JP2009090601A - Recording layer for optical information recording medium, optical information recording medium, and sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording layer for an optical information recording medium (a recording film) having such characteristics that reflectivity (initial reflectivity) is high, an initial jitter value is low and remarkably increases (deteriorates) by continuous reproduction to become nonreproductive in a limited time, and to provide an optical recording medium having the recording layer, and a sputtering target for forming the recording layer of the optical information recording medium. <P>SOLUTION: This invention relates to the recording layer for a recordable optical information recording medium using laser beams, wherein the recording layer consists of an In-Co-Bi alloy comprising In of ≥30 atom%, Co of 30 to 50 atom% and Bi of >19 to 45 atom%. Further the optical information recording medium having the recording layer and the sputtering target for forming the recording layer are also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a recording layer for a write once optical information recording medium using a laser beam, particularly a blue laser, an optical information recording medium comprising the recording layer, and a sputtering target for forming the recording layer.

  In write-once optical information recording media (optical disks) using a blue laser, organic dye materials and inorganic material thin films have been studied as recording layers. Although organic dyes have a track record in existing optical disks using a red laser such as CD-R and DVD-R, organic dyes that can be recorded with a blue laser have a problem in terms of light resistance. Inorganic material thin films are mainly studied.

  As recording methods, there are known a method in which an inorganic material thin film undergoes a phase change by laser irradiation, 1) a method in which holes are formed, 3) a method in which an interlayer reaction occurs, and the like.

  As a method of phase change, an oxide or a nitride is considered as a recording film. For example, in Patent Document 1, Te-OM (where M is at least one selected from a metal element, a metalloid element, and a semiconductor element). Element) has been proposed.

  Next, as a method for opening a hole, a low melting point metal material is studied as a recording film. For example, in Patent Document 2, an alloy obtained by adding a 3B group, a 4B group, and a 5B group to an Sn alloy, and in Patent Document 3, A (= Si, Sn) -M (= Al, Ag, Au, Zn, Ti, Ni, Cu, Co, Ta, Fe, W, Cr, V, Ga, Pb, Mo, In, Te) alloy [However, The ratio of M is 0.02-0.8 (atomic ratio)].

  Also, as a method of interlayer reaction, for example, in Patent Document 4, the first recording layer In—O— (Ni, Mn, Mo), the second recording layer Se and / or Te—O— (Ti, Pd, Zr) ), Patent Document 5 proposes a metal as a main component of the first recording layer In, a metal other than an oxide including the second recording layer 5B or 6B, or a semimetal.

  When an oxide is used as the recording film, the reflectance of the recording film alone is low, a reflecting film is required to increase the reflectance in the optical disk state, and ZnS-SiO2 is formed above and below the recording film to increase the modulation degree. Therefore, the total number of films constituting the optical disk increases. Further, in the method of interlayer reaction, since the recording layer itself is formed of a plurality of thin films, there remains a problem that the total number of films increases.

  By the way, the method of drilling holes in the low melting point metal thin film is advantageous from the viewpoint of reducing the total number of films constituting the optical disk because the recording film alone has a high reflectivity and the modulation degree can be increased by drilling. It is a simple method. However, in general, metal thin films are inferior in durability under high temperature and high humidity compared to oxides and nitrides, so various improvements have been studied by alloying, but the reflectivity decreases due to alloying, Since optical disk characteristics also change, balancing various characteristics becomes a problem.

  Therefore, in view of these conventional problems, the present inventors have studied to provide a recording layer (recording film) for an optical information recording medium having a high reflectance (initial reflectance) and a low jitter value. In- (Ni, Co)-(Si, Bi) system has been successfully developed as a metal material that advantageously achieves these characteristics.

