WO2008018440A1

WO2008018440A1 - Recording layer for optical information recording medium, sputtering target, and optical information recording medium

Info

Publication number: WO2008018440A1
Application number: PCT/JP2007/065413
Authority: WO
Inventors: Hideo Fujii; Hironori Kakiuchi
Original assignee: Kabushiki Kaisha Kobe Seiko Sho
Priority date: 2006-08-08
Filing date: 2007-08-07
Publication date: 2008-02-14

Abstract

Disclosed is a recording layer for an optical information recording medium, on which a recording mark can be formed by irradiation with laser beam. The recording layer comprises an In alloy containing 20 to 65 at% of at least one element selected from Ni and Co and an In alloy containing 19 at% or less of at least one element selected from Sn, Bi, Ge and Si. Also disclosed is an optical information recording medium comprising the recording layer. Further disclosed is a sputtering target for use in the formation of the recording layer. The recording layer has a high reflectivity (initial reflectivity), a high C/N ratio and a low jitter value.

Description

Specification

Recording layer for optical information recording medium, sputtering target, and optical information recording medium

Technical field

TECHNICAL FIELD [0001] The present invention relates to a recording layer for an optical information recording medium (particularly, a write once optical disk using a blue laser), an optical information recording medium, and a sputtering target for forming a recording layer of the optical information recording medium. .

Background art

[0002] In a write once optical disk using a blue laser, an organic dye material and an inorganic material thin film are broadly studied as a recording layer. Although organic dyes have a proven track record in existing optical disks that use red lasers such as CD-R and DVD-R, organic dyes that can be recorded with blue lasers have problems in terms of light resistance. Especially in BD-R

Inorganic material thin films have been mainly studied.

[0003] As a recording method, a thin film of an inorganic material 1) phase change by laser irradiation,

2) a method of opening a hole, 3) a method of reacting between layers, etc. are known.

[0004] As a method of phase change, oxides and nitrides have been studied as a recording film. For example, in Patent Document 1, Te—O—M (M is selected from metal elements, metalloid elements, and semiconductor elements) 1 element) has been proposed.

[0005] Next, as a method for opening a hole, a low melting point metal material has been studied as a recording film. For example, in Patent Document 2, an alloy obtained by adding a 3B group, a 4B group, or a 5B group to a Sn alloy, a patent In Reference 3, A (= Si, Sn) -M (= A1, Ag, Au, Zn, Yi, Ni, Cu, Co, Ta, Fe, W, Cr, V, Ga, Pb, Mo, In , Te) alloys [however, the ratio of M is 0 · 02-0.8 (atomic ratio)]

Yes

[0006] Also, as a method of interlayer reaction, for example, in Patent Document 4, In --- (Μ, Μη, Μο) is used as the first recording layer, and Se and / or Te_0- (Ti , Pd, Zr) have been proposed. In Patent Document 5, a light containing a metal containing In as a main component as a first recording layer and a metal other than an oxide containing 5B or 6B or a semimetal as a second recording layer. A recording medium has been proposed!

[0007] When an oxide is used as a recording film, a reflective film is required to increase the reflectivity in a disk state where the reflectivity of the recording film alone is low, and to increase and decrease the modulation degree, It is necessary to provide a dielectric film such as ZnS-SiO, and the total number of films constituting the disk increases. In addition, since the recording layer itself is formed of a plurality of thin films in the method of interlayer reaction, there remains a problem that the total number of films increases.

[0008] On the other hand, the method of making holes in the low melting point metal thin film has a high reflectivity of the recording film alone and a large degree of modulation by making holes, so that the total number of films constituting the disk can be reduced. Is an advantageous scheme. However, since metal thin films generally have poor durability under high temperature and high humidity compared to oxides and nitrides, various improvements are being investigated by alloying. Since the characteristics also change, balancing various characteristics becomes a problem.

Patent Document 1: Japanese Patent No. 3638152

Patent Document 2: JP 2002-225433 A

Patent Document 3: US Patent Publication No. 2004/0241376

Patent Document 4: Japanese Patent Laid-Open No. 2003-326848

Patent Document 5: Japanese Patent No. 3499724

Disclosure of the invention

The present invention eliminates the above-mentioned problems of the prior art, has a high C / N ratio with a high reflectance (initial reflectance), and further has a low jitter value. An object of the present invention is to provide a layer (recording film), an optical recording medium provided with the recording layer, and a sputtering target for forming a recording layer of the optical information recording medium.

