TW201337011A - Oxide sputtering target and protection film for optical recording medium - Google Patents

Abstract

Provided are an oxide sputtering target which is used to form a film as an optical recording medium protection film, is used to form a flexible, difficult-to-crack film having high storage ability and is capable of using direct-current sputtering for having few particles, and a protection film for optical recording medium formed by using said sputtering target. The oxide sputtering target, relative to the total amount of metal, contains: more than 0.15at% of In, more than 7at% of Si, less than 39at% of the sum of In and Si, and the remainder containing Zn and inevitable impurities.

Description

Oxide sputtering target and protective film for optical recording medium

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

In recent years, with the high image quality of photographs or animations, the number of digits of data recorded in optical recording media has increased, and the capacity of recording media has been increased. Currently, as an optical recording medium with a high recording capacity, the second layer is composed of two layers. A Blu-ray Disc (registered trademark: hereinafter referred to as BD) having a recording capacity of 50 GB has been sold. In the future, the BD is expected to further increase the capacity, and the high-capacity research using the multilayer of the recording layer is actively carried out.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] JP-A-2009-26378

[Patent Document 2] JP-A-2005-228402

The above-mentioned past technologies still have the following problems.

In the recording medium of the type in which the organic dye is used in the recording layer, since the deformation of the recording layer is large as compared with the case where the inorganic material is used as the recording layer, it is adjacent to the dye as described in Paragraph No. 0085 of Patent Document 1. The protective layer must be low in hardness. Therefore, in the past, moderately soft ZnS-SiO ₂ or ITO was used.

However, as for ZnS-SiO ₂ , as described in Paragraph No. 0004 of Patent Document 2, when sulfur (S) is contained, sulfur reacts with the metal in the reflective film to lower the reflectance, and the storage property changes. Low disadvantages. Further, regarding ITO, there are many particles at the time of sputtering, which adversely affects the optical disk of the recording medium, and also makes it difficult to clean the production equipment, and there is a problem that productivity is deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to provide an oxide sputtering target which can be formed into a film for forming an optical recording medium protective film, which has high storage property, is soft and not easily broken, and can be oxidized by DC. The plated particles are also small, and a protective film for an optical recording medium produced using the sputtering target.

The present inventors have studied the ZnO-based sputtering target, and found that by adding SiO ₂ and In ₂ O ₃ to the raw material, it is possible to form a film having a small change in reflectance of the film and being soft and not easily broken by DC sputtering.

Therefore, the present invention has been made based on the above findings, and the following configuration is adopted in order to solve the above problems. In other words, the oxide sputtering target according to the first aspect of the invention is characterized in that the amount of In is 0.15 at% or more, Si: 7 at% or more, and the total of In and Si: 39 at% or less, and the balance is Zn with respect to the total metal component. And the inevitable impurities.

The oxide sputtering target is made of In: 0.15 at% or more, Si: 7 at% or more, and a total of In and Si: 39 at% or less with respect to the total metal component amount, and the balance is Zn and unavoidable impurities. Since the composition is composed of an oxide, the specific resistance is low, and DC sputtering can be stably performed, and the film can have a small change in reflectance, and has a high storage property and is soft and not easily broken.

Further, it is considered that the specific resistance of the target due to the generation of the carrier due to the solid solution of In in ZnO can be reduced, and the thermal diffusivity of the film formed film can be further improved and the thermal damage can be reduced.

In addition, when the content of In is set to 0.15 at% or more, the reason why the content of In is less than 0.15 at% is that DC sputtering is unstable, and film breakage is likely to occur. In addition, when the content of Si is 7 at% or more, the hardness of the film (indentation hardness to be described later) is 800 mgf/μm ² or more and becomes hard. In addition, when the total content of In and Si is 39 at% or less, the amount of In ₂ O ₃ or SiO ₂ added to the raw material is too large, and a large amount of composite oxide with ZnO is generated to increase the specific resistance of the target. , and DC sputtering is not possible.

The oxide sputtering target according to the second aspect of the invention is characterized in that, in the oxide sputtering target according to the first aspect of the invention, Si: 25 at% or more.

In other words, since the oxide sputtering target has a Si: 25 at% or more, a film having a hardness (indentation hardness) of 700 mgf/μm ² or less can be formed into a film which is soft and not easily broken.

The protective film for an optical recording medium according to the third aspect of the invention is characterized in that the amount of In: 0.15 at% or more, Si: 7 at% or more, In and Si with respect to the total metal component amount. The total amount is 39at% or less, and the rest is an oxide composed of Zn and unavoidable impurities.

