JP2003027158A - Gold alloy for forming optical recording disk reflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gold alloy giving a reflection film which has high reflectance and high thermal conductivity for increasing the recording density of an optical disk, and has excellent corrosion resistance and heat resistance. SOLUTION: The gold alloy for forming the optical recording disk reflection film has a composition containing at least one kind of element selected from the groups consisting of Mg, Al, Ti, Co, Ge, Zr, Sb, Zn, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy and Ca in 0.05 to 0.2 wt.%, and the balance Au.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gold alloy for forming a reflective film on an optical recording disk, and more particularly, it has high reflectance and high thermal conductivity, and has excellent corrosion resistance and heat resistance. It relates to a gold alloy that gives a film.

[0002]

2. Description of the Related Art As a medium for recording computer information, video information or music information, CD, CD-R, CD-
RW, DVD, DVD-RW, DVD-RAM, MO
Various optical recording discs (hereinafter, optical discs) such as D and MD are used. These optical discs have different layer structures depending on their recording / reproducing systems.
Each of them is manufactured by forming a thin film having various functions, such as a recording film, a reflective film, a protective film, etc., in layers on a transparent plastic substrate.

The reflective film (including a semi-transparent film of a multilayer disc such as a DVD) has a function of reflecting a laser beam used for reading and writing information, a function of radiating heat caused by the laser beam, and the like. It is used for optical disks of all recording / playback systems. Further, as the reflection film, mainly A
A thin metal film made of 1, 1, Au, Ag, or an alloy thereof is used. For example, a read-only optical disk such as a CD or a DVD has a pure Au thin film and a DVD with good corrosion resistance.
A thin film of pure Au or pure Si is mainly used as a semi-permeable film of a multi-layer disc.

In recent years, for example, it was commercialized relatively early,
Deterioration has been recognized in audio CDs that have been manufactured for 10 to 15 years, and the long-term storability (long-term reliability) of optical discs is beginning to be a problem. As a measure for improving the long-term storage stability of this optical disk, the reflective film is required to have high corrosion resistance. Moreover, the amount of information is rapidly increasing with the spread of computers, and the recording density of an optical disk, which is a recording medium thereof, is rapidly increasing. Corresponding to the high recording density of this optical disc,
High reflectance and high thermal conductivity are required for the reflective film.

However, Al alloys have a problem in that they have relatively good corrosion resistance in normal use, but lack long-term reliability, and have low thermal conductivity. There is a problem that it is difficult to deal with. Since Ag alloy has high thermal conductivity, its corrosion resistance has been improved especially for the purpose of coping with higher recording density, but long-term reliability has not been sufficiently examined and long-term reliability has not been improved. I am in a situation where my anxiety remains. Further, although Si is beginning to be used as a low-cost semi-transparent film in place of Au, it has a problem that it cannot cope with high recording density because of its low reflectance.

On the other hand, Au has excellent corrosion resistance, high reflectance and high thermal conductivity, and is a material that can meet the above requirements. However, due to the heat load in data rewriting, erasing, long-term storage, etc. Heat resistance that the disk characteristics such as C / N ratio, jitter, and modulation degree are likely to deteriorate because the crystal structure becomes coarse (crystal grains grow), the surface roughness of the film increases, and the reflectance locally decreases. Have sex problems. When Au is used as a semi-permeable film of a multi-layer disc, the transmittance locally changes in addition to the reflectance, and the disk characteristics deteriorate.

[0007]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, an object of the present invention is to have a high reflectance and a high thermal conductivity, which are compatible with the high recording density of an optical disk, and have a corrosion resistance and a heat resistance. Another object of the present invention is to provide a gold alloy that provides a reflective film having excellent properties.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by a gold alloy containing a specific element. Based on this, the present invention has been completed. That is,
According to the present invention, the following gold alloy for forming a reflective film of an optical recording disk is provided. (1) A gold alloy for forming an optical recording disk reflection film,
Mg, Al, Ti, Co, Ge, Zr, Sb, Zn, L
Characterized by containing 0.05 to 0.2% by weight of at least one element selected from the group consisting of a, Ce, Nd, Sm, Eu, Gd, Tb, Dy, and Ca, with the balance being Au. A gold alloy for forming a reflective film on an optical recording disk. (2) The gold alloy for forming an optical recording disk reflective film according to (1), which contains 0.1 to 20% by weight of Ag.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The gold alloy for forming an optical recording disk reflective film of the present invention is composed of Mg, Al, Ti, Co, Ge, Zr,
Sb, Zn, La, Ce, Nd, Sm, Eu, Gd, T
It contains 0.05 to 0.2% by weight of at least one element selected from the group consisting of b, Dy, and Ca, and the balance is A
It is characterized by consisting of u. Even when the gold alloy contains trace components (unavoidable impurities) other than the above elements,
As long as it has the same effects as the present invention, it is included in the gold alloy of the present invention. Further, the reflective film in the present invention includes, as described above, a semi-permeable film used for a multilayer disc such as a DVD.

