JP2006331619A - Optical recording medium, sputtering target and azo-metal chelate dye - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium for high-density recording or high-speed recording having a preferable recording characteristic in a wide range of recording linear velocity and an excellent light resistance. <P>SOLUTION: The optical recording medium includes at least a recording layer formed by an organic dye and a reflection layer containing metal arranged on a substrate having a coaxial or a spiral groove. Recording is performed with the minimum mark length less than 0.4 μm or with a recording linear velocity not smaller than 35.0 m/s. The guide groove on the substrate has a track pitch not greater than 0.8 μm, a groove width not greater than 0.4 μm, and a recording layer film thickness in the groove not greater than 70 nm. The organic dye single layer forming the recording layer has a dye holding ratio not greater than 70% in Wool scale 5 (light resistance test) of the light irradiation condition shown in ISO-105-B02. The differentiation value dR/dλ (%/nm) of the reflection ratio R of the reflection layer for the wavelength λ in the air is not greater than 3 in the wavelength band from 300 nm to 500 nm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording medium that can be recorded and reproduced by laser light, and to a sputtering target and an azo metal chelate dye used in the optical recording medium. More specifically, the present invention has good recording characteristics at a wide recording linear velocity and is light resistant. The present invention relates to an optical recording medium for high-density recording or high-speed recording, which has excellent properties, and a sputtering target and an azo metal chelate dye used for the optical recording medium.

  Currently, various optical recording media such as CD-R, CD-RW, DVD-R, and DVD-RW can store large amounts of information and are easily accessible at random. It is widely recognized as a storage device and is becoming popular. Furthermore, it is desired to increase the recording density by increasing the amount of information handled.

  Among various optical recording media, an optical recording medium having a recording layer containing an organic dye, such as CD-R and DVD-R, is relatively inexpensive and compatible with a read-only optical recording medium. Especially widely used.

  In general, the current optical recording medium has a recording layer composed of an alloy thin film layer or an organic dye-containing thin film layer on a transparent disk substrate, and has a reflective layer on the opposite side of the substrate through the recording layer, It has a laminated structure having a protective layer covering these recording layers and reflective layers, and performs recording / reproduction with a laser beam through a substrate.

  As the reflective layer, a metal or alloy thin film is generally used (see Patent Document 1), and gold, silver, a silver alloy or the like is often used among them. Silver, which is the center of these alloys, has been put to practical use because it is relatively inexpensive and provides high reflectivity.

  As for the copper alloy, for example, Patent Document 2 describes a reflective layer containing a silver-copper alloy or a silver-palladium-copper alloy. Patent Document 3 describes a reflective layer provided with an alloy thin film containing less than 40% silver on copper. Patent Document 4 describes a copper alloy reflective layer and target containing Ag and Ti. However, they are all optical recording media having a low linear velocity recording speed of less than 2.0 m / s. The present invention also relates to an optical recording medium having a low recording density.

Japanese Patent Publication No. 7-105065 Japanese Patent Laid-Open No. 4-49539 JP-A-4-364240 International Publication No. WO2002 / 021524 Pamphlet

  In recent years, along with the increase in recording density, high-speed recording of drives has progressed, and high-speed recording of 28 m / s has been put into practical use in DVD-R, and development for further high-speed recording has been accelerated. In such high-speed recording, there is a problem that a recording margin cannot be obtained. This problem is observed, for example, as a phenomenon that a recording power range in which a good recording jitter value can be obtained is narrow, or a waveform distortion occurs in a recording mark as recording is performed with increasing recording power.

The present invention has been made in view of the above problems.
That is, an object of the present invention is an optical recording medium for high-density recording or high-speed recording, having good recording characteristics at a wide recording linear velocity, and excellent in “practical” light resistance. An optical recording medium is provided.
Another object of the present invention is to provide an optical recording medium suitable for high-speed recording.
Another object of the present invention is to provide a sputtering target for producing a reflective layer of an optical recording medium excellent in light resistance and recording characteristics.
Another object of the present invention is to provide a predetermined organic dye used for a recording layer of an optical recording medium suitable for high-speed recording.

  As a result of intensive studies in view of the above problems, the present inventors have found the following items and completed the present invention. In other words, when the organic dye forming the recording layer is formed as a single layer, the dye retention rate before and after the light resistance test is 80% or more, more preferably 90% or more in the recording layer used in the low-speed recording medium. Therefore, for the purpose of high-density recording or high-speed recording, the composition of the dye is adjusted to 70% or less, which is not sufficiently good for practical use. In addition, a reflective layer having a composition in which the differential value dR / dλ (% / nm) of the reflectance R with respect to the wavelength λ in the air of the reflective layer is 3 or less in a wavelength region of 300 to 500 nm is used. It has been found that by these combinations, an excellent optical recording medium can be obtained not only at high speed recording but also at a wide recording linear velocity, and excellent in “practical” light resistance.

That is, the gist of the present invention is to have a recording layer made of at least an organic dye and a reflective layer containing a metal on a substrate having concentric or spiral grooves, and the shortest mark length is less than 0.4 μm. Alternatively, in an optical recording medium for recording at a recording linear velocity of 35.0 m / s or more, the track pitch of the guide groove on the substrate is 0.8 μm or less, the groove width is 0.4 μm or less, and the recording layer film in the groove The organic dye single layer forming the recording layer has a dye retention of 70 or less according to the following definition in the Wool scale 5 (light resistance test) under the light irradiation conditions shown in ISO-105-B02. % Or less, and the differential value dR / dλ (% / nm) of the reflectance R with respect to the wavelength λ in the air of the reflective layer is 3 or less in a wavelength region of 300 nm to 500 nm. Wherein it consists in the optical recording medium.
[Dye retention]
The ratio of absorbance before and after the light resistance test at the maximum absorption wavelength of the coating film of the organic dye single layer forming the recording layer in the wavelength region of 300 to 800 nm, that is, {(absorbance after test) / (absorbance before test)} X100 (%) is defined as a dye retention rate.

（一般式（１）中、Ｒ¹は、水素原子又はＣＯ₂Ｒ³で示されるエステル基（ここで、Ｒ³は、直鎖もしくは分岐のアルキル基、又は、シクロアルキル基を表わす。）を表わす。Ｒ²は、直鎖又は分岐のアルキル基を表わす。Ｘ¹及びＸ²のうち、少なくともいずれか一方はＮＨＳＯ₂Ｙ基（ここで、Ｙは、少なくとも２つのフッ素原子で置換されている直鎖又は分岐のアルキル基を表わす。）を表わすとともに、残りは水素原子を表わす。Ｒ⁴及びＲ⁵はそれぞれ独立して、水素原子、直鎖若しくは分岐のアルキル基、又は直鎖若しくは分岐のアルコキシ基を表わす。Ｒ⁶、Ｒ⁷、Ｒ⁸及びＲ⁹はそれぞれ独立して、水素原子又は炭素数１若しくは２のアルキル基を表わす。尚、前記ＮＨＳＯ₂Ｙ基からＨ⁺が脱離してＮＳＯ₂Ｙ^-（陰性）基となり、上記一般式（１）で表されるアゾ系化合物は金属イオンと配位結合を形成する。） Another gist of the present invention is that a recording layer containing at least an organic dye and a reflective layer containing a metal are provided on a substrate having concentric or spiral grooves, and the shortest mark length is less than 0.4 μm. Or an optical recording medium for recording at a recording linear velocity of 35.0 m / s or more, wherein the recording layer is an organic dye, an azo compound represented by the following general formula (1), a metal ion of Zn, An optical recording medium comprising at least an azo metal chelate dye comprising:

(In the general formula (1), R ¹ represents a hydrogen atom or an ester group represented by CO ₂ R ³ (where R ³ represents a linear or branched alkyl group or a cycloalkyl group). R ² represents a linear or branched alkyl group, and at least one of X ¹ and X ² is an NHSO ₂ Y group (where Y is substituted with at least two fluorine atoms) And the remainder represents a hydrogen atom, R ⁴ and R ⁵ each independently represent a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkyl group. R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms, wherein H ⁺ is eliminated from the NHSO ₂ Y group. NSO ₂ Y ^- (negative) I and group Thus, the azo compound represented by the general formula (1) forms a coordinate bond with the metal ion.)

Another aspect of the present invention is to manufacture the reflective layer of an optical recording medium having a recording layer containing at least an organic dye and a reflective layer containing a metal on a substrate having concentric or spiral grooves. A sputtering target to be used, comprising at least a material represented by the following composition B.
[Composition (B)]
50at% ≦ Cu ≦ 97at%
3at% ≦ Ag ≦ 50at%
0.05at% ≦ X ≦ 10at%
(Here, X represents at least one element selected from the group consisting of Zn, Al, Pd, In, Sn, Cr, and Ni, provided that the total amount of Cu, Ag, and X is 100 at% or less. .)

  Another gist of the present invention is that a recording layer containing at least an organic dye and a reflective layer containing a metal are provided on a substrate having concentric or spiral grooves, and the shortest mark length is less than 0.4 μm. Or an azo metal chelate dye used as the organic dye of an optical recording medium for recording at a recording linear velocity of 35.0 m / s or more, wherein the azo compound is represented by the general formula (1) An azo metal chelate dye characterized by comprising a metal ion of Zn.

According to the present invention, there is provided an optical recording medium for high-density recording or high-speed recording, which has good recording characteristics at a wide recording linear velocity and has excellent “practical” light resistance.
According to the present invention, an optical recording medium suitable for high-speed recording is provided.
Furthermore, according to the present invention, there is provided a sputtering target for producing a reflective layer of an optical recording medium excellent in light resistance and recording characteristics.
In addition, according to the present invention, there is provided an azo metal chelate dye used for a recording layer of an optical recording medium suitable for high-speed recording.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment of the present invention) will be described in detail. The present invention is not limited to the following embodiments, and it goes without saying that various modifications can be made within the scope of the invention.

[I. Basic concept 1 of the present invention]
In the present invention, first, on a substrate having concentric or spiral grooves, at least a recording layer made of an organic dye and a reflective layer containing a metal, and the shortest mark length is less than 0.4 μm, or In an optical recording medium for recording at a recording linear velocity of 35.0 m / s or more, the track pitch of the guide groove on the substrate is 0.8 μm or less, the groove width is 0.4 μm or less, and the recording layer thickness in the groove is The organic dye single layer forming the recording layer has a dye retention of 70% or less in the Wool scale 5 (light resistance test) under the light irradiation conditions shown in ISO-105-B02. The differential value dR / dλ (% / nm) of the reflectance R with respect to the wavelength λ in the air of the reflective layer is 3 or less in a wavelength region of 300 nm to 500 nm. That the optical recording medium is provided (which hereinafter may be referred to as "first optical recording medium of the present invention").

  The present inventors have intensively studied to provide an optical recording medium for high-density recording or high-speed recording, which has good recording characteristics at a wide recording linear velocity.

  The “high density recording” in the present invention is premised on recording with a density of a shortest mark length of less than 0.4 μm. This is because the problem to be solved by the present invention is particularly prominent in an optical recording medium that is densified by shortening the recording mark and narrowing the track pitch. In “high density recording”, it is important to reduce the formation of excessive recording portions.

  Further, “high-speed recording” in the present invention means recording at a recording linear velocity of 35.0 m / s or more (for DVD as an example, the DVD is 1 × speed, that is, 10 × or more of the linear velocity of 3.5 m / s). Recording at the number of revolutions).

  When the recording of the first optical recording medium of the present invention corresponds to “high-speed recording”, the above-described “high-density recording”, that is, recording with a density of less than the shortest mark length of 0.4 μm is not necessarily required. Good. However, even in this case, it is desirable that the shortest mark length is usually less than 0.5 μm, preferably 0.44 μm or less, more preferably 0.4 μm or less.

  As a result of the study by the present inventors, it has been found that there are suitable dyes or combinations of dyes as dyes used in the recording layer (dye layer). That is, using a dye having a dye retention of 70% or less after the light resistance test of the recording layer single layer, or mixing “a dye having poor light resistance” and “a dye having good light resistance” The recording layer single layer is mixed so that the dye retention before and after the light resistance test is 70% or less.

  However, it has been found that such a dye or a combination of dyes suitable for high-density recording at a high density causes a new problem of causing deterioration of the light resistance of the disk.

  The present inventors have further investigated this new problem. As a result, the differential value dR / dλ (% / nm) of the reflectance R with respect to the wavelength λ in the air of the reflective layer is set to 3 or less in the wavelength region of 300 nm or more and 500 nm or less. It was found that various problems could be solved. That is, “practical” light resistance can be improved. Incidentally, the “practical” light resistance in the present invention means that even though the light resistance of a single recording layer is not sufficiently good, when a disk structure is used, Wool scale class 5 light is irradiated. This also means an index as to whether jitter or error in the recorded portion of the disk falls within a preferable range. Therefore, it is distinguished from the index of the dye retention rate of the recording layer itself.

  That is, in the basic concept 1 of the present invention, on a substrate having concentric or spiral grooves, at least a recording layer made of an organic dye and a reflective layer containing a metal are provided, and the shortest mark length is less than 0.4 μm. Alternatively, in an optical recording medium that performs recording at a recording linear velocity of 35.0 m / s or more, the groove width on the substrate is 0.4 μm or less, and the recording layer thickness in the groove is 70 nm or less. The dye retention of the organic dye single layer forming the layer is 70% or less in the Wool scale 5 (light resistance test) under the light irradiation conditions shown in ISO-105-B02, and the wavelength of the reflective layer in the air The differential value dR / dλ (% / nm) of the reflectance R with respect to λ is 3 or less in a wavelength region of 300 nm to 500 nm.

  Here, the “dye retention” is the ratio of the absorbance before and after the light resistance test at the maximum absorption wavelength of the coating film of the organic dye single layer forming the recording layer in the wavelength range of 300 to 800 nm, that is, {(after the test Absorbance) / (Absorbance before test)} × 100 (%).

  By setting the substrate groove width to 0.4 μm or less, the track pitch can be increased to 0.8 μm or less, and a sufficient push-pull signal amplitude is ensured. When recording is performed by rotating the disk at high speed, tracking can be stably performed on the groove. The groove width is usually 0.1 μm or more, more preferably 0.2 μm or more, in order to ensure a sufficient push-pull signal amplitude. The track pitch is usually 0.2 μm or more, preferably 0.4 μm or more.

  Further, when the recording layer thickness in the groove is 70 nm or less, the formation of an excessive recording portion is suppressed, and good “high density recording” and “high speed recording” with little crosstalk become possible. Incidentally, the film thickness of the recording layer in the groove is usually 5 nm or more, more preferably 10 nm or more, and further preferably 20 nm or more.