[0010] As a result of diligent efforts, experiments, and studies aimed at developing a recording film with a good recording sensitivity using a next-generation blue laser, the present inventors have achieved a low melting point as a base metal element. Focusing on In, which has a low environmental impact, and adding an appropriate amount of one or more elements selected from Ni and Co to it, in addition, an appropriate amount of one or more elements selected from Sn, Bi, Ge, and Si It has been found that the above-mentioned problems can be advantageously solved by the inclusion, and the present invention has been completed here. That is, the present invention relates to the following (1) to (5).

(1) A recording layer in which a recording mark is formed by irradiation with a laser beam, and the recording layer contains 20 to 65 atomic% of one or more elements selected from Ni and Co. Recording layer for recording media.

(2) The recording layer is further composed of an In alloy containing 19 atomic percent or less (excluding 0 atomic percent) of one or more elements selected from Sn, Bi, Ge, and Si. The recording layer for optical information recording media as described.

(3) An optical information recording medium comprising the recording layer according to any one of (1) to (2).

(4) A sputtering target for forming a recording layer of an optical information recording medium, comprising an In alloy power containing 20 to 65 atomic% of one or more elements selected from Ni and Co.

(5) The sputtering target is further composed of an In alloy containing 19 atomic% or less (but not including 0 atomic%) of one or more elements selected from Sn, Bi, Ge, and Si. Sputtering target for forming a recording layer of an optical information recording medium.

[0012] According to the present invention, a recording layer for an optical information recording medium having excellent characteristics having a high C / N ratio with a high reflectance (initial reflectance) and a low jitter value, and It is possible to provide an optical information recording medium. In particular, it is most suitable as a write-once optical disc using a blue laser that employs a punching method, which is an advantageous recording method with a small total number of films. In addition, according to the present invention, it is possible to provide a sputtering target effective for producing the recording layer and the optical information recording medium.

Brief Description of Drawings

FIG. 1 is a cross-sectional view showing a schematic structure of an optical disc according to an embodiment (and an example) of the present invention.

Explanation of symbols

[0014] 1: Substrate 2: Recording layer 3: Light transmission layer

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a cross-sectional view showing a schematic structure of an optical disc according to a typical embodiment (and an example described later) of the present invention. Here, 1 is a substrate, 2 is a recording layer, and 3 is a light transmission layer. [0016] Hereinafter, in the recording layer 2 of the present invention, the reason for selecting In as the main component (base metal), one or more elements selected from Ni and Co, and further Sn, Bi, Ge The reason for using an In alloy containing one or more elements selected from the group consisting of Si force, including the definition of its component range will be described.

[0017] First, In is used as a main component, In is conventionally used, for example, the melting point is much lower than other metals such as Al, Ag or Cu! /, (Melting point: Therefore, the In alloy thin film can be easily melted and deformed, and can easily exhibit excellent recording characteristics even at low laser power. In particular, when considering application to next-generation optical discs that use blue lasers, it is difficult to form recording marks with A1-based alloys. Because there is no. The In content is preferably 30 atomic% or more, and more preferably 45 atomic% or more, and particularly preferably 50 atomic% or more in order to sufficiently exhibit the above recording characteristics.

Next, in the present invention, by containing 20 to 65 atomic% of one or more of Ni and Co in In, high C / N of 8T signal can be realized while maintaining high reflectivity. . Although this detailed mechanism is not clear, it is estimated that the inclusion of Ni and Co simultaneously achieves super-smoothness, microstructure, and surface tension adjustment. A preferred lower limit for the content of one or more elements of Ni and Co is 20 atomic%, more preferably 30 atomic%, and even more preferably 40 atomic%. Moreover, the preferable upper limit is 56 atomic%, More preferably, it is 50 atomic%, More preferably, it is 45 atomic%. In addition, the preferable range as the content when adding Ni alone is 20 to 45 atomic%, more preferably 25 to 35 atomic%. Further, the preferred range for the content when Co is added alone is 35 to 56 atomic%, more preferably 40 to 56 atomic%.

