JP2003160827A - Silver-alloy sputtering target for forming reflective layer on optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silver-alloy sputtering target for forming a reflective layer on an optical recording medium such as optical recording disks (CD-RW and DVD-RAM). <P>SOLUTION: This sputtering target comprises (1) a silver alloy having a composition including 1-20 mass% Zn, further 0.005-0.05 mass% in total of one or more selected among Ca, Be, or Si, and the balance Ag, (2) a silver alloy having a composition including 1-20 mass% Zn, further 0.1-3 mass% in total of one or more selected among Dy, La, Nd, Tb, or Gd, and the balance Ag, or (3) a silver alloy having a composition including 1-20 mass% Sn, further 0.005-0.05 mass% in total of one or more selected among Ca, Be, and Si, further 0.1-3 mass% in total of one or more selected among Dy, La, Nd, Tb, or Gd, and the balance Ag. <P>COPYRIGHT: (C)2003,JPO

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 Ag-Zn alloy (see JP 2001-35014 A).

[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-Zn alloy reflective layer was lowered, and sufficient recording / reproduction 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) Ag-Z in which Zn: 1 to 20 mass% was added to Ag
Silver alloy obtained by sputtering using a silver alloy target having a composition in which n alloy contains one or more kinds selected from Ca, Be, and Si in total: 0.005 to 0.05 mass% The reflective layer is different from the conventional silver or silver alloy reflective layer obtained by sputtering using a target made of Ag or Ag-Zn alloy,
Even if it is repeatedly heated and cooled due to the repeated irradiation of the laser beam, the crystal grains are rarely coarsened, and therefore, the reflectance is hardly reduced even if it is used for a long period of time.
(B) Ag-Z in which Zn: 1 to 20 mass% is added to Ag
n alloy selected from Dy, La, Nd, Tb, Gd 1
Or a total of two or more kinds: a silver alloy reflective layer obtained by sputtering using a silver alloy target having a composition containing 0.1 to 3 mass% is made of a conventional Ag or Ag-Zn alloy. Compared to the silver or silver alloy reflective layer obtained by sputtering using a target,
Even if it is repeatedly heated and cooled due to repeated irradiation of the laser beam, the crystal grains are rarely coarsened, so that there is very little decrease in reflectance even after long-term use.
(C) Ag-Z in which Zn: 1 to 20 mass% is added to Ag
n alloy, and a total of one or more selected from Ca, Be and Si: 0.005 to 0.05 mass% and D
1 or 2 selected from y, La, Nd, Tb and Gd
Since the research results have been obtained, the same effect can be obtained with a silver alloy reflection layer obtained by sputtering using a silver alloy target containing a total of at least one species: 0.1 to 3% by mass. is there.

The present invention was made on the basis of the results of such research, and contains (1) Zn: 1 to 20 mass%, and one or more kinds selected from Ca, Be and Si. A total of 0.005 to 0.05 mass% and the balance is Ag alloy sputtering target for forming a reflective layer of an optical recording medium, which is made of a silver alloy having a composition of Ag,
(2) Containing Zn: 1 to 20% by mass, and further containing Dy, L
Silver for forming a reflective layer of an optical recording medium, which is composed of a silver alloy having a composition of 0.1 to 3 mass% and one or two or more kinds selected from a, Nd, Tb, and Gd, the balance being Ag. Alloy sputtering target, (3) Zn: containing 1 to 20 mass%, further containing one or more kinds selected from Ca, Be, Si: 0.005 to 0.05 mass%, and Dy, La, Nd, Tb, Gd, 1 type or 2 types or more of total: 0.1-3 mass% is contained, and the balance forms the reflection layer of the optical recording medium which consists of a silver alloy of the composition which is Ag. The silver alloy sputtering target for use is characterized.

The sputtering target for forming the silver alloy reflective layer of the present invention has a purity of 99.
99% by mass or more of high purity Ag and 99.9% by mass or more of purity of Zn, Dy, La, Nd, Tb and Gd are prepared, and these raw materials are dissolved in a high vacuum or an inert gas atmosphere to obtain It can be manufactured by casting the obtained molten metal in a vacuum or an inert gas atmosphere to produce an ingot, hot working these ingots, and then machining them.

