JP2005209259A - Manufacturing method of optical recording medium, and optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide such a manufacturing method of an optical recording medium, that the optical recording medium using a metallic oxide as the recording layer can be manufactured at a low cost and high tact time, and to provide the optical recording medium obtained by this manufacturing method. <P>SOLUTION: By this manufacturing method, the optical recording medium having the recording layer containing the metallic oxide on a substrate is manufactured. The formation of the above recording layer has a feature such as including a metallic oxide layer forming process for applying physical etching or chemical etching after forming the metallic oxide layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical recording medium using a metal oxide for a recording layer and a method for manufacturing the same.

  Optical recording media represented by CD and DVD are manufactured by laminating a recording layer, a reflective layer, and the like on a transparent disk substrate, and information is recorded / reproduced / erased by irradiation with a laser beam. In recent years, recording density has been further improved in order to secure a capacity that can be used for HDTVs, digital VTRs, and the like. As a means for improving the recording density, it is only necessary to reduce the spot diameter of the laser beam and miniaturize the recording pattern (record mark). Recently, an optical recording medium compatible with a 405 nm short wavelength laser beam and compatible with a high NA lens. Has been developed.

  As described above, until now, the recording density of optical recording media has been basically increased by shortening the wavelength of the laser. However, in recent years, it is said that the limits are approaching the shortening of the laser wavelength and the increase of the NA of the lens, and in the future, the recording density can be dramatically increased by combining a simple short wavelength laser and a high NA lens. It is considered difficult to increase. Therefore, it is necessary to fundamentally renew the recording mechanism for the next generation high-density optical recording medium.

  Recently, an optical recording medium using a metal oxide as a recording film has been proposed (for example, see Non-Patent Documents 1 and 2). Such an optical recording medium has a recording / reproducing principle based on a completely new mechanism such as a coloring phenomenon and a uniform phenomenon, and depending on the material, it corresponds to an infrared light to an ultraviolet light laser. As expected very much. In addition, since the material is oxide-based, durability and archive characteristics are presumed to be good.

In such a recording medium, the metal oxide used for the recording film is generally formed by a pulse laser deposition (PLD) method. However, since the PLD method has problems such as high cost, low tact time, and inability to produce a large area, it is far from practical use. On the other hand, for the purpose of low cost and high tact time, formation of a metal oxide by a sputtering method has been studied. However, sputtering using a metal oxide target makes it difficult to form a metal material that contributes to coloring, and good characteristics cannot be obtained. In addition, when a metal target is used, the inside of the chamber is extremely contaminated, which is not preferable because the inside of the chamber needs to be frequently cleaned.
Takanori Aoki, 4 others, “Improvement of characteristics in blue laser compatible optical discs” J.Vac.Soc.Jpn.Vol.45, No.3,2002, p.129-132 Akio Suzuki and five others, "ZnO-based optical recording film (II) prepared by pulsed laser deposition", 38th Joint Conference on Vacuum Proceedings, p.176-179

This invention is made | formed in view of the above conventional trouble, and makes it a subject to achieve the following objectives. That is,
An object of the present invention is to provide an optical recording medium manufacturing method capable of manufacturing an optical recording medium using a metal oxide in a recording layer at low cost and high tact time, and an optical recording medium obtained by the manufacturing method. is there.

Means for solving the above problems are as follows. That is,
<1> A method for producing an optical recording medium having a recording layer containing a metal oxide on a substrate, wherein in the formation of the recording layer, physical etching or chemical etching is performed after forming the metal oxide layer. A method for producing an optical recording medium, comprising: forming a metal oxide layer.

<2> The method for producing an optical recording medium according to <1>, wherein the metal oxide layer is formed by a sputtering method.

<3> Furthermore, it has a different metal oxide layer formation process which forms the layer of a different metal oxide which is an oxide of a metal different from the metal of the metal oxide, The method for producing an optical recording medium according to <1> or <2>, wherein the metal oxide layer forming step is repeated, and the metal oxide layer and the dissimilar metal oxide layer are laminated.

<4> The method for producing an optical recording medium according to any one of <1> to <3>, wherein a time for performing the physical etching or the chemical etching is 120 to 300 seconds.

