JP4186223B2 - Reflective film and translucent reflective film for optical recording medium, and Ag alloy sputtering target for forming these reflective films - Google Patents

Description

  The present invention relates to an optical recording disk (CD-RW, DVD-RW, DVD-RAM, etc.) for reproducing or recording / reproducing / erasing information signals such as audio, video, and characters using a laser beam such as a semiconductor laser. The present invention relates to a reflective film and a semitransparent reflective film that are constituent layers of an optical recording medium, and an Ag alloy sputtering target for forming these reflective films by a sputtering method.

  Conventionally, pure Ag or an Ag alloy film has been used as a reflective film and a translucent reflective film for optical recording media such as CD-R, CD-RW, DVD-R, DVD-RW, and DVD-RAM. A film or an Ag alloy film is widely used because it has a function of quickly releasing the heat of a heated recording film and has a high reflectance with respect to laser light in a wide wavelength range of 300 to 800 nm.

Various reflective films and translucent reflective films made of various Ag alloys have been proposed as reflective films and translucent reflective films for optical recording media (see, for example, Patent Documents 1, 2, and 3). For example, Patent Document 3 contains Cu: 0.5 to 3 mass%, and further contains one or more selected from Ca, Be, Si: 0.005 to 0.05 mass% In addition, a reflection film and a semitransparent reflection film of an optical recording medium whose balance is made of Ag, and a target for forming the reflection film by sputtering are described.
JP 2001-126315 A JP 2004-2929 A JP 2003-155561 A

In recent years, the demand for high-speed recording in optical recording media has led to an increase in the output of laser light used for recording. Therefore, reflective film materials can quickly diffuse heat from the laser irradiated to the recording area. That is, it has become increasingly important to have excellent thermal conductivity.
Moreover, in a two-layer recording type optical recording medium having two recording films, for example, as shown in “Proceeding of the 15th. Symposium on Phase Change Optical Storage Storage PCOS 2003, P86-89”, A very thin semi-transparent reflective film having a thickness of about 10 to 20 nm is provided. The semi-transparent reflective film transmits light in addition to the function as a reflective film for the recording layer on the incident light side and transmits the second recording. It has the function of recording on the layer.
In this case, if the semi-transparent reflective film absorbs incident light, the recording efficiency in the second recording layer deteriorates, so the semi-transparent reflective film reduces the absorption of incident light into the semi-transparent reflective film. This is an important issue. On the other hand, the semitransparent reflective film must also realize high thermal conductivity at the same time due to the requirement for high-speed recording described above for recording on the first recording layer on the incident side.
Pure Ag is known as the most suitable material for imparting such characteristics. However, when the translucent reflective film is made of pure Ag, the film aggregates when heated during recording or recording / reproducing / erasing. However, there is a problem that the translucent reflective film has a hole. On the other hand, conventional Cu: containing 0.5 to 3% by mass, and further, one or two kinds selected from Ca, Be, and Si Sum of the above: The Ag alloy translucent reflective film containing 0.005 to 0.05% by mass and the balance being made of Ag aggregates even when heated during recording or recording / reproducing / erasing However, since Cu: 0.5 to 3% by mass is contained, there is a problem that the thermal conductivity and the absorptance are lower than those of pure Ag.

