JP2004241055A - Optical recording medium and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to prevent the occurrence of corrosion in the outer peripheral portion and to suppress the size of a recording failure area in the outer peripheral portion.
In an optical recording medium, at least a mask is applied to an outer peripheral portion of a substrate, a reflective layer is formed on one principal surface of the masked substrate, and a reflective layer is formed on the reflective layer. The applied mask is removed, a lower dielectric layer 4, a recording layer 5, and an upper dielectric layer 6 are sequentially formed, and a protective layer 7 is formed on the upper dielectric layer 6. This can prevent the reflective layer 3 from being exposed to the air at the outer peripheral portion, and also allows the lower dielectric layer 4, the recording layer 5, and the upper dielectric layer 6 to be formed without reflecting the sputtering particles by the outer peripheral mask. 3 can be formed.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium and a method for manufacturing the same, and more particularly to an optical recording medium on which information signals are recorded and reproduced by irradiating a laser beam from a side provided with a protective layer for protecting an information signal portion. It is suitable for application.
[0002]
[Prior art]
2. Description of the Related Art In recent years, bonded optical discs such as DVDs (Digital Versatile Discs) have become widespread. This bonded optical disk has an advantage that a higher recording density can be achieved as compared with a single-plate optical disk such as a CD (Compact Disc).
[0003]
FIG. 10 shows an example of the configuration of a DVD-RW (Digital Versatile Disc-ReWritable) as a practical example of a bonded optical disk. As shown in FIG. 10, the DVD-RW includes a substrate 101 on which a dielectric layer 102, a recording layer 103, a dielectric layer 104, and a reflective layer 105 are sequentially stacked on one main surface, and a reflective layer 112 on one main surface. Is formed by bonding the substrate 111 formed in the above with an adhesive layer 120. Then, the recording layer 103 is irradiated with laser light used for recording / reproduction from the substrate 101 side.
[0004]
The specification of the DVD-RW is shown below.
3.49m / sec linear velocity
Recording bit length 0.267μm / bit
Track pitch 0.74μm
Laser light wavelength 650nm
Data transfer rate 11Mbps
4.7 GB storage capacity
[0005]
In recent years, it has been desired to realize a larger capacity and a higher transfer rate than the DVD described above. To meet this demand, it is necessary to reduce the spot size of the recording laser and increase the recording linear velocity.
[0006]
Therefore, as a specific method of reducing the spot size of the recording laser, a method of shortening the laser wavelength and a method of increasing the numerical aperture of the objective lens have been proposed. In particular, when both the method of shortening the laser wavelength and the method of increasing the numerical aperture of the objective lens are used in combination, the spot size can be made smaller than when each is used alone. For example, if a blue-violet laser having a wavelength of about 400 nm is used as a light source and an objective lens having a high numerical aperture NA of 0.85 is used as an objective lens, further high-density recording is theoretically possible.
[0007]
Thus, it is essential to increase the value of NA / λ in order to increase the recording density of the optical recording medium. For example, in order to achieve a storage capacity of 8 GB, it is necessary that the numerical aperture NA is at least 0.7 and the laser wavelength λ is 0.68 μm or less.
[0008]
However, as the NA of the objective lens is increased, the aberration of light caused by the tilt of the disk increases, and the allowable amount of tilt (tilt) of the disk surface with respect to the optical axis of the optical pickup decreases. Would.
[0009]
Therefore, a next-generation optical recording medium has been proposed in which a light transmission layer capable of transmitting laser light is formed on an information signal portion formed on one main surface of a substrate. In this next-generation optical recording medium, recording and / or reproduction of an information signal is performed by irradiating light not from the substrate side but from the light transmission layer side formed on the information signal portion.
[0010]
FIG. 11 shows a configuration of a next-generation optical recording medium. FIG. 12 shows the size of each area of the next-generation optical recording medium. A method of manufacturing this next-generation optical recording medium will be described with reference to FIG. First, an inner peripheral mask and an outer peripheral mask are applied to the substrate 201, and the reflective layer 202 is formed on one main surface of the substrate by a sputtering method. Then, a lower dielectric layer 203, a recording layer 204, and an upper dielectric layer 205 are sequentially formed on the reflective layer 202 in the same manner as when the reflective layer 202 is formed. Thereafter, the light transmitting layer 206 is formed by bonding the light transmitting sheet on the dielectric layer 205 with an adhesive.
[0011]
As described above, when each film is formed on one main surface of the substrate by the sputtering method, masking is performed on the inner circumference and the outer circumference of the substrate so that the reflective layer and the recording layer are formed on the inner circumference and the outer circumference of the optical disk. It can be prevented from being exposed inside and corroding.
[0012]
[Problems to be solved by the invention]
However, as described above, when an optical recording medium is manufactured by applying a mask to the substrate 201, it becomes impossible to obtain a desired film thickness near the mask edge. This is because the sputter particles are blocked by the mask and the film thickness decreases.
[0013]
Due to such a decrease in film thickness, a next-generation optical recording medium that records / reproduces an information signal using a laser beam having a wavelength of 400 nm will be less than a conventional optical disc that records / reproduces an information signal using a laser beam having a wavelength of 650 nm. However, there is a problem that the recording failure area further increases in the outer peripheral portion (see FIG. 12). This is because, in the next-generation optical recording medium, signal characteristics and the like greatly change due to a change in film thickness as compared with the conventional optical recording medium.
[0014]
Accordingly, an object of the present invention is to provide a next-generation optical recording medium in which a light transmitting layer capable of transmitting laser light is formed on an information signal portion formed on one main surface of a substrate, and the occurrence of corrosion at the outer peripheral portion is improved. It is an object of the present invention to provide an optical recording medium in which the recording error is prevented and the size of the defective recording area in the outer peripheral portion is suppressed, and a method for manufacturing the same.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the first invention of the present application is directed to an optical disc in which at least a reflective layer, a lower dielectric layer, a recording layer, an upper dielectric layer, and a protective layer are sequentially laminated on one main surface of a substrate,
An optical recording medium characterized in that a lower dielectric layer, a recording layer, and an upper dielectric layer are laminated so as to cover an outer peripheral portion of a reflective layer.
