JP2004241028A - Manufacturing method of optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical information recording medium, the method uniformly initializing a plurality of recording layers in a short period of time with a conventional initializing device. <P>SOLUTION: The method for manufacturing an optical information recording medium comprises a first process in which a first light-permeable substrate 1 on which a first information storage layer 2 is formed and a second substrate 5 on which a second information storage layer 4 is formed are preliminarily prepared; a second process in which the first information storage layer is initialized by irradiating the layer with a first laser light from over the first information storage layer; a third process in which an intermediate layer 3, which comprises an adhesive and optically separates the layer, is applied to the first information storage layer; a fourth process in which the first substrate and the second substrate are jointed via the intermediate layer by facing the first information storage layer to the second information storage layer; and a fifth process in which the second information storage layer is initialized by irradiating the layer with a second laser light from the first substrate side. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a multilayer phase-change optical information recording medium capable of optically recording and reproducing information.
[0002]
[Prior art]
Generally, an optical information recording medium such as an optical disk has a first protective layer, a phase-change recording layer, a second protective layer, and a reflective layer on a substrate on which a guide groove for laser light and the like are formed. Are laminated in this order, and a protective film is formed thereon. Such an optical disk is known as, for example, a DVD-RW, a DVD-RAM, or the like using an optical system having an objective lens with an aperture ratio (NA) of 0.6.
In recent years, in order to further increase the recording capacity (higher density), research and development for increasing the areal density in the two-dimensional direction has been promoted, and commercialization thereof is awaited. For this purpose, the system must be a system using an objective lens having a high NA with a shorter wavelength of the recording / reproducing light, and various proposals have been made.
[0003]
However, there is a technical limit to shortening the wavelength of the recording / reproducing laser beam and increasing the NA of the objective lens, and the improvement of the areal density in the two-dimensional direction has leveled off. Therefore, a so-called multilayer optical information recording medium having a large number of recording surfaces in a three-dimensional direction has been studied. This optical information recording medium has been proposed in, for example, Japanese Patent Application Laid-Open No. 9-198709. Further, a method of collectively initializing such a multilayer optical information recording medium is proposed in Japanese Patent Application Laid-Open No. 9-91700.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 9-198709 [Patent Document 2]
JP-A-9-91700
[Problems to be solved by the invention]
By the way, the initialization method disclosed in Patent Document 2 is performed by an optical pickup having a plurality of optical heads, which complicates the apparatus. Further, although a method of simultaneously initializing a plurality of recording layers that are multilayered by one optical head is also disclosed, two recording layers of a multilayer optical recording medium do not adversely affect each other's recording layers. It is very difficult to initialize efficiently in such a short processing time.
Further, in order to initialize the first recording layer having a high transmittance, it is necessary to irradiate a laser beam having a power higher than the initializing power used when initializing a standard single recording layer. However, in this case, excessive light energy or heat energy is applied to the second recording layer, and it is not possible to set each recording layer to an optimal initialization state. Conversely, when the second recording layer is initialized to an optimum state, there is a problem that the initial recording power of the first recording layer is insufficient and sufficient crystallization cannot be performed thereon.
[0006]
It is also conceivable to adjust the initialization sensitivity of the recording layers of each layer to initialize the first recording layer and the second recording layer at the same time, but it is quite difficult to realize this.
The present invention has been proposed in view of such a conventional situation, and an object of the present invention is to provide an optical disc which can initialize a plurality of recording layers in a short time and uniformly with a conventional initialization apparatus. An object of the present invention is to provide a method for manufacturing an information recording medium.
[0007]
[Means for Solving the Problems]
The present invention provides a first step of preparing a light-transmissive first substrate on which a first information storage layer is formed in advance and a second substrate on which a second information storage layer is formed; Irradiating a first laser beam from above the information storage layer to initialize the first information storage layer; and optically separating the first information storage layer from an adhesive made of an adhesive. A third step of applying an intermediate layer to be bonded, and bonding the first substrate and the second substrate via the intermediate layer with the second information storage layer facing the first information storage layer And a fifth step of irradiating a second laser beam from the first substrate side to initialize the second information storage layer. This is a method for manufacturing a medium.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an optical information recording medium according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing an optical information recording medium of the present invention, and FIG. 2 is a configuration diagram showing details of the optical information recording medium shown in FIG.