Therefore, the present inventors have been researching to obtain a reflective film and a translucent reflective film made of an Ag alloy that suppresses aggregation of the film while maintaining high thermal conductivity and high reflectance close to pure Ag.
(I) Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and one or more selected from Pr, Ce, Gd, and Tb Reflective film or translucent reflective film of optical recording medium comprising 0.05 to 0.2% by mass in total, the balance being made of Ag and unavoidable impurities, and Ag being a composition containing 99% by mass or more Can suppress aggregation of the film while maintaining high thermal conductivity and high reflectance close to pure Ag.
(B) Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, Ir: 0.005 to 0.2 mass%, Pd: 0.01 to 0 The reflective film or translucent reflective film of an optical recording medium having a silver alloy having a composition containing 0.5% by mass, the balance being made of Ag and inevitable impurities, the Ag being 99% by mass or more, has a high heat close to pure Ag. It can suppress film aggregation while maintaining conductivity and high reflectivity,
(C) Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, Re: 0.005 to 0.2 mass%, Pd: 0.01 to 0 The reflective film or translucent reflective film of an optical recording medium comprising a silver alloy having a composition containing 0.5% by mass, the balance being made of Ag and inevitable impurities, the Ag being 99% by mass or more, has a high heat close to pure Ag. It can suppress film aggregation while maintaining conductivity and high reflectivity,
(D) Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and further Ir and Re: 0.005 to 0.2% by mass, Pd: 0 The reflective film or translucent reflective film of an optical recording medium containing 0.01 to 0.5% by mass, the balance being made of Ag and inevitable impurities, and the Ag being a composition containing 99% by mass or more is pure. It is possible to suppress film aggregation while maintaining high thermal conductivity and high reflectance close to Ag.
(E) The reflective film or translucent reflective film of the optical recording medium described in (a) to (d) above is formed by sputtering using a target having the same component composition as that of the reflective film of the optical recording medium. The research result that it was obtained was obtained.

The present invention has been made based on such research results,
(1) Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and one or more selected from Pr, Ce, Gd, and Tb Reflective film or translucent reflective film of optical recording medium comprising 0.05 to 0.2% by mass in total, the balance being made of Ag and unavoidable impurities, and Ag being a composition containing 99% by mass or more ,
(2) Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, Ir: 0.005 to 0.2 mass%, Pd: 0.01 to 0 A reflective film or a translucent reflective film of an optical recording medium comprising a silver alloy having a composition of 0.5 mass%, the balance being made of Ag and inevitable impurities, the Ag being 99 mass% or more,
(3) Ca: 0.005-0.1% by mass, Ga: 0.1-0.6% by mass, Re: 0.005-0.2% by mass, Pd: 0.01-0 A reflective film or a translucent reflective film of an optical recording medium comprising a silver alloy having a composition of 0.5 mass%, the balance being made of Ag and inevitable impurities, the Ag being 99 mass% or more,
(4) Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and a total of Ir and Re: 0.005 to 0.2% by mass, Pd: 0 A reflective film or a semitransparent reflective film of an optical recording medium comprising a silver alloy having a composition containing 0.01 to 0.5% by mass, the balance being made of Ag and inevitable impurities, and the Ag being contained by 99% by mass or more,
(5) Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and one or more selected from Pr, Ce, Gd, and Tb Reflective film or translucent reflective film of optical recording medium comprising 0.05 to 0.2% by mass in total, the balance being made of Ag and unavoidable impurities, and Ag being a composition containing 99% by mass or more Silver alloy sputtering target for forming,
(6) Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, Ir: 0.005 to 0.2 mass%, Pd: 0.01 to 0 A silver alloy sputtering target for forming a reflective film or a translucent reflective film of an optical recording medium comprising a silver alloy having a composition containing 0.5% by mass, the balance being made of Ag and inevitable impurities, wherein the Ag is 99% by mass or more,
(7) Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, Re: 0.005 to 0.2 mass%, Pd: 0.01 to 0 A silver alloy sputtering target for forming a reflective film or a translucent reflective film of an optical recording medium comprising a silver alloy having a composition containing 0.5% by mass, the balance being made of Ag and inevitable impurities, wherein the Ag is 99% by mass or more,
(8) Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, and further Ir and Re: 0.005 to 0.2 mass%, Pd: 0 Silver for forming a reflective film or a semitransparent reflective film of an optical recording medium comprising a silver alloy having a composition containing 0.01 to 0.5% by mass, the balance being made of Ag and inevitable impurities, and Ag being 99% by mass or more. The alloy sputtering target is characterized.