  In the high-speed recording, usually, the shortest mark must be formed with a pulse whose irradiation time of the laser beam is extremely shortened. In other words, in such high-speed recording, the recording laser light irradiation time for recording the shortest mark length (3T mark in the example of the present embodiment) is less than 8 ns. For this reason, the fact that recording is possible in such high-speed recording means that recording can be performed with the bottom jitter (minimum value of jitter value) not exceeding 9% under the recording conditions where the laser irradiation time during the shortest mark length recording is less than 8 ns. Or, it means that the error rate is good enough that there is no problem in reproduction with a commercially available reproduction apparatus. This “recording the shortest mark length with a pulse shortened so that the irradiation time is less than 8 ns” means, for example, that the rise time of the semiconductor laser in the wavelength region of DVD is around 4 ns. You can see how severe the recording conditions are.

  The irradiation pulse width of the laser for recording the 3T mark length used in each example and comparative example described later is 7.times. Recording (35 m / s) and 16.times. Recording (56.0 m / s), respectively. 9 ns and 6.5 ns.

  Further, in the present invention, “good recording is possible at a wide recording linear velocity” means 3.5 m / s to about 70 m / s (when DVD is taken as an example, 1 × speed recording (3.5 m / s) of DVD) It can be recorded with a bottom jitter not exceeding 9% over approximately 20 times speed recording (70 m / s), or it has a good error rate so that there is no problem in reproduction with a commercially available reproducing apparatus. means. For example, in the DVD-R, the jitter value is a good index for evaluating the recording quality. For example, in the currently known range, it is usually 8.0% or less, more preferably 7% or less, even more preferably 3.5 m / s to 28 m / s (for example, 1 × speed recording to 8 × speed recording for DVD). Is generally determined to be particularly good when recording capable of obtaining a bottom jitter of 6% or less is possible.

  As a result of intensive studies, the present inventors have found that the problem of the recording margin among the above problems can be solved by reducing the recording speed dependency of the organic dye medium and further increasing the response to the shortening pulse. Thought.

More specifically, as a result of investigations by the present inventors, it is possible to ensure good recording characteristics at a wide recording speed by including a “dye having poor light resistance” in the recording layer, that is, poor light resistance. It was found that there is a correlation between the high-speed recording characteristics and the recording characteristics in a wide recording speed range. This effect is considered to be due to the fact that the light energy incident as “recording light inferior dye” as recording light can be effectively utilized by decomposition of the dye (optical mode). That is, in such a dye, it is considered that the optical mode is involved in the bond-cleavage reaction of the dye, light energy is used efficiently, and a recording mark with a sharp edge is formed, thereby improving the recording characteristics. . Or it is generally known that the optical mode recording has a high reaction speed, and it is possible in principle to terminate the reaction on the order of fsec to psec. If the reaction is completed in this time order, it is highly possible that interference between adjacent marks does not occur in view of the rotational speed of the disc.
On the other hand, the use of incident light as recording light for reaction (including decomposition and melting) of a dye as heat energy is generally called heat mode recording.

  This heat mode recording has a reaction speed limit due to the heat conduction speed. For example, in DVD-R, it is considered that the reaction is usually completed in the order of ns. When the reaction is completed in this order, the order of the disk rotation speed and the reaction speed is approximately the same, so that the adjacent mark may be affected by heat. When the adjacent mark is affected by heat, so-called thermal interference occurs between the marks, and the possibility of deteriorating jitter increases. However, since this heat mode is not related to light resistance, it is considered that “colorant with good light resistance” is mainly decomposed and recorded in this mode.

  Furthermore, by mixing “dye with good light resistance” with such “dye with poor light resistance”, it is possible to skillfully balance the physical change and the optical change in the recording area, and at a higher speed. It is considered that the recording characteristics can be improved. This is because, for example, a sufficient degree of recording modulation cannot be obtained with a “dye having poor light resistance”, which is less likely to cause heat mode recording. This is because it is thought that it can be supplemented with “a simple pigment”.

The “dye having poor light resistance” is considered to correspond to a dye compound having a low probability of causing a so-called “non-radiative transition” from a state excited by light. For example, (1) not only has a strong absorption band that is considered to involve a π-π ^* transition or a charge transfer transition in the vicinity of the recording / reproducing wavelength, but also has a structure with good flatness that does not have many spatial configurations. Pigments. Examples of this include a large number of organic dyes that are likely to undergo a π-π ^* transition and that often emit fluorescence. For example, specific cyanine dyes listed below are suitable for optical disks. Can be mentioned. In addition, although metal chelate dyes have been said to have good light resistance, among the metal chelate dyes, (2) metal chelate dyes whose central metal tends to be detached from coordination bonds by light are “light resistance”. It is considered that the colorant is inferior in property. (2) is the case where the central metal ion does not have an empty d orbital in the outermost d orbital that should originally be involved in coordination bonds, or there are few empty d orbitals (in the present invention). in, for example, Zn ^2+, since the electron configuration 3d ¹⁰ 4s ² of Zn (the ionization) two electrons can take, take 3d ¹⁰ electron configuration), metal -. covalent bonding ligand is reduced. Then, electrons are excited in the ligand by photoexcitation, and the central metal tends to be easily detached. As a result, the absorption band may shift to the short wavelength side and the optical constant may change. In addition, when the ligand free from the coordinate bond is inferior in light resistance, the ligand tends to react in the optical mode. This is considered to have the tendency of optical mode recording in the same manner as this type of “dye having poor light resistance”. Accordingly, as the central metal of the metal chelate dye having such an inferior light resistance, a metal having few empty d orbitals or no empty d orbital due to ionization is applicable. In addition, the ligand has a molecular orbital in which MLCT (metal-to-ligand charge transfer) is likely to occur (for example, the ligand has an empty anti-bonding orbital). Is also preferable. It should be noted that the magnitude of the contribution of the optical mode in the decomposition of these dyes can also be estimated by whether or not fluorescence is emitted. That is, it is considered that the fluorescent dye tends to have a large contribution of the optical mode in the decomposition. In addition, the property that the covalent bond property (strong coordination bond) between the ligand and the central metal ion is small is that the central metal ion has a d ⁹ or d ¹⁰ electron configuration, but the structure selection energy is near zero. It can also be considered to be related to this. The “structure selection energy” was in accordance with KF Puncell et al., Inorganic Chemistry, 1977, p.550.

  On the other hand, in the “dye having good light resistance”, for example, a dye compound having a high probability of occurrence of non-radiative transition can be mentioned. In such a dye compound, the absorbed light is mainly converted into thermal energy. Examples of such a metal chelate dye include an azo metal chelate dye which is a first transition element (3d transition element) which has an empty d orbital in the d orbital of the central metal ion or can form an empty d orbital. It is done. These have a chelate structure that is stable even in an excited state because a hybrid orbital is formed through the overlap of an empty d orbital of a metal ion and an orbital of a ligand, and the metal-ligand covalent bond is large. Is likely to be formed. That is, it is considered that the ligand does not become free from the coordinate bond even by photoexcitation.

  Examples of the “dye having poor light resistance” include an azo complex having Zn as a central metal, or a cyanine dye containing no quencher. In addition, depending on the type of ligand, an azo complex having Cu or Ni as a central metal may be used, but an azo complex having Zn as a central metal is particularly preferable. Examples of such dyes include metal chelate dyes that coordinate two azo compounds described below with respect to one Zn element.

  The “dye having poor light resistance” in the present invention is preferably a single composition of the dye and having a dye retention of 70% or less as defined in the present invention. The smaller the dye retention within this range, the more “dye having poor light resistance”. Therefore, for the reasons described above, the characteristics in high-speed recording or high-density recording may be excellent.

  Further, the “dye having good light resistance” in the present invention is preferably a single composition of the dye and having a dye retention rate of more than 70% as defined in the present invention. More preferably, it is 80% or more, More preferably, it is 85% or more.

  Examples of the azo complex preferable as the “dye having poor light resistance” include an azo metal chelate dye (hereinafter referred to as “dye (1)” which comprises an azo compound represented by the following general formula (1) and a metal ion of Zn. ) ”)).

In general formula (1), R ¹ represents a hydrogen atom or an ester group represented by CO ₂ R ³ (wherein R ³ represents a linear or branched alkyl group or a cycloalkyl group). .
R ² represents a linear or branched alkyl group.
At least one of X ¹ and X ² represents an NHSO ₂ Y group (where Y represents a linear or branched alkyl group substituted with at least two fluorine atoms), and the rest Represents a hydrogen atom.
R ⁴ and R ⁵ each independently represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkoxy group.
R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.
Note that H ⁺ is eliminated from the NHSO ₂ Y group to become an NSO ₂ Y ⁻ (negative) group, and the azo compound represented by the general formula (1) forms a coordinate bond with the metal ion.

R ³ is preferably a linear or branched alkyl group having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, and a sec-butyl group. A cycloalkyl group having 3 to 8 carbon atoms, such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group; Particularly preferred is a straight chain alkyl group having 1 or 2 carbon atoms such as a methyl group or an ethyl group because of low steric hindrance; a cycloalkyl group having 3 to 6 carbon atoms such as a cyclopentyl group or a cyclohexyl group. .

R ² is preferably a linear alkyl group having 1 to 8 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group; isopropyl group, sec-butyl group, isobutyl group, t- Examples thereof include branched alkyl groups having 3 to 8 carbon atoms such as a butyl group, 2-ethylhexyl group, cyclopropyl group, cyclohexylmethyl group and the like.

  Y represents a linear or branched alkyl group substituted with at least two fluorine atoms. The linear or branched alkyl group is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and more preferably a linear alkyl group having 1 to 3 carbon atoms.

R ⁴ and R ⁵ are preferably a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, and an alkoxy group having 1 to 8 carbon atoms. R ⁴ and R ⁵ are more preferably a hydrogen atom, an alkyl group having 1 or 2 carbon atoms, or an alkoxy group having 1 or 2 carbon atoms. The alkyl group and alkoxy group are preferably unsubstituted. R ⁴ and R ⁵ are particularly preferably a hydrogen atom, a methyl group, an ethyl group, or a methoxy group.

R ⁶ , R ⁷ , R ⁸ , and R ⁹ each independently represent a hydrogen atom or an alkyl group having 1 or 2 carbon atoms. It is preferable to use a hydrogen atom or an alkyl group having 1 or 2 carbon atoms because the absorbance and refractive index can be easily adjusted to predetermined values. In the alkyl group having 1 or 2 carbon atoms, the hydrogen atom bonded to the carbon atom may be substituted with another substituent (for example, a halogen atom), but is preferably an unsubstituted alkyl group. Examples of the alkyl group having 1 or 2 carbon atoms include a methyl group and an ethyl group. From the viewpoint of ease of synthesis and steric structure, hydrogen atoms are most preferred as R ⁶ , R ⁷ , R ⁸ , and R ⁹ .

  Specific examples of the azo compound (ligand) of the general formula (1) constituting the dye (1) include azo compounds having the structure shown below.

  On the other hand, examples of cyanine dyes preferable as the “dye having poor light resistance” include cyanine dyes represented by the following general formula (2) (hereinafter, appropriately referred to as “dye (2)”).

In general formula (2), ring A and ring B each independently represent a benzene ring or naphthalene ring which may have a substituent.
R ¹⁰ and R ¹¹ each independently represents an alkyl group having 1 to 5 carbon atoms which may have a substituent.
R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ each independently represents an alkyl group having 1 to 5 carbon atoms which may have a substituent.
R ¹⁶ represents a hydrogen atom, a halogen atom, a cyano group or an alkyl group having 1 to 5 carbon atoms which may have a substituent.
Q ⁻ represents a counter anion. Examples of the counter anion include various anions such as BF ₄ ⁻ , PF ₆ ⁻ , and metal complexes.

R ¹⁰ and R ¹¹ are preferably straight chain or branched having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, sec-butyl, etc. It is an alkyl group. Particularly preferred is a linear alkyl group having 1 or 2 carbon atoms such as a methyl group or an ethyl group because of its small steric hindrance. The hydrogen atom of the alkyl chain may be substituted with fluorine or a substituent described later.

R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ are preferably straight chain alkyl groups having 1 to 5 carbon atoms such as methyl, ethyl, propyl, butyl, and pentyl groups; isopropyl groups, sec-butyl A branched alkyl group having 3 to 5 carbon atoms, such as a group, an isobutyl group, and a t-butyl group. The hydrogen atom of the alkyl chain may be substituted with fluorine or a substituent described later.

R ¹⁶ is preferably a hydrogen atom; a halogen atom such as Cl or Br; a cyano group; a carbon such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, or a sec-butyl group. A linear or branched alkyl group having a number of 1 or more and 5 or less. Moreover, when using an alkyl group, the hydrogen atom of the alkyl chain may be substituted by the substituent mentioned later.

In addition, as a preferable substituent of the benzene ring or naphthalene ring of ring A and ring B,
A linear or branched alkyl group having 1 to 6 carbon atoms,
An aromatic or heteroaryl group having 1 to 12 carbon atoms (a carbocyclic or heterocyclic aryl group having 1 to 12 carbon atoms),
An alkoxy group having 1 to 6 carbon atoms,
An ester group having 1 to 6 carbon atoms,
A dialkylamino group having 1 to 6 carbon atoms,
Nitro group,
A thioalkyl group having 1 to 6 carbon atoms,
An alkylsulfonyl group having 1 to 6 carbon atoms,
A trialkylsilyl group having 1 to 6 carbon atoms,
Sulfonic acid groups,
Phosphate group,
Carboxylic acid groups,
A cyano group,
A halogen atom etc. are mentioned.

Further, as preferred substituents for the alkyl group of R ¹⁰ to R ¹⁶ ,
An aromatic or heteroaryl group having 1 to 12 carbon atoms (a carbocyclic or heterocyclic aryl group having 1 to 12 carbon atoms),
An alkoxy group having 1 to 6 carbon atoms,
An ester group having 1 to 6 carbon atoms,
A dialkylamino group having 1 to 6 carbon atoms,
Nitro group,
A thioalkyl group having 1 to 6 carbon atoms,
An alkylsulfonyl group having 1 to 6 carbon atoms,
A trialkylsilyl group having 1 to 6 carbon atoms,
Sulfonic acid groups,
Phosphate group,
Carboxylic acid groups,
A cyano group,
A halogen atom,
Etc.

The substituent is preferably a carbocyclic or heterocyclic aryl group having 1 to 12 carbon atoms. More preferred is a carbocyclic aryl group having 6 to 12 carbon atoms. From the viewpoint of recording characteristics, a benzene ring is more preferable.
Most preferable from the viewpoint of recording characteristics, it is preferable to substitute hydrogen of the alkyl chain with a benzene ring in a part of the alkyl groups used for R ^{12 to} R ¹⁶ . Specifically, examples of the method using a benzene ring as a substituent include the following combinations (α) to (γ). Considering steric hindrance and the like, it is preferable to use a combination of (α) and (β).

(Α) When R ¹² and R ¹³ are alkyl groups, hydrogen in one or both alkyl chains of R ¹² and R ¹³ is substituted with a benzene ring.
(Β) When R ¹⁴ and R ¹⁵ are alkyl groups, hydrogen in one or both alkyl chains of R ¹⁴ and R ¹⁵ is substituted with a benzene ring.
(Γ) When R ¹⁶ is an alkyl group, the hydrogen of the alkyl chain of R ¹⁶ is substituted with a benzene ring.

