JP2012020530A - Recording layer for optical information-recording medium, optical information-recording medium, and sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording layer for an optical informaiton-recording medium having excellent recording property, and to provide the optical information-recording medium including the recording layer and a sputtering target helpful to form the recording layer.SOLUTION: The recording layer where recording is conducted by irradiation of a laser light includes: an Ag oxide; and at least one kind of the oxide selected out of a group consisting of In oxide, Sn oxide and Zn oxide.

Description

  The present invention relates to a recording layer for an optical information recording medium, an optical information recording medium, and a sputtering target useful for forming the recording layer.

  Optical information recording media (optical discs) are typified by optical discs such as CDs, DVDs, and BDs, and are roughly classified into three types according to recording and playback methods: read-only type, write once type, and rewritable type. Of these, the write-once type optical disc recording method mainly includes a phase change method for changing the phase of the recording layer, an interlayer reaction method for reacting a plurality of recording layers, a method for decomposing a compound constituting the recording layer, and a hole in the recording layer. It is roughly classified into a drilling method in which recording marks such as pits are locally formed.

In the phase change method, a material using a change in optical characteristics due to crystallization of the recording layer has been proposed as a material for the recording layer. For example, Patent Document 1 proposes a recording layer containing Te-OM (M is at least one element selected from a metal element, a metalloid element, and a semiconductor element),
Patent Document 2 proposes a recording layer containing Sb and Te.

  As the recording layer of the interlayer reaction type optical information recording medium, for example, in Patent Document 3, the first recording layer is made of an alloy containing In—O— (Ni, Mn, Mo), and the second recording layer is used. Has been proposed that is made of an alloy containing Se and / or Te element, O (oxygen), and one element selected from Ti, Pd, and Zr. In Patent Document 4, a first recording layer: a metal containing In as a main component, and a second recording layer: a metal other than an oxide or a nonmetal containing at least one element belonging to Group 5B or Group 6B is laminated. It has been proposed to record by reaction by heating or alloying.

  As a recording layer of a method for decomposing a compound constituting the recording layer, for example, Patent Document 5 shows a recording layer mainly composed of nitride, and recording can be performed by decomposing the nitride by heating. Materials to be performed and organic pigment materials are being studied.

  As the perforated recording layer, a recording layer made of a low melting point metal material has been studied. For example, Patent Document 6 proposes an alloy made of an alloy obtained by adding a 3B group, 4B group, or 5B group element to a Sn alloy. Patent Document 7 proposes a recording layer made of a Sn-based alloy containing Ni and / or Co in the range of 1 to 50 atomic%. Further, Patent Document 8 discloses a recording layer made of an In alloy containing 20 to 65 atomic percent of Co, and further containing an In alloy containing 19 atomic percent or less of one or more elements selected from Sn, Bi, Ge, and Si. It is shown. In Patent Document 9, Pd. A recording layer made of Ag and O, in which the ratio of the number of atoms of Pd, Ag, and O is controlled within a predetermined range is disclosed.

JP 2005-135568 A JP 2003-331461 A JP 2003-326848 A Japanese Patent No. 3499724 International Publication No. 2003/101750 Pamphlet JP 2002-225433 A JP 2007-196683 A Japanese Patent No. 4110194 JP 2005-238516 A

  The required characteristics required for an optical information recording medium include that a recording signal has a signal amplitude sufficient for reproduction (high modulation degree) and a high signal intensity (high C / N ratio) is required. The C / N ratio means “Carrier to Noise ratio” and is a ratio between a signal at the time of reading and a background noise output level.

