JP4397801B2 - Manufacturing method of optical information recording medium - Google Patents

Description

The present invention relates to a recording information using an optical means such as a laser beam, a method of manufacturing the optical information recording medium body to be reproduced.

Conventional techniques for reproducing or recording high-density information using laser light are known. This prior art is mainly put to practical use as an optical disk.
Optical discs can be broadly classified into read-only, write-once, and rewritable types.
The read-only type is put into practical use as a compact disc or laser disc, and the write-once type or rewritable type is put into practical use as a disc for recording document files, data files, and the like. As the rewritable optical disk, a magneto-optical disk and a phase change optical disk are mainly known.

  The phase change type optical disk utilizes the fact that the recording layer reversibly changes state between an amorphous state and a crystal (or between a crystal and a crystal having a different structure) by laser light irradiation. More specifically, in a phase change optical disc, recording is performed by irradiating a laser beam and changing at least one of the refractive index and extinction coefficient of the thin film. Also, in the phase change optical disc, it is detected that the amplitude of the transmitted or reflected light of the laser beam irradiated to the recorded portion changes, and as a result, the transmitted or reflected light amount reaching the detection system changes. To play the signal.

  In general, in a phase change type optical disk, a case where the recording layer material is in a crystalline state is set as an unrecorded state, and the recording layer material is melted and rapidly cooled by irradiating a laser beam so that the recording layer material becomes in an amorphous state. Record state. Further, when erasing the signal, a laser beam power lower than that at the time of recording is irradiated to bring the recording layer into a crystalline state.

In general, a chalcogen compound is often used as the recording layer material. Since the recording layer made of the chalcogen compound is formed in an amorphous state, it is necessary to crystallize the entire recording area in an unrecorded state in advance. This entire crystallization is called “initialization”.
The initialization process is incorporated in a part of the disk manufacturing process, and the recording layer is made into a crystalline state using a laser beam or a flash light source. When laser light is used, the entire surface of the disk is initialized by irradiating the laser light while rotating the disk, focusing on the information layer, and shifting the position of the optical head in the radial direction of the disk.

  Initialization conditions such as laser power, linear velocity, defocus amount, and feed pitch of the laser light in this initialization are determined so as to satisfy the following criteria. That is, the initialization condition is generally that the entire area of the initialization area is uniformly crystallized without remaining an amorphous state, and the information is overwritten several times (several tens of times) from the first recording. In this case, the signal quality is required to be constant.

  When obtaining the initialization condition, the initialization condition is detected near the center of the disc (a predetermined position in the data area area where information is recorded / reproduced). Further, using the detected initialization condition, the entire disk including the burst cutting area described later is initialized. That is, initialization is performed over the entire surface under the same conditions.

  From the viewpoint of increasing the recording capacity of an optical disc per unit area, a single-sided dual-layer configuration and a manufacturing method thereof have been proposed, and a technique for changing initialization conditions in each layer is known (for example, patents). Reference 1). There is also a document describing a method of manufacturing a single-sided, dual-layer phase change optical disk using blue-violet laser light for a single-sided dual-layer disk (see, for example, Patent Document 2).

It is described in DVD-RAM and Blu-ray disc standards that a disc is provided with a burst cutting area (hereinafter referred to as BCA) for identifying each disc.
This BCA is performed, for example, by burning out the film using a high-power laser beam, or by providing an initialization portion and an uninitialization portion in a bar code shape in the radial direction in a normal initialization process (see FIG. 1). It is formed.

When the BCA is formed in the initialization process, the initialization unit and the uninitialized unit are provided by turning on and off the laser beam while keeping the relative angular velocity of the optical head of the laser beam for initialization and the disk constant.
Also, when reading BCA information, the disk is rotated and the laser beam is focused in the BCA area where the BCA is formed, and a portion with or without a film, or between an initialization portion and an uninitialization portion. BCA information is read from the difference in reflectance. Note that the standards for DVD-RAM and Blu-ray discs describe that BCA is provided on the innermost periphery of the layer on the back side when viewed from the laser light incident side.
Japanese Patent Application No.10-132982 Japanese Patent Application No. 2000-400442

  The applicant of the present application has developed a phase change type single-sided multilayer optical disk using blue-violet laser light. For example, as shown in FIG. 1, an optical disc having a first information layer, an optical separation layer, a second information layer, and a light transmission layer on a transparent substrate is being developed. In this optical disc, the BCA is formed in the first information layer in the initialization process.

According to the applicant's investigation, the following two problems have been confirmed in this initialization process.
The first problem is that when the first information layer and the second information layer are initialized one by one in this order, a BCA is provided in the first information layer. It will be initialized.

The second problem is the initialization process of the second information layer after the initialization of the first information layer, the focus is lost in the same radius area as the BCA area of the first information layer, and the initialization process stops. It is a thing that ends up.
A main object of the present invention is to provide a method for manufacturing an optical information recording medium having a single-sided multilayer structure that solves the above-mentioned problems.

An optical information recording medium according to an aspect of the present invention has information having a burst cutting area (hereinafter referred to as BCA) formed of a bar code-like portion having a different reflectance in a radial band shape on a disc-like substrate. A plurality of information layers including a layer (hereinafter referred to as a first information layer) and an information layer having no BCA (hereinafter referred to as a second information layer) are formed. A BCA is formed by providing an initialized portion and an uninitialized portion in a region of radius r1 to radius r2 (hereinafter referred to as a first region) of the first information layer. The information layer has at least a recording layer that causes a reversible change that can be detected optically between the amorphous phase and the crystalline phase when irradiated with laser light. The first information layer is a layer on the back side when viewed from the laser light incident side. The second information layer has a region having a radius r1 to a radius r2 (hereinafter referred to as a third region) and a region other than the third region (hereinafter referred to as a fourth region).

