JP2006313612A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium capable of obtaining satisfactory recording and reproducing characteristics in use of high speed recording. <P>SOLUTION: In the optical recording medium having a reflection layer, a recording layer containing a dye and a transparent resin layer in this order on a substrate, a barrier layer is provided between the recording layer and the resin layer, a material used for the barrier layer has ≥70 W/(m K) heat conductivity M at 300 K as bulk and the barrier layer has <5 nm film thickness t. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording medium, and more particularly to an optical recording medium capable of obtaining good recording / reproduction characteristics at high speed recording.

  In recent years, various optical recording media such as DVD-RW and DVD-R are widely recognized as external storage devices in information processing apparatuses such as computers because they store large amounts of information and are easily accessible at random. . For example, a typical DVD-R having an organic dye-containing recording layer has a dye recording layer and a reflective layer in this order on a transparent disk substrate, and a laminate having a protective layer covering these recording layers and the reflective layer. The structure is such that recording and reproduction are performed with a laser beam through the substrate. In order to further increase the recording capacity of these optical recording media, a multilayer optical recording medium in which a plurality of recording layers are provided on one medium has been developed. For example, a disk-shaped transparent first substrate is developed. On top of this, a two-layer type optical recording medium having two dye recording layers with an intermediate layer made of an ultraviolet curable resin interposed therebetween has been reported.

  Such a two-layer optical recording medium is formed by forming two disk substrates on which a 2P (Photo Polymerization) method using a transparent stamper and a recording layer and a reflective layer are laminated, and pasting them through a photo-curable resin layer. The method is known. In either case, a reflective layer and a recording layer containing a dye (hereinafter, also referred to as a recording layer (1) or a second recording layer) are formed on a substrate that is deepest in the laser light incident surface. They are stacked in order.

  Among them, in the method of attaching two disk substrates on which a recording layer and a reflective layer are laminated, the recording layer and the reflective layer are laminated in this order on a substrate on which a guide groove for a recording track is formed (hereinafter referred to as such). Such a laminated body or laminated structure may be referred to as a “regular laminated body” or a “regular laminated structure” when the transparent resin layer in which the grooves are formed is viewed on the substrate.) The first disk substrate and the above A second disk in which a reflective layer and a recording layer are laminated in this order on a similar substrate (hereinafter, such a laminated body or laminated structure may be referred to as “reverse laminated body” or “reverse laminated structure”). A substrate is formed, a photocurable resin is applied to each disk substrate, and then the coated surfaces are put together to cure the photocurable resin. Optical information is recorded / reproduced on the two recording layers using recording / reproducing light incident from the first disk substrate side. Such a method of adhering two disc substrates does not require a step of transferring the uneven shape of the transparent stamper as in the 2P method, and is considered to be excellent in productivity and cost reduction.

  In the reverse laminated structure, it is known to provide a layer called “barrier layer” between the recording layer and the photocurable resin (see Patent Documents 1 and 2).

JP 2000-31384 A (paragraphs [0052] and [0053], Example 2) JP 2002-373451 A (paragraphs [0034] and [0035], Examples)

  In the first place, in an optical recording medium provided with a recording layer containing an organic dye, there is a problem that it is desired to further suppress the occurrence of crosstalk in high-speed recording applications. According to the study by the present inventors, this is mainly because the thermal conductivity of the organic dye is much smaller than the thermal conductivity of the recording layer of other known inorganic recording media (for example, DVD-RW). This is due to

  That is, in a recording layer containing an organic dye, the dye that has absorbed the condensed recording laser beam is usually decomposed to change the optical constant, or the thickness of the portion decreases, the pressure increases, and the temperature increases. The recording portion is formed, for example, when the periphery of the recording layer exposed to is changed. In this case, since heat diffusion, particularly heat radiation in the in-plane direction of the recording layer is unlikely to occur, the recording portion tends to expand to the adjacent track portion, and crosstalk tends to increase when recording is performed on a plurality of tracks. . These tendencies may cause a phenomenon that it is difficult to obtain good jitter.

  Furthermore, since the recording pulse is shortened in the case of high-speed recording, it is necessary to decompose the dye using a recording laser beam having a higher power than in the case of low-speed recording. As a result, since the recording layer is exposed to a higher temperature than in the case of low speed recording, the increase in crosstalk tends to be remarkable.

  The occurrence of such crosstalk may also be seen in the above-described two-layer optical recording medium by the 2P method. In particular, the two-layer optical recording formed by a method in which two disk substrates are attached. In the medium, it is noticeable in a recording layer (hereinafter sometimes referred to as “second recording layer”) located on the back side from the incident surface of the recording / reproducing light. As described above, the second recording layer of the two-layer optical recording medium formed by the method of adhering two disc substrates is an inverse laminate in which a reflective layer and a recording layer are laminated on a substrate. Is provided. In such a reverse laminate, when optical information is recorded in the inter-groove portion of the substrate, it is necessary to increase the thickness of the recording layer in the inter-groove portion in order to ensure the recording modulation degree. In this case, since the adjacent track of the recording portion is a groove portion of the substrate, the recording layer thickness is likely to be thicker than that between the grooves. For this reason, as the recording layer film thickness of the groove portion increases, the recording mark spreads laterally and crosstalk tends to increase. Such a difference in recording film thickness between the groove and the groove is likely to occur when an organic dye solution is applied.

  Further, the second disk substrate provided on the back side from the recording / reproducing light incident surface in the two-layer type optical recording medium has a guide groove shallower than the conventional one in order to ensure the reflectance of the recording / reproducing light. Is set. For this reason, the physical barrier effect of the guide groove is reduced, excessive deformation due to flow deformation of the resin of the substrate during recording is likely to occur, and crosstalk is likely to increase.

The present invention has been made to solve such problems.
That is, an object of the present invention is to provide an optical recording medium including an inversely laminated structure that can obtain good recording / reproducing characteristics in high-speed recording applications.
Furthermore, another object of the present invention is to provide an optical recording medium having a second recording layer that is particularly excellent in high-speed recording in a two-layer optical recording medium.

As a result of intensive studies, the inventors of the present invention have formed a barrier layer provided between the recording layer and the transparent resin layer with a material having a high thermal conductivity as a bulk and making the film thickness very thin. The present inventors have found that the above problems can be effectively solved.
In addition, the second recording layer of the two-layer optical recording medium contains a specific dye that is particularly excellent for high-speed recording, thereby solving various problems required for the second recording layer. Further, the inventors have found that sufficient light resistance can be maintained, and have reached the present invention.

  That is, the gist of the present invention is an optical recording medium having a reflective layer, a recording layer containing a dye, and a transparent resin layer in this order on a substrate, and a barrier layer between the recording layer and the resin layer. The thermal conductivity M at 300 K as a bulk of the material used for the barrier layer is 70 W / m · K or more, and the thickness t of the barrier layer is smaller than 5 nm. It exists in a medium (Claim 1).

（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、少なくとも何れか一方は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。） Furthermore, another gist of the present invention is that a first reflective layer, a first recording layer containing a dye, a transparent resin layer, a second reflective layer containing a dye, and a second recording are formed on a first substrate. An optical recording medium having a layer and a second substrate in this order, wherein the first recording layer (second recording layer) is represented by the following general formula (1) as a dye: An optical recording medium comprising at least a metal-containing azo dye comprising a compound and a Zn metal ion (claim 7).

(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. )

  In another aspect of the present invention described above, the transparent resin layer may be an intermediate layer having guide grooves in a two-layer optical recording medium in which guide grooves are formed in the intermediate layer by the 2P method. Hereinafter also referred to as “2P layer”).

  Thus, according to the present invention, it is possible to obtain an optical recording medium capable of obtaining good recording / reproducing characteristics in high-density and high-speed recording applications.

  Hereinafter, the best mode for carrying out the present invention (abbreviated as “embodiment of the invention” as appropriate) will be described. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

[Basic concept 1 of the present invention]
The basic structure of the first optical recording medium of the present invention includes a reflective layer, a recording layer containing a dye, and a transparent resin layer in this order on a substrate. Furthermore, a barrier layer is provided between the recording layer and the resin layer as necessary.

  One feature of the present invention is that a material having high thermal conductivity is used for the barrier layer. By using a material having a high thermal conductivity for the barrier layer in this way, it is possible to dissipate heat during recording of the recording layer of the reverse laminate, suppress excessive deformation during recording, and reduce crosstalk. It becomes possible.

  Furthermore, the present invention has another feature in that the thickness of the barrier layer is made thinner than 5 nm. By reducing the film thickness in this way, even if a metal film or alloy film having a large extinction coefficient is used as a barrier layer, it is possible to suppress the attenuation of the recording light, and to reduce the recording sensitivity of the reverse stacking configuration, thereby achieving good recording It becomes possible to obtain characteristics. In addition, as will be described later, it is considered possible to form a good recording edge portion.

  The effect of reducing the crosstalk in the present invention is that the groove shape of the substrate used in the reverse laminated body, in particular, the groove depth is about 1/5 or less of the groove depth of the normal forward lamination or the second disk substrate. It is remarkably demonstrated. That is, the effects of the present invention are remarkably exhibited when the grooves of the substrate of the reverse laminated body are provided shallow in order to ensure the disk reflectivity and suppress the decrease in recording sensitivity.

  This is because when the groove depth is shallow, it becomes difficult to obtain a physical barrier due to the groove wall of the substrate, that is, a barrier effect of mass transfer such as dye or a resin of the substrate that has flowed during recording. This is because there is a problem that the crosstalk becomes very large due to excessive deformation of the recording portion. Therefore, it is preferable that the present invention is applied to a reverse laminated body using a substrate having a shallower groove than the conventional one.

  The relationship between the thermal conductivity of the barrier layer and the recording characteristics is supported by FIG. 2 of [Experimental Example 1] described later. Here, jitter when a plurality of tracks are recorded and signals recorded on adjacent tracks are reproduced is referred to as MT (%). In addition, jitter that can be reproduced by recording a portion recorded in only one track in a state where there is no recording in an adjacent track is referred to as ST (%). MT (%) includes the influence of crosstalk, whereas ST (%) does not include the influence of crosstalk.

  Δjitter is a difference value between the MT (%) and the ST (%), and the larger the value, the greater the crosstalk. The value of Δjitter is preferably 2% or less. If Δjitter exceeds 2%, for example, even if ST (%) is as good as 7%, MT (%) exceeds 9%, which is not preferable.

  When FIG. 2 is seen based on the above, in an Example, it turns out that thermal conductivity is less than 2% at 70 W / m * K or more, and a favorable characteristic is acquired.

