JP2007196571A - Recording layer for optical information recording medium, optical information recording medium and sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording layer for an optical information recording medium and the optical information recording medium, which are excellent in recording sensitivity characteristics, reflectivity characteristics and environment-resisting characteristics and can be applied to a next-generation type optical disk, and a sputtering target useful for forming the recording layer. <P>SOLUTION: To be disclosed is an optical recording layer for the optical information recording medium, on which a recording mark is formed by the irradiation of a laser beam and which is made of a Sn base alloy including 2-30 atomic percentage of ≥1 kind of element selected from the group consisting of group IVa elements, group Va elements, group VIa elements, group VIIa elements, Pt, Dy, Sm and Ce, a recording medium equipped with the recording layer and a sputtering target, which is used for forming the recording layer and has a composition same one as that made of the recording layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a recording layer (optical recording layer) for an optical information recording medium, an optical information recording medium, and a sputtering target for forming the optical recording layer. The recording layer for optical information recording media of the present invention is used for current CDs (Compact Discs), DVDs (Digital Versatile Discs), and next-generation optical information recording media (HD-DVDs and Blu-ray Discs). It is suitably used as a write-once optical information high-density recording medium using a blue-violet laser.

  Optical information recording media (optical discs) are roughly classified into three types according to recording / reproducing systems: a reproduction-only type, a rewritable type, and a write-once type.

  Of these, write-once type optical discs record data mainly using changes in physical properties of the recording layer material irradiated with laser light. A write-once optical disc can record information but cannot erase or rewrite it. Using such characteristics, write-once optical discs are used for CD-R, DVD-R, DVD + R, etc. that require data falsification prevention, such as document files and image files.

  As recording layer materials used for write-once optical discs, organic dye materials such as cyanine dyes, phthalocyanine dyes, and azo dyes are known, for example. When this organic dye material is irradiated with a laser beam, the dye and the substrate are decomposed, melted and evaporated by heat absorption of the dye to form a recording mark. However, when an organic dye material is used, there is a problem that the dye must be dissolved in an organic solvent and then applied onto the substrate, resulting in low productivity. There is also a problem in terms of long-term stable storage of recorded signals.

  In order to improve the weaknesses of these organic dye materials, an inorganic material thin film is used as the optical recording layer, and this thin film is irradiated with laser light to form recording marks (holes, pits, etc.) locally. A method of performing this has been proposed (Non-patent Document 1, Patent Documents 1 to 7, etc.).

  Non-Patent Document 1 discloses a technique of using a Te thin film having a low melting point and low thermal conductivity to make a hole with low laser power.

  Patent Documents 1 and 2 disclose an optical recording layer in which a reaction layer made of a Cu-based alloy containing Al and a reaction layer containing Si or the like are laminated on a substrate. In the optical recording layers shown in these documents, the region where the elements contained in each reaction layer are mixed is partially formed on the substrate by laser light irradiation, and the reflectivity changes greatly. Therefore, it is described that recording can be performed with high sensitivity using a short wavelength laser such as a blue laser.

  Patent Documents 3, 4 and 7 prevent optical recording with high C / N and reflectivity by preventing a decrease in C / N (carrier-to-noise ratio) due to a recording mark. A medium is disclosed, and a Cu-based alloy containing In as an optical recording layer (Patent Document 3), an Ag-based alloy containing Bi or the like (Patent Document 4), and an Sn-based alloy containing Bi or the like (Patent Document 7) are described. Has been.

  Patent Documents 5 and 6 relate to an optical recording layer using an Sn-based alloy. Patent Document 5 discloses an optical information recording in which two or more elements that can aggregate at least partially during heat treatment are contained in the alloy layer. A medium is disclosed. Specifically, the optical information recording medium is composed of a Sn—Cu based alloy layer containing Bi or In and having a thickness of about 1 to 8 nm, and has a high melting point and high thermal conductivity.