[0019] If the content of one or more elements selected from Ni and Co is less than 20 atomic%, the super-smoothness of the recording film cannot be realized and the media noise becomes high. It cannot be obtained and is not preferable. On the other hand, if it exceeds 65 atomic%, the low melting point characteristics of In are greatly impaired, and the recording sensitivity is deteriorated (the recording laser power for obtaining high C / N is increased), which is not preferable.

[0020] From the viewpoint of jitter, the combined addition of Ni and Co is better than the single addition of Ni or Co. Is desirable.

[0021] On the other hand, Pt and Au as additive elements other than Ni and Co have an effect on the super-surface smoothness of the recording film, but the addition causes an extremely low reflectivity compared to the addition of Ni and Co. Therefore, sufficient reflectance cannot be secured. With V, the reflectivity can be secured, but the super-smoothness of the recording film is inferior to the addition of Ni or Co, and a sufficiently high C / N cannot be realized.

[0022] Furthermore, as described above, In contains one or more of Ni and Co in an amount of 20 to 65 atomic%, and further contains one or more of Sn, Bi, Ge and Si in an amount of 19 atomic% or less. Jitter value can be reduced. Although this mechanism is not necessarily clear, it is presumed that Sn, Bi, Ge, and Si achieve the suppression of lateral heat bleeding by lowering the thermal conductivity without increasing the melting point. The preferred lower limit for the content of one or more elements of Sn, Bi, Ge and Si is 1 atomic%, more preferably 5 atomic%. Moreover, the preferable upper limit is 19 atomic%, More preferably, it is 11 atomic%, More preferably, it is 10 atomic%.

The film thickness of the recording layer of the present invention is such that the optimum value fluctuates by inserting other layers such as metal, semi-metal, and dielectric above and below the recording layer. In this case, 8 to 25 nm, more preferably 10 to 20 nm is preferable.

[0024] The present invention is not limited to a structure formed of only one recording layer. Depending on the required range of reflectance, recording characteristics, and durability, a light transmission layer (cover layer) and a recording layer are used. A two-layer structure in which a light absorption layer is inserted between the two and a two-layer structure in which a wettability control layer is inserted between the substrate and the recording layer are also included in the range.

[0025] The recording layer made of the In alloy is preferably formed by a sputtering method because the film thickness distribution in the disk surface can be easily controlled.

[0026] The composition of the sputtering target used to form the recording layer according to the present invention is basically the same as the alloy composition of the recording layer described above, and is adjusted to the alloy composition described above as the In alloy. Thus, a desired component composition can be easily realized.

[0027] It should be noted that the sputtering target is a force S produced by a vacuum melting method or the like, and in its production, the gas component (nitrogen, oxygen, etc.) in the atmosphere and the melting furnace component are contained in the sputtering target as an impurity although they are in a small amount. May be mixed. However, the recording layer of the present invention In addition, the component composition of the sputtering target is not limited to the trace components that are inevitably mixed, so that the trace contamination of these unavoidable impurities is allowed as long as the above characteristics of the present invention are not impaired.

Example

[0028] Examples and comparative examples of the present invention will be described below. It should be noted that the present invention is not limited to this embodiment, and can be implemented with appropriate modifications within the scope that can be adapted to the gist of the present invention, all of which fall within the technical scope of the present invention. included

Yes

1) Optical disc manufacturing method

A polycarbonate substrate (thickness: 1. lmm, track pitch: 0.32 111, groove width: 0.14—0.16 mm, groove depth: 25 nm) is used as substrate 1, and DC magnetron sputtering is used. Thus, the recording layer 2 was formed. As a sputtering target, a composite target was used in which an additive element chip (5 mm square or 10 mm square) was placed on a 6-inch diameter In target. The film composition was measured by ICP emission spectrometry or ICP mass spectrometry.

