JP2003155560A - Silver alloy sputtering target for forming reflection layer of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silver alloy sputtering target for forming an Ag alloy reflection layer of an optical recording medium such as an optical recording disk (CD-RW, DVD-RAM). SOLUTION: This sputtering target consists of: a silver alloy (1) having a composition containing, by mass, 0.5 to 5% Cu and 0.05 to 2% Ni, and the balance Ag; a silver alloy (2) containing one or more kinds selected form Ca, Be and Si by 0.005 to 0.05% in total in the silver alloy (1); a silver alloy (3) containing one or more kinds selected from Dy, La, Nd, Tb and Gd by 0.1 to 3% in total in the silver alloy (1); or a silver alloy (4) containing 0.5 to 5% Cu, 0.05 to 2% Ni and one or more kinds selected from Dy, La, Nd, Tb and Gd by 0.1 to 3% in total, and one or more kinds selected from Ca, Be and Si by 0.005 to 0.05% in total in the silver alloy (1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording disk (CD-RW, DVD-RAM) for reproducing or recording / reproducing / erasing information signals such as audio, video and characters by using a laser beam such as a semiconductor laser. ) Etc. for forming a semitransparent reflective layer or a reflective layer (hereinafter, both are referred to as a reflective layer), which is a constituent layer of an optical recording medium, by a sputtering method.

[0002]

2. Description of the Related Art Conventionally, optical recording disks (CD-RW, D
An Ag or Ag alloy reflective layer is used as a reflective layer of an optical recording medium such as a VD-RAM), and this Ag or Ag alloy reflective layer has a high reflectance in a wide wavelength range of 400 to 830 nm, and particularly optical recording. It is said that it is suitable because it has a large reflectance with respect to a laser beam having a short wavelength used for high density recording of a medium. It is known that the Ag or Ag alloy reflective layer is formed by sputtering a target made of Ag or an Ag alloy such as an Ag-Cu alloy or an Ag-Ni alloy (JP-A-57). -186244, and Japanese Patent Laid-Open No. 2001-35014).

[0003]

However, even in an optical recording medium, a phase change recording material is used for the recording layer, and repeated recording / recording is performed.
In the case of an optical recording medium that reproduces and erases,
As the number of repetitions of erasing increases, Ag or A
The reflectivity of the g-alloy reflective layer was lowered, and sufficient recording / reproducing durability could not be obtained for a long period of time. As one of the causes of this, when recording / reproducing / erasing is repeatedly performed on the optical recording medium, the Ag reflecting layer is repeatedly heated and cooled by the irradiation of the laser beam, whereby the Ag reflecting layer is recrystallized and the crystal grains become coarse. By doing so, it was found that the reflectance decreases.

[0004]

Therefore, the present inventors have conducted research to obtain an Ag alloy reflective layer in which the reflectance of the reflective layer is less likely to decrease even if the number of recording / reproducing / erasing is increased. It was As a result, (a) the silver alloy reflective layer obtained by sputtering using a target made of a silver alloy in which Cu and Ni were added to Ag was prepared from a conventional Ag, Ag-Cu alloy or Ag-Ni alloy. In comparison with the silver alloy reflective layer formed by sputtering the target, the crystal grains are less likely to coarsen even after being repeatedly heated and cooled by the repeated irradiation of the laser beam.
The composition of the silver alloy reflection layer containing both i and Cu is Cu: 0.
5 to 5% by mass, Ni: 0.05 to 2% by mass, with the balance being preferably Ag, (b) Cu: 0.5 to 5% by mass, Ni: 0.05 to 2% by mass. In addition, by sputtering using a silver alloy target having a composition containing one or more selected from Ca, Be, and Si: 0.005 to 0.05 mass% and the balance being Ag. The obtained silver alloy reflective layer is less likely to have crystal grains coarsened even when subjected to repeated heating and cooling associated with repeated irradiation of a laser beam, and therefore, there is very little decrease in reflectance even after long-term use, (C) Cu: 0.5 to 5 mass%, Ni: 0.
05 to 2 mass%, further Dy, La, Nd, T
b, a total of one or more selected from Gd: 0.
The silver alloy reflective layer obtained by sputtering using a silver alloy target having a composition containing 1 to 3% by mass and the balance being Ag has crystal grains even when subjected to repeated heating and cooling due to repeated irradiation of a laser beam. Is less likely to coarsen, and therefore, the decrease in reflectance is extremely small even after long-term use, (d) Cu: 0.5 to 5 mass%,
Ni: A silver alloy having a composition containing 0.05 to 2 mass% and the balance being Ag, and a total of one kind or two or more kinds selected from Ca, Be, and Si: 0.005 to 0.05 mass%. Silver alloy reflective layer obtained by sputtering using a silver alloy target containing at least one kind selected from Dy, La, Nd, Tb, and Gd, or a total of 0.1 to 3 mass%. However, the research result that the same effect can be obtained was obtained.