  On the other hand, as can be seen from Table 3 of [Experimental Example 2] described later, it can be seen that it is difficult to improve jitter at a barrier layer with a high thermal conductivity at a boundary of 5 nm. This is considered to be one of the causes that the recording light intensity is attenuated and the recording sensitivity is deteriorated as the film thickness is increased. It is also conceivable that a change in film morphology due to an increase in film thickness is related to deterioration. The film morphology can be adjusted to some extent by the film formation conditions of the sputtering, the film composition, and the like.

  Furthermore, in the optical recording medium of the present invention, in the above-described basic configuration, the second reflective layer, the second recording layer, and the transparent resin layer on the side opposite to the reverse laminate side of the transparent resin layer in contact with the reverse laminate are transparent. By further providing a substrate in order, it can be developed into a multilayer optical recording medium.

[First Embodiment]
FIG. 1A is a cross-sectional view schematically showing a configuration of an optical recording medium according to the first embodiment of the present invention. FIG. 1A shows a disk substrate (reverse laminate 11) in which a reflective layer and a recording layer are laminated on a transparent substrate, and a disk substrate (normal laminate 12) in which a recording layer and a reflective layer are sequentially laminated on a transparent substrate. ) Is shown.

  As shown in FIG. 1A, an optical recording medium 100 includes a disc-shaped light transmissive substrate (1) 101 in which grooves and lands or prepits are formed as an inverse laminate 11, and the substrate (1). 101 includes a reflection layer (1) 102 provided on the incident surface side of the laser beam 110, a recording layer (1) 103 containing a dye, and a barrier layer 104. Further, as the regular laminate 12, a disc-shaped light-transmitting substrate (2) 109 in which grooves and lands or prepits are formed, and a recording layer (2) 108 containing a dye provided on the substrate (2) 109. And a translucent reflective layer (2) 107 for distributing the power of the laser beam 110 incident from the substrate (2) 109 side, and a protective coating layer 106 provided on the reflective layer (2) 107. The reverse laminate 11 and the regular laminate 12 are laminated via a transparent resin layer 105 so that the barrier layer 104 and the protective coat layer 106 face each other, and the two-layer optical recording medium 100 is formed. It is composed. In the recording layer (1) 103 and the recording layer (2) 108, optical information is recorded / reproduced by the laser light 110 incident from the substrate (2) 109 side of the positive laminate 12.

[Reverse laminate]
Next, each layer of the reverse laminate 11 will be described. As described above, the inverse laminate 11 includes the substrate (1) 101, the reflective layer (1) 102, the recording layer (1) 103, and the barrier layer 104 (hereinafter referred to as these layers) laminated on the substrate (1) 101. The reflective layer (1) 102, the recording layer (1) 103, and the barrier layer 104 may be collectively referred to as “L1 layer”).

<Board (1)>
It is desirable that the material constituting the substrate (1) 101 is light transmissive and has excellent optical properties such as a low birefringence. Moreover, it is desirable that the moldability is excellent, such as easy injection molding. Furthermore, it is desirable that the hygroscopicity is small. Furthermore, it is desirable to provide shape stability so that the optical recording medium 100 has a certain degree of rigidity. Examples of such materials include, but are not limited to, acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and glass. It is done. Moreover, what provided the resin layer which consists of radiation curable resins, such as photocurable resin, on base | substrates, such as glass, can be used. Among these, polycarbonate is preferable from the viewpoints of high productivity such as optical characteristics and moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoints of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.

  Further, since the substrate (1) 101 does not necessarily need to be light transmissive, a backing made of an appropriate material can be provided in order to increase mechanical stability and increase rigidity. Examples of such a material include an Al alloy substrate such as an Al—Mg alloy containing Al as a main component; an Mg alloy substrate such as an Mg—Zn alloy containing Mg as a main component; silicon, titanium, ceramics, paper, etc. A substrate or a combination thereof may be mentioned.

  The groove depth of the guide groove portion of the substrate (1) 101 constituting the reverse laminated body 11 is usually λ / 100 or more, preferably 2λ / 100 or more, more preferably 2.2λ / 100 or more, where λ is the recording / reproducing wavelength. It is. For example, when the wavelength of recording / reproducing light (recording / reproducing wavelength) is λ = 660 nm, the groove depth of the substrate (1) 101 is usually 6.6 nm or more, preferably 13 nm or more, more preferably 14.5 nm or more. .

  Moreover, it is preferable that the upper limit of the groove depth of the substrate (1) 101 in the reverse laminated body 11 is 110 nm or less. In particular, in the case of the optical recording medium 100 of the present embodiment, the light amount and the reflected light amount of the laser light 110 incident on the recording layer (1) 103 via the substrate (2) 109 and the transparent resin layer 105 are the recording layer (2). Since it is attenuated by 108 and the reflective layer (2) 107 and the reflectance becomes low, 7λ / 100 or less is a preferable upper limit of the groove depth. For example, when the recording / reproducing wavelength is λ = 660 nm, the groove depth of the substrate (1) 101 is preferably 46.2 nm or less. More preferably, it is 6λ / 100 or less.

  As described above, the groove depth of the substrate (1) in the reverse laminate 11 is preferably shallower than the groove depth of the substrate (2) in the configuration of the positive laminate 12 described later. The ratio of the substrate (2) to the groove depth is usually 1/3 or less, preferably 1/4 or less, more preferably 1/5 or less.

  The groove width of the substrate (1) 101 in the reverse laminated body 11 is usually T / 10 or more, preferably 2T / 10 or more, more preferably 3T / 10 or more, where T is the track pitch. However, it is usually 8T / 10 or less, preferably 7T / 10 or less, more preferably 6T / 10 or less. If the groove width of the substrate (1) 101 is within this range, tracking can be performed satisfactorily and sufficient reflectance can be obtained. For example, when the track pitch is 740 nm, the groove width of the substrate (1) 101 is usually 74 nm or more, preferably 148 nm or more, and more preferably 222 nm or more. Further, the upper limit of the substrate (1) 101 is usually 592 nm or less, more preferably 518 nm or less, and still more preferably 444 nm or less. In this specification, the “groove width” of the substrate refers to the width of the groove at half the maximum depth of the groove, that is, the half-value width.

  The substrate (1) 101 is preferably thick to some extent, and the thickness of the substrate (1) 101 is usually preferably 0.3 mm or more. However, it is usually 3 mm or less, preferably 1.5 mm or less.

<Reflective layer (1)>
The material constituting the reflective layer (1) 102 of the reverse laminate 11 is not particularly limited. For example, Au, Al, Ag, Cu, Ti, Ni, Pt, Ta, Pd, Mg, Se, Hf, V Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, rare earth metals and other metals and metalloids Any one of them can be used alone, or any two or more of them can be used as an alloy. Among these, Au, Al, and Ag are preferable, and a metal material containing 50% or more of Ag is particularly preferable from the viewpoint of low cost and high reflectance.

  Among them, the reflective layer (1) 102 is an alloy containing Ag as a main component and containing at least one element selected from the group consisting of Ti, Zn, Cu, Pd, Au, and rare earth metals in an amount of 0.1 to 15 atomic%. It is preferable that When two or more elements of Ti, Bi, Zn, Cu, Pd, Au, and rare earth metals are included, each content may be 0.1 to 15 atomic%, but the total content thereof is It is preferable that it is 0.1-15 atomic%.

  Further preferable alloy composition of the reflective layer (1) 102 contains 0.1 to 15 atomic% of at least one element selected from the group consisting of Ti, Bi, Zn, Cu, Pd, and Au with Ag as a main component. If necessary, it contains 0.1 to 15 atomic% of at least one rare earth element. Of the rare earth metals, neodymium is particularly preferred. Specifically, AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, AgBi, AgBiNd, and the like. The composition ratio of the alloy used in the present embodiment is in the above range.

  As the reflective layer (1) 102, a layer made only of Au is suitable because it has small crystal grains and is excellent in corrosion resistance. It is also possible to use a layer made of Si as the reflective layer (1) 102. Furthermore, it is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.

  Examples of the method for forming the reflective layer (1) 102 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.

  It is desirable that the reflective layer (1) 102 in the reverse laminate 11 has high reflectivity and high durability. In order to ensure a high reflectance, the thickness of the reflective layer (1) 102 is usually 30 nm or more, preferably 40 nm or more, and more preferably 50 nm or more. However, in order to shorten the tact time in production and reduce the cost, it is usually 400 nm or less, preferably 300 nm or less.

<Recording layer (1)>
The recording layer (1) 103 in the reverse laminated body 11 usually contains a dye having the same sensitivity as that of a recording layer used in a single-sided recording medium such as CD-R, DVD-R, DVD + R. Such a dye is preferably a dye compound having a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 to 900 nm and suitable for recording with a blue to near microwave laser. Among them, a near-infrared laser having a wavelength of about 770 to 830 nm (for example, 780 nm and 830 nm) that is usually used for a CD-R, and a red laser having a wavelength of about 620 to 690 nm for a DVD-R (for example, 635 nm, 660 nm, 680 nm), and a dye suitable for recording with a so-called blue laser or the like having a wavelength of 405 nm or 515 nm. It is also possible to use a phase change material.

  Although it does not specifically limit as a pigment | dye used for the recording layer (1) 103, Usually, an organic pigment | dye material is used. Organic dye materials include, for example, macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, azurenium And dyes containing metal, metal-containing azo dyes, metal-containing indoaniline dyes, and the like. Among these, metal-containing azo dyes are preferable because they are excellent in recording sensitivity and excellent in durability and light resistance. These dyes may be used alone or in combination of two or more.

The recording layer (1) 103 may contain other components in addition to the dye.
For example, the recording layer (1) 103 is a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-) as a singlet oxygen quencher to improve the stability and light resistance of the recording layer. (alpha-diketone etc.) etc., and recording sensitivity improvement agents, such as a metallic compound, may be contained for recording sensitivity improvement. Here, the metal compound refers to a compound in which a metal such as a transition metal is included 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. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.

Further, the recording layer (1) 103 can be used in combination with a binder, a leveling agent, an antifoaming agent, or the like, if 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.
However, in order to further improve the high-speed recording characteristics in the recording layer (1), a combination with a specific dye is preferable. This will be described later.

  The film forming method of the recording layer (1) 103 is not particularly limited, but generally a thin film forming method generally performed such as a vacuum deposition method, a sputtering method, a doctor blade method, a cast method, a spin coating method, a dipping method or the like. In view of mass productivity and cost, a wet film formation method such as a spin coating method is preferable. Moreover, the vacuum evaporation method is preferable from the point that a uniform recording layer is obtained.

  In the case of film formation by spin coating, the number of rotations is preferably 10 to 15000 rpm. After spin coating, a heat treatment is generally performed to remove the solvent. 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.