The sputtering target for forming the silver alloy reflective film or translucent reflective film of the present invention has a purity of 99.99% by mass or more of high purity Ag and a purity of 99% by mass or more of Ca as raw materials. Ir, Re, Pr, Ce, Gd, Tb, Pd and Ga of 9.9% by mass or more are prepared. First, Ag melts obtained by melting high purity Ag in a high vacuum or in an inert gas atmosphere are prepared, and Ca is added to these Ag melts so as to have a predetermined content. Alternatively, an Ag—Ca master alloy is prepared in advance by casting in an inert gas atmosphere.
Further, Ir or Re is added to a molten Pd obtained by melting Pd in a high vacuum or an inert gas atmosphere so as to have a predetermined content, and then cast in a vacuum or an inert gas. -Pd master alloy and Re-Pd master alloy are prepared in advance.
Next, an Ag-Ca master alloy is added to the high-frequency vacuum melted Ag melt to produce a Ca-containing Ag melt, and then the Ca-containing Ag melt is filled with Ga, Ir-Pd master alloy and / or Re-Pd master alloy, Pr. , Ce, Gd, and Tb, one or more components are adjusted so as to have a predetermined component composition, then cast into a mold to produce ingots, and these ingots are cold worked and then machined Thus, an Ag alloy sputtering target can be manufactured.
As a method for adding Ga to the molten Ag, Ga is preferably added by wrapping it in advance with an Ag foil.

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

Ca:
Ca hardly dissolves in Ag, but by forming a film by sputtering, the Ca is forcibly dissolved in the crystal grains formed by Ag, and thereby, in the crystal grains of the reflective film or translucent reflective film. In addition, it suppresses the self-diffusion of Ag and further precipitates at the grain boundaries. Even if the film is heated by the effects of forced solid solution inside Ag and precipitation at the grain boundaries, And preventing the aggregation of the reflective film or translucent reflective film, the desired effect cannot be obtained even if Ca is contained in an amount of less than 0.005% by mass. If it is contained in excess, the thermal conductivity of the Ag alloy reflective film or translucent reflective film is lowered, which is not preferable. Therefore, the content of these Ca contained in the sputtering target for forming the Ag alloy reflective film or the semitransparent reflective film and the Ag alloy reflective film or the semitransparent reflective film is set to 0.005 to 0.1% by mass. . A more preferable range for exhibiting the aggregation suppressing effect is 0.01 to 0.07% by mass.

Ga:
Ga has the effect of accelerating the aggregation prevention effect due to Ca by the combined addition of Ga and Ca, and particularly has the effect of remarkably exerting the aggregation suppression effect in a very thin translucent reflective film having a film thickness of 30 nm or less. If the content is less than 0.1% by mass, the effect of promoting the suppression of aggregation by Ca cannot be obtained. On the other hand, if the content exceeds 0.6% by mass, it is a reflective film made of an Ag alloy formed by sputtering or translucent. This is not preferable because the thermal conductivity of the reflective film decreases and the absorptance increases. Therefore, in order to have high thermal conductivity and high reflectance and to suppress aggregation, Ga: 0.1 to 0.6% by mass (more preferably 0.3 to 0.6% by mass) is set.

Pr, Ce, Gd, Tb:
These components react with Ag to form intermetallic compounds in crystal grains and / or crystal grain boundaries, exhibit aggregation suppression effects and improve corrosion resistance, so are added together with Ga and Ca. Even if the amount is less than 0.05% by mass, a remarkable effect of suppressing aggregation cannot be obtained. On the other hand, if the amount exceeds 0.2% by mass, the thermal conductivity decreases and the reflective film or the semi Since it does not become a transparent reflective film, it is not preferable. Therefore, the content of these components contained in the reflective film and the semitransparent reflective film made of Ag alloy and the sputtering target for forming these reflective film or semitransparent reflective film is set to 0.05 to 0.2 mass%. . More preferably, the content is 0.05 to 0.15% by mass which has an aggregation suppressing effect and simultaneously exhibits high thermal conductivity.

