HK1116288B - Optical recording medium - Google Patents

Description

Optical recording medium

Technical Field

The present invention relates to an optical recording medium, and more particularly, to an optical recording medium capable of high-speed recording and having good recording and reading characteristics.

Background

In recent years, various optical recording media such as DVD-RW and DVD-R have been widely known as external storage devices in information processing devices such as computers because of their ease of storing large amounts of information and random access. For example, a typical DVD-R having an organic dye recording layer has a laminated structure, and performs recording and reading by laser light through a substrate, in which the dye recording layer and a reflective layer are provided in the stated order on a transparent optical disc substrate, and a protective layer is provided to cover the recording layer or the reflective layer. In order to further increase the recording capacity of these optical recording media, multilayer optical recording media in which two or more recording layers are provided on 1 medium have been developed, and for example, a two-layer optical recording medium having 2 pigment recording layers on a disc-shaped transparent 1 st substrate, with an intermediate layer made of an ultraviolet-curable resin interposed between the 2 pigment recording layers, has been disclosed.

As such a two-layer type optical recording medium, a 2P (photo polymerization) method using a transparent stamper, and a method of forming two optical disc substrates each including a recording layer and a reflective layer laminated on each other and bonding the two substrates to each other through a photocurable resin layer are known. In both cases, a reflective layer and a recording layer containing a dye (hereinafter, also referred to as a recording layer (1) or a 2 nd recording layer) are laminated in the stated order on the substrate located on the innermost side of the laser light incident surface.

In the method of bonding two optical disk substrates each composed of a recording layer and a reflective layer, the optical disk substrates are manufactured by forming a 1 st optical disk substrate in which the recording layer and the reflective layer are laminated in the stated order on a substrate having a guide groove for a recording track formed thereon (hereinafter, the transparent resin layer having the groove formed thereon is referred to as a substrate, and thus such a laminate or laminated structure is sometimes referred to as a "front laminate" or a "front laminated structure"), and a 2 nd optical disk substrate in which the reflective layer and the recording layer are laminated in the stated order on the same substrate as described above (hereinafter, such a laminate or laminated structure is sometimes referred to as a "reverse laminate" or a "reverse laminated structure"), applying a photocurable resin to each optical disk substrate, and then bonding the application surfaces to each other to cure the photocurable resin. In the 2 recording layers, optical information is recorded and read using recording/reading light incident from the 1 st optical disc substrate side. In the method of bonding 2 optical disk substrates, the step of transferring the uneven shape of the transparent stamper is not required as in the 2P method, and it is considered that excellent productivity and cost reduction can be achieved.

In the above-described inversely laminated structure, it is known to provide a layer called a "barrier layer" between the recording layer and the photocurable resin (see patent documents 1 and 2).

Patent document 1: japanese patent laid-open No. 2000-311384 (paragraphs [0052], [0053], example 2)

Patent document 2: japanese patent laid-open No. 2002-373451 (paragraphs [0034], [0035], examples)

Disclosure of Invention

In an optical recording medium having a recording layer containing an organic dye, there is a problem that it is desired to further suppress the occurrence of signal crosstalk during high-speed recording. According to the studies of the present inventors, the main reason for this problem is that the thermal conductivity of the organic dye is much lower than that of the recording layer of other known inorganic recording media (e.g., DVD-RW).

That is, in the recording layer containing an organic dye, when a recording portion is formed, the dye of the recording laser beam condensed is absorbed and decomposed, and the optical constant is changed, or the film thickness of the portion is decreased, and the pressure is increased, and the periphery of the recording layer exposed to high temperature is changed, and the like. In this case, since heat diffusion is hard to occur, and in particular, heat dissipation in the in-plane direction of the recording layer is hard to occur, the recording portion tends to expand to the adjacent track portion, and signal crosstalk tends to increase when recording is performed on 2 or more tracks. It is considered that these trends cause a phenomenon that it is difficult to obtain good jitter (jitter).

In addition, since the recording pulse is shortened at the time of high-speed recording, it is necessary to decompose the dye by using a recording laser beam having a higher energy than that at the time of low-speed recording. As a result, the recording layer is exposed to a higher temperature than in the case of low-speed recording, and thus an increase in signal crosstalk tends to be significant.

Such signal crosstalk may be observed to occur in the dual-layer optical recording medium manufactured by the 2P method, but particularly in the dual-layer optical recording medium formed by a method of bonding 2 optical disk substrates, such signal crosstalk is clearly observed to occur in a recording layer located inside an incident surface on which reading/writing light is recorded (hereinafter, this may be referred to as "2 nd-layer recording layer"). As described above, the 2 nd recording layer of the two-layer type optical recording medium formed by the method of bonding 2 optical disk substrates is provided on the reverse laminate in which the reflective layer and the recording layer are laminated on the substrate. In such a counter laminate, when optical information is recorded in the land portion of the substrate, the thickness of the recording layer in the land portion needs to be increased in order to ensure the recording modulation degree. In this case, since the adjacent tracks of the recording portion are groove portions of the substrate, the recording layer film thickness tends to become thicker than the inter-groove portions. Therefore, the recording layer film thickness of the groove portion becomes thick, and accordingly the recording mark tends to be laterally enlarged, and the signal crosstalk tends to increase. Such a difference in recording film thickness between the groove portion and the land portion is likely to occur when the organic dye solution is applied.

In the case of the 2 nd optical disc substrate provided inside the incident surface for recording/reading light in the dual-layer type optical recording medium, the depth of the guide groove is set to be shallower than the groove of the related art in order to secure the reflectance of the recording/reading light. Therefore, the physical barrier effect of the guide groove becomes small, and excessive deformation due to flow deformation of the substrate resin or the like at the time of recording is easily generated, and signal crosstalk is easily increased.

The present invention has been made to solve the above problems.

That is, an object of the present invention is to provide an optical recording medium including a counter laminated structure that can obtain good recording and reading characteristics in high-speed recording.

Another object of the present invention is to provide a dual-layer type optical recording medium having a 2 nd recording layer which is particularly excellent in high-speed recording.

As a result of intensive studies, the present inventors have found that the above problems can be effectively solved by forming a barrier layer provided between a recording layer and a transparent resin layer from a material having high thermal conductivity as a bulk (bulk) and by reducing the thickness of the barrier layer to a very small thickness.

The present inventors have also found that various problems required for the 2 nd recording layer can be solved and sufficient light resistance can be maintained by including a specific dye particularly excellent in high-speed recording in the 2 nd recording layer of a dual-layer type optical recording medium, and have completed the present invention.

That is, the gist of the present invention resides in an optical recording medium having a reflective layer, a recording layer containing a dye, and a transparent resin layer in the stated order on a substrate, wherein a barrier layer is provided between the recording layer and the resin layer, a thermal conductivity M of a material for the barrier layer at 300K as a bulk is 70W/M · K or more, and a film thickness t of the barrier layer is less than 5nm (claim 1).

Another gist of the present invention resides in an optical recording medium comprising a 1 st reflective layer, a 1 st recording layer containing a dye, a transparent resin layer, a 2 nd reflective layer containing a dye, a 2 nd recording layer, and a 2 nd substrate in the stated order on a 1 st substrate, wherein the 1 st recording layer (second-layer 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 the dye (claim 8),

(in the general formula (1),

R¹representing a hydrogen atom or as CO₂R³An ester group represented by, herein, R³Represents a linear or branched alkyl group, or a cycloalkyl group,

R²to representA linear or branched alkyl group, a cyclic or branched alkyl group,

X¹and X²At least any one of them represents NHSO₂Y represents a linear or branched alkyl group substituted by at least 2 fluorine atoms, while the remaining groups represent hydrogen atoms,

R⁴and R⁵Each independently represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkoxy group,

R⁶、R⁷、R⁸and R⁹Each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms,

furthermore, H⁺From the NHSO described above₂The Y group is detached to form NSO₂Y^-A (negative) group in which the azo compound represented by the above general formula (1) forms a coordinate bond with a metal ion. )

In another aspect of the present invention, the transparent resin layer further includes an intermediate layer having a guide groove (hereinafter, this may be referred to as a "2P layer") in the two-layer type optical recording medium in which the guide groove is formed in the intermediate layer by the 2P method.

Thus, according to the present invention, an optical recording medium which can obtain good recording and reading characteristics in high-density and high-speed recording can be obtained.

Drawings

Fig. 1(a) is a sectional view schematically showing the structure of an optical recording medium according to embodiment 1 of the present invention, and fig. 1(b) is a sectional view schematically showing the structure of an optical recording medium according to embodiment 2 of the present invention.

Fig. 2 is a graph showing the relationship between the thermal conductivity of the bulk material of the barrier layer and Δ jitter in the optical recording medium counter-laminate produced in experimental example 1.

Fig. 3 is a graph showing the relationship between the film thickness of the barrier layer and Δ jitter in the optical recording medium reverse laminate produced in experimental example 2.

Fig. 4 is a graph showing the relationship between the material of the barrier layer and ST (%), MT (%), in the optical recording medium reverse laminated body produced in experimental example 1.

Fig. 5 is a cross-sectional view schematically showing the structure of an optical recording medium according to embodiment 3 of the present invention.

Fig. 6(a) is a graph showing the relationship between jitter and asymmetry in the optical recording medium relationship graph 6 (b).

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.

Description of the symbols

11 reverse laminate

12 positive laminate

100, 200, 300 optical recording medium

101, 308 base plate (1)

102, 306 reflective layer (1)

103, 305 recording layer (1)

104, 204 barrier layer

105, 205 transparent resin layer

304 transparent resin layer (2P layer)

106 protective coating

107, 303 reflecting layer (2)

108, 302 recording layer (2)

109, 301 base plate (2)

110, 210, 310 laser

201 substrate

202 reflective layer

203 recording layer

307 bonding layer

Detailed Description

The best mode for carrying out the present invention (hereinafter, simply referred to as "embodiment of the invention" where appropriate) will be described. The present invention is not limited to the following embodiments, and can be implemented by being variously modified within the scope of the gist thereof.

[ basic concept 1 of the invention ]

The 1 st optical recording medium of the present invention has a reflection layer, a recording layer containing a dye, and a transparent resin layer as basic components in the order described above on a substrate. Further, a barrier layer is provided between the recording layer and the resin layer as necessary.

In addition, the present invention is characterized in that a material having high thermal conductivity is used for the barrier layer. By using a material having high thermal conductivity for the barrier layer in this manner, heat can be released from the recording layer of the anti-laminate during recording, excessive deformation during recording can be suppressed, and signal crosstalk can be reduced.

In addition, the present invention is characterized in that the thickness of the barrier layer is set to be less than 5 nm. By reducing the film thickness in this manner, it is possible to suppress the attenuation of the recording light even if a metal film or an alloy film having a large attenuation coefficient is used as the barrier layer, and it is possible to obtain good recording characteristics without lowering the recording sensitivity of the inversely laminated structure. Further, as described later, it is considered that a good recording edge portion can also be formed.

The signal crosstalk reduction effect in the present invention is remarkably exhibited in the following cases: the groove shape of the substrate for the reverse laminate, particularly the groove depth, is set to about 1/5 or less of the groove depth of a normal front laminate or 2 nd optical disk substrate. That is, in order to secure the reflectance of the optical disk and suppress the decrease in recording sensitivity, the effect of the present invention can be remarkably exhibited when the groove of the substrate of the reverse laminate is made shallow.

