JPH10188339A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DRAW type optical recording medium which is stable in tracking at the time of recording and enables high-density recording having good recording characteristics. SOLUTION: This high-density optical recording medium has a recording layer contg. dyestuff to absorb laser beams on a substrate spirally formed with pregrooves and a reflection layer of a metal on this recording layer. In such a case, a track pitch and groove depth are regulated with respect to the recording beam diameter (λ is a recording wavelength and NA is the numerical aperture of an objective lens) expressed by λ/NA. Further, the dyestuff included in the recording layer is formed of a trimethyl cyanine compd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a recording layer containing a dye and a reflective layer on a transparent substrate, and more particularly to an optical recording medium capable of recording at high density.

[0002]

2. Description of the Related Art A recordable optical recording medium in which a recording layer is made of a dye and a metal reflective layer is provided on the recording layer in order to increase the reflectance is disclosed in, for example, Optical Data Storage 1989.
Technical Digest Series Vol. 145 (1989), a medium using a cyanine dye or a phthalocyanine dye in the recording layer is marketed as a CD-R medium.
These media are characterized in that they can be recorded by a 780 nm semiconductor laser and can be reproduced by a commercially available CD player or CD-ROM player equipped with a 780 nm semiconductor laser. But these media
It has a capacity of only about 650 MB, and the recording time is as short as 15 minutes or less for recording large-capacity information such as digital moving images. In addition, if the size of the conventional medium is reduced in order to cope with a situation where the size of the device is reduced, the capacity becomes insufficient. The above-mentioned conventional CD-R medium performs recording and reproduction using a semiconductor laser having a wavelength of about 780 nm.
Semiconductor lasers of up to 655 nm have been developed, enabling higher-density recording and / or reproduction, and an optical recording medium in which a high-quality moving image of about 2 hours is recorded on a medium having a diameter of 120 mm has been developed as a DVD. This medium has a recording capacity of 4.7 GB / side, but is a read-only medium made by transferring pits to a substrate. Recently, a read-only DVD as described above
There is a demand for a recordable optical recording medium having a capacity close to that of the above.

In a recordable medium, it is necessary to reduce the recording laser beam in order to increase the recording capacity. The beam diameter becomes smaller as the wavelength of the laser used becomes shorter and the numerical aperture (NA) of the objective lens becomes larger, which is preferable for high-density recording. However, the current semiconductor laser technology and the NA of the lens limit the beam diameter. There is. For example, the beam diameter of the DVD described above is not small for the recording density as compared with the conventional CD. Therefore, during recording, pits smaller than the beam diameter must be accurately formed as compared with the case of CD-R. However, as the size of the pits becomes smaller, the degree of modulation of the shortest pits becomes smaller, causing a problem that the jitter and the error rate increase. Therefore, there is a demand for a medium that can accurately form thin and small pits without sacrificing the degree of modulation during recording. Furthermore, considering the stability of tracking for positioning the laser along the groove during recording, the unrecorded radial contrast (RCb) is 0.0%.
Desirably greater than 5. Further, a medium using a trimethine cyanine dye that absorbs light of a short wavelength is disclosed in
40162. However, only a trimethine cyanine dye is mentioned as a dye having recording sensitivity to short-wavelength laser light for high-density recording, but nothing is disclosed about various conditions for increasing the recording capacity.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to optimize a recording beam diameter, a track pitch, a groove shape and a dye, and to perform tracking during recording even if the track pitch is reduced with respect to the recording beam diameter. The object of the present invention is to provide a high-density optical recording medium which is stable and has good recording characteristics when smaller pits are formed than before.

[0005]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, by optimizing the recording beam diameter, track pitch, groove shape, and dye structure, the recording beam Even when the track pitch is made smaller than the diameter, the tracking during recording is stable with an appropriate RCb value, and when a smaller pit is formed, the degree of modulation is larger, the jitter and error rate are better. It has been found that a high-density optical recording medium can be realized, and the present invention has been completed.

