JP2007301761A - Recording layer for optical information recording medium and optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording layer for an optical recording medium, which has high signal writing and reading characteristics under a high C/N and a low jitter and, at the same time, favorable recording sensitivity and reflectivity and further is highly corrosion resistant and excellent in environment resisting characteristics and can be applicable to a next generation type optical disc. <P>SOLUTION: This recording layer 4, on which recording marks are formed by being irradiated with a laser beam, is disclosed as the recording layer for the optical recording medium, in which an oxidizing layer having a thickness of 0.25-5 nm is formed on the surface of an optical information recording layer mainly made of Sn. At the same time, the optical information recording medium 10 having the recording layer is also disclosed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a recording layer (optical recording layer) for an optical information recording medium and an optical information recording medium. 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. Utilizing such characteristics, for example, it is 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 pigment material is used, the pigment must be dissolved in an organic solvent and then applied onto the substrate, which has the disadvantage of 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 method has been proposed (Non-patent Document 1, Patent Documents 1 to 9, 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 even when a short wavelength laser such as a blue laser is used.

  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 to 9 relate to an optical recording layer containing Sn as a main component. Patent Document 5 discloses an optical information recording in which an alloy layer contains two or more elements that can aggregate at least partially during heat treatment. 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. Further, in Patent Document 7, by adding other elements to Sn, the surface tension of the Sn alloy is controlled and the shape of the recording mark is optimized, so that the C / N is improved as a result.

Further, Patent Documents 8 and 9 reveal that jitter (temporal shift of recording signal) is improved when an Sn—N—O film, not an Sn alloy, is used as a recording layer.
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 Japanese Patent Laid-Open No. 2004-90610 JP 2004-276337 A Appl. Phys. Lett. , Vol. 34 (1979) p. 835

  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, (4) High corrosion resistance, etc. are required.

  However, according to the investigation by the present inventors, the conventional metal-based recording layer and the techniques disclosed in the above-mentioned Patent Documents 8 and 9 cannot sufficiently satisfy all of the above required characteristics and are difficult to put into practical use. There is. However, the metal-based optical recording layer has a feature that the material is much more stable than the organic recording layer, and a practical optical recording layer that satisfies the above-mentioned required characteristics with the metal-based material is developed. This is extremely important in providing users with a highly reliable CD-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, and it is possible to provide a technique for forming a high-quality optical recording layer and an optical information recording medium provided with the recording layer. desired.

  The present invention has been made by paying attention to such circumstances, and its purpose is not only to satisfy the required characteristics listed as (1) to (4) above, but also to have high recording sensitivity reliability and cost. In addition to providing a recording layer for optical information recording made of an inexpensive metal-based material, an optical information recording medium provided with the recording layer is provided.

  The recording layer for optical information recording according to the present invention that has solved the above problems is a recording layer in which a recording mark is formed by irradiation with a laser beam, and the recording layer is a recording layer mainly composed of Sn. It is characterized in that an oxide layer having a thickness of 0.25 to 5 nm is formed on the surface of the layer.

  The recording layer of the present invention comprises Sn as a main component and at least one selected from the group consisting of 3B group, 4B group (excluding Sn), 5B group, Pd, Cu, Ag, Au, Mg, Li. Element containing or selected from the group consisting of Sn as a main component, 4A group, 5A group, 6A group, 7A group, rare earth elements (including Sc, Y), Zn, Ni, Co Those containing at least one kind of element are preferred. Further, the preferable content in the recording layer of at least one element selected from the group consisting of the group 3B, group 4B (excluding Sn), group 5B, Pd, Cu, Ag, Au, Mg, Li is as follows. 0.1 atom% or more and 30 atom% or less, selected from the group consisting of the 4A group, 5A group, 6A group, 7A group, rare earth elements (including Sc and Y), Zn, Ni, and Co. A preferable content of at least one element in the recording layer is 2 atomic% or more and 30 atomic% or less. The recording layer preferably has a thickness of 1 nm to 50 nm, more preferably 3 nm to 30 nm.

  The optical information recording medium of the present invention is characterized by including the recording layer as a constituent element.

  In the recording layer used in the present invention, Sn is basically responsible for its main characteristics, and the Sn content in the recording layer is preferably 40 atomic% or more, and a more preferable Sn content is 50 atomic% or more, more preferably 60 atomic% or more.

  In the present invention, Sn serving as a base material of the recording layer has a low melting point, and can form a recording mark with a low laser power. In addition, by forming an oxide layer of a predetermined thickness on the surface, the initial reflectance, It is possible to provide an optical information recording layer having excellent performance in all of the shape retention, environment resistance, and surface flatness of the recording mark.