Patent Document 6 discloses an optical information recording layer in which an oxidizable substance that is more easily oxidized than Sn or Bi is added to an Sn—Bi alloy having excellent recording characteristics, and is excellent in a high-temperature and high-humidity environment. Emphasis is placed on showing durability.
JP 2004-5922 A JP 2004-234717 A JP 2002-172861 A JP 2002-144730 A Japanese Patent Laid-Open No. 2-117878 JP 2001-180114 A JP 2002-225433 A Appl. Phys. Lett. , Vol. 34 (1979) p. 835.

  As described above, the metal-based optical information recording layer is superior in long-term stable storage of recorded information as compared to the organic optical recording layer. There is a problem that the metal-based recording layer is oxidized by oxygen, moisture (moisture), etc., and the writing / reading characteristics are gradually deteriorated.

  In recent years, in order to cope with the higher density of recorded information, optical information recording and reproducing technology using a short wavelength laser such as a blue-violet laser has been developed. High quality signal writing / reading characteristics such as high C / N (high signal during reading and low background noise), low jitter (less fluctuation on the time axis of the playback signal), (2) high recording sensitivity ( (3) high reflectivity from the recording layer necessary for obtaining stable tracking, and (4) high corrosion resistance are required.

  However, according to the investigation by the inventors, the conventional metal-based recording layer cannot satisfy all of the above required characteristics sufficiently, and is difficult to put into practical use. However, the metal optical recording layer has the feature that the material is much more stable than the organic recording layer, and the development of a practical optical recording layer that satisfies the above required characteristics with the metal material is as follows. This is extremely important in providing users with highly reliable BD-R and HD DVD-R.

  In addition, it is desirable to employ a sputtering method with high production efficiency for the formation of the optical recording layer. A sputtering target for forming a high-quality optical recording layer, and an optical information recording medium equipped with the recording layer Offer is desired.

  The present invention has been made paying attention to such circumstances, and its purpose is not only to satisfy the required characteristics as shown in the above (1) to (4), but also to have high reliability of recording sensitivity. In addition to providing a recording layer for optical information recording made of a metal material that is inexpensive in terms of cost, an optical information recording medium including the recording layer is provided, and further useful for forming such an optical information recording layer. It is to provide a sputtering target.

  The recording layer for optical information recording according to the present invention that has solved the above-mentioned problems is a recording layer in which a recording mark is formed by irradiation with a laser beam, and the recording layer includes groups 4a, 5a, 6a. A Sn group alloy containing in the range of 2 to 30% (meaning atomic%, the same shall apply hereinafter) of at least one element selected from the group consisting of elements of Group III, Group 7a, and Pt, Dy, Sm, Ce It has a feature.

  When the recording layer according to the present invention further contains Nd and / or Y in the range of 10% or less (not including 0%) as other elements, the corrosion resistance of the recording layer is improved, and light Since the surface smoothness of the recording layer is improved, the shape characteristics of the recording mark are improved, and the jitter can be further reduced, it is recommended as a more preferable embodiment of the present invention.

  The recording layer of the present invention exhibits high recording sensitivity especially for laser light having a wavelength in the range of 350 to 700 nm, and exhibits excellent optical information writing and reading accuracy.

  The optical information recording medium of the present invention is characterized in that the optical recording layer having the above-described configuration is provided, and an optical adjustment layer and / or a dielectric layer is provided above and / or below the recording layer. It is also a preferred embodiment to have a configuration. The preferred thickness of the optical recording layer in the optical information recording medium is in the range of 1 to 50 nm when the optical recording layer or dielectric layer is provided above and / or below the optical recording layer. When not provided, it is in the range of 8 to 50 nm.

  Furthermore, the sputtering target of the present invention is a target used when the optical recording layer is formed by a sputtering method, and the first target is an element of 4a group, 5a group, 6a group, 7a group, and Pt, It consists of a Sn-based alloy containing at least one element selected from the group consisting of Dy, Sm, and Ce in a range of 2 to 30%, and the second target further contains Nd and / or Y of 10% or less ( (Not including 0%).