  The heat treatment for removing these solvents is usually performed at a temperature slightly lower than the boiling point of the solvent to be used from the viewpoint of removing the solvent and using simple equipment, and usually 60 ° C. or higher and 100 ° C. It is performed in the following range. The method for the heat treatment is not particularly limited. For example, after forming a film containing a dye-containing solution for forming the recording layer (1) 103 on the substrate (1) 101, a predetermined temperature is applied. And a predetermined time (usually 5 minutes or more, preferably 10 minutes or more, and usually within 30 minutes, preferably within 20 minutes). In addition, a method of heating the substrate (1) 101 by irradiating infrared rays or far infrared rays for a short time (for example, 5 seconds to 5 minutes) is also possible.

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 with an appropriate vacuum pump. After evacuating to about 10 ⁻⁵ Pa, the crucible is heated to evaporate the recording layer components and deposited on the substrate placed facing the crucible.

  The thickness of the recording layer (1) 103 of the reverse laminate 11 is usually 40 nm or more, preferably 50 nm or more, provided that it is usually 150 nm or less, preferably 100 nm or less. When the thickness of the recording layer (1) 103 is within this range, it is possible to suppress a decrease in sensitivity while ensuring a sufficient recording signal amplitude. Further, when the thickness of the recording layer (1) 103 is excessively large, the sensitivity may be lowered.

<Barrier layer>
The barrier layer 104 is provided on the reverse laminate 11. In general, the barrier layer 104 is provided between the recording layer (1) 103 and the transparent resin layer 105 in order to prevent components that ooze from the transparent resin layer 105 from contaminating or dissolving the recording layer (1) 103. It is done.

  In the present invention, in addition to the above object, the barrier layer 104 is used to secure heat dissipation in the recording layer 103 and suppress crosstalk in high-speed recording. For this reason, in the present invention, it is not a thick film conventionally known for alloys and dielectrics, but a very thin film using a material having high thermal conductivity as a bulk, so that extremely good characteristics are obtained. Is obtained.

  First, as described above, the thermal conductivity of the bulk is drastically improved with 70 W / m · K as a boundary. In FIG. 2 that summarizes a part of the data of Examples described later, when the thermal conductivity is further 90 W / m · K or more, Δjitter is less than 1%, except for Si and C, which are semiconductors, It can be seen that very good characteristics can be obtained. The upper limit of the thermal conductivity of the barrier layer 104 in the present invention is not necessarily limited, but 700 W / m · K is considered to be sufficient. It is considered that Si, C, etc., which are semiconductors alone, exhibit even better characteristics by increasing conductivity by alloying or using additives.

  On the other hand, when the film thickness of the barrier layer 104 exceeds 5 nm, as described above, remarkable deterioration of characteristics is observed. Therefore, the thickness of the barrier layer 104 is usually smaller than 5 nm, preferably 4 nm or less, more preferably 3.5 nm or less. On the other hand, the lower limit of the film thickness is usually 0.5 nm or more, more preferably 1 nm or more, and still more preferably 1.5 nm or more. As shown in FIG. 3, taking examples of Mo and Co from the elements listed in Table 2 in the “Examples” section below, the optimum values differ depending on the difference in thermal conductivity. It can be seen that Δjitter, ST (%), and MT (%) are stable and good values.

  Further, by forming such a thin film, unlike a glassy dielectric film having a low thermal conductivity, a thin film of a material having high ductility and malleability and having a high thermal conductivity is used for the barrier layer 104. It is possible to trace the change due to the decomposition of the image and to further improve the jitter.

  As the material of the barrier layer 104 of the present invention, Mg, Cr, Mn, Fe, Ni, Zn, Ru, Rh, Pd, In, Os, Ir, Pt, Mo, Al, W, Co, Cr, Cu, Ag Au simple substance or alloy is preferable. More preferably, a simple substance or an alloy of Cu, Al, Au, Co, Cr, Mo, Si, W, C, and Ag is used. More preferably, it is a simple metal element selected from the group consisting of Mo, W, Cu, Co, Cr, and Al, or an alloy containing these metal elements as a main component. Note that that a certain metal element is a “main component” means that the metal element occupies 50% by weight or more of the alloy composition. In particular, Mo, W, and Cu have extremely good characteristics, and Co and Cr have good sensitivity and good jitter in 4 × speed recording and 8 × speed recording. Note that Ag, Al, Si, and C may become a barrier layer 104 with good recording characteristics and weather resistance by alloying or improvement of a photocurable resin.

  According to the study by the present inventors, even when the barrier layer 104 is formed using the material exemplified above, it is possible to sufficiently obtain a barrier effect so that the recording layer does not dissolve in the photocurable resin in contact therewith. I understood. Further, it is considered that the barrier layer 104 should be a dense and smooth film. This is because when there is a density in the film, such as an island-like structure, a change in temperature and humidity such as in a high-temperature and high-humidity test may cause grain boundaries or increase in particle size, resulting in an increase in noise. This is because an increase in film defects can occur.

  The dense and smooth structure of the barrier layer 104 is considered to depend not only on its constituent components and composition but also on the conditions for forming the barrier layer 104. The barrier layer 104 is formed by a generally used film forming method such as a vacuum vapor deposition method or a sputtering method, but it is preferable to form the barrier layer 104 by a sputtering method. Here, taking the case of sputtering as an example, in order to obtain a dense and smooth barrier layer, the target is pre-sputtered before sputtering. Set the pre-sputtering time longer than usual and start the sputtering after removing the moisture adsorbed on the target and the surface oxide layer as much as possible, or set the argon pressure as low as possible. It is preferable to perform sputtering while adjusting the range. Further, since the barrier layer 104 of the present invention is a thin film, the surface state of the barrier layer 104 may affect recording. Therefore, recording characteristics can be improved by obtaining a dense and smooth film structure.

  In this specification, “thermal conductivity” refers to the heat at 300K described in Kittel, “Introduction to Solid State Physics, Volume 1”, 6th edition, Table 1, “Debye temperature and thermal conductivity” on page 117. The conductivity value shall be used. The thermal conductivity values of the main materials listed in the above table are shown in Table 1 below.

  Several methods have been reported to measure the thermal conductivity of an actual thin film, but the experiment requires a special device (for example, an optical alternating current method thin film thermal constant measurement device) or a special sample preparation method. To do. For this reason, these methods are not widely used in general, and measurement often requires excessive labor. Therefore, in the present invention, the above generalized bulk thermal conductivity is used.

  When the barrier layer 104 is composed of a plurality of compositions such as an alloy, the thermal conductivity obtained from the value obtained by multiplying the bulk thermal conductivity of each composition by the ratio of the composition as follows. Is defined as the thermal conductivity of the material used for the barrier layer 104 as a bulk. For example, the thermal conductivity of an alloy composed of 95 atomic% Al and 5 atomic% Cr includes the bulk thermal conductivity of Al (237 W / m · K) and the thermal bulk conductivity of Cr (94 W / m · K). K), 237 × 0.95 + 94 × 0.05 = 229.9 W / m · K. In this way, for example, the same calculation is performed for both the ternary system and the quaternary system.

  Note that the thermal conductivity of materials whose thermal conductivity is not described in the above-mentioned Kittel's "Introduction to Solid State Physics, Volume 1", 6th edition, Table 1, "Debye temperature and thermal conductivity" on page 117, is the WWW site on the Internet. (Http://www.a1s.co.jp/thermal/db/prop_met.htm etc.), “Science Chronology” (Maruzen), “Physics Dictionary” (Baifukan), etc. The value should be determined from a database that may be able to obtain the latest physical property values such as “rate table”.

  Incidentally, between the substrate (1) 101 and the recording layer (1) 103, between the substrate (2) 109 and the recording layer (2) 108, and between the recording layer (2) 108 and the reflective layer (2) 107. Alternatively, a layer made of the same material as the barrier layer 104 may be provided.

[Transparent resin layer]
Next, the transparent resin layer 105 provided in contact with the incident surface side of the laser beam 110 of the reverse laminate 11 will be described. The transparent resin layer 105 in the two-layer type optical recording medium 100 of the present embodiment usually has such light transmittance that the laser light 110 incident from the substrate (2) 109 side reaches the recording layer (1) 103. Consists of materials. The transparent resin layer 105 is preferably composed of a transparent resin having a glass transition temperature Tg of 150 ° C. or higher. The transparent resin layer 105 may be a single layer or a plurality of layers. By configuring the transparent resin layer using such a transparent resin, it is considered that the hardness of the transparent resin layer is increased and the jitter is improved.

  The resin constituting the transparent resin layer 105 has an elastic modulus at 30 ° C. of usually 1000 MPa or more, preferably 2000 MPa or more, more preferably 3000 MPa or more, and further preferably 4000 MPa or more. By forming the transparent resin layer 105 using a resin having an elastic modulus of 1000 MPa or more, a so-called confinement effect is further enhanced in recording / reproduction of the L1 layer (FIG. 1). However, the upper limit of the elastic modulus is usually 6000 MPa or less. By using a resin having an elastic modulus of 6000 MPa or less, for example, the transparent resin layer 105 can be formed by a solution method such as coating, which is industrially advantageous. Since the resin constituting the transparent resin layer 105 has an elastic modulus in the above range, it is possible to suppress excessive deformation extending to adjacent track portions in the recording of optical information of the recording layer (1) 103 of the reverse laminate 11. Can do. As a result, in the optical recording medium 100, crosstalk in high-speed recording of the L1 layer is reduced, and jitter is improved. Here, “transparent” in the transparent resin layer 105 means that the transparent resin layer 105 does not have a structure that scatters the laser light 110 incident on the optical recording medium 100.

  In order to stack a plurality of recording layers and focus each of them, it is desirable that there is a certain distance between the recording layers. Therefore, the film thickness of the transparent resin layer 105 is usually 5 μm or more, preferably 10 μm or more, although it depends on the focus servo mechanism.

  If this layer is too thick, for example, it may take time to adjust the focus servo to the recording layer (1) to which the focus servo is applied via the transparent resin layer 105. Furthermore, the moving distance of the objective lens may be long. Also, UV curing takes time and productivity may be inferior. From the above, the transparent resin layer 105 is generally preferably 100 μm or less.

Next, specific examples of the material constituting the transparent resin layer 105 will be described.
Examples of the material constituting the transparent resin layer 105 include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin (including a delayed curable type), and the like. The material which comprises the transparent resin layer 105 is suitably selected from these. A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent as necessary to prepare a coating solution, applying the solution, and drying (heating). The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiating with ultraviolet light. These materials may be used alone or in combination.

  As a method of forming the transparent resin layer 105, for example, a coating method such as a spin coating method or a casting method is used, and among these, the spin coating method is preferable. High-viscosity resin can also be applied and formed by screen printing or the like. As the ultraviolet curable resin, it is preferable to use a resin that is liquid at 20 ° C. to 40 ° C. This is because productivity can be improved because it can be applied without using a solvent. Moreover, it is preferable to adjust so that the viscosity of a coating liquid may be 20 mPa * s or more and 1000 mPa * s or less normally.