That is, the present invention relates to a recording layer containing a dye that absorbs a laser beam directly or through another layer on a substrate in which a groove is formed in a spiral shape, and directly or on another layer on the recording layer. In an optical recording medium having a metal reflective layer via a layer, the diameter of a recording beam represented by λ / NA is r (where λ is the recording wavelength (μm), and NA is the numerical aperture of the objective lens). , The pitch of the groove of the substrate is P
(Μm), the depth of the groove is dsub (μm), the dye film thickness of the groove portion of the recording layer is dg (μm), the dye film thickness of the land portion is dl (μm), and the refractive index of the recording layer at wavelength λ To nab
where s and the refractive index of the substrate are nsub, the following relationship is established: 0.66r ≦ P ≦ 0.89r 0.12r ≦ dsub ≦ 0.20r 1.8 ≦ nabs ≦ 2.7 Phase difference (ΔT) = 2 [nsub · dsub + nab
s (dl−dg)] / λ is 0.13 ≦ ΔT ≦ 0.41;
dg-dl≤dsub, and the dye contained in the recording layer is a trimethinecyanine compound represented by the general formula (Chemical Formula 2). .655 μm, NA 0.58-0.7
0 is a high-density optical recording medium.

[0007]

Embedded image [Wherein, Y and Y ′ are each CR ₄ R ₅ , O, S, S
e or NR ₆ , wherein R _{1 to} R ₆ are a hydrogen atom or an unsubstituted or substituted alkyl group having 1 to 12 carbon atoms, A ₁ to
A ₄ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, A ₁ and A ₂ , A ₃ and A ₄ may form an unsubstituted or substituted benzene ring or a naphthalene ring;
Represents a monovalent anion. However, when R ₁ is a monovalent anionic substituent, X does not exist.]

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a recording layer containing a dye that absorbs laser light directly on a substrate in which grooves are formed spirally or through another layer, directly or on the recording layer. In an optical recording medium having a metal reflective layer via another layer, by optimizing the recording beam diameter, track pitch, groove shape and dye structure, even if the track pitch is reduced with respect to the recording beam diameter. , RC
An object of the present invention is to provide a high-density optical recording medium having a moderate b value, stable tracking during recording, a large degree of modulation when forming smaller pits than before, and a good jitter and error rate. .

When a dye is used for the recording layer, the recording layer can be formed by spin coating. When a recording layer is formed on a substrate having a groove by a spin coating method, the thickness of the recording layer in the groove portion is usually larger than the thickness of the recording layer in the portion between the grooves (lands). On the other hand, the recording sensitivity depends on the thickness of the recording layer, and particularly in the case of a medium provided with a metal reflective layer on the recording layer, heat is diffused into this reflective layer and the recording sensitivity is reduced. The smaller the thickness of the recording layer, the greater the influence of this thermal diffusion, and the lower the sensitivity. That is,
A large difference occurs in the recording sensitivity between the groove and the land. Therefore, even if the beam diameter of the recording laser beam is large, a thin pit can be formed. However, no matter how thin pits can be recorded, the track pitch cannot be reduced. Even if the track pitch is reduced without limit,
When the diameter of the laser beam at the time of reproduction is large, not only the degree of modulation becomes small, but also the crosstalk becomes too large, the jitter becomes worse, and the reproduction becomes impossible.

According to the present invention, in order to perform recording in such a manner that crosstalk is small and jitter is good without sacrificing the degree of modulation during reproduction, the recording beam diameter represented by λ / NA is defined as r. , The track pitch (P) is set to 0.66r to 0.
It is preferably 89r. Track pitch is 0.66
If it is less than r, the jitter and error rate increase, which is not preferable. If it exceeds 0.89r, the recording density in the radial direction does not increase, and the desired recording capacity cannot be obtained. In FIG. 1, the depth of the groove portion of the substrate is dsub (μm), the dye film thickness of the groove portion of the recording layer is dg (μm), the dye film thickness of the land portion is dl (μm), and the wavelength is λ. The refractive index of the recording layer is nabs, and the refractive index of the substrate is nsub
In order to sufficiently obtain the modulation degree and the radial contrast, dsub is preferably set to 0.12r to 0.20r.

