TWI405204B - Translucent reflection film for optical recording medium, and ag alloy sputtering target for forming the reflection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable translucent reflecting film for optical recording medium have corrosion resistance that is substantially equivalent to the conventional type, to have high thermal conductivity and low absorptivity, and to further, suppress the increase in absorptivity of a film due to changes from aging of the translucent reflecting film. <P>SOLUTION: A translucent reflecting film for optical recording medium comprises a silver alloy, having a composition consisting of 0.05-1 mass% of Mg, 0.05-1 mass% in total of one kind or more elements from among Eu, Pr, Ce and Sm, and the residuals of Ag and unavoidable impurities. An Ag alloy sputtering target for forming a translucent reflecting film for optical recording media comprises a silver alloy, having a composition consisting of 0.05-1 mass% of Mg, 0.05-1 mass% in total of one kind or more elements from among Eu, Pr, Ce and Sm, and the residuals of Ag and unavoidable impurities. It is possible to manufacture optical recording medium, capable of being used for long periods which can greatly contribute to development of media industry. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

Translucent reflective film for optical recording medium and silver alloy sputtering target for forming the semi-transparent reflective film

The present invention relates to the use of a laser beam such as a semiconductor laser to play or record information signals such as sound, video, and text. Play. Composition of optical recording media such as rewritable optical disc (CD-RW), digital video disc burner (DVD-RW), rewritable DVD disc (DVD-RAM), etc. A semi-transparent reflective film of the layer and a silver alloy sputtering target that forms the semi-transparent reflective film by sputtering. In particular, a translucent reflective film suitable for recording, playing, or erasing optical recording discs (Blu-ray Disc specifications, HD DVD-based optical recording discs, etc.) using a blue laser and sputtering of the translucent reflective film Target target.

In recent years, a two-layer recording type optical recording medium having a two-layer recording film having an extremely thin translucent reflective film having a thickness of about 5 to 15 nm is provided on the incident light side. The related semi-transparent reflective film has a function of transmitting light to the recording layer on the incident light side as a function of the reflective film, and recording or playing the second recording layer. As the semi-transparent reflective film formed on the two-layer recording type optical recording medium, a pure Ag film or an Ag alloy film is used because the pure Ag film or the Ag alloy film has a function of rapidly dissipating heat of the heated recording film. And it has a low absorption rate for laser light in a wide wavelength range of 400 to 800 nm, so it is widely used.

In one example of the reflective film of the optical recording medium, Patent Document 1 discloses that at least one selected from the group consisting of Nd or Y of 0.1% by atom or more and at least one selected from the group consisting of 0.2 to 5.0% by atom is selected from the group consisting of Au and Cu. a group of Pd, Mg, Ti, and Ta, the remainder being a semi-transparent reflective film composed of a component formed of Ag, and the semi-transparent reflective film is used to have at least 0.1% by atom or more of Nd or Y. 1 type, further comprising at least one selected from the group consisting of Au, Cu, Pd, Mg, Ti, and Ta in a total of 0.2 to 5.0 atomic %, and the remainder being a silver alloy target composed of a component formed of Ag, Formed by sputtering.

[Patent Document 1] JP-A-2002-15464

Invention disclosure

In general, when the semi-transparent reflective film of the optical recording medium absorbs incident light, since the efficiency of recording or playback of the second recording layer is deteriorated, it is necessary to reduce the absorption of incident light by the semi-transparent reflective film for the semi-transparent reflective film. On the other hand, since a high-speed recording of the first recording layer on the incident side is required, the semi-transparent reflective film must also achieve high thermal conductivity at the same time.

As the most suitable material for imparting such characteristics, it is known as pure Ag, but the semi-transparent reflective film made of pure Ag has the lowest absorption rate just after use, but is heated when recorded, or recorded/played/deleted. When the film is agglomerated and the semi-transparent reflective film is perforated, the semi-transparent reflective film made of pure Ag has poor corrosion resistance, so that there is a problem that the rapid absorption rate increases in a short time.