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 produce a master alloy of Ag containing Ca, Be and Si, and this master alloy is added to Ag together with Zn and melted. Then, an ingot can be produced by casting, and the obtained ingot can be manufactured by hot working and then mechanical working.

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.

Zn: Zn 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 Zn is contained in an amount of less than 1% by mass, it is not possible to prevent sufficient recrystallization of crystal grains, and therefore it is not possible to prevent a decrease in reflectance of the reflective layer, while Zn exceeds 20% by mass. If it is contained, the internal stress of the Ag alloy reflective layer formed by sputtering becomes large, and an intermetallic compound is formed in the crystal grains and / or in the crystal grain boundaries during the production of the target, and cracking is likely to occur, which is not preferable. Therefore, the Z alloy contained in the Ag alloy reflective layer and the sputtering target for forming this Ag alloy reflective layer is not included.
The content of n is 1 to 20% by mass (more preferably 5 to 15%).
Mass%).

Ca, Be, Si: These components hardly dissolve in Ag and precipitate at the crystal grain boundaries to prevent the crystal grains from binding to each other and further promote the prevention of recrystallization of the Ag alloy reflection layer. It is one of these ingredients or 2
Even if the total amount of the above components is less than 0.005% by mass, no remarkable effect can be obtained. On the other hand, if the total amount of one or more of these components exceeds 0.05% by mass, the target is significantly hardened. However, it is not preferable because it is difficult to manufacture the target. Therefore, the Ag alloy reflective layer and this A
The content of these components contained in the sputtering target for forming the g alloy reflection layer is 0.005 to 0.0.
It was set to 5% by 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, even if the total content of one or more of these components is less than 0.1% by mass, no remarkable effect can be obtained. On the other hand, one or two of these components are not obtained. If the above total content exceeds 3% by mass, the target is significantly hardened and the target is difficult to manufacture, 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 0.1 to 3.
The content is set to the mass% (more preferably 0.2 to 1.5 mass%).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Example 1 Purity as raw material: high purity Ag of 99.99 mass% or more,
Also, all of them have a purity of 99.9% by mass or more, Zn, Ca,
Be and Si were prepared. Ca, Be and Si are A
Since there is almost no solid solution in g, Ag is blended so that the concentration of each element is 0.20% by mass, and then it is melted in a high frequency vacuum melting furnace, and the pressure in the furnace after melting is atmospheric pressure. A mother alloy of Ag containing Ca, Be and Si was prepared in advance by filling Ar gas until it was filled and then casting in a graphite mold. This mother alloy was added to Ag together with Zn and melted and cast to form an ingot. The obtained ingot was heated at 600 ° C. for 2 hours, rolled, and then machined to have a diameter of 125 mm and a thickness of 125 mm. Length: 5 mm
Inventive targets 1 to 18, comparative targets 1 to 4 and conventional targets 1 and 2 having the dimensions of No. 1 and the composition shown in Tables 1 and 2 were produced.

The targets 1 to 9 of the present invention, the comparative targets 1 to 4 and the conventional targets 1 and 2 are each soldered to a backing plate 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
A 00 nm Ag and Ag alloy reflective film was formed.

The reflectance of the Ag and Ag alloy reflective films thus formed immediately after the film formation was measured by a spectrophotometer. After that, the formed Ag and Ag alloy reflective film is heated to a temperature of 80 ° C. and a relative humidity of 85% in a thermo-hygrostat at 200.
After holding for a time, the reflectance was measured again under the same conditions.
From the obtained reflectance data, wavelengths: 400 nm and 6
Each reflectance at 50 nm was obtained, and the results are shown in Tables 1-2.
The recording and reproducing resistance was evaluated as a reflective film of the optical recording medium as shown in FIG.

