JP2005251236A - Sputtering target, protective film for optical information recording medium, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film (used especially for a protective film) for an optical information recording medium having stable amorphous properties, excellent adhesiveness to a recording layer and mechanical characteristics and high transmittance and hardly generating deterioration of the adjacent recording layer and an adjacent reflection layer because of its non-sulfide based constitution, to provide its manufacturing method and to provide a sputtering target which can be applied thereto. <P>SOLUTION: The sputtering target for forming the protective film for the optical information recording medium consists of a material which consists essentially of Ta<SB>2</SB>O<SB>5</SB>and to which a glass forming oxide is added and has ≥90% transmittance (405 nm wavelength) and a refractive index of 1.8 to 2.4 (405 nm wavelength). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, since the amorphousness of the sputtered film is stable, the adhesiveness with the recording layer is excellent, the mechanical properties are high, and the transmittance is high. The present invention relates to a protective film for an optical information recording medium in which deterioration of a recording layer hardly occurs, a manufacturing method thereof, and a patching target applicable to these.

Conventionally, ZnS-SiO ₂ generally used mainly for the protective layer of phase change type optical information recording media has excellent characteristics such as optical characteristics, thermal characteristics, adhesion to the recording layer, etc. in use.
However, today, rewritable DVDs represented by Blue-Ray are strongly required to increase the number of rewrites, increase the capacity, and increase the recording speed.

One of the causes of deterioration of the number of times of rewriting of the optical information recording medium is diffusion of sulfur components from ZnS-SiO ₂ to the recording layer material arranged so as to be sandwiched between the protective layers ZnS-SiO _2. .
In addition, pure Ag or Ag alloy having high reflectivity and high thermal conductivity has been used for the reflective layer material for increasing the capacity and recording speed, but such a reflective layer is also a protective layer material. They are arranged in contact with the ZnS-SiO _2.
Accordingly, in this case as well, due to the diffusion of the sulfur component from ZnS-SiO ₂ , the pure Ag or Ag alloy reflective layer material also corrodes and becomes a factor causing deterioration in characteristics such as reflectance of the optical information recording medium. It was.

In order to prevent diffusion of these sulfur components, an intermediate layer mainly composed of nitride or carbide is provided between the reflective layer and the protective layer and between the recording layer and the protective layer. However, this causes an increase in the number of stacked layers, resulting in a problem of reduced throughput and increased cost.
In order to solve the above problems, the protective layer material is replaced with an oxide-free material that does not contain sulfides, and a material system having optical properties equal to or better than ZnS-SiO ₂ and amorphous stability is found. It was an urgent need.

For these reasons, oxide-based protective layer materials, transparent conductive materials, or optical thin films have been proposed (see Patent Documents 1 to 3). However, Patent Documents 1 to 3 have a problem including a region where optical properties and amorphousness are inferior.
Japanese Patent Laid-Open No. 01-317167 JP 2000-90745 A JP 2003-166052 A

  The present invention is stable in the amorphousness of the film, excellent in adhesion to the recording layer, excellent in mechanical properties, high in transmittance, and composed of a non-sulfide system, so that the adjacent reflective layer, recording layer The present invention relates to use as a protective film for an optical information recording medium in which deterioration of the optical information hardly occurs, a manufacturing method thereof, and a patching target applicable to these, and thereby greatly improving the characteristics of the optical information recording medium. Objective.

In order to solve the above problems, the present inventors conducted extensive research, and as a result, replaced the conventional protective layer material ZnS-SiO ₂ with a sulfide-free oxide-only material presented below, In addition, the inventors have obtained knowledge that optical characteristics and amorphous stability equivalent to those of ZnS-SiO ₂ can be secured and the characteristics of the optical information recording medium can be improved.

Based on this knowledge, the present invention is composed of 1) a material mainly composed of Ta ₂ O ₅ and added with a glass-forming oxide, having a transmittance of 90% or more (wavelength of 405 nm) and a refractive index of 1.8 to 2.4 ( Sputtering target for forming a protective film for optical information recording media having a wavelength of 405 nm), 2) It is made of a material mainly composed of Ta ₂ O ₅ and added with a glass-forming oxide, and has a transmittance of 90% or more (wavelength of 405 nm). ) And a refractive index of 1.8 to 2.4 (wavelength 405 nm), and a sputtering target for forming a protective film for an optical information recording medium characterized by being amorphous and stable in a thin film state, 3) The sputtering target according to 1 or 2, characterized by comprising a material to which 5 to 50 mol% of a glass-forming oxide is added, 4) 1 to 3 characterized in that SiO ₂ is added as a glass-forming oxide. Z To provide a sputtering target of crab described.

