HK1167925A - Optical information recording medium, and sputtering target for forming reflective film for optical information recording medium - Google Patents

Description

Optical information recording medium and sputtering target for forming reflective film of optical information recording medium

Technical Field

The present invention relates to an optical information recording medium such as a read-only BD (blu-ray disc) that performs reproduction using, for example, a blue laser beam, and a sputtering target for forming a reflective film of the optical information recording medium.

Background

Optical information recording media (optical disks) are roughly classified into 3 types, i.e., read-only type, write-once type, and rewritable type, according to the recording and reproducing principle.

Fig. 1 schematically shows a typical structure of a read-only optical information recording medium (single-layer optical disc). As shown in fig. 1, the read-only optical information recording medium has a structure in which a reflective film 2 containing Ag, Al, Au, or the like as a main component and a light transmissive layer 3 are sequentially stacked on a substrate 1 made of transparent plastic or the like. Information on a combination of irregularities called "Land pit (Land pit)" is recorded on the substrate 1, and a substrate made of polycarbonate having a thickness of 1.1mm and a diameter of 12cm, for example, is used. The light-transmitting layer 3 is formed by, for example, bonding a light-transmitting sheet or coating a light-transmitting resin and curing the same. The recorded data is reproduced by detecting a phase difference or a reflection difference of the laser beam irradiated to the optical disc.

Fig. 1 shows a single-layer optical disc in which a reflective film 2 and a light-transmitting layer 3 are formed in layers on a substrate 1 on which information formed by a combination of land and pit (recording data) is recorded, but for example, as shown in fig. 2, a two-layer optical disc having a 1 st information recording surface 11 and a 2 nd information recording surface 12 may be used. Specifically, the dual-layer optical disc of fig. 2 has a structure in which a 1 st reflective film 2A, a 1 st light-transmitting layer 3A, a 2 nd reflective film 2B, and a 2 nd light-transmitting layer 3B are sequentially stacked on a substrate 1 on which information is formed by a combination of land and pits (recording data) having irregularities is recorded, and information different from the substrate 1 is recorded in the combination of land and pits in the 1 st light-transmitting layer 3A.

As the reflective film used for an optical disk, Au, Cu, Ag, Al, and alloys containing these as main components have been generally used so far.

Among these, a reflective film mainly composed of Au has advantages of excellent chemical stability and small change over time in recording characteristics, but is extremely expensive and has a problem that a sufficiently high reflectance is not obtained for a blue laser beam (wavelength of 405nm) used for recording and reproducing, for example, BD. However, although the reflective film mainly composed of Cu is inexpensive, it is the most chemically stable of the conventional reflective film materials, and has a disadvantage of low reflectance to blue laser light, like Au, and its use is limited. On the other hand, since a reflective film mainly composed of Ag exhibits a sufficiently high reflectance in a practical wavelength range of 400 to 800nm and has high chemical stability, it is currently widely used for optical discs using blue laser.

Al exhibits a very high reflectance at a wavelength of 405nm, is inexpensive as compared with Ag and Au, but is less chemically stable than Ag-based and Au-based reflective films. Thus, in order to ensure durability, the thickness of the reflective film is sufficiently thick, for example, in the case of a DVD-ROM, the thickness of the Al-based reflective film is made sufficiently thick. However, in the case of a BD-ROM (read only blu-ray disc) using a blue laser, if the thickness of the Al-based reflective film is increased as in the conventional case, the accuracy of the recording signal (reproduction signal) is lowered (that is, the jitter value is increased), and stable reproduction cannot be performed. Further, even if the reflective film has excellent characteristics (initial reflectance and initial jitter value) immediately after formation, there is a problem that these properties deteriorate when stored for a long period of time under high-temperature and high-humidity conditions, and therefore it is preferable that the reflective film has excellent durability.

As a technique of using an Al alloy for a reflective film of an optical disc, for example, patent document 1 discloses an optical information recording medium using an Al alloy containing at least one element selected from Ge, Ti, Ni, Si, Tb, Fe, and Ag as an additive element for the reflective film.

However, patent document 1 is a technique on the premise of being applied to a DVD, and it is considered that in order to apply this technique to, for example, the BD-ROM, it is necessary to improve the accuracy of a recording signal to realize stable reproduction.