  Specific examples of the dye (2) include compounds having the following structures.

  Note that any one of the above “dyes having poor light resistance” in the recording layer may be used alone, or two or more thereof may be used in any combination. Among these, it is preferable to use at least one of the above-described dye (1) and / or dye (2). In this case, only one or two or more of the above-described dye (1) may be used, or only one or two or more of the above-described dye (2) may be used. 1) Any one kind or two kinds or more and any one kind or two kinds or more of the above-mentioned dye (2) may be used in appropriate combination. Of course, in addition to the above-mentioned dye (1) and / or dye (2), another "dye having poor light resistance" may be used in combination.

  On the other hand, the “dye having good light resistance” that is preferably combined with the above-mentioned dye (1) or dye (2) is specifically a transition other than Zn in which two azo compounds are coordinated. Examples thereof include metal-containing azo complexes having a metal (for example, V, Cr, Mn, Fe, Co, Ni, Cu) as a central metal. The central metal ion that forms a coordination bond is preferably a divalent ion.

  Preferably, at least one azo compound selected from the group consisting of compounds represented by the following general formulas (3), (4), (5), and (6), a metal ion of a 3d transition element excluding Zn, Azo metal chelate dyes (hereinafter referred to as azo metal chelate dyes having azo compounds corresponding to the respective general formulas are referred to as “dye (3)”, “dye (4)”, “dye (5)”, “dye (6 ) ”))).

In general formulas (3) and (5), R ²⁰ has a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms which may have a substituent, or a substituent. An ester group having a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms which may be present.
In the general formulas (4) and (6), R ¹⁷ represents an alkyl group having 1 to 6 carbon atoms which may have a substituent.
R ²¹ to R ^{27 in} the general formulas (3) and (4) and R ¹⁸ and R ¹⁹ in the general formulas (5) and (6) each independently have a hydrogen atom or a substituent. It represents a straight, branched or cyclic alkyl group having 1 to 6 carbon atoms. R ¹⁸ and R ¹⁹ may combine with each other to form a ring.
In general formulas (3), (4), (5), and (6), at least one of X ¹ and X ² is an NHSO ₂ Y group (where Y is substituted with at least two fluorine atoms) Represents a straight-chain or branched alkyl group, and the remainder represents a hydrogen atom.
The azo compound represented by the general formulas (3), (4), (5) and (6) is obtained by removing H ⁺ from the NHSO ₂ Y group to form an NSO ₂ Y ⁻ (negative) group. Forms a coordination bond with a metal ion. )

R ¹⁷ is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group and sec-butyl group. It is.

R ¹⁸ and R ¹⁹ are preferably straight chain or branched chains having 1 to 6 carbon atoms, such as methyl group, ethyl group, isopropyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, and hexyl group. An alkyl group is mentioned. R ¹⁸ and R ¹⁹ may be bonded to each other to form a cyclic alkyl group such as a cyclic cyclohexyl group.

R ²⁰ is preferably a hydrogen atom; a straight chain or branched alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, etc .; methyl An ester group having a linear or cyclic alkyl group having 1 to 6 carbon atoms, such as an ester group, an ethyl ester group, a propyl ester group, an isopropyl ester group, a butyl ester group, an isobutyl ester group, a pentyl ester group, or a cyclohexyl ester group. is there. Considering comprehensively the ease of industrial synthesis and recording characteristics, R ²⁰ is particularly preferably a hydrogen atom.

R ²¹ to R ²⁷ are preferably hydrogen atoms; straight chain having 1 to 6 carbon atoms such as methyl group, ethyl group, isopropyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, hexyl group, etc. A branched alkyl group.
X ¹ , X ² , and Y may be the same as those of the azo compound represented by the general formula (1).

In addition, as a substituent which may be substituted by the alkyl group of R ^{17 to} R ^{27 in} the general formulas (3), (4), (5) and (6),
An aromatic or heteroaryl group having 1 to 12 carbon atoms (a carbocyclic or heterocyclic aryl group having 1 to 12 carbon atoms),
An alkoxy group having 1 to 6 carbon atoms,
An ester group having 1 to 6 carbon atoms,
A dialkylamino group having 1 to 6 carbon atoms,
Nitro group,
A thioalkyl group having 1 to 6 carbon atoms,
An alkylsulfonyl group having 1 to 6 carbon atoms,
A trialkylsilyl group having 1 to 6 carbon atoms,
A cyano group,
A halogen atom etc. are mentioned.

  Specific examples of the azo compounds (ligands) of the general formulas (3), (4), (5), and (6) that constitute such azo metal chelate dyes include compounds having the following structures.

  In addition, any one of the above “dyes having good light resistance” may be used alone, or two or more may be used in any combination. Among these, it is preferable to use at least one of the above-mentioned dye (3), dye (4), dye (5) and / or dye (6). In this case, only one or two or more of the dyes (3), (4), (5) and (6) described above may be used. , (4), (5) and (6), a plurality of them may be used alone or in combination of two or more. Of course, in addition to the above-mentioned dye (3), dye (4), dye (5) and / or dye (6), another “light-resistant dye” may be used in combination.

  Note that, as described above, the light resistance index of a dye whose effect is clear on the recording characteristics is as described below. That is, when the “dye having poor light resistance” and “dye having good light resistance” constituting the recording layer are used in combination, the mixing ratio of these dyes is controlled as follows. That is, such a ratio that the dye retention rate of the recording layer single layer (the organic dye single layer forming the recording layer) is 70% or less in the light irradiation conditions shown in ISO-105-B02, that is, in Wool scale 5 grade. Mix with.

  If the light resistance is better than this value, the sufficient optical mode is not exhibited in the decomposition, so the contribution of the heat mode (pyrolysis reaction) in the decomposition of the dye is large, and therefore the recording characteristics are sufficiently improved. It may not be possible.

  Incidentally, the dye retention rate of the recording layer single layer can be evaluated by the method described in the following example even in a disc slice having a substrate and a dye that are peeled off at the bonded portion of the bonded disc. Is possible.

  As described above, the combination of the above dyes suitable for high-speed recording, on the other hand, may deteriorate the light resistance of the disc.

  As a solution for improving the light resistance of such “dye having poor light resistance”, generally, a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithiol) is used as a singlet oxygen quencher. -Α-diketone, etc.) and a recording sensitivity improver such as a metal compound may be contained. Here, the metal compound means a compound in which a metal such as a transition metal is contained in the compound in the form of atoms, ions, clusters, etc., for example, ethylenediamine complex, azomethine complex, phenylhydroxyamine complex, phenanthroline complex, Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex and porphyrin complex can be mentioned. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.

  However, by adding such a quencher, the sharpness of the edge of the recording mark may be lost, or the manufacturing process may be complicated.

  The present inventors have studied to improve “practical” light resistance without actively using such additives. As a result, the light resistance of the recording layer is improved by using a reflective layer in which the differential value (dR / dλ) of the reflectance R with respect to the wavelength in the air at a wavelength of 300 nm ≦ λ ≦ 500 nm is (dR / dλ) ≦ 3. I got the knowledge that it can be improved.

  The reason is considered as follows. That is, based on a metal free electron model, when a metal is irradiated with a specific light frequency, a phenomenon occurs in which electrons in the metal collectively resonate. When this resonance occurs, the refractive index (n), and thus the reflectance, changes abruptly at a specific frequency. When this electron collective resonance occurs, chemical reaction (including catalytic reaction) due to photoexcitation at the interface with the dye is likely to proceed, and the dye is likely to deteriorate. Therefore, it is not desirable from the viewpoint of light resistance that the reflectance fluctuates sharply at a specific light frequency. From this result, it is necessary to select a reflective layer in which (dR / dλ) ≦ 3 in the above wavelength range in which not only the absolute value of the reflectance but also the relative value of the reflectance does not change abruptly. . Examples of the material that satisfies such a condition include materials whose interband transition is not in the range of 300 nm to 500 nm. More preferably, (dR / dλ) ≦ 2, and further preferably (dR / dλ) ≦ 1. The reason why the prescribed wavelength range of dR / dλ is set to 300 nm to 500 nm will be described below.

  Examples of the reflective layer satisfying such conditions include at least one element selected from Cu, Au and Al (hereinafter sometimes referred to as “specific element”), and these specific elements in the reflective layer. And a reflective layer having a total ratio of 50 at% or more. When this ratio is less than 50 at%, there is a possibility that (dR / dλ) ≦ 3 in the above wavelength range may not be satisfied, and therefore sufficient light resistance may not be obtained. In addition, as an element other than the specific element in the reflective layer, Ag, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co , Rh, Ir, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, Ti, Zn, Zr, and at least one element selected from the group consisting of rare earth metals. Among these, the ratio of these elements in the reflective layer is preferably 100 at% together with the ratio of the specific element. It is preferable to adjust the types of elements other than the specific element and the amount of mixing thereof so as to satisfy the above (dR / dλ) ≦ 3.

  Further, a reflective layer having a reflectance in the air at 300 nm to 500 nm of 20% to 70% is also preferable. This requirement does not simply mean that a reflection layer having a high reflection layer at the recording / reproducing light wavelength is used as in the prior art. That is, by using a reflective layer in which the reflective layer in the air in the wavelength region of 300 nm to 500 nm is 20% to 70% while having a high reflectance of 80% or more at the recording / reproducing light wavelength, This means that the “practical” light resistance is further improved.

  The reason why the reflection layer satisfying such requirements improves the light resistance of the recording layer is considered as follows. In the first place, the light resistance test (ISO-105-B02) of an optical disk that is generally performed is a test method that assumes exposure to sunlight. It is known that the intensity of sunlight reaches saturation at 300 nm to 500 nm, particularly 400 nm to 500 nm, and since the energy of the light particles is proportional to the frequency of light, the energy of the light particles is also Higher than the energy of long wavelength light particles. Since light particles having high energy have a higher probability of exceeding the threshold for breaking the bond of the dye, it is desirable that the light of this wavelength is not excessively absorbed by the dye in order to improve the light resistance of the disk. That is, it is preferable to use a reflective layer having a low reflectance in this wavelength range. Therefore, if a reflection layer having a low reflectance in the above wavelength range is used, the amount of multiple reflections between the dye recording layer and the reflection layer is reduced, so that deterioration of the recording layer having a dye having poor light resistance is suppressed. it is conceivable that. In this way, “practical” light resistance can be further improved.

  3A is a graph showing the wavelength distribution of the refractive index (n) of the main metal material, and FIG. 3B is a graph showing the wavelength distribution of the extinction coefficient (k) of the main metal material. FIG. 3C is a graph showing the wavelength distribution of reflectance in air calculated for a reflective layer (film thickness 120 nm) formed using main metal materials. Note that the thickness of the reflective layer of 120 nm is a thickness at which the reflectance is sufficiently saturated. In this specification, the reflectance “in the air” means the ratio of the return light intensity to the incident light intensity when incident light is directly irradiated onto the film surface of the reflective layer through the air.

  FIG. 3A shows that the refractive index (n) of Au, Cu, and Al is larger in the region of 350 nm to 500 nm than Ag that is generally used as a reflective layer. In particular, the refractive index (n) of Au and Cu is stably around 1 in this wavelength region. Moreover, from FIG.3 (c), it turns out that the reflectance of Au and Cu is 30%-70%, and is quite small compared with Ag.

In addition, the value published in the following literature was used as the value of the refractive index (n) and extinction coefficient (k) of the metal material in FIG. 3 (a), (b).
Springer-Verlag Heidelberg, Landolt Bornstein-Group III Condensed matter, Volume 15, subvolume B, 1985, p.222-236 (Ag-Ca), p.237-248 (Cd-Eu), p.280-291 (Ni -Pb) (ISSN: 1616-9549)

  Examples of the reflective layer satisfying such conditions include at least one element selected from Cu, Au and Al (hereinafter sometimes referred to as “specific element”), and these specific elements in the reflective layer. And a reflective layer having a total ratio of 50 at% or more. When this ratio is less than 50 at%, there is a possibility that the preferable reflectance range is not satisfied. In addition, as an element other than the specific element in the reflective layer, Ag, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co , Rh, Ir, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, Ti, Zn, Zr, and at least one element selected from the group consisting of rare earth metals. Among these, the ratio of these elements in the reflective layer is preferably 100 at% together with the ratio of the specific element.

  Further, as a result of investigations, for example, in the case of silver or silver alloy that has been put to practical use in the past, the change before and after recording of the recording layer and the reflective layer is different from that at the time of low speed recording, so 35.0 m / s. It was found that the above high-speed recording may be difficult. This is because, particularly in recording exceeding 35.0 m / s, the pulse width of the laser beam irradiated for recording is shortened, so that optical properties such as plastic deformation, thermal conductivity, absorption and refraction of the reflective layer are reduced. This is because it is considered that the difference in the constant tends to reflect the recording characteristics more remarkably. Accordingly, the selection of the reflective layer for such high-speed recording needs more care than in the conventional low-speed recording. However, the present situation is that optical recording media having a reflective layer of silver or a silver alloy are widely put into practical use due to the fact that they have a record of recording characteristics in low-speed recording and are relatively inexpensive.

  As a result of intensive studies, the present inventors have found that recording characteristics at a high recording linear velocity (especially 35.0 m / s or more), and thus a wide recording linear velocity from low to high, differ depending on the reflective layer. It has been found that the use of a reflective layer mainly composed of copper, gold, or aluminum makes it favorable.

  There are various effects of recording at high speed on recording characteristics. In particular, when the recording layer is made of an organic dye, the recording speed dependency such as recording sensitivity and jitter becomes very remarkable as compared with a recording film medium made of metal or semiconductor. Therefore, as a condition required for a reflection layer of a medium having an organic dye as a recording layer, a reflection layer having a high reflectance of a certain value or higher and higher heat conduction is desired. The metal reflection film having a high reflectance is a reflection layer in which the real part n of the refractive index at the recording wavelength is a predetermined value or less and the imaginary part k is large. Specifically, the refractive index of the reflective layer for obtaining a practical reflectance is 0.0 <n <1.0 and k> 2.0.

  Moreover, it is preferable that heat conductivity is high. Examples of metals with high reflectivity include Ag (320 W / M · K), Cu (300 W / M · K), Au (230 W / M · K), Al (158 W / M · K), and the like. Can be mentioned.

  By using these metals or alloys thereof, there is a possibility that a medium with good high-speed recording can be obtained. Even when the recording wavelength is shortened in the future, by optimizing the combination of the metals, there is a high possibility of obtaining good recording characteristics that can achieve both high reflectivity and thermal conductivity.

  In a medium using an organic dye for the recording layer, when a long mark (6T mark or more) is recorded, the bottom line of the waveform is not horizontal but tends to be inclined (hereinafter sometimes referred to as waveform distortion). There is. The waveform distortion may cause the bottom jitter to deteriorate. Although bottom jitter is good at low speed recording, bottom jitter at high speed recording is bad or vice versa. In the present inventors, such waveform distortion is related to the temperature distribution in the film thickness direction of the recording layer, which optimizes the combination of the film thickness of the recording layer and the reflective layer, the optical constant, and the thermal conductivity of the reflective layer. As a result, it is considered that good recording can be performed at a wide recording linear velocity of 3.5 m / s to 35.0 m / s and eventually 3.5 m / s to approximately 70 m / s. Yes.