  Moreover, this invention uses 5) the sputtering target in any one of 1-4 characterized by relative density being 90% or more, and 6) the sputtering target in any one of said 1-5. Provided is a protective film for an optical information recording medium having a transmittance of 90% or more (wavelength 405 nm) and a refractive index of 1.8 to 2.4 (wavelength 405 nm), and a method for producing the same.

As described above, the conventional protective layer material ZnS-SiO ₂ is replaced with an oxide-only material that does not contain sulfide, thereby suppressing deterioration of the adjacent reflective layer, recording layer, etc. due to sulfur, and ZnS- Protective film for optical information recording medium having excellent properties such as optical properties equal to or better than SiO ₂ and amorphous stability, excellent adhesion to recording layer, mechanical properties, and high transmittance It is possible to provide a manufacturing method and a sputtering target applicable to them.
Further, the use of this material system has an excellent effect that the characteristics of the optical information recording medium can be improved.

The sputtering target of the present invention is made of a material mainly composed of Ta ₂ O ₅ and added with a glass forming oxide. In particular, it is desirable to add 5 to 50 mol% of a glass forming oxide, and SiO ₂ is usually used as the glass forming oxide. In addition, B ₂ O ₃ or silicate glass can be used as the glass-forming oxide, but pure SiO ₂ is optimal for the production method.
One of the major features of the present invention is that it is amorphous in a thin film state. Addition of less than 5 mol% of glass-forming oxide does not provide a sufficient effect of amorphous stability, and addition of more than 50 mol% results in inadequate optical properties (refractive index, transmittance) and is good. The characteristic cannot be obtained. Therefore, it is desirable to add glass-forming oxide in the range of 5 to 50 mol%.

This material is stable in optical characteristics and amorphousness of the film, and is suitable as a protective layer material for a phase change optical recording medium. For film formation, high frequency sputtering is used.
Since this material is stable in amorphousness and can improve the transmittance as described above, it is suitable for a phase change recording medium having a fast rewrite speed or a protective layer material for a phase change recording medium of a blue laser system.

Further, the sputtering target of the present invention can have a relative density of 90% or more. The improvement in density has the effect of improving the uniformity of the sputtered film and suppressing the generation of particles during sputtering.
By using the sputtering target described above, it is possible to provide an optical information recording medium which forms at least a part of the optical information recording medium structure as a thin film. Furthermore, using the sputtering target, it is possible to produce an optical information recording medium in which at least a part of the structure of the optical information recording medium is formed as a protective film and is disposed adjacent to the recording layer or the reflective layer. it can.

Furthermore, the thin film formed using the sputtering target of the present invention forms a part of the structure of the optical information recording medium and is arranged adjacent to the recording layer or the reflective layer. Since it is not used, there is no contamination due to S, and there is no significant diffusion of sulfur component into the recording layer material arranged so as to be sandwiched between protective layers, thereby eliminating the deterioration of the recording layer.
In addition, pure Ag or Ag alloy having high reflectivity and high thermal conductivity has been used for the reflective layer material in order to increase the capacity and increase the recording speed, but the sulfur component to the adjacent reflective layer has been used. Diffusion is also eliminated, and the reflective layer material is similarly corroded and has an excellent effect of eliminating the cause of deterioration of characteristics such as reflectance of the optical information recording medium.

 The sputtering target of the present invention can be produced by atmospheric pressure sintering or high temperature pressure sintering of oxide powders of each constituent element having an average particle size of 5 μm or less. Thereby, a sputtering target having a relative density of 90% or more is obtained. In this case, it is desirable that the oxide powder containing zinc oxide as a main component is calcined at 800 to 1300 ° C. before sintering. After this calcination, it is pulverized to 3 μm or less to obtain a raw material for sintering.

The oxide raw material powder used is a stoichiometric oxide. That is, there is no method of reducing the amount of oxygen as a whole by mixing an oxide powder with a small amount of oxygen or the same kind of element (metal) powder into an oxide powder.
As a result, a uniform target with high density can be obtained. Further, there is a significant advantage that a complicated process such as constantly adjusting the amount of oxygen at the time of sputtering is not required, and further, composition variation and in-plane variation of the oxide film can be prevented. A high density and uniform target has the following particle generation preventing effect during sputtering.

Furthermore, by using the sputtering target of the present invention, productivity is improved, a material with excellent quality can be obtained, and an optical recording medium having an optical disk protective film can be manufactured stably at low cost. There is.
The improvement in the density of the sputtering target of the present invention can reduce the number of vacancies, refine the crystal grains, and make the sputtering surface of the target uniform and smooth, thereby reducing particles and nodules during sputtering, and further improving the target life. It has a remarkable effect that it can be lengthened, and there is little variation in quality, so that mass productivity can be improved.

  Hereinafter, description will be made based on Examples and Comparative Examples. In addition, a present Example is an example to the last, and is not restrict | limited at all by this example. In other words, the present invention is limited only by the scope of the claims, and includes various modifications other than the examples included in the present invention.