The present invention was made on the basis of the results of such research. (1) Cu: 0.5 to 5% by mass,
Ni: 0.05 to 2% by mass, the balance being Ag alloy sputtering target for forming a reflective layer of an optical recording medium made of a silver alloy having a composition of Ag, (2) Cu: 0.5 to 5% by mass, Ni: 0.05 to 2% by mass, and further C
a, Be, Si, or a total of one or more selected from: 0.005 to 0.05% by mass, with the balance being Ag.
A silver alloy sputtering target for forming a reflective layer of an optical recording medium, which is composed of a silver alloy having a composition of (3) Cu: 0.5
-5% by mass, Ni: 0.05-2% by mass, and one or more kinds selected from Dy, La, Nd, Tb, Gd in total: 0.1-3% by mass. A silver alloy sputtering target for forming a reflective layer of an optical recording medium, which is composed of a silver alloy having a balance of Ag, (4) Cu:
0.5 to 5% by mass, Ni: 0.05 to 2% by mass, and one or two selected from Ca, Be and Si.
Total of seeds or more: contains 0.005-0.05 mass%,
Furthermore, a reflection layer of an optical recording medium containing a silver alloy having a composition of 0.1 to 3 mass% of one or more selected from Dy, La, Nd, Tb, and Gd, and the balance being Ag. The present invention is characterized by a silver alloy sputtering target for forming.

The sputtering targets for forming the silver alloy reflective layer of the present invention each have a purity of 99.99% by mass or more as high purity Ag and high purity C as raw materials.
u, and purity: Ni, Dy, L of 99.9 mass% or more
a, Nd, Tb and Gd are prepared, these raw materials are melted in a high vacuum or an inert gas atmosphere, and the obtained molten metal is cast in a vacuum or an inert gas atmosphere to prepare an ingot. It can be manufactured by hot working and then mechanical working.

For Ca, Be and Si, which have almost no solid solution in Ag, Ag is blended so that the concentration of each element becomes 0.20% by mass, and then dissolved by high-frequency vacuum melting to dissolve. After filling Ar gas until the post-reactor pressure reaches atmospheric pressure, it is cast in a graphite mold to form Ca, Be and S.
A mother alloy of Ag containing i was produced, and similarly, for Ni having little solid solution in Ag, Cu was blended so that the concentration of Ni was 5 to 95% by mass and then melted by high frequency vacuum melting. After melting and casting in a graphite mold in a vacuum atmosphere, N
By preparing a master alloy of Cu containing i, adding these master alloys together with Cu if necessary, and melting and casting, an ingot is prepared, and the obtained ingot is hot worked and then machined. It can be manufactured.

Next, the reason why the component composition in the reflective layer made of the Ag alloy of the present invention and the sputtering target for forming the reflective layer made of the Ag alloy is limited as described above will be explained.

Cu: Cu has the effects of forming a solid solution with Ag to increase the strength of crystal grains, prevent recrystallization of crystal grains, and suppress a decrease in reflectance of the reflective layer formed by sputtering. However, even if Cu is included in an amount of less than 0.5% by mass, it is not possible to prevent recrystallization of sufficient crystal grains, and therefore it is not possible to prevent a decrease in reflectance of the reflective layer. If the content exceeds the above range, the internal stress of the Ag alloy reflective layer formed by sputtering increases, and the reflective layer is easily peeled off, which is not preferable. Therefore, the content of these Cu contained in the Ag alloy reflective layer and the sputtering target for forming this Ag alloy reflective layer is 0.5 to 0.5.
It was set to 5% by mass (more preferably 1.0 to 3% by mass).