Patent document 1: international publication No. 01/008145

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical information recording medium as a reflective film of an optical information recording medium (for example, BD-ROM), which has a reflective film exhibiting an appropriate disc reflectance (hereinafter simply referred to as "reflectance") and having excellent reproduction stability, more preferably extremely excellent durability, and a sputtering target useful for forming the reflective film.

The present invention includes the following embodiments.

(1) A read-only optical information recording medium is a read-only optical information recording medium having a reflective film composed of an Al-based alloy, wherein the Al-based alloy contains 5 to 40% (in the case where nothing is specified, "%" in the composition means "a ratio of atomic%". further, in the case where Si and Ge are contained, the same applies hereinafter) of at least one element of Si and Ge.

(2) The read-only optical information recording medium according to (1) further comprising at least one element selected from the group consisting of a high-melting-point metal element and a rare earth element in an amount of 0.7 to 5% (when two or more elements are contained, the total amount is referred to hereinafter).

(3) In the read-only optical information recording medium according to (2), the high-melting-point metal element is at least one element selected from the group consisting of Ti, Fe, Mn, Ta, W, Mo, Cr, V, Zr, Nb, and Hf.

(4) In the read-only optical information recording medium according to (2), the rare earth element is at least one of Nd and Y.

(5) The read-only optical information recording medium according to any one of (1) to (4), which comprises a structure in which the reflective film and the light-transmitting layer are laminated on a substrate, and which reproduces information with a blue laser beam.

(6) A sputtering target for forming a reflective film for an optical information recording medium, which is used for forming the reflective film for the optical information recording medium described in (1), is composed of an Al-based alloy, wherein the Al-based alloy contains 5 to 40% of at least one element of Si and Ge.

(7) A sputtering target for forming a reflective film for an optical information recording medium, which is used for the formation of the reflective film for the optical information recording medium described in (2), is composed of an Al-based alloy, wherein the Al-based alloy contains 5 to 40% of at least one element selected from Si and Ge and 0.7 to 5% of at least one element selected from a refractory metal element and a rare earth element.

(8) The sputtering target according to (7), wherein the refractory metal element is at least one element selected from the group consisting of Ti, Fe, Mn, Ta, W, Mo, Cr, V, Zr, Nb and Hf.

(9) The sputtering target according to (7), wherein the rare earth element is at least one element selected from Nd and Y.

The present invention enables the realization of a reflective film which exhibits a suitable reflectance as a reflective film for an optical information recording medium (e.g., BD-ROM) and at the same time has excellent reproduction stability. Further, since at least one element selected from the group consisting of the high-melting-point metal element and the rare earth element is contained in an appropriate amount, a reflective film which can exhibit excellent durability and which can maintain these properties for a long period of time even when left to stand under high-temperature and high-humidity conditions can be realized. Therefore, it is possible to provide a read-only optical information recording medium in which the manufacturing cost is suppressed as compared with the conventional optical information recording medium using an Ag alloy for the reflective film.

The optical information recording medium of the present invention is particularly suitable for use in an optical information recording medium such as a BD-ROM which performs reproduction using a blue laser beam.

In the present invention, the term "suitable reflectance" means that the initial reflectance measured by the method described in the examples described later is in the range of 40% to 75%. The initial reflectance is preferably 50% of the lower limit. On the other hand, the upper limit is preferably 65%, and less than 60% is more preferable in view of easy realization of the following initial jitter value.

The excellent playback stability means that the initial jitter value measured by the method shown in the following examples is 6.5% or less.

The excellent durability means that, as shown in the following examples, when an accelerated environmental test is performed under an environmental condition of 80 ℃ and 85% relative humidity for 96 hours, the reflectance change amount before and after the accelerated environmental test is within ± 5%, and the jitter value before and after the accelerated environmental test is 6.5% or less.

Drawings

Fig. 1 is a sectional view schematically showing a main portion in a circumferential direction of a read-only optical information recording medium (single-layer optical disc).

Fig. 2 is a sectional view schematically showing a main portion in the circumferential direction of another read-only optical information recording medium (a dual-layer optical disc).

Description of the symbols

1 substrate

2 reflective film

3 light-transmitting layer

2A 1 st reflective film

2B 2 nd reflective film

3A the 1 st light-transmitting layer

3B 2 nd light-transmitting layer

11 st information recording surface

12 nd 2 nd information recording surface

Detailed Description

In order to achieve the above object, the present inventors have studied Al-based alloys suitable as a reflective film base material, which exhibit a suitable reflectance and excellent reproduction stability as well as excellent durability particularly as a reflective film of an optical information recording medium (for example, BD-ROM), from various viewpoints.