[0016]
The second invention of the present application includes a step of applying at least a mask to an outer peripheral portion of the substrate;
Forming a reflective layer on one main surface of the masked substrate;
Removing the mask applied to the substrate on which the reflective layer is formed, a step of sequentially forming a lower dielectric layer, a recording layer, and an upper dielectric layer,
Forming a protective layer on the upper dielectric layer;
Is a method for manufacturing an optical recording medium comprising:
[0017]
In the optical recording medium configured as described above, at least a mask is applied to the outer peripheral portion of the substrate, a reflective layer is formed on one main surface of the masked substrate, and the reflective layer is applied to the substrate on which the reflective layer is formed. Remove the mask, remove the mask, and sequentially form the lower dielectric layer, recording layer, and upper dielectric layer, and form a protective layer on the upper dielectric layer. And the lower dielectric layer, the recording layer, and the upper dielectric layer can be formed on the reflective layer without blocking the sputtered particles by the outer peripheral mask.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of an optical disk according to an embodiment of the present invention.
[0019]
As shown in FIG. 1, the optical disc according to this embodiment has a configuration in which a reflective layer 3, a lower dielectric layer 4, a recording layer 5, an upper dielectric layer 6, and a light transmitting layer 7 are sequentially laminated on a substrate 2. Have. The optical disk according to the embodiment is an optical disk (for example, a Blu-ray Disc) on which information signals are recorded and reproduced by irradiating the recording layer 5 with laser light from the light transmission layer 7 side.
[0020]
In the optical disc according to this embodiment, the track pitch P of the guide groove, the skew of the substrate 2, the numerical aperture NA of the optical pickup used for reproducing and / or recording the information signal, and the reproduction and / or recording of the information signal. By setting the wavelength λ of the laser beam to be used and the thickness t of the light transmitting layer 7 to satisfy the following relational expressions (1) to (4), a recording capacity of 8 GB or more can be realized.
P ≦ 0.64 (μm) (1)
Θ ≦ ± 84.115 (λ / NA ³ / T) (2)
λ ≦ 0.64 (μm) (3)
NA / λ ≧ 1.20 (4)
[0021]
Here, the wavelength λ is selected from 400 nm to 410 nm, the numerical aperture NA is selected from 0.84 to 0.86, and the data bit length is selected from 0.1035 μm to 0.12 μm. For example, the wavelength λ is set to 405 nm, the numerical aperture NA is set to 0.85, the data bit length is set to 0.12 μm, and the track pitch is set to 0.32 μm.
[0022]
When the numerical aperture NA is 0.84 or less and the wavelength λ is 410 nm or more, the spot diameter d (d∝λ / NA) becomes larger than the desired diameter, and the recording capacity of 8 GB or more is reduced. The high recording density that can be achieved cannot be realized. On the other hand, when the numerical aperture NA is 0.86 or more and the wavelength λ is 400 nm or less, the light transmission layer 7 is further provided to secure an allowable amount (tilt margin) of the inclination between the recording surface and the optical axis. Since it is necessary to reduce the thickness, it is difficult to keep the thickness error of the light transmitting layer 7 within an allowable range. That is, it becomes difficult to maintain signal quality.
[0023]
FIG. 2 is a sectional view of the optical disc according to the embodiment. As shown in FIG. 2, the optical disk according to this embodiment has a lower dielectric layer 4, a recording layer 5, an upper dielectric layer 6, a light transmission The layers 7 are sequentially stacked.
[0024]
The substrate 2 has an annular shape with a center hole (not shown) formed in the center. On one main surface of the substrate 2 on which the reflective layer 3 is formed, an uneven portion (not shown) serving as a guide groove for guiding an optical spot when recording and reproducing information is formed. The laser beam can be moved to an arbitrary position on the disk by using the groove as a guide. Various shapes such as a spiral shape, a concentric shape, and a pit row can be applied to the shape of the groove. The diameter of the substrate 2 is selected to be, for example, 120 mm. The thickness of the substrate 2 is selected in consideration of rigidity, preferably from 0.3 mm to 1.3 mm, more preferably from 0.6 mm to 1.3 mm, for example, 1.1 mm. In consideration of diverting production equipment such as a CD, the thickness of the substrate 2 is preferably about 1.2 mm.
[0025]
If the thickness of the substrate 2 is smaller than 0.3 mm, the strength of the optical disk 1 is reduced or the optical disk 1 is easily warped. Conversely, if the thickness is larger than 1.3 mm, the thickness of the optical disk 1 becomes larger than 1.2 mm for CDs and DVDs. Therefore, there is a possibility that the same disk tray cannot be shared when commercializing drive devices corresponding to all of them. .
[0026]
As a material of the substrate 2, for example, a plastic material such as a polycarbonate resin, a polyolefin resin, or an acrylic resin, or glass is used. Polycarbonate resins and polyolefin-based resins have the advantage of being heat-resistant and easy to mold at the time of melt molding, having little deterioration, and having excellent mechanical properties. Preferably, it is used. In consideration of cost, it is preferable to use a plastic material as the material of the substrate 2. For the production, an injection molding method (injection method) or a photopolymer (2P method: Photo Polymerization) using an ultraviolet curable resin can be used. Other than this, any method can be used as long as it can obtain a desired shape (for example, a disk shape having a thickness of 1.1 mm and a diameter of 120 mm) and optically sufficient substrate surface smoothness. Further, in the optical disc according to the embodiment, since a laser for recording and reproduction is incident from the light transmission layer 7, a non-transparent material such as a metal can be used as the material of the substrate 2.
[0027]
The material of the reflection layer 3 is selected in consideration of, for example, the reflection function and heat conduction of the reflection layer 3. That is, it has a reflection function with respect to the wavelength of the laser beam used for recording and reproduction, and has a thermal conductivity of, for example, 4.0 × 10 ^-2 ~ 4.5 × 10 ² J / m · K · s (4.0 × 10 ^-4 ４4.5 J / cm ・ K ・ s) selected from metal elements, metalloid elements, and compounds or mixtures thereof. Specifically, as a material of the reflection layer 3, a simple substance such as Al, Ag, Au, Ni, Cr, Ti, Pd, Co, Si, Ta, W, Mo, or Ge, or a simple substance of these simple substances is used. Alloys can be mentioned. In consideration of practicality, Al-based, Ag-based, Au-based, Si-based, or Ge-based materials are preferable. When an alloy is used as the material of the reflective layer 3, for example, AlCu, AlTi, AlCr, AlCo, AlMgSi, AgPdCu, AgPdTi, AgCuTi, AgPdCa, AgPdMg, AgPdFe, Ag, or SiB is preferable.
