JP2013237893A - Oxide sputtering target and protective film for optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide sputtering target for forming a protective film for an optical recording medium, capable of forming a film that has excellent storage stability, is flexible and hardly breakable, and also the oxide sputtering target capable of being subjected to direct-current sputtering and containing few particles, and to provide a protective film for an optical recording medium, which is produced by using the same.SOLUTION: An oxide sputtering target is an oxidation product with a component composition including 0.1 atom% or more In, 12 atom% or more Cr, and the balance Zn with inevitable impurities, based on the total amount of all the metal components, wherein the total of In and Cr is 53 atom% or less.

Description

  The present invention relates to an oxide sputtering target for forming a protective film for an optical recording medium used for Blu-ray Disc (registered trademark) and the like, and to a protective film for an optical recording medium produced using the oxide sputtering target.

  In recent years, with the improvement of the picture quality of photographs and moving images, digital data when recording on an optical recording medium or the like has increased, and there has been a demand for an increase in the capacity of the recording medium. A Blu-ray Disc (registered trademark: hereinafter referred to as BD) having a capacity of 50 GB is on the market. In the future, it is desired to further increase the capacity of this BD, and research on increasing the capacity by increasing the number of recording layers has been actively conducted.

ZnS—SiO ₂ and ITO are known as a material for a protective film constituting a BD using an organic dye in the recording layer (see Patent Document 1). As a protective film having high storage stability, a ZnO-based protective film is known (see Patent Document 2). Furthermore, a ZnO—Cr ₂ O ₃ protective layer is known as a material for a protective film constituting a BD using an inorganic substance in the recording layer (see Patent Document 3).

JP 2009-26378 A JP 2005-228402 A Japanese Patent No. 4612689

The following problems remain in the conventional technology.
In the recording medium of the type using the organic dye for the recording layer, since the deformation of the recording layer is large compared to the case where the inorganic substance is used as the recording layer, as described in paragraph No. 0058 of Patent Document 1, The protective layer adjacent to the dye must have a low hardness. Therefore, conventionally, ZnS—SiO ₂ and ITO, which are moderately soft films, are employed.
However, as described in paragraph No. 0004 of Patent Document 2, when ZnS—SiO ₂ contains sulfur (S), sulfur reacts with the metal in the reflective film, resulting in a reflectivity. There is an inconvenience that the storage stability is lowered. In addition, ITO has many particles when it is sputtered, which adversely affects the disk of the recording medium, and the production equipment is difficult to clean, resulting in poor productivity.
Furthermore, since ZnO—Cr ₂ O ₃ used in a recording medium of a type using an inorganic substance in the recording layer is easily broken, when used in an organic dye type recording medium with a large deformation in the recording layer, A decrease in storage stability is expected. In addition, the ZnO—Cr ₂ O ₃ sputtering target has a high resistance, and direct current sputtering cannot be performed.

  The present invention has been made in view of the above-mentioned problems, and can be used for forming a protective film for an optical recording medium, which can form a film that is highly storable, soft and difficult to break, and that can be directly sputtered and has few particles. It is an object of the present invention to provide an object sputtering target and a protective film for an optical recording medium produced using the same.

The inventors of the present invention have made researches on a ZnO—Cr ₂ O ₃ -based sputtering target. By adding In ₂ O ₃ to the raw material, a film that is soft and hardly breaks is formed by direct current sputtering with little change in reflectance. I found out that I can do it.

  Therefore, the present invention has been obtained from the above findings, and the following configuration has been adopted in order to solve the above problems. That is, the oxide sputtering target according to the first invention contains In: 0.1 at% or more, Cr: 12 at% or more, and the total of In and Cr: 53 at% or less with respect to the total metal component amount, and the balance Is an oxide having a component composition of Zn and inevitable impurities.

  This oxide sputtering target contains In: 0.1 at% or more, Cr: 12 at% or more, and a total of In and Cr: 53 at% or less with respect to the total amount of metal components, with the balance being Zn and inevitable impurities. Since it is an oxide having a component composition, a stable direct current sputtering with a low specific resistance is possible, and a film having a small change in reflectivity, high storage stability, and being soft and difficult to break can be formed.