  That is, for the reasons described above, the recording mark waveform may be improved in a wide recording linear velocity range by having a reflective layer that can use the recording laser light without waste in a thermal optical manner.

  In addition, the above-mentioned “reflective layer is mainly composed of copper, gold, and aluminum” means that the reflective layer is made of copper, gold, or aluminum alone, or any two or more of copper, gold, and aluminum. It means that the combination includes 50 atomic% or more in total. In order to optimize weather resistance, film structure, and optical properties, it is preferable to contain elements other than copper and gold. Examples of such elements include Al, Ag, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, and Cd. , Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, Ti, Zn, Zr and a group consisting of rare earth metals. The content of these elements is preferably 0.1 to 40 atomic%. As a material containing such an element, for example, CuAg, CuZrAg, and the like are preferable.

  In addition, as described in Examples, copper, gold, and aluminum have a reflectance dR / dλ (% / m) of 3 or less with respect to the wavelength in the air at a wavelength of 300 nm to 500 nm. On the other hand, the differential value of the reflectivity of pure silver at 300 nm to 500 nm exceeds 5 at the maximum, which is not preferable from practical light resistance. For example, even in a metal reflective film containing silver, the composition ratio of silver The dR / dλ value of the present invention can be set to 3 or less.

  As described above, the reflective layer having a reflectance differential value dR / dλ (% / nm) of 3 or less with respect to the wavelength in the air at a wavelength of 300 nm to 500 nm, and the recording layer containing a dye having poor light resistance; For the first time, it is possible to obtain an optical recording medium having “practical” light resistance that can withstand practical use while having extremely high recording characteristics of 35 m / s or more.

  As described above, in order to form the reflective layer so as to satisfy (dR / dλ) ≦ 3 in the specific wavelength range defined in the present invention, by selecting a sputtering target, the reflective layer is made of Cu, Au and While containing at least one element selected from Al, the total ratio of the elements is 50 atomic% or more (in some cases, “atomic%” may be described as “at%”) in the reflective layer. It is preferable to do so. Among Cu, Au, and Al, Cu and Al are preferable at least from the viewpoint of reflectivity.

  According to the study by the inventors, the island-like structure of the sputtered film grows during the high-temperature and high-humidity test and the temperature rising process during recording, and the smoothness of the film may be lowered. It has been found that the jitter of the portion may be lowered.

  From the above, the reflective layer is preferably a thin film containing at least a Cu alloy represented by the following composition (A).

[Composition (A)]
50at% ≦ Cu ≦ 97at%
3at% ≦ Ag ≦ 50at%
0.05at% ≦ X ≦ 10at%
(Here, X represents at least one element selected from the group consisting of Zn, Al, Pd, In, Sn, Cr, and Ni. In the following description, when X is referred to as “third element species”) (However, the total amount of Cu, Ag, and X is 100 at% or less.)

  Specifically, in the composition (A), the Cu content is usually 50 at% or more, preferably 65 at% or more, more preferably 80 at% or more, and usually 97 at% or less, preferably 95 at% or less, more preferably. Is in the range of 90 at% or less.

  In the composition (A), the Ag content is usually 3 at% or more, preferably 5 at% or more, and usually 50 at% or less, preferably 30 at% or less.

  In order to form the reflective layer so as to satisfy (dR / dλ) ≦ 3 in the specific wavelength range specified in the present invention, the Ag content is preferably 50 at% or less. In addition, as supported by the examples described later, the organic dye layer that can withstand high-speed recording as described in the present invention is used as a recording layer, and the effect of improving sufficient light resistance by combining with a reflective layer is further improved. In order to ensure, it is preferable to make Ag content into 30 at% or less.

  In the composition (A), the X content is usually 0.05 at% or more, preferably 0.1 at% or more, and usually 10 at% or less, preferably 5 at% or less. In addition, when 2 or more types of metal elements are selected as X, it is preferable that those sum totals satisfy | fill the said range.

  The content of the third element species X is preferably 0.05 at% or more. In order to make it easy to obtain a sufficient effect stably, it is more preferably 0.1 at% or more. In particular, since Zn has a low melting point, the amount may not be sputtered when the target is sputtered. Therefore, a more stable composition is preferably 0.1 at% or more.

  Further, the content of the third element species X is preferably 10 at% or less. If it is 10 at% or less, it is easy to ensure a high reflectance. In order to easily ensure a sufficiently high reflectance, the content of the third element species X is more preferably 5 at% or less.

  It is considered that the third element species X has little influence on (dR / dλ). That is, the third element species X is preferable for ensuring the fine adjustment of the reflectance and the storage stability of the reflective layer, rather than being preferable for the light resistance improvement effect of the present invention.

Of the third element species X described above, Zn, Al, Pd, In, and Sn are more preferable. Among these, Zn, Al, and Pd are preferable because sufficient reflectance can be easily secured. In particular, Zn has been studied by the present inventors, and it has been found that a higher reflectance may be obtained even if the addition amount is small. In and Sn can also be expected to have the above-mentioned effects, similar to Zn, Al, and Pd. In particular, Zn, In, and Sn form an O ₂ component that attacks the Cu alloy and ZnO, In ₂ O ₃ , and SnO ₂ that are conductive oxides. These conductive oxides ZnO, In ₂ O ₃ and SnO ₂ are n-type semiconductors and generate a contact potential difference with Cu. As a result, oxygen ions (O ²⁻ ) are more likely to be attracted to the Zn, In, Sn side than Cu, and it is considered that the oxidation of Cu is delayed.

  When a low melting point / low boiling point element is used as the third element type X, a thin film (reflective layer) containing at least a Cu alloy having high reflectivity and excellent storage stability is formed (manufacturing). ), It is preferable to use the following sputtering target.

  For example, when Zn (melting point 419.6 ° C., boiling point 907 ° C.) is selected as the third element species X, Zn is used in a sputtering target that is about 0.01 to 2.5 at% higher than the above-described composition (A). It is preferable to make it contain in. This is because an element having a low melting point and a low boiling point easily volatilizes. Although there is a method of suppressing volatilization by making the distance between the target and the substrate during sputtering closer than other places, in order to obtain a predetermined reflective layer more stably and without waste, the sputtering target must be It is particularly preferable that the composition (B) is satisfied. As can be seen from the composition (B), when the composition of the reflective layer and the composition of the target are the same or close to each other, it becomes easy to produce a reflective layer having the composition (A).

[Composition (B)]
50at% ≦ Cu ≦ 97at%
3at% ≦ Ag ≦ 50at%
0.05at% ≦ X ≦ 10at%
(Here, X represents at least one element selected from the group consisting of Zn, Al, Pd, In, Sn, Cr, and Ni, provided that the total amount of Cu, Ag, and X is 100 at% or less. .)
Here, the preferable content range of Cu, Ag, and the third element species X may be the same as the composition (A) described as the composition of the reflective layer.

The melting point of X is 660.4 ° C. for Al, 1550 ° C. for Pd, 231.97 ° C. for Sn, and 156.6 ° C. for In other than Zn described above (Iwanami Rikagaku Dictionary 5th edition) , Iwanami Shoten, 1998).
Of the above X, Zn, Al, Pd, In, and Sn are particularly preferable.

  As described above, the sputtering target has a small difference in melting point. Therefore, it becomes possible to omit the production of the mother alloy described in the above-mentioned Patent Document 4 (International Publication No. WO2002 / 021524 pamphlet). That is, the following processes are possible. That is, in a high-frequency melting furnace, Cu and Ag are put in a crucible at a predetermined ratio, vacuum-dissolved, and after the Cu and Ag are sufficiently dissolved, the third element species X is added. Alternatively, Cu, Ag, and the third element species X may be put in a crucible at a predetermined ratio in a high-frequency melting furnace, and vacuum melting may be performed. At this time, when adding Al, Cr, Ni, Pd, In, and Sn as the third element species X, they may be added together with Cu and Ag at a predetermined ratio. On the other hand, when adding Zn as the third element species X, it is preferable to add it after Cu and Ag are sufficiently dissolved. This is because when the Zn having a high vapor pressure is charged from the beginning, the composition tends not to become a specified value due to volatilization.

Here, the melting temperature in the furnace is set to about 1100 ° C. to 1200 ° C., and C, Al ₂ O ₃ , MgO, ZrO ₂ or the like is used as the crucible material. Next, the molten metal is cast into a mold, the melt is cooled in the mold and solidified to produce an ingot, and the ingot is taken out of the mold and cooled to room temperature. Next, the uppermost feeder part of the ingot is cut and removed, and the ingot is rolled by a compressor to produce a plate-like alloy. Thereafter, the plate-like alloy is wire-cut into a product shape, and the front surface of the product is polished to finally produce the Cu alloy sputtering target of the present invention.

  In addition, when the above-mentioned master alloy manufacturing process is required, the melting point of the main element (Cu in the above sputtering target) and the melting point of the additive element are usually extremely high, such as about several hundred degrees C. is there. If Ti having a melting point of 1668 ° C. is added to a molten main element Cu (about 1000 ° C.), alloying proceeds by solid diffusion, but the rate is slow and it is difficult to form an alloy with a uniform yield. If the ratio of the amount of Cu and Ti is 1: 1, the melting point is 960 ° C. due to the correlation. Therefore, it is possible to easily alloy the molten main element. However, there are some that do not require parent alloying even if their melting points differ greatly. It is Pd as X. Even if Pd (melting point: 1554 ° C.) is added to Ag at a molten metal temperature of 1100 ° C. without being made into a mother alloy, alloying proceeds easily because the diffusion rate is high.

  The sputtering target described above provides an excellent reflective layer as described later. For this reason, from the viewpoint of only the reflective layer formed using the sputtering target, the organic dye to be contained in the recording layer of the optical recording medium using the reflective layer is not particularly limited. Such organic dyes include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, azurenium dyes, azo dyes Examples thereof include metal chelate dyes and metal-containing indoaniline dyes. Of these organic dyes, it is preferable to use an azo metal chelate dye or a phthalocyanine dye in consideration of various factors such as productivity, performance, and results. Preferable examples of the azo metal chelate dye include azo metal chelate dyes composed of the azo compound having the predetermined structure and metal ions of Ni and Zn. However, as described above, the reflection layer exhibits a predetermined effect when used in combination with a recording layer containing a “dye having poor light resistance”.

  Next, physical properties at a recording / reproducing wavelength preferable for the recording layer and the reflective layer are shown. It is desirable to maintain an appropriate reflectivity at the laser wavelength at which recording is performed due to restrictions on the drive or optical system for recording. Also, for example, in DVD-R, the refractive index (n) after recording generally decreases, so that the refractive index (n) of the recording layer before recording is high, and the absorption is smaller than a certain amount. This is a necessary condition for ensuring a sufficient signal amplitude after recording. Further, if the reflective layer is thin, the transmitted light increases and the components that do not contribute to the signal increase. Therefore, the reflective layer needs to have a film thickness of a certain thickness or more.

For this purpose, in the recording layer, the refractive index (n _w ) at the recording / reproducing wavelength is n _w ≧ 1.4, and the extinction coefficient (k _w ) at the recording / reproducing wavelength is k _w ≦ 0.3, It is preferable that the film thickness (d _w ) in the groove satisfies 0.05 ≦ (n _w d _w /λ)≦0.3. In addition, when the reflective layer is not used as a semitransparent film, the reflective layer preferably has a film thickness (d _r ) satisfying 50 nm ≦ d _r ≦ 250 nm. The upper limit of n _w is usually 4.0. The lower limit of k _w is usually 0.01.

  When the recording layer and the reflective layer satisfy the above optical constants and film thicknesses, it is possible to obtain a high reflectance at a recording / reproducing light wavelength and a sufficient signal amplitude after recording, which are necessary for recording with a drive.

[II. Embodiment of the Invention]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  The first optical recording medium of the present invention is not particularly limited as long as it has the recording layer and the reflective layer described above on the substrate, but a preferable configuration is shown in FIG. A configuration in which a recording layer and a reflective layer are sandwiched between two substrates, as represented by the configuration represented by a) and (b), and a configuration represented by 1 in the configuration represented by FIG. A configuration in which a reflective layer and a recording layer are laminated on a single substrate can be mentioned. Furthermore, the present invention can also be applied to a single-sided two-layer type configuration as shown in FIGS. 1A to 1C and FIGS. 2A and 2B are schematic cross-sectional views showing the layer structure of the optical recording medium according to the embodiment of the present invention.

  An optical recording medium 100 shown in FIG. 1A includes a substrate (1) 101, a recording layer (1) 102, a reflective layer (1) 103, a protective coat layer (1) 104, an adhesive layer 105, The protective coat layer (2) 106, the reflective layer (2) 107, the recording layer (2) 108, and the substrate (2) 109 are laminated in this order. Such an optical recording medium 100 includes a bonding disk 11 in which a substrate (1) 101, a recording layer (1) 102, a reflective layer (1) 103, and a protective coating layer (1) 104 are laminated in this order, and a substrate ( 2) 109, a recording layer (2) 108, a reflective layer (2) 107, a protective coating layer (2) 106, and a laminating disk 12 in this order, a protective coating layer (1) 104 and a protective coating layer ( 2) It is configured by bonding 106 with the adhesive layer 105 facing each other. By irradiating the laser beam 110 from the substrate (2) 109 side, the recording layer (2) 108 is irradiated from the substrate (1) 101 side by irradiating the laser beam 111 from the substrate (1) 101 side. In FIG. 4, information is recorded and reproduced.

  The optical recording medium 200 shown in FIG. 1B includes a substrate (1) 201, a reflective layer (1) 202, a protective coat layer (1) 203, an adhesive layer 204, and a protective coat layer (2) 205. The reflection layer (2) 206, the recording layer 207, and the substrate (2) 208 are stacked in this order. Such an optical recording medium 200 includes a dummy disk 21 in which a substrate (1) 201, a reflective layer (1) 202, and a protective coat layer (1) 203 are laminated in this order, a substrate (2) 208, a recording layer 207, a reflective layer. The bonding disk 22 in which the layer (2) 206 and the protective coating layer (2) 205 are laminated in this order is bonded to the bonding layer 204 with the protective coating layer (1) 203 and the protective coating layer (2) 205 facing each other. Composed by combining. Information is recorded / reproduced in the recording layer 207 by irradiating the laser beam 210 from the substrate (2) 208 side.

  An optical recording medium 300 shown in FIG. 1C has a layer configuration in which a substrate 301, a reflective layer 302, a recording layer 303, a barrier layer 304, and a transparent resin layer 305 are sequentially laminated. In this optical recording medium 300, information is recorded / reproduced on the recording layer 303 by irradiating the laser beam 310 from the transparent resin layer 305 side instead of the substrate 301 side (film surface incidence type).