However, it is difficult for the recording material disclosed as the prior art to satisfy these required characteristics with the recording material alone. In the phase change method, the reflectance of the recording layer alone is low. In order to increase the degree of modulation, and in order to increase the degree of modulation, it is necessary to provide a dielectric layer (dielectric film) such as ZnS-SiO ₂ above and below the recording layer, and the number of layers constituting the optical disk is large. Become. In addition, since the interlayer reaction method also requires a plurality of recording layers, the number of layers constituting the optical disk increases. For this reason, there is a problem that the number of film layers increases and productivity decreases. On the other hand, the perforation method has a high reflectivity of the recording layer itself and can secure a large degree of modulation, so that the number of layers constituting the optical disk can be reduced, but in achieving higher recording sensitivity, Further study is needed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide optical information capable of increasing the productivity of an optical information recording medium by satisfying the above required characteristics while reducing the number of layers of an optical disk. The object is to provide a recording layer for a recording medium, an optical information recording medium provided with the recording layer, and a sputtering target useful for forming the recording layer.

  The recording layer for an optical information recording medium according to the present invention is a recording layer on which recording is performed by laser light irradiation, and has a gist in that it contains an Ag oxide.

  In a preferred embodiment of the present invention, the recording layer for an optical information recording medium is at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide in addition to the Ag oxide. Is included.

  In a preferred embodiment of the present invention, the recording layer for an optical information recording medium does not contain a Pd oxide.

  The present invention also includes an optical information recording medium provided with the recording layer for optical information recording medium.

  In a preferred embodiment of the present invention, the optical information recording medium has a dielectric layer laminated on and / or below the optical information recording medium recording layer.

  The present invention also includes a sputtering target for forming the recording layer for an optical information recording medium. The sputtering target includes an Ag oxide; and at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide, and the remainder is an inevitable impurity. It is what you have.

  According to the present invention, a recording layer for an optical information recording medium excellent in recording sensitivity at a practical recording laser power (particularly, a recording layer for a write once optical information recording medium), and an optical information recording provided with the recording layer A medium (particularly, a write-once optical information recording medium) can be provided. Moreover, according to the present invention, a sputtering target useful for forming the recording layer can be provided.

  In the present specification, “excellent recording sensitivity” means that, as will be described in detail in the Examples section described later, a relatively low recording laser power is obtained by irradiating the recording layer with laser light (writing laser light). This means that a high C / N ratio and a high degree of modulation can be realized even if it is approximately 9 mW.

1 is a schematic diagram showing an outline of an optical information recording medium manufactured in Example 1. FIG. No. of Example 1 4 is a graph showing the result of XPS analysis for 4. No. of Example 1 4 is a TEM observation photograph of the recording layer surface.

The present inventors have intensively studied to realize a recording layer for a write once optical information recording medium having excellent recording sensitivity by irradiation with a writing laser beam. As a result, a material different from the conventional recording layer, that is, a recording layer containing Ag oxide, or preferably Ag oxide; selected from the group consisting of In oxide, Sn oxide, and Zn oxide It has been found that the intended purpose can be achieved by using a recording layer containing at least one oxide. When the recording layer is irradiated with laser light, the Ag oxide is heated by the laser light and decomposes to release oxygen (O ₂ gas), and bubbles are generated in the laser irradiated portion. As a result, the film shape changes and a mark is formed. It has been found that if such an inevitable recording method by the generation of bubbles accompanying laser irradiation is used, the recording sensitivity can be improved as compared with the prior art, and the present invention has been completed.

  In the recording system using the recording layer of the present invention, the structure of the recording layer before laser irradiation is amorphous, and the structure is amorphous after laser irradiation. Is different.

  The reason why the recording layer of the present invention is excellent in recording sensitivity is that a bubble is generated by laser irradiation and a portion where a mark is formed is a portion where no bubble is generated (that is, a portion where no mark is formed). It is conceivable that the degree of modulation could be increased by increasing the transmittance (that is, reducing the reflectance) as compared with the above.