In the protective film for an optical recording medium according to the third aspect of the invention, the protective film for an optical recording medium according to the third aspect of the invention has a Si: 25 at% or more.

Further, the protective film for an optical recording medium according to the fifth aspect of the invention is characterized in that the film is formed by sputtering using the oxide sputtering target of the first or second invention.

In other words, the protective film for an optical recording medium has a property of being small in reflectance change, high in storage property, and soft and not easily broken, and is suitable as a protective film of BD using a recording layer of an organic dye.

According to the present invention, the following effects can be achieved.

In other words, the oxide sputtering target according to the present invention has an In: 0.15 at% or more, Si: 7 at% or more, and a total of In and Si: 39 at% or less with respect to the total metal component amount, and the balance is Zn. And an oxide composed of components which are unavoidable impurities, so that DC sputtering can be stably performed, and a film having high storage stability and being soft and not easily broken can be formed.

Therefore, the protective film for an optical recording medium formed by the oxide sputtering target of the present invention is suitable as a dielectric protective film for BD using a recording layer of an organic dye.

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

The oxide sputtering target of the present embodiment is a sputtering target for forming a dielectric protective film laminated on a recording layer formed of an organic dye such as BD, and is set to be In with respect to the total metal component amount. : 0.15 at% or more, Si: 7 at% or more, and the total of In and Si: 39 at% or less, and the balance is composed of Zn and unavoidable impurities.

Moreover, for direct current (DC) sputtering, the specific resistance of the sputtering target should be 1 Ω. Below cm. In particular, for stable sputtering, it should be 0.1Ω. Below cm, it is more preferably 0.01Ω. Below cm.

In addition, the protective film for an optical recording medium which is formed by sputtering using the oxide sputtering target of the present embodiment is in the range of In: 0.15 at% or more and Si: 7 at%, similar to the total target component. In the above, the total of In and Si is 39 at% or less, and the rest is an oxide composed of a component composed of Zn and unavoidable impurities.

When an example of the method for producing the oxide sputtering target of the present embodiment is described in detail, zinc oxide, cerium oxide, indium oxide, and each raw material powder are first weighed to have a specific ratio.

The weighed raw material powder and its three times (by weight) zirconia balls (diameter: 5 mm) were fed into a container and wet-mixed by a ball mill for 24 hours. Further, in this case, for example, an alcohol is used as the solvent. Next, the obtained mixed powder is dried, and dried, for example, at a mesh of 250 μm, at 900 to 1250 ° C, preferably at 1000 to 1150 ° C for 2 to 9 hours, at a pressure of 150 to 350 kgf / cm ² under vacuum or inertness. Hot pressing in a gaseous environment, becoming a sputtering target.

[Examples]

The examples of the oxide sputtering target actually produced based on the above-described embodiment were evaluated and the results were explained.

[Examples]

Weigh zinc oxide (chemical formula: ZnO, D ₅₀ = μm), cerium oxide (chemical formula: SiO ₂ , D ₅₀ = 2 μm), indium oxide (chemical formula: In ₂ O ₃ , D ₅₀ =) at a specific ratio shown in Table 1. 11 μm) of each raw material powder.

The weighed raw material powder and its three times (by weight) zirconia balls (diameter: 5 mm) were fed into a container and wet-mixed by a ball mill for 24 hours. Further, in this case, an alcohol is used as the solvent. Next, the obtained mixed powder was dried, and then hot-pressed in a vacuum at a pressure of 350 kgf/cm ² at a temperature of 1100 ° C for 2 hours at a mesh of 250 μm to prepare a sputtering target of Examples 1 to 7. Further, the target size was 125 mm in diameter × 5 mm in thickness.

Further, as a comparative example, those who do not contain In ₂ O ₃ (Comparative Example 1) and those outside the setting range of the component composition ratio of the present invention (Comparative Examples 2 and 3) also have the compositions shown in Table 1. The sputtering target is also produced. Next, a conventional sputtering target of ZnS-SiO ₂ (Comparative Example 4) and ITO (Comparative Example 5) was prepared. ZnS-SiO ₂ is a ZSSO target (20 mol% SiO ₂ ) manufactured by Mitsubishi Materials Corporation, and ITO is an ITO target (10 wt% of SnO ₂ ) manufactured by Mitsubishi Materials Corporation.

