JP2004005865A - Optical information recording medium, method for manufacturing the same, and initializer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an initialization method and initializer for an optical information recording medium capable of rapidly initializing the multilayered recording medium having a plurality of recording layers. <P>SOLUTION: The optical information recording medium (1) which has a plurality of recording layers (3 and 5) and is smaller in the reflectivity in an uninitialized state for an initializing light beam of at least one recording recording layer among a plurality of the recording layers (3 and 5) than the reflectivity after the initialization is formed by first irradiating the recording layer (5) on the deeper side viewed from the side irradiated with the light beam and irradiating the recording layer (3) on the near side afterward to simultaneously initialize the recording layers, by which the optical recording medium (1) absent of the initialization unevenness in the initialized recording layers (3 and 5) is obtained. This initialization method comprises irradiating first the recording layer (5) on the deeper side viewed from the side irradiated with the light beam among a plurality of the recording layers with the light beam in the positions of the same distance viewed from the radial direction on the optical recording medium. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical information recording medium having a plurality of recording layers for recording and reproducing information by irradiating a laser beam or the like, a method of manufacturing the same, and an initialization apparatus.
[0002]
[Prior art]
Optical information recording media have attracted attention as large-capacity and high-density memories. Currently, development of a rewritable type called an erasable type is underway. As one of such erasable optical information recording media, there is a type that uses a thin film that changes phase between an amorphous state and a crystalline state as a recording layer, and performs recording and erasing of information by thermal energy by laser light irradiation.
[0003]
As a phase change material for the recording layer, an alloy film containing Ge, Sb, Te, In, or the like as a main component, for example, a GeSbTe alloy is known. Recording of information is performed by forming a recording mark by partially amorphizing the recording layer. Usually, information is often erased by crystallizing the recording mark. Amorphization is performed by heating the recording layer above its melting point and then cooling it. On the other hand, crystallization is performed by heating the recording layer to a temperature higher than the crystallization temperature and lower than the melting point. In general, the recording layer is formed by sputtering, but the thin film of the phase change material formed by sputtering is almost in an amorphous state. Therefore, it is necessary to make the recording layer in a crystalline state before recording information. This process is called initialization.
[0004]
A conventional initialization apparatus for performing the initialization has one optical head having one light source and one objective lens, and irradiates the optical layer with a light beam from the optical head to a recording layer of a recording medium. The head is moved in a predetermined direction to initialize a desired area of the recording layer.
[0005]
On the other hand, recently, as the processing capacity of various information devices is improved, the amount of information handled is increasing. For this purpose, a recording medium capable of recording and reproducing data at a higher capacity and at a higher speed is required. As means for increasing the capacity and increasing the speed, a multilayer recording medium having a plurality of recording layers and capable of recording and reproducing information on each recording layer from one side has been proposed (for example, JP-A-9-91700). Publication).
[0006]
[Problems to be solved by the invention]
However, the initialization method disclosed in Japanese Patent Application Laid-Open No. 9-91700 has a problem that the recording layer is likely to be uneven because the recording layer on the near side as viewed from the beam irradiation side is initialized first. That is, when initialized, light is difficult to transmit due to crystallization, and there is a problem that the initialization of the recording layer on the back side cannot be uniform.
[0007]
When the multilayer recording medium is initialized using a conventional initialization device, the number of recording layers that can be initialized at a time is only one, so it is necessary to repeat the initialization operation by the number of recording layers. In addition, there is a problem that the time required for the initialization becomes extremely long. In addition, while a short wavelength light beam is used to increase the recording density for recording and reproduction of a recording medium, a long wavelength light beam is used to increase the light intensity for initializing the recording medium. Can be Therefore, initialization is performed with a light beam having a wavelength different from the optical design wavelength of the recording medium, and the focus servo that accurately adjusts the focal position to the recording layer becomes unstable. There is a problem that the performance of the recording medium is reduced. In particular, in the case of a multilayer recording medium, it is necessary to accurately adjust the focal position to a specific recording layer among a plurality of recording layers, and the above problem becomes conspicuous.
[0008]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a method of manufacturing an optical information recording medium and a method of initializing a multi-layer recording medium having a plurality of recording layers, in which focus servo is stable and which can be initialized in a short time. It is an object of the present invention to provide a high-performance multi-layer recording medium in which a recording layer is provided, and the recording layer has no initialization unevenness.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an optical information recording medium of the present invention has a plurality of recording layers, and reflects at least one of the plurality of recording layers in an uninitialized state with respect to an initialization light beam. An optical information recording medium whose reflectance is smaller than the reflectance after the initialization, wherein a light beam is first radiated to a recording layer deeper in the plurality of recording layers when viewed from the light beam irradiation side, The recording layer on the side is initialized by irradiating a light beam later.
[0010]
Another optical information recording medium according to the present invention has a plurality of recording layers, and a reflectance of at least one of the plurality of recording layers in an uninitialized state with respect to an initialization light beam after the initialization. The optical information recording medium having a reflectivity smaller than that of the optical recording medium, characterized in that the initialized recording layer has no initialization unevenness.
[0011]
Next, the manufacturing method of the present invention, when initializing the optical information recording medium having a plurality of recording layers, irradiates each of the plurality of recording layers with a different light beam, from the radial direction on the optical information recording medium At a position at the same distance as viewed, the light beam is first applied to the recording layer on the far side when viewed from the light beam irradiation side of the plurality of recording layers, and the light beam is applied to the recording layer on the near side later. And irradiating the plurality of recording layers with different positions by a light beam irradiation operation and simultaneously initializing the recording layers.
[0012]
Next, another manufacturing method of the present invention is a method for manufacturing an optical information recording medium having a plurality of recording layers, wherein the crystallization light for crystallizing the recording layers when initializing at least one recording layer. An initialization method for controlling a focal position of the crystallization light beam using a focal position control light beam different from the beam is included.
[0013]
Next, the initialization device of the present invention is an initialization device for an optical information recording medium having a plurality of recording layers, provided on the same surface side with respect to the recording medium, and applying a light beam to the recording layers different from each other. A plurality of optical heads for irradiating, and a moving unit for moving the optical head in a predetermined direction, wherein the recording on the deeper side of the plurality of optical heads when viewed from the light beam irradiation side of the plurality of recording layers. An optical head for irradiating the layer with a light beam is further disposed on the initialization progressing side.
[0014]
Next, another initialization apparatus of the present invention includes at least one optical head and moving means for moving the optical head in a predetermined direction, wherein at least one of the optical heads includes a single objective lens. A light source for irradiating a crystallization light beam for crystallizing the recording layer and a light source for irradiating a focal position control light beam with an intensity that does not crystallize the recording layer are provided.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
In the optical information recording medium of the present invention, the reflectance of the at least one of the plurality of recording layers in the uninitialized state with respect to the initialization light beam is smaller than the reflectance after the initialization. Even a later recording medium can be determined. This is because a portion of the normal recording medium that is not initialized remains in the inner peripheral area and / or the outer peripheral area even after the initialization.