Specifically, first, using an Al-based alloy containing various alloying elements described in patent document 1 and the like, the influence of these alloying elements on the reflectance, the reproduction stability, and the durability was examined in detail. More specifically, various Al alloy films were formed on a polycarbonate substrate on which flat pits were formed by a sputtering method, and then a single-layer BD-ROM was prepared by forming a light-transmitting layer of an ultraviolet-curable resin. As a result, it has been found that in order to realize a reflective film which exhibits a reflectance suitable for a reflective film of an optical information recording medium (for example, BD-ROM) and is excellent in reproduction stability, Si and/or Ge is indispensable and, in order to maintain these characteristics even when left under high-temperature and high-humidity conditions for a long period of time, that is, to provide excellent durability, it is preferable to further contain a high-melting metal element and/or a rare earth element, and the object of the present invention has been achieved.

First, a case where the reflective film of the present invention contains Si and/or Ge will be described. Although some examples of the alloy elements contained in the Al alloy film are given in order to ensure only an appropriate reflectance, it has been found that it is very effective to contain Si and/or Ge among various alloy elements in order to achieve both the appropriate reflectance and excellent reproduction stability, and the present invention has been conceived. The reason why the above elements function effectively is not determined, but there are the following considerations. That is, in the case of BD, since the laser beam is reproduced by reflection and interference of the pits, the reflection behavior of the laser beam affects the reproduction characteristics. In the present invention, since the reflective film that controls the reflection behavior is made of a material containing Si and/or Ge, the optical constants of the reflective film are changed to optimize the reflective film, and as a result, it is considered effective to suppress an increase in the initial jitter value, that is, to improve the reproduction stability.

In order to fully exert the above-described effect, the content of Si and/or Ge needs to be 5% or more. If the jitter value is less than 5%, the effect of sufficiently reducing the jitter value is insufficient. The Si content is preferably 10% or more, more preferably 12% or more, and the Ge content is preferably 7% or more, more preferably 12% or more. On the other hand, the upper limit of the content of the above element is 40%. When the content of either Si or Ge is increased, the absorption rate of the Al alloy film constituting the reflection film increases, the reflectance relatively decreases, the signal intensity necessary for reproduction cannot be obtained, the initial jitter value increases, and excellent reproduction stability cannot be secured. From the viewpoint of the balance between the reflectance and the jitter value, the Si and/or Ge content is preferably 30% or less, more preferably 25% or less, and still more preferably 17% or less.

Next, a case where the reflection film of the present invention contains a refractory metal element and/or a rare earth element will be described.

The high-melting-point metal element is considered to contribute to grain refinement of the crystal grains of the reflective film. In the initial stage of depositing the reflective film by sputtering, the high-melting metal element constitutes a nucleus generation site, and the nucleus density can be increased. Therefore, the crystal grains of the deposited film are considered to be fine as compared with the case where the high melting point metal is not present. Further, the rare earth element can make the structure of the reflective film amorphous (amorpauslike). Since the rare earth element and Al have different atomic radii, it is considered that Al in the film is less likely to form a crystal lattice, and thus the surface smoothness is improved. Furthermore, after the accelerated test, the change of the crystal structure of the reflective film (for example, coarsening of crystal grains) is also suppressed, and as a result, excellent durability is exhibited.

Examples of the refractory metal element include Ti, Fe, Mn, Ta, W, Mo, Cr, V, Zr, Nb, and Hf, and preferably at least one element selected from the group consisting of Ti, Fe, and Mn. Ti, Fe and Mn are preferable because they are easily available, and their melting points are about 1200 to 1700 ℃, so that Al alloy targets by the melting method can be easily produced.

The rare earth elements include, for example, Nd, Y, Gd, La, and Dy, with Nd and Y being preferred.

In order to fully exhibit the above-mentioned effects, the content of the high-melting-point metal element and/or the rare earth element is preferably 0.7% or more, more preferably 0.8% or more. If the value is less than 0.7, the suppression of the tissue change is insufficient, and when the accelerated environmental test is performed, the jitter value is significantly larger than the initial jitter value, and the durability tends to deteriorate. On the other hand, when the amount of the high-melting metal element and/or the rare earth element exceeds 5%, the optical constant of the Al alloy film is greatly changed, so that the initial jitter value tends to be large and the reproduction stability tends to be deteriorated. Therefore, in the present invention, the content of the high melting point metal element and/or the rare earth element is preferably 5% or less, more preferably 2% or less.