When the radial position of the initialization part of the third area adjacent to the fourth area is r3 and the radial position of the initialization part of the fourth area adjacent to the third area is r4, the radial position r3 of the second information layer is The difference in reflectance from the radial position r4 is 0.2% or more, and the reflectance at the radial position r3 is higher than the reflectance at the radial position r4.

The laser power of the initialization condition for initializing the third region may be higher than the laser power of the initialization condition for initializing the fourth region.
The linear velocity of the initialization condition for initializing the third region may be slower than the linear velocity of the initialization condition for initializing the fourth region.

The focal position of the initialization condition for initializing the third area may be closer to the second information layer than the focal position of the initialization condition for initializing the fourth area.
The feed pitch of the initialization condition for initializing the third region may be narrower than the feed pitch of the initialization condition for initializing the fourth region.
The distance between the radial position r3 and the radial position r4 may be 0.2 mm or less.

The radius position of the initialization portion of the first region adjacent to the region other than the first region of the first information layer (hereinafter referred to as the second region) is r3, and the radius of the initialization portion of the second region adjacent to the first region When the position is r4, the difference in reflectance between the radial position r3 and the radial position r4 of the first information layer is 0.2% or more, and the reflectance at the radial position r3 is greater than the reflectance at the radial position r4. It may be low.

The laser power of the initialization condition for initializing the first region may be lower than the laser power of the initialization condition for initializing the second region.
The linear velocity of the initialization condition for initializing the first region may be higher than the linear velocity of the initialization condition for initializing the second region.

The focal position of the initialization condition for initializing the first area may be farther from the first information layer than the focal position of the initialization condition for initializing the second area.
The distance between the radial position r3 and the radial position r4 may be 0.2 mm or less.

The reflectance of the first information layer in the amorphous state at the wavelength of the laser beam for crystallization is Ra1, the reflectance in the crystalline state is Rc1, the reflectance of the second information layer in the amorphous state is Ra2, and in the crystalline state When the reflectance of Rc2 is Rc2, Ra1> Ra2 and Rc1 <Rc2 may be satisfied.

The optical information recording medium may include a light transmission layer, a plurality of information layers, an optical separation layer formed between each of the plurality of information layers, and a substrate in order from the laser light incident side. .

  According to the present invention, it is possible to appropriately initialize the optical information recording medium, or to prevent the initialization process from being stopped midway, and the yield of manufacturing the optical information recording medium is improved.

(Summary of Invention)
<< Principle of initialization process >>
First, the principle of the initialization process for the first information layer and the second information layer will be described in detail with reference to FIG.

  As shown in FIG. 2, when the optical head that irradiates the initialization laser light is brought closer to the light transmission layer, focus errors from the light transmission layer, the second information layer, and the first information layer (see FIG. 1). Three signals are detected in sequence. The magnitudes of these three focus error signals are large when the reflectance of each information layer is high, and small when it is low.

The reflectance of each information layer varies depending on the combination of its thin film configuration and its phase state (amorphous or crystalline), and the probability of failure of the initialization process increases when the detected focus error signal is small.
In the configuration of the information layer used this time, the reflectance of the first information layer in the amorphous state at the wavelength of the laser light for crystallizing the first information layer and the second information layer is Ra1, and in the crystal state. Where Rc1 is the reflectance, Ra2 is the reflectance in the amorphous state of the second information layer, and Rc2 is the reflectance in the crystalline state, then Ra1> Ra2 and Rc1 <Rc2. Here, when the initialization laser light is irradiated when the first information layer and the second information layer are not initialized, since Ra1> Ra2, the first information layer is focused, The information layer can be initialized. Next, in the case of initializing the second information layer, Rc1 <Rc2 is established by creating a part (crystallized part) initialized as much as possible in the second information layer. Focusing can be performed to initialize the second information layer.

<About the cause of the issue>
According to the applicant's investigation, it is considered that the above problem occurs for the following reason.
First, the first problem, the reason why the second information layer is partially initialized when the first information layer is being initialized, is considered as follows.

  In the case of initializing the first information layer, the initialization laser light is also applied to the second information layer in a state where focusing is not performed. In the disc developed by the present applicant, the initialization laser power necessary for initializing the second information layer needs to be higher than the laser power necessary for initializing the first information layer. is there. For this reason, when the first information layer is initialized, the second information layer should not be initialized.

  However, the amount of energy required for crystallization (initialization) varies depending on the disk configuration. The disc adopted this time has a disc configuration in which the initialization sensitivity of the first information layer is poor and the initialization sensitivity of the second information layer is good. The multilayer films constituting each information layer have a film thickness distribution in the radial direction of the disk. Due to this film thickness distribution, the initialization sensitivity also changes in the radial direction of the disk. In the second information layer of the disc adopted this time, it is considered that the initialization sensitivity is further improved in the innermost circumference of the disc where the BCA is formed due to this film thickness distribution.

For this reason, when the initialization method similar to the conventional method is used, the second information layer is partially initialized when the first information layer is initialized.
Next, during initialization of the second information layer, which is the second problem, the focus is lost on the same radius area as the BCA area of the first information layer, and the reason why the initialization stops is as follows. I think so.

  In the disc adopted this time, in the same radius area as the BCA area where the uninitialized portion is provided, the difference between Ra1 and Rc2 of the first information layer and the second information layer is usually due to the film thickness distribution in the radial direction. It has a smaller configuration. For this reason, focusing becomes unstable when the laser light initializing the second information layer reaches the same radius region as that of the BCA.

