Title of Invention

SPUTTERING TARGET AND OPTICAL INFORMATION RECORDING MEDIUM AND MANUFACTURING METHOD THEREOF

Abstract

A sputtering target characterized by comprising a composite oxide of HfO₂ and Y₂O₃; the sputtering target wherein the content of Y₂O₃ is in the range of 10 to 95 mol% while the balance consists of HfO₂; and the sputtering target characterized in that further ZrO₂ is contained in an amount of 10 to 90 mol%. Furthermore, there is provided a thin film for optical information recording medium (especially used as a protective film) that is stable in its amorphous property, excelling in adherence to recording layer and mechanical properties and exhibits high transmittance, and that when comprised of a nonsulfide material, retards any deterioration of adjacent reflection layer and recording layer. Still further, there are provided a process for producing the same and a sputtering target applicable thereto. Ultimately, the performance of optical information recording medium and the productivity thereof can be strikingly enhanced.

Full Text

FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003COMPLETE SPECIFICATION (See section 10 and rule 13) 1. SPUTTERING TARGET AND OPTICAL INFORMATION RECORDING MEDIUM AND MANUFACTURING METHOD THEREOF 2.(A) (B) (C) NIPPON MINING & METALS CO., LTD.JAPANESE10-l,Toranomon 2-chome,Minato-ku,Tokyo 105-0001,Japan. The following specification particularly describes the invention and the manner in which it is to be performed. 1 TECHNICAL FIELD The present invention relates to a thin film for an optical information recording medium (especially used as a protective film) that has stable film amorphous nature, is superior in adhesiveness and mechanical properties with the recording layer, has a high transmission factor, and is composed with a non-sulfide system, whereby the deterioration of the adjacent reflective layer and recording layer can be suppressed. The present invention also relates to a manufacturing method of such a thin film, and a sputtering target for use therein. BACKGROUND ART Conventionally, ZnS-Si02 generally and primarily used as a protective layer of a phase change optical information recording medium has superior characteristics such as in optical characteristics, heat characteristics, and adhesiveness with the recording layer, and is being widely used. Nevertheless, rewritable DVDs in the present day as represented by Blu-ray discs are strongly demanded of more write cycles, greater capacity, and faster recording. As one reason for deterioration in the write cycles of an optical information recording medium, there is the diffusion of a sulfur constituent from the ZnS-Si02 to the recording layer material disposed in between the protective layers formed from ZnS-Si02. Further, although pure Ag or Ag alloy having high thermal conduction properties with a high reflection ratio is being used as the reflective layer material for realizing high capacity and high-speed recording, this kind of reflective layer is also disposed to come in contact with the protective layer material of ZnS-Si02. Therefore, in this case also, as a result of diffusion of the sulfur constituent from the ZnS-SiC>2, the pure Ag or Ag alloy reflective layer material is subject to corrosive degradation, and would cause the characteristic degradation in the reflection ratio of the optical information recording medium. 2 As a measure for preventing the diffusion of such sulfur constituent, attempts have been made to provide an intermediate layer having nitrides or carbides as its primary component between the reflective layer and protective layer, and between the recording layer and protective layer. Nevertheless, this results in an increased number of layers, and there is a problem in that throughput will deteriorate and costs will increase. In order to overcome the foregoing problems, there is a pressing need to substitute the material with an oxide material that does not contain sulfides in the protective layer material, or discover a material having optical characteristics and amorphous stability that are equivalent to or better than ZnS-Si02. In light of the above, an oxide protective layer material, a transparent conductive material and an optical thin film have been proposed (refer to Patent Documents 1 to 3). However, Patent Documents 1 to 3 have a problem in that they contain areas that are inferior in optical characteristics and amorphous nature. [Patent Document 1] Japanese Patent Laid-Open Publication No. H01-317167 [Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-90745 [Patent Document 3] Japanese Patent Laid-Open Publication No. 2003-166052 SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film for an optical information recording medium (especially used as a protective film) that has stable film amorphous nature, is superior in adhesiveness and mechanical properties with the recording layer, has a high transmission factor, and is composed with a non-sulfide system, whereby the deterioration of the adjacent reflective layer and recording layer can be suppressed. The present invention also provides a manufacturing method of such a thin film, and a sputtering target for use therein. As a result, the present invention is able to improve the performance of the optical information recording medium, and to considerably improve the productivity thereof. In order to overcome the foregoing