[0028]
The thickness of the reflective layer 3 is preferably selected to be 80 nm or more and 140 nm or less, for example, 100 nm. If the thickness of the reflective layer 3 is less than 80 nm, the heat generated in the recording layer 5 cannot be sufficiently diffused, the thermal cooling becomes insufficient, and the jitter characteristic deteriorates due to the reproduction power at the time of reproduction. On the other hand, if the thickness of the reflective layer 3 is larger than 140 nm, the thermal characteristics and the optical characteristics will not be affected, but mechanical stress such as skew will be affected by the stress generated in the reflective layer 3. In this case, desired characteristics cannot be obtained.
[0029]
The thickness of the upper dielectric layer 6 is selected to be, for example, about 40 to 140 nm. By selecting the thickness of the upper dielectric layer 6 within this range, good recording and reproducing characteristics can be secured when recording and reproducing are performed using a laser beam having a wavelength of 400 nm. Preferably, the upper dielectric layer 6 is formed in two or three chambers. By forming the upper dielectric layer 6 in this manner, the tact time during film formation can be improved.
[0030]
The material of the lower dielectric layer 4 and the upper dielectric layer 6 is desirably a material that does not absorb the wavelength of the recording / reproducing laser. Specifically, the value of the extinction coefficient k is 0 <k ≦ 0. Preferably, the material satisfies 3. Such materials include, for example, ZnS-SiO ₂ Mixtures (especially a molar ratio of about 4: 1) can be mentioned. However, ZnS-SiO ₂ In addition to the mixture, materials conventionally used for optical recording media can be used as the material for the lower dielectric layer 4 and the upper dielectric layer 6.
[0031]
For example, nitrides, oxides, carbides, fluorides, and sulfides of elements such as metals and metalloids such as Al, Si, Ta, Ti, Zr, Nb, Mg, B, Zn, Pb, Ca, La, and Ge , A layer composed of a nitride oxide, a nitrided carbide, an oxycarbide, and the like, and a material containing these as a main component. Specifically, AlN _X (0.5 ≦ x ≦ 1), especially AlN, Al ₂ O _3-X (0 ≦ x ≦ 1), especially Al ₂ O ₃ , Si ₃ N _4-X (0 ≦ x ≦ 1) In particular, Si ₃ N ₄ , SiO _X (1 ≦ x ≦ 2), especially SiO ₂ , SiO, MgO, Y ₂ O ₃ , MgAl ₂ O ₄ , TiO _X (1 ≦ x ≦ 2), especially TiO ₂ , BaTiO ₃ , StTiO ₃ , Ta ₂ O _5-X (0 ≦ x ≦ 1), especially Ta ₂ O ₅ , GeO _X (1 ≦ x ≦ 2), SiC, ZnS, PbS, Ge-N, Ge-NO, Si-NO, CaF ₂ , LaF, MgF ₂ , NaF, ThF ₄ Etc. can be used. Further, a material containing these materials as main components may be used. Alternatively, a mixture of these materials, for example AlN-SiO ₂ Or the like may be used.
[0032]
Further, the lower dielectric layer 4 and the upper dielectric layer 6 may be configured by laminating two or more dielectric layers. FIG. 3 shows an example of the configuration of the lower dielectric layer 4 and the upper dielectric layer 6 formed by laminating two dielectric layers. The lower dielectric layer 4 has a configuration in which a second lower dielectric layer 11 and a first lower dielectric layer 12 are sequentially stacked on the reflective layer 3. The upper dielectric layer 6 has a configuration in which a first upper dielectric layer 13 and a second upper dielectric layer 14 are sequentially laminated on the recording layer 5. The second lower dielectric layer 11 and the second upper dielectric layer 14 are made of Si ₃ N ₄ Consists of The first lower dielectric layer 12 and the first upper dielectric layer are made of ZnS-SiO ₂ A mixture, preferably ZnS-SiO with a molar ratio of about 4: 1 ₂ Consisting of a mixture
[0033]
The thickness of the second lower dielectric layer 11 is preferably selected from 8 nm or more and 14 nm or less, for example, 10 nm. If the thickness of the second lower dielectric layer 4 is less than 8 nm, the material of the first lower dielectric layer 12 will diffuse sulfur (S), thereby corroding the reflective layer 3. On the other hand, if the thickness of the second lower dielectric layer 11 is larger than 14 nm, the reflectivity decreases and desired signal characteristics cannot be obtained.
[0034]
The thickness of the first lower dielectric layer 12 is preferably selected from 4 nm or more and 10 nm or less, for example, 6 nm. If the thickness of the first lower dielectric layer 12 is less than 4 nm, it becomes difficult to form the first lower dielectric layer 12 having a uniform thickness. On the other hand, if it is larger than 10 nm, the reflectance is reduced and desired signal characteristics cannot be obtained.
[0035]
The thickness of the first upper dielectric layer 13 is preferably selected from 4 nm to 12 nm, for example, 6 nm. If the thickness of the first upper dielectric layer 13 is less than 4 nm, it becomes difficult to form the first upper dielectric layer 13 having a uniform thickness. On the other hand, when the thickness of the first upper dielectric layer 13 is larger than 12 nm, heat is easily stored in the recording layer 5, and the reproduction stability is deteriorated.
[0036]
The thickness of the second upper dielectric layer 14 is preferably selected from 36 nm or more and 46 nm or less, for example, 42 nm. When the thickness of the second upper dielectric layer 14 is selected to be less than 36 nm, the reflectance increases, and when it is selected to be larger than 46 nm, the reflectance decreases.