This is because, when the groove depth is shallow, it is difficult to obtain a physical shield by the groove walls of the substrate, that is, it is difficult to obtain a barrier effect by a substance such as a dye or a resin of the substrate moving during recording by flowing, and therefore, excessive deformation of the recording portion occurs during recording, and the signal crosstalk becomes very large. Therefore, the present invention is preferably applied to a counter laminate using a substrate having a shallower groove than the related art.

The relationship between the thermal conductivity and the recording characteristics of the barrier layer can also be confirmed from fig. 2 of [ experimental example 1] described later. Here, the jitter when recording on 2 or more tracks and reading signals recorded on the tracks on both sides adjacent to each other is referred to as MT (%). The jitter obtained by reading a portion recorded in only one track in a state where no recording is made in the adjacent track is referred to as ST (%). MT (%) includes the influence of signal crosstalk, whereas ST (%) does not include the influence of signal crosstalk.

Further, Δ jitter is a difference between the above MT (%) and ST (%), and the larger the value is, the larger the signal crosstalk is. The value of Δ jitter is preferably 2% or less. This is because, in the case where Δ jitter is greater than 2%, even if it is good when ST (%) is 7%, for example, MT (%) is greater than 9%, which is not preferable.

Based on the above, as can be seen from FIG. 2, in the examples, the thermal conductivity was 70W/m.K or more and less than 2%, and good characteristics were obtained.

On the other hand, as can be confirmed from table 3 of [ experimental example 2] described later, it is found that in the barrier layer having high thermal conductivity, the thickness of the barrier layer is limited to 5nm, and it is difficult to improve the jitter. One of the reasons for this is that the recording sensitivity is deteriorated due to attenuation of the intensity of the recording light due to the increased film thickness. Further, it is considered that the film thickness is increased to cause morphological deterioration of the film. The morphology of the film can be adjusted to some extent by the film formation conditions of thermal spraying, the composition of the film, and the like.

In addition, in the optical recording medium of the present invention, in the above-described basic configuration, the 2 nd reflective layer, the 2 nd recording layer, and the transparent substrate are further provided in this order on the side opposite to the counter laminate side of the transparent resin layer in contact with the counter laminate, whereby a multilayer optical recording medium can be developed.

[ embodiment 1]

Fig. 1(a) is a cross-sectional view schematically showing the structure of an optical recording medium according to embodiment 1 of the present invention. Fig. 1(a) shows a dual-layer optical recording medium 100, which includes an optical disc substrate (a reverse laminated body 11) in which a reflective layer and a recording layer are laminated on a transparent substrate, and an optical disc substrate (a front laminated body 12) in which a recording layer and a reflective layer are laminated in this order on a transparent substrate.

As shown in fig. 1(a), the optical recording medium 100 includes a disk-shaped light-transmissive substrate (1)101 having grooves, lands, or prepits formed thereon as a counter laminate 11; a reflective layer (1)102 provided on the incident surface side of the laser beam 110 of the substrate (1) 101; a recording layer (1)103 containing a coloring matter; and a barrier layer 104. The positive laminate 12 further includes a disk-shaped light-transmitting substrate (2)109 on which grooves, lands, or prepits are formed; a recording layer (2)108 containing a pigment provided on a substrate (2) 109; a translucent reflective layer (2)107 for attenuating the energy of laser light 110 incident from the substrate (2)109 side; a protective coating 106 disposed on the reflective layer (2) 107. The transparent resin layer 105 is laminated between the reverse laminate 11 and the front laminate 12 so that the barrier layer 104 and the protective coating layer 106 face each other, thereby constituting the dual-layer optical recording medium 100. In the recording layer (1)103 and the recording layer (2)108, optical information can be recorded and read by the laser beam 110 incident from the substrate (2)109 side of the positive laminate 12.

[ reflection laminate ]

Next, each layer of the reverse laminate 11 will be described. As described above, the multilayer body 11 is composed of the substrate (1)101, the reflective layer (1)102, the recording layer (1)103, and the barrier layer 104 laminated on the substrate (1)101 (hereinafter, the reflective layer (1)102, the recording layer (1)103, and the barrier layer 104 are sometimes collectively referred to as "L1 layer").

< substrate (1) >

The material constituting the substrate (1)101 is preferably light-transmitting and has a small birefringence, and is excellent in optical characteristics. Further, it is preferable that the composition is easy to be injection molded and has excellent moldability. Further, it is also preferable that the hygroscopicity is small. It is further preferable that the optical recording medium 100 has shape stability so as to have a certain degree of rigidity. Such a material is not particularly limited, and examples thereof include acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and glass. In addition, a substrate or the like in which a resin layer made of a radiation curable resin such as a photocurable resin is provided on a substrate such as glass may be used. Among these, polycarbonate is preferable from the viewpoints of high productivity such as optical properties and moldability, low cost, low moisture absorption, shape stability, and the like. In addition, amorphous polyolefins are preferred in terms of chemical resistance, low hygroscopicity, and the like. In addition, a glass substrate is preferable in view of high-speed response and the like.

Further, since the substrate (1)101 is not necessarily light-transmissive, a substrate made of an appropriate material may be provided in order to improve mechanical stability and increase rigidity. Examples of such a material include Al alloy substrates such as Al — Mg alloys containing Al as a main component; an Mg alloy substrate such as an Mg-Zn alloy containing Mg as a main component; a substrate of silicon, titanium, ceramic, paper, or the like, or a combination of these.

The groove depth of the guide groove portion of the substrate (1)101 constituting the reverse laminate 11 is usually λ/100 or more, preferably 2 λ/100 or more, and more preferably 2.2 λ/100 or more, with the recording/reading wavelength λ. For example, when the wavelength λ of the recording/reading light (recording/reading wavelength) is 660nm, the groove depth of the substrate (1)101 is usually 6.6nm or more, preferably 13nm or more, and more preferably 14.5nm or more.

Further, the upper limit of the groove depth of the substrate (1)101 in the reverse laminate 11 is preferably set to 110nm 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 beam 110 incident on the recording layer (1)103 through the substrate (2)109 and the transparent resin layer 105 are weakened by the recording layer (2)108 and the reflective layer (2)107, and the reflectance is lowered, and therefore 7 λ/100 or less becomes a preferable upper limit of the groove depth. For example, when the recording/reading wavelength λ is 660nm, the groove depth of the substrate (1)101 is preferably 46.2nm or less. More preferably 6 λ/100 or less.

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

The groove width of the substrate (1)101 in the inverted laminate 11 is generally T/10 or more, preferably 2T/10 or more, and more preferably 3T/10 or more, assuming that the track pitch is T. However, it is usually 8T/10 or less, preferably 7T/10 or less, and more preferably 6T/10 or less. When the groove width of the substrate (1)101 is within this range, good tracking can be performed and sufficient reflectance can be obtained. For example, when the track pitch is 740nm, the groove width of the substrate (1)101 is usually 74nm or more, preferably 148nm or more, and more preferably 222nm or more. The upper limit of the substrate (1)101 is usually 592nm or less, more preferably 518nm or less, and still more preferably 444nm or less. Further, in the present specification, the "groove width" of the substrate refers to a groove width at half the depth of the maximum depth of the groove (i.e., half-value width).

The substrate (1)101 preferably has a certain thickness, and the thickness of the substrate (1)101 is preferably 0.3mm or more in general. However, it is usually 3mm or less, preferably 1.5mm or less.

< reflective layer (1) >

The material constituting the reflective layer (1)102 of the reverse laminate 11 is not particularly limited, and for example, any one of metals and metalloids such as 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, and rare earth metals may be used alone, or any two or more thereof may be alloyed. Among these, Au, Al, and Ag are preferable, and particularly, a metal material containing 50% or more of Ag is preferable in terms of low cost and high reflectance.

The reflective layer (1)102 is preferably an alloy containing Ag as a main component and 0.1 to 15 atomic% of at least one element selected from the group consisting of Ti, Zn, Cu, Pd, Au and rare earth metals. When two or more elements among Ti, Bi, Zn, Cu, Pd, Au and rare earth metals are contained, the contents thereof may be 0.1 to 15 atomic% respectively, but the total content thereof is preferably 0.1 to 15 atomic%.

The alloy composition of the reflective layer (1)102 is preferably 0.1 to 15 atomic% of at least one element selected from the group consisting of Ti, Bi, Zn, Cu, Pd, and Au, and optionally 0.1 to 15 atomic% of at least one rare earth element. Among rare earth metals, neodymium is particularly preferred. Specifically, AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, AgBi, AgBiNd, etc. The composition ratio of the alloy used in the present embodiment is within the above range.

The reflective layer (1)102 made of Au alone is preferable because it has small crystal grains and excellent corrosion resistance. Further, a layer containing Si may also be used as the reflective layer (1) 102. Further, a multilayer film in which a low refractive index thin film and a high refractive index thin film are alternately laminated with a material other than a metal may be used as the reflective layer.

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

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

< recording layer (1) >

The recording layer (1)103 in the counter laminate 11 usually contains a dye having the same sensitivity as that of a recording layer used for a single-sided recording medium (for example, CD-R, DVD-R, DVD + R). Such a dye preferably has a maximum absorption wavelength λ max in the visible to near-infrared region of about 350 to 900nm and is a dye compound suitable for recording with a blue to near-microwave laser. Among them, pigments suitable for recording by the following laser beams are more preferable: generally, it is used for a near infrared laser having a wavelength of about 770 to 830nm (for example, 780nm or 830nm) such as a CD-R, a red laser having a wavelength of about 620 to 690nm (for example, 635nm, 660nm or 680nm) such as a DVD-R, a so-called blue laser having a wavelength of 405nm or 515nm, or the like. In addition, phase change type materials may also be used.

The dye used for the recording layer (1)103 is not particularly limited, but an organic dye material is generally used. Examples of the organic coloring matter material include macrocyclic azaannulene-based coloring matters (phthalocyanine coloring matters, naphthalocyanine coloring matters, porphyrin coloring matters, etc.), pyrromethene-based coloring matters, polymethine-based coloring matters (cyanine coloring matters, merocyanine coloring matters, squarylium coloring matters, etc.), anthraquinone-based coloring matters, azulenium-based coloring matters, metal-containing azo-based coloring matters, metal complex indoaniline-based coloring matters, etc. Among these, the metal-azo-containing pigment is preferable because of its excellent recording sensitivity, durability and light resistance. One kind of these pigments may be used alone or two or more kinds may be used in combination.

The recording layer (1)103 also contains other components than the dye.

For example, the recording layer (1)103 may contain a transition metal chelate compound (e.g., acetylacetone chelate, diphenyldithiol, salicylaldoxime, dithiol- α -diketone, etc.) as a singlet oxygen quencher for improving the stability or light resistance of the recording layer, or the recording layer (1)103 may contain a recording sensitizer (upstream sensitivity) such as a metal-based compound for improving the recording sensitivity. The metal-based compound is a compound obtained by including a metal such as a transition metal in the compound in the form of an atom, an ion, a cluster, or the like, and examples thereof include organic metal compounds such as ethylenediamine-based complexes, azomethine-based complexes, phenylhydroxylamine-based complexes, phenanthroline-based complexes, dihydroxyazobenzene-based complexes, dioxime-based complexes, nitrosoaminophenol-based complexes, pyridyltriazine-based complexes, acetylacetone-based complexes, metallocene-based complexes, and porphyrin-based complexes. The metal atom is not particularly limited, however, a transition metal is preferable.