[0016]
The non-uniformity of initialization in the recording layer can be determined by measuring the jitter (JIT) value of the reproduced signal when the information is overwritten several times, or by checking whether the recorded information can be normally reproduced. Can be determined.
[0017]
The reflectance of at least one of the plurality of recording layers in an uninitialized state with respect to the initialization light beam is equal to or less than の of the reflectance after initialization, that is, the reflectance after initialization. Can be twice or more the reflectance in an uninitialized state.
[0018]
It is preferable that the recording layer on the back side and the recording layer on the front side are initialized at the same time by changing the positions by a single light beam irradiation operation. This is for shortening the initialization time.
[0019]
Next, in the manufacturing method of the present invention, the positions of the plurality of recording layers are changed by a light beam irradiation operation and are simultaneously initialized from the back side recording layer, so that there is no initialization unevenness, and the initialization time is reduced. Can be shortened and initialized. In other words, the initialization can initialize the multilayer recording medium in a short time and initialize the recording layer farther from the light beam irradiation side without being affected by the initialization of the recording layer closer to the front side. Method.
[0020]
The light beam is provided on an optical head, and while moving a plurality of optical heads provided on the same surface side with respect to the recording medium in a predetermined direction, using an optical head arranged on a more initialization progress direction side. Then, of the plurality of recording layers, the recording layer on the deeper side as viewed from the light beam irradiation side may be irradiated with a light beam to initialize the plurality of recording layers simultaneously.
[0021]
Further, among the plurality of optical heads, spot shapes of light beams emitted from at least two optical heads may be different from each other.
[0022]
Further, when the at least one recording layer is initialized, the focal position of the crystallization light beam is controlled by using a focus position control light beam different from the crystallization light beam for crystallizing the recording layer. Is also good. In this manner, a stable initialization method of the focus servo is provided, and the position of the recording film can be accurately detected.
[0023]
Further, when the at least one recording layer is initialized, at the start of the initialization, the focal position of the optical head is moved up and down with a light beam intensity sufficient for the initialization to partially crystallize the recording layer. You may. When partially crystallized, the reflectance of the crystallized portion increases, so that the position of the recording film can be accurately detected. As a result, even if the recording medium has a very low reflectance in the amorphous state of the recording layer, a stable initialization method of the focus servo can be achieved.
[0024]
When initializing the at least one recording layer, at the beginning of the initialization, after focusing on a recording layer that provides a larger amount of reflected light than the recording layer, the focal position of the optical head is changed to the thickness of the recording medium. Alternatively, the target recording layer may be initialized by moving in a predetermined direction in a predetermined direction. This method can also accurately detect the position of the recording film.
[0025]
After focusing on a recording layer that provides a larger amount of reflected light than the recording layer with the intensity of the light beam that does not crystallize the target recording layer, the focal position of the optical head is set in advance in the thickness direction of the recording medium. The target recording layer may be partially crystallized by moving the recording layer up and down around a position separated by a predetermined distance. This method can also accurately detect the position of the recording film.
[0026]
After focusing on a recording layer that provides a larger amount of reflected light than the recording layer with the intensity of a light beam that does not crystallize the target recording layer, the focal position of the optical head is shifted by a predetermined distance to the recording medium. May be moved in the thickness direction to initialize the target recording layer with a light beam having sufficient intensity for initializing the target recording layer. This method can also accurately detect the position of the recording film.
[0027]
The spot width of the light beam for initializing the recording layer on the near side as viewed from the light beam irradiation side is x, the spot width and the incident angle of the light beam for initializing the recording layer on the back side are y and θ, and the light beams are Is the distance of z and the distance between the recording layers is d,
z> (x / 2) + (y / 2) + (d · tan θ)
It is preferable to set the positional relationship between the optical heads so as to satisfy the following relationship. By doing so, even if a plurality of recording layers are initialized at the same time, each recording layer is initialized independently and is not affected by the initialization processing of other layers, so that it is possible to prevent the occurrence of uneven initialization.
[0028]
Next, according to the initialization apparatus of the present invention, the multi-layer recording medium is initialized in a short time, and the initialization of the recording layer on the far side as viewed from the light beam irradiation side is initialized on the near side. This is an initialization device that can be performed without the influence of the above. In this apparatus, a spindle motor for rotating a recording medium, a plurality of optical heads for irradiating light beams to different recording layers of the recording medium, a transfer table for installing the optical head, and moving the transfer table to a desired position It is preferable that a moving means for moving the plurality of optical heads is provided, and the plurality of optical heads are arranged such that light beams emitted from the respective optical heads have different radial positions on the recording medium.
[0029]
Further, the plurality of optical heads may be installed on the same transfer table. In this way, the device can be simplified and downsized.
[0030]
Further, the thicknesses of the optimum substrates that minimize the spot diameter of the light irradiated from the plurality of optical heads to the recording medium through the substrate may be different from each other. This makes it possible for each optical head to accurately focus a light beam on a target recording layer, thereby enabling stable and stable initialization.
[0031]
In addition, at least one of the plurality of optical heads includes a driving unit that moves an objective lens provided in the optical head up and down, a counter that counts the number of up and down movements of the objective lens, and the optical head. A controller for controlling the intensity of the light beam emitted from the light source and the driving unit, and a moving unit for moving the optical head in a predetermined direction. Thus, at the start of initialization, the recording layer is partially crystallized by raising and lowering the focal position of the optical head with a light beam intensity sufficient for initialization, thereby increasing the reflectance of the recording layer in the amorphous state. Can be a stable initialization device for the focus servo even if the recording medium is very small.
[0032]
A plurality of optical heads that are provided on the same surface side with respect to the recording medium and irradiate the recording layers different from each other with a light beam; and among the plurality of optical heads, a light beam irradiation side of the plurality of recording layers. An optical head that irradiates a light beam to the recording layer on the deeper side as viewed from above may be disposed on the initialization progressing side.
[0033]
The optical head may include an objective lens and a plurality of light sources, and may include an optical path correcting unit on a unique optical path of a light beam emitted from at least one light source. Thus, while the focus of the light beam emitted from one light source is adjusted to the specific recording layer by moving the objective lens, the focus of the light beam emitted from the other light source is focused on another recording layer by the optical path correcting unit. It becomes possible to match. That is, even when the distance between the recording layers in the recording medium is different from the design value or is non-uniform, the focal points of the light beams emitted from the plurality of light sources are simultaneously accurately adjusted to the respective target recording layers. This enables stable and stable initialization. In the above, it is preferable that the objective lens is single.
[0034]
Preferably, the optical path correcting means is a liquid crystal element or a lens.
[0035]
Further, the wavelengths of the plurality of light sources may be different from each other.
[0036]
Hereinafter, the optical information recording medium, the method for manufacturing the same, and the initialization apparatus of the present invention will be described more specifically with reference to the drawings.