[0029] The sputtering conditions, the ultimate vacuum: 3 X 10- ⁶ Torr or less, Ar gas pressure: 2 mTorr, DC spatter deposition power: was 100W. The film thickness was adjusted in the range of 12 to 21 nm so that the unrecorded SUM2 signal level of the BD-R disc (output signal correlating with reflectivity) was 280 mV or more. in the alloy, those force ^s Oh not be secured more than 280mV

Next, an ultraviolet curable resin (“BRD-130” (trade name) manufactured by Nippon Kayaku Co., Ltd.) was spin-coated thereon, followed by ultraviolet curing to provide a light transmitting layer 3 having a thickness of 100 ± 15 m. Formed. For optical disk evaluation methods, optical disk evaluation equipment (trade name “ODU_1000” manufactured by Pulstec Industrial Co., Ltd., recording laser wavelength: 405 nm, NA (numerical aperture): 0.85), spectrum analyzer (manufactured by Advantest) (R3131R)), the linear velocity is 4.9 m / s, the unrecorded SUM2 level, the recording laser power from 4 mW to 12 mW, and a length of 0.6 111 recording mark (2508 : 6111-013 (corresponding to 8 signals), and the maximum C / N value at the time of recording / reproducing at the time of signal reading at a reproducing laser power of 0.3 mW was evaluated. Time interval analyzer (Yokogawa Electric Co., Ltd.) TA520 (trade name)) with a recording laser power in the range of 4mW to 12mW! /, The shortest length 0 · 15 111, et al. 0.075m to the longest length 0 · 6m The jitter value was evaluated when random recording marks (corresponding to 2T-8T signals of 25 GB Blu-ray Disc) were randomly formed. Note that the jitter value is an index of the uncertainty of the recorded signal mark edge position, and is a value corresponding to the variance (σ) when the distribution of the rising / falling position of the edge is obtained and set as a normal distribution. It is. The jitter value is evaluated after recording three consecutive tracks, and the value in the signal of the center track is the “jitter value (during continuous three-track recording)”. At the same time, the recording laser power at which the “jitter value (during continuous three-track recording)” is the minimum value was also evaluated.

[0031] Table 1 is a table showing the unrecorded SUM2 level and the C / N value at the time of 8 再生 signal recording / reproduction on the optical recording media of the examples and comparative examples, and Table 2 shows the examples and Comparison Example Recording power and jitter values (continuous) for which the unrecorded SUM2 level on each optical recording medium, the C / N value during 8 、 signal recording playback, and the jitter value (continuous 3-track recording) are minimum values. It is a table showing (at the time of 3-track recording). Table 1 shows the case where the In alloy corresponding to the above (1) is used as the recording layer, and Table 2 shows the case where the In alloy corresponding to the above (2) is used as the recording layer. The recording laser power that gives the maximum C / N value is in the range of 6 mW to 10 mW. In the table, X is marked if the unrecorded SUM2 level is 280 mV or more, and X is marked if it is less than this. In addition, a C / N value of 50 dB or more at the time of 8T signal recording / playback is marked with ◯, and X is marked when it is less than this.

[0032] [Table 1]

[z [εεοο]

£ l S90 / L00ZdT / 13d 8 o Difficult ooz OA Alloy composition (ICP) Film thickness SU 2 8 TC / N Recording power jitter Example 18 ln-Co Co 55.6at% 13nm ○ 338mV ○ ≥50dB 7. Im 8.4% Example 19 In-Go Co 65.1at 18 ○ 379mV ○ ≥50dB 8.0m 11.6% Example 20 In-Co-Sn Co 46.1at% Sn 1.05at% 12nm O 291mV O ≥50dB 6.6mW 7.8% Example 21 In-Co-Sn Co 47.1at% Sn 1.75at% 12nm ○ 289mV ○ ≥50dB 6.OmW 7.9% Example 22 In-Co-Bi Co 29at% Bi 19at% 15nm ○ 310mV ○ ≥50dB 7.4mW 8.6% Example 23 In-Ni-Sn Ni 31at% Sn 15at% 15nm ○ 311mV ○ ≥50dB 7.8mW 8.8% Example 24 In-Ni-Sn Ni 35at% Sn 15at% 15nm ○ 365mV O ≥50dB 7.6mW 10.1% Example 25 In-Ni-Sn Ni 37at% Sn 17at% 15nm ○ 335mV O ≥50dB 8. OmW 9.9% Example 26 In-Co-Bi Co 39at% Bi 10at% 12nm ○ 280mV ○ ≥50dB 7.2m 9.5% Example 27 In-Co-Ge Co 50.4at% Ge 7. at% 14nm ○ 340mV ○ ≥50dB 6.4m 9.0% Example 28 In-Co-Si Co 42.8at% Si 6.4at% 15nm ○ 351mV O ≥50dB 7.2m 8.7% Example 29 In-Co-Ni-Sn Co 37.4at% Ni 9.2at% 12nm ○ 344mV O ≥50dB 6.6mW 6.9%