Further, a binder, a leveling agent, a defoaming agent, or the like may be used in combination as necessary for the recording layer (1) 103. Preferred examples of the binder include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resins, acrylic resins, polystyrene resins, urethane resins, polyvinyl butyral, polycarbonate, and polyolefin.

However, in the recording layer (1), a combination with a specific dye is preferable in order to further improve high-speed recording characteristics. As will be described later.

The film forming method of the recording layer (1)103 is not particularly limited, and a common thin film forming method such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spin coating method, a dipping method, and the like can be generally mentioned. Further, the vacuum deposition method is preferable in that a uniform recording layer can be obtained.

In the case of film formation by spin coating, the rotation speed is preferably 10 to 15000 rpm. After the spin coating, a heating treatment is generally performed to remove the solvent. The coating solvent in the case of 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 is not particularly limited as long as it is a solvent that does not attack the substrate. Examples thereof include ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolve 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, t-butylcyclohexane, and cyclooctane; perfluoroalkyl alcohol solvents such as tetrafluoropropanol, octafluoropentanol, and hexafluorobutanol; and hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.

The heat treatment for removing the solvent is usually carried out at a temperature slightly lower than the boiling point of the solvent used, and is usually carried out in the range of 60 to 100 ℃ from the viewpoint of removing the solvent and carrying out the treatment by a simple apparatus. The method of the heat treatment is not particularly limited, and for example, a method of applying a solution containing a coloring matter to form a film so as to form the recording layer (1)103 on the substrate (1)101, and then holding the film at a predetermined temperature for a predetermined time (generally 5 minutes or more, preferably 10 minutes or more, and further generally 30 minutes or less, preferably 20 minutes or less) is given. In addition, the substrate (1)101 may be heated by irradiating infrared rays or far infrared rays for a short time (for example, for 5 seconds to 5 minutes).

In the case of the vacuum vapor deposition method, this is performed by: for example, the recording layer components such as the organic dye and various additives added as needed are put in a crucible provided in a vacuum vessel, and the inside of the vacuum vessel is evacuated to 10 degrees by an appropriate vacuum pump^-2～10^-5After the Pa level, the crucible is heated to evaporate the recording layer component, thereby evaporating the recording layer component onto the substrate placed opposite to the crucible.

The thickness of the recording layer (1)103 of the reverse laminate 11 is usually 40nm or more, preferably 50nm or more, but usually 150nm or less, preferably 100nm or less. If the thickness of the recording layer (1)103 is in this range, it is possible to suppress a decrease in sensitivity while securing a sufficient recording signal amplitude. Further, if the thickness of the recording layer (1)103 is too large, the sensitivity may be lowered.

< Barrier layer >

The barrier layer 104 is provided on the reverse laminate 11. In order to prevent the recording layer (1)103 from being contaminated or dissolved by the component exuded from the transparent resin layer 105, the barrier layer 104 is generally provided between the recording layer (1)103 and the transparent resin layer 105.

In the present invention, in addition to the above-described object, the barrier layer 104 is used to secure heat dissipation on the recording layer 103 and suppress signal crosstalk in high-speed recording. Therefore, in the present invention, a very thin film is made using a material having a high bulk thermal conductivity without using a thick film which is known in the art for an alloy or a dielectric, whereby excellent characteristics can be obtained.

First, as described above, the bulk thermal conductivity is drastically improved within the limit of 70W/m.K. As is clear from FIG. 2 summarizing a part of the data of examples described later, if the thermal conductivity is further 90W/m.K or more, particularly if Si and C, which are semiconductors, are removed, Δ jitter is less than 1%, and excellent characteristics can be obtained. The upper limit of the thermal conductivity of the barrier layer 104 in the present invention is not necessarily limited, and it is considered that the thermal conductivity is sufficient as long as 700W/m.K. It is considered that Si, C, and the like, which are single substances as semiconductors, exhibit better characteristics by increasing conductivity through alloying, use of additives, and the like.

On the other hand, when the film thickness of the barrier layer 104 is larger than 5nm, as described above, the characteristics are seen to be significantly deteriorated. Therefore, the thickness of the barrier layer 104 is set to be generally less than 5nm, preferably 4nm or less, and more preferably 3.5nm or less. On the other hand, the lower limit of the film thickness is usually 0.5nm or more, more preferably 1nm or more, and still more preferably 1.5nm or more. Taking Mo and Co as examples of the elements listed in Table 2 of [ example ] given later, it is understood that, as shown in FIG. 3, although the optimum values differ depending on the thermal conductivity, in this range, Δ jitter, ST (%), and MT (%) are stable and have good values.

Further, it is also considered that, by using a thin film of a material having a ductile high thermal conductivity for the barrier layer 104, it is possible to accurately track changes due to the decomposition of the pigment of the recording layer, and the jitter becomes better, unlike a vitreous dielectric film having a low thermal conductivity, since the thin film is made.

As the material of the barrier layer 104 of the present invention, a simple substance or an alloy of Mg, Cr, Mn, Fe, Ni, Zn, Ru, Rh, Pd, In, Os, Ir, Pt, Mo, Al, W, Co, Cr, Cu, Ag, Au is preferable. More preferably, Cu, Al, Au, Co, Cr, Mo, Si, W, C, Ag, or an alloy thereof. More preferably, the metal element is a simple substance 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 the "main component" of a certain metal element means that the metal element accounts for 50 wt% or more of the alloy composition. In particular, Mo, W, and Cu are excellent in characteristics, and Co and Cr are excellent in sensitivity and jitter in both 4-fold and 8-fold recording. In addition, it is possible to form the barrier layer 104 having good recording characteristics and weather resistance by alloying Ag, Al, Si, and C, or by improving a photocurable resin.

As a result of the studies by the present inventors, it has been found that even when the above-mentioned materials are used to form the barrier layer 104, a sufficient barrier effect can be obtained such that the recording layer does not dissolve in the photocurable resin in contact therewith. Further, it is considered that the barrier layer 104 is a dense and smooth film and is effective. This is because, when density is dense in a film such as an island structure, grain boundaries are generated or grain sizes are increased due to changes in temperature and humidity such as a high temperature and high humidity test, which causes an increase in noise and an increase in film defects.

The dense and smooth structure of the barrier layer 104 is considered to depend on the conditions under which the barrier layer 104 is formed, in addition to the constituent components and the composition thereof. The barrier layer 104 is formed by a common film formation method such as a vacuum deposition method or a thermal spraying method, but among them, it is preferably formed by a thermal spraying method. Here, in the case of the thermal spraying method, for example, the target is subjected to pre-thermal spraying before thermal spraying in order to obtain a barrier layer having a dense and smooth structure. The time for the preliminary sputtering is set longer than the usual time, and the sputtering is started after removing the water adsorbed on the target or the surface oxide layer as much as possible, or the sputtering is performed by setting the argon pressure as low as possible, or the like, and the conditions for the sputtering are preferably adjusted to an appropriate range. Further, since the barrier layer 104 of the present invention is a thin film, it is considered that the surface state of the film of the barrier layer 104 affects recording. Therefore, a dense and smooth film structure is obtained, and thus the recording characteristics can be improved.

In the present specification, as the "thermal conductivity", a thermal conductivity value at 300K described in "debye temperature and thermal conductivity" on page 117 of "volume for entry to door of solid physics" (6 th edition) written in キツテル is used. The values of thermal conductivity of the main materials described in the above table are shown in table 1 below.

TABLE 1

	Thermal conductivity at 300K (W/m. K)		Thermal conductivity at 300K (W/m. K)
				C	129	Ru	117
Mg	156	Rh	150
				Al	237	Pd	72
Si	148	Ag	429
				Cr	94	Cd	97
Fe	80	In	82
				Co	100	Sn	67
Ni	91	W	174
				Cu	401	Os	88
Zn	116	Ir	147
				Mo	138	Pt	72
Ti	22	Au	317

Several methods for measuring thermal conductivity with an actual thin film have been reported, but these experiments require a special apparatus (for example, an apparatus for measuring a thermal constant of a thin film by an optical alternating current method) or a method for preparing a special sample. Therefore, these methods have not been generally used, and often require excessive labor for measurement. Therefore, in the present invention, the above-described general bulk thermal conductivity (bulk thermal conductivity) is used.

In the case where the barrier layer 104 is composed of two or more compositions of an alloy or the like, as described below, the thermal conductivity of the bulk of each composition is multiplied by the ratio of the compositions thereof, and the value of the thermal conductivity obtained from the obtained value is determined as the thermal conductivity as the bulk of the material for the barrier layer 104. For example, the thermal conductivity of an alloy composed of 95 atomic% of Al and 5 atomic% of Cr was measured as 237 × 0.95+94 × 0.05 ═ 229.9W/m · K from the thermal conductivity of the bulk of Al (237W/m · K) and the thermal conductivity of the bulk of Cr (94W/m · K). In this manner, the thermal conductivity of the block of, for example, 3-or 4-membered system is also calculated.

The thermal conductivity of a material not described in "Debye temperature and thermal conductivity" in Table 1 on page 117 of "volume for entry to solid Physics" (6 th edition) written by キツテル described above is determined from a database in which the latest physical property values can be obtained, such as WWW site of the Internet (http:// www.als.cojp/thermal/db/prop _ met. htm, etc.), or "Table of thermal conductivity" given in "Charactins" (pill-good), "Physics dictionary" (Pechan-kuyama).

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

[ 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 optical recording medium 100 of the present embodiment is generally made of a material having a light transmittance enough to allow the laser beam 110 incident from the substrate (2)109 side to reach the recording layer (1) 103. The transparent resin layer 105 is preferably made of a transparent resin having a glass transition temperature Tg of 150 ℃. The transparent resin layer 105 may be formed from 1 layer or 2 or more layers. It is considered that by forming the transparent resin layer using such a transparent resin, the hardness of the transparent resin layer is increased, and the jitter is improved.

The elastic modulus of the resin constituting the transparent resin layer 105 at 30 ℃ is preferably 1000MPa or more, preferably 2000MPa or more, more preferably 3000MPa or more, and further preferably 4000MPa or more. By forming the transparent resin layer 105 with a resin having an elastic modulus of 1000MPa or more, the so-called blocking effect can be further improved in recording and reading of the L1 layer (fig. 1). However, the upper limit of the elastic modulus is usually 6000MPa or less. By using a resin having an elastic modulus of 6000MPa or less, the transparent resin layer 105 can be formed into a film 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, excessive deformation reaching the adjacent track portion can be suppressed in recording of optical information on the recording layer (1)103 of the inverted laminate 11. As a result, crosstalk of signals in the optical recording medium 100 recorded at a high speed on the L1 layer is reduced, and jitter is improved. Here, "transparent" of the transparent resin layer 105 means that the transparent resin layer does not have a structure that scatters the laser light 110 incident on the optical recording medium 100.