  Among the materials constituting the transparent resin layer 105, an ultraviolet curable resin is preferable because of its high transparency and a short curing time, which is advantageous in manufacturing. Examples of the ultraviolet curable resin include a radical ultraviolet curable resin and a cationic ultraviolet curable resin, both of which can be used.

  As the radical ultraviolet curable resin, a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used.

  As an ultraviolet curable compound, monofunctional (meth) acrylate and polyfunctional (meth) acrylate can be used as a polymerizable monomer component. Each of these may be used alone or in combination of two or more. In the present specification, “acrylate” and “methacrylate” are collectively referred to as “(meth) acrylate”.

  Examples of monofunctional (meth) acrylates include methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, and phenoxyethyl as substituents. , Nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone-modified tetrahydrofurfuryl, And (meth) acrylate having a group such as isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like.

  Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neo Di (meth) acrylates such as pentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, And di (meth) acrylate of tris (2-hydroxyethyl) isocyanurate.

  In addition, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol, and diol obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A Di (meth) acrylate, 3 mol or more of ethylene oxide or propylene oxide added to 1 mol of trimethylolpropane, triol di or tri (meth) acrylate, 4 mol or more of ethylene oxide or propylene per 1 mol of bisphenol A Di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol poly, obtained by adding oxide Meth) acrylate, ethylene oxide-modified phosphoric acid (meth) acrylate, ethylene oxide-modified alkylated phosphoric acid (meth) acrylate.

  Moreover, as what can be used together with these polymerizable monomers, polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate etc. are mentioned as a polymerizable oligomer.

  On the other hand, the photopolymerization initiator is preferably a molecular cleavage photopolymerization initiator or a hydrogen abstraction photopolymerization initiator.

  Examples of the molecular cleavage type photopolymerization initiator include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethyl. Amino-1- (4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like can be mentioned. Furthermore, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Propan-1-one and 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one may be used in combination.

  Examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4'-methyl-diphenyl sulfide, and the like.

  A sensitizer can be used in combination with these photopolymerization initiators. Examples of the sensitizer include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzylamine, and 4, 4′-bis (diethylamino) benzophenone and the like can be mentioned.

  On the other hand, examples of the cationic ultraviolet curable resin include an epoxy resin containing a cationic polymerization type photoinitiator. Examples of the epoxy resin include bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. As the epoxy resin, it is preferable to use one having a low content of free chlorine and chlorine ions. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.

  The ratio of the cationic polymerization type photoinitiator per 100 parts by weight of the cationic ultraviolet curable resin is usually 0.1 parts by weight or more, preferably 0.2 parts by weight or more, and usually 20 parts by weight or less, preferably 5 parts by weight. Part or less. A known photosensitizer can be used in combination in order to use the near-ultraviolet region and the visible region of the ultraviolet light source more effectively. Examples of the photosensitizer at this time include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, and acetophenone.

  In addition, for UV curable resins, as necessary, other additives such as thermal polymerization inhibitors, antioxidants represented by hindered phenols, hindered amines, phosphites, plasticizers, epoxy silanes, mercapto silanes, etc. Silane coupling agents represented by (meth) acrylic silane and the like can also be blended for the purpose of improving various properties. These are selected from those having excellent solubility in ultraviolet curable compounds and those that do not impair ultraviolet transparency.

  In the transparent resin layer 105 of the optical recording medium 100 of the present embodiment, specific means for obtaining a resin having a relatively high elastic modulus is not particularly limited, but the following methods are usually mentioned. For example, a method of increasing the composition of a monomer component having 2 or more, preferably 3 or more methacryloyl groups in the molecule as the above-mentioned ultraviolet curable resin; side chain such as polyester diol mixed with a linear polymer diol A method of increasing the composition of the containing polymer diol component; a method of increasing the intramolecular bond by lowering the side chain of the oligomer component whose main chain is a hard segment; polyisocyanate compound, amino resin, epoxy compound, silane compound, Examples thereof include a method of adding a predetermined amount of a crosslinking agent such as a metal chelate compound.

  In particular, in order to obtain a resin having sufficient hardness, a triol tri (meth) acrylate obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane tri (meth) acrylate and trimethylolpropane. ) Acrylate, pentaerythritol tri- or tetra (meth) acrylate, tetra-alcohol tri- or tetra (meth) acrylate obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of pentaerythritol, dipenta Penta or hexa (meth) acrylate of erythritol, pentaalcohol or hexa (meth) acrylate of hexaalcohol obtained by adding 6 mol or more of ethylene oxide or propylene oxide to 1 mol of dipentaerythritol, etc. Kan応 (meth) the use of acrylates, crosslinking density can be increased, further, it is also possible to increase the shrinkage preferred.

  Among them, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) ) Acrylate is more particularly preferred.

  In addition, norbornane dimethanol diacrylate, norbornane diethanol di (meth) acrylate, norbornane dimethanol obtained by adding 2 moles of ethylene oxide or propylene oxide to di (meth) acrylate, tricyclodecane dimethanol di ( Di (meth) acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to (meth) acrylate, tricyclodecane diethanol di (meth) acrylate, tricyclodecane dimethanol, pentacyclodecane dimethanol di (meth) Dioxide obtained by adding 2 moles of ethylene oxide or propylene oxide to acrylate, pentacycloopentadecane diethanol di (meth) acrylate, pentacyclopentadecane dimethanol Di (meth) acrylate of diol, di (meth) acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to pentacyclopentadecane diethanol, among others, tricyclodecane dimethanol di (meth) Acrylate, pentacyclopentadecane dimethanol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, bis (2-acryloyloxyethyl) hydroxyethyl isocyanurate, bis (2-acryloyloxypropyl) hydroxypropyl isocyanurate, Bis (2-acryloyloxybutyl) hydroxybutyl isocyanurate, bis (2-methacryloyloxyethyl) hydroxyethyl isocyanurate, bis (2-methacryloyloxyp) Pyr) hydroxypropyl isocyanurate, bis (2-methacryloyloxybutyl) hydroxybutyl isocyanurate, tris (2-acryloyloxyethyl) isocyanurate, tris (2-acryloyloxypropyl) isocyanurate, tris (2-acryloyloxybutyl) An acrylate having a rigid cyclic structure such as isocyanurate, tris (2-methacryloyloxyethyl) isocyanurate, tris (2-methacryloyloxypropyl) isocyanurate, tris (2-methacryloyloxybutyl) isocyanurate is also high. Preferred as an elastic modulus resin.

  Among these, tricyclodecane dimethanol di (meth) acrylate and tricyclopentadecane diethanol di (meth) acrylate are particularly preferable.

  Furthermore, it is preferable to appropriately combine an acrylic monomer having a high crosslinking density with an acrylic monomer having a rigid cyclic structure in the crosslinked structure.

  Of the ultraviolet curable resins, a cationic ultraviolet curable resin that has low light scattering and low viscosity and can be applied by spin coating is preferable. Furthermore, radical UV curing is possible because there are many types, the blending ratio and the degree of freedom of composition are large, and when the thickness of the transparent resin layer 105 is 10 μm or more, there is no need to consider curing inhibition by oxygen. It is preferable to use a functional resin.

[Positive laminate]
Next, each layer of the positive laminate 12 will be described. As described above, the positive laminate 12 includes the substrate (2) 109, the recording layer (2) 108 laminated on the substrate (2) 109, the reflective layer (2) 107, and the protective coating layer 106 (hereinafter referred to as these layers). The recording layer (2) 108, the reflective layer (2) 107, and the protective coating layer 106 are collectively referred to as “L0 layer”).

<Substrate (2)>
The substrate (2) 109 of the positive laminate 12 is made of the same material as the substrate (1) 101 of the reverse laminate 11. However, the substrate (2) 109 needs to be light transmissive. The groove width of the substrate (2) 109 is usually 2T / 10 or more, preferably 3T / 9 or more, where T is the track pitch. If it is this range, a sufficient reflectance can be secured. For example, when the track pitch is 740 nm, the groove width of the substrate (2) 109 is usually 148 nm or more, preferably 246 nm or more. However, the groove width of the substrate (2) 109 is usually 7T / 10 or less, preferably 6T / 10 or less. For example, when the track pitch is 740 nm, the groove width of the light-transmitting substrate (2) 109 is usually 518 nm or less, preferably 444 nm or less, because the groove shape transferability can be improved.

  The groove depth of the substrate (2) 109 is usually preferably λ / 10 or more when the recording / reproducing light wavelength is λ, because a sufficient reflectance can be secured. More preferably, it is λ / 8 or more, and further preferably λ / 6 or more. For example, when the wavelength of the recording / reproducing light (recording / reproducing wavelength) is λ = 660 nm, the groove depth of the substrate (2) 109 is usually 66 nm or more, preferably 82.5 nm or more, and more preferably 110 nm or more. However, the upper limit of the groove depth of the substrate (2) 109 is usually preferably 2λ / 5 or less because the transferability of the groove shape can be improved, and more preferably 2λ / 7 or less. For example, when the recording / reproducing wavelength is 660 nm, it is usually 264 nm or less, preferably 188.6 nm or less.

<Recording layer (2)>
The recording layer (2) 108 of the positive laminate 12 contains the same dye as the recording layer (1) 103 of the reverse laminate 11. The thickness of the recording layer (2) 108 of the positive laminate 12 is not particularly limited because the suitable film thickness varies depending on the recording method or the like, but is usually 20 nm or more, preferably 30 nm or more in order to obtain a sufficient degree of modulation. Especially preferably, it is 40 nm or more. However, since it is necessary to transmit light, it is usually 200 nm or less, preferably 180 nm or less, and more preferably 150 nm or less. The thickness of the recording layer (2) 108 indicates the thickness of the thick film portion (the thickness of the recording layer (2) 108 in the groove portion of the substrate (2) 109).

<Reflective layer (2)>
The reflective layer (2) 107 of the regular laminate 12 is made of the same material as the reflective layer (1) 102 of the reverse laminate 11. The reflective layer (2) 107 of the positive laminate 12 has a small absorption of the laser beam 110, which is a recording / reproducing light incident from the substrate (2) 109 side, and has a light transmittance of usually 40% or more. Therefore, it is necessary to have an appropriate light reflectance of 30% or more. For example, an appropriate transmittance can be provided by providing a thin metal with high reflectivity. Moreover, it is desirable that there is some degree of corrosion resistance. Furthermore, the recording layer (2) 108 positioned below the reflective layer (2) 107 is not affected by other components that ooze out from the upper layer (here, the transparent resin layer 105) of the reflective layer (2) 107. It is desirable to have sex.

  The thickness of the reflective layer (2) 107 is usually 50 nm or less, preferably 30 nm or less, more preferably 25 nm or less in order to ensure a light transmittance of 40% or more. In order to ensure an appropriate light reflectance of 30% or more, the thickness of the reflective layer (2) 107 is usually 3 nm or more, preferably 5 nm or more.