  An optical recording medium 400 shown in FIG. 2A includes a substrate (1) 401, a recording layer (1) 402, a reflective layer (1) 403, an intermediate layer 404, a recording layer (2) 405, a reflective layer. The layer (2) 406, the adhesive layer 407, and the substrate (2) 408 are stacked in this order. Also, the optical recording medium 500 shown in FIG. 2B includes a substrate (1) 501, a recording layer (1) 502, a reflective layer (1) 503, an adhesive layer (intermediate layer) 504, and a barrier layer 508. A recording layer (2) 505, a reflective layer (2) 506, and a substrate (2) 507 are stacked in this order. In these optical recording media 400 and 500, information is recorded in the recording layers (1) 402 and 502 and the recording layers (2) 405 and 505 by irradiating laser beams 410 and 510 from the substrate (1) 401 and 501 side. Is recorded and played back.

  The recording layer (1) 102 and the recording layer (2) 108 of the optical recording medium 100 shown in FIG. 1A, the recording layer 207 of the optical recording medium 200 shown in FIG. 1B, and FIG. The recording layer 303 of the optical recording medium 300 shown, the recording layer (1) 402 and the recording layer (2) 405 of the optical recording medium 400 shown in FIG. 2A, and the recording layer of the optical recording medium 500 shown in FIG. As the (1) 502 and the recording layer (2) 505, the above-described recording layer of the present invention can be applied. Further, in combination with these recording layers, the reflective layer (1) 103 and the reflective layer (2) 107 of the optical recording medium 100 shown in FIG. 1A, and the reflective layer of the optical recording medium 200 shown in FIG. (1) 202 and the reflective layer (2) 206, the reflective layer 302 of the optical recording medium 300 shown in FIG. 1C, the reflective layer (1) 403 and the reflective layer of the optical recording medium 400 shown in FIG. 2) As the reflective layer (1) 503 and the reflective layer (2) 506 of the optical recording medium 500 shown in 406 and FIG. 2B, the above-described reflective layer of the present invention can be applied.

  Various modifications may be made to the configurations of the optical recording media 100, 200, and 300 in FIGS. 1A to 1C and the optical recording media 400 and 500 in FIGS. 2A and 2B. is there. For example, other layers may be provided in addition to the above-described layers, some layers may be omitted, or the stacking order of the layers may be changed without departing from the spirit of the present invention. As a specific example, in the optical recording medium 200 of FIG. 1B, the reflective layer (1) 202 and the protective coat layer (1) 203 are omitted, and the substrate 201 is directly attached to the bonding disk 22 by the adhesive layer 204. It is good also as a structure bonded together. Further, in the optical recording media 100 and 200 of FIGS. 1A and 1B, the protective coat layers (1) 104 and 203 and the protective coat layers (2) 106 and 205 are not provided, but instead, the protective coat layers. Adhesion layers 105 and 204 having the above functions may be used for adhesion.

  As another modified example, an ultraviolet curable resin layer, an inorganic thin film, or the like may be formed on the mirror surface side of the substrate in order to protect the surface or prevent adhesion of dust. In addition, a print receiving layer that can be written (printed) on various printers such as ink jet and thermal transfer or various writing tools may be provided on the surface other than the incident surface of the recording / reproducing light.

  The material of the substrate in the optical recording medium according to the embodiment of the present invention may be basically transparent at the wavelength of the recording light and the reproducing light in the thickness direction up to the recording layer.

  Examples of the material having such a transparent thickness portion include resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, and epoxy resins. The thing which provided the resin layer which consists of radiation curable resin, such as a thing, glass, and photocurable resin on glass, etc. can be used.

  In view of high productivity, cost, moisture resistance, etc., injection molded polycarbonate is preferable. Amorphous polyolefin is preferred from the standpoint of chemical resistance and moisture absorption resistance. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.

  A resin substrate or a resin layer may be provided in contact with the recording layer, and guide grooves or pits for recording / reproducing light may be provided on the resin substrate or resin layer. Such guide grooves and pits are preferably provided at the time of forming the substrate, but can also be provided on the substrate using an ultraviolet curable resin layer. When the guide groove has a spiral shape, the groove pitch is preferably about 0.1 to 2.0 μm.

  The groove depth is an AFM (Atomic Force Microscope) measurement and is usually 50 nm or more. The red semiconductor laser light such as DVD-R usually has a wavelength of 100 nm or more. In particular, the recording speed is 1 × from a low speed (hereinafter sometimes referred to as “1 ×”) to 8 × at a high recording speed. In order to be able to record in a range, the groove depth is 120 nm or more. The groove depth is usually 200 nm or less, preferably 180 nm or less. When the groove depth is larger than the above lower limit value, the degree of modulation tends to be obtained at a low speed, and when the groove depth is smaller than the above upper limit value, it is easy to ensure a sufficient reflectance. The groove width is a value measured by AFM (atomic force microscope) and is usually 0.10 μm or more, preferably 0.20 μm or more. The groove width is preferably 0.40 μm or less. For high-speed recording with red semiconductor laser light such as DVD-R, the groove width is more preferably 0.28 μm or more and 0.34 μm or less. When the groove width is larger than the above lower limit value, the push-pull signal amplitude is easily obtained. Further, the deformation of the substrate greatly affects the recording signal amplitude. Therefore, if the groove width is made larger than the above lower limit value, it becomes easy to suppress the influence of thermal interference and obtain good jitter when recording at a high speed of 8 × or more. Furthermore, the recording power margin is widened and the tolerance for fluctuations in laser power is increased, so that the recording characteristics and recording conditions are improved. When the groove width is smaller than the above upper limit value, thermal interference in the recording mark can be suppressed in low-speed recording such as 1 ×, and a good jitter value can be easily obtained.

  Information such as address information, medium type information, recording pulse conditions, and optimum recording power can be recorded on the optical recording medium according to the embodiment of the present invention. As a form for recording such information, for example, a format of LPP (Land Pre-Pit) or ADIP (Adress in Pre-groove) described in the DVD-R and DVD + R standards may be used.

  The recording layer material, mixing ratio, and film thickness are as described above. In addition, it is preferable that the film thickness of an inter-groove part is smaller than the film thickness in a groove | channel.

  Examples of the method for forming the recording layer include vacuum film forming methods, sputtering methods, doctor blade methods, cast methods, spin coating methods, dipping methods, and the like, but from the viewpoint of mass productivity and cost, A spin coating method is preferred. From the viewpoint that a recording layer having a uniform thickness can be obtained, the vacuum vapor deposition method is preferable to the coating method.

  In the case of film formation by spin coating, the rotation speed is preferably 10 to 15000 rpm, and after spin coating, treatment such as heating or application to solvent vapor may be performed.

  The coating solvent for forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method, or a dipping method may be any solvent that does not attack the substrate and is not particularly limited. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; perfluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Examples of the solvent include hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.

In the case of the vacuum deposition method, for example, an organic dye and, if necessary, recording layer components such as various additives are put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is 10 ⁻² to After evacuating to about 10 ⁻⁵ Pa, the crucible is heated to evaporate the recording layer components and deposited on a substrate placed facing the crucible to form a recording layer.

  The recording layer is used for a near-infrared laser having a wavelength of about 770 to 830 nm and a DVD-R, which are usually used for CD-R, in addition to the above-mentioned compounds for improving the stability and light resistance of the recording layer. In combination with a plurality of wavelengths of recording light, such as a red laser having a wavelength of about 620 to 690 nm or a so-called blue laser having a wavelength of 410 nm or 515 nm, a plurality of wavelength regions are combined. It is also possible to provide an optical recording medium corresponding to recording with laser light.

  As the dyes that can be used in combination, the same kind of azo metal chelate dyes having the above specific characteristics or structure, azo dyes or azo metal chelate dyes, cyanine dyes, squarylium dyes, naphthoquinone dyes, anthraquinone dyes, Porphyrin dyes, tetrapyraporphyrazine dyes, indophenol dyes, pyrylium dyes, thiopyrylium dyes, azurenium dyes, triphenylmethane dyes, xanthene dyes, indanthrene dyes, indigo dyes, thioindigo dyes Examples include dyes, merocyanine dyes, bispyromethene dyes, thiazine dyes, acridine dyes, oxazine dyes, indoaniline dyes, and the like. Examples of the dye thermal decomposition accelerator include metal compounds such as metal anti-knock agents, metallocene compounds, and acetylacetonate metal complexes.

  Furthermore, a binder, a leveling agent, an antifoaming agent, and the like can be used in combination in the recording layer of the present invention as necessary. Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.

The material and composition of the reflective layer are as described above.
Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.
The thickness of the reflective layer is set to the following range in consideration of recording characteristics and industrial production. That is, the thickness of the reflective layer is usually 50 nm or more, preferably 60 nm or more, and is usually 300 nm or less, preferably 250 nm or less, more preferably 200 nm or less.

  Further, the roughness (particle size) of the film of the reflective layer is preferably as small as that of a gold thin film or less from the viewpoint of weather resistance and reflectance. In particular, in the case of high-density recording with a short recording / reproducing light wavelength, the roughness of aluminum is likely to increase. Therefore, a device for improving the smoothness by alloying is required. Further, in order to reduce the roughness of the film of the reflective layer, a device such as reducing the argon pressure at the time of sputtering can be cited.

The material of the protective layer formed on the reflective layer is not particularly limited as long as it protects the reflective layer from external force. Examples of the organic material include thermoplastic resins, thermosetting resins, electron beam curable resins, and UV curable resins. Examples of inorganic substances include SiO ₂ , SiN ₄ , MgF ₂ , SnO _{2 and the} like.

  A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying. The UV curable resin can be formed by preparing a coating solution as it is or by dissolving in a suitable solvent, and then applying the coating solution and curing it by irradiating with UV light. As the UV curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.

  As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a spin coating method is preferable.

  The thickness of the protective layer is usually 0.1 μm or more, preferably 3 μm or more. On the other hand, the thickness of the protective layer is usually 100 μm or less, preferably 30 μm or less.

  There is no particular limitation on the laser used for recording / reproduction, but for example, a dye laser capable of selecting a wavelength in a wide range in the visible region, a helium neon laser having a wavelength of 633 nm, and a recently developed wavelength around 680, 660, 650, and 635 nm. Examples include a high-power semiconductor laser, a harmonic conversion YAG laser having a wavelength of 532 nm, and a blue semiconductor laser having a wavelength of about 405 nm. Among these, a semiconductor laser is preferable in terms of lightness, ease of handling, compactness, cost, and the like. The optical recording medium according to the embodiment of the present invention can perform high-density recording and reproduction at one wavelength or a plurality of wavelengths selected from these.

  Recording on the optical recording medium according to the embodiment of the present invention is usually performed by irradiating a recording layer provided on both sides or one side of the substrate with a laser beam focused to about 1 μm. As a result of the temperature rise due to the absorption of laser light energy, the recording layer irradiated with laser light undergoes thermal changes in the recording layer such as decomposition, heat generation, and melting, and changes in optical characteristics such as phase difference and optical constant To do.

  Reproduction of recorded information is performed by irradiating a reproduction laser beam and reading a difference in reflectance between a portion where a change in optical characteristics occurs and a portion where the change does not occur.

[III. Basic concept 2 of the present invention]
The azo metal chelate dye comprising the azo compound represented by the general formula (1) and a metal ion of Zn is the above [I. A recording layer containing at least an organic dye on a substrate having concentric or spiral grooves without being limited to the optical recording medium described in the basic concept 1] of the present invention (the first optical recording medium of the present invention). And an organic dye for the recording layer in an optical recording medium having a minimum mark length of less than 0.4 μm or recording at a recording linear velocity of 35.0 m / s or more. It can be used widely.

  That is, another optical recording medium of the present invention has a recording layer containing at least an organic dye and a reflective layer containing a metal on a substrate having concentric or spiral grooves, and the shortest mark length is 0. An optical recording medium for recording at a recording linear velocity of less than 4 μm or 35.0 m / s or more, wherein the organic dye of the recording layer comprises an azo compound represented by the general formula (1) and Zn An azo metal chelate dye consisting of the above metal ions (this may be hereinafter referred to as “the second optical recording medium of the present invention”). According to the second optical recording medium of the present invention, there is an advantage that it is particularly excellent in life characteristics (long-term storage stability and storage stability under high temperature and high humidity).

  In the second optical recording medium of the present invention, details and specific examples of the azo compound represented by the general formula (1) and details of an azo metal chelate dye comprising the azo compound and a Zn metal ion And specific examples are described in [I. This is the same as that described in the section “Basic concept 1 of the present invention”.

Note that, also in the second optical recording medium of the present invention, it is preferable that the reflective layer of the optical recording medium contains the material represented by the composition (A). According to the optical recording medium having such a configuration, it is possible to obtain an advantage that a decrease in reflectance can be suppressed to a minimum and life characteristics are excellent.
The details and specific examples of the composition (A) in the second optical recording medium of the present invention are also described in [I. This is the same as that described in the section “Basic concept 1 of the present invention”.

[IV. Basic concept 3 of the present invention]
In addition, a sputtering target having at least a material represented by the above-described composition B is also described in [I. It is not limited to the formation of the reflective layer of the optical recording medium (the first optical recording medium of the present invention) described in “Basic Concept 1 of the Present Invention”, and at least an organic dye is formed on a substrate having concentric or spiral grooves. In an optical recording medium having a recording layer containing a metal and a reflective layer containing a metal, it can be widely used when forming the reflective layer.

That is, the sputtering target of the present invention forms the reflective layer on an optical recording medium having a recording layer containing at least an organic dye and a reflective layer containing a metal on a substrate having concentric or spiral grooves. It is a sputtering target used at the time, and has at least a material represented by the above-mentioned composition B. According to the sputtering target of the present invention, it is possible to provide a high-quality medium that can suppress a decrease in reflectivity to a minimum and has excellent life characteristics, and can be manufactured at a lower cost.
The details and specific examples of the composition B in the sputtering target of the present invention are described in [I. This is the same as that described in the section “Basic concept 1 of the present invention”.

  In the sputtering target of the present invention, the organic dye is an azo metal chelate dye composed of the azo compound represented by the general formula (1) and a metal ion of Ni and Zn. It is particularly preferably used for forming. By using the sputtering target of the present invention for the formation of the reflective layer of such an optical recording medium, there is an advantage that the medium can be manufactured at a low cost without almost changing the conventional manufacturing process.

[V. Basic concept 4 of the present invention]
An azo metal chelate dye comprising an azo compound represented by the general formula (1) and a metal ion of Zn has a recording layer containing at least an organic dye on a substrate having concentric or spiral grooves, Widely and suitably used as the organic dye of an optical recording medium having a reflective layer containing a metal and having a shortest mark length of less than 0.4 μm or recording at a recording linear velocity of 35.0 m / s or more. It is possible.
The azo metal chelate dye comprising the azo compound represented by the general formula (1) and a metal ion of Zn is hereinafter referred to as “the dye of the present invention”. By using the dye of the present invention for the above-mentioned optical recording medium for high-speed recording or high-density recording, there can be obtained an advantage that a low jitter, a low error rate, and a wide recording margin can be achieved as compared with the conventional one.
The details and specific examples of the azo compound represented by the above general formula (1) and the details and specific examples of the dye of the present invention possessed by the dye of the present invention are described in [I. This is the same as that described in the section “Basic concept 1 of the present invention”.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded.