The reason why the content of In is 0.1 at% or more is that when it is less than 0.1 at%, direct current sputtering becomes unstable and film cracking is likely to occur. The reason why the Cr content is 12 at% or more is that when it is less than 12 at%, the hardness of the film (indentation hardness described later) becomes 800 mgf / μm ² or more and becomes hard. Furthermore, the reason why the total content of In and Cr is set to 53 at% or less is that if it exceeds 53 at%, In elutes before the target density reaches 90% or more during target production.

The protective film for an optical recording medium according to the second invention contains In: 0.1 at% or more, Cr: 12 at% or more, and a total of In and Cr: 53 at% or less with respect to the total amount of metal components, and the balance Is an oxide having a component composition of Zn and inevitable impurities.
The protective film for an optical recording medium according to the third invention is formed by sputtering using the oxide sputtering target according to the first invention.

  That is, these protective films for optical recording media are suitable as a protective film for BD using a recording layer of an organic dye, since the change in reflectance is small and the storage property is high and the film is soft and difficult to break. .

The present invention has the following effects.
That is, the oxide sputtering target according to the present invention contains In: 0.1 at% or more, Cr: 12 at% or more, and total of In and Cr: 53 at% or less with respect to the total amount of metal components, and the balance Is an oxide having a component composition consisting of Zn and inevitable impurities, so that stable direct current sputtering can be performed, and a film having high storage stability and soft and difficult to crack can be formed.
Therefore, the protective film for optical recording media formed with the oxide sputtering target of the present invention is suitable as a dielectric protective film for BD using an organic dye recording layer.

It is a graph which shows the X-ray-diffraction (XRD) result of an oxide sputtering target in the Example of the oxide sputtering target which concerns on this invention, and the protective film for optical recording media. In the Example of the oxide sputtering target which concerns on this invention, and the protective film for optical recording media, it is the element distribution image of each element which measured the cross-sectional structure | tissue of the oxide sputtering target by EPMA.

  Hereinafter, an embodiment of the oxide sputtering target and the protective film for an optical recording medium of the present invention will be described.

The oxide sputtering target of the present embodiment is a sputtering target for producing a dielectric protective film laminated on a recording layer formed of, for example, an organic dye of BD, and is In: It is an oxide having a component composition containing 0.1 at% or more, Cr: 12 at% or more, and a total of In and Cr: 53 at% or less, with the balance being Zn and inevitable impurities.
In order to perform direct current (DC) sputtering, the specific resistance of the sputtering target is desirably 1 Ω · cm or less. In particular, in order to perform stable sputtering, it is preferably 0.1 Ω · cm or less, and more preferably 0.01 Ω · cm or less.

  Moreover, the protective film for optical recording media formed by sputtering using the oxide sputtering target of the present embodiment is In: 0.1 at% or more, Cr: : 12 at% or more, total of In and Cr: 53 at% or less, and the balance is an oxide having a component composition consisting of Zn and inevitable impurities.

  If an example of the method of manufacturing the oxide sputtering target of this embodiment is explained in full detail, first, each raw material powder of zinc oxide, chromium oxide, and indium oxide will be weighed so that it may become a predetermined ratio.

The weighed raw material powder and 3 times its amount (weight ratio) of zirconia balls (diameter 5 mm) are put in a plastic container and wet mixed in a ball mill apparatus for 18 hours. In addition, alcohol is used for the solvent in this case, for example. Next, after drying the obtained mixed powder, for example, at 900 to 1350 ° C., desirably at 950 to 1200 ° C. for 1 to 9 hours, in a vacuum or an inert gas atmosphere at a pressure of 100 to 400 kgf / cm ^2. Hot press to obtain a sputtering target.

The result of having evaluated about the Example of the oxide sputtering target actually produced based on the said this embodiment is demonstrated.
[Example]
Zinc oxide (chemical formula: ZnO, D ₅₀ = 1 μm), chromium oxide (chemical formula: Cr ₂ O ₃ , D ₅₀ = 0.4 μm), and indium oxide (chemical formula: In ₂ O ₃ , D ₅₀ = 11 μm) Each raw material powder was weighed so as to have a predetermined ratio shown in Table 1.