In order to stack 2 or more recording layers and focus the layers, it is preferable that the recording layers have a certain distance therebetween. Therefore, the thickness of the transparent resin layer 105 depends on the focus servo mechanism, but is usually 5 μm or more, preferably 10 μm or more.

When the layer is too thick, it may take time to adjust the focus servo to the recording layer (1) on which the focus servo is performed through the transparent resin layer 105. Further, the moving distance of the objective lens may become longer. In addition, ultraviolet curing may take time, and productivity may be reduced. In view of the above, the transparent resin layer 105 is preferably generally 100 μm or less.

Next, a specific example of a material constituting the transparent resin layer 105 will be described.

Examples of the material constituting the transparent resin layer 105 include thermoplastic resins, thermosetting resins, electron beam curable resins, ultraviolet curable resins (including delayed curing type), and the like. The material constituting the transparent resin layer 105 is appropriately selected from these. The transparent resin layer 105 can be formed by dissolving a thermoplastic resin, a thermosetting resin, or the like in an appropriate solvent as needed to prepare a coating solution, applying the coating solution, and drying (heating). The ultraviolet curable resin may be applied as it is or dissolved in an appropriate solvent to prepare a coating solution, and then the coating solution is applied and cured by ultraviolet irradiation, thereby forming the transparent resin layer 105. These materials may be used alone or in combination.

As a method for forming the transparent resin layer 105, for example, a coating method such as a spin coating method or a casting method can be used, but among them, a spin coating method is preferable. The high-viscosity resin may be applied by screen printing or the like to form the transparent resin layer 105. As the ultraviolet-curable resin, an ultraviolet-curable resin which is liquid at 20 to 40 ℃ is preferably used. This is because the coating can be performed without using a solvent, and therefore, the productivity is good. Further, the viscosity of the coating liquid is preferably adjusted so as to be usually 20 to 1000mPa · s.

Among the materials constituting the transparent resin layer 105, an ultraviolet curable resin is particularly preferable in view of high transparency, short curing time, and advantageous production. Examples of the ultraviolet-curable resin include a radical type ultraviolet-curable resin and a cationic type ultraviolet-curable resin, and both of them can be used.

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

As the ultraviolet-curable compound, monofunctional (meth) acrylate and polyfunctional (meth) acrylate, which are polymerizable monomer components, can be used. These components may be used alone in 1 kind, or two or more kinds may be used in combination. In the present specification, "acrylate" and "methacrylate" are collectively referred to as "(meth) acrylate".

Examples of the monofunctional (meth) acrylate include (meth) acrylates having the following groups as substituents: methyl, ethyl, propyl, butyl, pentyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone-modified tetrahydrofurfuryl, isobornyl, dicyclopentyl, dicyclopentenyl, or dicyclopentenyloxyethyl, and the like.

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

Further, di (meth) acrylate of diol obtained by adding 4 or more moles of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol, di (meth) acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol a, di (meth) acrylate or tri (meth) acrylate of triol obtained by adding 3 or more moles of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane, di (meth) acrylate of diol obtained by adding 4 or more moles of ethylene oxide or propylene oxide to 1 mole of bisphenol a, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, poly (meth) acrylate of dipentaerythritol, ethylene oxide-modified phosphoric acid (meth) acrylate, and mixtures thereof, Ethylene oxide-modified alkylated phosphoric acid (meth) acrylates, and the like.

Examples of the polymerizable monomer that can be used in combination with the polymerizable monomer include polymerizable oligomer polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, and the like.

On the other hand, as the photopolymerization initiator, a molecular cleavage type photopolymerization initiator or a hydrogen abstraction type photopolymerization initiator is preferable.

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

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

Further, a sensitizer may 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-dimethylbenzylamine, and 4, 4' -bis (diethylamino) benzophenone.

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 type, long-chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, heterocyclic type, and the like. As the epoxy resin, it is preferable to use an epoxy resin having a small 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 proportion of the cationic polymerization type photoinitiator per 100 parts by weight of the cationic ultraviolet-curable resin is in the following range: usually 0.1 part by weight or more, preferably 0.2 part by weight or more, and usually 20 parts by weight or less, preferably 5 parts by weight or less. In addition, in order to more effectively utilize the wavelength of the near ultraviolet region or the visible light region of the wavelength band of the ultraviolet light source, a known photosensitizer may be used in combination. Examples of the photosensitizer in this case include anthracene, phenothiazine, benzyl methyl ketal, benzophenone, acetophenone, and the like.

In order to improve various properties of the ultraviolet-curable resin, an antioxidant represented by a thermal polymerization inhibitor, hindered phenol, hindered amine, phosphite, or the like, a plasticizer, a silane coupling agent represented by epoxysilane, mercaptosilane, (meth) acrylic silane, or the like may be further added to the ultraviolet-curable resin as necessary. Among these substances, a substance having excellent solubility in an ultraviolet-curable compound and a substance that does not inhibit ultraviolet light transmission are selected and used.

In the transparent resin layer 105 of the optical recording medium 100 of the present embodiment, a specific method for obtaining a resin having a high elastic modulus is not particularly limited, and the following methods are generally used. 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 ultraviolet-curable resin; a method of increasing the composition of a side chain-containing polymer diol component such as polyester diol mixed with a linear polymer diol; a method of reducing the molecular weight of the side chain of an oligomer component having a hard segment as the main chain to increase intramolecular bonds; and a method of adding a predetermined amount of a crosslinking agent such as a polyisocyanate compound, an amino resin, an epoxy compound, a silane compound, or a metal chelate compound.

In particular, in order to obtain a resin having sufficient hardness, the following polyfunctional (meth) acrylate is preferably used because the crosslinking density can be increased and the shrinkage can be increased. The multifunctional (meth) acrylate is: trimethylolpropane tri (meth) acrylate, tri (meth) acrylate of triol obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane, pentaerythritol tri (meth) acrylate or pentaerythritol tetra (meth) acrylate, triol tri (meth) acrylate or tetraol tetra (meth) acrylate obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of pentaerythritol, dipentaerythritol penta (meth) acrylate or dipentaerythritol hexa (meth) acrylate, and hexaol penta (meth) acrylate or hexaol hexa (meth) acrylate obtained by adding 6 moles or more of ethylene oxide or propylene oxide to 1 mole of dipentaerythritol, and the like.

Among them, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate are more particularly preferable.

Further, norbornanedimethanol diacrylate, norbornanediethanol di (meth) acrylate, diol di (meth) acrylate obtained by adding 2 moles of ethylene oxide or propylene oxide to norbornanedimethanol, tricyclodecanedimethanol di (meth) acrylate, tricyclodecanediethanol di (meth) acrylate, diol di (meth) acrylate obtained by adding 2 moles of ethylene oxide or propylene oxide to tricyclodecanedimethanol, pentacyclodecane dimethanol di (meth) acrylate, pentacyclopentadecane diethanol di (meth) acrylate, diol di (meth) acrylate obtained by adding 2 moles of ethylene oxide or propylene oxide to pentacyclopentadecane dimethanol, diol di (meth) acrylate obtained by adding 2 moles of ethylene oxide or propylene oxide to pentacyclopentadecane diethanol, and the like are present, in particular, as the resin having a high elastic modulus, the following acrylates having a rigid cyclic structure in a crosslinked structure are also preferable: 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-methacryloyloxypropyl) hydroxypropyl isocyanurate, bis (2-methacryloyloxybutyl) hydroxybutyl isocyanurate, tris (2-acryloyloxyethyl) isocyanurate, tris (2-acryloyloxypropyl) isocyanurate, tris (2-acryloyloxybutyl) isocyanurate, tricyclo (2-acryloyloxybutyl) isocyanurate, and mixtures thereof, Tris (2-methacryloyloxyethyl) isocyanurate, tris (2-methacryloyloxypropyl) isocyanurate, tris (2-methacryloyloxybutyl) isocyanurate, and the like.

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

Further, 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.

Among the ultraviolet-curable resins, a cationic ultraviolet-curable resin which has low light scattering properties and low viscosity and can be applied by a spin coating method is particularly preferable. In addition, from the viewpoint of a large number of types, a large mixing ratio, and a large degree of freedom in composition, or from the viewpoint of inhibiting curing by oxygen when the thickness of the transparent resin layer 105 is 10 μm or more, it is not necessary to use a radical-based ultraviolet-curable resin.

[ front laminate ]

Next, each layer of the alignment layered body 12 will be explained. As described above, the positive laminate 12 is composed of the substrate (2)109, and the recording layer (2)108, the reflective layer (2)107, and the protective coating 106 laminated on the substrate (2)109 (hereinafter, the recording layer (2)108, the reflective layer (2)107, and the protective coating 106 are sometimes collectively referred to as "L0 layer").

< substrate (2) >

The substrate (2)109 of the front laminate 12 is made of the same material as the substrate (1)101 of the reverse laminate 11. However, the substrate (2)109 must have light-transmitting properties. The groove width of the substrate (2)109 is usually 2T/10 or more, preferably 3T/9 or more, with T as the track pitch. Within this range, the reflectance can be sufficiently ensured. For example, if the track pitch is 740nm, the groove width of the substrate (2)109 is usually 148nm or more, preferably 246nm or more. However, the groove width of the substrate (2)109 is usually 7T/10 or less, preferably 6T/10 or less. For example, if the track pitch is 740nm, the groove width of the light-transmitting substrate (2)109 is usually 518nm or less, preferably 444nm or less, and in this case, the groove shape transferability can be improved, which is preferable.

When λ is used as the recording/reading wavelength, the groove depth of the substrate (2)109 is preferably set to λ/10 or more, because sufficient reflectance can be secured. More preferably, it is not less than λ/8, and still more preferably not less than λ/6. For example, when the wavelength λ of the recording/reading light (recording/reading wavelength) is 660nm, the groove depth of the substrate (2)109 is usually 66nm or more, preferably 82.5nm or more, and more preferably 110nm or more. However, the upper limit of the groove depth of the substrate (2)109 is usually 2 λ/5 or less, and thus the transferability of the groove shape is good, and is preferably 2 λ/7 or less. For example, when the recording/reading wavelength is 660nm, the groove depth is usually 264nm or less, preferably 188.6nm 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 negative laminate 11. The thickness of the recording layer (2)108 of the positive laminate 12 is not particularly limited since it is different from an appropriate film thickness depending on a recording method and the like, but is usually 20nm or more, preferably 30nm or more, and particularly preferably 40nm or more in order to obtain a sufficient modulation factor. However, since light needs to be transmitted, the film thickness is usually 200nm or less, preferably 180nm or less, and more preferably 150nm or less. The thickness of the recording layer (2)108 is represented by 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 positive laminate 12 is made of the same material as the reflective layer (1)102 of the negative laminate 11. The reflection layer (2)107 of the positive laminate 12 absorbs the laser beam 110 as the recording/reading light incident from the substrate (2)109 side to a small extent, and has a light transmittance of usually 40% or more and usually needs to have a moderate light reflectance of 30% or more. For example, the reflective layer (2)107 can have an appropriate transmittance by making a metal having a high reflectance thin. Further, it is preferable to have a certain degree of corrosion resistance. Further, it is preferable to have such shielding properties: the recording layer (2)108 located below the reflective layer (2)107 is not affected by other components that leak out from the upper layer (here, the transparent resin layer 105) of the reflective layer (2) 107.