problems, as a result of intense study, 3 the present inventors discovered that, by substituting the conventional protective layer material ZnS-Si02 with an oxide material presented below that does not contain sulfides, it is possible to ensure optical characteristics and amorphous stability that are equivalent to 2nS-Si02 while improving the characteristics of the optical information recording medium and improving the productivity. Based on the foregoing discovery, the present invention provides 1) a sputtering target comprising a compound oxide of HfC>2 and Y203; 2) the sputtering target according to 1) above, wherein the Y2O3 content is 10 to 95 mol% and the remnant is Hf02; and 3) the sputtering target according to 1) or 2) above further containing 10 to 90 mol% of Zr02. Further, the present invention also provides 4) the sputtering target according to any one of 1) to 3) above, wherein the relative density is 90% or higher, 5) an optical information recording medium and a manufacturing method thereof, wherein the sputtering target according to any one of 1) to 4) above is used at least as a thin film in forming a part of an optical information recording medium structure, and 6) an optical information recording medium and a manufacturing method thereof, wherein the sputtering target according to any one of 1) to 5) above is used at least as a thin film in forming a part of an optical information recording medium structure and disposed adjacent to a recording layer or a reflective layer. Effect of the Invention As a result of the above, by substituting the protective layer material ZnS-Si02 with an oxide material that does not contain sulfides, it is possible to provide to a thin film for an optical information recording medium (especially used as a protective film) that has superior characteristics such as having stable film amorphous nature, being superior in adhesiveness and mechanical properties with the recording layer, and having a high transmission factor, whereby the deterioration of the adjacent reflective layer and recording layer caused by sulfur can be suppressed, as well as a manufacturing method of such a thin film, and a sputtering target for use therein. Further, by using this material, a superior effect is yielded in that it is possible to improve the performance of the optical information recording medium, and considerably improve the productivity thereof. 4 BEST MODE FOR CARRYING OUT THE INVENTION The sputtering target of the present invention comprises a compound oxide of Hf02 and Y2O3. In particular, the Y2O3 content is 10 to 95 mol% and the remnant is Hf02. If the Y2O3 content is less than 10 mol% or if the Y2O3 content exceeds 95 mol%, there is a problem in that the sputtering target will lack stability in the amorphous nature. Further, 10 to 90 mol% of Zr02 may be added. Zr02 is characterized in that it has high thermal conductivity. When utilizing this characteristic and adding Zr02, it is desirable to added 10 to 90 mol% of Zr02. If the Zr02 content is less than 10 mol%, there is no effect of addition, and if the Zr02 content exceeds 90 mol%, there is a problem in that the sputtering target will lack stability in the amorphous nature, and it is desirable to add Zr02 within the range described above. This material has stable optical characteristics and amorphous nature of the film, and is suitable as a protective layer of a phase-change optical recording medium. Radio frequency sputtering is used for the deposition. Since this material has stable amorphous nature and is able to improve the transmission factor as described above, it is suitable as a protective layer material for a phase change recording medium or a blue laser phase change recording medium with a fast rewriting speed. Further, the sputtering target of the present invention is able to achieve a relative density of 90% or higher. The improvement in density yields an effect of improving the uniformity of the sputtered film and inhibiting the generation of particles during sputtering. The sputtering target described above can be used at least as a thin film in forming a part of an optical information recording medium structure to provide an optical information recording medium. Further, the foregoing sputtering target can be used at least as a thin film in forming a part of an optical information recording medium structure, and disposed adjacent to a recording layer or a reflective layer. Moreover, the thin film formed using the sputtering target of the present 5 invention forms a part of the optical information recording medium structure and is disposed adjacent to the recording layer or reflective layer, but as described above, since ZnS is not used, there is no contamination by S, there is no diffusion of the sulfur constituent to the recording layer material disposed between the protective layers, and there is a significant effect in that the deterioration of the recording layer can be prevented thereby. Further, when using pure Ag or Ag alloy having high thermal conduction properties at a high reflection ratio as adjacent reflective layers for realizing high capacity and high-speed recording, diffusion of the sulfur constituent to such adjacent reflective layers will not occur, and a superior effect is yielded in that the cause of the reflective layer material being subject to corrosive degradation and causing characteristic degradation in the