<Protective coat layer>
The protective coating layer 106 of the regular laminate 12 is provided on the transparent resin layer 105 side of the reflective layer (2) 107 for the purpose of preventing oxidation of the reflective layer (2) 107, and preventing dust or scratches. The material of the protective coat layer 106 is not particularly limited as long as it protects the reflective layer (2) 107. Examples of the material of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of the inorganic substance include dielectrics such as silicon oxide, silicon nitride, magnesium fluoride (MgF ₂ ), and tin (IV) oxide (SnO ₂ ). Especially, it is preferable to laminate | stack an ultraviolet curable resin layer. The thickness of the protective coating layer 106 is usually 1 μm or more, preferably 3 μm or more, and usually 100 μm or less, preferably 30 μm or less, more preferably 10 μm or less. If the thickness of the protective coat layer 106 is less than this range, curing failure due to oxygen may occur. On the other hand, if the thickness exceeds this range, the disc may be warped and a film thickness distribution is likely to occur. The protective coat layer 106 is not necessarily provided, and the transparent resin layer 105 may be directly formed on the reflective layer (2) 107.

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

[Second Embodiment]
FIG. 1B is a cross-sectional view schematically showing the configuration of the optical recording medium according to the second embodiment of the present invention. FIG. 1B shows a film surface incident type optical recording medium 200 in which recording / reproducing of optical information is performed by recording / reproducing light incident from the side opposite to the substrate side. As shown in FIG. 1B, the optical recording medium 200 includes a substrate 201, a reflective layer 202 provided on the substrate 201, a recording layer 203 laminated on the reflective layer 202, and a recording layer 203. A transparent resin layer 205 is further laminated on the incident surface side of the laser beam 210 on the reverse laminate including the barrier layer 204 provided to protect the laser beam. In the optical recording medium 200, information is recorded / reproduced by a laser beam 210 applied to the recording layer 203 from the transparent resin layer 205 side.

  The substrate 201 constituting the inverse laminate is formed using the same material as the substrate (1) 101 of the inverse laminate 11 in the optical recording medium 100 of the first embodiment. Similarly, the materials constituting the reflective layer 202, the recording layer 203, and the barrier layer 204 are the reflective layer (1) 102 and the recording layer (of the reverse laminate 11 in the optical recording medium 100 of the first embodiment, respectively). 1) The same materials as those described in 103 and the barrier layer 104 can be used. Further, the thickness of each layer is the same as the range described in the optical recording medium 100.

Further, the transparent resin layer 205 is configured using the same material as the transparent resin layer 105 in the optical recording medium 100 described above, and the elastic modulus and thickness of the transparent resin layer 205 are the same as those of the first embodiment. The same range as the transparent resin layer 105 in the recording medium 100 is adjusted.
In each of the above-described embodiments, any other layer may be provided between the layers as long as the function as the optical recording medium 100 is not impaired.

[Basic concept 2 of the present invention]
Next, a two-layer type optical recording medium that is a second optical recording medium of the present invention, particularly suitable for high-speed recording, will be described below with a focus on the configuration of the second recording layer.

  The two-layer type optical recording medium, which is the second optical recording medium of the present invention, is a first reflective layer containing a first reflective layer and a dye on a substrate (sometimes referred to as a “first substrate”). A recording layer and a transparent resin layer are provided in this order. On the transparent resin layer, a second reflection layer, a second recording layer, and a transparent substrate (this may be referred to as a “second substrate”). .) Are further provided in this order.

A specific example of the basic concept will be described with reference to FIGS. 1A and 5 as follows.
That is, the “substrate (1)” in FIGS. 1A and 5 corresponds to the “first substrate”.
Further, the “reflective layer (1)” in FIGS. 1A and 5 corresponds to the “first reflective layer”.
Similarly, the “recording layer (1)” in FIGS. 1A and 5 corresponds to the “first recording layer”.
Further, the “reflective layer (2)” in FIGS. 1A and 5 corresponds to the “second reflective layer”.
Similarly, the “recording layer (2)” in FIGS. 1A and 5 corresponds to the “second recording layer”.
The “substrate (2)” in FIGS. 1A and 5 corresponds to the “transparent substrate”, that is, the “second substrate”.

  Then, the first recording layer (second recording layer) is a metal-containing azo dye (hereinafter referred to as “formula (2)” composed of an azo compound represented by the following general formula (1) and a Zn metal ion as a dye. At least a metal-containing azo dye according to 1).

(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 4 carbon atoms such as ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, sec-butyl, etc .; cyclopropyl A cycloalkyl group having 3 to 8 carbon atoms, such as a group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and 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 6 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 .

  The metal-containing azo dye according to the above formula (1) has (i) an appropriate calorific value, and (ii) has absorption in an appropriate wavelength range (the inventors have (i) and (ii) In addition, among metal-containing azo dyes, (iii) the excitation-state deactivation rate is large (the present inventors consider that (iii) is a photon mode. This is considered to be a factor that contributes at least to the reaction. As a result, there is a possibility that the balance between the decomposition reaction of the heat mode and the photon mode is good, jitter can be reduced, and crosstalk can be reduced. Therefore, when combined with the second recording layer of the two-layer optical recording medium, a remarkable effect is easily exhibited. This is because, as described above, an increase in jitter and crosstalk tends to be remarkable in a two-layer optical recording medium. In the reverse laminate as the second recording layer, it is preferable to make the groove depth shallower than the conventional groove depth in order to obtain sufficient reflectance. The shallow groove is one of the causes of increasing jitter and crosstalk. Further, when recording in a region corresponding to the groove portion of the substrate, it is necessary to increase the thickness of the recording layer in order to obtain a sufficient recording modulation degree as described above. Such a thick recording layer is another cause of increased jitter and crosstalk. Note that jitter and crosstalk tend to increase as the recording speed increases. On the other hand, in a two-layered optical recording medium based on the 2P method according to a third embodiment to be described later, there are cases where unevenness of the film thickness of the 2P layer or optical distortion or warpage caused by 2P curing shrinkage occurs. For this reason, the beam of the recording laser beam is distorted, or an offset of the beam traveling portion of the recording portion is generated, which may cause a jitter or crosstalk to be increased particularly during high-speed recording. Therefore, the metal-containing azo dye according to the above formula (1) is contained in the second recording layer (the recording layer on the side far from the laser beam incident side) of the two-layer optical recording medium by the 2P method. By doing so, a remarkable effect can be obtained.

The metal-containing azo dye according to the above formula (1) is an azo dye that enables a high refractive index at the recording laser wavelength by a combination of its ligand and metal. The metal-containing azo dye according to the above formula (1) has a calorific value greater than a certain level. Furthermore, combining the central metal ion with Zn ²⁺ increases the probability of radiative transition when excited by recording light, or causes energy transfer to or from another molecule. It is thought that it decomposes at a very high speed without going through much. That is, the recording layer containing the metal-containing azo dye according to the above formula (1) is considered to be decomposed, that is, the formation of the recording portion is completed in a very short time. As a result, the above-described disturbance in high-speed recording is reduced, and good high-speed recording with small jitter and crosstalk is easily achieved in the second recording layer of the two-layer optical recording medium.

  The effect of reducing the jitter can be known by, for example, increasing the jitter asymmetry margin. In addition to the MT% and ST% described above, the reduction in crosstalk can be known by increasing the asymmetry margin.

  Examples of the metal-containing azo dye according to the above formula (1) include the following dyes.

[Third Embodiment]
Subsequently, an embodiment of the above-described second optical recording medium of the present invention (hereinafter referred to as “third embodiment of the present invention”) will be described.

  FIG. 5 is a cross-sectional view schematically showing a configuration of an optical recording medium according to the third embodiment of the present invention. An optical recording medium 300 shown in FIG. 5 includes a recording layer (2) (second recording layer) 302 containing a dye, a translucent reflective layer (second substrate) on a disk-shaped substrate (2) 301 (second substrate). 2) 303 (second reflective layer), transparent resin layer 304, recording layer containing dye (1) 305 (first recording layer), reflective layer (1) 306 (first reflective layer), adhesive layer 307 And a substrate (1) 308 (first substrate) in this order. In the recording layer (2) 302 and the recording layer (1) 306, optical information is recorded / reproduced by the laser beam 310 incident from the substrate (2) 109 side. The substrate (2) 301, the recording layer (2) 302, and the reflective layer (2) 303 may be collectively referred to as a “positive laminate”. Further, the recording layer (1) 305 corresponds to the above-mentioned “second recording layer”.

  Details of materials, formation methods, and the like of the substrate (2) 301, the recording layer (2) 302, and the reflective layer (2) 303 are the substrate (2 of the optical recording medium 100 described in the section of the first embodiment). ) 109, the recording layer (2) 108, and the details of the reflective layer (2) 107, respectively.

  Subsequently, a transparent resin layer 304 is formed on the reflective layer (2) 303. As a method for forming the transparent resin layer 304, a 2P (Photo Polymerization) method is usually used. When the guide groove is formed in the transparent resin layer 304 (which may be referred to as “intermediate layer”) using the 2P method, the procedure is usually as follows.

  First, a resin raw material layer is formed on the reflective layer (2) 303 by applying a photocurable resin raw material or the like that is cured by light typified by radiation such as ultraviolet rays. Subsequently, a stamper having a concavo-convex shape for transfer (hereinafter appropriately referred to as “transfer concavo-convex shape”) is placed thereon. Next, after the photocurable resin raw material is cured, the stamper is peeled off. In this way, the concavo-convex shape for transfer of the stamper is transferred to the surface of the photocurable resin, and the transparent resin layer 304 (2P layer) having the concavo-convex shape, that is, the guide groove, is formed by a cured product of the photocurable resin. Can be done. In this case, in order to obtain a sufficient reflectance, the depth of the guide groove may be in the range of (1/100) × λ or more and (1/6) × λ or less. . “Λ” represents the recording / reproducing wavelength of the laser beam 310.

As the stamper, for example, a stamper formed of cyclic polyolefin or polystyrene resin can be used.
In addition, as the photocurable resin used as the material of the transparent resin layer 304, various electron beam curable materials described as the material of the transparent resin layer 105 of the optical recording medium 100 described in the section of the first embodiment. Examples thereof include resins and ultraviolet curable resins.

  Subsequently, a recording layer (1) 305 which is a second recording layer is formed on the transparent resin layer 304. As the dye of the recording layer (1) 305, at least the metal-containing azo dye according to the above formula (1) is used. Any one of the metal-containing azo dyes according to the above formula (1) may be used alone, or two or more thereof may be used in any combination and ratio. Moreover, in addition to the 1 type, or 2 or more types of metal-containing azo pigment | dye which concerns on the said Formula (1), you may use together another 1 type, or 2 or more types of pigment | dye. There are no particular limitations on the type of other dyes that can be used in combination with the metal-containing azo dye according to the above formula (1). As an example, the same dye as that used for the recording layer (1) 103 of the optical recording medium 100 described in the section of the “first embodiment” may be mentioned. The details of the recording layer (1) 305 other than the dye, the formation method, and the like are the same as the details of the recording layer (1) 103 of the optical recording medium 100 described in the section of the first embodiment. is there.