Further, the optical distance (Xp) of the groove portion
Is nabs · dg, and the optical distance of the land (Xl)
Is nsub.dsub + nabs.dl. Therefore, when a laser beam having a wavelength .lambda. Is irradiated from the substrate side, the optical phase difference of the laser beam reflected by the reflective layer at the groove portion and the land portion [.DELTA.T = 2 (Xl -Xp) / [lambda]
2 [nsub.dsub + nabs (dl-dg)] / λ (where,
dg−dl ≦ dsub), and the range of ΔT is preferably from 0.13 to 0.41. That is, the organic dye layer is decomposed by the recording laser light, burned,
Since the difference in reflectivity from a change or the like where deformation or the like does not occur is a signal modulation degree, it is necessary to take a sufficient optical path length of the dye film in order to obtain a large modulation degree. In addition, in consideration of an optical phase difference for sufficiently obtaining an unrecorded radial contrast, it is necessary to satisfy the above-described conditions of the substrate depth and the optical phase difference. If the depth of the groove is less than 0.12r, the modulation degree and the radial contrast will be small, and the jitter characteristics will be deteriorated. If it exceeds 0.20r, it will be difficult to reduce the reflectance and form the substrate. Further, when ΔT is less than 0.13, a sufficient degree of modulation and radial contrast cannot be obtained, and when it is 0.41 or more, a decrease in reflectance occurs.

At the wavelength λ of the laser beam, the refractive index nabs required for the recording layer is preferably 1.8 or more and 2.7 or less in consideration of the characteristics of the organic dye. When the value of nabs is smaller than 1.8, a large reflectivity and a high signal modulation cannot be obtained, and accurate signal reading cannot be performed. The extinction coefficient kabs is 0.04 to 0.2.
It is preferably 0. If kabs is smaller than 0.04, recording sensitivity is remarkably reduced, and recording is difficult with the current output of the semiconductor laser. If it is larger than 0.20, not only the reflectance required for accurate signal reading cannot be obtained, but also ,
The signal is easily changed by the reproduction light.

In the present invention, the beam diameter at the time of recording and reproduction becomes smaller as the wavelength of the laser used becomes shorter and the numerical aperture (NA) of the objective lens becomes larger, which is preferable for high density recording. As a high-output laser usable for recording, a semiconductor laser of 0.630 to 0.655 μm is preferable, in view of downsizing of the apparatus, simplification of an optical system, and the economical efficiency of the apparatus. ~ 0.640 μm
Is most preferred. Further, the limit of the NA of the lens is 0.70 in terms of aberration due to unevenness in the thickness of the substrate and inclination of the substrate. Preferably the NA is between 0.58 and 0.70.

The medium of the present invention comprises a recording layer containing a dye absorbing at least laser light and a metal reflective layer on a transparent substrate. For example, as shown in FIG. 1, a four-layer structure in which a substrate 1, a recording layer 2, a reflective layer 3 and a protective layer 4 are sequentially stacked, or as shown in FIG. There is a structure having a structure in which a recording layer 2 'and a reflective layer 3' are sequentially laminated, and a substrate 5 'is bonded thereon via an adhesive layer 4'. The transparent substrate used in the optical recording medium of the present invention preferably has a transmittance of light for recording and reading signals of 85% or more and has a small optical anisotropy. For example, a known resin substrate such as an acrylic resin, a polycarbonate resin, and a polyolefin resin may be used. These substrates may be in the form of a plate or a film, and their shape may be circular or card-like. The surfaces of these substrates have grooves and / or pits indicating recording positions. Such grooves and pits are preferably provided at the time of molding the substrate, but may also be provided by providing an ultraviolet curable resin layer on the substrate. The track (groove) pitch and groove depth are described above,
The width of the groove is preferably about 0.25 to 0.37 μnm.

In the present invention, the recording layer contains a dye, and the dye used in this recording layer is one of the important factors for obtaining good recording sensitivity, reflectance and modulation. It is. Among them, the characteristics of the dye species such as the decomposition characteristics and the above-described optical characteristics are particularly effective for the degree of modulation. In high-density recording, a dye having a large modulation degree when pits having the same size are formed and having excellent threshold characteristics is particularly preferable. In this regard, trimethine represented by the general formula (1) is preferred. Preference is given to cyanine compounds.