  Further, by containing the Ag oxide in the recording layer as in the present invention, the light absorption rate of the film can be increased as compared with the recording layer containing only the In oxide without containing the Ag oxide. Therefore, it is possible to efficiently convert the laser energy of the writing light into thermal energy. Furthermore, in the present invention, preferably, the ratio (Atom) of the Ag amount in the element (Ag; at least one element selected from the group consisting of In, Sn, and Zn) constituting the oxide contained in the recording layer Since the ratio) is appropriately controlled, the laser power necessary for recording can also be controlled. As a result, according to the present invention, the recording sensitivity can be improved.

  Further, the recording layer of the present invention is different from Patent Document 9 described above in that it does not contain a Pd oxide. According to the examination results of the present inventors, the ratio (atomic ratio) of the above Ag amount is preferably controlled appropriately, so that the recording layer contains a Pd oxide as shown in the examples described later. Even without this, good characteristics were obtained.

  Hereinafter, the configuration of the recording layer according to the present invention will be described in detail. In the present specification, for convenience of explanation, at least one element selected from the group consisting of In, Sn, and Zn may be referred to as an X group element.

  As described above, the recording layer of the present invention is a recording layer on which recording is performed by laser light irradiation, and is characterized in that it contains an Ag oxide. Preferably, the recording layer of the present invention contains Ag oxide; and at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide. The recording layer does not contain Pd oxide.

The recording layer of the present invention contains Ag oxide. The form of the Ag oxide is not particularly limited as long as it can usually exist. Examples of the Ag oxide include oxides composed of Ag and oxygen (O) such as Ag ₂ O, AgO, and AgOx, and other elements that can be included in the recording layer (X group element = In, And a composite oxide (X-Agx-Oy) with at least one of Sn and Zn.

The recording layer of the present invention may contain at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide in addition to Ag oxide. These oxides are useful for controlling the film refractive index and recording sensitivity (modulation degree and C / N ratio). The forms of In oxide, Sn oxide, and Zn oxide are not particularly limited as long as they can usually exist. For example, In oxide is In ₂ O ₃ , Sn oxide is SnO or SnO ₂ Examples of Zn oxide include ZnO. In the present invention, it is sufficient if it contains at least one of the above oxides, and each of them may contain In oxide, Sn oxide, and Zn oxide alone, or may contain two or more kinds of oxides. Good. Of these, a preferred oxide is In ₂ O ₃ .

In order to obtain a recording layer having excellent recording sensitivity, an oxide (Ag oxide, preferably selected from the group consisting of In oxide, Sn oxide, and Zn oxide) constituting the recording layer of the present invention is selected. The atomic ratio of the amount of Ag occupying in the elements (at least one oxide) (Ag and group X element) (expressed by the following formula, hereinafter sometimes abbreviated as “Ag ratio”) is 2 It is preferably at least atomic percent.
Ag content (atomic%)
= {[Ag] / ([Ag] + [In] + [Sn] + [Zn])} × 100
In the formula, [Ag], [In], [Sn], and [Zn] are respectively
Ag amount (atomic%), In amount (atomic%) contained in the recording layer of the present invention,
It means Sn content (atomic%) and Zn content (atomic%). When In, Sn, and Zn are not included in the recording layer, each calculation is made as 0 atomic%.

  Here, when the Ag ratio is less than 2 atomic%, the amount of Ag oxide in the recording layer decreases and the film absorptance decreases, so that the laser power of the incident writing light cannot be efficiently converted into heat. The necessary write power is increased, which is not preferable. The Ag ratio is more preferably 5 atomic% or more. Ag ratio is 100%, that is, the recording layer may be composed only of Ag oxide.

  The recording layer of the present invention contains an Ag oxide as described above, and may contain inevitable impurities that are inevitably mixed during production. Preferably, the recording layer of the present invention contains Ag oxide; and at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide, and is unavoidably mixed during production. Impurities may be included.