  In the above Sn-based alloy used in the present invention, Sn is basically responsible for its main characteristics, and the Sn content in the Sn-based alloy is desirably 40% or more, and more preferable Sn content. Is 50% or more, more preferably 60% or more. Further, the content of at least one element selected from the group consisting of 4a group, 5a group, 6a group, 7a group element and Pt, Dy, Sm, Ce is 2-30%, more preferably Is 5% or more and 25% or less, more preferably 10% or more and 20% or less.

  In another Sn-based alloy, Nd and / or Y are included as other elements in a range of 10% or less (not including 0%), but in addition to these elements, they are oxidized more than Sn. Easy metal elements may be included.

  In the Sn-based alloy according to the present invention, Sn serving as a base material has a low melting point, enables formation of a recording mark with low laser power, and includes elements of 4a group, 5a group, 6a group, 7a group, Since elements selected from Dy, Sm, and Ce are more easily oxidized than Sn, these additional elements are oxidized on the surface of the recording layer made of an Sn-based alloy to form a dense oxide film, and the recording layer is oxidized. Suppress. As a result, the corrosion resistance is improved, and the high reflectance inherent in the Sn-based alloy is maintained for a long time. Moreover, since these elements have a higher melting point than Sn, the effect of keeping the surface of the entire Sn-based alloy recording film smooth is also exhibited.

  Of the above elements, Pt is less likely to be oxidized than Sn, and oxygen or moisture that has permeated through the resin substrate or cover layer first oxidizes Sn. However, since Pt is dispersed in the Sn-based alloy recording layer during film formation by sputtering and prevents diffusion of Sn atoms in the surface direction, further growth of the Sn oxide film is suppressed, contributing to improvement of corrosion resistance. . When compared with the same amount of addition to Sn as the main component, the corrosion resistance of the recording layer to which Pt is added is slightly inferior to that of the above-described easily oxidized elements other than Pt, but compared to the additive-free Sn single recording layer. Corrosion resistance is greatly improved. Furthermore, it has been confirmed that when Pt is added, the surface smoothness of the optical recording layer is improved as compared with the case where an element that is easily oxidized is added.

  In addition to the above elements, adding an appropriate amount of Nd or Y further improves the corrosion resistance of the recording layer, and also reduces the jitter due to the improvement of the surface smoothness of the recording layer and the effect of optimizing the shape of the recording mark. It works effectively.

  In the present invention, the reason why Sn is first selected as the base metal is as follows. From the viewpoint of the reflectance of the optical recording layer, Al, Ag, Cu, etc. are superior to Sn, but the recording mark formation by laser light irradiation is much superior to Sn. This is because Sn has a melting point of about 232 ° C. and is much lower than Al (melting point is about 660 ° C.), Ag (melting point is about 962 ° C.), and Cu (melting point is about 1085 ° C.). This thin film is easily melted or deformed even at low temperatures by laser light irradiation, and exhibits excellent recording characteristics even at low laser power. In particular, in the present invention, application to a next-generation optical disk using a blue-violet laser is listed as one object, and in this case, it is difficult to form a recording mark with an Al-based alloy or the like. A base alloy was adopted.

  Next, in the first Sn-based alloy, the elements of 4a group, 5a group, 6a group, 7a group, and Pt, Dy, Sm, Ce improve the corrosion resistance and maintain high reflectivity for a long time. Furthermore, it is an effective element in that it has an action of improving the surface smoothness of the optical recording layer. In order to effectively exhibit these effects, it is necessary to contain 2% or more of at least one of the above elements. Don't be. However, if the sum of these elements exceeds 30%, the amount of Sn is relatively insufficient, and the original characteristics required for Sn, particularly the high reflectance characteristics, cannot be effectively exhibited. Considering such advantages and disadvantages, the more preferable content of the above elements is 5% or more and 25% or less, more preferably 10% or more and 20% or less.

  Preferred specific examples of the elements of 4a group, 5a group, 6a group, and 7a group include 4a group; Ti, Zr, Hf, 5a group; V, Nb, Ta, 6a group; Cr, Mo, W, 7a group; Mn, Tc, Re are mentioned.