On the other hand, recently, from a new viewpoint such as copyright protection, a read-only DVD that cannot be played back by a drive in 48 hours, such as 48 DVD, has been studied, and a part of the product is being commercialized. However, there is a problem that by removing special resin with a grinder, it becomes possible to regenerate as usual, and in general, it is not so popular.
The inventors have further developed the above metal system in view of these new problems, and among them, particularly in the In-Co-Bi system, the initial jitter value is low due to its composition range, but the finite time. It has been found that there are some that deteriorate due to continuous reproduction with the others and others that do not deteriorate and remain low jitter values.
Japanese Patent No. 3638152 JP 2002-225433 A US Patent Publication No. 2004/0241376 JP 2003-326848 A Japanese Patent No. 3499724

  The present invention has been made on the basis of the above knowledge, and has a high reflectance (initial reflectance), an initial jitter value is low, and this is remarkably increased (deteriorated) by continuous reproduction, and cannot be reproduced in a finite time. An object of the present invention is to provide a recording layer (recording film) for an optical information recording medium having the above characteristics, an optical recording medium having the recording layer, and a sputtering target for forming a recording layer of the optical information recording medium. It is.

  That is, the invention according to claim 1 is a recording layer for a write-once optical information recording medium using laser light, wherein In is 30 atomic% or more, Co is 30 atomic% or more and 50 atomic% or less, and Bi is used. The recording layer is made of an In—Co—Bi alloy containing more than 19 atomic% and not more than 45 atomic%.

  According to a second aspect of the present invention, there is provided an optical information recording medium comprising the recording layer according to the first aspect.

  Furthermore, the invention according to claim 3 is a sputtering target for forming a recording layer for write-once type optical information recording media using laser light, wherein In is 30 atomic% or more and Co is 30 atomic% or more and 50 atomic% or less. And a sputtering target comprising an In—Co—Bi alloy containing more than 19 atomic% and not more than 45 atomic% of Bi.

  According to the present invention, the reflectivity (initial reflectivity) is high, the initial jitter value is low, and this value increases remarkably with continuous reproduction, and has excellent characteristics that the reproduction is impossible in a finite time. An optical information recording medium recording layer (recording film) and an optical recording medium including the recording layer can be provided. Moreover, according to this invention, the sputtering target effective in preparation of the recording layer and optical information recording medium which have the said outstanding characteristic can be provided.

  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.

  Hereinafter, in the recording layer 2 of the present invention, the reason why In is selected as the main component (base metal), and an In—Co—Bi alloy in which Co and Bi are included in a specific ratio (composition range) are used. The reason is described including the definition of the component range.

  First, the content of In at 30 atomic% or more with In as the main component is that In has a remarkably lower melting point than other metals such as Al, Ag, and Cu that are conventionally used (melting point: about 156.6). Therefore, the In alloy thin film is easily melted and deformed, and excellent recording characteristics can be easily exhibited even with a low laser power. In particular, when considering application to a next-generation optical disk using a blue laser, it may be difficult to form a recording mark with an Al-based alloy or the like. Because there is no. In order to exhibit the recording characteristics more sufficiently, the In content is preferably 50 atomic% or more.

  Next, in the present invention, by containing 30 atomic% or more of Co, high C / N of 8T signal can be realized while maintaining high reflectivity. Although this detailed mechanism is not clear, it is presumed that super surface smoothness, fine structure, and surface tension adjustment are realized at the same time.

  If the Co content is less than 30 atomic%, the super-surface smoothness of the recording film cannot be realized and the media noise becomes high, so a high C / N cannot be obtained, and the initial jitter value is low. The characteristic of increasing (deteriorating) due to continuous reproduction cannot be imparted. On the other hand, when Co is contained in a large amount, the low melting point characteristic of In is greatly impaired, and the recording sensitivity is deteriorated (the recording laser power for obtaining high C / N is increased).

  Furthermore, as described above, the initial jitter value is kept low by containing 30 atomic% or more and Co 30 atomic% or more and 50 atomic% or less and Bi containing 19 atomic% or more and 45 atomic% or less. In addition, it is possible to obtain a recording film having characteristics that the jitter value is greatly increased by continuous reproduction and the reproduction time is finite.

  The film thickness of the recording layer of the present invention varies optimally by inserting other layers such as metal, semi-metal, dielectric, etc. above and below the recording layer. 25 nm, more preferably 10 to 20 nm is preferable.

  The recording layer made of the In—Co—Bi alloy is preferably formed by a sputtering method from the viewpoint that the film thickness distribution within the optical disk surface can be easily controlled.

  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 can be adjusted to the alloy composition described above as an In alloy. The component composition can be easily realized.