<5> An optical recording medium obtained by the method for manufacturing an optical recording medium according to any one of <1> to <4>.

  According to the present invention, it is possible to provide an optical recording medium manufacturing method capable of manufacturing an optical recording medium using a metal oxide for a recording layer at low cost and high tact time, and an optical recording medium obtained by the manufacturing method. it can.

  The method for producing an optical recording medium of the present invention is a method for producing an optical recording medium having a recording layer containing a metal oxide, and in the step of forming the recording layer, after forming the metal oxide layer, It is characterized by having a metal oxide layer forming process for performing etching or chemical etching. Hereinafter, first, the optical recording medium of the present invention manufactured by the method of manufacturing the optical recording medium of the present invention will be described in detail.

<Optical recording medium>
The optical recording medium of the present invention has at least a recording layer on a substrate, and other layers such as a light reflection layer, a barrier layer, a protective layer (light transmission layer), an underlayer, an intermediate layer, and a dielectric layer as necessary. Having a layer. Hereinafter, the substrate and each layer will be described.

[substrate]
As the substrate, various materials used as substrate materials for conventional optical recording media can be arbitrarily selected and used.
Specifically, glass; acrylic resin such as polycarbonate and polymethyl methacrylate; vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer; epoxy resin; amorphous polyolefin; polyester; metal such as aluminum; These may be used together if desired.
Among the above materials, polycarbonate and amorphous polyolefin are preferable, and polycarbonate is particularly preferable from the viewpoints of moisture resistance, dimensional stability, and low cost. Moreover, it is preferable that the thickness of a board | substrate shall be 0.5-1.4 mm.

  The substrate is formed with unevenness (pre-groove) representing information such as a guide groove for tracking or an address signal. In order to achieve a higher recording density, it is preferable to use a substrate on which a pre-groove having a narrower track pitch is formed as compared with CD-R and DVD-R. The track pitch of the pregroove is 0.2 to 0.6 μm. The depth of the pregroove (groove depth) is in the range of 20 to 150 nm.

In addition, it is preferable to form an undercoat layer on the substrate surface for the purpose of improving the flatness and the adhesive force.
Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, and chloro. Polymer materials such as sulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, etc .; silane coupling Surface modifiers such as agents;
The undercoat layer is formed by dissolving or dispersing the above materials in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. can do. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, and preferably in the range of 0.01 to 10 μm.

[Recording layer]
The recording layer is a layer formed on a substrate and capable of recording / reproducing information with a laser beam having a wavelength of 340 to 680 nm. As described above, the recording layer has at least a metal oxide layer, and the metal oxide layer is colored by releasing the metal as a simple substance from a part of the metal oxide (coloration phenomenon). ). When this recording layer is irradiated with laser light, the single metal contributing to coloring of the recording layer is oxidized and becomes transparent in the region irradiated with the laser light, and the transmittance of the oxidized region is increased. An area where the transmittance is increased is used as a recording mark, and information can be recorded based on the presence or absence of the recording mark in the same manner as a conventional CD-R or DVD-R.

As a more preferred configuration of the recording layer, a layer of a different metal oxide which is an oxide of a metal different from the metal of the metal oxide is alternately laminated with the metal oxide layer. When dissimilar metal oxides are stacked, it is presumed that a metastable state is likely to be formed due to the influence of differences in lattice distortion and lattice constant.
In the case of this configuration, the metal oxide layer and the dissimilar metal oxide layer are preferably laminated by 10 to 150 layers, and more preferably by 20 to 50 layers.

  Examples of the metal oxide include a ZnO-based oxide, a ZnGaInO-based oxide, a ZnGaInCuO-based oxide, a GaInCuO-based oxide, a GaInO-based oxide, and the like. Preferably used.

Preferred combinations of the metal oxide and the different metal oxide include ZnO / Al ₂ O ₃ , ZnO / Ga ₂ O ₃ , ZnO / In ₂ O ₃ , ZnO / Ag ₂ O and the like.

  The thickness of the recording layer is preferably from 0.01 to 0.2 μm, more preferably from 0.03 to 0.08 μm.