  In addition, Nd and Y additionally contained in the second Sn-based alloy contribute to the improvement of the corrosion resistance and surface smoothness of the optical recording layer, and contribute to the optimization of the shape of the recording mark and promote the reduction of jitter. Although these effects can be exhibited even in a very small amount, it is clear that the effects appear clearly in practical use at a sum of 0.1% or more, more certainly 0.5% or more. When it is added. However, if the added amount is too large, the Sn content is relatively reduced and the original properties of Sn are impaired. Therefore, it is preferable to keep it at most 10% or less, preferably 5% or less in total.

  The optical recording layer formed of the Sn-based alloy has a thickness in the range of 1 to 50 nm depending on the structure of the optical information recording medium in order to form a reliable recording layer with stable accuracy. Good. If it is less than 1 nm, the optical recording layer is too thin, so even if an optical adjustment layer or a dielectric layer is provided above or below the optical recording layer, defects such as pores are likely to occur on the film surface of the optical recording layer. It becomes difficult to obtain satisfactory recording sensitivity. On the other hand, if the thickness exceeds 50 nm and becomes too thick, the heat given by the laser beam irradiation easily diffuses rapidly in the recording layer, and it becomes difficult to form a recording mark. From the viewpoint of reflectivity as a disc, the more preferable thickness of the recording layer is 8 nm or more and 30 nm or less, more preferably 12 nm or more and 20 nm or less when the dielectric layer or the optical adjustment layer is not provided. When providing a layer and an optical adjustment layer, they are 3 nm or more and 30 nm or less, More preferably, they are 5 nm or more and 20 nm or less.

  The preferred wavelength of the laser beam irradiated for recording is in the range of 350 to 700 nm. If it is less than 350 nm, light absorption by the cover layer (light transmission layer) becomes remarkable, making writing and reading to the optical recording layer difficult. Become. On the other hand, if the wavelength exceeds 700 nm and becomes excessive, the energy of the laser beam is reduced, and it becomes difficult to form a recording mark on the optical recording layer. From such a viewpoint, the more preferable wavelength of the laser beam used for recording information is 350 nm or more and 660 nm or less, and more preferably 380 nm or more and 650 nm or less.

  The composition of the sputtering target used to form the optical recording layer according to the present invention is basically the same as the alloy composition of the optical recording layer described above, and is described as the first and second Sn-based alloys. By adjusting to the alloy composition, the same component composition can be easily realized for the optical recording layer formed by sputtering.

  Hereinafter, the characteristics of the Sn-based alloy characterized by the present invention will be described in comparison with the prior arts disclosed in Patent Documents 1 to 7 and Non-Patent Document 1 mentioned above.

  As described above, Al, Ag, and Cu disclosed in Patent Documents 1 to 4 are slightly superior to the Sn-based alloy used in the present invention in terms of the reflectance of the optical recording layer. However, the Sn-based alloy is remarkably superior in the formation of recording marks by laser light irradiation. This is because, as described above, the melting point of Sn is remarkably lower than that of Al, Ag, and Cu, and the Sn-based alloy thin film is easily melted or deformed by laser light irradiation, and exhibits excellent recording characteristics. Seem.

  In particular, when applied to a next-generation optical disk using a blue-violet laser as irradiation light as in the present invention, when an Al thin film or the like is used as a recording layer, there is a possibility that a recording mark cannot be formed with low laser power. However, the present invention can also eliminate such concerns.

  On the other hand, according to research by the present inventors, it has been found that the alloys described in Patent Documents 5 to 7 have the following problems.

  First, Patent Document 5 discloses a 40 mass% Sn-55 mass% In-5 mass% Cu alloy (37.7 atomic% Sn-53.5 atomic% In-8.8 atomic% Cu alloy when converted to atomic%. Although an optical recording layer having a thickness of 2 to 4 nm is disclosed, a practical C / N value is difficult to obtain. Moreover, although the thickness of the alloy layer currently disclosed by this patent document is 2-4 nm, since the film thickness was too thin for the said alloy composition, the reflectance of the level which can be put to practical use was not obtained.