[0037]
(1st Embodiment)
FIG. 1 is a configuration diagram of an apparatus for initializing an optical information recording medium according to a first embodiment of the present invention, and shows a state where an information recording medium 1 having two recording layers is installed. The recording medium 1 includes a first recording layer 5, a transparent separation layer 4 having a thickness of about 0.04 mm, and a second transparent layer 4 having a thickness of about 100 nm on a substrate 6 made of polycarbonate having a thickness of about 1.1 mm. The recording layers 3 are sequentially formed, and the protective film 2 is provided thereon. The recording layers 3 and 5 are formed by grooves having a depth of about 20 nm, a width of about 0.2 μm, and a track pitch of about 0.32 μm. A guide groove (not shown) for tracking laser light during recording and reproduction is provided.
[0038]
FIG. 12 shows a more detailed structure of the recording medium 1. In FIG. 12, the recording layer 3 is made of a dielectric material (ZnS—SiO ₂ , A thickness of 50 nm), a phase change layer 34 of a GeSbTe thin film (7 nm in thickness), and a dielectric material (ZnS—SiO 2). ₂ (Thickness: 40 nm), and the phase change layer 34 changes from an amorphous state to a crystalline state by initialization or the like, whereby the reflectance increases and the transmittance decreases. The recording layer 5 is made of a dielectric material (ZnS-SiO ₂ , A protective layer 36 made of 60 nm thick, a phase change layer 37 made of a GeSbTe thin film (10 nm thick), and a dielectric material (ZnS-SiO ₂ And a reflective layer 39 made of a metal material (Ag alloy, 100 nm thick). The phase change layer 37 changes its state from an amorphous state to a crystalline state, and the reflection state is reduced. The rate increases. The transparent separation layer 4 was formed of a 0.04 mm thick ultraviolet curable resin, and the protective film 2 was formed of a 0.07 mm thick polycarbonate sheet and a 0.01 mm thick ultraviolet curable resin.
[0039]
In FIG. 1, the initialization device includes a spindle motor 7, two optical heads 8a and 8b, a transfer table 9 on which the optical head is installed, a moving unit 10 for moving the transfer table to a desired position, and a controller 11. ing.
[0040]
FIG. 2 shows the structure of the optical heads 8a and 8b. In this optical head, a light beam emitted from a light source 12 composed of a semiconductor laser having a wavelength of 800 nm is focused on a recording medium through a collimator lens 13, a beam splitter 14, a quarter-wave plate 15, and an objective lens 16. The focused light beam is focused on the recording layer in the recording medium by adjusting the position of the objective lens 16 by the voice coil 17. The light reflected from the recording layer passes through the objective lens 16 and the quarter-wave plate 15 again, is reflected by the beam splitter 14, enters the detector 18, is converted into an electric signal, and is used for controlling the voice coil 17. .
[0041]
In FIG. 1, the light beams emitted from the optical heads 8a and 8b are focused on the recording layers 3 and 5, respectively, in the manner described above. The spot shape of the light beam on the recording layer is formed in an oval shape having a length of 100 μm in the radial direction of the recording medium and 1 μm in the circumferential direction. The optical head 8b is arranged on the outer peripheral side of the recording medium by about 1 mm with respect to the optical head 8a. At the time of initialization, the optical heads 8a and 8b are moved by the transfer table 9 while the light beam is focused on the recording layer while rotating the spindle motor 7 on which the recording medium 1 is installed. The recording medium is moved from the side toward the outer circumference at a feed pitch of 50 μm per rotation of the recording medium. At this time, the rotation speed of the spindle motor 7 is controlled so that the linear velocity at the position of the optical head 8a becomes substantially constant. Thereby, the recording layers 3 and 5 can be initialized at the same time, so that a multilayer recording medium having a plurality of recording layers can be initialized in a short time.
[0042]
At this time, since the optical head 8b is disposed on the outer peripheral side of the recording medium in the moving direction of the optical head with respect to the optical head 8a, at the same position on the recording medium, after the recording layer 5 is initialized, The recording layer 3 is initialized. That is, the recording layer 5 is initialized by irradiating a light beam through the recording layer 3 in an uninitialized state (that is, a state with a high transmittance). Therefore, there is an advantage that the initialization of the recording layer 5 can be efficiently performed in a state where the attenuation of the light beam intensity by the recording layer 3 is small, and the initialization of the recording layer 3 is not affected. Therefore, the optical information recording medium having a plurality of recording layers in the present embodiment is a high-performance multilayer recording medium in which the recording layers are not uniformly initialized.
[0043]
Here, the initialization unevenness refers to insufficient crystallization of the recording layer partially or entirely. When information is recorded, rewriting is performed until the crystal state of the recording layer is stabilized. The jitter value, which is the quality of the signal, fluctuates every number of times, and the recorded information cannot be normally reproduced. The variation of the jitter value is preferably within 2%, and a state where the variation is more than that is regarded as the unevenness in initialization.
[0044]
An overwrite test was performed on the multilayer recording medium of the present embodiment at a linear velocity of 5.3 m / s using a laser beam having a wavelength of 405 nm collected by an objective lens having an NA of 0.85. The recorded signal is a PWM recording system in which the length of the mark and the length of the space (that is, the edge positions of the front end and the rear end of the mark) carry information, and 1-7PP of the reference clock T = 15.1 nsec. It is a random signal modulated by the method. The laser light was irradiated in the form of a pulse modulated according to a signal to be recorded, and its peak power and bottom power were set to 10 mW and 4 mW for the recording layer 3 and 10 mW and 5 mW for the recording layer 5. The peak power and the bottom power were selected so as to minimize the jitter value when the random signal was overwritten ten times by changing the power respectively. Under this condition, overwriting was performed ten times, and the jitter value of the reproduced signal was measured each time. As a result, in both of the recording layers 3 and 5, the jitter value was in the range of 10 to 11%. That is, the fluctuation amount of the jitter value was within 1%, and no unevenness in initialization was recognized.
[0045]
On the other hand, when initialization was performed by a conventional method in which the recording layer 3 on the near side as viewed from the light beam irradiation side was initialized first, a similar overwrite test was performed. The JIT value fluctuated within the range of 10 to 14%, and uneven initialization was observed.
[0046]
A preferred positional relationship between the optical heads 8a and 8b will be described below. FIG. 3 is a radial cross-sectional view of the light beam irradiation unit of the recording medium 1 in FIG. The difference z between the radial positions of the light beams 8a 'and 8b' emitted from the optical heads 8a and 8b on the recording medium 1 depends on the radial spot length of the light beam 8a 'on the recording layer 3 and the light beam 8b Let x and y denote the radial spot lengths of the light beam 8b ′ on the recording layer 5, the incident angle of the light beam 8b ′ is θ, and the thickness of the transparent separation layer is d.
z> (x / 2) + (y / 2) + (d · tan θ)
It is preferable to set the positional relationship between the optical heads 8a and 8b so as to satisfy the following relationship.
[0047]
Incidentally, the incident angle θ of the light beam is represented by the following formula, where NA is the numerical aperture of the objective lens, and n is the refractive index of the substrate.
NA = n · sin θ
Have a relationship.
[0048]
Here, the difference z between the radial positions is preferably in the range of 0.1 to 2 mm, the spot lengths x and y are preferably in the range of 50 to 200 μm, the NA is preferably in the range of 0.3 to 0.7, and the transparent separation is performed. The thickness d of the layer is preferably from 10 to 60 μm.