  The film thickness of the recording layer depends on the structure of the optical information recording medium, such as inserting other layers such as a metal compound layer and a metal layer above and below the recording layer, but when the recording layer is used as a single layer ( In the case where a dielectric layer or an optical adjustment layer is not provided), the thickness of the recording layer is preferably 10 to 100 nm. This is because if the thickness of the recording layer is smaller than 10 nm, it is difficult to obtain a sufficient reflectance change due to recording. More preferably, it is 20 nm or more, and particularly preferably 25 nm or more. On the other hand, if the thickness of the recording layer is larger than 100 nm, it takes time to form the film, the productivity is lowered, and the laser power required for recording is increased. More preferably, it is 70 nm or less, More preferably, it is 60 nm or less.

  As described above, the recording layer of the present invention contains Ag oxide, preferably Ag oxide; and at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide. In order to obtain such a recording layer, it is preferable to form the recording layer by sputtering. The sputtering method is preferable because the film thickness distribution uniformity within the disk surface can be secured.

In order to form the recording layer containing the oxide by sputtering, it is preferable to adjust the gas flow rate as sputtering conditions. In particular, the ratio of the oxygen flow rate to the Ar (argon) flow rate is preferably 0.3 times or more, and more preferably 1.5 times or more. The ratio of the oxygen flow rate to the Ar flow rate is preferably 10.0 times or less. Other conditions in the sputtering method are not particularly limited, and a widely used method can be adopted. The gas pressure is in the range of 0.1 to 1.0 Pa, for example, and the sputtering power is in the range of 0.5 to ²⁰ W / cm ² , for example. What is necessary is just to control to a range.

  Examples of the sputtering target (hereinafter sometimes simply referred to as “target”) used in the sputtering method include a target containing an Ag oxide and the balance being an inevitable impurity.

  A preferable target is (A) an Ag oxide; and at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide, and the balance: a target that is an unavoidable impurity. Alternatively, instead of the above target (A), (B) an Ag metal target; and a metal target containing at least one element selected from the group consisting of In, Sn, and Zn are used, and these are simultaneously discharged. Then, multi-source sputtering may be performed.

  In addition, as the sputtering target of the above (A), in particular, an Ag metal powder or an Ag oxide powder; and at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide It is preferable to use a powder obtained by mixing and sintering the powder in terms of productivity, in-plane uniformity of the composition of the formed thin film, and thickness control. In the production of the sputtering target, impurities may be mixed in the sputtering target as impurities in a small amount. However, the component composition of the sputtering target of the present invention does not prescribe even the trace components that are inevitably mixed, and the trace amounts of these unavoidable impurities are allowed as long as the above characteristics of the present invention are not impaired.

The optical information recording medium of the present invention is characterized in that the recording layer is provided, and a mark is formed by the effect of O ₂ gas generated by decomposition of Ag oxide.

  In the present invention, the configuration other than the recording layer is not particularly limited, and a configuration known in the field of optical information recording media can be employed.

A dielectric layer (dielectric layer) may be provided above and / or below (at least one side) the recording layer. Examples of the dielectric layer include known ones such as ZnS—SiO ₂ , In, Sn, Si, Al, Ti, Ta, Zr, Cr, and other oxides, In, Sn, Ge, Cr, Nitrides such as Si, Al, Nb, Mo, Ti, Zn, carbides such as In, Sn, Ge, Cr, Si, Al, Ti, Zr, Ta, fluorides such as Si, Al, Mg, Ca, La Or a mixture thereof. In consideration of improvement in productivity and recording sensitivity, use of In ₂ O ₃ is preferable.

The thickness of the dielectric layer is preferably about 1 to 50 nm. If the dielectric layer is too thin, the generated O ₂ gas is not sufficiently covered and the recording sensitivity is lowered. On the other hand, if the film thickness of the dielectric layer is too large, the absorption of the entire laminated film (recording layer + dielectric layer) is reduced due to light interference, so that the required writing laser power is increased and the mark is formed. Therefore, the recording sensitivity is lowered. Considering such circumstances, the preferable film thickness when the dielectric layer is provided in the lower layer of the recording layer is generally 3 to 20 nm, and the preferable film thickness when provided in the upper layer of the recording layer is approximately 3 to 3. 30 nm.