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

< protective coating layer >

The protective coating 106 of the positive laminate 12 is provided on the transparent resin layer 105 side of the reflective layer (2)107 in order to prevent oxidation, dust prevention, damage, and the like of the reflective layer (2) 107. The material of the protective coating 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, an ultraviolet curable resin, and the like. Examples of the inorganic substance include silicon oxide, silicon nitride, and magnesium fluoride (MgF)₂) Tin (IV) oxide (SnO)₂) And a dielectric body. Among them, an ultraviolet curable resin layer is preferably laminated. The thickness of the protective coating 106 is in the following range: usually 1 μm or more, preferably 3 μm or more, and usually 100 μm or less, preferably 30 μm or less, and more preferably 10 μm or less. If the thickness of the protective coating 106 does not fall within this range, the curing may be inhibited by oxygen, while if the thickness exceeds this range, the optical disk may be bent or the film thickness may be easily uneven. Further, the protective coating 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. The format for recording such information may be, for example, the format of LPP or ADIP described in the standard specification of DVD-R, DVD + R.

[ 2 nd embodiment ]

Fig. 1(b) is a cross-sectional view schematically showing the structure of an optical recording medium according to embodiment 2 of the present invention. Fig. 1(b) shows a film-surface incident type optical recording medium 200 for recording and reading optical information by recording and reading light incident from the opposite side to the substrate side. As shown in fig. 1(b), in the optical recording medium 200, a transparent resin layer 205 is further laminated on the side of the laser beam 210 incident on the reverse laminate (composed of a substrate 201, a reflective layer 202 provided on the substrate 201, a recording layer 203 laminated on the reflective layer 202, and a barrier layer 204 provided to protect the recording layer 203). The optical recording medium 200 records and reads information by a laser beam 210 irradiated from the transparent resin layer 205 side onto the recording layer 203.

The substrate 201 constituting the counter laminate is formed of the same material as the substrate (1)101 of the counter laminate 11 in the optical recording medium 100 of embodiment 1. Similarly, the same materials as those described for the reflective layer (1)102, the recording layer (1)103, and the barrier layer 104 of the anti-laminate 11 in the optical recording medium 100 according to embodiment 1 can be used for the reflective layer 202, the recording layer 203, and the barrier layer 204. The thickness of each layer is in the same range as described in the optical recording medium 100.

Further, the transparent resin layer 205 is formed using the same material as the transparent resin layer 105 in the above-described optical recording medium 100, and the elastic modulus and the thickness of the transparent resin layer 205 are adjusted to the same range as the transparent resin layer 105 in the optical recording medium 100 of embodiment 1.

In each of the above embodiments, any other layer may be provided between the layers within a range that does not impair the function as the optical recording medium 100.

[ basic concept 2 of the invention ]

Next, a description will be given below of a dual-layer type optical recording medium, which is a 2 nd optical recording medium of the present invention and is particularly suitable for high-speed recording, with the configuration of the 2 nd recording layer being the center.

The 2 nd optical recording medium of the present invention is a dual-layer optical recording medium having the following constitution: the substrate (sometimes referred to as "1 st substrate") has a 1 st reflective layer, a 1 st recording layer containing a pigment, and a transparent resin layer in the stated order, and further has a 2 nd reflective layer, a 2 nd recording layer, and a transparent substrate (sometimes referred to as "2 nd substrate") in the stated order on the transparent resin layer.

A specific example of the basic concept will be described below with reference to fig. 1(a) and 5.

That is, "substrate (1)" in fig. 1(a) and 5 corresponds to the "1 st substrate" described above.

The "reflective layer (1)" in fig. 1(a) and 5 corresponds to the "1 st reflective layer" described above.

Similarly, "recording layer (1)" in fig. 1(a) and 5 corresponds to the "1 st recording layer" described above.

The "reflective layer (2)" in fig. 1(a) and 5 corresponds to the "2 nd reflective layer".

Similarly, "recording layer (2)" in fig. 1(a) and fig. 5 corresponds to the "2 nd recording layer" described above.

The "substrate (2)" in fig. 1(a) and 5 corresponds to the "transparent substrate" or the "2 nd substrate".

The 1 st recording layer (2 nd recording layer) contains, as a dye, at least a metal-containing azo dye composed of an azo compound represented by the following general formula (1) and a Zn metal ion (hereinafter, simply referred to as "the metal-containing azo dye according to formula (1)").

(in the general formula (1),

R¹representing a hydrogen atom or as CO₂R³An ester group represented by, herein, R³Represents a linear or branched alkyl group, or a cycloalkyl group.

R²Represents a linear or branched alkyl group.

X¹And X²At least any one of them represents NHSO₂Y represents a linear or branched alkyl group substituted with at least 2 fluorine atoms, while the remaining groups represent hydrogen atoms.

R⁴And R⁵Each independently represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkoxy group.

R⁶、R⁷、R⁸And R⁹Each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.

Furthermore, H⁺From the NHSO described above₂Removal of the Y group to form NSO₂Y^-A (negative) group, whereby the azo-based compound represented by the above general formula (1) forms a coordinate bond with a metal ion. )

As R³Preferably a linear or branched alkyl group having 1 to 4 carbon atoms such as ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, sec-butyl, etc.; and cycloalkyl groups having 3 to 8 carbon atoms such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. A straight-chain alkyl group having 1 or 2 carbon atoms such as a methyl group or an ethyl group is particularly preferable because of small steric hindrance; and cycloalkyl groups having 3 to 6 carbon atoms such as cyclopentyl and cyclohexyl.

As R²Preferred examples thereof include linear alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl and hexyl groups; and branched alkyl groups having 3 to 8 carbon atoms such as isopropyl group, sec-butyl group, isobutyl group, tert-butyl group, 2-ethylhexyl group, cyclopropyl group, and cyclohexylmethyl group.

Y represents a linear or branched alkyl group substituted with at least 2 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.

As R⁴、R⁵Preferably, the alkyl group is a hydrogen atom, a straight-chain alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. As R⁴、R⁵More 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 the alkoxy group are preferably unsubstituted. As R⁴、R⁵Particularly preferred is a hydrogen atom, a methyl group, an ethyl group or a methoxy group.

R⁶、R⁷、R⁸And R⁹Each independently represents a hydrogen atom or an alkyl group having 1 or 2 carbon atoms. The use of a hydrogen atom or an alkyl group having 1 or 2 carbon atoms is preferable because the absorbance or refractive index can be easily adjusted to a predetermined value. With respect to the alkyl group having 1 or 2 carbon atoms, the hydrogen atom bonded to the carbon atom may be substituted with another substituent (e.g., 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. R is a group represented by⁶、R⁷、R⁸And R⁹Most preferred is a hydrogen atom.

The metal-containing azo pigment in the above formula (1) is considered to be: not only (i) a moderate heat dissipation amount, (ii) absorption in an appropriate wavelength band (the present inventors consider that (i) and (ii) are factors that at least contribute to the reaction of the thermal mode), but also the deactivation rate of the excited state of (iii) in the metal-containing azo pigment is large (the present inventors consider that (iii) is a factor that at least contributes to the reaction of the photon mode). As a result, the decomposition reaction of the thermal mode and the photon mode is well balanced, and jitter may be reduced and signal crosstalk may be reduced. Therefore, when the metal-containing azo dye of the above formula (1) is combined with the 2 nd layer recording layer of the two-layer type optical recording medium, a special effect is easily exerted. This is because, as described above, in the dual-layer type optical recording medium, increase in jitter and signal crosstalk tends to be significant. In the case of the anti-laminate as the 2 nd recording layer, it is preferable to make the groove depth shallower than the conventional groove depth in order to obtain sufficient reflectance. The shallow grooves are one of the causes of increased jitter or signal crosstalk. In addition, when recording is performed in the region corresponding to the land 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. The thicker film of the recording layer is another cause of increased jitter or signal cross-talk. Further, the jitter and the signal crosstalk tend to be larger as the recording speed is larger. On the other hand, in the two-layer type optical recording medium manufactured by the 2P method in embodiment 3 described later, there are cases where optical distortion or warpage occurs due to unevenness in film thickness of the 2P layer or curing shrinkage of the 2P layer. Therefore, the beam distortion of the recording laser beam or the shift of the beam moving part of the recording part may occur, which may cause an increase in jitter or signal crosstalk particularly at the time of high-speed recording. Therefore, a special effect can be obtained by including the metal-containing azo dye of the above formula (1) in the 2 nd layer recording layer (the recording layer located on the far side as viewed from the laser light incidence side) of the two-layer type optical recording medium produced by the 2P method.

The metal-containing azo dye of formula (1) is an azo dye that can have a high refractive index at the recording laser wavelength by the combination of a ligand and a metal thereof. The metal-containing azo dye of formula (1) has a heat dissipation value of at least a certain value. It is further considered that the central metal ion is formed by reacting Zn with the central metal ion²⁺In combination, the probability of radiative transitions increases when excited states are generated by the recording light, or energy shifts are induced between other moleculesAnd so on, so that the decomposition proceeds substantially without radiationless transitions and at a very high speed. That is, it is considered that the decomposition (i.e., the formation of the recording portion) of the recording layer containing the metal-containing azo dye of the above formula (1) is completed in a very short time. As a result, in the 2 nd recording layer of the dual-layer optical recording medium, it is easy to achieve good high-speed recording with reduced disturbance and less jitter or signal crosstalk in high-speed recording.

Furthermore, the effect of the reduction of the jitter can be known by, for example, widening the tolerance of the asymmetry of the jitter. Furthermore, in addition to the MT% and ST% already described, the reduction in signal crosstalk can also be seen by the widening of the above-mentioned asymmetry tolerance.

Examples of the metal-containing azo pigment of the general formula (1) include the pigments listed below.

[ embodiment 3]

Next, an embodiment of the 2 nd optical recording medium of the present invention (hereinafter, referred to as "embodiment 3 of the present invention") will be described.

Fig. 5 is a cross-sectional view schematically showing the structure of an optical recording medium according to embodiment 3 of the present invention. In the optical recording medium 300 shown in fig. 5, a recording layer (2) (2 nd recording layer) 302 containing a dye, a translucent reflective layer (2)303 (2 nd reflective layer), a transparent resin layer 304, a recording layer (1)305 containing a dye (1 st recording layer), a reflective layer (1)306 (1 st reflective layer), an adhesive layer 307, and a substrate (1)308 (1 st substrate) are provided in this order on a disk-shaped substrate (2)301 (2 nd substrate). Then, in the recording layer (2)302 and the recording layer (1)306, the laser light 310 incident from the substrate (2)109 side is used to record and read the optical information. The substrate (2)301, the recording layer (2)302, and the reflective layer (2)303 may be referred to as a "positive laminate". The recording layer (1)305 corresponds to the "layer 2 recording layer" described above.

The specific cases of the materials, the forming methods, and the like of the substrate (2)301, the recording layer (2)302, and the reflective layer (2)303 are the same as the specific cases of the substrate (2)109, the recording layer (2)108, and the reflective layer (2)107 of the optical recording medium 100 described in [ embodiment 1 ].