  Patent Document 6 discloses an optical recording layer in which an oxidizable substance that is more easily oxidized than Sn or Bi is added to an Sn—Bi alloy. However, with these alloys, a C / N value and recording sensitivity at levels exceeding those of the Sn-based alloy of the present invention were not obtained.

  Further, Patent Document 7 discloses an optical recording layer made of a Sn-based alloy having an alloy composition of 84 atomic% Sn-10 atomic% Zn-6 atomic% Sb. However, even with this Sn-based alloy, a C / N value, recording sensitivity, and reflectance at levels exceeding those of the Sn-based alloy of the present invention were not obtained.

  Also from these facts, it is clear that the optical recording layer of the present invention is a useful technique as compared with the prior art.

  1 to 4 are cross-sectional schematic views illustrating an embodiment of an optical information recording medium (optical disk) according to the present invention. Data is recorded and reproduced by irradiating a recording layer with laser light having a wavelength of about 350 to 700 nm. 1 shows a write-once optical disc that can be used. In addition, as viewed from the laser beam incident direction, (A) [and (C)] in each figure are those where the recording location is formed on the convex portion, and (B) [and (D)] are those where the recording location is formed on the concave portion. This has been illustrated.

  1 includes a support substrate 1, an optical adjustment layer 2, dielectric layers 3 and 5, a recording layer 4 sandwiched between the dielectric layers 3 and 5, and a light transmission layer 6. I have. The dielectric layers 3 and 5 are provided in order to protect the recording layer 4, thereby enabling recording information to be stored for a long time.

  2 includes a support substrate 1, a 0th recording layer group (a group of layers including an optical adjustment layer, a dielectric layer, and a recording layer) 7A, an intermediate layer 8, and a first recording layer group (an optical layer). A group of layers including an adjustment layer, a dielectric layer, and a recording layer) 7B, and a light transmission layer 6. 3 illustrates a single-layer DVD-R, single-layer DVD + R, single-layer HD DVD-R type optical disc, and FIG. 4 illustrates a double-layer DVD-R, dual-layer DVD + R, dual-layer HD DVD-R type optical disc. In the figure, reference numeral 8 denotes an intermediate layer, and reference numeral 9 denotes an adhesive layer.

  2 and 4, the group of layers constituting the 0th and first recording layer groups 7A and 7B has a three-layer structure (dielectric layer / recording layer / dielectric layer, dielectric layer / Recording layer / optical adjustment layer, recording layer / dielectric layer / optical adjustment layer, etc.) and two-layer structure (from the top of the figure, recording layer / dielectric layer, dielectric layer / recording layer, recording layer / optical adjustment layer, In addition to the optical adjustment layer / recording layer, etc., it may be composed of only one recording layer.

  In the present invention, the evaluation criteria for durability is “wavelength 405 nm before and after holding a sample in which only the recording layer 4 is formed on the support substrate 1 in an environment of temperature 80 ° C. × 85% relative humidity for 96 hours. The reflectance change rate measured using the blue laser beam is less than 15% (preferably less than 10%) ”. By the way, in general, blue lasers have a short wavelength, and the change in reflectance with respect to film deterioration is remarkable. Therefore, the durability of optical discs that record and reproduce information using blue lasers is better than when red lasers are used. Expected to be inferior. For this reason, the blue laser optical recording layer is required to have a higher level of durability than before.

  From this point of view, the above-mentioned Patent Documents 1 and 6 also examine the durability of the optical disc, but the conditions are more gentle than the present invention. Incidentally, in Patent Document 6, the durability test temperature is lower than that of the present invention (temperature 60 ° C. × 90% relative humidity for 120 hours), and in Patent Document 1, the durability test time is shorter than that of the present invention (temperature 80 (Centigrade x 85% relative humidity, hold for 50 hours). That is, in any case, the durability test for a long time at high temperature and high humidity is not performed as in the present invention.

  The optical disk according to a typical embodiment of the present invention is characterized in that, for example, an Sn-based alloy that satisfies the above-mentioned prescribed requirements is used as a material of the recording layer 4 as shown in FIGS. Materials such as the support substrate 1, the optical adjustment layer 2, and the dielectric layers 3 and 5 other than 4 are not particularly limited, and those that are normally used can be appropriately selected and used.