(Example 1-7)
4N equivalent SiO ₂ powder of 5 μm or less, B ₂ O ₃ powder and 4N equivalent Ta ₂ O ₅ powder with an average particle size of 5 μm or less are prepared, prepared to have the composition shown in Table 1, and wet mixed After drying, it was calcined at 1100 ° C.
Further, the calcined powder was wet pulverized to an average particle size equivalent to 1 μm, then dried and hot-press sintered at 1200 ° C., and the sintered material was finished into a target shape by machining. The component composition of this target is shown in Table 1.

Sputtering was performed using the above-mentioned 6-inch φ-sized target that was finished. The sputtering conditions were RF sputtering, sputtering power 1000 W, Ar gas pressure 0.5 Pa, and a target film thickness of 1500 mm.
XRD (Cu-Kα, film-formed sample annealed (600 ° C. × 30 min, Ar atmosphere) subjected to transmittance (wavelength 405 nm)%, refractive index (wavelength 405 nm), amorphous (film sample annealing) Table 1 summarizes the measurement results and the like of the maximum peak intensity with respect to an undeposited glass substrate in the range of 2θ = 20-60 ° in the measurement at 40 kV, 30 mA).

As a result, the sputtering target of Example 1-3 reached a relative density of 90 or more, and stable RF sputtering was possible.
The transmittance of the sputtered film reaches 91 to 94% (405 nm), the refractive index is 1.9 to 2.4, no specific crystal peak is observed, and stable amorphous properties (1.0 -1.1).
Since the target of this example does not use ZnS, the characteristic deterioration of the optical information recording medium due to sulfur diffusion / contamination does not occur. Moreover, compared with the comparative example mentioned later, all of the transmittance | permeability, refractive index, and amorphous stability of the film-forming sample showed the favorable value.

(Comparative Example 1-3)
As shown in Table 1, a raw material component and composition ratio material different from the conditions of the present invention, in particular, a ZnS raw material powder is prepared in Comparative Example 3, and a target is produced under the same conditions as in the example. In addition, a sputtered film was formed using this target.
The results are also shown in Table 1.

The component / composition of the comparative example deviating from the composition ratio of the present invention, for example, comparative example 1, does not contain any glass-forming oxide, so the transmittance is as low as 85% and the amorphous property is 2. 4 was a bad result.
In Comparative Example 2, since the amount of Si oxide was large, the refractive index was lower than the standard.
In particular, Comparative Example 3 contained a large amount of ZnS, had a low transmittance of 80%, and had a risk of contamination with sulfur.

The thin film formed using the sputtering target of the present invention forms part of the structure of the optical information recording medium and does not use ZnS, so that there is no diffusion of the sulfur component into the recording layer material. There is a remarkable effect that the recording layer is not deteriorated. In addition, when pure Ag or Ag alloy having high heat conductivity and adjacent reflectivity is used for the reflection layer, diffusion of sulfur component to the reflection layer is eliminated, and the reflection layer is deteriorated due to corrosion deterioration. It has an excellent effect of causing the cause to be wiped out.
Further, the amorphousness is stabilized and the target is provided with conductivity, and the relative density is increased to 90% or more, thereby enabling stable RF sputtering film formation. And there exists a remarkable effect that the controllability of sputtering can be facilitated and the sputtering efficiency can be improved. Furthermore, particles (dust generation) and nodules generated during sputtering during film formation can be reduced, quality variations can be reduced, and mass productivity can be improved. Optical recording media with an optical disc protective film can be stably manufactured at low cost. There is a remarkable effect that it can be manufactured.

Claims (6)

For an optical information recording medium comprising Ta ₂ O ₅ as a main component and a material to which a glass-forming oxide is added, having a transmittance of 90% or more (wavelength 405 nm) and a refractive index of 1.8 to 2.4 (wavelength 405 nm). A sputtering target for forming a protective film. It is made of a material mainly composed of Ta ₂ O ₅ and added with a glass-forming oxide. It has a transmittance of 90% or more (wavelength 405 nm) and a refractive index of 1.8 to 2.4 (wavelength 405 nm). A sputtering target for forming a protective film for an optical information recording medium, which is amorphous.   The sputtering target according to claim 1 or 2, comprising a material to which 5 to 50 mol% of a glass-forming oxide is added. The sputtering target according to claim 1, wherein SiO ₂ is added as a glass forming oxide.   The sputtering target according to claim 1, wherein the relative density is 90% or more. Optical information having a transmittance of 90% or more (wavelength of 405 nm) and a refractive index of 1.8 to 2.4 (wavelength of 405 nm), characterized by being formed using the sputtering target according to claim 1. Protective film for recording medium and manufacturing method thereof.