On the other hand, the inventors of the present invention have used at least one of Nd or Y containing 0.1 atomic % or more, and further containing Mg in an amount of 0.2 to 5.0 atomic %, and the remainder is Ag. A semi-transparent reflective film composed of components. The result is that the semi-transparent reflective film is compared with the semi-transparent reflective film made of pure Ag, and even if heated during recording, recording, or playback/deletion, the film does not aggregate, and the corrosion resistance is excellent, although some degree is found. The absorption rate is suppressed by the time change, but the effect is still insufficient, and it is required to further suppress the change of the incident light absorption rate over time.

Here, the inventors of the present invention conducted research to obtain a silver alloy semi-transparent reflective film having characteristics of resistance to cohesiveness and corrosion resistance and having a small change in the absorption rate of incident light with time. As a result, (i) one or more of Eu, Pr, Ce, and Sm in the rare earth element containing 0.05 to 1% by mass in total of Mg: 0.05 to 1% by mass, and the remainder The semi-transparent reflective film made of a silver alloy composed of Ag and inevitable impurities maintains a low absorption rate and has higher cohesion resistance and high corrosion resistance as compared with a conventional silver alloy semi-transparent reflective film. Etc., therefore, the change in incident light absorption over time will become less.

(ii) The semi-transparent reflective film according to the above (i) is one or more selected from the group consisting of 0.05 to 1% by mass of Mg, and further containing 0.05 to 1% by mass of Eu, Pr, Ce, and Sm. The remaining part is a silver alloy target made of a silver alloy composed of Ag and inevitable impurities, and the result of the sputtering is obtained.

The present invention has one or more of Eu, Pr, Ce, and Sm containing (1) containing Mg: 0.05 to 1% by mass, and further containing 0.05 to 1% by mass in total, The remaining portion is a semi-transparent reflective film of an optical recording medium made of a silver alloy composed of Ag and inevitable impurities, and (2) contains Mg: 0.05 to 1% by mass, and further contains 0.05 to 1% by mass in total. One or two or more of Eu, Pr, Ce, and Sm, and the remaining portion is a silver alloy composed of Ag and an inevitable impurity, and the semi-transparent reflective film formed by the optical recording medium is splashed with a silver alloy. The plated target is characterized.

The silver alloy sputtering target which forms the semi-transparent reflective film of the present invention is prepared as a raw material having a purity of 99.99% by mass or more, a high purity Ag having a purity of 99.9% by mass or more, and a purity of 99% by mass or more. Purity Eu, Pr, Ce, and Sm, first, a high-purity Ag solution obtained by dissolving high-purity Ag in a high vacuum or an inert gas atmosphere, and adding Mg to the Ag content to form a predetermined amount, and thus the Ag-containing Ag is obtained. In the alloy solution, one or two or more of Eu, Pr, Ce, and Sm are added, and the Ag alloy obtained by casting the mold is dissolved to prepare an ingot. After the cold working, the machine can be manufactured by mechanical processing. Silver alloy sputtering target. The semi-transparent reflective film made of the Ag alloy of the present invention can be formed by using the silver alloy sputtering target thus produced and using a usual sputtering apparatus.

Next, the composition of the semi-transparent reflective film made of the Ag alloy of the present invention and the sputtering target for forming the semi-transparent reflective film made of the Ag alloy will be described as the above limitation.

Mg:Mg is solid-solubilized in Ag, inhibits the change of the semi-transparent reflective film with time, and has the effect of improving the cohesive resistance and corrosion resistance, even if it contains less than 0.05% by mass of Mg, because the absorption of the semi-transparent reflective film is increased for a short time. Since the rate does not have a sufficient effect for improving the cohesive resistance, it is not preferable because the effect of temporally changing the incident light absorptivity cannot be sufficiently suppressed. On the other hand, when Mg is contained in an amount of more than 1% by mass, since the incident light absorption rate of the translucent reflective layer is increased, the recording or playback efficiency of the second recording layer of the optical recording disk is deteriorated, which is not suitable. Therefore, the content of the Mg contained in the Ag alloy semi-transparent reflective film and the sputtering target forming the Ag alloy semi-transparent reflective film is determined to be 0.05 to less than 1% by mass. It is particularly preferably in the range of 0.1 to 0.3% by mass.