[0049]
In the above, the length of the light beam 8a 'from the center of the spot on the recording layer 3 to the radial end of the spot is x / 2, and the length of the light beam 8b' from the center of the spot on the recording layer 3 is The length to the end of the spot in the direction is (y / 2) + (d · tan θ), which is more light than the sum of the two (x / 2) + (y / 2) + (d · tan θ). Since the distance z between the spot centers of the beams 8a 'and 8b' is large, the light beams 8a 'and 8b' do not overlap on the recording layer 3. That is, the recording layer 5 is irradiated with the light beam 8b 'without passing through the recording layer 3 in the initialized state. If the difference z between the radial positions of the light beams 8a 'and 8b' on the recording medium 1 is made unnecessarily large, the waiting time from the start of the initialization of the recording layer 5 to the start of the initialization of the recording layer 3 is increased. And the time required for the entire initialization becomes longer. However, the tact time (the time for initializing one recording medium) can be set within the allowable range.
[0050]
Further, since the optical heads 8a and 8b are provided on the same transfer table, the transfer mechanism and its control circuit may be equivalent to the case of one optical head, and the size of the apparatus by using two optical heads And the two optical heads can be installed in an accurate positional relationship.
[0051]
Next, the optical heads 8a and 8b are adjusted so that the optimum substrate thickness, at which the spot diameter converged through the substrate becomes minimum, differs in advance according to the distance between the recording layers 3 and 5. An example in which the head is designed will be described.
[0052]
In FIG. 1, the optical system is set so that the optical head 8a has the aforementioned optimum substrate thickness of 0.08 mm, and the optical head 8b has the optical substrate 8b that has the aforementioned optimum substrate thickness of 0.12 mm. Optical system is set. Thus, when the optical head 8a irradiates the recording medium 1 with a light beam, the optical head 8a focuses on the position transmitted through the protective film having a thickness of 0.08 mm, that is, the recording layer 3 without aberration. On the other hand, when the optical head 8b irradiates the recording medium 1 with a light beam, the optical head 8b transmits through the protective film having a thickness of 0.08 mm, the recording layer 3 having a thickness of 100 nm, and the transparent separation layer having a thickness of 0.04 mm, that is, The recording layer 5 is focused almost without aberration. Therefore, there is an advantage that a light beam can be accurately focused on a target recording layer by each optical head, and stable initialization can be performed without unevenness.
[0053]
In the above embodiment, the light beams emitted from the optical heads 8a and 8b have the same spot shape on the recording layer, but may have different spot shapes. The thermal characteristics of the recording layer 3 and the recording layer 5 are different due to the difference in structure, and the shape of the temperature distribution when the light beam is irradiated is different even if the spot shape of the light beam to be irradiated is the same. Therefore, by setting the spot shape in accordance with the thermal characteristics of the recording layer to be initialized, uniform and stable initialization can be performed.
[0054]
In the above embodiment, the combination of the initialization device having two optical heads and the recording medium having two recording layers has been described. However, the number of optical heads may be three or more, By matching the number of optical heads, in a recording medium having n recording layers, it is possible to realize an initialization speed n times faster than in the case of one optical head. FIG. 4 is a configuration diagram of an example in which three optical heads are provided, and shows a state in which an information recording medium 1 ′ having three recording layers is installed. The configuration is the same as that of the initialization device shown in FIG. 1 except that the third optical head 8c is provided. The optical head 8c has the same structure as the optical heads 8a and 8b shown in FIG. The optical head 8c initializes the recording medium 1 'by irradiating a light beam to the recording layer farthest from the light beam irradiating side of the recording medium 1', and is disposed closest to the movement direction among the three optical heads. Have been. As a result, the recording medium having three recording layers can be shortened similarly to the case where the recording medium having two recording layers is initialized by the initialization device having two optical heads described with reference to FIG. In addition to the initialization in time, the recording layer on the far side as viewed from the light beam irradiation side can be initialized without the influence of the unevenness in the initialization of the recording layer on the near side.
[0055]
Further, the moving direction of the optical head when performing the initialization may be a direction from the outer peripheral side to the inner peripheral side of the recording medium. In this case, the optical head 8b may be disposed on the inner peripheral side of the recording medium in the moving direction of the optical head with respect to the optical head 8a.
[0056]
(Second embodiment)
FIG. 5 is a configuration diagram of an apparatus for initializing an optical information recording medium according to the second embodiment of the present invention, and shows a state where the information recording medium 1 is installed. The configuration is the same as that of the optical information recording medium initialization apparatus according to the first embodiment.
[0057]
The optical head 8d has a single objective lens, a light source for irradiating a crystallization light beam for crystallizing the recording layer, and a light source for irradiating a focal position control light beam with an intensity that does not crystallize the recording layer. The structure is shown in FIG.
[0058]
This optical head includes light sources 40 and 41 composed of semiconductor lasers having respective wavelengths of 800 nm and 680 nm.
[0059]
In FIG. 6, a wavelength-selective mirror 46 transmits light having a wavelength of the light source 40 and reflects light having a wavelength of the light source 41. The light beam emitted from the light source 40 passes through the wavelength-selective mirror 46, and is irradiated as a crystallization light beam 49 on the recording layer through the objective lens 47. On the other hand, the light beam emitted from the light source 41 passes through a collimator lens 43, a beam splitter 44, a quarter-wave plate 45, is reflected by a wavelength-selective mirror 46, and is focused on a recording layer of a recording medium through an objective lens 47. It is radiated as a light beam 50 for use. The focal position controlling light beam 50 reflected from the recording layer again passes through the objective lens 47, is reflected by the wavelength selective mirror 46, passes through the quarter wavelength plate 45, is reflected by the beam splitter 44, and is reflected by the detector 51. The incident light is converted into an electric signal. The position of the objective lens 47 is adjusted by controlling the voice coil 48 by the electric signal, and the focal position of the crystallization light beam 49 is adjusted to the recording layer.
[0060]
This initialization device is particularly effective when initializing a recording medium having a very low reflectance in the amorphous state of the recording layer 3 at the wavelength of the crystallization light beam. Normally, a multilayer recording medium is optically designed so that the transmittance of the recording layer on the front side is increased in order to facilitate recording and reproduction on the recording layer on the back side as viewed from the light beam irradiation side. ing. Accordingly, the reflectance of the recording layer on the near side decreases.
[0061]
The optical information recording medium according to one embodiment of the present invention has the same configuration as the multilayer recording medium described with reference to FIG. 12 except for the thickness of each layer.
[0062]
The reflectance and transmittance of each recording layer are wavelength-dependent. The reflectance of the recording layer 3 in the amorphous state with respect to light having a wavelength of 800 nm is 1% and the transmittance is 60%. The reflectance was 10%. The reflectance of the recording layer 3 in the amorphous state with respect to light having a wavelength of 680 nm was 3% and the transmittance was 50%, and the reflectance of the recording layer 5 in the crystalline state was 8%.