  Note that the sputtering target is manufactured by a vacuum melting method or the like. In manufacturing the sputtering target, gas components (nitrogen, oxygen, etc.) and melting furnace components in the atmosphere may be mixed in the sputtering target as impurities even though they are in trace amounts. . However, the component composition of the recording layer and the sputtering target of the present invention does not stipulate even the trace components that are inevitably mixed, and as long as the above characteristics of the present invention are not hindered, these traces of unavoidable impurities are allowed. The

(Example)
Hereinafter, examples and comparative examples of the present invention will be described. The present invention is not limited to this embodiment, and can be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention, all of which are within the technical scope of the present invention. include.

1) Manufacturing method of optical disk A polycarbonate substrate (thickness: 1.1 mm, track pitch: 0.32 μm, groove width 0.16 μm, groove depth: 25 nm) is used as the disk substrate 1 shown in FIG. Desired metal thin films (various In alloys) were formed by sputtering. As a sputtering target, a metal chip of an alloy element was placed on a pure In target to form a film.

The sputtering conditions for the recording layer 2 formed, ultimate ^vacuum: 10 - 5 Torr or less (1 Torr = 133.3 Pa), sputtering gas total pressure: 3 mTorr, DC sputtering power were set to 100W.

  Table 1 shows the specifications of the recording layer samples of the examples of the present invention (invention examples) and comparative examples. The reflectance level in the unrecorded state (SUM2 signal is around 300 mV) was made constant by adjusting the film thickness (12 to 14 nm).

  Subsequently, an ultraviolet curable resin (“BRD-130” (trade name) manufactured by Nippon Kayaku Co., Ltd.) was spin-coated thereon, followed by ultraviolet curing to form a light transmission layer 3 having a film thickness of 10015 ± μm.

2) Optical disk evaluation method Using an optical disk evaluation apparatus ("ODU-1000" (trade name) manufactured by Pulstec Industrial Co., Ltd., recording laser wavelength: 405 nm, NA (numerical aperture): 0.85), BD-R standard After performing three-track continuous recording with an optimum recording strategy in a range compliant with the above, the change behavior of the jitter value when continuously reproduced with a reproduction laser power of 0.3 mW was evaluated. The jitter value here 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. All In-Co-Bi ternary systems used the same recording strategy.

3) Evaluation Results FIG. 2 shows the relationship between the continuous reproduction time and the jitter value in each optical recording medium.
As shown in FIG. 2, the jitter values after 5 minutes of continuous reproduction in Comparative Examples 1 to 4 are almost the same as the initial values. This is because Comparative Example 4 does not contain Bi, and Comparative Examples 1 to 3 are In-Co-Bi ternary systems, but Comparative Examples 1 and 2 contain Bi. Is less than the specified range of the present invention, and in the case of Comparative Example 3, it is considered that the Co content is less than the specified range of the present invention.
On the other hand, in the example of the present invention having a composition satisfying the specified range, the jitter value increased rapidly from the initial 9.3% as the reproduction time increased (11.3% at the reproduction time of 1 minute, 2 minutes at the time of 2 minutes). 15.5%), it turns out that it shows a tendency to saturation over time.

  Therefore, the optical information recording medium provided with the recording layer according to the present invention has an unrecorded state reflectance level (SUM2) of 280 mV or higher as shown in Table 1, and from FIG. The initial jitter value is low, and it is known that the jitter value greatly increases and changes as the continuous playback time increases. Therefore, it can be used as an optical information recording medium that is advantageous for copyright protection.

It is sectional drawing showing the schematic structure of the optical disk which concerns on embodiment (and Example) of this invention. 5 is a graph showing the relationship between continuous reproduction time and jitter value in an optical recording medium.

Explanation of symbols

  1: Substrate 2: Recording layer 3: Light transmission layer

Claims (3)

  A recording layer for write-once optical information recording media using laser light, containing 30 atomic% or more of In, 30 atomic% or more and 50 atomic% or less of Co, and Bi of 19 atomic% or more and 45 atomic% or less A recording layer comprising an In—Co—Bi alloy.   An optical information recording medium comprising the recording layer according to claim 1.   A sputtering target for forming a recording layer for a write once optical information recording medium using a laser beam, wherein In is 30 atomic% or more, Co is 30 atomic% or more and 50 atomic% or less, and Bi is 19 atomic% or more 45 A sputtering target comprising an In—Co—Bi alloy containing at most atomic%.

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