Ni: Ni hardly forms a solid solution with Ag,
By precipitating at the crystal grain boundaries, the binding of the crystal grains is prevented, the crystal grains of the reflective layer are prevented from being recrystallized, and the reflectance of the reflective layer formed by sputtering is reduced. , Ni is less than 0.05% by mass, no remarkable effect can be obtained. On the other hand, if Ni is more than 2% by mass, the film stress is increased and the film is cracked immediately after sputtering, which is not preferable. Therefore, the content of these Ni contained in the Ag alloy reflective layer and the sputtering target for forming the Ag alloy reflective layer is 0.0.
It is set to 5 to 2% by mass (more preferably 0.1 to 1.5% by mass).

Ca, Be, Si: These components, like Ni, hardly form a solid solution in Ag and precipitate at the crystal grain boundaries to prevent the bonding of the crystal grains to each other, thereby recrystallizing the Ag alloy reflection layer. Although it is a component that further promotes prevention, even if the total amount of one or more of these components is less than 0.005% by mass, no remarkable effect can be obtained, while one or more of these components are If the total content exceeds 0.05% by mass, the target remarkably hardens, and it becomes difficult to manufacture the target, which is not preferable. Therefore, the content of these components contained in the Ag alloy reflective layer and the sputtering target for forming this Ag alloy reflective layer is 0.
005 to 0.05 mass% (more preferably 0.010 to
0.035% by mass).

Dy, La, Nd, Tb, Gd: These components form an intermetallic compound at the crystal grain boundary by reaction with Ag to prevent the crystal grains from binding to each other and recrystallize the Ag alloy reflection layer. Although it is a component that further promotes prevention, a remarkable effect cannot be obtained even if the total amount of one or more of these components is less than 0.1% by mass. On the other hand, if one or more of these components are contained, If the total content exceeds 3% by mass, the target remarkably hardens, and it becomes difficult to manufacture the target, which is not preferable. Therefore, the content of these components contained in the Ag alloy reflective layer and the sputtering target for forming the Ag alloy reflective layer is 0.1 to 3% by mass (more preferably 0.2 to 1.5% by mass). Specified.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Example 1 As raw materials, high-purity Ag and high-purity Cu each having a purity of 99.99% by mass or more were prepared. Furthermore, since Ni has almost no solid solution in Ag, Ni is melted together with Cu in a high-frequency vacuum melting furnace and cast in a graphite mold to prepare N in advance.
A Cu master alloy containing i was prepared and prepared as a raw material. The prepared Cu mother alloy containing Ag, Cu and Ni was melted in a high frequency vacuum melting furnace, and the resulting melt was cast in a graphite mold in an Ar gas atmosphere to produce an ingot. After heating for 2 hours, rolling, then machining: Diameter: 1
The targets 1 to 9 of the present invention, the comparative targets 1 to 3 and the conventional targets 1 and 2 having the composition of components shown in Table 1 were produced having dimensions of 25 mm and thickness: 5 mm.

The targets 1 to 9 of the present invention, the targets 1 to 3 for comparison, and the targets 1 and 2 for related art are soldered to backing plates made of oxygen-free copper, mounted on a DC magnetron sputtering apparatus, and then evacuated by a vacuum exhaust apparatus. 1 × 10 ^-4 Pa inside the DC magnetron sputtering system
After evacuation to Ar gas, Ar gas is introduced to obtain a sputtering gas pressure of 1.0 Pa, and then the target is 10
A direct current sputtering power of 0 W was applied to generate plasma between the target and a glass substrate having a diameter of 30 mm and a thickness of 0.5 mm, which was placed in parallel with the target at a distance of 70 mm, facing the target. , Thickness: 1
An Ag alloy reflective film of 00 nm was formed.

The reflectance of each Ag alloy reflective film thus formed immediately after its formation was measured by a spectrophotometer. After that, each formed Ag alloy reflective film was kept in a constant temperature and temperature chamber at a temperature of 80 ° C. and a relative humidity of 85% for 200 hours.
The reflectance was measured again under the same conditions. From the obtained reflectance data, the reflectances at wavelengths of 400 nm and 650 nm were obtained, and the results are shown in Table 1 to evaluate the recording / reproducing durability as a reflective film of an optical recording medium.