Here, a description will be given of a phase-change type optical disk having two recording layers that can be optically recorded and reproduced as an optical information recording medium. In this optical disc D, as shown in FIG. 1, a first information storage layer 2, an intermediate layer 3, a second information storage layer 4, and a second substrate 5 are formed on a first substrate 1. It is configured by being sequentially laminated. In FIG. 1, an arrow a indicates the incident direction of the initialization laser light and the recording or reproducing laser light (neither is shown).
[0009]
As shown in detail in FIG. 2, the first information storage layer 2 includes a first dielectric layer 21, a first phase-change recording layer 22, a second dielectric layer 23, and a first dielectric layer 23. The reflective layer 24 and the high refractive index layer 25 are sequentially laminated. Further, the second information storage layer 4 includes a third dielectric layer 41, a second phase change type recording layer 42, a fourth dielectric layer 43, and a second reflective layer 44 sequentially. Laminated.
The first substrate 1 is a light-transmitting substrate through which the initialization laser light and the recording or reproduction laser light can pass from the arrow a side. The second substrate 5 does not need to be translucent because recording / reproducing light is not incident thereon, but it is preferable to use a substrate similar to the first substrate 1 in consideration of production efficiency. As shown in FIG. 2, the first substrate 1 and the second substrate 5 are provided with pre-grooves 1a (so-called empty grooves) and pre-pits 1b for guiding the laser beam. As the substrates 1 and 5, a plastic substrate such as a polycarbonate resin, a polyolefin resin, and an acrylic resin or a glass substrate is used.
[0010]
The pre-grooves 1a and pre-pits 1b formed on the first substrate 1 have a function of guiding laser light, and the pre-grooves 1a and pre-pits 1b are directly injection-molded and formed on a smooth substrate. It is formed by a 2P method (photopolymer method).
The first substrate 1 having the above-described configuration is provided with a constant angular velocity (CAV), a constant linear velocity (CLV), a constant linear velocity (CLV), a ZCV (zone constant velocity), a ZCLV (zone-constant periodicity), and a ZCLV (zone-constant-line-constant). At the head of each sector, an address signal is recorded in advance as emboss pits. In addition, it may meander in a specific cycle.
[0011]
Next, a method of manufacturing the two-layer optical information recording medium D having the above-described configuration will be described.
First, a method for manufacturing the first information recording layer 1 will be described. The first substrate 1 is set in a vacuum film forming apparatus (not shown), and the first dielectric layer 21 of the first information storage layer 2 and the first phase change type recording layer 22 , A second dielectric layer 23, a first reflective layer 24, and a high refractive index layer 25 are formed in vacuum in this order. As the vacuum film formation method, resistance heating type or electron beam type vacuum evaporation, direct current or alternating current sputtering, reactive sputtering, ion beam sputtering, ion plating and the like are used.
[0012]
Next, a method for manufacturing the second information storage layer 4 will be described. Each layer is stacked in the same manner as the first information storage layer 2, but the order of stacking is opposite to that of the first information storage layer 2. That is, the second substrate 5 is set in a vacuum film forming apparatus (not shown), and the second reflective layer 44, the fourth dielectric layer 43, and the second phase change type recording layer 42 And the third dielectric layer 41 are sequentially vacuum-formed in this order.
Here, when the high refractive index layer 25 is provided on the first reflective layer 24 in the first information storage layer 2 as described above, the transmittance can be increased. As the high refractive index layer 25, a metal oxide, nitride, or sulfide is used. For example, ZnS—SiO ₂ , ZnS, SiO ₂ , Ta ₂ O ₅ , Si ₃ N ₄ , AlN, Al ₂ O ₃ , A simple substance such as AlSiON, ZrO ₂ , TiO ₂ , or a mixture thereof is used. N, which is the real part of the complex refractive index of the medium accompanying the absorption of light, is “2 <n <2.8”, the absorption coefficient k is “k <0.1”, and is as transparent and high as possible. The mixing ratio of the metal and oxygen, nitrogen, sulfur and the like is controlled so as to have a refractive index.