  In the present invention, Sn is selected as the main component of the optical information recording layer for the following reason.

  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 significantly lower than Al (melting point: about 660 ° C.), Ag (melting point: about 962 ° C.), and Cu (melting point: 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.

  In the present invention, Sn is the main component of the recording layer for the reasons described above. The Sn content in the recording layer is preferably 40 atomic% or more, and a more preferable Sn content is 50 atomic%. As mentioned above, More preferably, it is 60 atomic% or more.

  Moreover, the present invention is characterized in that an oxide layer having a thickness of 0.25 nm or more and 5 nm or less is formed on the surface of the recording layer containing Sn as a main component. This is to ensure a sufficient initial reflectivity while ensuring excellent environmental resistance as a recording layer. When the thickness of the oxide layer is less than 0.25 nm, the corrosion resistance is insufficient and satisfactory environmental resistance is obtained. On the other hand, if the oxide layer is too thick beyond 5 nm, the initial reflectance becomes insufficient.

  The optical recording layer contains at least one element selected from the group consisting of 3B group, 4B group (excluding Sn), 5B group, Pd, Cu, Ag, Au, Mg, Li together with Sn. The preferred content is 0.1 atomic% or more, more preferably 2 atomic% or more, and 30 atomic% or less, more preferably 20 atomic% or less.

  It is also effective to contain at least one element selected from the group consisting of 4A group, 5A group, 6A group, 7A group, rare earth elements (including Sc and Y), Zn, Ni and Co together with Sn. The preferable content is 2 atomic% or more, more preferably 5 atomic% or more, and 30 atomic% or less, more preferably 20 atomic% or less.

Incidentally, when the Sn-based recording layer contains at least one of the above-mentioned selective elements, the modification effect of the oxide layer formed on the surface of the recording layer is generally improved as compared with the recording layer of Sn alone. The environmental resistance and the initial reflectivity are further improved. The reason why such an effect is obtained is not yet fully understood, but Sn oxides include SnO and SnO ₂ , and when the ratio of the former (SnO) in the surface oxide layer is large, the film quality is poor and the heat resistance is low. However, it is thought that the percentage of SnO ₂ increases if it contains at least one selected element.

  In the present invention, as described above, an oxide layer having a predetermined thickness is formed on the surface of the Sn alloy that constitutes the optical recording layer. The thickness of the entire recording layer is preferably 1 nm or more and 50 nm or less. 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, making it difficult to form a recording mark. From such a viewpoint, the more preferable film thickness of the recording layer is 3 nm or more and 30 nm or less.

  In the present invention, the overall characteristics of the optical recording layer are enhanced by forming an oxide layer on the surface of the optical recording film formed on the substrate as described above, and the method for forming the oxide layer is not particularly limited. However, a method as exemplified below is preferable.

  (1) A method of sputtering an optical recording layer deposited on a substrate simply using an inert gas. Generally, a very small amount of oxygen or moisture is present inside the sputtering apparatus. This is because I) the vacuum sealing of the sputtering device is not complete, and the atmosphere enters the sputtering device with a very small amount. II) The sputtering device is opened to the atmosphere during equipment maintenance. This is because it is difficult to completely remove oxygen and moisture adhering to or adsorbed on the inner wall, etc. III) Oxygen and moisture are adsorbed or occluded on the substrate itself on which the optical recording layer is formed. Therefore, the surface of the optical recording layer is oxidized to form an oxide layer simply by performing a sputtering process using an inert gas.

  (2) A method of sputtering the surface of the optical recording layer using a mixed gas of an inert gas and oxygen. Rather than using oxygen and moisture that are inevitably mixed in the sputtering atmosphere, if oxidation treatment is performed using a mixed gas of inert gas such as argon and oxygen, the oxidation treatment can be performed more reliably and quantitatively. Can do.

  (3) A method combining (1) and (2) above. In this method, sputtering of the surface of the optical recording layer is started using only an inert gas, and then sputtering is performed using a mixed gas of inert gas and oxygen. According to this method, the thickness and film quality of the oxide layer are reduced. This is preferable because it can be controlled with higher accuracy.

  In addition, the preferable flow ratio of oxygen with respect to inert gas (Ar etc.) at the time of implementing the method of said (2), (3) is the range of 1-15%. By the way, if it is less than 1%, the formation rate of the oxide layer is too slow, and on the contrary, the phenomenon that the optical recording film and the oxide layer are sputtered off occurs. On the other hand, if the flow rate ratio is too high exceeding 15%, the oxide layer This is because the formation speed of the film is too high and the surface roughness increases and the density of the oxide layer is also impaired. From such a viewpoint, a more preferable oxygen flow rate ratio is 3% or more and 10% or less.