Specifically, the support substrate material is polycarbonate resin, norbornene resin, cyclic olefin copolymer, amorphous polyolefin, etc .; the optical adjustment layer material is Ag, Au, Cu, Al, Ni, Cr, Ti, etc. and alloys thereof; as a material for the dielectric layer, oxides such as ZnS—SiO ₂ , Si, Al, Ti, Ta, Zr, Cr, Ge, Cr, Si, Al, Nb, Mo , Nitrides such as Ti, Zn, carbides such as Ge, Cr, Si, Al, Ti, Zr, Ta, fluorides such as Si, Al, Mg, Ca, La, or a mixture thereof.

  As described above, if the optical adjustment layer or the dielectric layer is formed, the reflectivity of the disk can be increased. Therefore, the recording layer has a thickness of 1 to 50 nm, more preferably 3 to 30 nm. More preferably, it is 5-20 nm.

  In addition, if the optical recording layer having the above-described configuration defined in the present invention is used, a part or all of the optical adjustment layer 2 and the dielectric layers 3 and 5 can be omitted. The preferable film thickness in the case of a single optical recording layer is 8 to 30 nm, more preferably 12 to 20 nm.

  The optical recording layer made of the Sn-based alloy is desirably formed by a sputtering method. That is, alloy elements other than Sn used in the present invention (group 4a group, 5a group, 6a group, 7a group element, Pt, Dy, Sm, Ce, Nd, Y) have a solid solubility limit inherent to Sn in a thermal equilibrium state. However, when a thin film is formed by sputtering, the above alloy elements are uniformly dispersed in the Sn matrix, so that the film quality is homogenized and stable optical characteristics and environmental resistance are easily obtained. .

  When sputtering is performed, it is desirable to use an Sn-based alloy (hereinafter referred to as “melted Sn-based alloy target material”) produced by a melting / casting method as a sputtering target material. The structure of the melted Sn-based alloy target material is uniform, the sputtering rate is stable, and the emission angle of atoms from the target is also uniform, so that an optical recording layer having a uniform composition can be easily obtained. This is because a homogeneous and high-performance optical disk can be manufactured.

  The target material is manufactured by a vacuum melting method or the like. At that time, a small amount of gas components (nitrogen, oxygen, etc.) or melting furnace components in the atmosphere may be mixed as impurities into the target. The component composition of the optical recording layer and the target material according to the present invention does not define even the trace components that are inevitably mixed, and as long as the above characteristics of the present invention are not impaired, the trace amounts of these unavoidable impurities are mixed. Is acceptable.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the following examples are not intended to limit the present invention as a matter of course, and are appropriately modified without departing from the spirit of the preceding and following descriptions. They are also possible and are within the scope of the present invention.

Example 1
1) Manufacturing Method of Disc Using a polycarbonate substrate (thickness: 0.6 mm, diameter: 120 mm) as a disc substrate, an optical recording film was formed by DC sputtering. As the sputtering target, a composite target in which a chip of an additive element was placed on a 4-inch Sn target was used.

The sputtering conditions for forming the optical recording film were as follows: ultimate vacuum: 10 ⁻⁵ Torr or less (1 Torr = 133.3 Pa), Ar flow rate: 30 sccm, Ar gas pressure: 2 mTorr, DC sputtering film formation power: 50 W. The thickness of the recording film was controlled by changing the sputtering time between 5 and 45 seconds. The composition of the formed Sn-based alloy layer was determined by ICP emission spectroscopy and mass spectrometry.

2) Optical disk evaluation method Using an optical disk evaluation apparatus (trade name “POP120-8R” manufactured by Hitachi Computer Equipment), the laser power at which a good recording mark is formed on the recording layer is evaluated at a linear velocity of 10 m / s. did. A semiconductor laser having a wavelength of 405 nm was used as the light source, the laser spot size was 0.8 μm in diameter, and the laser was irradiated from the recording layer side. The mark shape after recording was observed with an optical microscope, and the ratio of the mark formation area to the laser irradiation area was calculated as an area ratio by image processing analysis.