Using the sputtering targets of the examples and the comparative examples, the protective films for optical recording media of Examples 1 to 7 and Comparative Examples 1 to 5 were formed by the following film formation conditions.

The metal composition of the sputtering target is shown in Table 2, and the protective film for optical recording media The metal composition is shown in Table 3.

<Film formation conditions>

. Power: Pulse DC500W (one, high frequency (RF) sputtering)

. Full pressure: 0.4Pa

. Sputtering gas: Ar = 47.5 sccm, O ₂ : 2.5 sccm (Comparative Example 4 is Ar = 50 sccm, O ₂ =0 sccm)

. Target substrate (TS) distance: 70mm

[Evaluation]

For each embodiment. In the sputtering target of the comparative example, the density ratio, specific resistance, abnormal discharge number, particle amount, film indentation hardness, film rupture, film specific resistance, XRD of the film, and reflectance were determined.

<density ratio measurement>

The density ratio is obtained by mechanically processing the sintered body to a specific size, and then measuring the weight to obtain the bulk density, and then calculating by dividing the theoretical density. Further, the theoretical density was determined based on the weight of the raw material as follows.

<Specific resistance measurement>

The specific resistance measurement of the sputtering target and the film was measured using a resistance measuring instrument LORESTA GP manufactured by Mitsubishi Chemical Corporation.

<Change in reflectivity>

A substrate obtained by sputtering an Ag _98.1 Nd _1.0 Cu _0.9 alloy on a polycarbonate to form a film of the following pigment described in Patent Document 1, and forming a film having a thickness of 14 nm under the above conditions and Comparative Example Protective Film. Subsequently, it was allowed to stand in a thermo-hygrostat at 80 ° C and 85% for 100 hours, and the change in reflectance before and after the measurement was measured. Further, the reflectance was measured by using an ultraviolet-visible spectrophotometer (V-550, manufactured by JASCO Corporation). Further, the reflectance for light having a wavelength of 405 nm was obtained.

. Pigment: a pigment formed on the substrate, an alloy azo dye A formed of a ligand A and a divalent Ni represented by the following structural formula, and an alloy formed of a complex B and a divalent Co. The azo dye B was mixed at a ratio of 70:30% by weight, and mixed with octafluoropentanol (OFP) to a 1.0% by weight mixed solution to form a film by a spin coating method. Further, in the spin coating, 1.5 g of the mixed solution was applied in a ring shape near the center of the substrate, and the substrate was rotated at 1200 rpm for 7 seconds to extend the dye, and then the film was spun at 9200 rpm for 3 seconds to coat the dye. . Further, after coating, the substrate was kept at 80 ° C for 1 hour, and the solvent OFP was removed by evaporation.

<Indentation hardness of film>

In the above-mentioned conditions, the substrate was 1737 glass manufactured by Corning Co., Ltd., and the film thickness was 500 nm, and the film was formed by an ultra-indentation hardness tester (ENT-1100a manufactured by ELIONIX Co., Ltd.) having an indentation load of 35 mgf. Further, the substrate was fixed in a device at 27 ° C, and the measurement was performed after one hour or more. Further, the average value measured at 10 points was used as the measured value.

<Film rupture>

Among the above conditions, a film having a thickness of 100 nm was formed on a PET film having a thickness of 0.1 mm, and after the film was bent 10 times, the film surface was observed at a magnification of 1000 times for the presence or absence of cracking.

<Abnormal discharge and particles>

The number of abnormal discharges which were sputtered for 12 hours under the above conditions was measured. Subsequently, the sputtering chamber is turned on to confirm the number of particles in the chamber.

<XRD of the film>

Preparation of sample: The sample is made of SiC-Paper (coarse grain 180) It was wet-tested and dried to be used as a measurement sample.

Device: manufactured by Rigaku Electric Co., Ltd. (RINT-Ultima/PC)

Tube ball: Cu

Tube voltage: 40kV

Tube current: 40mA

Scanning range (2θ): 5°~80°

Slit size: divergence (DS) 2/3 degrees, scattering (SS) 2/3 degrees, received light (RS) 0.8mm

Measuring step width: 0.02 degrees in 2θ

Scanning speed: 2 degrees per minute

Sample table rotation speed: 30rpm

The results of these evaluations are shown in Table 4.