  The preferred sputtering time for forming the oxide layer varies depending on the gas pressure, gas flow rate, oxygen concentration, substrate temperature, etc., but is generally performed within the range of 3 to 120 seconds. However, since the optical recording layer forms an oxide layer even under mild sputtering conditions, it is possible to form the oxide layer by natural oxidation or photo-oxidation in some cases.

  Next, the characteristics of the optical recording layer characterized by the present invention will be described in comparison with the prior arts disclosed in Patent Documents 1 to 9 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 type 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 a 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, in order to control the amount of the oxidizable substance, a high-level thin film forming technique is necessary, and there is a problem in practical use on an industrial scale. In contrast, according to the present invention, a particularly advanced technique is not required for the production of the optical recording layer and the target material, and the object can be achieved only by using a Sn alloy having a simple composition.

  Further, Patent Document 7 discloses an optical recording layer made of an Sn alloy in which a 3B group, 4B group, 5B group element, Zn, a rare earth element, or the like is added to Sn. However, in the case of this Sn alloy, since the surface oxide layer is hardly formed by ordinary Ar sputtering, it is impossible to obtain the characteristics and environment resistance as intended in the present invention as an optical recording medium. In Patent Documents 8 and 9, Sn—N—O compounds are used as optical recording materials, but Sn, which has a low melting point, is bonded to N (nitrogen) or O (oxygen). Since the melting point is remarkably increased, the writing characteristics are deteriorated.

  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 schematic cross-sectional views illustrating an embodiment of an optical information recording medium (optical disk) according to the present invention. The write-once type can record and reproduce data by irradiating a recording layer with laser light. The optical disc is shown. 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. In addition, an oxide film having a predetermined thickness is formed on the surface of the optical recording layer in each drawing on the laser beam incident side.

  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 are as follows: “A sample in which only the recording layer 4 is formed on the support substrate 1 is held for 96 hours in an environment of a temperature of 80 ° C. and a relative humidity of 85% RH before and after. The reflectance change rate measured using a 405 nm 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% RH for 120 hours), and in Patent Document 1, the durability test time is shorter than that of the present invention (temperature 80 ° C. × 85% RH 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 disc according to a typical embodiment of the present invention uses, for example, an Sn alloy having a surface with an oxide layer formed on the surface thereof as a material for the recording layer 4 as shown in FIGS. There are features, and materials such as the support substrate 1, the optical adjustment layer 2, and the dielectric layers 3 and 5 other than the recording layer 4 are not particularly limited, and commonly used materials 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. The film thickness of the recording layer is preferably 1 to 50 nm, more preferably 3 to 30 nm, and still more preferably 5 to 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 3B, Group 4B (excluding Sn), Group 5B, Pd, Cu, Ag, Au, Mg, Li, or Group 4A, Group 5A, The elements of Group 6A, Group 7a, rare earth elements (including Sc and Y), Zn, Ni, and Co) have an intrinsic solid solubility limit with respect to Sn in a thermal equilibrium state. This is because when the thin film is formed by sputtering, 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.

  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 disk A polycarbonate substrate (thickness: 0.6 mm, diameter: 120 mm, track pitch: 0.32 μm, groove width: 0.14 to 0.16 μm, groove depth: 24 nm) is used as a disk substrate. Then, an optical recording film made of a Sn-15 atomic% Bi alloy was formed by DC sputtering. As a sputtering target, for convenience, a composite target in which a Bi chip was placed on a Sn target having a diameter of 4 inches was used.

The sputtering treatment conditions for forming the oxide layer are: ultimate vacuum: 10 ⁻⁵ Torr (about 1.33 × 10 ⁻³ Pa) or less, Ar flow rate: 30 sccm, Ar gas pressure: 0.5 to 10 mTorr, DC sputtering Film power: 50 W. The thickness of the oxide layer is 1) “Ar (28 sccm) + O ₂ ( ₂ sccm)” as a gas, or 2) “Ar gas” at the start of sputtering, and “Ar (28 sccm) + O ₂ in the middle”. (2 sccm) "was used, and the sputtering time was controlled between 5 and 45 seconds. The composition of the formed Sn-based alloy layer was determined by ICP emission spectroscopy and ICP mass spectrometry.

2) Optical disk evaluation method Using an optical disk evaluation apparatus (trade name “POP120-8R” manufactured by Hitachi Computer Equipment Co., Ltd.), the laser power at which a good recording mark is formed on the recording layer at a linear velocity of 10 m / s. evaluated. 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.

  The film thickness of the surface oxide layer was determined by X-ray photoelectron spectroscopy (XPS, trade name “PHI5400MC” manufactured by Perkin Elmer). The X-ray source was MgKα, the output was 400 W, the analysis area was in the range of 1.1 mm in diameter, and the angle between the detector and the sample was 45 °.