For this reason, when the initialization method similar to the conventional method is used, the focus is lost on the BCA area of the first information layer while the second information layer is being initialized, and the initialization is stopped.
(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The technique described in the present embodiment solves the first problem described above, and the second information layer is partially initialized when the first information layer is initialized. Is to prevent.
《Disk structure》
The structure of the disk used in this embodiment will be described with reference to FIG. In FIG. 3, each laser beam for recording and reproducing information and initializing the information layer is incident from the light transmission layer 7 side. The substrate 1 is made of a resin plate such as polycarbonate or PMMA, a glass plate, or the like. The substrate surface 2 is covered with a spiral or concentric continuous groove or the like.

A first information layer 3 is provided on the substrate 1 (laser beam incident side). The first information layer 3 includes at least a reflective layer 8, protective layers 9 and 11, and a recording layer 10.
On the first information layer 3, an optical separation layer 4 is formed. The optical separation layer 4 is made of a material that is transparent with respect to the wavelength of the laser beam irradiated to record and reproduce signals on the first information layer 3, and optically separates the first information layer and the second information layer. It has a function to separate automatically. The optical separation layer 4 is formed by a method in which a layer made of an ultraviolet curable resin or the like is formed by spin coating, a method in which a transparent film is adhered by an adhesive tape or an ultraviolet curable resin, or the like. The surface 5 of the optical separation layer is covered with a spiral or concentric continuous groove or the like.

A second information layer 6 is formed on the optical separation layer 4. The second information layer 6 includes at least a reflective layer 12, protective layers 13 and 15, and a recording layer 14.
A light transmission layer 7 is formed on the second information layer 6. The light transmission layer 7 is formed by a method of forming a layer made of an ultraviolet curable resin or the like by spin coating, or a method of adhering a transparent film on the second information layer 6 with an adhesive tape or an ultraviolet curable resin or the like. .

  The protective layers 9, 11, 13, and 15 are made of oxides such as Al, Si, Ta, Mo, W, and Zr, sulfides such as ZnS, and nitriding such as Al, B, Ge, Si, Ti, and Zr. And materials mainly composed of fluorides such as Pb, Mg, and La can be used. In this embodiment, a ZnS-20 mol% SiO2 composition was used.

  As the material of the recording layers 10 and 14, a phase change material mainly composed of Te, In, Se, or the like can be used. Well-known main components of phase change materials include TeGeSb, TeGeSn, TeGeSnAu, SbSe, SbTe, SbSeTe, In-Te, In-Se, In-Se-Tl, InSbInSbSe, GeSbTeAg and the like. Examples of material systems that have been commercialized with phase change optical disks or that have been actively researched include GeSbTe systems and AgGeSbTe systems. These recording layers are usually formed in an amorphous state. When these recording layer materials are used, the transmittance in the crystalline state is smaller than the transmittance in the amorphous state at an infrared light wavelength generally used for initialization of the recording layer. In this embodiment, a GeSbTe-based recording layer material is mainly used.

  As the reflective layers 8 and 12, a material mainly containing a metal element such as Ag, Au, or Al can be used. Further, the same optical characteristics as those of the reflective layer can be obtained by laminating two or more kinds of protective layers having different refractive indexes instead of the metal reflective layer. In the present embodiment, a metal reflection layer containing Ag as a main component is used.

As a method for forming the protective layer, the recording layer, the reflective layer, and each layer, electron beam vapor deposition, sputtering, CVD, laser sputtering, and the like are usually applied. In this embodiment mode, a sputtering method is used.
<< Initialization process >>
Next, a process for initializing the optical information recording medium having the above-described single-sided two-layer structure using laser light will be described.

  The outline of the initialization apparatus will be described with reference to FIG. The laser light emitted from the laser light source is focused on the second information layer 6 or the first information layer 3 by the objective lens using, for example, an astigmatism method. At the time of focusing, focus error signals obtained from the first information layer 3 and the second information layer 6 are used. As a method for performing the focusing control, various methods such as a knife edge method can be employed.

Next, when initializing each formed information layer (the first information layer 3 and the second information layer 6), the first information layer 3 and the second information layer 6 are distinguished, A procedure for focusing the initialization laser beam on a desired information layer will be described.
First, when the optical head for irradiating the laser beam for initialization is brought closer to the light transmission layer, the focus error signals from the light transmission layer 7, the second information layer 6, and the first information layer 3 are sequentially 3 in order. Are detected (see FIG. 2). For example, in order to initialize the second information layer 6, the second focus error signal among the focus error signals detected when the optical head is brought close to the light transmission layer is focused. Alternatively, after the focus error signal from the first information layer 3 is detected, the optical head is moved away from the light transmission layer and the second focus error signal is focused in the initialization apparatus (note that In the case where there are a plurality of information layers instead of two, focussing is performed in the same manner.

As a method for initializing the first and second information layers 3 and 6, the following plurality of patterns can be considered.
(1) Immediately after each information layer is formed, each information layer is initialized.
(2) Each information layer is formed, and initialization is performed immediately after forming the optical separation layer 4 (light transmission layer 7 in the case of the second information layer 6) thereon.
(3) Initialization is performed after the first information layer 3, the optical separation layer 4, the second information layer 6, and the light transmission layer 7 are formed on the substrate 1 (note that the light transmission layer 7 is formed after the initialization). Sometimes).
(4) In the case of (3), the first information layer 3 is initialized before the second information layer 6 (or vice versa).

In addition, since crystallization (initialization) using laser light requires high output laser power, it is common to use an infrared laser having a wavelength of about 800 nm for the laser light wavelength.
In this embodiment mode, BCA is provided using an initialization process. The initialization area to be subjected to the initialization process is an area from the radius 21 mm to 59 mm of the disc, and the BCA is a portion not initialized in a radial band between the radius 21 mm and 22 mm of the disc (uninitialized). Are provided in a bar code form. Further, when forming the BCA (radius in the range of 21 to 22 mm), the disk was initialized in a state of rotating at a constant angular velocity (2728 rpm). In terms of the linear velocity, the radius is 6.0 m / s at a radius of 21 mm and 6.28 m / s at a radius of 22 mm.