[Measurement method of monolayer dye retention]
In each of the following Examples and Comparative Examples, the dye retention was measured according to the following procedure unless otherwise specified.
First, a polycarbonate substrate having a mirror finish was prepared. Using a tetrafluoropropanol (hereinafter referred to as “TFP”) solution with a concentration of the dye mixture to be measured of 1.4% by weight, spin coating was performed in the same manner as in the preparation of the dye layer in each of the following Examples and Comparative Examples. did. A small piece of the obtained dye single layer was cut out, and the wavelength dispersion of the absorbance was measured using a spectrophotometer (UV-VIS). The maximum value of the obtained absorbance was used as the initial value.

Next, using a light resistance tester (Suntest XLS + manufactured by Toyo Seiki Co., Ltd.), integrated irradiation satisfying the Wool scale class 5 was measured, and the apparatus was calibrated. The small piece of the dye single layer was irradiated with light having the irradiation intensity, and the wavelength dispersion of the absorbance was again measured with a spectrophotometer. The ratio between the maximum absorbance obtained here and the above-mentioned initial value was defined as the dye retention. In each of the following examples and comparative examples, irradiation with a 2200 W xenon lamp at a radiation intensity of 550 W / m ² for 40 hours was a setting condition satisfying the Wool scale class 5.

[Measurement method of reflectance]
In each of the following Examples and Comparative Examples, unless otherwise specified, the reflectance of the reflective layer in air was measured according to the following procedure. That is, using a sample in which the material of the reflective layer was sputtered onto a slide glass, reflectance measurement light was irradiated from the film surface (apparatus: Hitachi U3010 type spectrophotometer, measurement mode: reflection measurement mode, scan speed: 300 nm / min, Slit: 1 nm). DR / dλ with respect to the wavelength λ = 300 nm to 500 nm was calculated from the measured reflectance value, and the maximum value dR / dλ (max) was determined.

[Example 1]
On a support substrate made of polycarbonate having a thickness of 0.6 mm having guide grooves having a track pitch of 0.74 μm, a groove width of 320 nm, and a groove depth of 160 nm, two dyes A (two azo compounds represented by the following structural formula (a) and 40 wt% of an azo metal chelate dye comprising nickel and 60 wt% of a dye B (azo metal chelate dye comprising two azo compounds represented by the following structural formula (b) and zinc (divalent ion: Zn ²⁺ )) % Recording layer (thickness in the groove 50 nm) was provided by spin coating so as to have a thickness of 0.65 (absorbance at a wavelength of 598 nm, measured with Optical Density: air as a reference). The coating solution was a TFP solution having a concentration of 1.3% by weight, and the spin coating speed was 1000 rpm to 2500 rpm. Next, copper (Cu) was deposited thereon by sputtering to form a Cu reflective layer having a thickness of 120 nm. At the time of sputtering, the argon pressure was made smaller than the well-known conditions for forming the reflective layer to increase the input power. Further, an ultraviolet curable resin (KAYARAD SPC-920 manufactured by Nippon Kayaku Co., Ltd.) was spin-coated on this reflective layer and cured to form a 10 μm protective layer. Two sheets of the laminate thus obtained were prepared, and an optical recording medium was manufactured by using a UV curable adhesive (SK7100 manufactured by Sony Chemical Co., Ltd.) so that the two substrates were bonded to the outside.

  The dye retention rates of the dye single layer coating films of the dye A and the dye B were 90.4% and 0%, respectively, and the dye retention ratio of the recording layer single layer was 56%.

  Moreover, the reflectance and dR / dλ value of the Cu reflective layer single layer were measured by the above-described method. The results are shown in the graphs of FIG. 8 and FIG. 9 (a), respectively. The reflectance of 300 nm to 500 nm of the Cu reflective layer single layer was 29% to 56% (FIG. 8). The value of dR / dλ (max) in the same wavelength region was 0.36 (FIG. 9 (a)).

  For the obtained optical recording medium, a recording / reproducing apparatus having a wavelength of 650 nm and a numerical aperture of 0.65 was used with a recording pulse strategy condition compliant with DVD-R Specification for General Ver.2.1 and DVD + R Specification Ver.1.20. EFM plus modulation random signal recording with a shortest mark length of 0.4 μm was performed at a recording speed of 56.0 m / s (16 × speed of DVD-R). The irradiation pulse width of the laser for 3T mark length recording was 6.5 ns. Then, the recorded signal was reproduced using the same evaluator, and the margins (jitter recording power margin and jitter asymmetry margin) were measured. In addition, recording for evaluation of “practical” light resistance (recording characteristics evaluation before and after xenon irradiation) is performed at 8 × speed, and the minimum value of data to clock jitter (the best data to clock jitter) Jitter characteristic value (hereinafter referred to as “bottom jitter”) and the maximum value of PI (Parity of Inner-code) error (hereinafter referred to as “PI max”) using a DVD-ROM inspection machine (LM2 20A manufactured by Shibasoku Co., Ltd.) It was measured.

  The measurement result of the recording power margin is shown in the graph of FIG. 4A, and the measurement result of the asymmetry margin is shown in the graph of FIG. 4B. As is apparent from FIGS. 4A and 4B, the optical recording medium of this example using the Cu reflective layer had a very good bottom jitter of 7%. In addition, the asymmetry margin at which the jitter is 9% or less is about 18%, the asymmetry margin at which the jitter is 8% or less is 10% or more, and the jitter is around 8% even in the vicinity of 5% asymmetry. .

  The measurement results before and after the bottom jitter light resistance test are shown in the graph of FIG. 4C, and the measurement results of PI max are shown in the graph of FIG. 4D. As apparent from FIGS. 4C and 4D, in the optical recording medium of this example using the Cu reflective layer, the bottom jitter slightly increased even when the xenon irradiation time was 40 hours (Wool scale 5). However, PI max does not increase at all, and it can be seen that the “practical” light resistance is greatly improved as compared with the case of the Ag reflection layer described later.

[Example 2]
An optical recording medium was manufactured in the same manner as in Example 1, except that the material of the reflective layer was changed to gold (Au) and the film thickness was changed to 90 nm. Recording and reproduction were performed on the obtained optical recording medium under the same conditions as in Example 1, and bottom jitter and PI max before and after the light resistance test were measured.

  The measurement result of bottom jitter is shown in the graph of FIG. 4C, and the measurement result of PI max is shown in the graph of FIG. 4D. As is apparent from FIGS. 4C and 4D, the optical recording medium of this example using the Au reflective layer is slightly less effective than the Cu reflective layer, but good results are obtained. It was.

  Further, the reflectance and dR / dλ of the Au reflective layer single layer were measured by the above-described method. The results are shown in the graphs of FIGS. 8 and 9 (b), respectively. The reflectance of 300 nm to 500 nm of the Au reflective layer single layer was 37% to 50% (FIG. 8). In addition, the value of dR / dλ (max) in the same wavelength region was 0.72 (FIG. 9B).

[Comparative Example 1]
An optical recording medium was manufactured in the same manner as in Example 1, except that the material of the reflective layer was changed to silver (Ag) and the film thickness was changed to 120 nm. Recording and reproduction were performed on the obtained optical recording medium under the same conditions as in Example 1, and margins (recording power margin and asymmetry margin), bottom jitter before and after the light resistance test, and PI max were measured.

  The measurement result of the recording power margin is shown in the graph of FIG. 4A, and the measurement result of the asymmetry margin is shown in the graph of FIG. 4B. As is apparent from FIGS. 4A and 4B, the optical recording medium of this comparative example using the Ag reflective layer has lower bottom jitter and asymmetric margin as compared with the case of the Cu reflective layer. You can see that it is narrow.

  Further, the measurement result of bottom jitter is shown in the graph of FIG. 4C, and the measurement result of PI max is shown in the graph of FIG. 4D. As apparent from FIGS. 4C and 4D, the optical recording medium of this comparative example using the Ag reflection layer has bottom jitter and error (PI) under the conditions of Wool scale 5 (40 hours of xenon irradiation). It can be seen that the Ag reflection layer cannot withstand the Wool scale grade 5 condition, that is, it is inferior in “practical” light resistance. The error (PI max) is described as a requirement in the DVD-R standard that it does not exceed 280.

  Further, the reflectance and dR / dλ values of the single Ag reflection layer were measured by the above-described method. The results are shown in the graphs of FIG. 8 and FIG. 9 (c), respectively. The reflectance of 300 nm to 500 nm of the single Ag reflection layer was 4% to 96% (FIG. 8). The value of dR / dλ (max) in the same wavelength region was 5.6 (FIG. 9 (c)).

[Example 3]
In Example 1, the dye A was changed to Ni complex dye C (65 wt%) (Ni is a divalent ion: Ni ²⁺ ) in which two azo compounds represented by the following structural formula (c) are coordinated, and the dye An optical recording medium was produced by the same procedure except that B was changed to a cyanine dye D (35% by weight) represented by the following structural formula (d). In addition, it was 25 nm when the film thickness in the groove | channel of a recording layer was confirmed by the cross-sectional analysis by an electron microscope. Further, the film thickness of the Cu reflective layer was 120 nm as in Example 1. Recording and reproduction were performed on this optical recording medium under the same conditions as in Example 1, and margins (recording power margin and asymmetry margin), bottom jitter before and after the light resistance test, and PImax were measured.

  The dye retention rates of the dye single layer coating films of the dye C and the dye D were 97.0% and 0%, respectively, and the dye retention ratio of the recording layer single layer was 68.2%.

  The measurement result of the recording power margin is shown in the graph of FIG. 5A, and the measurement result of the asymmetry margin is shown in the graph of FIG. 5B. As is apparent from FIGS. 5A and 5B, the optical recording medium of this example using a Cu reflective layer realizes a very stable power margin with a power margin of about 10 mw with a jitter of 9% or less. Has been. Further, even if the asymmetry exceeds + 6.0%, it has a jitter of 9% or less, and the asymmetry margin of the jitter of 9% or less shows a very wide margin of about 20%. The fact that these margins are very good means that the thermal deterioration (heat storage and thermal interference) of the recording mark is small even at extremely high speed recording of 56 m / s (16 × speed).

  Further, the measurement result of bottom jitter is shown in the graph of FIG. 5C, and the measurement result of PI max is shown in the graph of FIG. 5D. As is clear from FIGS. 5C and 5D, the optical recording medium of this example using the Cu reflective layer has much more “practical” light resistance than the case of the Ag reflective layer described later. It can be seen that Then, it can be seen that an optical disk having Wool scale Grade 5 “practical” light resistance can be realized while including a dye D having a dye retention rate of 0% and a much lower light resistance in the dye single layer.

[Comparative Example 2]
In Example 3, an optical recording medium was prepared in the same procedure except that the material of the reflective layer was changed from copper to silver and an Ag reflective layer having a thickness of 120 nm was provided. Recording and reproduction were performed on this optical recording medium under the same conditions as in Example 1, and margins (recording power margin and asymmetry margin), bottom jitter before and after the light resistance test, and PI max were measured.

  The measurement result of the recording power margin is shown in the graph of FIG. 5A, and the measurement result of the asymmetry margin is shown in the graph of FIG. 5B. As is apparent from FIG. 5A, it can be seen that the recording power margin is much narrower in the optical recording medium of this comparative example using the Ag reflective layer than in the case of the Cu reflective layer.

  Further, the measurement result of bottom jitter is shown in the graph of FIG. 5C, and the measurement result of PI max is shown in the graph of FIG. 5D. In the optical recording medium of this comparative example using the Ag reflection layer, the bottom jitter after 40 hours deteriorated in FIG. 5C, and the error (PI max) far exceeded 280 in FIG. ing. From this, it can be seen that the optical recording medium of this comparative example using the Ag reflection layer cannot withstand the Wool scale 5 grade.

[Example 4]
Except for changing the recording speed to 35.0 m / s (equivalent to 10 ×) for the optical recording medium of Example 3 and changing the irradiation pulse width of the laser for 3T mark length recording to 7.9 ns, the Example Recording / reproduction was performed under the same conditions as in No. 1, and margins (recording power margin and asymmetry margin) were measured.

  The measurement result of the recording power margin is indicated by a mark in FIG. 6A, and the measurement result of the asymmetry margin is indicated by a mark in the graph of FIG. 6B. As shown in FIG. 6 (a), in the present embodiment in which recording was performed at 35.0 m / s, very good recording with a bottom jitter of 6.0% was possible as in the case of 56.0 m / s recording. I understand that.

[Comparative Example 3]
Except that the recording speed was changed to 35.0 m / s (equivalent to 10 ×) for the optical recording medium of Comparative Example 2 and the irradiation pulse width of the laser for recording the 3T mark length was changed to 7.9 ns. Recording / reproduction was performed under the same conditions as in No. 1, and margins (recording power margin and asymmetry margin) were measured.

  The measurement result of the recording power margin is shown in the graph of FIG. 6A, and the measurement result of the asymmetry margin is shown in the graph of FIG. 6A and 6B, the bottom jitter is 6.7%, which is relatively good, but the power margin is relatively inferior compared with the optical recording medium using the Cu reflective film of Example 4. I understand that.

[Comparative Example 4]
In Example 1, a “complex light-resistant” Ni complex dye E (Ni is divalent) in which two “azo compounds” represented by the following structural formula (e) are coordinated with the “light-inferior” dye B An optical recording medium was prepared by the same procedure as in Example 1 except that the dye A and the dye E were mixed at a ratio of 50% by weight: 50% by weight instead of the ion: Ni ²⁺ ). The film thickness in the groove of the obtained recording layer was 30 nm. The film thickness of the Cu reflective layer was 120 nm.

尚、色素Ｅ単層塗布膜の色素保持率は８７．３％であり、この記録層単層の色素保持率は８９．０％であった。

The dye retention rate of the dye E single layer coating film was 87.3%, and the dye retention rate of this recording layer single layer was 89.0%.

  Recording and reproduction were performed on this optical recording medium under the same conditions as in Example 1, and margins (recording power margin and asymmetry margin), bottom jitter before and after the light resistance test, and PI max were measured.

  The measurement result of the recording power margin is shown in the graph of FIG. 7A, and the measurement result of the asymmetry margin is shown in the graph of FIG. 7B. As is apparent from FIGS. 7A and 7B, even when the reflective layer is a Cu reflective layer, the characteristics are not significantly improved. It can be seen that the bottom jitter is 9% or more, and both the power margin and the asymmetry margin are extremely narrow. In particular, the asymmetry margin is poor, and thermal degradation has already been seen even at a recording power as low as -5%, and the jitter has deteriorated by 1% or more than the bottom jitter. The asymmetry margin is preferably 9% or less of jitter at 5%.