  A visible / ultraviolet spectrophotometer (trade name “V-570” manufactured by JASCO Corporation) was used to measure the reflectance, and the absolute reflectance of the recording layer formed on the polycarbonate resin substrate was measured.

  For corrosion resistance, the reflectance is measured after being held in an air atmosphere at a temperature of 80 ° C. and a relative humidity of 85% for 96 hours, and the amount of decrease in reflectance (ΔR: unit%) is compared with the reflectance before treatment. Calculated.

  The surface roughness (Ra: unit: nm) was measured with an atomic force microscope (trade name “SP14000” probe station AFM manufactured by Seiko Instruments Inc .; Atomic Force Microscopy mode). The measurement range was 2.5 μm × 2.5 μm.

  The results are summarized in Table 1. However, the meanings of the symbols in the table are as follows.

(1) Initial reflectance ○: 30% or more, x: less than 30%.
(2) Laser power required for forming a recording mark A: 10 mW or more and 15 mW or less, ◯: More than 15 mW and 25 mW or less, ×: More than 25 mW.
(3) Corrosion resistance (change in reflectance ΔR)
●: Less than 10%, ◎: 10% or more and less than 15%, ○: 15% or more and less than 20%, ×: 20% or more.
(4) Surface roughness (Ra)
A: Less than 2.0 nm, O: 2.0 nm or more and 4.0 nm or less, X: More than 4.0 nm.

  As is clear from Table 1, all the examples (samples Nos. 1 to 22) that satisfy all the requirements of the present invention have good initial reflectivity and require excessive laser power to form recording marks. In addition, corrosion resistance and surface roughness are also good. On the other hand, pure Sn is inferior in corrosion resistance, has a large surface roughness, and lacks practicality. Moreover, even if it contains the alloy element prescribed | regulated by this invention, when the content exceeds a regulation range (sample No. 24), the initial reflectance is falling. Further, even if the selected alloy element is contained in an appropriate amount, if the recording film thickness is too thick (Sample No. 23), excessive laser power is required to form the recording mark, which is somewhat impractical. There are difficulties.

It is a cross-sectional schematic diagram which shows one embodiment of the optical information recording medium based on this invention. It is a cross-sectional schematic diagram which illustrates the other optical information recording medium based on this invention. It is a cross-sectional schematic diagram which illustrates further another optical information recording medium based on this invention. It is a cross-sectional schematic diagram which illustrates further another optical information recording medium based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support substrate 2 Optical adjustment layer 3, 5 Dielectric layer 4 Recording layer 6 Light transmission layer 7A, 7B Recording layer group 8 Intermediate layer 9 Adhesive layer 10 Optical disk

Claims (8)

  A recording layer in which a recording mark is formed by laser light irradiation, and the recording layer is selected from the group consisting of elements of 4a group, 5a group, 6a group, 7a group, and Pt, Dy, Sm, Ce A recording layer for an optical information recording medium, comprising an Sn-based alloy containing at least one element in a range of 2 to 30% (meaning atomic%, hereinafter the same).   2. The recording layer according to claim 1, wherein the recording layer is a Sn-based alloy containing Nd and / or Y in a range of 10% or less (not including 0%).   The recording layer according to claim 1, wherein the recording mark is formed by irradiation with any laser beam having a wavelength of 350 to 700 nm.   An optical information recording medium comprising the recording layer according to claim 1.   The optical information recording medium according to claim 4, wherein an optical adjustment layer and / or a dielectric layer is provided above and / or below the recording layer.   The optical information recording medium according to claim 4, wherein the recording layer has a thickness of 1 to 50 nm.   It consists of Sn group alloy which contains the element of 4a group, 5a group, 6a group, 7a group, and at least 1 sort (s) selected from the group which consists of Pt, Dy, Sm, and Ce in the range of 2 to 30%. A sputtering target for forming a recording layer of an optical information recording medium.   The sputtering target according to claim 7, wherein the Sn-based alloy further contains Nd and / or Y in a range of 10% or less (not including 0%) as another element.

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