It is generally known that coarsening of the crystal structure of the Au film can be prevented by adding a large amount of alloying elements such as Cu and Ni. In this case, however, the thermal conductivity and corrosion resistance of the Au film are high. Occurs. In the present invention, Mg, Al, Ti, Co, Ge, Zr, S
b, Zn, La, Ce, Nd, Sm, Eu, Gd, T
A small amount of at least one element selected from the group consisting of b, Dy, and Ca is added to Au.

The above-mentioned elements are extremely excellent in the function of refining the crystal structure of the Au film, and by adding a small amount of at least one of these elements to Au, a reflecting film having a fine crystal structure regardless of sputtering conditions. In addition to the above, it is possible to prevent the crystal structure of the reflective film from coarsening during the subsequent manufacturing process or use. Further, by adding at least one of the above-mentioned elements to Au, the crystal structure of the sputtering target is miniaturized and the sputtering rate is made uniform, and further the adhesion between the reflective film and the plastic substrate is improved. To do. That is, the gold alloy of the present invention has high reflectance and high thermal conductivity, as well as excellent corrosion resistance and heat resistance, so that the crystal structure becomes coarse due to a heat load during data rewriting, erasing, long-term storage, etc. It is possible to obtain a reflection film in which the reflectance is prevented and the reflectance is not lowered.

In the optical disk, the thermal conductivity required for the reflective film differs depending on the film structure (composition, film thickness, etc.) of the disk. According to the present invention, the thermal conductivity of the reflective film can be controlled within the required range by reducing the type and amount of the additive element without lowering the reflectance. Further, the gold alloy of the present invention is used in applications requiring high reflectivity such as a reflective film such as a reflecting mirror, a lighting fixture, a sign, and a reflector, as well as heat resistance and corrosion resistance, and a liquid crystal display (LCD),
It is also useful for applications such as plasma display (PDP) and EL (electroluminescence) displays that require high heat dissipation such as a heat dissipation reflection film, and also for applications that require low electrical resistivity such as various wiring materials.

In the present invention, the addition amount of the above elements is
It is 0.05 to 0.2% by weight, preferably 0.05 to 0.1% by weight, based on the total weight of the alloy. When the addition amount of the element is less than the above range, it is not preferable because sufficient heat resistance cannot be obtained, while when it is more than the above range,
It is not preferable because the thermal conductivity and corrosion resistance of the reflective film are sharply reduced. The reflectance of the reflective film is preferably 80% or more in order to obtain a high C / N ratio and improve the recording speed.

Further, in the present invention, in order to reduce the manufacturing cost of the gold alloy, part of Au in the gold alloy can be replaced with Ag. In this case, the amount of Ag added is usually 0.1 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.1 to 10% by weight, based on the total weight of the alloy.
5% by weight. If the addition amount of Ag is less than the above range, it is not preferable because a sufficient addition effect cannot be obtained.
On the other hand, if the amount exceeds the above range, the thermal conductivity and corrosion resistance of the reflective film are extremely lowered, which is not preferable. The thermal conductivity of the reflective film is usually 60 W / m · K or more, preferably 10
It is 0 W / m · K or more, and more preferably 150 W / m · K or more. When the thermal conductivity is lower than this range, the heat dissipation function is not sufficiently exhibited, which is not preferable.

The method for producing the gold alloy of the present invention includes:
A conventionally known method can be used, for example, a purity of 99.99%
After mixing the above Au and the above elements in a specific ratio, the mixture is filled in an alumina crucible, a graphite crucible, etc., melted at about 1200 ° C. in a high vacuum or an inert gas atmosphere, and further in a vacuum or an inert gas atmosphere. It is possible to manufacture an Au alloy ingot by casting with.

As a method for processing the gold alloy of the present invention to produce a sputtering target, a conventionally known method can be used. For example, the alloy ingot is hot worked (forged
The target for sputtering can be produced by performing mechanical processing after rolling, or by mixing Au powder and additive element powder and sintering by hot pressing.