Eu, Pr, Ce, and Sm: These rare earth elements are only a little solid solution of Ag, and Ag forms a crystal grain boundary with an intermetallic compound. Since Mg is contained at the same time, it has an effect of improving the cohesiveness of the semitransparent reflective film. When the amount of addition is less than 0.05% by mass, the effect of resisting aggregation is not exhibited. On the other hand, when the amount is more than 1% by mass, the corrosion resistance of the semitransparent reflective film is adversely affected, and the thermal conductivity is further lowered. Not suitable. Therefore, the amount of the above rare earth element added is determined to be 0.05 to 1% by mass. It is particularly preferably in the range of 0.2 to 0.5% by mass.

The semi-transparent reflective film of the optical recording medium of the present invention has substantially the same corrosion resistance as compared with the semi-transparent reflective film of the conventional optical recording medium, thereby having high thermal conductivity and low absorption rate, and further suppressing translucency. The absorption rate of the film caused by the change of the film over time is increased, so that an optical recording medium that can be used for a long period of time can be produced, which contributes greatly to the development of the media industry.

The best form for implementing the invention

Preparation of purity as raw material: Ag of 99.99% by mass or more, purity: 99.9% by mass or more of Mg, and purity: 99% by mass or more of Eu, Pr, Ce, Sm, Nd, and Y.

First, Ag is dissolved in a high-frequency vacuum furnace to prepare an Ag solution, Mg is added to the Ag solution, and Eu, Pr, Ce, Sm, Nd, and Y are added to dissolve, and an ingot is cast by casting, and the obtained ingot is cold-rolled. Thereafter, the mixture was subjected to a heat treatment at 600 ° C for 2 hours in the atmosphere, followed by mechanical processing to prepare a target 1 of the present invention having a diameter of 152.4 mm and a thickness of 6 mm and having the composition shown in Tables 1 to 2. Up to 30, compare targets 1 to 10 and conventional targets 1 to 2.

Using the inventive targets 1 to 30, the comparison targets 1 to 10, and the conventional targets 1 to 2, respectively, a semi-transparent reflective film was produced, and for the semi-transparent reflective films, the following measurements were performed. 4 shows.

(a) Measuring the thermal conductivity of the film, such as the targets 1 to 30 of the present invention, the comparison targets 1 to 10, and the conventional targets 1 to 2, respectively, soldered to a bucking plate made of oxygen-free copper, It is mounted on a DC magnetron sputtering (Magnetron Sputter) device, and the inside of the DC magnetron sputtering device is evacuated to 1×10 ^-4 Pa or less by a vacuum exhaust device, and Ar gas is introduced to become 1.0 Pa sputtering. Air pressure, then DC power supply plus 250W DC sputtering power to the target, against the above target and parallel with the above target 70mm length: 30mm, width: 30mm, thickness: 1mm with oxide film The substrate is subjected to plasma formation with the above-mentioned target to form a semi-transparent reflective film 1 to 30 having a thickness of 10 nm, having the composition shown in Tables 3 and 4, a comparative translucent reflective film 1 to 10, and a conventional half. Transparent reflective films 1 to 2.

The specific resistances of the semi-transparent reflective films 1 to 30 of the present invention having the composition shown in Tables 3 and 4, the comparative translucent reflective films 1 to 10, and the conventional semi-transparent reflective films 1 to 2 are determined by a four-probe method. By the formula based on Wiedemann-Franz law: κ = 2.44 × 10 ^-8 T / ρ (however, κ: thermal conductivity, T: absolute temperature, ρ: specific resistance), The specific resistance was calculated by calculating the thermal conductivity, and the results are shown in Tables 3 and 4.