[0015]

[Table 1]

From the results shown in Table 1, the reflective layers obtained by sputtering the targets 1 to 9 of the present invention according to the present invention were used for the sputtering using the comparative targets 1 to 3 and the conventional targets 1 and 2. It can be seen that, compared with the reflective layer obtained by performing the above step, the decrease in reflectance after 200 hours of holding in a constant temperature and temperature chamber at a temperature of 80 ° C. and a relative humidity of 85% is small.

Example 2 Ca, Be and Si having a purity of 99.9% by mass or more were prepared as raw materials. Since Ca, Be and Si have almost no solid solution in Ag, the concentration of each element is 0.20.
After blending Ag so that the content of the mixture becomes% by mass, it is melted by high-frequency vacuum melting, and after melting, Ar gas is filled until the pressure in the furnace becomes atmospheric pressure, and then cast in a graphite mold to prepare C in advance.
A master alloy of Ag containing a, Be or Si was prepared. These master alloys were added to Ag together with the Cu master alloy containing Cu and Ni prepared in Example 1 and melted and cast to prepare an ingot.
After heating at 0 ° C. for 2 hours, rolling, and then machining, the targets 10 to 27 of the present invention having dimensions of diameter: 125 mm, thickness: 5 mm and having the composition of components shown in Tables 2 to 3 are obtained. Manufactured.

With respect to the targets 10 to 27 of the present invention thus obtained, an Ag alloy reflection film having a thickness of 100 nm was formed on the glass substrate surface in the same manner as in Example 1, and each Ag alloy reflection film was formed. The reflectance immediately after was measured with a spectrophotometer. After that, each Ag alloy reflective film thus formed was subjected to temperature:
After holding in a constant temperature and constant temperature chamber at 80 ° C. and a relative humidity of 85% for 200 hours, the reflectance was measured again under the same conditions. From the obtained reflectance data, wavelengths: 400 nm and 65
The respective reflectances at 0 nm were obtained, and the results are shown in Tables 3 to 4 to evaluate the recording / reproducing durability as a reflective film of the optical recording medium.

[0019]

[Table 2]

[0020]

[Table 3]

From the results shown in Tables 2 to 3, the reflective layers obtained by sputtering using the targets 10 to 27 of the present invention of the present invention were prepared using the conventional targets 1 and 2 shown in Table 1. Compared with the reflective layer obtained by sputtering, temperature: 80 ° C., relative humidity:
It can be seen that there is little decrease in reflectance after 200 hours of holding in an 85% constant temperature constant temperature chamber. However, comparison target 4 ~
As can be seen from FIG. 7, when Ca, Be and Si are contained in a total amount of more than 0.05 mass%, it cannot be formed due to cracking during rolling.

Example 3 Purity as raw material: Dy, La, N having a purity of 99.9 mass% or more
d, Tb and Gd were prepared, and these raw materials were added to Ag together with the Cu mother alloy containing Cu and Ni prepared in Example 1 and the Ag mother alloy containing Ca, Be or Si prepared in Example 2. Melted in a high-frequency vacuum melting furnace, cast the resulting melt in a graphite mold in an Ar gas atmosphere to produce an ingot, and heat the obtained ingot at 600 ° C. for 2
After being heated for an hour, rolled and then machined to have a diameter of 125 mm and a thickness of 5 mm.
The target 28 of the present invention having the component composition shown in FIG.
52 and comparative targets 8-13 were manufactured.

Each of the targets 28 to 52 of the present invention and the targets 8 to 13 of the present invention is soldered to a backing plate made of oxygen-free copper, mounted on a DC magnetron sputtering device, and the inside of the DC magnetron sputtering device is vacuum exhausted. 1 × 10 ^{- 4} was evacuated to Pa, A
Introducing r gas to adjust the sputtering gas pressure to 1.0 Pa, and subsequently applying DC sputtering power of 100 W to the target with a DC power source, the target was opposed to the target, and the target was placed in parallel with the target with an interval of 70 mm. Diameter: 30m
Plasma was generated between a glass substrate having a thickness of 0.5 mm and a thickness of 0.5 mm and the target to form an Ag alloy reflective film having a thickness of 100 nm.