[0063]
The initialization of the recording layer 5 is performed prior to the initialization of the recording layer 3 so as not to be affected by unevenness in the initialization of the recording layer 3. Therefore, when the recording layer 3 is initialized, the recording layer 3 is in an amorphous state and the recording layer 5 is in a crystalline state.
[0064]
At this time, when the crystallization light beam having the wavelength of 800 nm is irradiated, the reflected light amount from the recording layer 3 is 1%, whereas the reflected light amount from the recording layer 5 is 3.6% (10% × 60). % X 60%). Therefore, when trying to focus the light beam by a general method such as the knife edge method or the astigmatism method, the intensity ratio of the focus error signal obtained from the recording layer 3 to the focus error signal obtained from the recording layer 5 Is 1 / 3.6.
[0065]
FIG. 7A shows the intensity of the focus error signal obtained from each recording layer at this time. An arrow a indicates an S-shaped curve in the recording layer 3, and an arrow b indicates an S-shaped curve in the recording layer 5. Since the intensity of the focus error signal is three times or more larger in the recording layer 5 than in the recording layer 3, in the recording medium 1 in which the interval between the recording layers 3 and 5 is as short as 0.04 mm, It becomes difficult to separate a focus error signal obtained from the recording layer 3 and the recording layer 5, that is, an S-shaped curve. Therefore, the light beam focuses on the recording layer 5 with a large amount of reflected light, making it difficult to focus on the recording layer 3 with a small amount of reflected light, and initializing the recording layer 3 while focusing with a light beam for crystallization. It is difficult to convert.
[0066]
On the other hand, in the initialization apparatus according to the present embodiment, the focal position of the crystallization light beam is controlled using the focal position control light beam having a wavelength of 680 nm. When a light beam having a wavelength of 680 nm is irradiated, the reflected light amount from the recording layer 3 is 3%, whereas the reflected light amount from the recording layer 5 is 2.5% (10% × 50% × 50%). is there.
[0067]
Therefore, the intensity ratio between the focus error signal obtained from the recording layer 3 and the focus error signal obtained from the recording layer 5 is 3 / 2.5. FIG. 7B shows the intensity of the focus error signal obtained from each recording layer at this time. An arrow a indicates an S-shaped curve in the recording layer 3, and an arrow b indicates an S-shaped curve in the recording layer 5. The intensity of the focus error signal is larger in the recording layer 3, and the recording layer 3 can be reliably focused.
[0068]
Therefore, the optical information recording medium having a plurality of recording layers in the present embodiment is a high-performance multilayer recording medium in which the recording layers are not uniformly initialized.
[0069]
The wavelengths of the crystallization light beam and the focus position control light beam can be set as appropriate according to the optical characteristics of the recording medium.
[0070]
(Third embodiment)
FIG. 8 is a configuration diagram of an apparatus for initializing an optical information recording medium according to the third embodiment of the present invention, and shows a state where the information recording medium 1 having two recording layers described in the first embodiment is installed. Except that the optical heads 8a and 8b are provided on separate transfer tables 9 and 9 ', respectively, the configuration is the same as that of the optical information recording medium initialization apparatus in the first embodiment shown in FIG. is there.
[0071]
The light beams emitted from the optical heads 8a and 8b are focused on the recording layers 3 and 5, respectively. The spot shape of the light beam on the recording layer is formed in an oval shape having a length of 100 μm in the radial direction of the recording medium and 1 μm in the circumferential direction. The optical head 8b is arranged on the outer peripheral side of the recording medium by about 1 mm with respect to the optical head 8a. When initialization is performed, the optical heads 8a and 8b are moved by the transfer tables 9 and 9 'while the light beam is focused on the recording layer while rotating the spindle motor 7 on which the recording medium 1 is set. The recording medium is moved from the inner circumference to the outer circumference at a feed pitch of 50 μm per rotation of the recording medium. At this time, the rotation speed of the spindle motor 7 is controlled so that the linear velocity at the position of the optical head 8a becomes substantially constant. Thereby, the recording layers 3 and 5 can be initialized at the same time, so that a multilayer recording medium having a plurality of recording layers can be initialized in a short time.
[0072]
At this time, since the optical head 8b is disposed on the outer peripheral side of the recording medium in the moving direction of the optical head with respect to the optical head 8a, at the same position on the recording medium, after the recording layer 5 is initialized, The recording layer 3 is initialized. That is, the recording layer 5 is initialized by irradiating a light beam through the recording layer 3 in an uninitialized state (that is, a state with a high transmittance). Therefore, the recording layer 5 can be initialized efficiently with little attenuation of the light beam intensity by the recording layer 3 and without the influence of the unevenness in the initialization of the recording layer 3.
[0073]
Further, by providing the optical heads 8a and 8b on separate transfer tables, the apparatus scale is slightly increased, but there is an advantage that the manufacturing cost can be reduced by using the conventional transfer mechanism.
[0074]
The moving direction of the optical head when performing the initialization may be a direction from the outer peripheral side to the inner peripheral side of the recording medium. In this case, the optical head 8b may be disposed on the inner peripheral side of the recording medium in the moving direction of the optical head with respect to the optical head 8a.
[0075]
Further, similarly to the initialization device according to the second embodiment, two light sources may be provided, a light source for irradiating the optical head with a crystallization light beam and a light source for irradiating a focal position control light beam.
[0076]
(Fourth embodiment)
A fourth embodiment of the present invention relates to an initialization method and an initialization apparatus for an optical information recording medium having a plurality of recording layers and having a small reflectance in an amorphous state of a recording layer on the near side as viewed from the light beam irradiation side. It is about.
[0077]
FIG. 9 is a configuration diagram of an initialization device according to the present embodiment, and shows a state in which the information recording medium 1 having two recording layers described in the second embodiment is installed. The configuration is the same as that of the initialization device according to the first embodiment shown in FIG. 1 except that a counter 52 for counting the number is provided, and includes the optical head shown in FIG.
[0078]
When the recording layer 3 is initialized, the intensity of the light beam emitted from the optical head 8a is controlled to be sufficient by the controller 11 at the start of the initialization so that the voice coil 17 in FIG. The focus position of the light beam is moved up and down a predetermined number of times by driving and moving the objective lens 16 up and down. The range in which the focal position of the light beam is raised or lowered is an area including at least the recording layer 3, and here, 100 μm based on a predetermined position. At this time, the number of vertical movements of the objective lens is counted by the counter 52, and the number of times is controlled by the controller 11.
[0079]
By this operation, the recording layer 3 is partially crystallized, and the optical head 8a is focused on the recording layer 3 by using the reflected light from the partially crystallized recording layer 3 having increased reflectance. This makes it possible to initialize the light beam by focusing on the recording layer 3 without fail.
[0080]
The number of vertical movements of the objective lens is set in accordance with the relative speed of the recording medium and the optical head and the speed of vertical movement, and is preferably two or more.
[0081]
This initialization method is particularly effective when initializing a recording medium having a very low reflectance in the amorphous state of the recording layer 3 at the wavelength of the light beam emitted from the optical head 8a.
