JP2007196683A - 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 writing/reading characteristics, C/N characteristics, jitter characteristics, 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: In this optical recording layer for the optical information recording medium, on which a recording mark is formed by the irradiation of a laser beam, a first mode of the recording layer is made of an Sn base alloy including 1-50 atomic percentage of Ni and/or Co, its second mode is made of an Sn base alloy including ≤30 atomic percentage of one or more kinds of elements selected from the group consisting of In, Bi and Zn in addition to the element in the first mode and its third mode is made of an Sn base alloy including 10 or less atomic percentage of rare earth elements as other elements in addition to the elements in the second mode. <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) and 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 light with a high C / N and reflectance by preventing a decrease in C / N (carrier-to-noise ratio) due to a recording mark. A recording medium is disclosed, and an 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 listed.

  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

  In recent years, in order to cope with higher recording information density, optical information recording and reproducing technology using a short wavelength laser such as a blue-violet laser has been developed. The recording layer characteristics suitable for this are (1) high quality such as high C / N (the signal at the time of reading is strong and the background noise is small), low jitter (the fluctuation on the time axis of the reproduced signal is small), etc. Signal writing / reading characteristics, (2) High recording sensitivity (can be written with low-power laser light), (3) High reflectivity from recording layer required to obtain stable tracking, (4) High durability Sex, etc. are required.

  However, according to the investigation by the present inventors, the conventional metal-based recording layer cannot sufficiently satisfy all of the above required characteristics 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 for providing users with highly reliable BD (Blu-ray Disc) -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 laser light, and the recording layer contains 1 Ni and / or Co. It is characterized by being made of a Sn-based alloy contained in a range of ˜50% (meaning of atomic%, the same applies hereinafter).

  When the recording layer according to the present invention contains at least one element selected from the group consisting of In, Bi, and Zn as a further element in a range of 30% or less (not including 0%), recording is performed. Deterioration of the characteristics due to oxidation of the layer can be suppressed, or the surface smoothness of the recording layer can be improved and recording can be achieved by adding a rare earth element in the range of 10% or less (not including 0%) as another element. The shape characteristics of the marks can be enhanced and they are a more preferred 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 made of an Sn-based alloy containing Ni and / or Co, and the second target. Is made of an Sn-base alloy containing 30% or less of at least one selected from In, Bi, and Zn, and the third target is made of an Sn-base alloy containing 10% or less of a rare earth element as another element. However, it has the characteristics.

  In the first 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 preferably 40% or more, and more preferably. The Sn content is 50% or more, more preferably 60% or more. Moreover, although content of Ni and / or Co is 1 to 50%, More preferably, it is 5% or more and 35% or less, More preferably, it is 15% or more and 25% or less.

  Further, in the second Sn-based alloy, one or more of In, Bi, and Zn are contained in the range of 30% or less as other elements. In addition to these elements, metal elements that are more easily oxidized than Sn. May be included.

  The third Sn-based alloy further contains 10% or less of rare earth elements as other elements. Examples of rare earth elements include Y, Nd, and La, and these are included alone. Or two or more of them may be included.

  In the first Sn-based alloy according to the present invention, Sn as a base material has a low melting point, can form a recording mark with a low laser power, and contains an appropriate amount of Ni and / or Co. Thus, the C / N value, the reflectance and the durability can be improved, and further the jitter can be reduced. In addition, Ni and / or Co further reduces the surface roughness of the optical recording layer, optimizes the shape of the recording mark, and effectively acts to reduce jitter.

  Further, In, Bi, and Zn defined by the second Sn-based alloy are elements that are more easily oxidized than Sn, and are effective in preventing deterioration of the characteristics of the optical recording layer due to oxidation of Sn.

  Furthermore, the rare earth element contained in the third Sn-based alloy contributes to the improvement of the durability of the optical recording film, and effectively acts to improve the surface smoothness of the recording film and optimize the shape of the recording mark. Excellent effect in reducing jitter.

  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, Ni and Co have the effect of increasing the C / N value, reflectivity and durability and reducing jitter, and further reducing the surface roughness of the optical recording layer. However, it is an effective element in that it has an effect of optimizing the shape of the recording mark, and in order to exhibit these effects effectively, it must be contained as 1% or more as (Ni + Co). However, if the total content of Ni and Co exceeds 50%, the amount of Sn becomes relatively short and the original characteristics required for Sn cannot be effectively exhibited. Considering such advantages and disadvantages, the more preferable content as (Ni + Co) is 5% or more and 35% or less, and further preferably 15% or more and 25% or less. Ni and Co may be added alone or in combination.