[Light reflection layer]
For the light reflection layer, a light reflective material having a high reflectance with respect to laser light is used. The reflectance is 70% or more.
As a light reflecting material having high reflectance, Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd , Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and other metals and semi-metals or stainless steel. These light reflecting materials may be used alone, or may be used in combination of two or more kinds or as an alloy. Among these, Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel are preferable. Particularly preferred is Au, Ag, Al or an alloy thereof, and most preferred is Au, Ag or an alloy thereof.

[Protective layer]
A protective layer is preferably provided on the light reflecting layer or the recording layer for the purpose of physically and chemically protecting the recording layer and the like. Note that in the case of adopting the same form as in the case of manufacturing a DVD-R type optical recording medium, that is, a structure in which two substrates are bonded with the recording layer inside, the protective layer is not necessarily provided. Examples of materials used for the protective layer include inorganic substances such as SiO, SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ , and organic substances such as thermoplastic resins, thermosetting resins, and UV curable resins. be able to. The thickness of the protective layer is generally in the range of 0.1 μm to 1 mm.

  As another configuration, when the optical recording medium of the present invention has a light reflection layer, a recording layer, and a light transmission layer in this order on a substrate, the light transmission layer includes an adhesive layer or a pressure-sensitive adhesive layer. And is preferably formed on the recording layer. In this case, the configuration other than the light transmission layer is as described above.

[Light transmission layer]
The light transmission layer is formed to prevent the inside of the optical recording medium from impact and the like, and is not particularly limited as long as it is a transparent material, but is preferably polycarbonate, cellulose triacetate, or the like, more preferably at 23 ° C. and 50% RH. The material has a moisture absorption rate of 5% or less.
The term “transparent” means that the recording light and the reproduction light are transmitted (transmittance: 90% or more).

The thickness of the light transmission layer is in the range of 0.01 to 0.2 mm, preferably in the range of 0.03 to 0.1 mm, and more preferably in the range of 0.05 to 0.095 mm.
Moreover, the polycarbonate sheet | seat etc. to which the adhesive was provided to the bonding surface can also be used as a light transmissive layer. In this case, the adhesive layer is not necessary.

Further, the optical recording medium of the present invention may be variously improved in addition to the configuration described above. For example, a barrier layer may be formed between the recording layer described above and the protective layer (or light transmission layer). The material constituting the barrier layer as long as the material transmits the laser beam is not particularly limited, is preferably a dielectric, and more _{specifically, ZnS, TiO 2, SiO 2} , ZnS-SiO ₂ , GeO ₂ , Si ₃ N ₄ , Ge ₃ N ₄ , MgF ₂ , and other inorganic oxides, nitrides, and sulfides. ZnS—SiO ₂ or SiO ₂ is preferable. The thickness of the barrier layer is preferably 1 to 100 nm.

<Method for producing optical recording medium>
Next, the manufacturing method of the present invention for manufacturing the above optical recording medium will be described in detail.

[Formation of recording layer]
First, the above-described substrate is prepared, and a metal oxide layer is formed on the substrate. Examples of the method for forming the metal oxide layer include a sputtering method, a pulse laser deposition (PLD) method, and an ion plating method. Among these, a sputtering method and a PLD method are particularly preferable. Hereinafter, the case where a metal oxide layer is formed by sputtering will be described.

  A metal oxide layer is formed by sputtering a metal oxide. After the metal oxide layer is formed, physical etching or chemical etching is performed (metal oxide forming step). Immediately after forming the metal oxide layer by sputtering, almost 100% of the metal oxide is present in the layer, and in this state, the recording layer is not colored. Therefore, physical etching or chemical etching is performed on the metal oxide layer to release and color the metal that contributes to coloring from the metal oxide as a simple substance. The recording layer is formed as described above.

  In the method for producing an optical recording medium of the present invention, particularly when a sputtering method is employed for forming a recording layer, a metal oxide layer is first formed by sputtering a metal oxide instead of sputtering a single metal as it is. Since the metal is released by physical etching or chemical etching after the formation, contamination in the chamber can be reduced as compared with sputtering using a single metal as a target. Further, in the present invention, since the production is performed using the sputtering method, a thin film can be formed over a wide area, and unlike the case of forming by the PLD method, production suitability is dramatically improved, which is preferable. Furthermore, for example, the film thickness distribution on a substrate having a diameter of 120 mm can be suppressed to within ± 5%. Therefore, it is effective in securing in-plane characteristics of the optical recording medium.