[0015]

[Table 1]

[0016]

[Table 2]

From the results shown in Tables 1 and 2, the reflective layers obtained by performing the sputtering using the targets 1 to 18 of the present invention are conventional targets 1 to 2.
It can be seen that, as compared with the reflective layer obtained by performing the sputtering using, the decrease in reflectance after 200 hours of holding in a thermo-hygrostat at a temperature of 80 ° C. and a relative humidity of 85% was less. However, Zn, C are out of the scope of the present invention.
Comparative targets 1 to 4 containing a large amount of a, Be and Si
It can be seen that in the case of, cracking occurs or the material becomes hard and cannot be molded.

Example 2 As a raw material, high-purity Ag having a purity of 99.99 mass% or more and Zn, Dy, La, N having a purity of 99.9 mass% or more.
d, Tb, and Gd were prepared, these raw materials were melted in a high-frequency vacuum melting furnace, and the resulting melt was cast in a graphite mold in an Ar gas atmosphere to prepare an ingot. The targets 19 to 43 of the present invention and the comparative targets 5 to 5 having dimensions of diameter: 125 mm, thickness: 5 mm and having the component compositions shown in Tables 3 to 5 by heating for a time, rolling and then machining. 10
Was manufactured.

Each of the targets 19 to 43 of the present invention and the targets 5 to 10 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 thermo-hygrostat at a temperature of 80 ° C. and a relative humidity of 85% for 200 hours.
The reflectance was measured again under the same conditions. Each reflectance at wavelengths of 400 nm and 650 nm was determined from the obtained reflectance data, and the results are shown in Tables 3 to 5 to evaluate the recording / reproducing durability as a reflective film of an optical recording medium.

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

[Table 5]

From the results shown in Tables 3 to 5, the reflective layer obtained by performing the sputtering using the targets 19 to 43 of the present invention was obtained by using the conventional targets 1 and 2 shown in Table 2. 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 and humidity chamber. However, comparison target 5
As can be seen from No. 10, when the total content of Dy, La, Nd, Tb and Gd is more than 3% by mass, cracking occurs during rolling and molding cannot be performed.

Example 3 A table using the high purity Ag and the mother alloy of Ag containing Zn, Ca, Be and Si prepared in Example 1 and Dy, La, Nd, Tb and Gd prepared in Example 2 Targets 44 to 55 of the present invention having the component composition shown in No. 6 were produced, and Ag alloy reflection films with a thickness of 100 nm were formed on the glass substrate surface for these targets in the same manner as in Example 1, and each Ag alloy reflection film was formed. The reflectance immediately after the film formation was measured with a spectrophotometer. After that, each formed Ag alloy reflective film was kept in a thermo-hygrostat at a temperature of 80 ° C. and a relative humidity of 85% for 200 hours, and then 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 Table 6.
The recording and reproducing resistance was evaluated as a reflective film of the optical recording medium as shown in FIG.

[0026]

[Table 6]

From the results shown in Table 6, the reflective layers obtained by sputtering using the targets 44 to 55 of the present invention are the conventional targets 1 to 1 shown in Table 2.
Compared with the reflective layer obtained by performing the sputtering using No. 2, the reflectance at the wavelengths: 400 nm and 650 nm: 80 ° C. and the relative humidity: 85% after being kept in a constant temperature and humidity chamber for 200 hours, the decrease in the reflectance. It turns out that there are few.

[0028]

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 (4)

[Claims] 1. Zn: 1 to 20% 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 the composition 2. Zn: 1 to 20% by mass, and further D
1 or 2 selected from y, La, Nd, Tb and Gd
Total of seeds or more: 0.1 to 3 mass% is contained, and the balance is Ag
A silver alloy sputtering target for forming a reflective layer of an optical recording medium, which is composed of a silver alloy having the composition 3. Zn: 1-20 mass% is contained, and further C
a, Be, Si, and a total of one or more selected from: 0.005 to 0.05 mass% and further D
1 or 2 selected from y, La, Nd, Tb and Gd
Total of seeds or more: 0.1 to 3 mass% is contained, and the balance is Ag
A silver alloy sputtering target for forming a reflective layer of an optical recording medium, which is composed of a silver alloy having the composition 4. A reflective layer of an optical recording medium produced by using the silver alloy sputtering target according to claim 1.