The weighed raw material powder and 3 times its amount (weight ratio) of zirconia balls (diameter 5 mm) were placed in a plastic container and wet mixed in a ball mill apparatus for 18 hours. In addition, alcohol was used for the solvent in this case. Next, after drying the obtained mixed powder, it hot-pressed in vacuum at a pressure of 300 kgf / cm < ² > for 3 hours at 1100 degreeC, and produced the sputtering target of Examples 1-5. The target size was 125 mm diameter x 5 mm thickness. In addition, Table 1 shows whether or not In was eluted during hot pressing.

In addition, as a comparative example, the composition shown in Table 1 includes those that do not contain In ₂ O ₃ (comparative example 1) and those that are outside the setting range of the component composition ratio of the present invention (comparative examples 2 to 4). And the sputtering target was similarly produced on condition. Furthermore, conventional sputtering targets of ZnS—SiO ₂ (Comparative Example 5) and ITO (Comparative Example 6) were prepared. ZnS—SiO ₂ is a ZSSO target (20 mol% SiO ₂ ) manufactured by Mitsubishi Materials, and ITO is an ITO target (10 wt% SnO ₂ ) manufactured by Mitsubishi Materials.
Using the sputtering targets of these Examples and Comparative Examples, protective films for optical recording media of Examples 1 to 5 and Comparative Examples 1 to 6 were formed under the following film forming conditions.
Table 2 shows the metal composition of the sputtering target, and Table 3 shows the metal composition of the protective film for an optical recording medium.

<Film formation conditions>
・ Power supply: Pulse DC500W (partially, radio frequency (RF) sputtering)
・ Total pressure: 0.4Pa
Sputtering gas: Ar = 47.5 sccm, O ₂ : 2.5 sccm
-Target-substrate (TS) distance: 70 mm

"Evaluation"
Regarding the sputtering target of each of the examples and comparative examples, the density ratio, specific resistance, amount of particles, indentation hardness of the film, cracking of the film, and change in reflectance were determined.
<Density ratio measurement>
The density ratio was calculated by machining the sintered body to a predetermined size, measuring the weight to determine the bulk density, and dividing this by the theoretical density. The theoretical density was determined as follows based on the weight of the raw material.
<Specific resistance measurement>
The specific resistance of the sputtering target was measured using a resistance measuring instrument Loresta GP manufactured by Mitsubishi Chemical.

<Change in reflectance>
A substrate in which an Ag _98.1 Nd _1.0 Cu _0.9 alloy was sputtered on polycarbonate and the following dye described in Patent Document 1 was formed on the substrate, and each of the Examples and Comparative Examples was formed on the above-described conditions. A protective film having a thickness of 14 nm was formed. Then, it was left for 100 hours in a constant temperature and humidity chamber at 80 ° C. and 85%, and the change in reflectance before and after that was measured. In addition, the ultraviolet visible spectrophotometer (JASCO Corporation V-550) was used for the measurement of a reflectance. Moreover, the reflectance with respect to the light of wavelength 405nm was calculated | required.

-Dye: The dye formed on the substrate comprises a metal-containing azo dye A composed of a ligand A represented by the following structural formula and divalent Ni, a ligand B, and divalent Co. The metal-containing azo dye B was mixed at a ratio of 70:30 wt%, and a mixed solution diluted to 1.0 wt% with octafluoropentanol (OFP) was formed by spin coating. In spin coating, 1.5 g of the above mixed solution is applied in the vicinity of the center of the substrate, and the substrate is rotated at 1200 rpm for 7 seconds to stretch the dye, and then rotated at 9200 rpm for 3 seconds to shake off the dye. went. After coating, the OFP as the solvent was removed by evaporation by holding the substrate in an environment of 80 ° C. for 1 hour.

<Indentation hardness of film>
Under the above-mentioned conditions, the substrate was formed with 1737 glass made by Corning, the film thickness was 500 nm, the indentation load was 35 mgf, and measurement was performed with an ultra-fine indentation hardness tester (ENT-1100a, Elionix). The substrate was set in a 27 ° C. apparatus and measured after 1 hour or more had elapsed. In addition, the average value of 10-point measurement was made into the measured value.

<Membrane cracking>
Under the above-mentioned conditions, a film of 100 nm was formed on a PET film having a thickness of 0.1 mm, the film was bent 10 times, and then the surface of the film was observed with a microscope at a magnification of 1000 to check for cracks. .
<Particle>
Sputtering was performed for 12 hours under the above-described conditions, and then the sputtering chamber was released, and particles in the chamber were confirmed.
These evaluation results are shown in Table 4.