Sn 4. at%

Example 30 ln-Co-Ni-Sn Co 36.5at% Ni 10.7at% 12nm O 353mV ○ ≥50dB 6.4mW 7.3%

Sn 9.8at%

Example 31 In-Co-Ni-Sn Go 41.4at% Ni 8.5at% 12nm ○ 309mV O ≥50dB 6.4mW 6.9%

Sn 8.4at%

Example 32 In-Co-Ni-Sn Co 34.0at% Ni 16.6at% 12nm ○ 308mV ○ ≥50dB 6.2mW 6.9%

Sn 5.7at

Example 33 In-Co-i-Sn Co 34.1at% Ni 13.2at% 13nm ○ 346mV ○ ≥50dB 6.6mW 7.4%

Sn 10.9at%

Example 34 In-Co-N 卜 Sn Co 32.5at% Ni 10.7at% nm O 354mV O ≥50dB 6.6mW 7.4%

Sn 5.2at%

Example 35 In-Co-Ni-Sn Co 34.2at% Ni 14.7at% 14nm ○ 312mV O ≥50dB 6.6mW 8.1%

Sn 3.8at%

Example 36 In-Co-Ni-Sn Co 32.2at% Ni 12.5at% 11nm ○ 286mV ○ ≥50dB 6.2mW 7.8%

Sn 7.1at%

Example 37 In-Co-Ni-Sn Co 34.4at% Ni 17.5at% 13nm ○ 333mV ○ ≥50dB 6.6mW 7.8%

Sn 5.3at%

(Example 1) ln-Co Co 22at% 12nm ○ 317mV O ≥50dB 6.8m 11.6%

According to Table 1, the optical disc provided with a recording layer made of an In alloy containing one or more elements selected from Ni and Co of the present invention is smaller than the comparative example (In alloy containing Pt Au or V). The C level and the C / N value are excellent, and the deviation is high.

Also, from Table 2, an optical disc having an In alloy recording layer containing N or Co of the present invention and containing one or more elements selected from Bi Sn Ge and Si is similarly SUM2 level and C Compared to the reference example corresponding to Example 1 in Table 1 that does not contain BiSnGe and Si, both the N / N value is high, and the jitter value is also low. It turns out! [0035] Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on August 8, 2006 (Japanese Patent Application 2006-2 15754) and a Japanese patent application filed on February 8, 2007 (Japanese Patent Application 2007-029612). And based on a Japanese patent application (Japanese Patent Application No. 2007-126210) filed on May 11, 2007, which is incorporated by reference in its entirety.

Also, all references cited herein are incorporated as a whole.

Industrial applicability

According to the present invention, a recording layer for an optical information recording medium having excellent characteristics having a high C / N ratio with a high reflectance (initial reflectance) and a low jitter value, and It is possible to provide an optical information recording medium. In particular, it is most suitable as a write-once optical disc using a blue laser that employs a punching method, which is an advantageous recording method with a small total number of films. In addition, according to the present invention, it is possible to provide a sputtering target effective for producing the recording layer and the optical information recording medium.

Claims

The scope of the claims

[1] A recording layer on which a recording mark is formed by laser light irradiation, the recording layer comprising:

A recording layer for an optical information recording medium comprising an In alloy containing 20 to 65 atomic% of one or more elements selected from Ni and Co.

[2] The recording layer further contains 19 atoms of one or more elements selected from Sn, Bi, Ge, and Si.

2. The recording layer for an optical information recording medium according to claim 1, comprising an In alloy containing not more than% (however, 0 atomic% is not included! /).

[3] An optical information recording medium comprising the recording layer according to any one of claims 2 to!

[4] A sputtering target for forming a recording layer of an optical information recording medium made of an In alloy containing 20 to 65 atomic% of one or more elements selected from Ni and Co.

[5] The sputtering target according to claim 4, further comprising an In alloy containing 19 atomic% or less (excluding 0 atomic%) of one or more elements selected from Sn, Bi, Ge, and Si. Sputtering target for forming a recording layer of an optical information recording medium.