The reflectance of each Ag alloy reflective film thus formed immediately after the film formation was measured by a spectrophotometer. After that, each formed Ag alloy reflective film was kept in a constant temperature and temperature chamber at a temperature of 80 ° C. and a relative humidity of 85% for 200 hours.
The reflectance was measured again under the same conditions. From the obtained reflectance data, the reflectances at wavelengths of 400 nm and 650 nm were determined, and the results are shown in Tables 4 to 6 to evaluate the recording / reproducing durability as a reflective film of an optical recording medium.

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

From the results shown in Tables 4 to 6, the reflective layers obtained by performing the sputtering using the targets 28 to 52 of the present invention were obtained by using the conventional targets 1 and 2 shown in Table 1. Compared with the reflective layer obtained by sputtering, temperature: 80 ° C., relative humidity:
It can be seen that there is little decrease in reflectance after 200 hours of holding in an 85% constant temperature constant temperature chamber. However, comparison target 8 ~
As can be seen from No. 13, when the total content of Dy, La, Nd, Tb and Gd is more than 3% by mass, cracking occurs during rolling and it becomes impossible to form.

Example 4 Cu and Ni prepared in Example 1 prepared in Example 1
A Cu master alloy containing Si, a master alloy containing Ca, Be and Si prepared in Example 2, and D prepared in Example 3
Using y, La, Nd, Tb and Gd, targets 53 to 64 of the present invention having the component composition shown in Table 7 were prepared, and these targets were formed on the surface of the glass substrate in the same manner as in Example 1 to have a thickness of 100 nm. An Ag alloy reflective film was formed, and the reflectance immediately after the formation of each Ag alloy reflective film was measured by a spectrophotometer. After that, each formed Ag alloy reflective film was placed in a thermostat chamber at a temperature of 80 ° C. and a relative humidity of 85%.
After holding for 00 hours, the reflectance was measured again under the same conditions. From the obtained reflectance data, the reflectances at wavelengths of 400 nm and 650 nm were obtained, and the results are shown in Table 7 to evaluate the recording / reproducing durability as a reflective film of an optical recording medium.

[0030]

[Table 7]

From the results shown in Table 7, the reflective layers obtained by carrying out the sputtering using the targets 53 to 64 of the present invention are the conventional targets 1 to 1 shown in Table 1.
Compared with the reflective layer obtained by performing the sputtering using No. 2, the reflectance at the wavelengths of 400 nm and 650 nm: 80 ° C., the relative humidity: 85%, and the reflectance decreases after 200 hours in a thermostatic chamber. It turns out that there are few.

[0032]

As described above, the reflective layer produced by using the silver alloy sputtering target for forming the reflective layer of the optical recording medium of the present invention uses the conventional silver alloy sputtering target for forming the reflective layer of the optical recording medium. Compared with the reflective layer prepared by the above, there is less decrease in reflectance due to aging, and it is possible to manufacture an optical recording medium that can be used for a long period of time.
It can greatly contribute to the development of the media industry.

Claims (5)

[Claims] 1. Cu: 0.5 to 5 mass%, Ni: 0.05
A silver alloy sputtering target for forming a reflection layer of an optical recording medium, characterized in that the silver alloy sputtering target contains ˜2% by mass and the balance is Ag. 2. Cu: 0.5-5% by mass, Ni: 0.05
To 2% by mass, and one or more kinds selected from Ca, Be, and Si in total: 0.005 to 0.05
A silver alloy sputtering target for forming a reflective layer of an optical recording medium, which is made of a silver alloy having a composition containing mass% and the balance being Ag. 3. Cu: 0.5-5% by mass, Ni: 0.05
˜2% by mass, further containing Dy, La, Nd, Tb,
Total of one or more selected from Gd: 0.1
A silver alloy sputtering target for forming a reflective layer of an optical recording medium, which comprises a silver alloy having a composition containing 3 mass% and the balance being Ag. 4. Cu: 0.5-5% by mass, Ni: 0.05
To 2% by mass, and one or more kinds selected from Ca, Be, and Si in total: 0.005 to 0.05
%, Dy, La, Nd, Tb, Gd
A silver alloy sputtering for forming a reflective layer of an optical recording medium, characterized in that it comprises a silver alloy having a composition of one or two or more selected from 0.1 to 3 mass% and the balance being Ag. target. 5. A reflective layer of an optical recording medium produced by using the silver alloy sputtering target according to claim 1.