The structure of the disk used in this embodiment will be described in more detail.
As an example of the disk structure, a polycarbonate having a diameter of 120 mm and a thickness of 1.1 mm, whose surface is covered with concave and convex guide grooves having a pitch of 0.3 μm and a groove depth of 20 nm, was adopted as the substrate 1. An Ag reflective layer, GeN, ZnS-20 mol% SiO2, Ge22Sb25Te53 (at%), and ZnS-20 mol% SiO2 were formed thereon in this order by the magnetron sputtering method, and the first information layer 3 was formed. Subsequently, a polycarbonate having a diameter of 120 mm and a thickness of 25 μm covered with concave and convex guide grooves having a pitch of 0.3 μm and a groove depth of 20 nm is formed of an ultraviolet curable resin, and the total is formed on the first information layer 3. An optical separation layer 4 having a thickness of 30 μm was formed. Subsequently, an Ag reflection layer, GeN, Ge22Sb25Te53 (at%), and ZnS-20 mol% SiO2 were formed on the optical separation layer 4 in this order by the magnetron sputtering method, and the second information layer 6 was formed. Subsequently, a light transmission layer 7 having a thickness of 0.1 mm was formed by spin coating.

The configuration of the disc used for the study, particularly the configuration of the information layer, is as follows.
The first information layer 3 has a structure in which an Ag reflection layer is formed on a substrate 1 by 100 nm, a GeN layer is formed by 5 nm, a ZnS-20 mol% SiO 2 layer is formed by 25 nm, a GeSbTe recording layer is formed by 15 nm, and a ZnS-20 mol% SiO 2 layer is formed by 60 nm. is there.

  In the second information layer 6, after forming the optical separation layer 4 on the first information layer 3, the Ag reflection layer is 10 nm, the GeN layer is 5 nm, the ZnS-20 mol% SiO 2 layer is 24 nm, and the GeSbTe recording layer is formed. The structure was such that a 6 nm ZnS—SiO 2 layer was formed to 50 nm. Further, a light transmission layer 7 was formed on the second information layer 6.

For initialization of each information layer, an initialization apparatus having a laser light source with a wavelength of 810 nm shown in FIG. 4 was used. Initialization conditions were determined in advance so that there was no deterioration in signal quality at the time of overwriting (conditions for no increase in jitter) at a disk radius of 40 mm.
In the first information layer 3, the obtained initialization condition (second initialization condition) is the defocus amount of laser light +3 μm (plus is the back side of the first information layer 3 when viewed from the laser incident side) Is a state where there is a just focus position, minus means a state where there is a just focus position on the near side), linear velocity 6 m / s, feed pitch 40 μm, laser power 1650 mW to 1750 mW (in this embodiment, 1700 mW) Implementation).

In the second information layer 6, the obtained initialization conditions (fourth initialization conditions) are defocus amount +3 μm, linear velocity 3 m / s, feed pitch 40 μm, laser power 870 to 930 mW (900 mW in this embodiment). Implemented).
The width of the laser beam for initialization in the disk radial direction was 100 μm.

Each information layer was initialized after the first information layer 3, the optical separation layer 4, the second information layer 6, and the light transmission layer 7 were formed.
When the first information layer 3 is initialized, the initialization laser power in the BCA region (first region: see FIG. 1) where the BCA is formed and the other initialization regions (second region: see FIG. 1), The results of examining the initialization stability when the linear velocity and defocus amount are changed will be described.

  In the present embodiment, the initialization conditions for initializing the BCA area (radius 21 to 22 mm) and the data area (radius 22 to 59 mm) of the first information layer 3 are changed (first initialization condition and Second initialization condition) At the end of initialization of the first information layer 3, observation with an optical microscope was performed to confirm the initialization state. At this time, it was confirmed whether or not the second information layer 6 was initialized by mistake.

  The results of changing the initialization laser power while keeping the “linear velocity 6 m / s” and “defocus amount +3 μm” constant (Table 1), “initialization laser power 1700 mW” The results of changing the linear velocity while keeping the “defocus amount +3 μm” constant (Table 2) are “initialization laser power 1700 mW” and “linear velocity 6 m / s”. Table 3 shows the results when “defocusing amount is changed” while keeping constant.

  Further, in each table, the reflectance at the radial position r3 = 21.9 mm and the radial position r4 = 22.1 mm of the first information layer 3 when the respective initialization conditions are used is shown (see FIG. 1). ). More specifically, the radial position r3 is a radial position in the BCA area (first area) and is a radial position close to the data area (second area). The radial position r4 is a radial position in the data area (second area) in the first information layer 3 and is a radial position close to the BCA area (first area). Further, the reflectance indicates the reflectance at the mirror portion of the reflected light having a wavelength of 405 nm from the radial position r3 and the radial position r4.

From Table 1, the following facts are confirmed.
When the initialization laser power in the BCA area is set to 1650 to 1750 mW or more which is the optimum power in the data area, a part of the second information layer 6 is erroneously initialized. If the initialization laser power in the BCA region is less than 1650 mW, which is the optimum power in the data area (that is, if the laser power density per unit area is reduced), the second information layer 6 is not initialized. Since the BCA only reads a signal based on the difference in reflectance between the initialized part and the uninitialized part, it only needs to be crystallized uniformly. For example, even if the BCA is formed at 1550 mW, the reflectance is not greatly affected. There is no problem because there is no. However, for example, when the initialization laser power is lowered to 1450 mW, initialization unevenness is formed in the BCA. Therefore, the initialization laser power is more than 1450 mW and less than 1650 mW, and more preferably, the initialization laser power is 1500 mW or more and 1600 mW or less. Initialization should be performed.