[0013]
As shown in FIG. 2, the first dielectric layer 21, the second dielectric layer 23, the third dielectric layer 41, and the fourth dielectric layer 43 are made of a metal oxide, nitride, or sulfide. For example, a simple substance such as ZnS—SiO ₂ , ZnS, SiO ₂ , Ta ₂ O ₅ , Si ₃ N ₄ , AlN, Al ₂ O ₃ , AlSiON, ZrO ₂ , TiO ₂ , or a mixture thereof is used. .
[0014]
The thickness of each of the first dielectric layer 21 and the third dielectric layer 41 is in the range of 10 nm to 300 nm. The optimum film thickness varies depending on the wavelength of the laser beam used, but it is preferably 30 nm to 200 nm in order to increase the reproduction signal. The first phase-change recording layer 22 and the second phase-change recording layer 42 are made of a phase-change material that uses a change in amorphous-crystal reflectance or a change in refractive index, for example, Ge-Sb-Te. System, Ag-In-Te-Sb system and the like. The film thickness of the first phase change type recording layer 22 is preferably 2 nm to 10 nm, and more preferably 3 nm to 7 nm in order to enable rewriting while increasing the transmittance and increase the reproduction signal. If the film thickness is reduced to 3 nm or less, the transmittance increases, but the crystallization speed is extremely reduced, and rewriting cannot be performed. Further, the reproduction output of the recording signal is significantly reduced. Conversely, if the film thickness is greater than 7 nm, the transmittance decreases, and it becomes impossible to guide light sufficient for recording on the second information storage layer 4.
[0015]
The thickness of the second phase change type recording layer 42 is preferably 7 nm to 30 nm, and more preferably 8 nm to 15 nm in order to reduce the cross erase while increasing the recording sensitivity. When the film thickness is set to 8 nm or less, the recording sensitivity decreases. Conversely, when the film thickness is set to 15 nm or more, the recording sensitivity improves but the cross erase increases.
(SbTe) M (where M is at least one of Ge, Ag, In, Ga, Cu, and Al) based phase change using a composition region near the eutectic point of (Sb ₇₀ Te ₃₀ ) When the type recording material is used as a first phase change type recording layer of a multilayer phase change type optical information recording medium with a thickness as thin as 10 nm or less, a conventional single layer information recording medium DVD If the composition of the RW is Sb ₆₅ Te ₂₅ M ₁₀ (M is Ag and In. Sb / Te = 2.6), the crystallization rate is low, so that initialization cannot be performed.
[0016]
In the DVD-RW, the thickness of the phase-change recording layer is from 10 nm to 20 nm. However, when the thickness is reduced to 10 nm or less so as to increase the transmittance for multi-layering, crystallization becomes difficult. This is because when the recording layer is thinner than when the recording layer is thicker, the heat generated by the irradiation of the laser beam escapes faster, so that the recording material heated above the melting point cools rapidly and the liquid phase This is because the state becomes a frozen amorphous state. For this reason, it is necessary to increase the Sb amount, that is, increase the Sb / Te ratio to increase the crystallization speed so that the amorphous state does not occur even with rapid cooling. Sb has a property of being crystallized immediately after film formation when formed into a thin film by itself. The Sb / Te ratio that can crystallize even an extremely thin recording layer having a film thickness of 10 nm or less depends on the film forming apparatus, film forming conditions, the sputtering gas pressure in the case of the sputtering method, the power input to the target, and the like. No value can be specified. However, the present inventors have examined that when the Sb / Te ratio of the first phase change type recording layer 22 is increased as compared with the Sb / Te ratio of the recording material used for the second phase change type recording layer 42, It has been found that crystallization of the first phase change type recording layer 22 easily occurs.