[0037]
The recording layer 5 is formed of a phase change material that undergoes a reversible state change upon irradiation with a laser beam. As the phase change material, a material which causes a reversible phase change between an amorphous state and a crystalline state is preferable, and any known materials such as a chalcogen compound or a simple chalcogen can be used. For example, Te, Se, Ge-Sb-Te, Ge-In-Sb-Te, Ge-Te, Sb-Te, In-Sb-Te, Ag-In-Sb-Te, Ag-Ge-Sb -Te, Au-In-Sb-Te, Ge-Sb-Te-Pd, Ge-Sb-Te-Se, In-Sb-Se, Bi-Te, Bi-Se, Sb-Se, Ge-Sb-Te A system containing -Bi, Ge-Sb-Te-Co, Ge-Sb-Te-Au, or a system in which a gas additive such as nitrogen or oxygen is introduced into these systems. Among them, particularly preferred are those containing an Sb-Te system as a main component. It is also preferable to add an arbitrary element such as Se or Pd, or Ge or In to this.
[0038]
The material of the recording layer 5 is not limited to a phase change material, but may be a magneto-optical recording material such as a Tb-Fe system, a Te-FeCo system, a Gd-Fe system, a Gd-FeCo system, or an organic dye. May be used.
[0039]
When a phase change recording layer is used as the recording layer 5, the phase change between the amorphous state and the crystalline state can be reversibly performed by the intensity of the laser beam. Utilizing it, it is possible to perform operations such as recording, reproduction, erasing, and overwriting. Generally, after film formation, crystallization (generally referred to as initialization) is performed once, and recording and reproduction are performed. Note that the recording layer 5 may be composed of two or more continuous different layers (any one of a material, a composition, and a complex refractive index is different).
[0040]
The thickness of the recording layer 5 is preferably selected from 6 nm to 16 nm, for example, 10 nm. If the thickness of the recording layer 5 is selected to be 6 nm or less, it will be difficult to obtain sufficient reproduction durability. On the other hand, if it is larger than 16 nm, the recording sensitivity is deteriorated, and it becomes difficult to record the information signal.
[0041]
The light transmitting layer 7 includes a light transmitting sheet (film) having a planar annular shape, and an adhesive layer (both not shown) for bonding the light transmitting sheet to the upper dielectric layer 6. . The adhesive layer is made of, for example, an ultraviolet curable resin or a pressure-sensitive adhesive (PSA: Pressure Sensitive Adhesive).
[0042]
The thickness of the light transmission layer 7 is preferably set to 10 μm to 177 μm, considering that the light transmission layer 7 corresponds to a current red laser to a blue laser expected to be widely used in the future. Generally, there is a correlation between the disc skew margin 光源, the light source wavelength λ of the recording / reproducing optical pickup, its numerical aperture NA, and the thickness t of the light transmission protective layer of the disc, and its playability has been demonstrated sufficiently for practical use. The relationship between these parameters and Θ based on an example of a compact disc (CD) is shown in Japanese Patent Application Laid-Open No. 3-225650. According to this, Θ ≦ ± 84.115 (λ / NA ³ / T). Here, considering a specific limit value of the skew margin 実 際 when the disks are actually mass-produced, it is appropriate to set the skew margin to 0.4 °. This is because, when considering mass production, if the size is smaller than this, the yield decreases and the cost increases. For example, it is 0.6 ° for a CD and 0.4 ° for a DVD. Therefore, when Θ = 0.4 °, the wavelength of the laser is shortened and the N.V. A. By calculating how much the thickness of the light transmitting layer 7 should be set by the conversion, first, when λ = 0.65 μm, the NA is required to be 0.78 or more. Further, if the wavelength is shortened in the future and λ = 0.4 μm, t = 177 μm. The lower limit of the thickness of the light transmitting layer 7 is determined by the protection function of the light transmitting layer 7 for protecting the recording layer 5, and is preferably 10 μm or more in consideration of the reliability and the influence of the collision of the second group lens.
[0043]
The light-transmitting sheet is preferably made of a material having a low absorptivity to laser light used for recording / reproducing, and specifically, a material having a transmittance of 90% or more. Specifically, the light transmissive sheet is made of, for example, a polycarbonate resin material or a polyolefin resin.
[0044]
For example, when polycarbonate (PC) is used as the material of the light transmissive sheet, the thermal expansion coefficient is 7.0 × 10 ^-5 Degree, flexural modulus is 2.4 × 10 ⁴ About a few materials are used. When a polyolefin resin (for example, ZEONEX (registered trademark)) is used as the material of the light transmitting sheet, the coefficient of thermal expansion is 6.0 × 10 6. ^-5 Degree, flexural modulus 2.3 × 10 ⁴ About a few materials are used.
[0045]
Further, the thickness of the light transmitting sheet is preferably selected to be 0.3 mm or less, and more preferably selected from the range of 3 to 177 μm. For example, the thickness is selected so that the total thickness with the adhesive layer is, for example, 100 μm. By combining such a thin light transmitting layer 7 with an objective lens having a high NA of about 0.85, high density recording can be realized.
[0046]
The light transmissive sheet according to the embodiment is, for example, a material such as a polycarbonate resin is put into an extruder, and is melted at a temperature of 250 to 300 ° C. using a heater (not shown), and a plurality of cooling rolls are formed. It is formed by shaping into a sheet shape and cutting it into a shape conforming to the substrate 2.
[0047]
Further, a protective layer made of an organic or inorganic material may be further formed for the purpose of preventing dust from adhering to or scratching the surface of the light transmitting protective layer. Also in this case, it is preferable to use a material having almost no absorption capacity for the wavelength of the laser for recording and reproduction.
[0048]
For example, when the thickness t of the light transmitting layer is set to 10 μmμ177 μm and the variation in the thickness of the light transmitting layer is set to Δt, the NA and the wavelength of the optical system that reproduces and / or records information on the optical recording medium are set. If the relationship expressed by the following equation is established between λ, the storage capacity can be set to 8 GB, and a high recording capacity can be achieved by using a recording and reproducing apparatus similar to a conventional recording and reproducing apparatus. It is possible.
Δt = ± 5.26 (λ / NA ⁴ )
[0049]
Next, a method for manufacturing an optical disk according to an embodiment of the present invention will be described.
[0050]
Here, a sputtering device used for manufacturing the optical disc 1 according to the embodiment will be described. This sputtering apparatus is a single wafer type stationary facing sputtering apparatus that can rotate on a substrate.