In the reflective film of the present invention, the content of Si and/or Ge is substantially within the above range, and from the viewpoint of improving durability, it is preferable that the content of the high melting point metal element and/or the rare earth element (preferably, one or more elements selected from the group consisting of Ti, Fe, and Mn) is within the above range, and the balance is Al and inevitable impurities.

The reflecting film of the present invention preferably has a film thickness of 15nm or more. In the case where the reflective film of the present invention contains a predetermined amount of a high-melting metal element and/or a rare earth element, the film thickness is preferably 25nm or more, from the viewpoint of improving durability. Al forms a transparent surface oxide film (Al oxide film) in the atmosphere. Since the substantial Al alloy portion is reduced with the growth of the oxide film, the reflectance is likely to be lowered. More preferably 30nm or more. On the other hand, if the film thickness of the reflective film is too large, the film formation time is long, and the manufacturing cost increases. Therefore, the film thickness is preferably 100nm or less from the viewpoint of production efficiency.

The optical information recording medium of the present invention is characterized by having a reflective film made of an Al-based alloy satisfying the above composition, and the structure of an optical disk using the reflective film is not particularly required. The reflective film of the present invention may be, for example, the reflective film 2 of fig. 1 described above or the 1 st reflective film 2A of fig. 2 described above. Other components (such as the light-transmitting layer and the substrate) of the optical disk are not particularly limited, and a structure generally used can be employed.

For example, as the substrate 1 of fig. 1 and 2, a resin commonly used for a substrate for an optical disk, specifically, an ultraviolet curable resin, a polycarbonate resin, an acrylic resin, or the like can be used. In consideration of cost and mechanical properties, polycarbonate resin is preferably used.

The thickness of the substrate 1 is preferably in the range of about 0.4 to 1.2 mm. The depth of the pits formed in the substrate 1 is in the range of about 50 to 100 nm.

The type of the light-transmitting layers 3, 3A, and 3B in fig. 1 and 2 is not limited, and for example, an ultraviolet curable resin, a polycarbonate resin, or the like can be used. The thickness of the light-transmitting layer is preferably about 100 μm for a single-layer optical disc, and in the case of a dual-layer optical disc, the thickness of the 1 st light-transmitting layer 3A is preferably about 25 μm, and the thickness of the 2 nd light-transmitting layer 3B is preferably about 75 μm.

The reflective film of the present invention can be formed by a method such as sputtering or vapor deposition, but is preferably formed by sputtering. Since the above alloy elements can be uniformly dispersed in an Al matrix if a sputtering method is employed, a uniform film can be obtained, and stable optical characteristics and durability can be obtained.

The film forming conditions in sputtering are not particularly limited, but the following conditions are preferably employed, for example.

Substrate temperature: room temperature to 50 DEG C

The degree of vacuum reached: 1X 10^-5Torr below (1X 10)^-3Pa below)

Gas pressure at the time of film formation: 1 to 4mTorr

DC sputtering power density (DC sputtering power per unit area of target): 1.0 to 20W/cm²

In order to form the reflective film of the present invention by the sputtering method, an Al-based alloy target having a Si and/or Ge content of 5 to 40% is used as a sputtering target, and if an Al-based alloy sputtering target having a composition substantially the same as the composition required for the reflective film is used, the composition is not varied, and a reflective film having a desired composition can be formed.

From the viewpoint of improving durability, a sputtering target made of an Al-based alloy further containing 0.7 to 5% of a high-melting-point metal element (for example, one or more elements selected from the group consisting of Ti, Fe, Mn, Ta, W, Mo, Cr, V, Zr, Nb, and Hf) and/or a rare earth element (for example, Nd and/or Y), preferably one or more elements selected from the group consisting of Ti, Fe, and Mn, can be used.

The sputtering target preferably has substantially the same composition as that of the reflective film having a desired composition. If an Al-based alloy sputtering target having a composition and a composition substantially the same as those of a desired reflective film is used, the reflective film having the desired composition and composition can be formed without variation in composition. Accordingly, the sputtering target has the same ideal composition and composition as the above-described reflective film.