  In addition, In, Bi, and Zn that are additionally contained in the second Sn-based alloy are all elements that are more oxidizable than Sn, and they exhibit the effect of preventing oxidation deterioration of Sn at the expense of them. Therefore, the durability is further improved as long as the high C / N characteristics and the high reflectance are not greatly deteriorated. Although the effect of adding the above elements is exhibited even in a very small amount, the effect clearly appears in practical use when the total is added at 3% or more, more certainly at 5% or more. However, if the added amount is too large, the Sn content is relatively reduced and the original properties of Sn are impaired, so at most 30% in total and preferably 25% or less should be suppressed. In, Bi, and Zn may be added alone or in combination of two or more.

  The rare earth element additionally contained in the third Sn-based alloy contributes to improving the durability of the recording layer and the surface smoothness of the recording film, and has the effect of reducing jitter. Is preferably 0.5% or more, more preferably 1.0% or more for effectively exhibiting the above. However, if the addition amount is too large, the melting point of the optical recording film rises and it becomes difficult to form a recording mark by laser light, so it is preferable to keep it at most 10%, preferably 8% or less.

  As the rare earth element used in the present invention, an element obtained by adding Sc (scandium) and Y (yttrium) to a lanthanoid element (a total of 15 elements from La of atomic number 57 to Lu of atomic number 71 in the periodic table). Means group. Among these, Y is particularly preferable. These may be used alone, or two or more of them may be used in any combination.

  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 film, 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, making it 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 to third 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 each figure, (A) [and (C)] are examples where the recording location is formed in a convex shape, and (B) [and (D)] are examples where the recording location is formed in a concave shape. .

  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. A preferable film thickness in the case of a single optical recording layer is 8 to 50 nm, more preferably 10 to 30 nm.

  The optical recording layer made of the Sn-based alloy is desirably formed by a sputtering method. That is, alloy elements (Ni, Co, In, Bi, Zn, and rare earth elements) other than Sn used in the present invention have a specific solid solubility limit with respect to Sn in a thermal equilibrium state, but a thin film is formed by sputtering. This is because the 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.

  In the production of the target material, gas components (nitrogen, oxygen, etc.) and melting furnace components in the atmosphere may be mixed in the target material as impurities although they are in trace amounts. However, the optical recording layer or the target material of the present invention may be used. These component compositions do not stipulate even the trace components that are inevitably mixed in, and as long as the above characteristics of the present invention are not inhibited, the trace amounts of these unavoidable impurities are allowed.

  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
In this example, Sn—Ni alloy (Sn—Ni alloy, Sn—Ni—In alloy, Sn—Ni—rare earth element alloy, Sn—Ni—In—Y alloy) and Sn—Co alloy (Sn—Co alloy) , Sn—Co—Bi alloy). A similar experiment was performed on an optical recording film made of a Sn—Ni—Co alloy or a Sn—Ni— {Bi, Zn} alloy, but no substantial difference was found in the obtained results.

1) Disc production method A polycarbonate substrate (thickness: 1.1 mm, track pitch: 0.32 μm, groove width: 0.14 to 0.16 μm, groove depth: 25 nm) is used as a disk substrate, and a DC sputtering method is used. Then, an optical recording film was formed. As the sputtering target, a composite target in which a chip of an additive element was placed on a 6-inch diameter 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 gas pressure: 4 mTorr, DC sputtering power: 100 W. The thickness of the recording film was controlled by changing the sputtering time between 5 and 120 seconds.

  Subsequently, an ultraviolet curable resin (trade name “BRD-130” manufactured by Nippon Kayaku Co., Ltd.) was spin-coated, and then a light transmission layer having a thickness of 100 ± 15 μm was formed by ultraviolet curing.

2) Optical disk evaluation method Optical disk evaluation apparatus (trade name “ODU-1000” manufactured by Pulstec Corporation, recording laser wavelength: 405 nm, NA (numerical aperture): 0.85) and spectrum analyzer (trade name “manufactured by Advantest Corporation” R3131R ") at a linear velocity of 5.28 m / s, (1) noise level at an unrecorded frequency of 16.5 MHz, and (2) at a frequency of 16.5 MHz when a 2T rectangular wave is recorded on each disk. C / N, (3) recording sensitivity (recording laser power at which C / N is maximized), (4) reflectivity in disc state (based on SUM2 level measurement result of commercially available BD-RE disc, SUM2 level 320 mV Was calculated assuming that the reflectance was 16%.

The results are summarized in Table 1. However, the meanings of the symbols in the table are as follows.
(1) Noise level in an unrecorded state ●: Less than −75 dB ◎: −75 dB or more and less than −70 dB ○: −70 dB or more and less than −65 dB ×: −65 dB or more (2) C / N
●: More than 45 dB ◎: 40 dB or more, less than 45 dB ○: 35 dB or more, less than 40 dB ×: less than 35 dB (3) Recording sensitivity ●: Less than 10 mW ◎: 10 mW or more, less than 15 mW ○: 15 mW or more, less than 20 mW ×: 20 mW or more ( 4) Reflectance ◎: 15% or more, 22% or less ○: 10% or more, less than 15%, or more than 22%, less than 30% ×: Less than 10% or 30% or more

  The composition of the formed optical recording film was determined by ICP emission spectroscopy and mass spectrometry.