Since the film thickness of the first phase change recording layer 22 is smaller than the film thickness of the second phase change recording layer 42, the heat generated by the laser light is cooled more quickly. Therefore, in order to increase the crystallization speed of the material of the first phase-change recording layer 22, it is necessary to increase the Sb content compared to the material of the second phase-change recording layer.
[0017]
The second dielectric layer 23 and the fourth dielectric layer 43 control the heat conduction to the first and second reflective layers 24 and 44, respectively, and adjust the recording sensitivity and the cross erase characteristics. The film thickness is preferably 5 nm to 50 nm.
The intermediate layer 3 optically separates the first information storage layer 2 and the second information storage layer 4 at the time of recording and reproduction, and at the time of recording or initialization, the first information storage layer 2 and the second information storage layer 2 are separated from each other. Has the effect of cutting off heat so that the information storage layer 4 is not heated at the same time. That is, the information recorded in the first information storage layer 2 and the information recorded in the second information storage layer 4 are not mutually recorded, and the information recorded in the first information storage layer 2 and the second The thickness of the intermediate layer 3 is set so that the information recorded in the information storage layer 4 cannot be mutually reproduced. Further, it has a function of preventing heat from being conducted to the second information storage layer 4 when the first information storage layer 2 is initialized. The film thickness varies depending on the wavelength of laser light used for recording and reproduction and the numerical aperture (NA) of the objective lens. When the wavelength is 650 nm and NA = 0.6, when the intermediate layer 3 having a thickness of 40 μm to 70 μm is formed, the first information storage layer 2 and the second information storage layer 4 can be recorded and reproduced independently. Can be. In the case of a wavelength of 405 nm and NA = 0.85, if the intermediate layer 3 having a thickness of 20 μm to 35 μm is formed, the first information storage layer 2 and the second information storage layer 4 are recorded independently. Can be played. This intermediate layer 3 is made of, for example, a resin material.
[0018]
As described above, after the first information storage layer 2 and the second information storage layer 4 are separately formed in the vacuum film forming apparatus, the first and second substrates 1 and 5 are separated. The substrate is taken out into the air, and the first and second substrates 1 and 5 are bonded together with the intermediate layer 3 made of an adhesive with the first information storage layer 2 and the second information storage layer 4 facing each other. When forming the intermediate layer 3, application, pressurization, heating or light irradiation is performed.
In the method of the present invention, there are a plurality of manufacturing methods for completing a single two-layer phase-change optical information recording medium. The first method is to form a protection film (not shown) on each of the information storage layers 2 and 4 formed on the surfaces of the first and second substrates 1 and 5, and then to first store the second information storage layer. The layer 4 is initialized, and then the second substrate 5 is bonded to the first substrate 1 with the second information storage layer 4 facing the first information storage layer 2 with the intermediate layer 3 interposed. After that, the first information storage layer 2 is initialized. The second method is to initialize the second information storage layer 4 without first forming a protective film on each of the information storage layers 2 and 4 formed on the surfaces of the first and second substrates 1 and 5, respectively. Then, the second substrate 5 is bonded to the first substrate 1 with the first information storage layer 2 facing the second information storage layer 4 with the intermediate layer 3 interposed. After that, the first information storage layer 2 is initialized. In this case, it is preferable that the protective layer be made of the same material as the intermediate layer 3 optically.
[0019]
When the second information storage layer 4 is initialized, whether or not to provide a protective film made of resin on the third dielectric layer 41 has almost no influence on optical characteristics. If the resin protective film is not provided, the conditions such as the linear velocity and laser power for initialization become narrower, but the thickness of the second reflective layer 44 is large, and the heat generated by the irradiation of the laser light is sufficiently radiated. Therefore, even if the recording layer is irradiated with the high-power initialization laser beam, the recording layer will not be thermally damaged. A conventional initialization device used when initializing a DVD-RW comprising a single layer of a phase-change type storage layer can also be initialized in substantially the same processing time.