  Also, good results were obtained when the initialization laser power in the BCA region was -5.9% to -11.8% of the initialization laser power in the data area (when the laser power was lowered). . This range of values is a value obtained for the disk configuration and the configuration of the initialization device employed in the present embodiment, and the present invention is not effective only within this range. For example, the optimum range may vary depending on the configuration of the disk and the configuration of the initialization device.

(Table 2) confirms the following facts.
When the initialization linear velocity of the BCA area is lower than 6 m / s which is the linear velocity in the data area, a part of the second information layer 6 is erroneously initialized. On the other hand, when the initialization linear velocity is set to 6.5 m / s or more (that is, when the laser power density per unit area is small), the second information layer 6 is not initialized. However, if the initialization linear velocity is increased to 7.5 m / s, for example, initialization unevenness is formed in the BCA. Therefore, an initialization linear velocity of more than 6.0 m / s and less than 7.5 m / s is more preferable. Is preferably initialized at an initialization linear velocity of 6.5 m / s or more and 7.0 m / s or less.

  In addition, good results were obtained when the initialization linear velocity in the BCA region was set to + 8.3% to + 16.7% of the initialization linear velocity in the data area (when the linear velocity was increased). This range of values is a value obtained for the disk configuration and the configuration of the initialization device employed in the present embodiment, and the present invention is not effective only within this range. For example, the optimum range may vary depending on the configuration of the disk and the configuration of the initialization device.

(Table 3) confirms the following facts.
When the defocus amount at the time of initialization of the BCA area is set to just focus from +3 μm, which is the defocus amount in the data area, a part of the second information layer 6 is erroneously initialized. However, when the focus is further defocused, the second information layer 6 is not initialized. For this reason, initialization should be performed with a defocus amount exceeding +3 μm, more preferably with a defocus amount of +3.5 μm or more.

  Also, good results were obtained when the defocus amount in the BCA area was set to + 16.7% or more of the defocus amount in the data area (when the defocus amount was increased). This range of values is a value obtained for the disk configuration and the configuration of the initialization device employed in the present embodiment, and the present invention is not effective only within this range. For example, the optimum range may vary depending on the configuration of the disk and the configuration of the initialization device.

  As described above, when different initialization conditions are used for the BCA region and the data area, more specifically, the laser power, the linear velocity, and the defocus amount are adjusted in the BCA region, and the laser power density per unit area is set. It can be seen that when the initialization condition lower than the initialization condition in the data area is used, the second information layer 6 is not erroneously initialized.

  Further, from (Tables 1 to 3), the difference in reflectance of the initialization portion between the radius of 21.9 mm (radius position in the BCA region) and the radius of 22.1 mm (radius position in the data area) is 0.2%. When the reflectance is lower at the radius of 21.9 mm, the second information layer 6 is not initialized. Note that the difference in reflectance occurs even when the laser power density per unit area is too low, but in this case, initialization is originally not uniform and an initialization process error occurs.

  Here, it is considered that there is almost no difference in reflectance due to the film thickness distribution of each layer when the radial direction is about 0.2 mm. For this reason, the difference in disk reflectivity in (Tables 1 to 3) is considered to be a difference due to different initialization conditions. For example, when the laser power density per unit area is high, the degree of initialization proceeds and the reflectance increases. However, when the laser power density becomes higher than a certain level, the reflectance is saturated. Therefore, when there is a reflectance difference of 0.2% or more within a radius of 0.2 mm, it can be determined that the reflectance difference is caused by a difference in initialization conditions.

  In the present embodiment, the laser power, the linear velocity, and the defocus amount are individually changed to change the laser power density per unit area. On the other hand, similar results can be obtained when the laser power density is changed by combining these parameters.

In this embodiment, the initialization is performed from the inner periphery toward the outer periphery. On the other hand, similar results can be obtained when initialization is performed from the outer periphery toward the inner periphery.
(Embodiment 2)
The technique described in this embodiment solves the second problem described above, and prevents the focus from being lost during initialization of the second information layer and the initialization from being stopped.

  When the second information layer 6 is initialized, the first information layer 3 has the same radius as the BCA area (first area: see FIG. 1) (third area: see FIG. 1), Initialization when initialization power, linear velocity, and defocus amount are changed in the data area (second area: see FIG. 1) and the same radius area (fourth area: see FIG. 1) in the information layer 3 The results of studying stability will be described. Since the disk configuration, initialization device, and the like used in the present embodiment are the same as those in the first embodiment, detailed description thereof is omitted.

In the first information layer 3, BCA is provided in advance in the BCA region having a radius of 21 to 22 mm by an initialization process, and further, initialization is performed in a data area having a radius of 22 to 59 mm.
In the present embodiment, the area of the second information layer 6 having a radius of 21 to 59 mm is subsequently initialized. At that time, in a region having a radius of 21 to 22 mm which is the same radius as the BCA region of the first information layer 3, an appropriate initialization condition (fourth initialization condition) obtained in advance for the region having a radius of 22 to 59 mm. Initialization was performed using the initialization condition (third initialization condition) in which the angle was changed, and initialization was performed in an appropriate initialization condition obtained in advance in a region having a radius of 22 to 59 mm. At this time, it was confirmed whether the initialization process of the second information layer 6 was performed to the end without stopping.

Here, as described in the first embodiment, the proper initialization conditions obtained in the data area of the second information layer 6 are defocus amount +3 μm, linear velocity 3 m / s, feed pitch 40 μm, laser power It was 870 to 930 mW (implemented at 900 mW in this embodiment).
In the initialization of the area of the second information layer 6 having a radius of 21 to 22 mm, “initialization laser power was changed” while “linear velocity was 3 m / s” and “defocus amount was +3 m”. (Table 4) shows the results of the case, and (Table 5) shows the results when the "linear velocity is changed" after making the "initialization laser power 900 mW" and the "defocus amount +3 μm" constant. Table 6 shows the results when the “initialization laser power is 900 mW” and the “linear velocity is 3 m / s” and the “defocus amount is changed”.