[0082]
The optical information recording medium according to the embodiment of the present invention has the same configuration as the multilayer recording medium described with reference to FIG. 12 except for the film thickness of each layer. The reflectance in the crystalline state is 6%, the transmittance in the amorphous state is 60%, and the transmittance in the crystalline state is 30%. The reflectance of the recording layer 5 in the amorphous state is 15% and the reflectance in the crystalline state is 15%. The reflectance is 10%. In a state where the recording layer 5 has been initialized and the recording layer 3 has not been initialized, the amount of light reflected from the recording layer 5 is 3.6% (10% × 60% × 60%), whereas The amount of reflected light from No. 3 is 1%.
[0083]
Therefore, when trying to focus the light beam by a general method such as the knife edge method or the astigmatism method, the intensity ratio of the focus error signal obtained from the recording layer 3 to the focus error signal obtained from the recording layer 5 Is very small, 1 / 3.6. FIG. 10A shows the intensity of the focus error signal obtained from each recording layer at this time, and arrows a and b are S-shaped curves in the recording layer 3 and the recording layer 5, respectively.
[0084]
Since the intensity of the focus error signal is three times or more larger in the recording layer 5 than in the recording layer 3, in the recording medium 1 in which the interval between the recording layers 3 and 5 is as short as 0.04 mm, It becomes difficult to separate a focus error signal obtained from the recording layer 3 and the recording layer 5, that is, an S-shaped curve. Therefore, the light beam focuses on the recording layer 5 with a large amount of reflected light, making it difficult to focus on the recording layer 3 with a small amount of reflected light, and initializing the recording layer 3 while focusing with a light beam for crystallization. It is difficult to convert.
[0085]
However, at the start of the initialization of the recording layer 3, the focal position of the optical head 8 a is moved up and down with a light beam intensity sufficient for the initialization to partially crystallize the recording layer 3, so that the recording layer 3 The reflected light amount is 6%, the reflected light amount from the recording layer 5 is 0.9% (10% × 30% × 30%), and the focus error signal obtained from the recording layer 3 and the focus error signal obtained from the recording layer 5 are different. The intensity ratio becomes 6 / 0.9. FIG. 10B shows the intensity of the focus error signal obtained from each recording layer at this time, and arrows a and b are S-shaped curves in the recording layer 3 and the recording layer 5, respectively. The intensity of the focus error signal is much higher in the recording layer 3, and the recording layer 3 can be reliably focused.
[0086]
FIG. 10C shows the intensity of the focus error signal obtained from each recording layer during initialization. Arrows a and b are S-shaped curves in the recording layer 3 and the recording layer 5, respectively. In the case of the present embodiment in which the radial length of the light beam on the recording layer is 100 μm and the feed pitch is 50 μm, half of the light beam spot covers the initialized area, so the amount of light reflected from the recording layer 3 Is 3.5% ((1% + 6%) / 2) and the amount of reflected light from the recording layer 5 is 2.25% ((3.6% + 0.9%) / 2). The intensity ratio between the focus error signal obtained and the focus error signal obtained from the recording layer 5 is sufficiently large as 3.5 / 2.25, and the light beam can be focused on the recording layer 3 without fail.
[0087]
Therefore, the optical information recording medium having a plurality of recording layers in the present embodiment is a high-performance multilayer recording medium in which the recording layers are not uniformly initialized.
[0088]
The relationship between the shape of the light beam spot and the feed pitch is preferably set such that the focus error signal obtained from the recording layer 3 is larger than the focus error signal obtained from the recording layer 5.
[0089]
Also, as a method of expanding the initialization range per one time by reducing the range of vertical movement of the objective lens, a light beam is once focused on a recording layer having a large amount of reflected light and a large amplitude of an S-shaped curve. There is also a method of initializing after specifying the position of the recording layer.
[0090]
At the start of the initialization of the recording layer 3, after performing a focusing operation for focusing a light beam emitted from the optical head 8 a on the recording layer 5, the focusing operation is stopped and the focal position of the optical head 8 a is changed to the recording layer 3. It is preferable that the optical head 8a be moved up and down with a light beam intensity sufficient for initialization after being lowered by 0.04 mm corresponding to the distance between the optical head 8a and the recording layer 5. This makes it possible to ensure that the focal point of the light beam passes through the recording layer 3 when the optical head 8a moves up and down a short distance. Therefore, the partial crystallization of the recording layer 3 at the start of the initialization can be reliably performed, and the collision of the optical head 8a with the recording medium can be prevented. Here, when the recording layer 3 is partially crystallized by mistake before focusing on the recording layer 5, the amount of light reflected from the recording layer 3 increases, and the amount of light reflected from the recording layer 5 decreases. Therefore, the recording layer 5 is mistakenly focused on the recording layer 3, and as a result, there is a possibility that an error occurs in the position of the optical head 8 a when the recording layer 3 is initialized. Therefore, when the light beam is focused on the recording layer 5, it is preferable that the intensity is set to an intensity at which the recording layer 3 is not crystallized. This can prevent the recording layer 3 from being partially crystallized by mistake before focusing on the recording layer 5. That is, the position of the optical head 8a at the time of initializing the recording layer 3 can be set correctly.
[0091]
(Fifth embodiment)
The optical information recording medium initialization apparatus according to the fifth embodiment of the present invention has the same configuration as the optical information recording medium initialization apparatus according to the first embodiment shown in FIG. 1 except for the optical head. . FIG. 11 shows the configuration of the optical head. This optical head includes light sources 19 and 20 composed of semiconductor lasers having wavelengths of 680 nm and 800 nm, respectively, and different wavelengths from each other.
[0092]
In FIG. 11, a wavelength selective mirror 27 transmits light having a wavelength of the light source 19 and reflects light having a wavelength of the light source 20. The light beam emitted from the light source 20 passes through a collimator lens 22, a beam splitter 24, a 波長 wavelength plate 26, is reflected by a wavelength selective mirror 27, and is condensed on the recording layer 5 through an objective lens 28. The light beam reflected from the recording layer 5 passes through the objective lens 28 again, is reflected by the wavelength-selective mirror 27, passes through the quarter-wave plate 26, is reflected by the beam splitter 24, and is incident on the detector 32. The signal is converted into a signal and used for controlling the voice coil 29. On the other hand, the light beam emitted from the light source 19 passes through an optical path correcting means 30 composed of a liquid crystal element, a collimator lens 21, a beam splitter 23, a quarter wavelength plate 25, passes through a wavelength selective mirror 27, and passes through an objective lens 28. The light is focused on the recording layer 3. The light beam reflected from the recording layer 3 passes through the objective lens 28 again, passes through the wavelength-selective mirror 27, passes through the quarter-wave plate 25, is reflected by the beam splitter 23, enters the detector 31, and The signal is converted into a signal and used for controlling the optical path correction unit 30.
[0093]
The light beam emitted from the light source 20 is focused on one recording layer 5 in the recording medium 1 having two recording layers by adjusting the position of the objective lens 28 by the voice coil 29. At the same time, when the focus of the light beam emitted from the light source 19 is to be accurately focused on the other recording layer 3, the fluctuation of the recording layer position due to the surface deflection of the recording medium 1 causes the recording layer 5 and the recording layer 5 to change. Since it is common, the light beam from the light source 20 is compensated by focusing on the recording layer 5 as described above. However, the fluctuation due to the uneven thickness of the transparent separation layer 4 is independent of the recording layer 5. Therefore, this method alone cannot compensate.