[0051]
FIG. 4 shows a sputtering apparatus used for manufacturing the optical disc 1. As shown in FIG. 4, the sputtering apparatus includes a vacuum chamber 21 serving as a stratification chamber, a vacuum controller 22 for controlling a vacuum state in the vacuum chamber 21, a DC high-voltage power supply for plasma discharge 23, and a DC high-voltage power supply for plasma discharge. A sputtering cathode unit 25 connected through a power supply line 23 and a power supply line 24, a pallet 26 opposed to the sputtering cathode unit 25 at a predetermined distance, and a sputtering gas such as an inert gas such as Ar or a reactive gas. It has a sputter gas supply unit 27 for supplying it into the vacuum chamber 21.
[0052]
The sputtering cathode portion 25 is provided on a target 28 functioning as a negative electrode, a backing plate 29 configured to fix the target 28, and a surface of the backing plate 29 opposite to the surface to which the target 28 is fixed. Provided with a magnet system 30.
[0053]
Further, a pair of electrodes is constituted by a pallet 26 functioning as a positive electrode and a target 28 functioning as a negative electrode. On the pallet 26, the substrate 2, which is a layered body, is mounted with the disk base 33 interposed therebetween so as to face the sputtering cathode section 25. At this time, the inner and outer peripheral portions of the substrate 2 are covered by the inner and outer peripheral masks 31 and 32.
[0054]
Further, on the surface of the pallet 26 opposite to the surface on which the disk base 33 is mounted, the pallet 26 is rotated in the in-plane direction of the substrate 2, whereby a substrate rotation driving unit 34 for rotating the substrate 2 rotates. It is provided as possible.
[0055]
In the sputtering apparatus 20, the substrate 2 as a layered body having a planar annular shape as shown in FIG. 5A and the target 28 made of a disk-shaped layered material as shown in FIG. As shown in (2), the center O of the substrate 2 and the center O 'of the target 28 are arranged so as to substantially coincide with each other in their planar positional relationship. In addition, the substrate 2 is configured to be able to rotate around its center O by the substrate rotation drive unit 34 shown in FIG.
[0056]
As described above, the sputtering apparatus 20 used for manufacturing the optical disc in this embodiment is configured.
[0057]
In the following manufacturing process, since the sputter devices used for forming each layer have the same configuration, the same reference numerals are used as in the DC sputtering device 20 described above.
[0058]
First, the substrate 2 is carried into a first sputtering apparatus 20 on which a target 28 made of, for example, AgM (M: additive) is installed, and is fixed to a pallet 26. At this time, at least the outer peripheral mask 32 of the inner peripheral mask 31 and the outer peripheral mask 32 is applied to the substrate 2. Next, a predetermined pressure (for example, 1.0 × 10 ^-5 Vacuum until Pa). Next, for example, Ar gas is introduced into the vacuum chamber 21, and a predetermined atmosphere (for example, 1.0 to 3.0 × 10 ⁰ Pa), the applied voltage is appropriately set to 1 to 3 kWh, and sputtering is performed to form a reflective layer 3 made of, for example, an Ag-based alloy on one main surface of the substrate 2.
[0059]
Next, the substrate 2 is carried into a second sputtering apparatus 20 on which a target made of, for example, Si is installed, and is fixed to a pallet 26. At this time, at least the outer mask 32 of the inner mask 31 and the outer mask 32 is not applied to the substrate 2. Then, a predetermined pressure (for example, 1.0 × 10 ^-5 Vacuum until Pa). Next, for example, Ar gas and nitrogen gas are appropriately introduced into the vacuum chamber 21, and a predetermined atmosphere (for example, 1.0 to 3.0 × 10 ⁰ Pa), and by appropriately setting the applied voltage to 1 to 3 kWh and performing sputtering, for example, Si ₃ N ₄ A second lower dielectric layer 11 made of the following is formed on the reflective layer 3.
[0060]
Next, the substrate 2 is, for example, ZnS-SiO ₂ The mixture is carried into the third sputtering apparatus 20 on which the target 28 made of the mixture is installed, and is fixed to the pallet 26. At this time, at least the outer mask 32 of the inner mask 31 and the outer mask 32 is not applied to the substrate 2. Next, a predetermined pressure (for example, 1.0 × 10 ^-5 Vacuum until Pa). After that, for example, Ar gas is appropriately introduced into the vacuum chamber 21 and a predetermined atmosphere (for example, 1.0 to 3.0 × 10 ⁰ Pa), and by appropriately setting the applied voltage to 1 to 3 kWh and performing sputtering, for example, ZnS-SiO ₂ A first lower dielectric layer made of a mixture is formed on the second lower dielectric layer.
[0061]
Next, the substrate 2 is carried into a fourth sputtering apparatus 20 provided with a target 28 made of, for example, an SbTe-based alloy, and is fixed to a pallet 26. At this time, at least the outer mask 32 of the inner mask 31 and the outer mask 32 is not applied to the substrate 2. Next, a predetermined pressure (for example, 1.0 × 10 ^-5 Vacuum until Pa). After that, for example, Ar gas is appropriately introduced into the vacuum chamber 21 and a predetermined atmosphere (for example, 1.0 to 3.0 × 10 ⁰ Pa), the recording layer 5 made of, for example, an SbTe-based alloy is formed on the first lower dielectric layer 12 by appropriately setting the applied voltage to 1 to 3 kWh and performing sputtering.
[0062]
Next, the substrate 2 is, for example, ZnS-SiO ₂ The mixture is carried into the fourth sputtering apparatus 20 on which the target 28 made of the mixture is installed, and is fixed to the pallet 26. At this time, at least the outer mask 32 of the inner mask 31 and the outer mask 32 is not applied to the substrate 2. Next, a predetermined pressure in the vacuum chamber 21 (for example, 1.0 × 10 ^-5 Vacuum until Pa). After that, for example, Ar gas is appropriately introduced into the vacuum chamber 21 and a predetermined atmosphere (for example, 1.0 to 3.0 × 10 ⁰ Pa), and by appropriately setting the applied voltage to 1 to 3 kWh and performing sputtering, for example, ZnS-SiO ₂ A first upper dielectric layer 13 made of a mixture is formed on the recording layer 5.