  Further, in each table, the reflectivity at the radial position r3 = 21.9 mm and the radial position r4 = 22.1 mm of the second information layer 6 when the respective initialization conditions are used (see FIG. 1). ). More specifically, the radius position r3 is a radius position in a radius area (third area) corresponding to the BCA area (first area) in the second information layer 6, and the data area (fourth area). Is a radial position close to. The radius position r4 is a radius position in the data area (fourth area) in the second information layer 6 and is a radius close to the area (third area) having a radius corresponding to the BCA area (first area). Position. Further, the reflectance indicates the reflectance at the mirror portion of the reflected light having a wavelength of 405 nm from the radial position r3 and the radial position r4.

(Table 4) confirms the following facts.
If the initialization process of the area of radius 21 to 22 mm of the second information layer 6 is performed at an appropriate laser power of 870 to 930 mW or less in the data area, the focus is lost in the middle of the area of radius 21 to 22 mm. The initialization process stops. Therefore, by raising the laser power above the appropriate laser power, the focus is not lost during the process, and the initialization yield is improved without stopping the initialization process. For example, the initialization process may be performed with a laser power exceeding 930 mW, more preferably with a laser power of 960 mW or more.

  In addition, good results were obtained when the initialization laser power in the region corresponding to the BCA region was set to + 6.7% or more of the initialization laser power in the data area (when the laser power was increased). This range of values is a value obtained for the disk configuration and the configuration of the initialization device employed in the present embodiment, and the present invention is not effective only within this range. For example, the optimum range may vary depending on the configuration of the disk and the configuration of the initialization device.

(Table 5) confirms the following facts.
When the initialization process of the area of radius 21 to 22 mm of the second information layer 6 is performed at 3.0 m / s or more which is the appropriate linear velocity in the data area, the focus is lost in the middle of the area of radius 21 to 22 mm. As a result, the initialization process stops. Therefore, by making the linear velocity slower than the appropriate linear velocity, the focus is not lost during the process, and the initialization yield is improved without stopping the initialization process. For example, the initialization process may be performed at a linear velocity of less than 3.0 m / s, more preferably at a linear velocity of 2.7 m / s or less.

  Also, good results were obtained when the linear velocity of the region corresponding to the BCA region was less than −10% of the linear velocity in the data area (when the linear velocity was further lowered). This range of values is a value obtained for the disk configuration and the configuration of the initialization device employed in the present embodiment, and the present invention is not effective only within this range. For example, the optimum range may vary depending on the configuration of the disk and the configuration of the initialization device.

(Table 6) confirms the following facts.
If the initialization process of the area of radius 21 to 22 mm of the second information layer 6 is further defocused from +3 μm, which is an appropriate defocus amount in the data area, the focus is lost in the middle of the area of radius 21 to 22 mm. The initialization process stops. Therefore, by making the focus more precise, the focus is not lost during the process, and the initialization yield is improved without stopping the initialization process. For example, the initialization process may be performed at a focal position of less than +3 μm, more preferably at a focal position of +2.5 μm or less.

  Also, good results were obtained when the defocus amount of the region corresponding to the BCA region was less than −16.7% of the defocus amount in the data area (when the defocus amount was further lowered). This range of values is a value obtained for the disk configuration and the configuration of the initialization device employed in the present embodiment, and the present invention is not effective only within this range. For example, the optimum range may vary depending on the configuration of the disk and the configuration of the initialization device.

  As described above, the area of the second information layer 6 having a radius of 21 to 22 mm (area having the same radius as the BCA area) and the area having a radius of 22 to 59 mm (area having the same radius as the data area of the first information layer) More specifically, the laser power, the linear velocity, and the defocus amount are adjusted in the region having the radius of 21 to 22 mm, and the laser power density per unit area is set to the initial value of the region having the radius of 22 to 59 mm. It can be seen that when the initial condition higher than the initialization condition is used, the focus is not shifted in the middle, and the yield in the initialization process is improved.

Here, the reason why the focus is not shifted in the middle is considered as follows.
The initialization process is performed by shifting the laser beam little by little in the radial direction every round (so as to overlap each other little by little). In this embodiment, since the feed pitch is 40 μm with respect to the beam diameter of 100 μm, 60 μm out of 100 μm crystallized in the first round is irradiated with the initialization laser light in the next round. Become. Conventionally, it is considered that the focus of the second information layer 6 in the region having the same radius as that of the BCA region is lost because the reflectance of the uninitialized portion of the BCA region is high. On the other hand, as in this embodiment, by increasing the laser power density per unit area, the region initialized in the radial direction is expanded, the reflected light from the uninitialized portion of the BCA region is reduced, and the focus is increased. It is thought that it is hard to come off.

  Further, from (Tables 4 to 6), the difference in the reflectance of the initialization unit at the radius of 21.9 mm (radius position in the area having the same radius as the BCA area) and the radius of 22.1 mm (radius position in the data area). Is 0.2% or more and the reflectance at the radius of 21.9 mm is higher, the initialization of the second information layer 6 does not stop at the radius of 21 to 22 mm.

  Here, it is considered that there is almost no difference in reflectance due to the film thickness distribution of each layer when the radial direction is about 0.2 mm. For this reason, the difference in disk reflectivity in (Tables 4 to 6) is considered to be a difference due to different initialization conditions. For example, when the laser power density per unit area is high, the degree of initialization proceeds and the reflectance increases. However, when the laser power density becomes higher than a certain level, the reflectance is saturated. Therefore, when there is a reflectance difference of 0.2% or more within a radius of 0.2 mm, it can be determined that the reflectance difference is caused by a difference in initialization conditions.