  First, Sn-Ni alloys (sample Nos. 1-22, 24-28 in Table 1) will be considered.

  As is clear from Table 1, when the Ni content in the Sn—Ni alloy increases, noise decreases and C / N improves. This is because the surface smoothness of the optical recording film is improved by increasing the amount of Ni. When the Ni content is in the range of 15 to 25 atomic%, excellent characteristics are obtained in all items.

  Further, when In is added to the Sn—Ni-based alloy, durability is further improved, and balance adjustment with recording characteristics (C / N, recording sensitivity) is possible. In Table 1, only examples containing In are shown, but it has been confirmed by experiments that even if Bi or Zn is added instead of In, the same tendency as in the In addition examples is observed. .

  Further, when a rare earth element is added to the Sn—Ni alloy, the surface smoothness and durability are further improved. In particular, regarding the read waveform, the Sn-5 atom% Ni-5 atom% Y alloy film had less noise component than the Sn-5 atom% Ni-5 atom% Nd alloy film.

  As a comprehensive evaluation, the optical recording films (samples Nos. 1 to 22) satisfying the prescribed requirements of the present invention have the contents of the optical recording film (sample No. 23) made of only Sn, Ni and the like defined by the present invention. It can be seen that the film has characteristics superior to those of optical recording films (samples Nos. 24-28) that deviate from the requirements.

  A tendency similar to that of the above-described Sn—Ni-based alloy is the same as that of sample No. made of Sn—Co-based alloy. It was also seen for 29-31. Table 1 does not show an example in which the Co content in the Sn-Co alloy is changed or an example in which a rare earth element is further added. However, an alloy containing a Co content specified in the present invention or a rare earth element is further included. The thing has confirmed by experiment that the outstanding characteristic is acquired by all the items. Moreover, it has been confirmed by experiments that the same effect as described above can be obtained even if In or Zn is used instead of Bi.

Example 2
The upper part (deposited after the recording film; between the cover layer and the recording layer) or the lower part (formed on the substrate) of the Sn-15 atomic% Ni-3 atomic% Y alloy prepared in Example 1 above. Then, a recording film is formed; between the substrate and the recording layer) using a ZnS-SiO ₂ target having a diameter of 4 inches, a disk in which a dielectric film is inserted by high frequency sputtering is prepared. The disk was evaluated. The sputtering conditions were: ultimate vacuum: 10 ⁻⁵ Torr or less, Ar gas pressure: 2 mTorr, and high-frequency sputtering power: 200 W. The film thickness was controlled by changing the sputtering time between 5 and 120 seconds.

  The results are summarized in Table 2. The meanings of symbols in Table 2 are the same as those in Table 1.

  As is clear from Table 2, since the reflectivity at the disc increases when the dielectric layer is provided, it is possible to relatively reduce the film thickness of the recording layer, and "noise", "C / N" The balance between “value” and “recording sensitivity” is improved.

Example 3
For the samples shown in Examples 1 and 2, with the optical recording film having no light transmission layer exposed, “blue light having a wavelength of 405 nm before and after being held in an environment of temperature 80 ° C. × relative humidity 85% for 96 hours” The test was conducted on the environmental resistance condition that the reflectance change rate measured using laser light satisfies less than 15% (preferably less than 10%). In this test, a spectral absolute reflectance was measured using a visible / ultraviolet spectrophotometer “V-570” manufactured by JASCO Corporation. As a result, it was confirmed that all the optical recording films satisfying the prescribed requirements of the present invention satisfy this environmental resistance condition.

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 (10)

  A recording layer in which a recording mark is formed by laser light irradiation, and the recording layer is made of an Sn-based alloy containing Ni and / or Co in a range of 1 to 50% (meaning atomic%, the same applies hereinafter). A recording layer for an optical information recording medium.   2. The recording layer according to claim 1, wherein the recording layer is a Sn-based alloy further containing at least one selected from the group consisting of In, Bi, and Zn in a range of 30% or less (not including 0%). .   The recording layer according to claim 1, wherein the recording layer is a Sn-based alloy containing a rare earth element of 10% or less (not including 0%) as another element.   The recording layer according to any one of claims 1 to 3, wherein a 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 5, 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 5, wherein the recording layer has a thickness of 1 to 50 nm.   A sputtering target for forming a recording layer of an optical information recording medium, comprising an Sn-based alloy containing 1 to 50% of Ni and / or Co.   The sputtering according to claim 8, wherein the Sn-based alloy further contains at least one element selected from the group consisting of In, Bi, and Zn as a further element in a range of 30% or less (not including 0%). ·target.   The sputtering target according to claim 8 or 9, wherein the Sn-based alloy further contains 10% or less (excluding 0%) of a rare earth element as another element.

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