reflection ratio of the optical information recording medium can be cleared out. The sputtering target of the present invention can be manufactured by subjecting the oxide powder of the respective constituent elements, in which the average grain size is 5um or less, to pressure less sintering or high temperature pressure sintering. It is thereby possible to obtain a sputtering target having a relative density of 90% or higher. In such a case, it is desirable to calcinate the oxide powder having hafnium oxide or yttrium oxide as its primary component at a temperature of 800 to 1400°C before sintering. After this calcinations, the resultant powder is pulverized to 3pm or less and used as the raw material for sintering. Further, by using the sputtering target of the present invention, a significant effect is yielded in that it is possible to improve the productivity, obtain a high-quality material, and stably manufacture an optical recording medium having an optical disk protective film at low costs. Improvement in the density of the sputtering target of the present invention reduces holes and miniaturizes crystal grains, and enables the sputtered face of the target to become uniform and smooth. As a result, a significant result is yielded in that particles and nodules generated during sputtering can be reduced, the target life can be extended, and the mass productivity can be improved with minimal variation in the quality. Examples 6 Examples and Comparative Examples of the present invention are now explained. These Examples are merely illustrative, and the present invention shall in no way be limited thereby. In other words, the present invention shall only be limited by the scope of the present invention, and shall include the various modifications other than the Examples of this invention. (Examples 1 to 6) Y203 powder equivalent of 4N and 5pm or less and Zr02 powder and Hf02 powder equivalent of 3N and an average grain size of 5pm or less were prepared, and these powders were mixed to achieve the composition shown in Table 1, subject to wet blending, dried, and thereafter calcinated at 1100°C. Further, after subjecting the calcinated powder to wet pulverization up to an average grain size equivalent to 1pm, a binder was added and this was granulated with a spray dryer. This granulated powder was subject to cold pressure forming, thereafter subject to pressure less sintering under oxygen atmosphere at 1300 to 1600°C, and this sintered material was formed into a target with machining process. The constituent and composition ratio of this target are shown in Table 1. [Table 1] Examples Composition TransmissionFactor 405nm (%) Refractive Amorphous Index Nature 405nm Example 1 HfC-2-20 mol% Y203 98 2.1 1.1 Example 2 HfC-2-40 mol% Y2O3 96 2.1 1.0 Example 3 HfC-2-60 mol% Y203 97 2.0 1.1 Example 4 HfO2-80 mol% Y2O3 97 1.9 1.0 Example 5 ZrO2-10 mol% HfO2-20 mol% Y2O3 97 2.1 1.1 Example 6 ZrO2-30 mol% HfO2-40 mol% Y2O3 97 2.0 1.0 Comparative Example 1 Hf02 95 2.1 1.9 Comparative Example 2 Zr02 97 2.1 2.3 Comparative Example 3 Y2O3 93 1.9 2.5 Comparative Example 4 Zr02-5 mol% Y203 97 2.0 2.1 Comparative Example 5 Hf02-5 mol% Y2O3 95 2.1 1.8 Comparative Example 6 ZnS-SiC-2 (20 mol%) 80 2.3 1.1 Amorphous nature was represented with the maximum peak strength against an undeposited glass substrate in a range of 29 = 20-60° in the XRD measurement of the deposition sample subject to anneal processing (600°C * 30min,Ar atmosphere). The foregoing 6-inchq> size target subject to finish processing was used to perform sputtering. The sputtering conditions were RF sputtering, sputtering power of 1000W, and Ar gas pressure of 0.5Pa, and deposition was performed at a target film thickness of 1500A. Results of the measured transmission factor (wavelength 633nm)%, refractive index (wavelength 633nm), and amorphous nature (represented with the maximum peak strength against an undeposited glass substrate in a range of 29 = 20-60° in the XRD measurement (Cu-Ka , 40kV, 30mA) of the deposition sample subject to anneal processing (600°C * 30min, Ar atmosphere)) are collectively shown in Table 1. As a result of the above, the sputtering target of Examples 1 to 6 achieved a relative density of 90% or higher, and stable RF sputtering could be performed. Further, the transmission factor of the sputtered film achieved 96 to 98% (405pm), the refractive index was 1.9 to 2.1, no specific crystal peak could be observed, and possessed a stable amorphous nature (1.0 to 1.1). Since the targets of the Examples do not use ZnS, there is no characteristic degradation in the optical information recording medium caused by the diffusion or contamination of sulfur. Further, in comparison to the Comparative Examples described later, the transmission factor, refractive index, and amorphous stability all showed favorable numerical values. (Comparative Examples 1 to 6) As shown in Table 1, materials having components and compositions of raw material powder that are different from the conditions of the present invention were prepared, and, particularly in Comparative Example 6, ZnS raw material powder was prepared, and targets were prepared with these materials under the same conditions as the Examples, and such targets were used to form a sputtered film. The results are similarly shown in Table 1. With respect to the components and compositions of the Comparative Examples that deviate from the composition ratio of the present invention; for instance regarding Comparative Example 1, since it did not contain any Y oxide, the amorphous nature was 1.9 and showed inferior results. 