Ir, Re:
These components are hardly dissolved in Ag, but are forcibly dissolved in the crystal grains formed by Ag by forming a film by sputtering, and thereby in the crystal grains of the reflective film or translucent reflective film. Suppresses self-diffusion of Ag, exhibits aggregation suppression effect and improves corrosion resistance, so it is added together with Ga and Ca. Even if Ir, Re, and Ir + Re all contain less than 0.005% by mass, it has the effect of suppressing aggregation. On the other hand, if Ir, Re, and Ir + Re contain more than 0.2% by mass, the thermal conductivity is lowered, and the reflective film or the semitransparent reflective film having high thermal conductivity is not preferable. Therefore, the content of these components contained in the reflective film and the semitransparent reflective film made of an Ag alloy and the sputtering target for forming the reflective film or the semitransparent reflective film is Ir: 0.005 to 0.2 mass%. , Re: 0.005 to 0.2% by mass, and the total of Ir and Re: 0.005 to 0.2% by mass.

Pd:
The Pd component has the effect of uniformly dispersing Ir and Re, which are dissolved in all of Ag, Ir, and Re, and hardly dissolved in Ag, in the target. As a result, the reflection film made of an Ag alloy and the translucent reflection It has the effect of uniforming Ir and Re components in the film and is added to improve the corrosion resistance. However, even if it contains less than 0.01% by mass of Pd, no significant effect is seen in the corrosion resistance. If the content exceeds 50%, the thermal conductivity of the reflective film and the semitransparent reflective film formed by sputtering will decrease and the absorptance will increase, so that high thermal conductivity and low absorptance will be imparted. Therefore, Pd was determined to be 0.01 to 0.5% by mass.

Ag:
When the amount of the additive element is increased and the Ag content is less than 99% by mass, the thermal conductivity and the absorptance increase, and the performance as a reflective film or a translucent reflective film is deteriorated. Therefore, the amount of Ag contained in the reflective film and translucent reflective film made of the Ag alloy of the present invention and the sputtering target for forming these reflective films is 99% by mass or more (preferably 99.5% by mass or more). did.

  The reflective film or translucent reflective film of the optical recording medium produced using the Ag alloy sputtering target of the present invention is compared with the reflective film or translucent reflective film of the optical recording medium produced using the conventional Ag alloy sputtering target. , An optical recording medium having a high thermal conductivity close to pure Ag and a low absorptance in a semitransparent reflective film, and having no perforation due to agglomeration caused by aging of the semitransparent reflective film for high-speed recording, and usable for a long period Can greatly contribute to the development of the media industry.

Purity: 99.99% by mass or more of Ag, purity: 99% by mass or more of Ca, and purity: 99.9% by mass or more of Ir, Re, Pr, Ce, Gd, Tb, Pd and Ga were prepared. .
Next, Ag is melted in a high-frequency vacuum melting furnace to produce a molten Ag, and added to this molten Ag so that the content of Ca is 5% by mass. After melting, the furnace is filled with Ar gas until the pressure in the furnace reaches atmospheric pressure. And then cast into a graphite mold to produce an Ag-5 mass% Ca master alloy. Further, the composition ratio of Pd and Ir, or Pd and Re is Pd: Ir = 80: 20, 70:30 and After weighing so that Pd: Re = 80: 20 and 70:30, it was melted in a high-frequency vacuum melting furnace, and after melting, it was filled with Ar gas until the pressure inside the furnace reached atmospheric pressure. Ingots of Pd-20% Ir, Pd-30% Ir, Pd-20% Re, and Pd-30% Re were manufactured by mass casting (hereinafter, these were referred to as Pd-Ir master alloy, Pd-Re, respectively). Then, these mother alloys are At a thickness: it was rolled up to 2mm.
The master alloy thus prepared is added to an Ag melt previously melted in a high-frequency vacuum melting furnace to prepare a Ca-containing Ag melt, and then, Ga, Pr, and Ce wrapped in an Ag foil in the Ca-containing Ag melt. , Gd, Tb, Pd—Ir alloy, Pd—Re alloy, and the like are prepared, and an ingot is prepared by casting this Ag alloy melt into a mold. The ingot is then heated at 550 ° C. for 2 hours. After heating under holding conditions and water cooling, cut into a predetermined size, then cold work at room temperature, then heat treated under the conditions of holding at 600 ° C. for 1 hour and then machined to obtain a diameter: The present invention targets 1 to 18 and comparative targets 1 to 16 having the dimensions of 125 mm and thickness: 5 mm and having the composition shown in Tables 1 and 2 were produced.
For further comparison, an Ag melt was prepared by melting Ag in a high-frequency vacuum melting furnace, and an ingot was prepared by casting the obtained Ag melt into a graphite mold in an Ar gas atmosphere. The ingot was cut into a predetermined size, cold-rolled at room temperature, then heat-treated at 550 ° C. for 1 hour, and then machined to obtain a diameter of 125 mm and a thickness of 5 mm. A conventional target 1 made of pure Ag shown in Table 2 was manufactured.
Further, Ag is melted in a high-frequency vacuum melting furnace, Cu is added to prepare a molten Ag—Cu alloy, and further, an Ag-5 mass% Ca master alloy is added to the obtained Ag—Cu alloy molten metal to obtain Ca. An ingot is prepared by producing a molten Ag alloy melt, casting the obtained Ag alloy melt into a graphite mold in an Ar gas atmosphere, and cutting the obtained ingot into a predetermined size, and then at room temperature. Conventionally having a diameter of 125 mm and a thickness of 5 mm by cold rolling and then heat-treating under conditions of holding at 550 ° C. for 1 hour, and having the component composition shown in Table 2 Target 2 was manufactured.