[0020]
On the other hand, the first information storage layer 2 is difficult to dissipate heat because the first phase-change recording layer 22 and the first reflection layer 24 are as thin as 10 nm or less, and are susceptible to thermal damage during initialization. Therefore, unless a protective film made of resin is provided on the side opposite to the direction in which the initialization laser beam is incident, the first phase-change type recording layer 22 scatters or cannot be initialized at all, and the initialization is performed uniformly. Difficult to do. For this reason, after initializing the second information storage layer 4, it is bonded to the first information storage layer 2 to form a resin intermediate layer 3, and thereafter, the first information storage layer 2 (first When the phase-change recording layer 22) is initialized, the first phase-change recording layer 22 can be uniformly initialized without causing thermal damage.
[0021]
<Example>
Next, a specific example in which a phase change recording film made of (SbTe) Ge is used as the first and second phase change recording layers 22 and 42 will be described. FIG. 3 is a flowchart showing a schematic flow of the manufacturing method.
First, the second substrate 5 with the second information storage layer 4 is manufactured. That is, a second reflective layer 44 and a fourth dielectric layer are formed on a second substrate 5 made of polycarbonate resin having a thickness of 0.6 mm and provided with a pre-groove 1a having a track pitch of 0.74 μm and a groove depth of 30 nm. The body layer 43, the second phase-change recording layer 42, and the third dielectric layer 41 were formed by sputtering in this order after the inside of the sputtering apparatus was evacuated to a degree of vacuum of 1 × 10 ⁻⁶ Torr or less. . The width of the groove and land of the second substrate 5 is opposite to that of the first substrate 1, and the width of the groove and land becomes the same as that of the first substrate 1 when viewed from the light incident direction L1.
[0022]
At this time, the second reflective layer 44 is formed to a thickness of 200 nm by direct current sputtering of Ag ₉₈ Pd ₁ Cu ₁ .
The fourth dielectric layer _43, ZnS-SiO 2: a (80 20 mol%) and the high-frequency sputtering is formed with a thickness of 25 nm.
The second phase change type recording layer 42 is formed to a thickness of 13 nm by direct current sputtering of Ge ₆ Sb ₇₁ Te ₂₃ (Sb / Te = 3.1).
[0023]
The third dielectric layer 41 is formed to a thickness of 85 nm by high frequency sputtering of ZnS—SiO ₂ (80:20 mol%) with Ar gas. Thus, the second information storage layer 4 is formed (see FIG. 3A).
Thereafter, a laser beam L1 (linear velocity 4 m / s, laser power 400 mW, feed pitch 40 μm / rotation) is applied from the third dielectric layer 41 side by an initialization device (Shibasoku LK220 wavelength 820 nm, NA = 0.35). Irradiation changes the phase from an amorphous state to a crystalline state (see FIG. 3A). Thereby, the second phase change type recording layer 42 can be uniformly crystallized.
[0024]
Next, similarly to the second substrate 5, the first substrate 1 made of a polycarbonate resin having a thickness of 0.6 mm and provided with a pre-groove 1a having a track pitch of 0.74 μm and a groove depth of 30 nm is formed on the first substrate 1. As the information storage layer 2 of the first embodiment, a first electrically conductive layer 21, a first phase-change recording layer 22, a second dielectric layer 23, a first reflective layer 24, and a high refractive index layer 25 are formed by vacuum forming. After the inside of the film apparatus was evacuated to a degree of vacuum of 1 × 10 ⁻⁶ Torr or less, films were formed by sputtering in this order.
At this time, ZnS—SiO ₂ (80:20 mol%) is formed with a thickness of 66 nm as the first dielectric layer 21 by high frequency sputtering with Ar gas.
Next, the first phase-change recording layer 22 is formed with a thickness of 5 nm by direct current sputtering of Ge ₈ Sb ₇₅ Te ₁₇ (Sb / Te = 4.4).
[0025]
The second dielectric layer 23 is formed to a thickness of 15 nm by high-frequency sputtering of ZnS-SiO ₂ (80:20 mol%).
The first reflective layer 24 is formed to a thickness of 8 nm by direct current sputtering of Ag ₉₈ Pd ₁ Cu ₁ .