  Next, the reflective layer (1) 306 is formed on the recording layer (1) 305. Details of the material, formation method, and the like of the reflective layer (1) 306 are the same as the details of the reflective layer (1) 102 of the optical recording medium 100 described in the section of the first embodiment.

  Thereafter, the substrate (1) 308 is provided on the reflective layer (1) 306. Details of the material and the like of the substrate (1) 308 are the same as the details of the substrate (1) 101 of the optical recording medium 100 described in the section of the first embodiment. In addition, the method of providing the substrate (1) 308 on the reflective layer (1) 306 is not particularly limited. Usually, as shown in FIG. 5, a preformed substrate (1) 308 is prepared, and this is applied to the reflective layer ( 1) It is formed by bonding onto 306 via an adhesive layer 307.

  The material of the adhesive layer 307 is not particularly limited. Examples include various curable resins similar to the transparent resin layer 105 of the optical recording medium 100 described in the section of [First Embodiment], conventionally known various adhesives, pressure-sensitive double-sided tape, and the like. It is done.

  In the case of using a curable resin, from the raw material of the curable resin on the reflective layer (1) 306 by the same application method as that for the transparent resin layer 105 of the optical recording medium 100 described in the section of the first embodiment. A layer (curable resin raw material layer) to be formed, and a substrate (1) 308 is placed thereon and pressed, and conditions for curing the curable resin raw material during or after pressing (UV curable resin or radiation) In the case of a curable resin, an ultraviolet ray or radiation is applied, and in the case of a thermosetting resin, the adhesive layer 307 made of the curable resin is formed by curing the curable resin raw material, and the adhesive layer The reflective layer (1) 306 and the substrate (1) 308 are bonded to each other through 307.

  In the case of using an adhesive, the adhesive layer 307 is formed by applying the adhesive on the reflective layer (1) 306 by a method such as screen printing, placing the substrate (1) 308 on the reflective layer (1) 306, and pressing it. At the same time, the reflective layer (1) 306 and the substrate (1) 308 are bonded via the adhesive layer 307.

  When a double-sided tape (for example, a pressure-sensitive double-sided tape) is used, an adhesive layer 307 is formed by pressing the pressure-sensitive double-sided tape between the reflective layer (1) 306 and the substrate (1) 308, The reflective layer (1) 306 and the substrate (1) 308 are bonded through the adhesive layer 307.

  The light transmittance of the adhesive layer 307 formed by the above method is not particularly limited, and may be transparent or opaque. The thickness of the adhesive layer 307 is not particularly limited, but is usually 1 μm or more, preferably 3 μm or more, and usually 300 μm or less, preferably 100 μm or less.

  Although the optical recording medium 300 according to the third embodiment has been described above, the embodiment of the present invention is not limited to this, and can be implemented with arbitrary modifications.

  For example, other arbitrary layers may be provided between the layers of the optical recording medium 300 described above. Examples of other layers include a protective coat layer provided between the reflective layer (2) 303 and the transparent resin layer 304, a barrier layer provided between the transparent resin layer 304 and the recording layer (1) 305, and the like. Is mentioned. The details of the material and forming method of the protective coat layer and the barrier layer are the same as the details of the protective coat layer 106 and the barrier layer 104 of the optical recording medium 100 described in the section of the first embodiment.

  Hereinafter, the present embodiment will be described more specifically based on examples (experimental examples). The present embodiment is not limited to the following examples (experimental examples) as long as the gist thereof is not exceeded.

[Experimental conditions]
In Experimental Examples 1, 2, and 4 to be described later, a two-layer type optical recording medium (an optical recording medium having a configuration shown in FIG. 1A) having a reverse laminate is prepared according to the following procedure. MT (%) and ST (%) of the optical information recorded on the recording layer (1) to be formed were measured.

[Preparation of optical recording medium]
<Preparation of reverse laminate>
First, a substrate having a diameter of 120 mm and a thickness of 0.60 mm in which grooves having a pitch of 0.74 μm, a width of 340 nm, and a depth of 28 nm are formed by injection-molding polycarbonate using a Ni stamper having grooves formed on the surface. (1) was formed. Next, an Ag—Bi—Nd alloy was formed into a thickness of 80 nm on the substrate (1) by sputtering to form a reflective layer (1). Next, as an organic dye compound, a tetrafluoropropanol solution (concentration 2) of a mixture of dye A and dye B, which are metal-containing azo dyes represented by the following chemical formulas (dye A: dye B = 50 wt%: 50 wt%), respectively. % By weight) was added dropwise onto the above-mentioned reflective layer (1), spin-coated, and then dried at 70 ° C. for 30 minutes to form a recording layer (1). The film thickness of the recording layer (1) in the groove portion of the substrate (1) (the groove portion of the reverse laminate in FIG. 1A, that is, the film thickness of the recording layer far from the incident laser beam) is about 70 nm, and the substrate (1) The thickness of the recording layer (1) in the inter-groove portion (the inter-groove portion of the reverse laminate in FIG. 1A, that is, the recording layer thickness near the incident laser beam) was about 60 nm. The OD value of the recording film was 1.20.

  Subsequently, after forming the recording layer (1), a barrier layer made of each composition described in Table 2 of [Experimental Example 1] described later is sputtered on the recording layer (1) as much as possible. Formed by. Here, the film thickness of the barrier layer was adjusted to 2 nm by adjusting the sputtering time. The pre-sputtering was performed before the barrier layer was sputtered. In this way, an inversely laminated disk 1 was prepared.

<Preparation of regular laminate>
A polycarbonate substrate (2) having guide grooves having a depth of 160 nm, a width of 360 nm, and a track pitch of 740 nm was prepared, and the above-described metal-containing azo dye was formed on the surface of the substrate (2) on which the guide grooves were formed. A tetrafluoropropanol solution (concentration 2% by weight) of a mixture of a certain dye A and a dye C which is a metal-containing azo dye represented by the following chemical formula (dye A: dye C = 10% by weight: 90% by weight) is dropped, After spin coating, the recording layer (2) was formed by drying at 70 ° C. for 30 minutes. The thickness of the recording layer (2) (the thickness of the recording layer in the groove portion of the positive laminate in FIG. 1A) was about 80 nm. Next, on the recording layer (2), an Ag—Bi alloy (Bi: 1.0 atomic%) was formed by sputtering so as to have a thickness of 17 nm to form a reflective layer (2). Further, an ultraviolet curable resin (radical ultraviolet curable resin SD347 manufactured by Dainippon Ink Co., Ltd.) is spin coated on the reflective layer (2) and cured to form a protective coating layer having a thickness of 3 μm to 4 μm. Thus, a positively laminated disk 2 was prepared.

<Preparation of two-layer type optical recording medium>
On the barrier layer of the disk 1 which is the reverse laminate prepared by the above-described method, resin A (a radical ultraviolet curable resin manufactured by Dainippon Ink Co., Ltd .: elastic modulus 4000 MPa (30 ° C.), glass transition temperature Tg = 174 ° C.) was applied by adjusting the spin coat rotation speed so that the film thickness was 23 μm. Further, the resin A was applied on the protective coating layer of the disk 2 which is a positive laminate, with the spin coating rotation speed adjusted so as to have a film thickness of 23 μm. Next, the disc 1 and the disc 2 each coated with the resin A are overlapped so that the surfaces coated with the resin A are opposed to each other, and then ultraviolet rays are applied from the substrate (2) side of the disc 2 (regular laminate). To cure the resin A and form a transparent resin layer made of the resin A to prepare a two-layer optical recording medium.

  The elastic modulus and glass transition temperature Tg of the resin A were measured using a dynamic viscoelasticity tester (manufactured by Leo Vibron: DDV series) under the conditions of a measurement frequency of 3.5 Hz and a heating rate of 3 ° C./min. .

[Conditions for high-speed recording of optical information on disk 1 (reverse laminate)]
The conditions for high-speed recording of optical information on the disc 1 which is a reverse laminate are as follows.
As an evaluator, DDU-1000 (wavelength 662 nm, numerical aperture NA = 0.65 of the objective lens) manufactured by Pulse Tech was used.
The recording speed was 2.4 times that of DVD (linear speed: 9.2 m / s).
The recording pulse strategy conformed to DVD + Recordable Dual Layer 8.5 Gbytes Basic Format Specifications version 1.1.
The recording power was 17 mW to 25 mW.
Jitter (data-to-clock jitter) measurement was performed while reproducing at 1 × speed.

[Evaluation of MT, ST, ΔJitter]
Since normal optical disc products are recorded without emptying the track, MT (%) is a value that reflects the signal quality of the optical disc. MT (%) generally needs to be 13% or less, preferably 10% or less, and more preferably 9% or less. If it exceeds 13%, the error tends to increase.

  Note that ST (%) is preferably 10% or less. More preferably, it is 9% or less, More preferably, it is 8% or less. If ST (%) does not fall below 10% regardless of how the film thickness of the barrier layer is changed or the recording strategy, it is determined that the barrier layer is not an appropriate material.

  Further, the difference between ST (%) and MT (%), that is, Δjitter is preferably 2% or less, more preferably 1.6% or less, and further preferably 1% or less. Beyond that, MT (%) may exceed 13%.

[Experimental Example 1]
According to the above-mentioned procedure, a two-layer type optical recording medium (two-layer DVD-R disc) in which a 2 nm barrier layer made of the material shown in Table 2 below was provided on the disc 1 was produced. DVD-R 2.4-times speed recording was performed on the obtained optical recording medium disk 1 under the above-described conditions, and ST (%), MT (%), and Δjitter were measured. The obtained ST (%), MT (%) and Δjitter results are shown in Table 2 below. FIG. 2 is a graph in which the thermal conductivity is plotted on the horizontal axis and Δjitter is plotted on the vertical axis for materials having ST (%) of 9% or less. In the graph of FIG. 2, “♦” corresponds to each material. From the graph of FIG. 2, it can be seen that the characteristics are rapidly improved when the thermal conductivity becomes higher than 70 W / m · K (Sn thermal conductivity 67 W / m · K) as a boundary. Furthermore, when the thermal conductivity is 90 W / m · K or more, Δjitter is 1% or less except for Si and C, which are semiconductors, and it can be seen that extremely good characteristics can be obtained. Note that it is considered that characteristics of Si and C can be improved by mixing and using other metal components.