  The present invention Ag alloy films 1-18 having the composition shown in Tables 3-5 by sputtering under the following conditions using the present invention targets 1-18, comparative targets 1-16 and conventional targets 1-2. The comparative Ag alloy films 1 to 16 and the conventional Ag alloy films 1 to 2 are formed, and the following measurements are performed on the Ag alloy films 1 to 18, the comparative Ag alloy films 1 to 16 and the conventional Ag alloy films 1 to 2 of the present invention. went.

(A) Measurement of thermal conductivity of film The present invention targets 1 to 18, comparative targets 1 to 16, and conventional targets 1 to 2 are each soldered to a backing plate made of oxygen-free copper, and this is attached to a direct current magnetron sputtering apparatus. After evacuating the DC magnetron sputtering device to 1 × 10 ⁻⁴ Pa with a vacuum exhaust device, Ar gas is introduced to a sputtering gas pressure of 1.0 Pa, and then a DC power of 100 W is applied to the target with a DC power source. The plasma is generated between the Si wafer substrate with an oxide film having a diameter of 30 mm and a thickness of 1 mm disposed opposite to the target and parallel to the target with a distance of 70 mm and the target, The present invention Ag alloy films 1 to 18 and comparative Ag alloy films 1 to 16 having the composition shown in Tables 2 to 3 of 100 nm And conventional Ag alloy films 1 and 2 were formed.
The specific resistance of the Ag alloy film having a thickness of 100 nm thus formed was measured by the four-probe method, and the formula based on the Weedmann-Franz law: κ = 2.44 × 10 ⁻⁸ T / ρ (where The thermal conductivity was calculated from the specific resistance value by κ: thermal conductivity, T: absolute temperature, ρ: specific resistance), and the results are shown in Tables 3-5.

(B) Measurement of reflectance / transmittance of film In order to measure reflectance / transmittance, plasma is generated between a polycarbonate substrate having a diameter of 30 mm and a thickness of 0.6 mm and the target, and the thickness of the polycarbonate substrate is measured. : The present invention Ag alloy films 1 to 18, comparative Ag alloy films 1 to 16 and conventional Ag alloy films 1 to 2 having the composition shown in Tables 2 to 3 of 10 nm are formed, and the wavelength is in the range of 300 to 800 nm. The reflectance and transmittance are measured with a spectrophotometer, the reflectance and transmittance on the sputtering side at a wavelength of 650 nm are obtained, and “100− (reflectance + transmittance)” is defined as the absorption rate. The results are shown in Tables 3-5.