  In the present embodiment, the laser power, the linear velocity, and the defocus amount are individually changed to change the laser power density per unit area. On the other hand, similar results can be obtained when the laser power density is changed by combining these parameters.

In this embodiment, the initialization is performed from the inner periphery toward the outer periphery. On the other hand, similar results can be obtained when initialization is performed from the outer periphery toward the inner periphery.
(Embodiment 3)
The technique described in this embodiment solves the second problem described above, and prevents the focus from being lost during initialization of the second information layer and the initialization from being stopped.

  When the second information layer 6 is initialized, the first information layer 3 has the same radius as the BCA area (first area: see FIG. 1) (third area: see FIG. 1), Initialization stability when the feed pitch of the initialization laser beam is changed between the data area (second area: see FIG. 1) and the same radius area (fourth area: see FIG. 1) in the information layer 3 Describe the results of the study. Since the disk configuration, initialization device, and the like used in the present embodiment are the same as those in the first embodiment, detailed description thereof is omitted.

In the first information layer 3, BCA is provided in advance in the BCA region having a radius of 21 to 22 mm by an initialization process, and further, initialization is performed in a data area having a radius of 22 to 59 mm.
In the present embodiment, the area of the radius 21 to 59 mm of the second information layer 6 is subsequently initialized. At that time, in a region having a radius of 21 to 22 mm which is the same radius as the BCA region of the first information layer 3, a feed pitch obtained by changing an appropriate feed pitch obtained in advance with respect to a region having a radius of 22 to 59 mm is used. Initialization was performed, and initialization was performed using an appropriate feed pitch obtained in advance in an area having a radius of 22 to 59 mm. At this time, it was confirmed whether the initialization process of the second information layer 6 was performed to the end without stopping.

Here, as described in the first embodiment, the proper initialization conditions obtained in the data area of the second information layer 6 are defocus amount +3 μm, linear velocity 3 m / s, feed pitch 40 μm, laser power It was 870 to 930 mW (implemented at 900 mW in this embodiment).
In the initialization of the second information layer 6 having a radius of 21 to 22 mm, “linear velocity is 3 m / s”, “defocus amount is +3 μm”, “initialization laser power is 900 mW”, and “feed pitch is changed” "Table 7" shows the results.

  Further, (Table 7) shows the reflectivity at the radial position r3 = 21.9 mm and the radial position r4 = 22.1 mm of the second information layer 6 when the respective initialization conditions are used. More specifically, the radius position r3 is a radius position in a radius area (third area) corresponding to the BCA area (first area) in the second information layer 6, and the data area (fourth area). Is a radial position close to. The radius position r4 is a radius position in the data area (fourth area) in the second information layer 6 and is a radius close to the area (third area) having a radius corresponding to the BCA area (first area). Position. Further, the reflectance indicates the reflectance at the mirror portion of the reflected light having a wavelength of 405 nm from the radial position r3 and the radial position r4.

(Table 7) confirms the following facts.
When the initialization process of the area of radius 21 to 22 mm of the second information layer 6 is performed at a feed pitch of 40 μm or more which is an appropriate feed pitch in the data area, the focus is lost in the middle of the area of radius 21 to 22 mm. As a result, the initialization process stops. Therefore, by making the feed pitch narrower than the proper feed pitch in the data area, the focus is not lost midway, and the initialization yield is improved without stopping the initialization process. For example, the initialization process may be performed with a feed pitch of less than 40 μm, more preferably with a feed pitch of 30 μm or less.

Here, as described in the second embodiment, the reason why the focus is not shifted in the middle is that the reflected light from the uninitialized portion of the BCA area is reduced by narrowing the feed pitch, and the focus is not easily lost. It is thought that there is.
Also, good results were obtained when the feed pitch of the region corresponding to the BCA region was less than -25% of the feed pitch of the initialization laser beam in the data area (when the feed pitch was made narrower). This range of values is a value obtained for the disk configuration and the configuration of the initialization device employed in the present embodiment, and the present invention is not effective only within this range. For example, the optimum range may vary depending on the configuration of the disk and the configuration of the initialization device.

  Further, from (Table 7), the difference in reflectivity of the initialization unit between the radius of 21.9 mm (radius position in the area having the same radius as the BCA area) and the radius of 22.1 mm (radius position in the data area) is 0. When the radius is 2% or more and the radius of 21.9 mm is higher, the initialization of the second information layer 6 does not stop at the radius of 21 to 22 mm.

  Here, it is considered that there is almost no difference in reflectance due to the film thickness distribution of each layer when the radial direction is about 0.2 mm. For this reason, the difference in disk reflectivity in (Table 7) is considered to be a difference due to different initialization conditions. For example, if the feed pitch is narrow, the laser power is applied again to the part that has been initialized once (crystallized part), and the degree of initialization is further advanced. For this reason, the reflectance is increased. When there is a reflectance difference of 0.2% or more within a radius of 0.2 mm, it can be determined that the reflectance difference is caused by a difference in initialization conditions.

In this embodiment, the initialization is performed from the inner periphery toward the outer periphery. On the other hand, similar results can be obtained when initialization is performed from the outer periphery toward the inner periphery.
Further, when the disc used in the present embodiment was observed with an optical microscope, the pitch of the striped pattern due to the difference in the initialization state looked different depending on the feed pitch as the initialization condition. This stripe pattern is caused by the difference in the degree of initialization due to the overlapping of the initialization laser beams. Thus, the difference in feed pitch can be observed with an optical microscope as a difference in stripe pattern.
(Modification of Embodiments 1 to 3)
The techniques described in the first embodiment, the second embodiment, and the third embodiment may be used independently or may be used in combination. More specifically, the first information layer 3 is initialized by the technique described in the first embodiment, and the second information layer 6 is initialized by the technique described in the second and third embodiments. May be.