  In addition to the dielectric layer, an optical adjustment layer may be provided between the substrate and the recording layer in order to further increase the reflectivity of the optical disk. Examples of the material of the optical adjustment layer include Ag, Au, Cu, Al, Ni, Cr, Ti, and alloys thereof.

  Further, as an optical information recording medium (optical disk), a structure in which a recording layer is laminated on a substrate in which a laser guide groove is engraved, and a light transmission layer is further laminated thereon.

  For example, examples of the material for the substrate include polycarbonate resin, norbornene resin, cyclic olefin copolymer, and amorphous polyolefin. Further, as the light transmission layer, polycarbonate or ultraviolet curable resin can be used. As a material for the light transmission layer, it is preferable that the light transmission layer has a high transmittance with respect to a laser for recording and reproduction, and has a small light absorption rate. The thickness of the substrate is, for example, 0.5 to 1.2 mm. The thickness of the light transmission layer is, for example, 0.1 to 1.2 mm.

  The recording layer of the present invention is excellent in recording characteristics. However, in order to improve the durability of the recording layer or further improve the recording characteristics, an oxide layer, a nitride layer, and a sulfide are formed on the upper layer and / or lower layer of the recording layer. It is preferable to provide a layer, a metal layer, or the like. By laminating these layers, the durability of the recording layer can be improved and the recording characteristics can be further enhanced.

  In the above, a single-layer optical disc in which one recording layer and one light transmission layer are formed is shown. However, the present invention is not limited to this, and two or more optical discs in which a plurality of recording layers and light transmission layers are stacked are shown. It may be.

  In the case of the two or more optical discs, for example, an ultraviolet curable resin or a polycarbonate is used between a recording layer and a recording layer group composed of an optical adjustment layer or a dielectric layer laminated as necessary. You may have the transparent intermediate | middle layer which consists of transparent resin etc.

  The feature of the present invention is that the recording layer described above, preferably a laminated film provided with a dielectric layer on and / or below the recording layer is employed. A substrate other than the recording layer, a light transmission layer, A method for forming the optical adjustment layer, the transparent intermediate layer, and the like is not particularly limited, and an optical information recording medium may be manufactured by a method that is usually performed.

  Examples of the optical information recording medium include CD, DVD, and BD. For example, a BD capable of recording and reproducing data by irradiating a recording layer with blue laser light having a wavelength of about 380 nm to 450 nm, preferably about 405 nm. -R is given as a specific example.

  EXAMPLES 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, and may be implemented with appropriate modifications without departing from the spirit of the preceding and following descriptions. And are within the scope of the present invention.

Example 1
In this embodiment, a recording layer of Ag oxide and In oxide is used, and the ratio of Ag element to the total of In atoms and Ag atoms contained in the recording layer (hereinafter referred to as “Ag ratio”) is the recording characteristics. The effects on the

(1) Production of optical disc A schematic diagram of the configuration of the optical disc used in this example is shown in FIG. As shown in FIG. 1, the optical disc has a structure in which a dielectric layer 2, an Ag-containing recording layer 3, a dielectric layer 4, and a light transmission layer 5 are sequentially laminated on a polycarbonate substrate 1.

  The method for producing the optical disc is as follows.

A polycarbonate substrate 1 (thickness: 1.1 mm, diameter: 120 mm, track pitch: 0.32 μm, groove depth: 25 nm) is used as a disk substrate, and the In ₂ O film is formed on the substrate 1 by DC magnetron sputtering. _As shown in Table 1, a recording layer 3 having a different Ag ratio and an In ₂ O ₃ dielectric layer 4 were formed in this order. The thickness of the recording layer is 40 nm, and the thicknesses of the In ₂ O ₃ dielectric layers respectively laminated above and below the recording layer are 10 nm both above and below.