Note that it is possible to determine whether Sn is in a metal state or an oxidation state based on the peak energy position of the XPS spectrum. In the Sn-based alloy thin film, SnO or SnO ₂ is formed on the surface side. However, in the measurement method adopted, Ar sputtering is performed from the surface side of the thin film, and the depth of O (oxygen) atoms is increased due to the sputtering time dependence of the XPS spectrum. The vertical distribution was obtained, and the depth position at which the peak value was halved with respect to the peak value due to O atoms in the XPS spectrum of O _1s was defined as the Sn oxide layer thickness (SiO ₂ conversion). Ar sputtering was performed at about 0.25 nm / min in terms of SiO ₂ .

  In addition, the reflectance is measured using a visible / ultraviolet spectrophotometer (trade name “V-570” manufactured by JASCO Corporation), and the absolute reflectance of the recording layer formed on the polycarbonate resin substrate is measured. An initial reflectance of 30% or more was considered acceptable. For corrosion resistance, reflectivity is measured after maintaining in an air atmosphere at a temperature of 80 ° C. and a relative humidity of 85% RH for 96 hours, and the decrease in reflectivity compared to the reflectivity before treatment (ΔR: unit%) Was calculated. In the evaluation, ΔR was 3% or less and excellent (◎), more than 3%, 5% or less was good (◯), and 5% or more was bad (x).

  The surface roughness (Ra: unit nm) was measured with an atomic force microscope (trade name “SP14000” manufactured by Seiko Instruments Inc., AFM of probe station; Atomic Force Microscopy mode). The measurement range was 2.5 μm × 2.5 μm, and Ra was 2 nm or less, excellent (◎), over 2 nm, over 4 nm, good (◯), over 4 nm, poor (×).

  Judgment was made with excellent (各), good (◯), and poor (x) based on the above characteristics.

  The results are summarized in Table 1. In addition, the formability of the recording mark was 25 mW for all the samples and passed.

  As is clear from Table 1, when the oxide layer having the thickness specified in the present invention is formed, the initial reflectance, corrosion resistance, and surface roughness are all good, and the thickness of the oxide layer is particularly 0. Those within the range of .5 to 2.0 have a higher level of performance. On the other hand, if the thickness of the oxide layer is less than 0.25 nm, satisfactory corrosion resistance cannot be obtained due to insufficient thickness, and if the thickness of the oxide layer exceeds 5 nm and becomes excessively thick, the initial reflectivity decreases. At the same time, the corrosion resistance is lowered and the modification effect cannot be obtained.

  In the above, an example in which an Sn-15% Bi alloy is used as the optical recording film forming material has been shown, but Sn-10 atomic% B alloy, Sn-10 atomic% Nd alloy, Sn-10 atomic% are used in the same manner. Y alloy, Sn-30 atomic% In alloy, Sn-30 atomic% Zn alloy, Sn-15 atomic% Ni-3 atomic% Y alloy, Sn-15 atomic% Ni-10 atomic% In alloy, Sn-2 atomic% Even when the optical recording film is formed using the B-15 atomic% Y alloy, it has been confirmed that the effect of forming the oxide layer is substantially the same including the relationship between the surface oxide layer thickness and the performance. .

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 (7)

  A recording layer in which a recording mark is formed by laser light irradiation, and the recording layer has an oxide layer having a thickness of 0.25 to 5 nm formed on the surface of a recording layer containing Sn as a main component. A recording layer for an optical information recording medium.   The recording layer contains Sn as a main component and contains at least one element selected from the group consisting of 3B group, 4B group (excluding Sn), 5B group, Pd, Cu, Ag, Au, Mg, and Li. The recording layer according to claim 1.   The recording layer has Sn as a main component and at least one element selected from the group consisting of 4A group, 5A group, 6A group, 7A group, rare earth elements (including Sc and Y), Zn, Ni, and Co. The recording layer according to claim 1, comprising:   The content in the recording layer of at least one element selected from the group consisting of Group 3B, Group 4B (excluding Sn), Group 5B, Pd, Cu, Ag, Au, Mg, Li is 0. The recording layer according to claim 2, wherein the content is 1 to 30 atomic%.   The content in the recording layer of at least one element selected from the group consisting of the 4A group, 5A group, 6A group, 7A group, rare earth elements (including Sc, Y), Zn, Ni, Co, The recording layer according to claim 3, wherein the content is 2 to 30 atomic%.   The recording layer according to claim 1, wherein the recording layer has a thickness of 1 to 50 nm.   An optical information recording medium comprising the recording layer according to claim 1.