Next, a transparent resin layer 304 is formed on the reflective layer (2) 303. As a method of forming the transparent resin layer 304, a 2P (Photo Polymerization) method is generally used. When the guide groove is formed in the transparent resin layer 304 (which may be referred to as an "intermediate layer") by the 2P method, the procedure is generally as follows.

First, a resin material layer is formed by applying a photocurable resin material or the like which is cured by light typified by radiation such as ultraviolet rays onto the reflective layer (2) 303. Next, a stamper (stamp) having a transfer concave-convex shape (hereinafter, appropriately referred to as a "transfer concave-convex shape") is mounted thereon. Then, the stamper is peeled off after the photocurable resin material and the like are cured. In this way, the transfer concave-convex shape of the stamper is transferred to the surface of the photocurable resin, and the cured product of the photocurable resin can be used to form the transparent resin layer 304(2P layer) having the concave-convex shape (i.e., the guide groove). In this case, the depth of the guide groove may be set to be in the range of (1/100) × λ to (1/6) × λ so that a sufficient reflectance can be obtained. Further, "λ" represents a recording reading wavelength of the laser light 310.

As the stamper, for example, a stamper formed of a cyclic polyolefin or a polystyrene resin can be used.

Examples of the photocurable resin used as the material of the transparent resin layer 304 include various electron beam-curable resins and ultraviolet-curable resins described as the material of the transparent resin layer 105 of the optical recording medium 100 described in [ embodiment 1 ].

Next, a recording layer (1)305 as a 2 nd-layer 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 of the above formula (1) can be used. The metal-containing azo dye of the formula (1) may be used alone or in combination of two or more kinds at any ratio. In addition to one or two or more of the metal-containing azo pigments of the above formula (1), one or two or more of other pigments may be used in combination. The kind of the other pigment which can be used in combination with the metal-containing azo pigment of the formula (1) is not particularly limited. As an example, the same dye as that used for the recording layer (1)103 of the optical recording medium 100 described in [ embodiment 1] can be given. The details of the material, the forming method, and the like of the recording layer (1)305 other than the dye are the same as those of the recording layer (1)103 of the optical recording medium 100 described in [ embodiment 1 ].

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

Thereafter, a substrate (1)308 is provided on the reflective layer (1) 306. The specific case of the material and the like of the substrate (1)308 is the same as the specific case of the substrate (1)101 of the optical recording medium 100 described in [ embodiment 1 ]. Although the method of providing the substrate (1)308 on the reflective layer (1)306 is not particularly limited, the substrate (1)308 is generally formed on the reflective layer (1)306 by preparing a previously molded substrate (1)308 and bonding the substrate (1)308 to the reflective layer (1)306 through an adhesive layer 307, as shown in fig. 5.

The material and the like of the adhesive layer 307 are not particularly limited. Examples thereof include various curable resins similar to the transparent resin layer 105 of the optical recording medium 100 described in [ embodiment 1], various adhesives known in the art, and pressure-sensitive double-sided tapes.

When a curable resin is used, a layer (curable resin raw material layer) made of a curable resin raw material is formed on the reflective layer (1)306 by the same coating method or the like as the transparent resin layer 105 of the optical recording medium 100 described in [ embodiment 1], the substrate (1)308 is mounted thereon and pressed, and at the same time, conditions for curing the curable resin raw material are given during or after the pressing (in the case of an ultraviolet curable resin or a radiation curable resin, irradiation of ultraviolet light or radiation is performed; in the case of a thermosetting resin, heating is performed), the curable resin raw material is cured, thereby forming an adhesive layer 307 made of a curable resin, and the reflective layer (1)306 and the substrate (1)308 are bonded via the adhesive layer 307.

When an adhesive is used, the adhesive is applied to the reflective layer (1)306 by screen printing or the like, and then the substrate (1)308 is mounted thereon and pressed, thereby forming the adhesive layer 307, and at the same time, the reflective layer (1)306 and the substrate (1)308 are adhered by the adhesive layer 307.

When a double-sided adhesive tape (for example, a pressure-sensitive double-sided adhesive tape) is used, the pressure-sensitive double-sided adhesive tape is sandwiched between the reflective layer (1)306 and the substrate (1)308 and pressed, thereby forming an adhesive layer 307, and the reflective layer (1)306 and the substrate (1)308 are adhered by 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, and is usually 1 μm or more, preferably 3 μm or more, and is usually 300 μm or less, preferably 100 μm or less.

While the optical recording medium 300 according to embodiment 3 has been described above, the embodiments of the present invention are not limited thereto, and may be implemented with any modifications.

For example, other arbitrary layers may be provided between the layers of the optical recording medium 300. Examples of the other layers include a protective coating layer provided between the reflective layer (2)303 and the transparent resin layer 304, and a barrier layer provided between the transparent resin layer 304 and the recording layer (1) 305. The specific cases of the materials, the formation methods, and the like of the protective coating layer and the barrier layer are the same as those of the protective coating layer 106 and the barrier layer 104 of the optical recording medium 100 described in [ embodiment 1 ].

Examples

Hereinafter, embodiments of the present invention will be described in more detail based on examples (experimental examples). The embodiments of the present invention are not limited to the following examples (experimental examples) as long as the embodiments do not exceed the gist thereof.

[ Experimental conditions ]

In experimental examples 1, 2 and 4 described below, a two-layer type optical recording medium having a reverse laminate (an optical recording medium having a configuration shown in fig. 1 (a)) was prepared in the following manner, and MT (%) and ST (%) of optical information recorded on a recording layer (1) constituting the reverse laminate were measured.

[ production of optical recording Medium ]

< preparation of reverse laminate >

First, a substrate (1) having a diameter of 120mm and a thickness of 0.60mm was formed by injection molding polycarbonate using a Ni stamper having grooves formed in the surface thereof, wherein the grooves having a pitch of 0.74 μm, a width of 340nm and a depth of 28nm were formed in the substrate (1). Then, a reflection layer (1) is formed on the substrate (1) by forming an Ag-Bi-Nd alloy into a film having a thickness of 80nm by a sputtering method. Next, as an organic dye compound, a tetrafluoropropanol solution (concentration 2 wt%) of a mixture of a dye a and a dye B each represented by the following chemical formula (dye a: dye B: 50 wt%) was prepared, and the solution was dropped on the reflective layer (1), followed by spin coating and drying at 70 ℃ for 30 minutes to form a recording layer (1). The film thickness of the recording layer (1) at the groove portion of the substrate (1) (the groove portion of the inverted laminate in fig. 1(a), i.e., the recording layer film thickness of the portion distant from the incident laser light) was about 70nm, and the film thickness of the recording layer (1) at the land portion of the substrate (1) (the land portion of the inverted laminate in fig. 1(a), i.e., the recording layer film thickness of the portion close to the incident laser light) was about 60 nm. The OD value of the recording film was 1.20.

Pigment A

Pigment B

Next, after the recording layer (1) was formed, barrier layers having respective compositions described in table 2 of [ experimental example 1] described later were formed on the recording layer (1) as soon as possible by a thermal spraying method. The sputtering time was adjusted so that the barrier layer thickness became 2 nm. Before the thermal spraying of the barrier layer, the above-mentioned preliminary thermal spraying is performed. Thus, the optical disk 1 of the reverse laminate is prepared.

< preparation of Positive laminate >

A substrate (2) made of polycarbonate having guide grooves with a depth of 160nm, a width of 360nm and a track pitch of 740nm was prepared, and a mixture of the dye a as the metal-containing azo dye and the dye C as the metal-containing azo dye represented by the following formula (dye a: dye C: 10 wt%: 90 wt%) was dropped on the surface of the substrate (2) on which the guide grooves were formed in a tetrafluoropropanol solution (concentration: 2 wt%) and was spin-coated, and then dried at 70 ℃ for 30 minutes to form a recording layer (2). The thickness of the recording layer (2) (the thickness of the recording layer in the groove of the positive laminate in FIG. 1 (a)) was about 80 nm. Next, an Ag-Bi alloy (Bi: 1.0 atomic%) was formed into a film on the recording layer (2) by sputtering to a thickness of 17nm, thereby forming a reflective layer (2). Further, an ultraviolet curable resin (a radical ultraviolet curable resin SD347 manufactured by Dainippon インキ Co., Ltd.) was spin-coated on the reflective layer (2) and cured to form a protective coating having a thickness of 3 μm to 4 μm, thereby preparing an optical disc 2 of a positive laminate.

Pigment C

< production of Dual-layer type optical recording Medium >

Resin a (a radical ultraviolet curable resin manufactured by japan インキ co., ltd.: elastic modulus 4000MPa (30 ℃), glass transition temperature Tg 174 ℃) was coated on the barrier layer of the optical disk 1 (the reverse laminate prepared by the above-described method), and the spin coating rotation speed was adjusted so that the film thickness became 23 μm. Further, the resin A was applied to the protective coating layer of the optical disk 2 (positive laminate), and the spin-coating rotation speed was adjusted so that the film thickness became 23 μm. Next, the optical disc 1 and the optical disc 2 each coated with the resin a were stacked so that the surfaces coated with the resin a were opposed to each other, and then, the substrate (2) side of the optical disc 2 (positive laminate) was irradiated with ultraviolet rays to cure the resin a and form a transparent resin layer made of the resin a, thereby producing a two-layer type optical recording medium.

The elastic modulus and the glass transition temperature Tg of the resin A were measured using a dynamic viscoelasticity tester (manufactured by レオバイブロン, DDV シリ - ズ) under conditions of a measurement frequency of 3.5Hz and a temperature rise rate of 3 ℃/min.

[ Condition for high-speed recording of optical information onto an optical disk 1 (reverse laminate) ]

The conditions for high-speed recording of optical information on the optical disc 1 as the opposite laminate are as follows.

As an evaluation machine, DDU-1000 (wavelength 662nm, number of apertures of objective lens NA 0.65) manufactured by パルステツク was used.

The recording speed was set to 2.4 times the speed of the DVD (linear velocity 9.2 m/s).

As a recording pulse strategy, DVD + Recordable Dual Layer 8.5Gbyte basic Format Specifications version 1.1 was followed.

The recording power was set to 17mW to 25 mW.

Jitter (data-to-clock jitter) measurements are performed while reading at 1 x speed.

[ evaluation of MT, ST, Δ jitter ]

Since a normal optical disc product performs recording without empty tracks, MT (%) is a value reflecting the signal quality of the optical disc. The MT (%) is generally required to be 13% or less, preferably 10% or less, and more preferably 9% or less. If it exceeds 13%, the error tends to increase.

The ST (%) is preferably 10% or less, more preferably 9% or less, and still more preferably 8% or less. In addition, no matter how the conditions such as the film thickness of the barrier layer and the recording strategy are changed, if ST (%) is not less than 10%, the barrier layer can be judged to be an unsuitable material.

The difference between ST (%) and MT (%), i.e., Δ jitter, is preferably 2% or less, more preferably 1.6% or less, and still more preferably 1% or less. If it is larger than the above value, MT (%) may be larger than 13%.