(b) Determine the absorbance of the film to determine the reflectance. The length of the transmittance: 30 mm, the width: 30 mm, the thickness: 0.6 mm of the carbonate substrate and the above-mentioned inventive targets 1 to 30, the comparative targets 1 to 10, and the conventional targets 1 to 2 are plasma-generated. The semi-transparent reflective films 1 to 30 of the present invention having the composition shown in Tables 3 and 4, the comparative translucent reflective films 1 to 10, and the conventional semi-transparent reflective films 1 to 2 are formed on a carbonate substrate to have a thickness of 10 nm. The reflectance and the transmittance at a wavelength of 650 nm from the side of the semitransparent reflective film were measured by a spectrophotometer, and "100-(reflectance + transmittance)" defined as the absorptivity was obtained. The results are shown in Tables 3 and 4. Show.

(c) Determination of the resistance of the film to cohesiveness: a carbonate substrate having a length of 30 mm, a width of 30 mm, a thickness of 0.6 mm, and the above-described inventive targets 1 to 30, comparative targets 1 to 10, and conventional targets 1 to 2 A plasma is generated to form a thickness of 10 nm on the carbonate substrate: the semi-transparent reflective films 1 to 30 of the present invention having the composition shown in Tables 3 and 4, the comparative translucent reflective films 1 to 10, and the conventional translucent reflection. Membrane 1 to 2, maintaining these cohesive resistance evaluation samples at a temperature of 90 ° C, relative humidity: 85% of a constant temperature and humidity chamber for 300 hours, measured by spectrophotometer at a wavelength of 650 nm from the semi-transparent reflective film side The reflectance and the transmittance were determined by the definition of the above absorption rate, and the absorption rate of the film after the cohesion resistance test was determined. The value obtained by the absorption measurement of the film (b) above was used as the absorption rate before the coagulation resistance test, and the amount of increase in the absorption rate before and after the coagulation resistance test was determined. The results are shown in Tables 3 and 4, and the evaluation film was used. Resistance to cohesion.

From the results shown in Tables 1 to 4, it is understood that the translucent reflective film obtained by sputtering using the inventive targets 1 to 30 is compared with the semitransparent reflective film obtained by sputtering using the conventional targets 1 to 2, and the thermal conductivity is compared. When the absorption rate is high, the amount of increase in the absorption rate is low, and since the aggregation resistance is more excellent, the absorption rate changes less with time, and therefore, it has excellent characteristics as a semi-transparent reflection film. However, it has been found that a semi-transparent reflective film produced using comparative targets 1 to 10 containing Mg and Ca outside the range of the present invention exhibits a decrease in the increase in the absorption rate and a decrease in the thermal conductivity.

Industrial use

Since the translucent reflective film for an optical recording medium of the present invention has characteristics of resistance to cohesion and corrosion, and the change in the absorption rate of incident light is small, it is very effectively used as an optical recording disc (CD-RW, Compositions of optical recording media such as DVD-RW, DVD-RAM, etc., in particular, optical recording discs (Blu-ray Disc specifications, optical recording discs based on HD DVD specifications, etc.) that are recorded, played, or deleted using a blue laser. Floor.

Claims (2)

A semi-transparent reflective film of an optical recording medium, which contains Mg: 0.05 to 1% by mass, and further contains one or more of Eu, Pr, Ce, and Sm in a total amount of 0.2 to 1% by mass, and the remainder The part is made of a silver alloy composed of Ag and inevitable impurities. A silver alloy sputtering target for forming a semi-transparent reflective film of an optical recording medium, characterized in that it contains Mg: 0.05 to 1% by mass, and further contains 0.2 to 1% by mass of Eu, Pr, Ce, and Sm. One type or two or more types, and the remaining part is a silver alloy composed of Ag and inevitable impurities.