As the method for producing the above-mentioned reflective film, a sputtering method, a vacuum deposition method, an ion plating method,
Although a conventionally known method such as a CVD method or a plating method can be used, it is preferable to use a sputtering method. For example, after soldering the target to a cooling plate, the target is attached to a DC magnetron sputtering device, and a glass substrate or a Si substrate is used. Alternatively, the reflective film can be prepared by forming an alloy thin film on a plastic substrate. In the sputtering method, instead of the target, a target in which a chip of the additional element (for example, 5 mm × 5 mm × 0.5 mm thickness) is arranged on the Au target, or a pellet of the additional element is embedded in the Au target. You can also use a target.

[0018]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Method for producing protective film, recording film and reflective film) The ultimate vacuum in the chamber before the start of sputtering is set to 6.
The sputtering shown in Table 1 was performed at 0 × 10 ⁻⁵ Pa or less.
Under the target and sputtering conditions, a protective film, a recording film, and a reflective film were formed by a sputtering method. (Testing / Evaluation Method of Film Characteristics) (1) Film Composition The composition of each film is as follows:
ICP (Induced Coupling Plas)
ma Analysis). Table 1 shows the target composition for the protective film and the recording film, Table 2 shows the target composition for the reflective film and the reflective film composition, and Table 3 shows the film thickness of each film measured by the stylus method. As a target for producing the reflective film, a hot pressing method (Au powder having a purity of 99.99% by weight and additive element powder were mixed, and 1.0 × 10 ⁻³ Tor was mixed.
After evacuation to r or less, under an Ar atmosphere of 600 Torr or under a vacuum of 1.0 × 10 ⁻³ Torr or less, 8
Sintered body target obtained by sintering at a temperature of 50 ° C. and a pressure of 24.5 MPa, and a melting method (purity 99.999)
1% by weight shot or powder of Au ingot and 99.99% by weight of additional element in an inert gas atmosphere or vacuum.
Two types of targets, a melt-casting target obtained by melting at 200 to 1500 ° C.), were used, but the target composition and the reflective film composition of both targets were almost the same, and the composition in each part in the reflective film was also almost the same. It was uniform. (2) Thermal conductivity The thermal conductivity of the reflective film is measured by measuring the electrical resistivity of the film by the direct current 4-terminal method, and the following formula (Widemann-Franz law) is used.
I asked more. λ · ρ / T = L ₀ 2.43 × 10 ⁻⁸ where λ, ρ, T, and L ₀ are thermal conductivity (W
/ M · K), electrical resistivity (Ω · cm), absolute temperature (K), and Lorentz number (W · Ω / K ² ). The electrical resistivity was measured by forming a reflective film on a cover glass having a thickness of 20 mm × 70 mm × 0.8 mm and then cutting the film into 3 mm × 6 mm. The film thickness of each sample is 3000Å
Met. (3) Reflectance The reflectance is measured using a spectrophotometer at wavelengths of 650 nm and 780.
It was measured in nm. The film thickness of each sample was 3000Å. (4) Heat-resistant sputtered film and annealing treatment (1.0 × 10
^The crystal grain size and surface roughness of the film, which was kept at 150 ° C. for 48 hours in a high vacuum of ⁻⁵ Pa or less, were measured to evaluate the heat resistance of the reflective film. The film thickness of each sample is 3
It was 000Å. Crystal grain size The crystal grain size was determined by performing X-ray diffraction (XRD) to determine the grain size of the crystal grain from the diffraction peak position and the half-value width, and observing and confirming by SEM after etching a small amount of the film. Surface roughness Surface roughness (center line surface roughness Ra) is 20Å
A film is formed on the following glass substrate and Si substrate, and Topo
The measurement was performed using an AFM (atomic force microscope) manufactured by Metrix Co., Ltd., and at the same time, it was measured and confirmed by a contact type surface roughness meter.