  FIG. 4 shows a graph of ST (%) and MT (%) obtained by using various materials for the barrier layer. From the graph of FIG. 4, Al (thermal conductivity 237 W / m · K), Mo (thermal conductivity 138 W / m · K), W (thermal conductivity 174 W / m · K), Cu (thermal conductivity 401 W / m). It can be seen that the recording characteristics of K) are very good. Both Co and Cr had good sensitivity and good jitter in 4 × speed recording and 8 × speed recording. Note that Ag, Al, Si, and C may be a barrier layer with good recording characteristics and weather resistance due to alloying or improvement of a photocurable resin. Moreover, there is a possibility that Au can improve characteristics such as MT (%) and ST (%) by adjusting the recording pulse strategy. However, compared to the above-mentioned very good Mo, W, Cu, Co, Cr, and Al, Au has a narrower recording pulse margin and tends to be somewhat unfavorable. It is considered that this is due to the mechanical properties of Au at high temperatures.

  On the other hand, for Nb and Ta with ST (%) exceeding 10%, Δjitter is as small as 0.9% and 0.4%, respectively, but the jitter of each mark length is all bad. However, this jitter value could not be improved. Therefore, it can be seen that Nb (thermal conductivity 54 W / m · K) and Ta (thermal conductivity 58 W / m · K) cannot be selected as the material of the barrier layer of the present invention.

[Experiment 2]
Mo, Co (thermal conductivity 100 W / m · K) having a thermal conductivity defined in the present invention, and ZnS—SiO ₂ which is a dielectric film as a comparison thereof are used as materials, and according to the above procedure, respectively. A two-layer optical recording medium (double-layer DVD-R disk) in which a barrier layer having a thickness shown in Table 3 was provided on the disk 1 was produced. DVD-R 2.4-times speed recording was performed on the obtained optical recording medium disk 1 under the above-described conditions, and ST (%), MT (%), and Δjitter were measured. The obtained ST (%), MT (%) and Δjitter results are shown in Table 3 below. FIG. 3 shows a graph plotted with the barrier layer thickness on the horizontal axis and Δjitter on the vertical axis.

As is apparent from Table 3 and FIG. 3, the optical recording medium having a Mo and Co barrier layer having a thermal conductivity exceeding 70 W / m · K tends to decrease Δjitter when the film thickness is thinner than 5 nm. The jitter is better than that of ZnS—SiO ₂ . In particular, when the film thickness is around 3 nm, both Mo and Co are stable and good ST (%), MT (%) and Δjitter can be obtained.

On the other hand, ZnS—SiO ₂ has a Δjitter of about 2% regardless of the film thickness, indicating that it is not possible to obtain as good characteristics as the barrier layer of the present invention. This difference is considered to be caused by the fact that the thermal conductivity of the dielectric is very low, approximately 1/100 or less of the conductivity of the present invention. That is, since the dielectric film cannot provide a sufficient heat dissipation effect, it is a shallow groove, and good crosstalk characteristics cannot be obtained in the reverse stacking configuration. In addition, it is considered that the dielectric film has poor ductility and malleability like the metal, alloy, and semiconductor films of the present invention, so that it is impossible to obtain extremely good ST (%) characteristics.

[Experiment 3]
Among the optical recording media manufactured in Experimental Example 1, an optical recording medium using Mo, Cr, Co (film thickness is all 2 nm) as the material of the barrier layer is placed in a test tank of 80 ° C. and 85% relative humidity after recording. The signal was stored and taken out after 250 hours to reproduce the signal of the recording section. It was found that all optical recording media had good storage stability with almost no change in PI (Parity of Inner-code) error.

[Experimental Example 4]
[Preparation of optical recording medium]
<Preparation of reverse laminate>
First, a substrate having a diameter of 120 mm and a thickness of 0.60 mm in which grooves having a pitch of 0.74 μm, a width of 340 nm, and a depth of 28 nm are formed by injection-molding polycarbonate using a Ni stamper having grooves formed on the surface. (1) was formed. Next, an Ag—Bi—Nd alloy was formed into a thickness of 80 nm on the substrate (1) by sputtering to form a reflective layer (1). Next, as an organic dye compound, tetrafluoro of a mixture of the dye A (center metal is Ni ²⁺ ) and the dye B (center metal is Zn ²⁺ ) (dye A: dye B = 50 wt%: 50 wt%). A propanol solution (concentration: 2.1% by weight) was prepared, dropped onto the above-mentioned reflective layer (1), spin-coated, and then dried at 70 ° C. for 30 minutes to form a recording layer (1). The OD value of the film was 1.20.

  The dye B had a calorific value in a nitrogen atmosphere of 40.7 Cal / g and a decomposition temperature of 278 ° C. It was found that the dye B had a calorific value appropriate for at least heat mode recording. The calorific value and the decomposition temperature were measured using a TG / DTA 6200 manufactured by Seiko Instruments Inc. under the conditions of a heating rate of 10 ° C./min and a sample amount of about 4 mg.

  The absorption maximum wavelengths of the dye-coated film of Dye B are 554.1 nm and 601.9 (strong) nm, and Dye B is 15.5% of the absorbance of the absorption maximum near the recording wavelength of 660 nm. It was found that the dye has an appropriate amount of absorption for recording on the second recording layer of the two-layer type optical recording medium.

Subsequently, after the formation of the recording layer (1), ZnS-SiO ₂ was formed on the recording layer (1) to a thickness of 130 nm by sputtering, with as little time as possible. In this way, an inversely laminated disk 1 was prepared.

<Preparation of regular laminate>
A polycarbonate substrate (2) having guide grooves having a depth of 160 nm, a width of 360 nm, and a track pitch of 740 nm was prepared, and the dye A and the dye C were formed on the surface of the substrate (2) on which the guide grooves were formed. A tetrafluoropropanol solution (concentration: 2% by weight) of a mixture of (A) and (Dye A: Dye C = 10% by weight: 90% by weight) was added dropwise, spin-coated, dried at 70 ° C. for 30 minutes, and the recording layer (2 ) Was formed. The thickness of the recording layer (2) (the thickness of the recording layer in the groove portion of the positive laminate in FIG. 1A) was about 80 nm. Next, on the recording layer (2), an Ag—Bi alloy (Bi: 1.0 atomic%) was formed by sputtering so as to have a thickness of 17 nm to form a reflective layer (2). Further, an ultraviolet curable resin (radical ultraviolet curable resin SD347 manufactured by Dainippon Ink Co., Ltd.) is spin coated on the reflective layer (2) and cured to form a protective coating layer having a thickness of 3 μm to 4 μm. Thus, a positively laminated disk 2 was prepared.

<Preparation of two-layer type optical recording medium>
On the barrier layer of the disk 1 which is the reverse laminate prepared by the above-described method, resin A (a radical ultraviolet curable resin manufactured by Dainippon Ink Co., Ltd .: elastic modulus 4000 MPa (30 ° C.), glass transition temperature Tg = 174 ° C.) was applied by adjusting the spin coat rotation speed so that the film thickness was 23 μm. Further, the resin A was applied on the protective coating layer of the disk 2 which is a positive laminate, with the spin coating rotation speed adjusted so as to have a film thickness of 23 μm. Next, the disc 1 and the disc 2 each coated with the resin A are overlapped so that the surfaces coated with the resin A are opposed to each other, and then ultraviolet rays are applied from the substrate (2) side of the disc 2 (regular laminate). To cure the resin A and form a transparent resin layer made of the resin A to prepare a two-layer optical recording medium.

  The elastic modulus and glass transition temperature Tg of resin A were measured using a dynamic viscoelasticity tester (manufactured by Leo Vibron: DDV series) under the conditions of a measurement frequency of 3.5 Hz and a temperature increase rate of 3 ° C./min. .

[High-speed recording conditions for disc 1 (reverse laminate)]
The conditions for high-speed recording of optical information on the disk 1 (reverse laminate) are as follows.
As an evaluator, DDU-1000 (wavelength 662 nm, numerical aperture NA = 0.65 of the objective lens) manufactured by Pulse Tech was used.
The recording speed was set to 4 times the speed of DVD (4 × recording) (linear velocity: 15.3 m / s).
The recording pulse strategy conformed to DVD + Recordable Dual Layer 8.5 Gbytes Basic Format Specifications version 1.1.
The pulse power ratio P ₀ / P _m = 1.7.
The recording power was 20 mW to 40 mW.
Jitter (data-to-clock jitter) measurement was performed at 1 × speed.

  6A is a graph showing the relationship between jitter and asymmetry in the reverse laminate of the optical recording medium manufactured in Experimental Example 4, and FIG. 6B is the optical recording medium manufactured in Experimental Example 4. 5 is a graph showing the relationship between jitter and recording power in the reverse laminated body. “Asymmetry” is a value defined as “asymmetry” in the DVD-R or DVD + R standard. When the asymmetry is a positive value, it means that the recording is performed with a sufficiently large recording power, and when the asymmetry is a negative value, it means that the recording power is insufficient.

  The curve shown as “Dye A + Dye B” in FIG. 6A is the asymmetry margin of jitter of the reverse laminate including the dye whose Zn is the central metal ion in the recording layer (1). Despite the extremely high recording speed of 4 × in the two-layer optical recording medium, the asymmetry is -5% (corresponding to “−0.05” in FIG. 6A) to + 15% (FIG. 6). (A) corresponds to “0.15”.) Even if it is changed in a very wide range up to a value slightly exceeding “0.15”, it can be seen that a good jitter of 9% can be secured.

  On the other hand, in the reverse laminate of Experimental Example 4, except that the dye B whose central metal is Zn ion is changed to the dye C whose central metal is not Zn ion, and dye A: dye C = 40 wt%: 60 wt% FIG. 6A shows the result of examining the asymmetry margin of jitter of 4 × recording in the same manner as the curve shown as “Dye A + Dye C” in FIG. 6A. It can be seen that the asymmetry margin and bottom jitter are not better for “Dye A + Dye C” than for the combination of “Dye A + Dye B”. The calorific value of Dye C in a nitrogen atmosphere was 27.6 Cal / g, and the decomposition temperature was 348 ° C. The absorption maximum wavelengths of the dye coating film of Dye C are 547.11 nm and 597.05 nm, and Dye C has an absorption of 14.4% of the absorbance at the absorption maximum in the vicinity of the recording wavelength of 660 nm. It turned out to be a pigment. The shape of the absorption spectrum of the film of Dye C was slower than that of Dye B.

  FIG. 6B shows the result of measuring the 4% recording MT% of the above reverse laminate of “Dye A + Dye B” and “Dye A + Dye C” while changing the recording laser power. Also in MT%, it can be seen that the combination of “Dye A + Dye B” is superior to the combination of “Dye A + Dye C”.

From the above results, it can be seen that the inclusion of the dye of the present invention having Zn ²⁺ as the central metal has a wider jitter asymmetry margin, better jitter value itself, and reduced crosstalk. It became clear.