The chemical composition of the Al-based alloy of the sputtering target of the present invention is as described above, and the balance is Al and inevitable impurities.

The sputtering target can be produced by any of a melting and casting method, a powder sintering method, a spray forming method, and the like.

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples, and can be carried out by appropriately changing the examples within the scope conforming to the above and the following interests.

(example 1-1)

First, a substrate having a thickness of 1.1mm was obtained by injection molding of polycarbonate using a Ni stamper (stamp) having flat pits. Then, pure Al reflective films having the thicknesses shown in table 1 or Al-based alloy reflective films having various compositions were formed on the obtained substrate by a DC magnetron sputtering method. In order to form the reflective film, a composite sputtering target in which a pure metal piece for adding various alloys is disposed on a pure Al sputtering target or a pure Al sputtering target, or an Al-based alloy sputtering target is used.

The sputtering apparatus used was a multiplex sputtering apparatus (CS-200 manufactured by Nippon Kagaku Kogyo アルバツク, or SIH-S100 manufactured by Nippon Kagaku Kogyo アルバツク) capable of discharging a plurality of targets simultaneously. Sputtering conditions were argon (Ar) flow: 20sccm, argon pressure: about 0.1Pa, DC sputtering power density: 2 to 5W/cm²The degree of vacuum reached: 2.0X 10^-6The Torr is less. The composition (table 1) of the Al-based alloy reflective film formed was determined by ICP emission spectrometry, ICP mass spectrometry, or fluorescent X-ray analysis.

Next, an ultraviolet-curable resin having a film thickness of 100 μm was applied on the reflective film obtained as described above by a spin coating method, and the resin was cured by irradiation with ultraviolet light to form a light-transmitting layer. A single-layer BD-ROM having reflective films of various compositions was thus fabricated.

(measurement of initial jitter)

Then, the tilt and focus were adjusted under the following conditions using ODU-1000 manufactured by Japan パルステツク and TA-810 manufactured by Yokogawa electric Co., Ltd to minimize the jitter value, and the initial jitter value was measured. And the product with the initial jitter value below 6.5 percent is qualified.

Playback laser power: 0.35mW

Disc rotation speed: 4.98m/s

(measurement of initial reflectance)

In order to measure the reflectance, a digital oscilloscope manufactured by yowa electric corporation is used, and the reflectance (disc reflectance) is calculated from the maximum level of the reflected signal. The reflectance was within a range of 40% to 75% as a pass (indicating a suitable reflective film). These results are reported together in table 1.

In table 1, a product that has both an initial jitter value and an initial reflectance that is acceptable is determined as a, and a product other than the product is determined as B.

TABLE 1

The corresponding numerical values indicate the contents (atomic%) of the respective alloy components in the Al-based alloy film.

From table 1, the following can be seen. That is, it was found that a reflective film made of an Al-based alloy containing a predetermined amount of the components defined in the present invention had an initial reflectance within a predetermined range, a low initial jitter value, and excellent reproduction stability.

On the other hand, in the case of a pure Al film, an Al-based alloy film containing no component defined by the present invention, or a product containing the component defined by the present invention and having a content exceeding a predetermined range, the initial reflectance is not within the predetermined range, or the initial jitter value is large, and the reproduction stability is poor.

Specifically, while No.1 is a pure Al film, No.2 to 5 are not products containing Si and/or Ge as predetermined elements, and therefore have a large initial jitter value.

Nos. 6 and 14 are examples containing a predetermined element, but the initial jitter value is large because the content thereof is insufficient.

On the other hand, nos. 13 and 22 are examples containing a predetermined element, but the content thereof is too large, and therefore the initial jitter value is large or the initial reflectance is low.

Examples 1 to 2

An Al-based alloy reflective film was formed in the same manner as in example 1-1, except that an Al-based alloy reflective film having a film thickness shown in table 1 in example 1-1 or an Al-based alloy reflective film having a composition shown in tables 2 and 3 was used instead of the pure Al reflective film or the Al-based alloy reflective film having a composition shown in table 1. In example 1-2, an accelerated environment test was performed in accordance with the following procedure, in addition to the measurement of the initial jitter value and the initial disc reflectance.