[0094]
In order to compensate for the variation inherent in the recording layer 3, the initialization apparatus according to the present embodiment operates the optical path correction unit 30 to change the distribution of the intensity and phase of the light beam, thereby obtaining the uneven thickness of the transparent separation layer 4. By adjusting the focal position in accordance with the above, the light beam emitted from the light source 19 can be accurately focused on the recording layer 3.
[0095]
Therefore, according to the initialization apparatus of the present embodiment, the light beam emitted from one light source is focused on a specific recording layer by moving the objective lens, and the light beam emitted from another light source is The optical path correction means can focus on another recording layer. Thereby, even when the thickness of the transparent separation layer 4 in the recording medium is different from the design value or non-uniform, the focal points of the light beams emitted from the plurality of light sources are simultaneously focused on the respective target recording layers. Accurate matching can be achieved, and stable and stable initialization can be performed. In addition, when the same objective lens is used, the shorter wavelength light has a shorter focal length than the longer wavelength light, so that the recording layer 3 close to the light beam incident surface of the recording medium can be initialized. By making the wavelength of the light source 19 used shorter than the wavelength of the light source 20 used for initializing the recording layer 5 far from the light beam incident surface, the design of the optical system becomes easier.
[0096]
In the above embodiment, the optical path correcting means is a liquid crystal element. However, the optical path correcting means may be constituted by a lens having a movable mechanism such as a piezoelectric element, or may be installed between the collimator lens 21 and the beam splitter 23. .
[0097]
Further, the optical path correcting means 30 is provided on a unique optical path of the light beam emitted from the light source 20, and the operation of focusing the light beam emitted from the light source 19 on the recording layer 5 is performed by the voice coil 29 at the position of the objective lens 28. And the focal position of the light beam emitted from the light source 20 may be adjusted by operating the optical path correction unit 30.
[0098]
Further, the position of the light beam applied to the recording layer 5 is arranged on the moving direction side of the optical head relative to the position of the light beam applied to the recording layer 3 so that the two light beams do not overlap on the recording layer. In this example, there is an advantage that the recording layer 5 can be initialized without being affected by the unevenness in the initialization of the recording layer 3.
[0099]
In the above embodiment, the wavelength of the light source 19 used for initializing the recording layer 3 near the light beam incident surface of the recording medium is shorter than the light source 20 used for initializing the recording layer 5 far from the light beam incident surface. However, in the case where the recording layer 3 is made of a material whose transmittance increases as the wavelength becomes shorter, the wavelength of the light source 19 may be longer than the wavelength of the light source 20.
[0100]
Further, the number of light sources may be three or more, and does not need to match the number of recording layers of the recording medium.
[0101]
Further, although semiconductor lasers having different wavelengths are used as light sources, the optical paths of the light beams emitted from the light sources 19 and 20 are set to different angles, and the positions where the reflected light from the recording medium forms an image at the detector are different. For example, when using another means for separating the reflected light from the recording medium of the light beams emitted from different light sources, the light sources may have the same wavelength.
[0102]
In the first to fifth embodiments, the wavelength of the light source and the numerical aperture of the objective lens can be appropriately designed according to the optical characteristics of the recording layer in the recording medium to be initialized, the thickness of the substrate, and the like.
[0103]
In the above description, the disc-shaped information recording medium is used, but the present invention can also be applied to a multi-layered recording medium having another shape such as a card.
[0104]
【The invention's effect】
As described above, according to the method and the apparatus for manufacturing an optical information recording medium of the present invention, the focus servo is stable, and a multilayer recording medium having a plurality of recording layers can be initialized uniformly and in a short time. Can be Further, the optical information recording medium of the present invention is a high-performance multilayer recording medium having no initialization unevenness in the recording layer.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional configuration diagram illustrating an apparatus for initializing an optical information recording medium according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram illustrating a main part of an apparatus for initializing an optical information recording medium according to the first embodiment of the present invention.
FIG. 3 is an explanatory sectional view showing a main part of the optical information recording medium according to the first embodiment of the present invention.
FIG. 4 is a partial cross-sectional configuration diagram showing an embodiment of an optical information recording medium initialization device according to the first embodiment of the present invention.
FIG. 5 is a partial cross-sectional configuration diagram illustrating an apparatus for initializing an optical information recording medium according to a second embodiment of the present invention.
FIG. 6 is a partial cross-sectional configuration diagram illustrating a main part of an apparatus for initializing an optical information recording medium according to a second embodiment of the present invention.
FIGS. 7A and 7B are waveform diagrams showing an example of a focus error signal obtained from the optical information recording medium initialization device according to the second embodiment of the present invention.
FIG. 8 is a partial cross-sectional configuration diagram illustrating an apparatus for initializing an optical information recording medium according to a third embodiment of the present invention.
FIG. 9 is a partial cross-sectional configuration diagram illustrating an apparatus for initializing an optical information recording medium according to a fourth embodiment of the present invention.
FIGS. 10A, 10B, and 10C are waveform diagrams showing an example of a focus error signal obtained from an optical information recording medium initialization device according to a fourth embodiment of the present invention.
FIG. 11 is a partial cross-sectional configuration diagram illustrating an apparatus for initializing an optical information recording medium according to a fifth embodiment of the present invention.
FIG. 12 is a sectional view showing an example of the optical information recording medium of the present invention.