[ Experimental example 1]

In the above-described procedure, a two-layer type optical recording medium (a two-layer type DVD-R optical disc) was produced, in which 2nm barrier layers made of the materials shown in table 2 below were provided on the optical disc 1. On the optical disk 1 of the obtained optical recording medium, 2.4-fold speed recording of DVD-R was performed under the above-described conditions, and ST (%), MT (%), and Δ jitter were measured. The results obtained for ST (%), MT (%), Δ jitter are given in Table 2 below. In addition, for a material having ST (%) of 9% or less, the graph obtained by plotting thermal conductivity on the horizontal axis and Δ jitter on the vertical axis is shown in fig. 2. In the graph of FIG. 2, ". diamond-solid" corresponds to each material. As is clear from the graph of FIG. 2, the thermal conductivity is limited to 70W/mK (67W/mK for Sn), and if the thermal conductivity is larger than this limit, the characteristics are drastically improved. Further, it is found that when the thermal conductivity is 90W/mK or more, if Si and C, which are semiconductors, are removed, Δ jitter is 1% or less, and excellent characteristics can be obtained. It is also considered that Si and C can be used by mixing them with other metal components to improve the characteristics.

TABLE 2

Barrier layer material	Barrier layer thickness (nm)	Thermal conductivity (bulk) of barrier layer material (W/m. K)	ST(％)	MT(％)	Δjitter(％)
						Cu	2	401	7.6	7.9	0.3
Al	2	237	6.9	7.2	0.3
						Au	2	317	9	9.5	0.5
Co	2	100	7.8	8.5	0.7
						Cr	2	94	7.5	8.5	1
Mo	2	138	7.1	7.2	0.1
						Nb	2	54	10.1	11	0.9
Si	2	148	7.6	9.2	1.6
						Sn	2	67	7.7	10.3	2.6
Ta	2	58	9.8	10.2	0.4
						W	2	174	7.5	7.8	0.3
C	2	129	7.2	8.7	1.5
						SiO	2	1.4	7.8	9.5	1.7
SiN	2	3.7	7.9	9.7	1.8
						ZnS-SiO	2	0.66	7.6	9.7	2.1

^*According to solidsPhysics, Vol.21 (1986), p.277, Table 1.

^**According to Japanese Journal of Applied Physics, Vol.31(1992), Pt.1, No.2B, p.415, Table I.

^***According to Japanese Journal of Applied Physics, Vol.35(1996), Pt.1, No.1B, p.425, Table III.

The graphs of ST (%) and MT (%) obtained using various materials for the barrier layer are shown in FIG. 4. As is clear from the graph of FIG. 4, recording characteristics of Al (237W/m.K thermal conductivity), Mo (138W/m.K thermal conductivity), W (174W/m.K thermal conductivity), and Cu (401W/m.K thermal conductivity) were excellent. In addition, Co and Cr were excellent in sensitivity and jitter in both 4 × speed recording and 8 × speed recording. In addition, it is possible to form a barrier layer having good recording characteristics and weather resistance by alloying Ag, Al, Si, and C, or by improving a photocurable resin. Further, with respect to Au, characteristics such as MT (%), ST (%), and the like can be improved by adjusting the recording pulse strategy. However, Au has a narrow recording pulse tolerance and is slightly inferior to the above-mentioned excellent Mo, W, Cu, Co, Cr and Al. It is believed that this is due to the mechanical properties of the Au film at high temperatures.

On the other hand, Nb and Ta having ST (%) greater than 10% have small Δ jitter of 0.9% and 0.4%, respectively, and the jitter of the length of each mark (マ - ク) is poor, so that the jitter value cannot be improved even when the recording strategy conditions are studied. Therefore, it is found that Nb (thermal conductivity: 54W/m.K) and Ta (thermal conductivity: 58W/m.K) cannot be selected as the material of the barrier layer of the present invention.

[ Experimental example 2]

Mo and Co (thermal conductivity 100W/m.K) having the thermal conductivity specified in the present invention and a dielectric film ZnS-SiO to be compared therewith₂The materials were used to prepare a two-layer type optical recording medium (a two-layer type DVD-R optical disc) in which the optical disc 1 was provided with the barrier layers having the film thicknesses shown in table 3 below. In obtainingThe optical disk 1 of the optical recording medium of (1) was recorded on the DVD-R at a speed of 2.4 times under the above-mentioned conditions, and ST (%), MT (%), and Δ jitter were measured. The results obtained for ST (%), MT (%), Δ jitter are given in Table 3 below. Further, the graph obtained by plotting the film thickness of the barrier layer on the abscissa and Δ jitter on the ordinate is shown in fig. 3.

TABLE 3

Barrier layer material	Barrier layer thickness (nm)	Thermal conductivity (bulk) of barrier layer material (W/m. K)	ST(％)	MT(％)	Δjitter(％)
						Co	1	100	8.6	10.0	14
Co	2	100	7.8	8.5	0.7
						Co	3	100	9.0	9.2	0.2
Co	5	100	13.5	15.1	1.6
						Mo	1	138	7.5	8.7	1.2
Mo	2	138	7.1	7.2	0.1
						Mo	3	138	7.1	7.6	0.5
Mo	5	138	8.9	12.5	3.6
						Mo	10	138	10.6	14.7	4.1
ZnS-SiO	2	0.66	7.6	9.7	2.1
						ZnS-SiO	5	0.66	8.7	10.6	1.9
ZnS-SiO	10	0.66	9.3	10.8	1.5

^****According to Japanese Journal of Applied Physics, Vol.35(1996), Pt.1, No.2B, p.425, Table III.

As shown in Table 3 and FIG. 3, it is found that, in the case of the optical recording medium having the barrier layer of Mo or Co having a thermal conductivity of more than 70W/m.K, if the film thickness is thinner than 5nm, the Δ jitter tends to be lowered, and the film thickness is similar to ZnS-SiO₂The comparison shows good jitter. Particularly, when the film thickness is about 3nm, Mo and Co are stable, and excellent ST (%), MT (%), and Δ jitter can be obtained.

On the other hand, it can be seen that for ZnS-SiO₂If Δ jitter is about 2% regardless of the film thickness, the barrier layer of the present invention cannot have such good properties. This difference is considered to be caused by that, first, the thermal conductivity of the dielectric body is very low, about 1/100 or less which is the conductivity of the present invention. That is, since a sufficient heat dissipation effect cannot be obtained in the dielectric film, a good signal crosstalk characteristic cannot be obtained in the shallow trench and inverted stack structure. Further, it is considered that the dielectric film lacks ductility such as that of the metal, alloy or semiconductor film of the present invention, which is also a cause of failure to obtain excellent ST (%) characteristics.

[ Experimental example 3]

The optical recording medium using Mo, Cr, and Co (each having a film thickness of 2nm) as a material for the barrier layer among the optical recording media produced in experimental example 1 was stored in a test cell at 80 ℃ and 85% relative humidity after recording, and was taken out after 250 hours, and a signal of the recording portion was read. It is known that PI (Parity of Inner-code) errors of any optical recording medium hardly change and have good storage stability.

[ Experimental example 4]

[ production of optical recording Medium ]

< preparation of reverse laminate >

First, a substrate (1) having a diameter of 120mm and a thickness of 0.60mm was formed by injection molding polycarbonate using a Ni stamper having grooves formed in the surface thereof, wherein the grooves having a pitch of 0.74 μm, a width of 340nm and a depth of 28nm were formed in the substrate (1). Then, a reflection layer (1) is formed on the substrate (1) by forming an Ag-Bi-Nd alloy into a film having a thickness of 80nm by a sputtering method. Next, the above-mentioned dye A (Ni as the central metal) was prepared as an organic dye compound²⁺) And the above pigment B (the central metal being Zn)²⁺) A tetrafluoropropanol solution (concentration: 2.1 wt%) of the mixture of (dye a: dye B: 50 wt%) was dropped on the above reflective layer (1), spin-coated, and then dried at 70 ℃ for 30 minutes to form a recording layer (1), and the OD value of the recording film obtained thereby was 1.20.

Further, it was found that the heat dissipation amount of the pigment B in a nitrogen atmosphere was 40.7Cal/g, the decomposition temperature was 278 ℃ and the pigment B had a suitable heat dissipation amount at least in the thermal mode recording. Further, the heat dissipation amount and the decomposition temperature were measured under the conditions of a temperature rise rate of 10 ℃ per minute and a sample amount of about 4mg using TG/DTA6200 manufactured by セイコ - インスツルメント.

Further, the maximum absorption wavelengths of the dye-coated film of dye B were 554.1nm and 601.9 (strong) nm, and it was found that dye B was the following dye: the absorbance of the maximum absorption at around the recording wavelength of 660nm was 15.5%, that is, the absorption was an appropriate amount in recording to the 2 nd layer recording layer of the dual-layer type optical recording medium.

Next, after the recording layer (1) is formed, ZnS-SiO is sprayed on the recording layer (1) as soon as possible by the sputtering method₂Forming a thickness of 130 nm. Thus, the optical disk 1 of the reverse laminate is prepared.

< preparation of Positive laminate >

A substrate (2) made of polycarbonate and having guide grooves with a depth of 160nm, a width of 360nm and a track pitch of 740nm was prepared, and 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 on the surface of the substrate (2) on which the guide grooves were formed, followed by spin coating and drying at 70 ℃ for 30 minutes to form a recording layer (2). The thickness of the recording layer (2) (the thickness of the recording layer in the groove of the positive laminate in FIG. 1 (a)) was about 80 nm. Then, an Ag-Bi alloy (Bi: 1.0 atomic%) was deposited on the recording layer (2) by thermal spraying to a thickness of 17nm to form a reflective layer (2). Further, an ultraviolet curable resin (a radical ultraviolet curable resin SD347 manufactured by Dainippon インキ Co., Ltd.) was spin-coated on the reflective layer (2) and cured to form a protective coating having a thickness of 3 μm to 4 μm, thereby preparing an optical disk 2 of a positive laminate.

< production of Dual-layer type optical recording Medium >

Resin a (a radical ultraviolet curable resin manufactured by japan インキ co., ltd.: elastic modulus 4000MPa (30 ℃), glass transition temperature Tg 174 ℃) was coated on the barrier layer of the optical disk 1 (the reverse laminate prepared by the above-described method), and the spin coating rotation speed was adjusted so that the film thickness became 23 μm. Further, the resin A was applied to the protective coating layer of the optical disk 2 (positive laminate), and the spin-coating rotation speed was adjusted so that the film thickness became 23 μm. Then, the optical disc 1 and the optical disc 2 coated with the resin a are respectively stacked so that the surfaces coated with the resin a face each other, and then, the resin a is cured by irradiating ultraviolet rays from the substrate (2) side of the optical disc 2 (positive laminate) to form a transparent resin layer composed of the resin a, thereby producing a dual-layer type optical recording medium.

The elastic modulus and the glass transition temperature Tg of the resin A were measured under the conditions of a measurement frequency of 3.5Hz and a temperature rise rate of 3 ℃/min using a dynamic viscoelasticity tester (manufactured by レオバイブロン, DDV シリ - ズ).

[ high-speed recording conditions on optical disk 1 (reverse laminate) ]

The conditions for high-speed recording of optical information on the optical disc 1 (reverse laminate) are as follows.

As an evaluation machine, DDU-1000 (wavelength 662nm, number of apertures of objective lens NA 0.65) manufactured by パルステツク was used.

The recording speed was set to 4 times the speed of DVD (4 × recording) (linear speed 15.3 m/s).