[0063]
Next, the substrate 2 is carried into a sixth sputtering apparatus provided with a target made of, for example, Si and fixed to the pallet 26. At this time, at least the outer mask 32 of the inner mask 31 and the outer mask 32 is not applied to the substrate 2. Then, a predetermined pressure (for example, 1.0 × 10 ^-5 Vacuum until Pa). Next, for example, Ar gas and nitrogen gas are appropriately introduced into the vacuum chamber 21, and a predetermined atmosphere (for example, 1.0 to 3.0 × 10 ⁰ Pa), and by appropriately setting the applied voltage to 1 to 3 kWh and performing sputtering, for example, Si ₃ N ₄ Is formed on the first upper dielectric layer 13.
[0064]
Thereafter, the substrate 2 is carried into a predetermined position of a bonding apparatus (not shown). Then, a planar annular light-transmitting sheet is bonded to the side on which the respective layers are formed on the substrate 2 by using a pressure-sensitive adhesive (PSA) previously uniformly applied to one main surface of the sheet. Thereby, the light transmitting layer 7 is formed so as to cover each layer formed on the substrate 2. By forming the light transmitting layer 7 in this manner, the yield can be improved and the reliability of the optical disc can be maintained.
[0065]
Thus, the optical disc 1 shown in FIG. 1 is manufactured.
[0066]
According to the embodiment of the present invention, the following effects can be obtained.
The lower dielectric layer 4, the recording layer 5, and the upper dielectric layer 6 are laminated on the reflective layer 3 formed on one main surface of the substrate 2 so as to cover the outer peripheral portion of the reflective layer 3. In this portion, the reflective layer 3 can be prevented from being exposed to the atmosphere, and the lower dielectric layer 4, the recording layer 5, and the upper dielectric layer 6 can be placed on the reflective layer 3 without the outer peripheral mask 32 blocking the sputtered particles. Can be formed. Therefore, it is possible to prevent the occurrence of corrosion in the outer peripheral portion and to suppress the size of the recording failure area in the outer peripheral portion.
[0067]
【Example】
Next, an embodiment of the optical disk will be described.
Example 1
First, the substrate 2 is loaded into a first sputtering apparatus 20 on which a target 28 made of AgM (M: additive) is installed, and is fixed to a pallet 26. At this time, the inner peripheral mask 31 and the outer peripheral mask 32 are applied to the substrate 2. The inner diameter of the outer peripheral mask 32 is 118 mm. Next, a reflective layer 3 made of an Ag-based alloy and having a thickness of 100 nm is formed on one main surface of the substrate 2 by performing sputtering.
The film forming conditions in this sputtering process are shown below.
Degree of vacuum: 1.0 × 10 ^-5 Pa
Atmosphere: 3.0 × 10 ⁰ Pa
Input power: 3 kWh
Gas type: Ar gas
[0068]
Next, the substrate 2 is carried into the second sputtering apparatus 20 provided with the Si target, and is fixed to the pallet 26. At this time, only the inner peripheral mask 31 is applied to the substrate 2. Then, by performing sputtering, Si having a thickness of 5 nm ₃ N ₄ The second lower dielectric layer 11 made of is formed.
The film forming conditions in this sputtering process are shown below.
Degree of vacuum: 1.0 × 10 ^-5 Pa
Atmosphere: 3.0 × 10 ⁰ Pa
Input power: 3 kWh
Gas type: Ar gas and nitrogen gas
Nitrogen gas amount: 30 sccm
[0069]
Next, the substrate 2 is made of ZnS-SiO ₂ Is carried into the third sputtering apparatus 20 on which the target 28 made of is installed, and is fixed to the pallet 26. At this time, only the inner peripheral mask 31 is applied to the substrate 2. Next, ZnS—SiO having a thickness of 5 nm is formed by performing sputtering. ₂ A first lower dielectric layer 12 is formed.
The film forming conditions in this sputtering process are shown below.
Degree of vacuum: 1.0 × 10 ^-5 Pa
Atmosphere: 3.0 × 10 ⁰ Pa
Input power: 3 kWh
Gas type: Ar gas
[0070]
Next, the substrate 2 is carried into the fourth sputtering apparatus 20 on which the target 28 made of an SbTe alloy is installed, and is fixed to the pallet 26. At this time, only the inner peripheral mask 31 is applied to the substrate 2. Next, the recording layer 5 made of an SbTe alloy having a thickness of 10 nm is formed on the second lower dielectric layer 12 by sputtering.
The film forming conditions in this sputtering process are shown below.
Degree of vacuum: 1.0 × 10 ^-5 Pa
Atmosphere: 3.0 × 10 ⁰ Pa
Input power: 3 kWh
Gas type: Ar gas
[0071]
Next, the substrate 2 is made of ZnS-SiO ₂ Is carried into the fifth sputtering apparatus 20 on which the target 28 made of is installed, and is fixed to the pallet 26. At this time, only the inner peripheral mask 31 is applied to the substrate 2. Next, ZnS-SiO having a thickness of 10 nm is formed by performing sputtering. ₂ The first upper dielectric layer 13 made of is formed on the recording layer 5.
The film forming conditions in this sputtering process are shown below.
Degree of vacuum: 1.0 × 10 ^-5 Pa
Atmosphere: 3.0 × 10 ⁰ Pa
Input power: 3 kWh
Gas type: Ar gas
[0072]
Next, the substrate 2 is carried into a sixth sputtering apparatus provided with a target 28 made of a Si target, and is fixed to a pallet 26. At this time, only the inner peripheral mask 31 is applied to the substrate 2. Next, by sputtering, Si having a thickness of 40 nm ₃ N ₄ A second upper dielectric layer 14 made of is formed on the first upper dielectric layer 13.
The film forming conditions in this sputtering process are shown below.