[Experimental Example 5]
In Experimental Example 5, a two-layer type optical recording medium having the configuration shown in FIG. 5 was prepared according to the following procedure, and the MT of optical information recorded in the recording layer (1) (second recording layer) ( %) And ST (%) were measured.

First, polycarbonate was injection-molded using a Ni stamper with grooves formed on the surface to form grooves with a pitch of 0.74 μm, a width of 0.33 μm, and a depth of 160 nm, a diameter of 120 mm, a thickness of 0.1 mm. A 57 mm substrate (2) was formed.
Next, a tetrafluoropropanol solution (concentration 2 wt%) of a mixture of the dye A and the dye C (Dye A: Dye C = 10 wt%: 90 wt%) was dropped and spin-coated, and then 70 ° C. And dried for 30 minutes to form a recording layer (2). Further, a translucent reflective layer (2) having a thickness of 17 nm was formed on the recording layer (2) by sputtering using an Ag alloy made of Ag—Bi (Bi: 1.0 atomic%).

  Next, a predetermined ultraviolet curable resin [1] for forming a transparent resin layer was dropped in a circular shape on the reflective layer (2), and a film having a thickness of about 25 μm was formed by a spinner method. On the other hand, a predetermined ultraviolet curable resin [2] was dropped in a circular shape on the surface of the resin stamper on which the guide groove was formed, and a film having a thickness of about 25 μm was formed by a spinner method.

  Next, a resin stamper was bonded onto the reflective layer (2) so that the resin layer made of the ultraviolet curable resin [1] and the resin layer made of the ultraviolet curable resin [2] face each other. Subsequently, ultraviolet rays were irradiated from the resin stamper side to cure and bond these resin layers, thereby forming an adhesive body having a transparent resin layer (2P layer) having guide grooves. The formed guide groove on the transparent resin had a track pitch of 0.74 μm, a groove width of 290 nm, and a groove depth of 190 nm.

In addition, as the ultraviolet curable resins [1] and [2], the following radical ultraviolet curable resins were used, respectively. The glass transition temperatures of the ultraviolet curable resins [1] and [2] are shown in parentheses.
Ultraviolet curable resin [1]: Dainippon Ink & Co., Ltd. SD6036 (Tg = 60 ° C.)
UV curable resin [2]: Nippon Kayaku Co., Ltd. MPZ388 (Tg = 161 ° C.)

On the transparent resin layer (2P layer), as an organic dye compound, the dye A (center metal is Ni ²⁺ ) and the dye B (center metal is Zn ²⁺ ), and a dye D ( Tetrafluoropropanol solution (concentration 2) of a mixture (Dye A: (Dye B + Dye D) = 50 wt% :( 15 wt% + 35 wt%) = 50 wt%: 50 wt%) with the central metal being Zn ²⁺ ) .1 wt%) was prepared, dropped onto the above-mentioned reflective layer (1), spin-coated, and then dried at 70 ° C. for 30 minutes to form a recording layer (1).

In addition, the calorific value of the dye B in the nitrogen atmosphere is 40.7 Cal / g and the decomposition temperature is 278 ° C., and the calorific value of the dye D in the nitrogen atmosphere is 34.1 Cal / g and the decomposition temperature is 251 ° C. It has been found that any of these dyes having a central metal ion of Zn ²⁺ has a suitable amount of heat generation for at least heat mode recording. The calorific value and the decomposition temperature were measured using a TG / DTA 6200 manufactured by Seiko Instruments Inc. under the conditions of a heating rate of 10 ° C./min and a sample amount of about 4 mg.

  The absorption maximum wavelengths of the dye-coated film of Dye B are 554.1 nm and 601.9 (strong) nm, and Dye B is 15.5% of the absorbance of the absorption maximum near the recording wavelength of 660 nm. It can be seen that the dye has an appropriate amount of absorption for recording on the second recording layer of the two-layer type optical recording medium.

  The absorption maximum wavelengths of the dye D coating film of Dye D are 561.6 nm and 608.3 (strong) nm, and Dye D is 20.1% of the absorbance at the absorption maximum in the vicinity of the recording wavelength of 660 nm. It can be seen that the dye has an appropriate amount of absorption for recording on the second recording layer of the two-layer type optical recording medium.

  Subsequently, a reflective layer (1) having a thickness of 120 nm was formed by a sputtering method using an Ag alloy made of Ag—Bi (Bi: 1.0 atomic%).

  Further, an ultraviolet curable resin was spin-coated on the reflective layer (1) to provide an adhesive layer. Then, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was placed on the adhesive layer to form a substrate (2), which was cured by being irradiated with ultraviolet rays and adhered. As described above, a two-layer optical recording medium by the 2P method was manufactured.

[High-speed recording conditions in the recording layer (1) of the two-layer optical recording medium]
The conditions for high-speed recording of optical information on the recording layer (1) of the two-layer optical recording medium are as follows.
As an evaluation machine, ODU-1000 (wavelength 660 nm, numerical aperture NA = 0.65 of the objective lens) manufactured by Pulse Tech was used.
The recording speed was 8 times the speed of DVD (8 × recording) (linear velocity 30.67 m / s).
The recording pulse strategy conformed to DVD + Recordable Dual Layer 8.5 Gbytes Basic Format Specifications version 1.1.
The pulse power ratio P ₀ / P _m = 1.3.
The recording power was 40 mW to 52 mW.
Jitter (data-to-clock jitter) measurement was performed while reproducing at 1 × speed.

FIG. 7 is a graph showing the relationship between jitter and asymmetry in the recording layer (1) of the optical recording medium produced in Experimental Example 5.
In FIG. 7, the measurement result of the jitter asymmetry margin of the 8 × speed recording on the recording layer (1) is a curve shown as “Dye A + Dye B + Dye D”. Even under a very large condition that the asymmetry of the recording layer (1) of “Dye A + Dye B + Dye D” is about + 10% (corresponding to “0.1” in FIG. 7), the jitter is 9% or less. The very high speed recording characteristics of the two-layer optical recording medium were shown.

On the other hand, the two-layer type obtained in exactly the same manner except that Dye B and Dye D were changed to Dye C whose central metal ion was Ni ²⁺ and Dye A: Dye C = 50 wt%: 50 wt% The above 8 × speed recording was performed on the recording layer (1) of the optical recording medium. The result is a curve shown as “Dye A + Dye C” in FIG. The calorific value of Dye C in a nitrogen atmosphere was 27.6 Cal / g, and the decomposition temperature was 348 ° C. The absorption maximum wavelengths of the dye coating film of Dye C are 547.11 nm and 597.05 nm, and Dye C has an absorption of 14.4% of the absorbance at its absorption maximum in the vicinity of the recording wavelength of 660 nm. It turned out to be a pigment. The shape of the absorption spectrum of the film of Dye C was slower than that of Dye B and Dye.

From FIG. 7, it can be seen that with the combination of the dye A and the dye C, the jitter sharply increases and gets worse as the asymmetry exceeds + 6% in the recording layer (1). From the above, by combining with the dye B and the dye D of the present invention whose central metal is Zn ^2+, it is called 8 × speed recording in the second recording layer (recording layer (1)) of the two-layer type optical recording medium. It was found that extremely high speed recording can be performed very well.

  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.

  In addition, this application is based on the Japanese application (Japanese Patent Application No. 2005-111244) for which it applied on April 7, 2005, The whole is used by reference.

(A) is sectional drawing which shows typically the structure of the optical recording medium which concerns on the 1st Embodiment of this invention, (b) is the structure of the optical recording medium which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows this typically. 6 is a graph showing the relationship between Δjitter and the bulk thermal conductivity of the material of the barrier layer in the reverse laminated body of the optical recording medium manufactured in Experimental Example 1. 6 is a graph showing the relationship between the thickness of a barrier layer and Δjitter in the reverse laminated body of the optical recording medium manufactured in Experimental Example 2. 6 is a graph showing the relationship between the barrier layer material and ST (%) and MT (%) in the reverse laminated body of the optical recording medium manufactured in Experimental Example 1. It is sectional drawing which shows typically the structure of the optical recording medium which concerns on the 3rd Embodiment of this invention. (A) is a graph showing the relationship between jitter and asymmetry in the reverse laminated body of the optical recording medium manufactured in Experimental Example 4, and (b) is the reverse laminated body of the optical recording medium manufactured in Experimental Example 4. 3 is a graph showing the relationship between jitter and recording power. 10 is a graph showing the relationship between jitter and asymmetry in the recording layer (1) of the optical recording medium produced in Experimental Example 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Reverse laminated body 12 Normal laminated body 100,200,300 Optical recording medium 101,308 Substrate (1)
102,306 Reflective layer (1)
103,305 Recording layer (1)
104, 204 Barrier layers 105, 205 Transparent resin layer 304 Transparent resin layer (2P layer)
106 Protective coating layers 107, 303 Reflective layer (2)
108,302 Recording layer (2)
109,301 Substrate (2)
110, 210, 310 Laser light 201 Substrate 202 Reflective layer 203 Recording layer 307 Adhesive layer

Claims (8)

An optical recording medium having a reflective layer, a recording layer containing a dye, and a transparent resin layer in this order on a substrate,
While providing a barrier layer between the recording layer and the resin layer,
The thermal conductivity M at 300 K as a bulk of the material used for the barrier layer is 70 W / m · K or more,
An optical recording medium, wherein the thickness t of the barrier layer is less than 5 nm. The optical recording medium according to claim 1, wherein the M is 90 W / m · K or more. The optical recording medium according to claim 1, wherein the t is 1 nm or more and 4 nm or less. The barrier layer is made of Mg, Cr, Mn, Fe, Ni, Zn, Ru, Rh, Pd, In, Os, Ir, Pt, Mo, Al, W, Co, Cr, Cu, Ag, and Au. 4. The optical recording medium according to claim 1, wherein the optical recording medium is a single metal element selected from the group consisting of: 5. The barrier layer according to claim 4, wherein the barrier layer is a single metal element selected from the group consisting of Mo, W, Cu, Co, Cr, and Al or an alloy containing the metal element as a main component. Optical recording medium. The light according to claim 1, further comprising a second reflective layer, a second recording layer, and a transparent substrate provided in this order on the transparent resin layer. recoding media. 7. The optical recording medium according to claim 6, wherein the recording layer contains at least a metal-containing azo dye composed of an azo compound represented by the following general formula (1) and a Zn metal ion as a 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 the first substrate, the first reflective layer, the first recording layer containing the dye, the transparent resin layer, the second reflective layer, the second recording layer containing the dye, and the second substrate are arranged in this order. An optical recording medium comprising:
The optical recording medium, wherein the first recording layer contains at least a metal-containing azo dye comprising an azo compound represented by the following general formula (1) and a Zn metal ion as a 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. )

Images