Sputtering for forming the recording layer was performed as follows. The sputtering conditions at this time were Ar flow rate: 10 sccm, oxygen flow rate: 10 sccm, gas pressure: 0.4 Pa, DC sputtering power: 100 to 200 W, and substrate temperature: room temperature.
No. in Table 1 For No. 1, a pure In target was used. About 2-10, Ag ratio was changed by using two types of targets, In oxide target and Ag target, and forming into a film by multi-source sputtering.

  Next, an ultraviolet curable resin (“BRD-864” manufactured by Nippon Kayaku Co., Ltd.) is spin-coated on the dielectric layer 4 and then irradiated with ultraviolet rays to form a light transmission layer having a thickness of about 0.1 mm. The optical disk was obtained.

  In order to investigate the influence of the dielectric layer formation, No. 1 in Table 1 was used. Eleven optical disks were produced. This is shown in Table 1. 4, an optical disc was produced in the same manner as described above except that the dielectric layer was not formed.

  As for the component composition of the recording layer, a recording layer single layer film (without a dielectric layer) was formed under the same conditions as described above, and the recording layer single layer film was analyzed using an ICP emission analysis method.

(XPS analysis)
No. in Table 1 For No. 4, the state of Ag contained in the recording layer was analyzed by the XPS method. Specifically, qualitative analysis was performed using a broad photoelectron spectrum on the outermost surface using an X-ray photoelectron spectrometer Quantera SXM manufactured by physical Electronics. Thereafter, etching was performed in the depth direction from the surface by Ar ⁺ sputtering, and narrow-layer photoelectron spectra of the constituent elements of the film and the elements detected on the outermost surface were measured at constant depths. The composition distribution in the depth direction (atomic%) was calculated from the area intensity ratio of the narrow-range photoelectron spectrum obtained at each depth and the relative sensitivity coefficient. Moreover, the binding state was estimated from the peak position of the montage spectrum of each element.

  FIG. 2 shows a depth direction montage spectrum in an unrecorded portion of Ag and a depth direction montage spectrum in an unrecorded portion of In.

(2) Evaluation of optical disc The initial recording characteristics (recording power, C / N ratio, modulation degree) of the manufactured optical disc were evaluated as follows.

  First, using an optical disk evaluation apparatus (recording laser center wavelength: 405 nm, NA (numerical aperture): 0.85) manufactured by Pulstech Industrial Co., Ltd. “ODU-1000”) Recorded. The linear velocity was evaluated as 4.92 m / s.

For the degree of modulation (the degree of modulation at the point where the C / N ratio is maximized), the maximum reflectance and the minimum reflectance of the recording portion are measured using “DL1640” manufactured by Yokogawa Electric Corporation. Calculated.
Modulation degree (ratio) = (maximum reflectance−minimum reflectance) / (maximum reflectance)

  For the C / N ratio, the recording power at which the highest C / N ratio was obtained was measured using an R3131A spectrum analyzer manufactured by ADVANTEST. Specifically, a 0.60 μm mark (equivalent to 8T of Blu-ray Disk) is repeatedly recorded, and the signal intensity (carrier C / dB) of the 4.12 MHz frequency component when reading the signal with a reproduction laser power of 0.3 mW Then, the signal intensity (noise N / dB) of the frequency components before and after that was measured, and the C / N ratio was calculated.

  These results are also shown in Table 1. Table 1 shows the recording power when the highest C / N ratio was obtained and the highest C / N ratio.

  In this embodiment, the recording sensitivity is excellent when the modulation degree (ratio) is 0.3 or more and the C / N ratio is 45 dB or more.

  From Table 1, the Ag ratio satisfies the preferable requirements of the present invention. 2 to 11 were good in both the degree of modulation and the C / N ratio. That is, it was confirmed that good recording characteristics were exhibited from the low Ag region to the high Ag region.