As a recording pulse strategy, DVD + Recordable Dual Layer 8.5Gbyte B active Format Specifications version 1.1 was followed.

The power ratio of the pulses is set to P₀/P_m＝1.7。

The recording power is set to 20mW to 40 mW.

The jitter (data-to-clock jitter) measurement is performed at 1 × speed.

Fig. 6(a) is a graph showing a relationship between jitter and asymmetry in the optical recording medium optical recording power relationship graph 6 (b). Further, "asymmetry" refers to a value specified as "asymmetry" in the standard specification for DVD-R or DVD + R. When the asymmetry is positive, it means that recording is performed with a sufficiently large recording power, and when the asymmetry is negative, it means that the recording power is insufficient.

The curve shown as "pigment a + pigment B" in fig. 6(a) is the jitter tolerance of the inverted laminate containing a pigment having Zn as a central metal ion in the recording layer (1). Although recording is performed at a very high speed of 4 times the speed on the dual-layer type optical recording medium, even if the asymmetry is changed from a very wide range of-5% (corresponding to "-0.05" in fig. 6 (a)) to a value slightly larger than + 15% (corresponding to "0.15" in fig. 6 (a)), good jitter of 9% can be ensured.

On the other hand, in the anti-laminate of experimental example 4, the asymmetry tolerance of the 4 × recorded jitter was examined in exactly the same manner as in experimental example 4 except that the dye B whose central metal was a Zn ion was converted to the dye C whose central metal was not a Zn ion, and the dye a and the dye C were set to 40 wt% to 60 wt%, and the result was shown in the graph shown as "dye a + dye C" in fig. 6 (a). It is known that the asymmetry tolerance and bottom-shaking "pigment a + pigment C" are no better than the combination of "pigment a + pigment B". Further, the heat dissipation amount of the pigment C in a nitrogen atmosphere was 27.6Cal/g, and the decomposition temperature was 348 ℃. Further, the maximum absorption wavelengths of the dye-coated film of the dye C were 547.11nm and 597.05nm, and the dye C was found to be the following: the absorbance at the maximum absorption around the recording wavelength of 660nm was 14.4%. The shape of the absorption spectrum of the film of the dye C is gentler than that of the dye B.

The recording laser energy was varied, and the 4 × recorded MT% of the reverse laminate of "dye a + dye B" and "dye a + dye C" was measured, and the result is shown in fig. 6 (B). It is found that the combination of "pigment A + pigment B" is superior to the combination of "pigment A + pigment C" even for MT%.

From the above results, it is clear that Zn is contained in the composition²⁺In the case of the pigment of the present invention which is a central metal, the asymmetry tolerance of the jitter is wide, and further, the jitter value itself is good, and the signal crosstalk is also reduced.

[ Experimental example 5]

In experimental example 5, a dual-layer type optical recording medium having the configuration shown in fig. 5 was prepared and MT (%) and ST (%) of optical information recorded on the recording layer (1) (2 nd layer recording layer) were measured according to the following procedure.

First, a substrate (2) having a diameter of 120mm and a thickness of 0.57mm was formed by injection molding polycarbonate using a Ni stamper having grooves formed in the surface thereof, wherein the grooves having a pitch of 0.74 μm, a width of 0.33 μm and a depth of 160nm were formed in the substrate (2).

Then, a tetrafluoropropanol solution (concentration: 2 wt%) of a mixture of the above-mentioned dye a and the above-mentioned dye C (dye a: dye C: 10 wt%: 90 wt%) was dropped, spin-coated, and then dried at 70 ℃ for 30 minutes to form a recording layer (2). Further, a semitransparent reflective layer (2) having a thickness of 17nm was formed on the recording layer (2) by a thermal spraying method using an Ag alloy consisting of Ag-Bi (Bi: 1.0 atomic%).

Subsequently, a predetermined ultraviolet-curable resin [ 1] for forming a transparent resin layer was circularly dropped on the reflective layer (2), and a film having a thickness of about 25 μm was formed by spin coating. On the other hand, a predetermined ultraviolet-curable resin [ 2] was circularly dropped 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 spin coating.

Then, the resin stamper is bonded to the reflective layer (2) so that the resin layer composed of the ultraviolet curable resin [ 1] and the resin layer composed of the ultraviolet curable resin [ 2] face each other. Next, ultraviolet rays are irradiated from the resin stamper side to cure and bond these resin layers, thereby forming a bonded body having a transparent resin layer (2P layer) having a guide groove. Further, the track pitch of the guide grooves on the transparent resin was 0.74. mu.m, the groove width was 290nm, and the groove depth was 190 nm.

Further, as the ultraviolet curable resins [ 1] and [ 2], the following radical-based ultraviolet curable resins were used, respectively. The glass transition temperatures of the respective ultraviolet-curable resins [ 1] and [ 2] are shown in parentheses.

Ultraviolet-curable resin [ 1 ]: SD6036(Tg 60 ℃ C.) manufactured by Dainippon インキ K.K.)

Ultraviolet-curable resin [ 2 ]: the pigment A (Ni as the central metal) was prepared as an organic pigment compound (MPZ 388(Tg 161 ℃ C.) manufactured by Nippon Kabushiki Kaisha²⁺) The pigment B (the central metal being Zn)²⁺) And a pigment D represented by the formula (the central metal is Zn)²⁺) A solution (concentration: 2.1 wt%) of the mixture of (pigment a), (pigment B + pigment D) 50 wt%, (15 wt% +35 wt%), 50 wt%, (50 wt%), in tetrafluoropropanol, and the mixture was mixed with a solvent to prepare a solutionThe resultant was dropped onto the reflective layer (1), spin-coated, and then dried at 70 ℃ for 30 minutes to form a recording layer (1) on the transparent resin layer (2P layer).

Pigment D

Furthermore, it was found that the heat dissipation amount of the pigment B in a nitrogen atmosphere was 40.7Cal/g, the decomposition temperature was 278 ℃ and the heat dissipation amount of the pigment D in a nitrogen atmosphere was 34.1Cal/g, the decomposition temperature was 251 ℃ and Zn was represented²⁺These pigments as the central metal ion are pigments having a moderate heat dissipation amount at least in thermal mode recording. Further, the amount of heat released and the decomposition temperature were measured under the conditions of a temperature rise rate of 10 ℃ per minute and a sample amount of about 4mg, using TG/DTA6200 manufactured by セイコ - インスツルメント.

Further, the maximum absorption wavelengths of the dye-coated film of dye B were 554.1nm and 601.9 (strong) nm, and it was found that dye B was the following dye: the absorbance of the maximum absorption at around the recording wavelength of 660nm was 15.5%, that is, the absorption was an appropriate amount in recording to the 2 nd layer recording layer of the dual-layer type optical recording medium.

Further, the maximum absorption wavelengths of the dye-coated films of dye D were 561.6nm and 608.3 (strong) nm, and it was found that dye D was: the absorbance of the maximum absorption at around the recording wavelength of 660nm was 20.1%, that is, the absorption was an appropriate amount in recording to the 2 nd layer recording layer of the dual-layer type optical recording medium.

Next, a film of the reflective layer (1) having a thickness of 120nm was formed by a sputtering method using an Ag alloy consisting of Ag-Bi (Bi: 1.0 atomic%).

Further, an ultraviolet curable resin is spin-coated on the reflective layer (1) to provide an adhesive layer. Further, a polycarbonate substrate having a diameter of 120mm and a thickness of 0.6mm was mounted on the adhesive layer to form a substrate (2), and ultraviolet rays were irradiated thereto to cure and bond the substrate. The above procedure was carried out to produce a two-layer optical recording medium obtained by the 2P method.

[ high-speed recording conditions on the recording layer (1) of a two-layer type optical recording medium ]

The conditions for high-speed recording of optical information on the recording layer (1) of the dual-layer optical recording medium are as follows.

As an evaluation machine, ODU-1000 manufactured by パルステツク (wavelength 660nm, aperture number NA of objective lens 0.65) was used.

The recording speed was set to 8 times the speed of the DVD (8 × recording) (linear speed 30.67 m/s).

As a recording pulse strategy, DVD + Recordable Dual Layer 8.5Gbyte basic Format Specifications version 1.1 was followed.

The power ratio of the pulses is set to P₀/P_m＝1.3。

The recording power was set to 40-52 mW.

The jitter (data-to-clock jitter) measurement was performed while reading at 1 x 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 asymmetry tolerance of the wobble recorded at the 8 × speed of the recording layer (1) is shown as a graph of "pigment a + pigment B + pigment D". Even under such 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), when the wobbling is 9% or less, excellent high-speed recording characteristics of the dual-layer type optical recording medium are exhibited.

On the other hand, the dye B and the dye D are converted into Ni as a central metal ion²⁺And a pigment C ofThe above-described 8-fold speed recording was performed on the recording layer (1) of the dual-layer type optical recording medium obtained in exactly the same manner except that the dye C was set to 50 wt%. The result is shown in fig. 7 as a graph of "pigment a + pigment C". Further, the heat dissipation amount of the pigment C in a nitrogen atmosphere was 27.6Cal/g, and the decomposition temperature was 348 ℃. Further, the maximum absorption wavelengths of the dye-coated film of the dye C were 547.11nm and 597.05nm, and it was found that the dye C had an absorption of 14.4% of the absorbance of the maximum absorption at a recording wavelength of 660 nm. The shape of the absorption spectrum of the film of the dye C is gentler than that of the above-mentioned dyes B and D.

As is clear from fig. 7, in the recording layer (1), the jitter rapidly increases and deteriorates as the asymmetry exceeds + 6% and becomes large for the combination of the dye a and the dye C. As is clear from the above, the center metal is Zn²⁺The dye B and the dye D of the present invention can be used in combination to perform extremely high-speed recording such as 8-fold speed recording on the 2 nd recording layer (1)) of a dual-layer optical recording medium.

Industrial applicability

The present invention is suitably used for optical recording media for red semiconductor laser such as DVD ± R, optical recording media for blue semiconductor laser, and the like.

Further, the present application is based on Japanese application laid out on 7/4/2005 (Japanese patent application No. 2005-111244) and Japanese application laid out on 6/4/2006 (Japanese patent application No. 2006-104917), and the entire contents thereof are incorporated by reference.

Claims (5)

1. An optical recording medium comprising a substrate, a reflective layer, a recording layer containing an organic dye, and a transparent resin layer in this order,

wherein a barrier layer is provided between the recording layer and the resin layer, and a material for the barrier layer has a thermal conductivity M of 70W/m.K or more at 300K as a bulk, and a film thickness t of the barrier layer is less than 5nm,

the barrier layer is a simple metal element selected from the group consisting of Mg, Cr, Mn, Fe, Ni, Zn, Ru, Rh, Pd, In, Os, Ir, Pt, Mo, Al, W, Co, Cr, Cu, Ag and Au or an alloy with the metal element as a main component.

2. An optical recording medium according to claim 1, wherein M is 90W/M-K or more.

3. An optical recording medium according to claim 1 or 2, wherein t is 1nm to 4 nm.

4. An optical recording medium according to claim 1, 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.

5. An optical recording medium according to claim 1 or 2, further comprising a 2 nd reflective layer, a 2 nd recording layer and a transparent substrate provided on said transparent resin layer in the recited order.