(accelerated environmental test)

An accelerated environment test (constant temperature and humidity test) was performed using the BD-ROM having the reflection film formed thereon, and the BD-ROM was kept at 80 ℃ and 85% relative humidity in the atmosphere for 96 hours, and the jitter value after the test and the reflectance after the test were measured in the same manner as described above. Then, the case where the reflectance change amount before and after the accelerated environment test was within ± 5%, and both the initial jitter value (jitter value before the accelerated environment test) and the jitter value after the accelerated environment test were 6.5% or less was evaluated as excellent durability. These results are reported in tables 2 and 3. Table 2 shows that the jitter values (96h) after the accelerated environment test of Nos. 6 and 7 could not be measured. In the table, 0h represents an initial value, and 96h represents a value after the accelerated environmental test.

In tables 2 and 3, the evaluation that all of the initial jitter value, the initial reflectance and the accelerated environment test were acceptable is a, the evaluation that all of the initial jitter value and the initial reflectance were acceptable is B, and the other evaluation is C.

TABLE 2

TABLE 3

The following can be seen from table 2. That is, samples Nos. 1 to 5, in which the reflective film satisfied a predetermined composition, exhibited a suitable reflectance and also had excellent reproduction stability and durability. In addition, Nos. 6 to 15 show examples in which the amount of Si in the Al-Si-Ti alloy reflective film was kept substantially constant and the amount of Ti was changed. It is found that Nos. 6 and 7 contain Si defined in the present invention and a predetermined content, and thus exhibit suitable reflectance and excellent reproduction stability. Since nos. 8 to 13 further contain Ti in the content specified in the present invention, excellent durability can be ensured, the jitter value can be maintained low, and the amount of change in reflectance is small. Further, it is understood from Nos. 14 and 15 that if the Ti content is excessive, the initial jitter value becomes large.

From table 3, the following can be understood. That is, Nos. 16 to 25 show that the reflective film satisfies a predetermined composition, and thus exhibit an appropriate reflectance, and also have excellent reproduction stability and durability.

While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

The present application is based on the applications of japanese patent application laid out on 4/14/2009 (japanese application 2009-.

Industrial applicability

According to the present invention, a reflective film exhibiting an appropriate reflectance and excellent reproduction stability can be realized as a reflective film for an optical information recording medium (for example, BD-ROM). Further, by containing an appropriate amount of at least one element selected from the group consisting of a refractory metal element and a rare earth element, a reflective film can be realized which can maintain these properties even when left to stand under high-temperature and high-humidity conditions for a long period of time and which exhibits excellent durability. Therefore, it is possible to provide a read-only optical information recording medium in which the manufacturing cost is suppressed as compared with the conventional optical information recording medium using an Ag alloy for the reflective film. The optical information recording medium of the present invention is particularly suitable for use in an optical information recording medium such as a BD-ROM which performs reproduction using a blue laser beam.

Claims (9)

1. A read-only optical information recording medium having a reflective film, wherein the reflective film is made of an Al-based alloy, and the Al-based alloy contains at least one element selected from Si and Ge in a ratio of 5 to 40 atomic%.

2. The read-only optical information recording medium according to claim 1, further comprising at least one element selected from the group consisting of a high melting point metal element and a rare earth element in a ratio of 0.7 to 5 atomic%.

3. The read-only optical information recording medium according to claim 2, wherein the high melting point metal element is one or more elements selected from the group consisting of Ti, Fe, Mn, Ta, W, Mo, Cr, V, Zr, Nb, and Hf.

4. The read-only optical information recording medium according to claim 2, wherein the rare earth element is at least one element selected from Nd and Y.

5. The read-only optical information recording medium according to any one of claims 1 to 4, comprising a structure in which the reflective film and the light-transmitting layer are laminated on a substrate, and information is reproduced by a blue laser beam.

6. A sputtering target for forming a reflective film used for the optical information recording medium according to claim 1, comprising an Al-based alloy, wherein the Al-based alloy contains at least one element selected from Si and Ge in a ratio of 5 to 40 at%.

7. A sputtering target for forming a reflective film for an optical information recording medium according to claim 2, which comprises an Al-based alloy containing 5 to 40 atomic% of at least one element selected from Si and Ge and 0.7 to 5 atomic% of at least one element selected from high-melting-point metal elements and rare earth elements.

8. The sputtering target according to claim 7, wherein the refractory metal element is 1 or more elements selected from the group consisting of Ti, Fe, Mn, Ta, W, Mo, Cr, V, Zr, Nb, and Hf.

9. The sputtering target according to claim 7, wherein the rare earth element is at least one element of Nd and Y.