9 With Comparative Example 2, since it did not contain any Y oxide as above, the amorphous nature was 2.3 and showed inferior results. With Comparative Example 3, since Y oxide was provided alone, the amorphous nature was 2.5 and showed inferior results. With Comparative Example 4, since the Y oxide content is less than the reference amount in the combination of Zr oxide and Y oxide, the amorphous nature was 2.1 and showed inferior results. With Comparative Example 5, since the Y oxide content is less than the reference amount in the combination of Hf oxide and Y oxide, the amorphous nature was 1.8 and showed inferior results. Further, Comparative Example 6 in particular contained large amounts of ZnS, the transmission factor was 80%, and resulted in a material with risk of being contamination with sulfur. INDUSTRIAL APPLICABILITY Since the thin film formed by using a sputtering target of the present invention forms a part of the structure of the optical information recording medium and does not use ZnS, it yields a significant effect in that diffusion of the sulfur constituent to the recording layer material will not occur, and deterioration of the recording layer can be prevented thereby. Further, when using pure Ag or Ag alloy having high thermal conduction properties at a high reflection ratio as adjacent reflective layers, diffusion of the sulfur constituent to such reflective layers will not occur, and a superior effect is yielded in that the cause of the reflective layer being subject to corrosive degradation and causing characteristic degradation can be cleared out. Further, in addition to the amorphous nature becoming stabilized, the target will be provided with conductivity, and stable RF sputtering will be enabled by making the relative density a high density of 90% or higher. Moreover, there is a significant effect in that the controllability of sputtering can be facilitated, and the sputtering efficiency can also be improved. Further still, there is significant effect in that it is possible to reduce the particles (dust) or nodules arising during sputtering upon performing deposition, improve the mass productivity with little 10 variation in quality, and stably manufacture an optical recording medium having an optical disk protective film at low costs. We Claim:- 1. A sputtering target for forming an optical information recording medium thin film comprising a compound oxide of Hf02 and Y203. 2. The sputtering target for forming an optical information recording medium thin film according to claim 1, wherein the Y203 content is 10 to 95 mol% and the remnant is Hf02. 3. The sputtering target for forming an optical information recording medium thin film according to claim 1 or claim 2 containing 10 to 90 mol% of Zr02. 4. The sputtering target for forming an optical information recording medium thin film according to any one of claims 1 to 3, wherein the relative density is 90% or higher. 5. An optical information recording medium comprising a thin film configured from a compound oxide of Hf02 and Y203 formed via sputtering at least at a part of an optical information recording medium structure. 6. The optical information recording medium according to claim 5, wherein the Y203 content is 10 to 95 mol% and the remnant is Hf02. 7. The optical information recording medium according to claim 5 or claim 6 containing 10 to 90 mol% of Zr02. 8. The optical information recording medium according to any one of claims 5 to 7, wherein said thin film is disposed adjacent to a recording layer or a reflective layer. 9. A manufacturing method of an optical information recording medium, wherein a thin film is formed at least at a part of an optical information recording medium structure using the target according to any one of claims 1 to 4. 12 10. A manufacturing method of an optical information recording medium according to claim 9, wherein said thin film is disposed adjacent to a recording layer or a reflective layer. 11. A Sputtering Target and Optical Information Recording Medium and Manufacturing Method Thereof as claimed substantially as herein described with forgoing description. Dated this 10th day of August 2006. Dr. Rajeshkumar H. Acharya Advocate & Patent Agent For and on Behalf of Applicant ABSTRACT Provided are a sputtering target comprising a compound oxide of Hf02 and Y203; the foregoing sputtering target wherein the Y203 content is 10 to 95 mol% and the remnant is Hf02; and the foregoing sputtering target further containing 10 to 90 mol% of Zr02. The present invention also provides a thin film for an optical information recording medium (especially used as a protective film) that has stable film amorphous nature, is superior in adhesiveness and mechanical properties with the recording layer, has a high transmission factor, and is composed with a non-sulfide system, whereby the deterioration of the adjacent reflective layer and recording layer can be suppressed. The present invention also provides a manufacturing method of such a thin film, and a sputtering target for use therein. As a result, the present invention is able to improve the performance of the optical information recording medium, and to considerably improve the productivity thereof.