Of these, No. Nos. 2 to 10 are examples in which dielectric layers are formed above and below the recording layer. 11 is an example in which a dielectric layer is not formed. No. No. 11 having a dielectric layer formed thereon. 4, the C / N ratio was improved and the degree of modulation was also improved by about twice. Therefore, it was found that a higher degree of modulation can be obtained by providing dielectric layers above and below the recording layer. The reason is considered to be that when the recording laser beam is input and the Ag oxide is decomposed, the O ₂ generated in the dielectric layer is confined so that the mark can be easily formed due to the shape change.

  FIG. 4 is a graph showing the results of XPS analysis of 4; In FIG. 2, the left figure shows the result of Ag 3d montage spectrum before recording. From this figure, no satellite peak (two locations of 372 eV and 378 eV) peculiar to the spectrum of metal Ag is observed. In FIG. 4, it can be seen that Ag exists not as an Ag metal but as an Ag oxide or an In—Ag composite oxide.

In FIG. 2, the right figure shows the 3d montage spectrum of In in the sample. From this figure, it can be seen that In is completely oxidized and takes the state of In ₂ O ₃ .

  From the above experimental results, it is expected that Ag oxide or In-Ag composite oxide is involved in the recording.

  In FIG. 4 shows a TEM observation photograph of the surface of the recording layer after laser irradiation. The observation magnification in the left figure is 45000 times, and the right figure is an enlarged view (magnification 150,000 times). From FIG. 3, generation | occurrence | production of the bubble was confirmed. From these results, it was confirmed that in the present invention example, oxygen was generated by the decomposition of the Ag oxide in the recording layer and bubbles were generated, and the recording characteristics were sufficiently enhanced by the volume expansion accompanying therewith.

Example 2
In this example, instead of the In oxide, Zn oxide (No. 2), Sn oxide (No. 3), W oxide (No. 4), and Ag oxide were used instead of the In oxide. Using the recording layer, an optical disc was produced in the same manner as in Example 1, and the recording characteristics were evaluated. In this example, the ratio of the Ag amount (Ag ratio) to the total of Ag atoms (Zn atoms, Sn atoms, or W atoms) contained in the recording layer was set to 20 atomic%. In this example, in order to obtain each desired recording layer, a metal Ag target and a metal Zn target (No. 2), a metal Ag target and a metal Sn target (No. 3), a metal Ag target and a metal W target (No. 2). Each recording layer was prepared by reacting with O ₂ gas by multi-source sputtering using 4). The sputtering conditions at this time are the same as those in the first embodiment. These results are listed in Table 2.

  For reference, in Example 1 described above, the results (No. 5 in Table 1) including In oxide and Ag oxide and the Ag ratio being 26 atomic% are shown in No. 2 of Table 2. It is described in 1.

  From Table 2, when a recording layer (No. 2, 3) containing an oxide of Sn and Zn instead of In is used, as with the recording layer (No. 1) containing In, a good modulation degree and A C / N ratio was obtained. On the other hand, when a recording layer (No. 4) containing an oxide of W was used, sufficient modulation and C / N ratio could not be obtained even when recording power was input.

1 Polycarbonate substrate 2, 4 Dielectric layer 3 Ag-containing recording layer 5 Light transmission layer

Claims (6)

A recording layer on which recording is performed by laser light irradiation,
A recording layer for optical information recording media, comprising an Ag oxide.   The recording layer for an optical information recording medium, further comprising at least one oxide selected from the group consisting of In oxide, Sn oxide, and Zn oxide.   The recording layer for an optical information recording medium according to claim 1, which does not contain a Pd oxide.   An optical information recording medium comprising the recording layer for an optical information recording medium according to claim 1.   The optical information recording medium according to claim 4, wherein a dielectric layer is laminated on and / or below the recording layer for the optical information recording medium. A sputtering target for forming a recording layer for an optical information recording medium according to claim 2 or 3,
Ag oxide;
A sputtering target comprising: at least one oxide selected from the group consisting of an In oxide, a Sn oxide, and a Zn oxide, and the balance: inevitable impurities.