  Further, a step of forming a different metal oxide layer different in metal from the metal oxide (dissimilar metal oxide layer forming step) is provided, and the metal oxide layer forming step and the different metal oxide layer forming step are provided. It is preferable that the metal oxide layer and the dissimilar metal oxide layer are stacked by repeating the above. When manufactured in this manner, as described above, it is preferable to stack different kinds of metal oxides because a metastable state is easily formed due to the influence of lattice distortion or difference in lattice constant.

  When forming a recording layer by laminating a metal oxide layer and a dissimilar metal oxide layer, the metal oxide layer forming step and the dissimilar metal oxide layer forming step are repeated 10 to 150 times. , It is preferable to form 10 to 150 layers, respectively.

(Sputtering)
In the sputtering of the metal oxide or the different metal oxide, the sputtering power (output) is preferably 0.5 to 3.0 kW, and more preferably 1.0 to 2.0 kW. The sputtering pressure (pressure in the chamber during film formation) is preferably 0.15 to 0.70 Pa, and more preferably 0.20 to 0.50 hPa.

As the type of sputtering, various methods such as RF sputtering, DC sputtering, and DC magnetron sputtering can be used.
As the sputtering gas, it is preferable to use Ar gas or a mixed gas obtained by adding other gas to Ar.

(Physical etching)
Examples of the physical etching include ion etching, plasma etching, ion milling, and ECR etching. In particular, it is preferable to apply ion etching.
Moreover, in the conditions where the pressure in the chamber is 0.2 to 0.6 Pa, the acceleration voltage is 80 to 100 V, the Ar gas is used, and the reach distance to the substrate is 150 to 250 mm, the etching time is preferably 120 to 300 seconds, More preferably, it is 180 to 240 seconds.
Impurities such as organic substances on the surface can be removed by ion etching, and a good interface state can be obtained. As the process gas for ion etching, argon, oxygen, or a mixed gas thereof can be used.

For example, ion etching is preferably performed under the following conditions. That is,
(1) Process gas flow rate: 20 to 160 sccm (more preferably 40 to 80 sccm)
(2) Acceleration voltage: 70 to 95 V (more preferably, 80 to 90 V)

(Chemical etching)
The chemical etching is an etching using a chemical reaction such as an oxidation-reduction reaction. In the present invention, a reducing gas is used because it is sufficient that the metal oxide can be reduced to release a single metal. Examples of the reducing gas that can be used in the present invention include hydrogen, carbon monoxide, and methane. Among them, it is particularly preferable to use hydrogen.

[Formation of light reflection layer]
The light reflecting layer can be formed on the substrate by vapor deposition, sputtering or ion plating of the light reflecting material described above. The thickness of the light reflecting layer is generally in the range of 10 to 300 nm, and preferably in the range of 50 to 200 nm.

[Formation of protective layer]
The protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic on the reflective layer via an adhesive. Or you may provide by methods, such as vacuum evaporation, sputtering, and application | coating. In the case of a thermoplastic resin or a thermosetting resin, it can also be formed by dissolving these in a suitable solvent to prepare a coating solution, and then applying and drying the coating solution. In the case of a UV curable resin, it can also be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, coating the coating solution, and curing it by irradiating with UV light. In these coating liquids, various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added according to the purpose.

[Formation of light transmission layer]
Next, a method for forming a light transmission layer on the optical recording medium will be described. The light transmission layer is prepared by dissolving a photocurable resin constituting the adhesive layer in a suitable solvent to prepare a coating solution, and then coating the coating solution on the recording layer at a predetermined temperature to form a coating film. For example, a cellulose triacetate film (TAC film) obtained by extruding plastic can be laminated on the coating film, and the coating film can be formed by irradiating light on the laminated TAC film. . The TAC film preferably contains an ultraviolet absorber.

[Formation of barrier layer]
When forming a barrier layer, sputtering _{ZnS, TiO 2, SiO 2,} ZnS-SiO 2, GeO 2, Si 3 N 4, Ge 3 N 4, MgF 2, inorganic oxides etc., nitrides, sulfides, It can be formed by ion plating or the like.