Further, the measurement result of bottom jitter is shown in the graph of FIG. 7C, and the measurement result of PI max is shown in the graph of FIG. 7D. As is apparent from FIGS. 7C and 7D, the “practical” light resistance was very good.
When the reflective layer on the recording layer is changed to the same Ag reflective layer as in Comparative Example 1, the bottom jitter in the light resistance test is changed from 6.9% to 7.0%, and the light resistance test is performed. PI max varied from 5 to 8 respectively, indicating very good “practical” light resistance.

  From the above results, in the optical recording medium of this comparative example using a recording layer containing only a dye having good light resistance, thermal deterioration is large at extremely high speed recording of 16 × recording, and a good recording mark is obtained. It can be seen that it is not formed. The degree of deterioration is large, and even if a Cu reflective layer is used, it can be said that it is difficult to improve.

[Single speed recording test]
For the optical recording media of Example 1, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 4 described above, recording / reproduction was performed under the same conditions as in Example 1 except that the recording speed was changed to 1 × speed. The bottom jitter was measured. The results are shown in Table 1 below.

  In general, the bottom jitter is required to be 9% or less. As is apparent from Table 1, the optical recording media of Example 1, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 4 were all good recording with a bottom jitter of 9% or less in 1 × speed recording. The characteristics are shown. Nevertheless, superiority and inferiority are observed in high-speed recording as described above.

  From the above results, it can be seen that the optical recording media of the respective examples satisfying the provisions of the present invention exhibit good recording characteristics at very high recording speeds such as 1 × speed, 10 × speed, and 16 × speed.

[Example 5]
The reflectance and dR / dλ of the reflective layer (Al reflective layer single layer) made of aluminum (Al) were measured by the above-described method. The results are shown in the graphs of FIG. 8 and FIG. 9 (d), respectively. As is clear from FIG. 9D, the dR / dλ value of the Al reflective layer single layer was always 0.1 or less in the range of 300 nm to 500 nm.

[Example 6]
Similarly to the above [Reflectance measurement method], Cu 87.2 atomic% / Ag _12.8 atomic% (hereinafter referred to as “CuAg _12.8 ” as appropriate) and Cu 86.4 atomic% / Ag 12.9 atomic% / Pd0. 7 atomic% (hereinafter referred to as “CuAg _12.9 Pd _0.7 ” as appropriate) was sputtered on separate glass slides, and the reflectance was measured from the film surface side. The sputtering conditions were the same as in Example 1.

FIG. 10 is a graph showing the measurement results of the reflectance of CuAg _12.8 and CuAg _12.9 Pd _0.7 together with the measurement results of Ag, Au, and Cu obtained in [Example 5] and the like. In FIG. 10, the horizontal axis represents the wavelength λ (nm) and the vertical axis represents the reflectance (%). As can be seen from FIG. 10, CuAg _12.8 and CuAg _12.9 Pd _0.7 both have optical characteristics that are clearly different from those of Cu, and reflectivity is somewhat closer to Ag than to Cu.

Moreover, dR / dλ of these CuAg _12.8 and CuAg _12.9 Pd _0.7 was calculated. 11A and 11B are graphs showing calculation results of dR / dλ for CuAg _12.8 and CuAg _12.9 Pd _0.7 , respectively. As can be seen from FIGS. 11 (a) and 11 (b), the noise is generally high, but the wavelength range of 300 to 500 nm where the peak wavelength of the maximum value 5.6 of dR / dλ of Ag exists (see FIG. 11). 9), a noise increase of dR / dλ is observed although it is weak.

Here, from the reflectance R _Ag of Ag of Comparative Example 1 and the reflectance R _Cu of Cu of Example 1, the reflectance R at each wavelength of Cu ( _1-X) Ag _X (atomic%: at%). (Cu _(1-X) Ag _X ) was calculated by the following formula.
_{R (Cu (1-X)} Ag X) =
{(1-X) / 100} × R (Cu) + (X / 100) × R (Ag)

  As a result, a spectrum showing the wavelength dependence of the reflectance as shown in FIG. 10 when the mixing ratio of Ag and Cu is arbitrary is obtained. Then, dR / dλ was calculated in the same manner as in FIG. 11A at a predetermined mixing ratio of Ag and Cu, and the maximum value of dR / dλ at 300 to 500 nm was obtained. Here, a graph obtained by plotting the Ag content on the horizontal axis and the maximum value of dR / dλ in the wavelength region of 300 to 500 nm obtained by the above procedure on the vertical axis is shown in FIG. As shown in the figure, it can be seen that there is a correlation between the maximum value of dR / dλ observed at 300 nm to 500 nm and the Ag amount. From the figure, it can be said that dR / dλ is 3 when Ag is approximately 50 at%.

On the other hand, the actual value of the maximum value of dR / dλ at 300 to 500 nm in CuAg _12.8 (see FIG. 11A), the actual value of the maximum value of dR / dλ at 300 to 500 nm in Cu (100 at%) (see FIG. 9 (a)), and the actual value of dR / dλ at 300 to 500 nm in Ag (100 at%) (see FIG. 9C), dR / dλ is 3 because Ag The amount is about 50 at%. That is, it can be said that the actual measurement result also shows good agreement with the previous calculation result. That is, the maximum value of the wavelength range of 300 to 500 nm of dR / dλ derived from Ag is obtained by adding a metal having a small dR / dλ value in the wavelength range of 300 to 500 nm, such as Cu, Al, Au, to Ag. It can be seen that it can be lowered. Therefore, it can be seen that if the Ag content is 50 at% or less, the maximum value of dR / dλ in the wavelength region of 300 to 500 nm can be controlled to 3 or less.

As to whether or not sufficient light resistance can be obtained, the xenon irradiation time of 40 hours in FIG. 4C was compared between the case where the reflective layer was Cu and the case where the reflective layer was Ag. As shown above, the maximum value of dR / dλ in the wavelength region of 300 to 500 nm has a substantially linear correlation with the Ag content. For this reason, assuming that the light resistance has a substantially linear correlation with the Ag content, a jitter value of 13% that can be reproduced by the player is set as an allowable limit of jitter deterioration. Then, bottom jitter values after 40 hours of xenon irradiation in an optical recording medium having a reflective layer of Cu (100 at%) and an optical recording medium having a reflective layer of Ag (100 at%) are plotted in FIG. . That is, FIG. 13 is a graph showing the relationship between the X value (Ag content: at%) and the bottom jitter value in Cu _(100-X) Ag _X under the above assumption. From FIG. 13, it is considered that the upper limit of the Ag content that makes it easy to obtain good jitter characteristics is about 30 at%.

Next, an optical recording medium (hereinafter referred to as “CuAg _12.8 DVD-R” and “CuAg _12.9 Pd _0.7 DVD-”, respectively) was used in the same manner except that the Cu reflective layer was changed to CuAg _12.8 and CuAg _12.9 Pd _0.7 in Example 1. R ”in some cases). And after performing 8 times speed recording with respect to these optical recording media, the light resistance test (however, the xenon irradiation time was set to 120 hours) was performed similarly to Example 1. The results are shown in the graphs of FIG. 14A (jitter value) and FIG. 14B (PI error). In all cases, no deterioration was observed, which was very good, and it was revealed that the copper alloy had the same effect as the Cu reflective layer.

Furthermore, a storage stability test was conducted on CuAg _12.8 DVD-R and CuAg _12.9 Pd _0.7 DVD-R. A storage stability test (sometimes referred to as a life test) uses a thermo-hygrostat (SH-641 manufactured by Espec Corp.) and holds the optical recording medium at 80 ° C. and 85% relative humidity for 875 hours. I did it. The results of the storage stability test of the above CuAg _12.8 DVD-R and CuAg _12.9 Pd _0.7 DVD-R at high temperature and high humidity are shown in the graphs of FIG. 15 (a) (jitter value) and FIG. 15 (b) (PI error). Shown in In FIGS. 15A and 15B, CuAg _12.8 DVD-R is indicated as “CuAg _12.8 ”, and CuAg _12.9 Pd _0.7 DVD-R is indicated as “CuAg _12.9 Pd _0.7 ”. In all cases, the deterioration was very small and extremely good.

[Example 7 and Example 8]
An optical recording medium was produced in exactly the same manner except that the CuAg _12.8 reflective layer or the CuAg _12.9 Pd _0.7 reflective layer in Example 6 was changed to a CuAg _12.8 Zn _1.1 reflective layer and a CuAg _12.9 Zn _10.6 reflective layer (hereinafter referred to as “the recording medium”). CuAg _12.8 Zn _1.1 DVD-R (Example 7), CuAg _12.9 Zn _10.6 DVD-R (Example 8)).

  For each optical recording medium, a light resistance test (results are shown in FIGS. 14A and 14B) and a storage stability test at high temperature and high humidity (results) in the same manner as in Example 6. (Shown in FIG. 15 (a) and FIG. 15 (b)).

In the case where CuAg _12.8 Zn _1.1 is included in the reflective layer, both in the light resistance test and the storage stability test, the same as the case where CuAg _12.8 of Example 6 is included in the reflective layer and the case where CuAg _12.9 Pd _0.7 is included in the reflective layer. It showed very good characteristics. On the other hand, when CuAg _12.9 Zn _10.6 was included in the reflective layer, the storage stability at high temperature and high humidity tended to be slightly inferior compared with other optical recording media. The reason is not clear, but there is room for improvement.

[Example 9]
A sputtering target was produced in accordance with a melting method in vacuum described below.

  First, in a high frequency melting furnace, a predetermined ratio of Cu and Ag was put in a crucible and melted while being sufficiently evacuated. At this time, when adding Pd (Example 6), Al, Cr, Ni (Example 9), and In, Sn (Example 10 described later) as the third element species X, a predetermined amount is included together with Cu and Ag. Added in proportions. On the other hand, when adding Zn (Examples 7, 8, 9 and Example 10 described later) as the third element species X, Cu and Ag were added after sufficiently dissolved. This is because when the Zn having a high vapor pressure is charged from the beginning, the composition does not become a specified value due to volatilization.

The melting temperature in the furnace was 1100 to 1200 ° C. For the crucible, C, Al ₂ O ₃ , MgO, ZrO ₂ or the like was used.
The molten metal was cast by casting it in an Fe or C mold having alumina or magnesium-based talc applied on the inner surface.
In order to prevent shrinkage of the casting mold, the feeder portion was heated to about 300 ° C. to 500 ° C. in advance with a heater before pouring and solidified in one direction from the bottom to the top.

  The melt was cooled and solidified in a mold to produce an ingot, and the ingot was rolled by a rolling mill to produce a plate-like alloy of 90 (mm) x 90 (mm) x 8.1 (mm). .

Then, in a state where Ar gas was sealed at 400 ° C. to 500 ° C. in an electric furnace, the plate-like alloy was heat-treated for about 1 to 1.5 hours, and then warpage was corrected by a press machine.
And the corrected board was wire-cut into a product shape. The front surface of the product was polished using water-resistant abrasive paper to adjust the surface roughness, and finally a Cu alloy sputtering target was prepared.

The degree of vacuum was kept at a high vacuum of 1.3 × 10 ⁻² Pa (1 × 10 ⁻⁴ Torr) or less. Since Ag and Cu are easy to contain oxygen in the molten metal, the purpose is to deoxidize the molten metal under reduced pressure. However, since the volatilization of Ag proceeds under reduced pressure, various atmosphere adjustments were made according to the situation.
A sputtering target having the composition shown in Table 2 below was produced by the above method.

  In order to examine the storage stability and reflectance tendency of the target having the above composition and the sputtered film, the following experiment was conducted. That is, a sputtered film having a thickness of 150 nm, which is thicker than usual, was formed on a glass substrate under the following sputtering conditions. And the reflectance when 650 nm light was irradiated from the film surface side was measured. The reflectance was measured immediately after film formation and after being kept at 80 ° C. under high temperature and high humidity with a relative humidity of 80% for 24 hours. The correlation between the reflectance and the target composition can be known from the measurement result of the reflectance immediately after the film formation. Further, by measuring the change in reflectivity after being kept under high temperature and high humidity for 24 hours and immediately after film formation, the result of extremely strict storage stability test can be obtained. In addition, the spectroscope used for the measurement of said reflectance was Shimadzu Corporation UV-3100PC.

<Sputtering conditions>
Sputtering device = ULVAC (ULVAC) BC4341
Ultimate vacuum = 5 × 10 ^-4 Pa
Ar gas pressure = 0.3Pa
Sputtering power (maximum value) = 200W

  Table 2 shows the measurement results of the reflectance immediately after the film formation, the measurement results of the reflectance after being kept under high temperature and high humidity for 24 hours, and the measurement results of the reflectance change. In Table 2, “time 0” is displayed as “measurement result of reflectance immediately after film formation”. In Table 2, what is displayed as “after 80 ° C. and 80% RH for 24 hours” indicates “a measurement result of the reflectance after being kept under high temperature and high humidity for 24 hours”. In Table 2, what is displayed as “reflectance change” indicates “measurement result of reflectivity change”.

In Table 2, as compared with the binary system of Cu and Ag, the effect of improving the storage stability due to the addition of the third element species X clearly appears. That is, for example, in Cu _87.2 Ag _12.8 , the decrease in reflectance tends to be as large as 26.8%, whereas Cu _84.8 Ag _12.7 Al _2.5 , Cu _86.1 Ag _12.8 Zn _1.1 , Cu _85.9 Ag _12.8 Cr _1.3 , The decrease in reflectance of Cu _85.3 Ag _12.8 Ni _1.2 is as small as 5.96%, 2.23%, 5.05%, and 3.28%, respectively. In Table 2, higher reflectivity (over 90%) is obtained as the third element type X in the case of Al, Zn, and Cr, and among them, Al and Zn are preferable because of high reflectivity. I understand. On the other hand, as verified by Al, when the third element species X is added to the CuAg alloy, if the content of the third element species X exceeds 10 at%, the reflectance change tends to be large. .

  The third element species X may be any number as long as it is one or more, and when two or more types of metal elements are used, the total sum may be set to 10 at% or less.

[Example 10]
In the same manner as in Example 9, a sputtering target having the composition described in Table 3 below was produced. Furthermore, the following experiment was conducted in order to investigate the oxidation resistance and corrosion resistance of the sputtering target and the sputtered film. That is, a sputtered film was provided on a glass substrate as in Example 9. Then, after measuring the reflectance of the sputtered film provided on a glass substrate in the same manner as in Example 9, concentration and held for 2 hours H ₂ S gas atmosphere 100 ppm. And the reflectance after holding | maintenance was measured by the method similar to Example 9 again. Incidentally, the light of 650 nm for reflectance measurement was incident from the substrate side. Table 3 shows the results obtained in the above experiment.

In Table 3, what is indicated as “immediately after the formation of the sputtered film” indicates the measurement result of the reflectance immediately after the sputtered film is formed on the glass substrate. In Table 3, what is indicated as “after exposure” indicates the measurement result of the reflectance after being kept in an H ₂ S gas atmosphere for 2 hours. In Table 3, what is indicated as “change rate” indicates the change rate of reflectance between “immediately after the formation of the sputtered film” and “after exposure”.