Examples 1 to 39, Comparative Examples 1 to 5 As evaluation disks, the following were used for CD systems and DV.
Two types of discs for D system were produced. A lower protective film and a recording layer were formed on a polycarbonate substrate (hereinafter referred to as PC substrate 1) having a thickness of 1.2 mm, a diameter of 120 mm, a pitch of 1.6 μm and a depth of 50 nm, which was produced by injection molding, by a sputtering method. A film, an upper protective film, and a reflective film were sequentially formed. Next, an ultraviolet curable resin (SD-318 manufactured by Dainippon Ink and Chemicals, Inc.) was applied on the reflective film by a spin coating method, and then irradiated with ultraviolet rays to be cured to form a 5 μm overcoat layer. This was used as a CD-based evaluation disk. Also, the thickness of 0.6m produced by injection molding
m, diameter 120 mm, pitch 0.8 μm, depth 30 n
On a polycarbonate substrate with a groove of m (hereinafter referred to as PC substrate 2), a lower protective film, a recording film,
An upper protective film and a reflective film were sequentially formed. Next, an ultraviolet curable resin (SD-318 manufactured by Dainippon Ink and Chemicals) is formed on the reflective film.
Was applied by a spin coating method and then irradiated with ultraviolet rays to be cured to form a 4 μm overcoat layer. Then, onto this substrate, a polycarbonate substrate (blank disc) having a thickness of 0.6 mm and a diameter of 120 mm was stuck using an ultraviolet curing resin (SD-318 manufactured by Dainippon Ink and Chemicals), and a disc for evaluation for DVD system was used. And Then, the entire surface of the disk was fully crystallized by DC light of 10 mW on the medium surface to an initial (unrecorded) state, and an optical disk evaluation device OMS-2000S manufactured by Nakashichi Co., Ltd.
The disc characteristics were evaluated under the following conditions using a system in which the system was improved for a phase change type optical disc. For CD discs, a semiconductor laser beam with a wavelength of 780 nm is passed through a lens of NA 0.55 and the diameter is 1 μm on the medium surface.
The spot diameter was narrowed down to irradiate from the substrate. The reading power Pr is 0.9 mW and the linear velocity of the optical disk is 2.
3 levels of 0, 5.0, 10.0 m / sec, Pw of 8-16 mW with laser power Pe / Pw = 0.5
The CNR (carrier-to-noise ratio), the jitter, and the modulation factor were measured by selecting the conditions in which the CNR (carrier-to-noise ratio) is large and the jitter is small. For a DVD disc, semiconductor laser light with a wavelength of 633 nm was narrowed down to a spot diameter of 0.5 μm on the medium surface through a lens of NA 0.6 and irradiated from the substrate. The reading power Pr is 0.9 mW, the linear velocity of the optical disk is two levels of 7.0 and 15.0 m / sec, the laser power is Pe / Pw = 0.5, and Pw is 8 to 8.
CNR (carrier-to-noise ratio) varied up to 16 mW
Is selected and the jitter is reduced, the CNR is selected.
(Carrier to noise ratio), jitter, and degree of modulation were measured. Next, as a high temperature and high humidity storage test,
After being left in a high temperature and high humidity condition of 0 ° C. and 95% RH for 2000 hours, the disk characteristics were measured in the same manner as the disk in the initial state. As a high temperature and high humidity storage test, 80
It is common to test under conditions of ℃, 85% RH and 500 hours of storage, but in order to track changes in disk characteristics over a longer period (long-term storage stability is confirmed), storage under more severe conditions The test was conducted. Table 4 shows the reflective film characteristics.
Table 5 shows the disk characteristics. Regarding the disk characteristics, the example used the data of the worst linear velocity among the respective linear velocities, and the comparative example used the data of the best linear velocity among the respective linear velocities as the representative data.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

[Table 5]

As is clear from the results of Tables 4 and 5, the gold alloy of the present invention has high reflectance and high thermal conductivity, as well as excellent corrosion resistance and heat resistance. It is possible to obtain a reflective film (optical disk excellent in long-term storage stability) in which coarsening of the crystal structure due to storage is prevented and the reflectance is not lowered.

[0027]

As described above, according to the gold alloy of the present invention, a reflection having a high reflectance and a high thermal conductivity, which is compatible with a high recording density of an optical disk, and is excellent in corrosion resistance and heat resistance. A membrane can be obtained.

Claims (2)

[Claims] 1. A gold alloy for forming a reflective film of an optical recording disk, comprising: Mg, Al, Ti, Co, Ge, Zr, Sb,
Zn, La, Ce, Nd, Sm, Eu, Gd, Tb, D
A gold alloy for forming an optical recording disk reflective film, which contains 0.05 to 0.2% by weight of at least one element selected from the group consisting of y and Ca, and the balance being Au. 2. The gold alloy for forming a reflective film of an optical recording disk according to claim 1, which contains 0.1 to 20% by weight of Ag.