Documents:

951-mumnp-2006-abstract(25-09-2007).doc

951-mumnp-2006-abstract(25-09-2007).pdf

951-mumnp-2006-abstract.doc

951-mumnp-2006-abstract.pdf

951-mumnp-2006-cancelled pages(25-09-2007).pdf

951-mumnp-2006-claims(granted)-(25-09-2007).doc

951-mumnp-2006-claims(granted)-(25-09-2007).pdf

951-mumnp-2006-claims.doc

951-mumnp-2006-claims.pdf

951-mumnp-2006-correspondance-received.pdf

951-mumnp-2006-correspondence(15-04-2008).pdf

951-mumnp-2006-correspondence(ipo)-(14-07-2008).pdf

951-mumnp-2006-declaration(04-08-2006).pdf

951-mumnp-2006-description (complete).pdf

951-mumnp-2006-form 1(11-08-2006).pdf

951-MUMNP-2006-FORM 16(18-2-2011).pdf

951-mumnp-2006-form 18(17-08-2006).pdf

951-mumnp-2006-form 2(granted)-(25-09-2007).doc

951-mumnp-2006-form 2(granted)-(25-09-2007).pdf

951-mumnp-2006-form 26(04-08-2006).pdf

951-mumnp-2006-form 3(11-08-2006).pdf

951-mumnp-2006-form 3(25-09-2007).pdf

951-mumnp-2006-form 5(04-08-2006).pdf

951-mumnp-2006-form-1.pdf

951-mumnp-2006-form-2.doc

951-mumnp-2006-form-2.pdf

951-mumnp-2006-form-3.pdf

951-mumnp-2006-form-5.pdf

951-mumnp-2006-form-pct-ipea-409.pdf