  In the above embodiment, the initialization of a disc having two information layers has been described. However, the present invention can also be applied to initialization of a disc having a plurality of information layers.

The method for manufacturing an optical information recording medium of the present invention, as an initialization process of single-sided multilayer optical disk, is useful in view of its productivity improvement.

Structure diagram of an optical disk used in an embodiment of the present invention Diagram of focus error signal for initialization of optical disc used in the embodiment of the present invention Structure diagram of an optical disk used in an embodiment of the present invention Structure diagram of optical disk initialization apparatus used in the embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate surface 3 First information layer 4 Optical separation layer 5 Optical separation layer surface 6 Second information layer 7 Light transmission layer 8 Reflection layer 9 Protection layer 10 Recording layer 11 Protection layer 12 Reflection layer 13 Protection layer 14 Recording layer 15 Protective layer

Claims (10)

An information layer (hereinafter referred to as a “first information layer”) having a burst cutting area (hereinafter referred to as “BCA”) having a bar code-like portion having a different reflectance in a radial band shape on a disk-shaped substrate, and the BCA An optical information recording medium in which a plurality of information layers including an information layer not included (hereinafter referred to as a second information layer) is formed,
The BCA is formed by providing an initialized portion and an uninitialized portion in a region of radius r1 to radius r2 (hereinafter referred to as a first region) of the first information layer,
The information layer has at least a recording layer that causes a reversible change optically detectable between an amorphous phase and a crystalline phase by laser light irradiation,
The first information layer is a layer on the back side when viewed from the laser light incident side,
The second information layer has a region having a radius r1 to a radius r2 (hereinafter referred to as a third region) and a region other than the third region (hereinafter referred to as a fourth region).
The focal position of the initialization condition for initializing the third area is a position closer to the second information layer than the focal position of the initialization condition for initializing the fourth area,
When the radial position of the initialization portion of the third region adjacent to the fourth region is r3, and the radial position of the initialization portion of the fourth region adjacent to the third region is r4,
The distance between the radial position r3 and the radial position r4 is 0.2 mm or less,
The difference in reflectance at the radial position r3 and radius position r4 Metropolitan of the second information layer is not less than 0.2%, and the reflectivity at the radial position r3 is greater than the reflectance at the radial position r4, optical Method for manufacturing an information recording medium. An information layer (hereinafter referred to as a “first information layer”) having a burst cutting area (hereinafter referred to as “BCA”) having a bar code-like portion having a different reflectance in a radial band shape on a disk-shaped substrate, and the BCA An optical information recording medium in which a plurality of information layers including an information layer not included (hereinafter referred to as a second information layer) is formed,
The BCA is formed by providing an initialized portion and an uninitialized portion in a region of radius r1 to radius r2 (hereinafter referred to as a first region) of the first information layer,
The information layer has at least a recording layer that causes a reversible change optically detectable between an amorphous phase and a crystalline phase by laser light irradiation,
The first information layer is a layer on the back side when viewed from the laser light incident side,
The second information layer has a region having a radius r1 to a radius r2 (hereinafter referred to as a third region) and a region other than the third region (hereinafter referred to as a fourth region).
The feed pitch of the initialization condition for initializing the third region is made narrower than the feed pitch of the initialization condition for initializing the fourth region,
When the radial position of the initialization portion of the third region adjacent to the fourth region is r3, and the radial position of the initialization portion of the fourth region adjacent to the third region is r4,
The distance between the radial position r3 and the radial position r4 is 0.2 mm or less,
The difference in reflectance at the radial position r3 and radius position r4 Metropolitan of the second information layer is not less than 0.2%, and the reflectivity at the radial position r3 is greater than the reflectance at the radial position r4, optical Method for manufacturing an information recording medium. The laser power of the third initialization condition for initializing the region is higher than the laser power of the initialization condition for initializing the fourth area, the manufacturing method of the optical information recording medium according to claim 1 or 2. The linear speed of the third initialization condition for initializing the region is slower than the linear speed of the initialization condition for initializing the fourth area, the manufacturing method of the optical information recording medium according to claim 1 or 2. The radius position of the initialization portion of the first region adjacent to the region other than the first region (hereinafter referred to as the second region) of the first information layer is r3, and the radius position of the second region adjacent to the first region is When the radial position of the initialization portion is r4, the difference in reflectance between the radial position r3 and the radial position r4 of the first information layer is 0.2% or more, and the reflectance at the radial position r3 is The method for manufacturing an optical information recording medium according to claim 1, wherein the optical information recording medium is lower than the reflectance at the radial position r < b > 4. 6. The method of manufacturing an optical information recording medium according to claim 5 , wherein a laser power under an initialization condition for initializing the first area is lower than a laser power under an initialization condition for initializing the second area. 6. The method of manufacturing an optical information recording medium according to claim 5 , wherein a linear velocity of an initialization condition for initializing the first area is higher than a linear velocity of an initialization condition for initializing the second area. 6. The optical position according to claim 5 , wherein a focal position of an initialization condition for initializing the first area is farther from the first information layer than a focal position of an initialization condition for initializing the second area. A method for manufacturing an information recording medium. The reflectance of the first information layer in the amorphous state at the wavelength of the laser light for crystallization is Ra1, the reflectance in the crystalline state is Rc1, the reflectance of the second information layer in the amorphous state is Ra2, and the crystal 3. The method of manufacturing an optical information recording medium according to claim 1, wherein Ra1> Ra2 and Rc1 <Rc2 when the reflectance in the state is Rc2. In order from the laser beam incidence side, a light transmission layer, wherein a plurality of information layers, and the optical separation layer formed between each of said plurality of information layers, and a said substrate, to claim 1 or 2 The manufacturing method of the optical information recording medium of description.

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