As can be seen from the results, the specific resistance of the embodiment of the present invention is 0.1 Ω. Below cm, the number of abnormal discharges is extremely small and the amount of particles is also small. On the other hand, in Comparative Examples 1 and 4, the specific resistance was high and outside the measurable range, DC sputtering could not be performed. Moreover, the specific resistance of Comparative Example 2 was also high, and DC sputtering could not be performed. Therefore, Comparative Examples 1, 2, and 4 were formed by RF film formation. Comparative Example 5 had a large amount of particles. Further, the density of the examples and comparative examples of the present invention were both 90% or more.

Further, the indentation hardness of the film indicating the softness of the protective film was more than 800 mgf/μm ² in Comparative Examples 1 and 3, and film cracking occurred in Comparative Examples 1 and 3. On the other hand, in the examples of the present invention, each was 800 mgf/μm 2 or less, and a film softer than Comparative Examples 1 and 3 was obtained, and no film breakage occurred. Further, in Comparative Example 5 of the ITO film, film breakage occurred.

Further, regarding the change in the reflectance, Comparative Example 4 of ZnS-SiO ₂ was largely changed, and in the examples of the present invention, the examples of the present invention all had a small change rate of 1.0% or less, and high storage stability was obtained.

Further, the protective film of the present embodiment is amorphous at normal temperature.

Next, the results of X-ray diffraction (XRD) of the sputtering targets of Examples 1 and 3 of the present invention are shown in Fig. 1. Further, the upper stage of Fig. 1 is the first embodiment, and the lower stage is the third embodiment. As is understood from the results, a diffraction peak belonging to ZnO and a diffraction peak of Zn ₂ SiO ₄ belonging to a composite oxide of SiO ₂ and ZnO were detected, and the phases of ZnO and Zn ₂ SiO _{4 were} confirmed to exist.

Further, regarding the sputtering targets of Examples 1 and 3, the reflected electron image (CP) was observed by EPMA (field emission type electron beam probe) and the element distribution image showing the composition distribution of each element was observed. The above reflected electron image and element distribution image are respectively Shown in Figures 2 and 3.

Further, the element distribution image measured by EPMA is originally a color image, but since it is converted into a black-and-white image, the light-colored portion (white portion) of the shade is a higher concentration of the specific element.

From these images, it is understood that the sputtering targets of Examples 1 and 3 are formed of a phase of ZnO, Zn ₂ SiO ₄ and cerium oxide, and In is selectively dispersed in the ZnO phase.

Moreover, since the present invention is used as a sputtering target, the surface roughness is preferably 5.0 μm or less, more preferably 1.0 μm or less, the particle diameter is 20 μm or less, more preferably 10 μm or less, and the metal-based impurity concentration is 0.1 atom%. Hereinafter, it is more preferably 0.05 atom% or less, and the bending strength is 50 MPa or more, more preferably 100 MPa or more. Each of the above embodiments is a condition that satisfies the conditions.

Further, the technical scope of the present invention is not limited to the above-described embodiments and the above-described embodiments, and various changes can be made without departing from the spirit and scope of the invention.

For example, although the above embodiment and the above embodiment are subjected to pressure sintering by hot pressing, a HIP method (hot isostatic pressing method) may be employed as another method.

Fig. 1 is a view showing the results of X-ray diffraction (XRD) of an oxide sputtering target in an embodiment of the oxide sputtering target and the protective film for an optical recording medium of the present invention.

2 is a view showing the cross-sectional structure of an oxide sputtering target by EPMA in the first embodiment of the protective film for an oxide sputtering target and an optical recording medium of the present invention; The elemental distribution of each element.

Fig. 3 shows an element distribution image of each element of the cross-sectional structure of the oxide sputtering target by EPMA in Example 3 of the oxide sputtering target and the protective film for an optical recording medium of the present invention.

Claims (5)

An oxide sputtering target characterized by having an In: 0.15 at% or more, a Si: 7 at% or more, a total of In and Si: 39 at% or less, and the balance being Zn and an unavoidable impurity with respect to the total metal component. Made into. The oxide sputtering target of claim 1, wherein Si: 25 at% or more. A protective film for an optical recording medium characterized in that the amount of In is 0.15 at% or more, Si: 7 at% or more, and the total of In and Si: 39 at% or less with respect to the total metal component amount, and the balance is Zn and not An oxide composed of components that are avoided by impurities. A protective film for an optical recording medium according to claim 3, wherein Si: 25 at% or more. A protective film for an optical recording medium characterized by being sputter-deposited by using an oxide sputtering target as claimed in claim 1.