  As can be seen from these results, each of the examples of the present invention had a specific resistance of 0.1 Ω · cm or less and a small amount of particles. On the other hand, in Comparative Examples 1 and 5, the specific resistance was high and out of the measurable range, and DC sputtering could not be performed. Therefore, Comparative Examples 1 and 5 were formed by RF sputtering. In Comparative Example 2, since In was eluted, a desired target could not be produced. Furthermore, the comparative example 3 had a low density. In Comparative Examples 2 and 3, since the total content of In and Cr exceeds 53 at% with respect to the total amount of metal components, in the temperature range where In does not elute from the sintered body during hot pressing, the density of the sintered body Did not reach 90% or more, and In was eluted in a temperature range where 90% or more was achieved. In Comparative Example 6, the amount of particles was large. In all of the examples of the present invention, the density was 90% or more.

Further, the indentation hardness of the film showing the softness of the protective film exceeded 800 mgf / μm ² in Comparative Example 4, and the film was cracked. In Comparative Example 1, since the resistance was high and DC sputtering could not be performed, the film was formed by RF sputtering, but the film was cracked.
On the other hand, all of the examples of the present invention have 800 mgf / μm ² or less, and a soft film is obtained as compared with Comparative Example 4, and the film is not cracked. In Comparative Example 7, which is an ITO film, the film is cracked.
Furthermore, with respect to the change in reflectance, the comparative example 5 of ZnS-SiO ₂ is greatly changed, whereas the examples of the present invention all have a low change rate of 1.0% or less and high storage. Sex has been obtained.
Note that the protective film of this example is amorphous at room temperature.

Next, the results of X-ray diffraction (XRD) of the sputtering target of Example 4 of the present invention are shown in FIG. As can be seen from this result, the diffraction peak attributed to ZnO, the diffraction peak attributed to In ₂ O _3, and the diffraction attributed to Zn ₅ In ₂ O ₈ which is a composite oxide of ZnO and In ₂ O _3. Peaks were detected, confirming the presence of ZnO, In ₂ O ₃ and Zn ₅ In ₂ O ₈ phases.

Further, with respect to the sputtering target of Example 4, a reflected electron image (CP) and an element distribution image showing the composition distribution of each element were observed with EPMA (field emission electron beam probe). The reflected electron image and element distribution image are shown in FIG.
The element distribution image by EPMA is originally a color image, but is described after being converted into a black and white image, and thus a light and dark portion (relatively white portion) is a portion where the concentration of the predetermined element is high. .
From these images, a part of the sputtering target of Example 4 formed a composite oxide of ZnO and In ₂ O ₃ and a part of it formed a composite oxide of ZnO and Cr ₂ O _3. You can see that Further, oxides of zinc, indium, and chromium are also present, and are considered to be raw materials ZnO, In ₂ O ₃ , and Cr ₂ O ₃ that have not contributed to the formation of the composite oxide.

In order to use the present invention as a sputtering target, the surface roughness is 5.0 μm or less, more preferably 1.0 μm or less, the particle size is 20 μm or less, more preferably 10 μm or less, and the metal impurity concentration is 0.00. 1 atomic% or less, more preferably 0.05 atomic% or less, bending strength: 50 MPa or more, more preferably 100 MPa or more. Each of the above-described embodiments satisfies these conditions.
The technical scope of the present invention is not limited to the above-described embodiment and examples, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment and the above examples, pressure sintering is performed by hot pressing, but as another method, a HIP method (hot isostatic pressing method) or the like may be employed.

Claims (3)

  It is an oxide having a component composition containing In: 0.1 at% or more, Cr: 12 at% or more, and a total of In and Cr: 53 at% or less with the balance being Zn and inevitable impurities with respect to the total amount of metal components. An oxide sputtering target.   It is an oxide having a component composition containing In: 0.1 at% or more, Cr: 12 at% or more, and a total of In and Cr: 53 at% or less with the balance being Zn and inevitable impurities with respect to the total amount of metal components. A protective film for an optical recording medium.   A protective film for an optical recording medium, formed by sputtering using the oxide sputtering target according to claim 1.