Degree of vacuum: 1.0 × 10 ^-5 Pa
Atmosphere: 3.0 × 10 ⁰ Pa
Input power: 3 kWh
Gas type: Ar gas and nitrogen gas
Nitrogen gas amount: 30 sccm
[0073]
Thereafter, the substrate 2 is carried into a predetermined position of a bonding device (not shown). Then, a light-transmitting sheet made of polycarbonate is attached to the side of the substrate 2 on which the respective layers are formed, using a pressure-sensitive adhesive (PSA) that is uniformly applied in advance on one main surface of the sheet. As a result, the light transmitting layer 7 having an outer diameter of 119 mm and a thickness of 0.1 mm is formed so as to cover each layer formed on the substrate 2.
[0074]
Example 2
In the same manner as in the first embodiment, the reflection layer 3, the second lower dielectric layer 11, the first lower dielectric layer 12, the recording layer 5, and the first upper dielectric layer 13 , A second upper dielectric layer 14 is sequentially laminated.
[0075]
Thereafter, an ultraviolet curable resin is dropped on the second upper dielectric layer 14 by spin coating, and is uniformly applied so as to form a 10 μm-thick film at a predetermined rotation speed. Then, a light transmissive sheet is stuck on the uniformly applied ultraviolet curing resin, and the ultraviolet curing resin is cured by irradiating ultraviolet rays. Thereby, the light transmission layer 7 is formed.
[0076]
Comparative Example 1
First, a reflection layer 3 made of an Ag alloy is formed on one main surface of the substrate 2 in the same manner as in the first embodiment. Then, the second lower dielectric layer 11 and the first lower dielectric layer 11 are formed on one main surface of the substrate 2 in the same manner as in the first embodiment except that the inner peripheral mask 31 and the outer peripheral mask 32 are applied to the substrate 2. The body layer 12, the recording layer 5, the first upper dielectric layer 13, and the second upper dielectric layer 14 are sequentially laminated.
[0077]
Comparative Example 2
First, the reflection layer 3 is laminated in the same manner as in Example 1 except that only the inner peripheral mask 31 is applied to the substrate 2. Then, in the same manner as in the first embodiment, only the inner peripheral mask 31 is applied to the substrate 2, and the second lower dielectric layer 11, the first lower dielectric layer 12, The recording layer 5, the first upper dielectric layer 13, and the second upper dielectric layer 14 are sequentially laminated.
[0078]
The present inventor recorded a signal having a recording light emission pattern shown in FIG. 6 for Example 1, Example 2, Comparative Example 1, and Comparative Example 2 created as described above. The wavelength of the laser beam used for recording was 405 nm, the NA of the lens was 0.85, and the recording bit length was 0.13 μm / bit. Then, in Example 1, Example 2, Comparative Example 1, and Comparative Example 2, the jitter value near the outer periphery was measured.
[0079]
FIG. 7 shows a measurement result of the jitter value. In FIG. 7, the horizontal axis represents the radial position, and the vertical axis represents the difference from the jitter value at each position when the jitter value at the radius of 57 mm is used as a reference (ΔJitter = Jitter at each position−Jitter at the radius of 57 mm). Is represented.
[0080]
From FIG. 7, in Comparative Example 1, the jitter value greatly deteriorates near the position where the outer peripheral mask 32 is applied, whereas in Examples 1 and 2 and Comparative Example 2, the jitter value near the position where the outer peripheral mask 32 is applied is large. It can be seen that there is no deterioration in the jitter value.
[0081]
After maintaining these samples for 400 hours in a high-temperature and high-humidity environment at a temperature of 80 ° C. and a humidity of 85%, it was observed whether or not corrosion occurred on the outer peripheral portion. As a result, in Examples 1 and 2, no corrosion was observed on the outer peripheral portion. In Comparative Example 1, no corrosion was observed on the outer peripheral portion. However, in Comparative Example 2, corrosion occurred on the outer peripheral portion.
[0082]
For this reason, without the mask as in Comparative Example 2, corrosion occurs although the signal characteristics are good, but with the mask as in Comparative Example 1, the corrosion disappears, but the signal characteristics near the outer periphery are deteriorated. You can see that.
[0083]
As described above, the embodiments of the present invention have been specifically described. However, the present invention is not limited to the above embodiments, and various modifications based on the technical idea of the present invention are possible.
[0084]
For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as needed.
[0085]
In the above-described embodiment, an example in which the present invention is applied to an optical disc having a single recording layer has been described. The invention may be applied.
[0086]
FIG. 8 shows an example in which the present invention is applied to an optical disk having two recording layers. Hereinafter, an example of a method for manufacturing the optical disc will be described with reference to FIG. First, the reflection layer 42, the lower dielectric layer 43, the recording layer 44, the upper dielectric layer 45, and the light transmission layer 46 are sequentially laminated on the substrate 41 in the same manner as in the above-described embodiment. Then, the reflection layer 47, the lower dielectric layer 48, the recording layer 49, the upper dielectric layer 50, and the light transmission layer 51 are laminated on the light transmission layer 46 in the same manner as in the above-described embodiment. The irregularities such as lands and grooves formed on one main surface of the light transmitting layer 46 are formed, for example, by pressing a stamper against the light transmitting layer 46.
[0087]
In the method for manufacturing an optical disc according to the above-described embodiment, an example is described in which the optical disc 1 is manufactured by forming the optical disc 1 by sequentially laminating each layer on the substrate 2. It is not limited to this.
[0088]
For example, a multilayer film may be laminated on the light transmission protection layer in which the guide groove is formed, and finally a smooth support substrate may be formed. As a method of forming the groove tracks of the unevenness in the light transmitting layer, for example, an injection molding (injection) method, a photopolymer method (2P method), a method of transferring the unevenness by pressing and pressing, or the like can be used. However, since the step of forming irregularities on the light transmitting layer 7 or the step of forming a multilayer layer is not always easy, it is preferable to use the method of manufacturing an optical disk according to the above-described embodiment in consideration of mass production or the like. .
[0089]
In the above-described embodiment, the light-transmitting sheet is attached to the substrate 2 via a pressure-sensitive adhesive that has been uniformly applied to one main surface of the light-transmitting sheet in advance. Although the case of forming the light transmitting layer 7 has been described as an example, the method of forming the light transmitting layer 7 is not limited thereto.
[0090]
For example, the light transmitting layer 7 may be formed by applying an ultraviolet curable resin between one main surface of the light transmitting sheet and the second upper dielectric layer 6 and irradiating with ultraviolet light.