(C) Measurement of anti-aggregation property of film: Plasma is generated between a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm and the target, and the component composition shown in Tables 3 to 5 having a thickness of 20 nm on the polycarbonate substrate. Inventive Ag alloy films 1 to 18, comparative Ag alloy films 1 to 16 and conventional Ag alloy films 1 to 2 having a thickness of 20 nm are formed by spin coating. Then, a UV curable resin was applied on each of the comparative Ag alloy films 1 to 16 and the conventional Ag alloy films 1 to 2 to prepare an aggregation resistance evaluation sample. These agglomeration resistance evaluation samples are kept in a constant temperature and humidity chamber at a temperature of 90 ° C. and a relative humidity of 85% for 300 hours, and then the presence of holes generated in the film is examined by observing transmitted light with an optical microscope. The results are shown in Tables 3 to 5, and the aggregation resistance of the film was evaluated.

  From the results shown in Tables 1 to 5, the Ag alloy film obtained by performing sputtering using the present invention targets 1 to 18 is a pure Ag film obtained by performing sputtering using the conventional target 1. Compared with the thermal conductivity, reflectance, and transmittance, the absorption rate is low, which is superior in that no holes are formed due to agglomeration. Furthermore, sputtering using the conventional target 2 is performed. It can be seen that it is excellent because it has a higher thermal conductivity and a lower absorptivity than the Ag alloy film obtained by performing the above. However, an Ag alloy film manufactured using comparative targets 1 to 16 including Ca, Ga, Ir, Re, Pd, Pr, Ce, Gd, and Tb outside the scope of the present invention has reflectance, transmittance, and absorption. It can be seen that undesirable characteristics appear due to the deterioration of the rate, the decrease in thermal conductivity, and the occurrence of holes due to aggregation.

Claims (8)

Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and one or two or more selected from Pr, Ce, Gd, and Tb in total. A reflective film for an optical recording medium, comprising 0.05 to 0.2% by mass, the balance being made of Ag and inevitable impurities, wherein the Ag is made of a silver alloy containing 99% by mass or more. Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, Ir: 0.005 to 0.2% by mass, Pd: 0.01 to 0.5% by mass %, The balance is made of Ag and inevitable impurities, and the Ag is made of a silver alloy having a composition containing 99% by mass or more. Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, Re: 0.005 to 0.2 mass%, Pd: 0.01 to 0.5 mass% %, The balance is made of Ag and inevitable impurities, and the Ag is made of a silver alloy having a composition containing 99% by mass or more. Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and a total of Ir and Re: 0.005 to 0.2% by mass, Pd: 0.01 to A reflective film for an optical recording medium, comprising 0.5% by mass, the balance being made of Ag and inevitable impurities, wherein the Ag is made of a silver alloy having a composition of 99% by mass or more. Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and one or two or more selected from Pr, Ce, Gd, and Tb in total. 0.05 to 0.2% by mass, the balance being made of Ag and unavoidable impurities, and the Ag is made of a silver alloy having a composition containing 99% by mass or more. Alloy sputtering target. Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, Ir: 0.005 to 0.2% by mass, Pd: 0.01 to 0.5% by mass A silver alloy sputtering target for forming a reflective film of an optical recording medium, wherein the balance is made of Ag and inevitable impurities, and the Ag is made of a silver alloy having a composition of 99% by mass or more. Ca: 0.005 to 0.1 mass%, Ga: 0.1 to 0.6 mass%, Re: 0.005 to 0.2 mass%, Pd: 0.01 to 0.5 mass% A silver alloy sputtering target for forming a reflective film of an optical recording medium, wherein the balance is made of Ag and inevitable impurities, and the Ag is made of a silver alloy having a composition of 99% by mass or more. Ca: 0.005 to 0.1% by mass, Ga: 0.1 to 0.6% by mass, and a total of Ir and Re: 0.005 to 0.2% by mass, Pd: 0.01 to A silver alloy sputtering target for forming a reflective film for an optical recording medium, comprising 0.5% by mass, the balance being made of Ag and inevitable impurities, wherein the Ag is made of a silver alloy having a composition of 99% by mass or more .