In the substituents of the general formula (1), R _{1 to} R
₆ is a hydrogen atom or a linear or branched alkyl group, an alkoxyalkyl group, an alkoxyalkoxyalkyl group, an alkoxyalkoxyalkoxyalkyl group, an alkoxycarbonylalkyl group, an alkoxycarbonyloxyalkyl group, an alkoxyalkoxycarbonyloxyalkyl group, a hydroxyalkyl group, Hydroxyalkoxyalkyl group, hydroxyalkoxyalkoxyalkyl group, cyanoalkyl group, acyloxyalkyl group, acyloxyalkoxyalkyl group, acyloxyalkoxyalkoxyalkyl group, halogenated alkyl group, sulfonealkyl group, alkylcarbonylaminoalkyl group, alkylsulfonaminoalkyl group , A sulfonamidoalkyl group, an alkylaminoalkyl group, an aminoalkyl group, and an It is selected from a killsulfonalkyl group and the like.

The linear or branched alkyl group is a hydrocarbon group having 1 to 12 carbon atoms. In consideration of workability by coating on a polycarbonate, acrylic, epoxy, polyolefin substrate, etc., a methyl group, an ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, t-butyl group, n-pentyl group, iso-pentyl group, 2-methylbutyl group, 1-methylbutyl group, neo-pentyl group, 1,2-dimethylpropyl group, 1,1-dimethylpropyl group, cyclopentyl group, n-hexyl group, 4-methylpentyl group, 3-methylpentyl group, 2-methylpentyl group, 1-methylpentyl group,
3,3-dimethylbutyl group, 2,3-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 1,2-dimethylbutyl group, 1,1-dimethylbutyl group, 3- Ethylbutyl group,
2-ethylbutyl group, 1-ethylbutyl group, 1,2,2-trimethylbutyl group, 1,1,2-trimethylbutyl group, 1-ethyl-2-
Methylpropyl group, cyclohexyl group, n-heptyl group,
2-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 2,4-dimethylpentyl group, n-octyl group, 2-ethylhexyl group, 2,5-dimethylhexyl group, 2,5,5-trimethylpentyl group, 2,4-dimethylhexyl group, 2,2,4-trimethylpentyl group, n-nonyl group, n-decyl group, 4-ethyloctyl group, 4-ethyl-4, Five-
Methylhexyl, n-undecyl, n-dodecyl, 4-
Butyloctyl group, 6,6-diethyloctyl group, 3,5-dimethylheptyl group, 2,6-dimethylheptyl group, 2,4-dimethylheptyl group, 2,2,5,5-tetramethylhexyl group, 1 -cy
clo-pentyl-2,2-dimethylpropyl group, 1-cyclohexyl-2,2-dimethylpropyl group and the like.

Examples of the alkoxyalkyl group include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group, a methoxyethyl group, an ethoxyethyl group, a propoxyethyl group, a butoxyethyl group, an n-hexyloxyethyl group, Methylpentoxyethyl group, 1,3-
Dimethylbutoxyethyl group, 2-ethylhexyloxyethyl group, n-octyloxyethyl group, 3,5,5-trimethylhexyloxyethyl group, 2-methyl-1-iso-propylpropoxyethyl group, 3-methyl-1- Carbon number of iso-propylbutyloxyethyl group, 2-ethoxy-1-methylethyl group, 3-methoxybutyl group, 3,3,3-trifluoropropoxyethyl group, 3,3,3-trichloropropoxyethyl group, etc. 2-12.

Examples of the alkoxyalkoxyalkyl group include methoxyethoxyethyl, ethoxyethoxyethyl, propoxyethoxyethyl, butoxyethoxyethyl, hexyloxyethoxyethyl, 1,2-dimethylpropoxyethoxyethyl, 2- Methoxy-1-methylethoxyethyl group, 2-butoxy-1-methylethoxyethyl group, 2- (2'-ethoxy-1'-methylethoxy) -1-methylethyl group, 3,3,3-trifluoropropoxy Examples include an ethoxyethyl group and a 3,3,3-trichloropropoxyethoxyethyl group.

Examples of the alkoxyalkoxyalkoxyalkyl group include a methoxyethoxyethoxyethyl group,
Examples thereof include an ethoxyethoxyethoxyethyl group, a butoxyethoxyethoxyethyl group, a 2,2,2-trifluoroethoxyethoxyethoxyethyl group, and a 2,2,2-trichloroethoxyethoxyethoxyethyl group. Examples of the alkoxycarbonylalkyl group include a methoxycarbonylmethyl group, an ethoxycarbonylmethyl group, a butoxycarbonylmethyl group, a methoxycarbonylethyl group, an ethoxycarbonylethyl group, a butoxycarbonylethyl group,
2,3,3-tetrafluoropropoxycarbonylmethyl group,
And a 2,2,3,3-tetrachloropropoxycarbonylmethyl group.