From the results shown in Table 3, when Cu is contained in Ag at 10 at% or less and the third element species X is contained at 5 at% or less, reflection occurs despite the extremely severe oxidation and corrosion test of H ₂ S gas exposure. It can be seen that many of the rate change rates can be controlled to a very small value of several percent. In addition, the content of 5 at% or less of the third element species X is smaller than the conventionally used addition amount. From this, it can be seen that even when the third element type X is 5 at% or less, the reflection layer can sufficiently exhibit the oxidation resistance improvement effect and the corrosion resistance improvement effect.

  The present invention can be suitably used in applications such as optical recording media for red semiconductor lasers such as DVD ± R and optical recording media for blue semiconductor lasers.

Although the invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention.
In addition, this application is based on the Japanese application (Japanese Patent Application No. 2005-131925) for which it applied on April 28, 2005, The whole is used by reference.

(A)-(c) is sectional drawing which shows typically the structure of the optical recording medium which concerns on embodiment of this invention. (A), (b) is sectional drawing which shows typically the structure of the optical recording medium which concerns on embodiment of this invention. (A) is a graph showing the wavelength distribution of the refractive index (n) of the main metal material, (b) is a graph showing the wavelength distribution of the extinction coefficient (k) of the main metal material, c) is a graph showing the wavelength distribution of reflectance in air calculated for a reflective layer (thickness 120 nm) formed using a main metal material. (A)-(d) are all the figures which show the recording characteristic of the optical recording medium of Example 1, Example 2, and Comparative Example 1, and the measurement result of "practical" light resistance, (a). A graph showing the measurement result of the recording power margin, (b) is a graph showing the measurement result of the asymmetry margin, (c) is a graph showing the measurement result of the bottom jitter before and after the light resistance test, and (d) is a light resistance of PI max. It is a graph showing the measurement result before and after a test. (A)-(d) is a figure which shows the recording characteristic of the optical recording medium of Example 3 and Comparative Example 2, and the measurement result of "practical" light resistance, (a) is a recording power margin. (B) is a graph showing the measurement results of the asymmetry margin, (c) is a graph showing the measurement results before and after the bottom jitter light resistance test, and (d) is a measurement before and after the PI max light resistance test. It is a graph showing a result. (A), (b) is a figure which shows the measurement result of the recording characteristic of the optical recording medium of Example 4 and Comparative Example 3, (a) is a graph showing the measurement result of the recording power margin, (b) ) Is a graph showing the measurement result of the asymmetry margin. (A)-(d) is a figure which shows the measurement result of the recording characteristic of the optical recording medium of the comparative example 4, and a "practical" light resistance, (a) represents the measurement result of a recording power margin. (B) is a graph showing the measurement results of the asymmetry margin, (c) is a graph showing the measurement results before and after the bottom jitter light resistance test, and (d) is a graph showing the measurement results before and after the PI max light resistance test. It is. It is a graph showing the wavelength distribution of the reflectance of the metal reflective layer single layer used by each Example and a comparative example. (A)-(d) is a graph showing the value of dR / dλ of the metal reflective layer single layer used in each example and comparative example. (A) Cu reflective layer single layer (Example 1), (b) Au reflective layer single layer (Example 2), (c) Ag reflective layer single layer (Comparative Example 1), (d) Al The values of the single reflective layer (Example 5) are shown. The measurement results of the reflectivity of CuAg _12.8 and CuAg _12.9 Pd _0.7 obtained in Example 6 is a graph showing Ag, Au, together with the measurement results of Cu obtained in Example 5. (A), (b) are each a graph showing the calculation result of dR / d [lambda] of CuAg _12.8 and CuAg _12.9 Pd _0.7. It is a graph which shows the relationship between content of Ag obtained in Example 6, and the maximum value of dR / d (lambda) in the wavelength range of 300-500 nm. It is a graph which shows the relationship between the value of X (Ag content) and bottom jitter value in Cu _(100-X) Ag _X , when it is assumed that light resistance has a substantially linear correlation with Ag content. . (A), (b) is a graph which shows the result of the light resistance test in Examples 6-8, (a) is a graph showing the relationship between a xenon irradiation time and a jitter value, FIG.14 (b). Is a graph showing the relationship between xenon irradiation time and PI error. (A), (b) is a graph which shows the result of the storage stability test in high temperature, high humidity in Examples 6-8, (a) is a graph showing the time change of a jitter value, b) is a graph showing a time change of the PI error.

Explanation of symbols

11, 12, 22 Bonding disk 21 Dummy disk 100, 200, 300, 400, 500 Optical recording medium 101, 201, 401, 501 Substrate (1)
102, 402, 502 Recording layer (1)
103, 202, 403, 503 Reflective layer (1)
104,203 Protective coat layer (1)
105, 204, 407, 504 Adhesive layer 106, 205 Protective coating layer (2)
107, 206, 406, 506 Reflective layer (2)
108,405,505 Recording layer (2)
109, 208, 408, 507 Substrate (2)
110, 111, 210, 310, 410, 510 Laser beam 207, 303 Recording layer 301 Substrate 302 Reflective layer 304, 508 Barrier layer 305, 404, 504 Transparent resin layer (intermediate layer), adhesive layer (intermediate layer)

Claims (12)

On a substrate having concentric or spiral grooves, at least a recording layer made of an organic dye and a reflective layer containing a metal, and the shortest mark length is less than 0.4 μm, or 35.0 m / s or more In an optical recording medium for recording at a recording linear velocity of
The track pitch of the guide groove on the substrate is 0.8 μm or less, the groove width is 0.4 μm or less, and the recording layer thickness in the groove is 70 nm or less,
The organic dye single layer forming the recording layer has a dye retention of 70% or less in the Wool scale 5 (light resistance test) under the light irradiation conditions shown in ISO-105-B02, as defined below.
An optical recording medium, wherein a differential value dR / dλ (% / nm) of reflectance R with respect to wavelength λ in the air of the reflective layer is 3 or less in a wavelength region of 300 nm or more and 500 nm or less.
[Dye retention]
The ratio of absorbance before and after the light resistance test at the maximum absorption wavelength of the coating film of the organic dye single layer forming the recording layer in the wavelength region of 300 to 800 nm, that is, {(absorbance after test) / (absorbance before test)} X100 (%) is defined as a dye retention rate. 2. The reflective layer contains at least one element selected from Cu, Au, and Al, and a total ratio of the elements is 50 at% or more in the reflective layer. The optical recording medium described. The optical recording medium according to claim 1, wherein the reflectance of the reflective layer in air at a wavelength of 300 nm to 500 nm is 20% or more and 70% or less. 4. The recording layer according to claim 1, wherein the recording layer contains at least an azo metal chelate dye composed of an azo compound represented by the following general formula (1) and a metal ion of Zn as an organic dye. The optical recording medium according to one item.

(In general formula (1),
R ¹ represents a hydrogen atom or an ester group represented by CO ₂ R ³ (wherein R ³ represents a linear or branched alkyl group or a cycloalkyl group).
R ² represents a linear or branched alkyl group.
At least one of X ¹ and X ² represents an NHSO ₂ Y group (where Y represents a linear or branched alkyl group substituted with at least two fluorine atoms), and the rest Represents a hydrogen atom.
R ⁴ and R ⁵ each independently represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkoxy group.
R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.
Note that H ⁺ is eliminated from the NHSO ₂ Y group to become an NSO ₂ Y ⁻ (negative) group, and the azo compound represented by the general formula (1) forms a coordinate bond with the metal ion. ) The optical recording medium according to any one of claims 1 to 4, wherein the recording layer contains at least a cyanine dye represented by the following general formula (2) as an organic dye.

(In general formula (2),
Ring A and ring B each independently represent an optionally substituted benzene ring or naphthalene ring.
R ¹⁰ and R ¹¹ each independently represents an alkyl group having 1 to 5 carbon atoms which may have a substituent.
R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ each independently represents an alkyl group having 1 to 5 carbon atoms which may have a substituent.
R ¹⁶ represents a hydrogen atom, a halogen atom, a cyano group, or an alkyl group having 1 to 5 carbon atoms which may have a substituent.
Q ⁻ represents a counter anion. ) 3d transition element excluding Zn and at least one azo compound selected from the group consisting of compounds represented by the following general formulas (3), (4), (5) and (6) as the organic dye as the organic dye The optical recording medium according to claim 4, comprising at least an azo metal chelate dye composed of the above metal ions.

(In the general formulas (3) and (5), R ²⁰ has a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms which may have a substituent, or a substituent. And an ester group having a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms which may be used.
In the general formulas (4) and (6), R ¹⁷ represents an alkyl group having 1 to 6 carbon atoms which may have a substituent.
R ²¹ to R ^{27 in} the general formulas (3) and (4) and R ¹⁸ and R ¹⁹ in the general formulas (5) and (6) each independently have a hydrogen atom or a substituent. It represents a straight, branched or cyclic alkyl group having 1 to 6 carbon atoms. R ¹⁸ and R ¹⁹ may combine with each other to form a ring.
In general formulas (3), (4), (5), and (6), at least one of X ¹ and X ² is an NHSO ₂ Y group (where Y is substituted with at least two fluorine atoms) Represents a straight-chain or branched alkyl group, and the remainder represents a hydrogen atom.
The azo compound represented by the general formulas (3), (4), (5) and (6) is obtained by removing H ⁺ from the NHSO ₂ Y group to form an NSO ₂ Y ⁻ (negative) group. Forms a coordination bond with a metal ion. ) 3d transition element excluding Zn and at least one azo compound selected from the group consisting of compounds represented by the following general formulas (3), (4), (5) and (6) as the organic dye as the organic dye 6. The optical recording medium according to claim 5, wherein the optical recording medium contains at least an azo metal chelate dye composed of the above metal ions.

(In the general formulas (3) and (5), R ²⁰ has a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms which may have a substituent, or a substituent. And an ester group having a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms which may be used.
In the general formulas (4) and (6), R ¹⁷ represents an alkyl group having 1 to 6 carbon atoms which may have a substituent.
R ²¹ to R ^{27 in} the general formulas (3) and (4) and R ¹⁸ and R ¹⁹ in the general formulas (5) and (6) each independently have a hydrogen atom or a substituent. It represents a straight, branched or cyclic alkyl group having 1 to 6 carbon atoms. R ¹⁸ and R ¹⁹ may combine with each other to form a ring.
In general formulas (3), (4), (5), and (6), at least one of X ¹ and X ² is an NHSO ₂ Y group (where Y is substituted with at least two fluorine atoms) Represents a straight-chain or branched alkyl group, and the remainder represents a hydrogen atom.
The azo compound represented by the general formulas (3), (4), (5) and (6) is obtained by removing H ⁺ from the NHSO ₂ Y group to form an NSO ₂ Y ⁻ (negative) group. Forms a coordination bond with a metal ion. ) On a substrate having concentric or spiral grooves, a recording layer containing at least an organic dye and a reflective layer containing a metal are used, and the shortest mark length is less than 0.4 μm, or 35.0 m / s In an optical recording medium for recording at the above recording linear velocity,
An optical recording medium, wherein the recording layer contains at least an azo metal chelate dye comprising an azo compound represented by the following general formula (1) and a metal ion of Zn as an organic dye.

(In general formula (1),
R ¹ represents a hydrogen atom or an ester group represented by CO ₂ R ³ (wherein R ³ represents a linear or branched alkyl group or a cycloalkyl group).
R ² represents a linear or branched alkyl group.
At least one of X ¹ and X ² represents an NHSO ₂ Y group (where Y represents a linear or branched alkyl group substituted with at least two fluorine atoms), and the rest Represents a hydrogen atom.
R ⁴ and R ⁵ each independently represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkoxy group.
R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.
Note that H ⁺ is eliminated from the NHSO ₂ Y group to become an NSO ₂ Y ⁻ (negative) group, and the azo compound represented by the general formula (1) forms a coordinate bond with the metal ion. ) The optical recording medium according to claim 1, wherein the reflective layer contains at least a material represented by the following composition (A).
[Composition (A)]
50at% ≦ Cu ≦ 97at%
3at% ≦ Ag ≦ 50at%
0.05at% ≦ X ≦ 10at%
(Here, X represents at least one element selected from the group consisting of Zn, Al, Pd, In, Sn, Cr, and Ni, provided that the total amount of Cu, Ag, and X is 100 at% or less. .) A sputtering target used for producing the reflective layer of an optical recording medium having a recording layer containing at least an organic dye and a reflective layer containing a metal on a substrate having concentric or spiral grooves,
A sputtering target comprising at least a material represented by the following composition B.
[Composition (B)]
50at% ≦ Cu ≦ 97at%
3at% ≦ Ag ≦ 50at%
0.05at% ≦ X ≦ 10at%
(Here, X represents at least one element selected from the group consisting of Zn, Al, Pd, In, Sn, Cr, and Ni, provided that the total amount of Cu, Ag, and X is 100 at% or less. .) The sputtering target according to claim 10, wherein an azo metal chelate dye comprising an azo compound represented by the following general formula (1) and Ni, Zn metal ions is used as the organic dye.

(In general formula (1),
R ¹ represents a hydrogen atom or an ester group represented by CO ₂ R ³ (wherein R ³ represents a linear or branched alkyl group or a cycloalkyl group).
R ² represents a linear or branched alkyl group.
At least one of X ¹ and X ² represents an NHSO ₂ Y group (where Y represents a linear or branched alkyl group substituted with at least two fluorine atoms), and the rest Represents a hydrogen atom.
R ⁴ and R ⁵ each independently represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkoxy group.
R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.
Note that H ⁺ is eliminated from the NHSO ₂ Y group to become an NSO ₂ Y ⁻ (negative) group, and the azo compound represented by the general formula (1) forms a coordinate bond with the metal ion. ) On a substrate having concentric or spiral grooves, a recording layer containing at least an organic dye and a reflective layer containing a metal are used, and the shortest mark length is less than 0.4 μm, or 35.0 m / s An azo metal chelate dye used as the organic dye of an optical recording medium for recording at the above recording linear velocity,
An azo metal chelate dye comprising an azo compound represented by the following general formula (1) and a metal ion of Zn.

(In general formula (1),
R ¹ represents a hydrogen atom or an ester group represented by CO ₂ R ³ (wherein R ³ represents a linear or branched alkyl group or a cycloalkyl group).
R ² represents a linear or branched alkyl group.
At least one of X ¹ and X ² represents an NHSO ₂ Y group (where Y represents a linear or branched alkyl group substituted with at least two fluorine atoms), and the rest Represents a hydrogen atom.
R ⁴ and R ⁵ each independently represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkoxy group.
R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.
Note that H ⁺ is eliminated from the NHSO ₂ Y group to become an NSO ₂ Y ⁻ (negative) group, and the azo compound represented by the general formula (1) forms a coordinate bond with the metal ion. )

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