[Explanation of symbols]
1 Optical information recording medium
2 Protective film
3,5 Recording layer
4 Transparent separation layer
5 Reflective layer deposition chamber
6 substrate
7 Spindle motor
8a, 8b, 8c, 8d optical head
8a ', 8b' light beam
9,9 'transfer table
10,10 'means of transportation
11, 11 'controller
12,19,20 Light source
13,21,22 Collimator lens
14,23,24 beam splitter
15, 25, 26 quarter-wave plate
16,28 Objective lens
17,29 Voice coil
18, 31, 32 detector
27 Wavelength selective mirror
30 Optical path correction means
33, 35, 36, 38 protective layer
34, 37 phase change layer
39 Reflective layer

Claims (28)

An optical information recording medium having a plurality of recording layers, wherein the reflectance of at least one of the plurality of recording layers in an uninitialized state with respect to an initialization light beam is smaller than the reflectance after initialization. So,
The recording layer on the deeper side as viewed from the light beam irradiation side of the plurality of recording layers is irradiated with the light beam first, and the recording layer on the near side is irradiated with the light beam later to initialize the recording layer. Optical information recording medium. 2. The optical information according to claim 1, wherein the reflectance of the at least one of the plurality of recording layers in an uninitialized state with respect to the initialization light beam is 以下 or less of the reflectance after initialization. 3. recoding media. 2. The optical information recording medium according to claim 1, wherein the recording layer on the back side and the recording layer on the near side are initialized at the same time by changing the positions by one light beam irradiation operation. 2. The optical information recording medium according to claim 1, wherein the initialized recording layer has no initialization unevenness. When initializing an optical information recording medium having a plurality of recording layers,
Irradiating each of the plurality of recording layers with a different light beam,
At a position on the optical information recording medium at the same distance as viewed from the radial direction, a light beam is first radiated to a recording layer deeper in the plurality of recording layers as viewed from the light beam irradiation side, A method for manufacturing an optical information recording medium, comprising: irradiating a recording layer on the side with a light beam later; and simultaneously initializing the plurality of recording layers by changing the positions thereof by a light beam irradiation operation. The light beam is provided in an optical head, while moving a plurality of optical heads provided on the same surface side with respect to the recording medium in a predetermined direction,
By using an optical head disposed on a more initialization progress direction side, of the plurality of recording layers, a light beam is radiated to a recording layer which is deeper when viewed from a light beam irradiation side, and the plurality of recording layers are irradiated. 6. The method for manufacturing an optical information recording medium according to claim 5, wherein the initialization is simultaneously performed. The method for manufacturing an optical information recording medium according to claim 6, wherein the spot shapes of the light beams emitted from at least two of the plurality of optical heads are different from each other. 6. The method according to claim 5, wherein, when initializing the at least one recording layer, a focal position of the crystallization light beam is controlled using a focal position control light beam different from a crystallization light beam for crystallizing the recording layer. 3. The method for producing an optical information recording medium according to item 1. When initializing the at least one recording layer, at the beginning of the initialization, the focal position of the optical head is moved up and down with a light beam intensity sufficient for the initialization to partially crystallize the recording layer. 6. The method for producing an optical information recording medium according to item 5. When initializing the at least one recording layer, at the beginning of the initialization, after focusing on a recording layer that provides a larger amount of reflected light than the recording layer, the focal position of the optical head is changed to the thickness of the recording medium. 6. The method for manufacturing an optical information recording medium according to claim 5, wherein the target recording layer is initialized by moving a predetermined distance in the vertical direction. After focusing on a recording layer that provides a larger amount of reflected light than the recording layer with the intensity of the light beam that does not crystallize the target recording layer, the focal position of the optical head is set in advance in the thickness direction of the recording medium. The method for manufacturing an optical information recording medium according to claim 5, wherein the target recording layer is partially crystallized by moving the recording layer up and down around a position separated by a predetermined distance. After focusing on a recording layer that provides a larger amount of reflected light than the recording layer with the intensity of a light beam that does not crystallize the target recording layer, the focal position of the optical head is shifted by a predetermined distance to the recording medium. 6. The method for manufacturing an optical information recording medium according to claim 5, wherein the target recording layer is initialized by moving the light beam in a thickness direction of the optical recording medium to a sufficient intensity for initializing the target recording layer. The spot width of the light beam for initializing the recording layer on the near side as viewed from the light beam irradiation side is x, the spot width and the incident angle of the light beam for initializing the recording layer on the back side are y and θ, and the light beams are Is the distance of z and the distance between the recording layers is d,
z> (x / 2) + (y / 2) + (d · tan θ)
6. The method for manufacturing an optical information recording medium according to claim 5, wherein the positional relationship of the optical head is set so as to satisfy the following relationship. A method for manufacturing an optical information recording medium having a plurality of recording layers, wherein when initializing at least one recording layer, a focus position controlling light beam different from a crystallization light beam for crystallizing the recording layers is used. And an initialization step of controlling a focal position of the crystallization light beam. The method for manufacturing an optical information recording medium according to claim 14, wherein, of the plurality of recording layers, a layer at the back as viewed from the light beam irradiation side is initialized, and then a layer at the front is initialized. While moving a plurality of optical heads provided on the same surface side with respect to the recording medium in a predetermined direction, using an optical head arranged on a more initialization proceeding direction side, of the plurality of recording layers, 15. The method for manufacturing an optical information recording medium according to claim 14, wherein a light beam is applied to a recording layer farther from the light beam irradiation side to initialize the plurality of recording layers simultaneously. An apparatus for initializing an optical information recording medium having a plurality of recording layers,
A plurality of optical heads provided on the same surface side with respect to the recording medium and irradiating a light beam to the different recording layers, and a movement system for moving the optical head in a predetermined direction,
Of the plurality of optical heads, an optical head that irradiates a light beam to a recording layer on a deeper side as viewed from a light beam irradiation side of the plurality of recording layers, is disposed on a more initialization progress direction side. For initializing an optical information recording medium. The spot width of the light beam for initializing the recording layer on the near side as viewed from the light beam irradiation side is x, the spot width and the incident angle of the light beam for initializing the recording layer on the back side are y and θ, and the light beams are Is the distance of z and the distance between the recording layers is d,
z> (x / 2) + (y / 2) + (d · tan θ)
18. The initialization apparatus according to claim 17, wherein the positional relationship between the optical heads is set so as to satisfy the following relationship. 18. The initialization apparatus according to claim 17, wherein spot shapes of light beams emitted from at least two of the plurality of optical heads are different from each other. A spindle motor that rotates the recording medium, a plurality of optical heads that irradiate light beams to different recording layers of the recording medium, a transfer table on which the optical head is installed, and a moving system that moves the transfer table to a desired position. 18. The initialization apparatus according to claim 17, further comprising: arranging the plurality of optical heads such that light beams emitted from the respective optical heads have different radial positions on the recording medium. 21. The initialization apparatus according to claim 20, wherein the plurality of optical heads are installed on a same transfer table. 21. The initialization apparatus according to claim 20, wherein the optimum substrate thicknesses at which the spot diameter of the light irradiated from the plurality of optical heads onto the recording medium through the substrate is minimized are different from each other. At least one of the plurality of optical heads includes a driving system for moving an objective lens provided in the optical head up and down, a counter for counting the number of times the objective lens has been moved up and down, and irradiation from the optical head. 18. The initialization apparatus according to claim 17, further comprising: a controller that controls an intensity of a light beam to be performed and the driving system; and a movement system that moves the optical head in a predetermined direction. At least one optical head and a movement system for moving the optical head in a predetermined direction, wherein at least one of the optical heads has a single objective lens and a crystallization light beam for crystallizing a recording layer. An initialization apparatus for an optical information recording medium, comprising: a light source for irradiating; and a light source for irradiating a light beam for controlling a focal position having an intensity that does not crystallize a recording layer. A plurality of optical heads are provided on the same surface side with respect to the recording medium and irradiate the recording layers different from each other with a light beam, and among the plurality of optical heads, from a light beam irradiation side of the plurality of recording layers. 25. The initialization apparatus according to claim 24, wherein an optical head that irradiates a light beam to a recording layer that is deeper than the optical recording medium is disposed closer to the initialization direction. The initialization apparatus according to claim 24, wherein the optical head has an objective lens and a plurality of light sources, and includes an optical path correction system on a unique optical path of a light beam emitted from at least one light source. The initialization apparatus according to claim 26, wherein the optical path correction system is a liquid crystal element or a lens. The initialization apparatus according to claim 26, wherein wavelengths of the plurality of light sources are different from each other.

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