[0091]
Also, for example, in the above-described embodiment, a stationary facing single-wafer sputtering apparatus in which one disk substrate is opposed to one target is used as the DC sputtering apparatus, and their planar positions are used. Although the relationship is shown in FIG. 5, the present invention is not necessarily limited to the stationary facing single-wafer sputtering apparatus, and a plurality of sheets (8 in FIG. 9A) are placed on the pallet 26 as shown in FIG. 9A. 9B, a plurality of targets 28 are fixed to the vacuum chamber 21 as shown in FIG. 9B, and the plurality of substrates 2 are rotated while rotating the pallet 26 in the direction of arrow b in the positional relationship shown in FIG. 9C. It is also possible to apply the present invention to a sputtering apparatus in which a film is formed.
[0092]
In the above-described embodiment, the case where the present invention is applied to a single-plate optical disk has been described. However, it is needless to say that the present invention is also applicable to a bonded optical disk such as a DVD. Nor. Note that the thickness of the substrate of the bonded optical disk is preferably 0.3 mm or more in consideration of rigidity.
[0093]
【The invention's effect】
As described above, according to the present invention, the reflection layer can be prevented from being exposed to the air in the outer peripheral portion, and the lower dielectric layer, the recording layer, and the upper dielectric layer can be prevented without the sputtering particles being blocked by the outer peripheral mask. A body layer can be formed on the reflective layer 3. Therefore, it is possible to prevent the occurrence of corrosion in the outer peripheral portion and to suppress the size of the recording failure area in the outer peripheral portion.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a configuration of an optical disc according to an embodiment of the present invention.
FIG. 2 is a sectional view showing an optical disc according to an embodiment of the present invention.
FIG. 3 is a sectional view showing an example of a configuration of an upper dielectric layer and a lower dielectric layer of the optical disc according to the embodiment of the present invention.
FIG. 4 shows an example of a DC sputtering apparatus used for manufacturing an optical disc according to an embodiment of the present invention.
FIG. 5 is a plan view showing a substrate, a target, and their planar positional relationship according to an embodiment of the present invention.
FIG. 6 is a schematic diagram illustrating waveforms of information signals recorded in an example and a comparative example.
FIG. 7 is a graph showing a measurement result of a jitter value in an example and a comparative example.
FIG. 8 is a sectional view showing an example of a configuration of an optical disc according to a modification of the present invention.
FIG. 9 shows another example of a DC sputtering apparatus used for manufacturing an optical disc according to an embodiment of the present invention.
FIG. 10 is a sectional view showing a configuration of a DVD-RW.
FIG. 11 is a cross-sectional view illustrating a configuration of a next-generation optical recording medium.
FIG. 12 shows the size of each area of a next-generation optical recording medium.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Substrate, 3 ... Reflective layer, 4 ... Lower dielectric layer, 5 ... Recording layer, 6 ... Upper dielectric layer, 7 ... Light transmission Layer, 11: second lower dielectric layer, 12: first lower dielectric layer, 13: first upper dielectric layer, 14: second upper dielectric layer

Claims (16)

At least on one principal surface of the substrate, an optical disc in which a reflective layer, a lower dielectric layer, a recording layer, an upper dielectric layer, and a protective layer are sequentially laminated,
An optical recording medium, wherein a lower dielectric layer, a recording layer, and an upper dielectric layer are laminated so as to cover an outer peripheral portion of a reflective layer. The protective layer is configured to transmit light used for recording and reproducing information signals,
Light having a wavelength in the range of 400 nm or more and 410 nm or less is condensed by an optical system having a numerical aperture in the range of 0.84 or more and 0.86 or less, and the recording layer is irradiated from the protective layer side to obtain information. 2. The optical recording medium according to claim 1, wherein recording and reproduction of signals are performed. 2. The optical recording medium according to claim 1, wherein the reflection layer is made of a metal or a metalloid. The optical recording medium according to claim 1, wherein the reflection layer is made of an Ag-based alloy. 2. The structure according to claim 1, wherein the lower dielectric layer and the upper dielectric layer have a structure in which a dielectric layer made of a mixture of zinc sulfide and silicon oxide and a dielectric layer made of silicon nitride are sequentially laminated. The optical recording medium according to the above. 2. The optical recording medium according to claim 1, wherein the light transmitting layer comprises a light transmitting sheet and an adhesive layer for bonding the light transmitting sheet to a substrate. 7. The optical recording medium according to claim 6, wherein said adhesive layer is made of a pressure-sensitive adhesive. 7. The optical recording medium according to claim 6, wherein said adhesive layer is made of an ultraviolet curable resin. A step of applying at least a mask to an outer peripheral portion of the substrate;
Forming a reflective layer on one main surface of the substrate provided with the mask,
Removing the mask applied to the substrate on which the reflective layer is formed, forming a lower dielectric layer, a recording layer, and an upper dielectric layer sequentially;
Forming a protective layer on the upper dielectric layer. The protective layer is configured to transmit a laser beam used for recording and reproducing an information signal,
Light having a wavelength in the range of 400 nm or more and 410 nm or less is condensed by an optical system having a numerical aperture in the range of 0.84 or more and 0.86 or less, and irradiated to the information signal portion from the protective layer side. The method for manufacturing an optical recording medium according to claim 9, wherein recording and reproduction of an information signal are performed. 10. The method according to claim 9, wherein the reflection layer is made of a metal or a metalloid. 10. The method according to claim 9, wherein the reflection layer is made of an Ag-based alloy. The lower dielectric layer and the upper dielectric layer are formed by sequentially laminating a dielectric layer composed of a mixture of zinc sulfide and silicon oxide and a dielectric layer composed of silicon nitride. Item 10. The method for manufacturing an optical recording medium according to Item 9. The method for manufacturing an optical recording medium according to claim 9, wherein the light transmitting layer is formed by bonding a light transmitting sheet to the upper dielectric layer with an adhesive layer. The method according to claim 14, wherein the adhesive layer is made of a pressure-sensitive adhesive. The method for manufacturing an optical recording medium according to claim 14, wherein the adhesive layer is made of an ultraviolet curable resin.

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