Further, the high refractive index layer 25 is formed of ZnS—SiO ₂ (80:20 mol%) (refractive index n = 2.3, k = 0 at a wavelength of 650 nm) with a thickness of 66 nm by high frequency sputtering. Thus, the first information storage layer 2 is formed.
Thereafter, an ultraviolet curable resin (Dainippon Ink EX8210) is applied on the second information storage layer 4 by spin coating, and then the high refractive index layer 25 of the first information storage layer 2 and the second information storage are applied. The third dielectric layer 41 of the layer 4 is bonded so as to be opposed to the first substrate 1, and the first substrate 1 and the second substrate 5 are bonded by irradiating ultraviolet rays from the first substrate 1 side and hardening. The thickness of the resin protective film as the intermediate layer 3 was 60 μm (see FIG. 3B).
[0026]
Next, the first information storage layer 2 (first phase-change type recording layer 22) is initialized by a laser beam L2 (from the first substrate 1 side) using an initialization device (Shibasoku LK220, wavelength 820 nm, NA = 0.35). Irradiation was performed at a linear velocity of 5 m / s, a laser power of 400 mW, and a feed pitch of 2 μm / rotation to change the phase from an amorphous state to a crystalline state (see FIG. 3C). Thereby, the first phase change type recording layer 22 can be initialized uniformly. Thus, a two-layer optical disc is completed.
Next, in order to evaluate the recording / reproducing characteristics, recording was performed on the groove of the first phase-change recording layer 22 from the first substrate 1 side. The groove is convex when viewed from the direction of incidence of the laser beam. The recording conditions are as follows.
The linear velocity is 3.5 m / s, the recording laser wavelength is 650 nm, the NA of the objective lens is 0.6, the peak power is 18.0 mW, and the bias power is 8.0 mW. The 8-17 modulated signal was recorded, and the jitter which was a value obtained by dividing the standard deviation σ by the window width Tw was measured. The first jitter was 10.5%. Rewriting was also possible, and the jitter after 10 times was 11.2%.
[0027]
Next, recording was performed on the groove of the second phase change recording layer 42 from the first substrate 1 side. The peak power is 28.0 mW and the bias power is 14.0 mW. The 8-17 modulated signal was recorded, and the jitter which was a value obtained by dividing the standard deviation σ by the window width Tw was measured. The first jitter was 9.3%. Rewriting was also possible, and the jitter after 10 times was 10.0%.
As described above, the first information storage layer 2 (the first phase change type recording layer 22) and the second information storage layer (the second phase change type recording layer 42) can both be uniformly initialized and have a good quality. Showed jitter. Here, the good jitter is a range of 15% or less at which the system breaks down, and a range of 12% or less in consideration of a margin.
[0028]
【The invention's effect】
As described above, according to the method for manufacturing an optical information recording medium of the present invention, the following excellent functions and effects can be exhibited.
A plurality of recording layers can be uniformly initialized in a short time by a conventional initialization device. Therefore, it is possible to obtain a multilayer optical information recording medium having a large capacity and excellent recording and reproducing characteristics.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an optical information recording medium of the present invention.
FIG. 2 is a configuration diagram showing details of the optical information recording medium shown in FIG. 1;
FIG. 3 is a flowchart showing a schematic flow of a method for manufacturing an optical information recording medium of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate, 2 ... 1st information storage layer, 3 ... intermediate | middle layer, 4 ... 2nd information storage layer, 5 ... 2nd board | substrate.

Claims (1)

A first step of preparing a light-transmissive first substrate on which a first information storage layer is formed in advance and a second substrate on which a second information storage layer is formed;
A second step of irradiating a first laser beam from above the first information storage layer to initialize the first information storage layer;
A third step of applying an optically separating intermediate layer made of an adhesive on the first information storage layer;
A fourth step of joining the first substrate and the second substrate via the intermediate layer with the second information storage layer facing the first information storage layer;
A fifth step of irradiating a second laser beam from the first substrate side to initialize the second information storage layer;
A method for manufacturing an optical information recording medium, comprising:

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