  Since the optical recording medium of the present invention is manufactured by the above-described manufacturing method of the optical recording medium of the present invention, the film thickness distribution can be reduced particularly when the recording layer is formed by sputtering. it can. For example, the film thickness distribution on a substrate having a diameter of 120 mm can be suppressed to within ± 5%.

[Example 1]
A substrate having a thickness of 0.6 mm and a diameter of 120 mm having a spiral (spiral) groove (depth: 100 nm, width 200 nm, track pitch: 0.4 μm) was molded from polycarbonate resin by injection molding.
Using a ZnO target as a metal oxide material, sputtering was performed under the following conditions to form a ZnO single layer film (metal oxide layer) on the substrate. Further, the metal oxide layer was etched under the following conditions to form a recording layer. Thus, an optical recording medium of Example 1 was obtained.
(Sputtering conditions)
Equipment used: Static facing sputtering equipment, Ar flow rate: 30 sccm, pressure: 0.16 Pa, RF power: 150 W, substrate-target distance: 75 mm, target size: φ180 × t10 mm, no substrate temperature control, no substrate bias applied ( Etching conditions)
Equipment used: Ar etching with an ion beam gun, Ar flow rate: 40 sccm, acceleration voltage: 85 V, ion gas-substrate distance: 170 mm, etching time: 60 seconds

[Example 2]
An optical recording medium of Example 2 was produced in the same manner as in Example 1 except that an Al ₂ O ₃ target was added as a different metal oxide and a ZnO / Al ₂ O ₃ laminated film was formed.

[Comparative Example 1]
An optical recording medium of Comparative Example 1 was produced in the same manner as in Example 1 except that the etching treatment was not performed.

[Comparative Example 2]
An optical recording medium of Comparative Example 2 was produced in the same manner as Example 2 except that the etching treatment was not performed.

[Evaluation]
About the optical recording medium of Examples 1-2 and Comparative Examples 1-2, the transmittance | permeability with respect to the light of wavelength 405nm of a recording layer was measured with the absorptiometer (Shimadzu Corporation make, UV-3100PC). The measurement results are shown in Table 1.

As shown in Table 1, the optical recording medium of Example 1 subjected to the etching treatment after forming the ZnO layer has a transmittance of 98% for the laser beam having a wavelength of 405 nm as compared with Comparative Example 1 not subjected to the etching treatment. To 87% (n = 5 average value). This is presumed that ZnO was metastable by performing the etching process, and Zn simple substance was generated from ZnO which is a complete oxide.
Further, the optical recording medium of Example 2 in which 20 layers of ZnO / Al ₂ O ₃ were stacked and then subjected to etching treatment was a laser having a wavelength of 405 nm as compared with Comparative Example 1 in which etching treatment was not performed. The transmittance for light decreased from 95% to 75% (n = 5 average value). In the case where different kinds of metal oxides are stacked, it is considered that a metastable state is easily formed due to the influence of differences in lattice distortion and lattice constant.
FIG. 1 is a graph showing transition of light transmittance with respect to etching time when 20 layers of ZnO / Al ₂ O ₃ are stacked. FIG. 1 shows that an etching time of 120 to 300 seconds is appropriate.

It is a figure which shows transition of the light transmittance with respect to etching time with a graph.

Claims (5)

A method of manufacturing an optical recording medium having a recording layer containing a metal oxide on a substrate,
The method for producing an optical recording medium, comprising forming a metal oxide layer by performing physical etching or chemical etching after forming the metal oxide layer in forming the recording layer.   2. The method of manufacturing an optical recording medium according to claim 1, wherein the metal oxide layer is formed by a sputtering method.   Furthermore, it has the different metal oxide layer formation process which forms the layer of the different metal oxide which is an oxide of the metal different from the metal of the said metal oxide, The said metal oxide layer formation process and the said different metal oxide 3. The method of manufacturing an optical recording medium according to claim 1, wherein the step of forming a layer is repeated, and a metal oxide layer and a dissimilar metal oxide layer are laminated.   4. The method of manufacturing an optical recording medium according to claim 1, wherein the time for performing the physical etching or the chemical etching is 120 to 300 seconds. 5.   An optical recording medium obtained by the method for producing an optical recording medium according to claim 1.

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