Examples of the alkoxycarbonyloxyalkyl group include a methoxycarbonyloxyethyl group, an ethoxycarbonyloxyethyl group, a butoxycarbonyloxyethyl group, a 2,2,2-trifluoroethoxycarbonyloxyethyl group, a 2,2,2 -Trichloroethoxycarbonyloxyl group and the like. Examples of the alkoxyalkoxycarbonyloxyalkyl group include a methoxyethoxycarbonyloxyethyl group, an ethoxyethoxycarbonyloxyethyl group, a butoxyethoxycarbonyloxyethyl group, a 2,2,2-trifluoroethoxyethoxycarbonyloxyethyl group, and a 2,2. , 2-trichloroethoxyethoxycarbonyloxyethyl group and the like.

Examples of hydroxyalkyl groups include 2-hydroxyethyl, 4-hydroxyethyl, 2-hydroxy-3-methoxypropyl, 2-hydroxy-3-chloropropyl, 2-hydroxy-3-ethoxy Propyl group, 3-butoxy-2-hydroxypropyl group, 2-hydroxy-3-phenoxypropyl group, 2-hydroxypropyl group, 2-hydroxybutyl group and the like. Examples of hydroxyalkoxyalkyl groups include hydroxyethoxyethyl group, 2- (2'-hydroxy-1'-methylethoxy) -1-methylethyl group, 2- (3'-fluoro-2'-hydroxypropoxy) ethyl Group, 2- (3′-chloro-2′-hydroxypropoxy) ethyl group, and the like.Examples of the hydroxyalkoxyalkoxyalkyl group include a hydroxyethoxyethoxyethyl group and [2 ′-(2′-hydroxy-1). '-Methylethoxy) -1'-
Methylethoxy] ethoxyethyl group, [2 '-(2'-fluoro
-1'-hydroxyethoxy) -1'-methylethoxy] ethoxyethyl group, [2 '-(2'-chloro-1'-hydroxyethoxy)
-1'-methylethoxy] ethoxyethyl group and the like.

Examples of cyanoalkyl groups include 2-cyanoethyl, 4-cyanobutyl, 2-cyano-3-methoxypropyl, 2-cyano-3-chloropropyl, 2-cyano-3
-Ethoxypropyl, 3-butoxy-2-cyanopropyl, 2-cyano-3-phenoxypropyl, 2-cyanopropyl, 2-cyanobutyl and the like. Examples of the acyloxyalkyl group include an acetoxyethyl group, a propionyloxyethyl group, a butyryloxyethyl group,
1-ethylpentylcarbonyloxyethyl group, 2,4,4-trimethylpentylcarbonyloxyethyl group, 3-fluorobutyryloxyethyl group, 3-chlorobutyryloxyethyl group and the like, and an acyloxyalkoxyalkyl group Examples include an acetoxyethoxyethyl group, a propionyloxyethoxyethyl group, a 1-ethylpentylcarbonyloxyethoxyethyl group, a 2-fluoropropionyloxyethoxyethyl group, a 2-chloropropionyloxyethoxyethyl group, and the like. Examples of the alkyl group include an acetoxyethoxyethoxyethyl group, a propionyloxyethoxyethoxyethyl group, a valeryloxyethoxyethoxyethyl group, a 2-fluoropropionyloxyethoxyethoxyethyl group, and 2-chloro. And a propionyloxyethoxyethoxyethyl group.

Examples of the halogenated alkyl group include a chloromethyl group, a chloroethyl group, a 2,2,2-trifluoroethyl group, a trifluoromethyl group, a bromomethyl group and a methyl iodide group. Examples of the sulfonealkyl group include a sulfonemethyl group, a sulfoneethyl group, a sulfonepropyl group, and the like. Examples of the alkylcarbonylaminoalkyl group include a methylcarbonylaminoethyl group, an ethylcarbonylaminoethyl group, a propylcarbonylaminoethyl group, a cyclohexylcarbonylaminoethyl group, and the like. Examples of the alkylsulfonaminoalkyl group include a methylsulfonaminoethyl group, an ethylsulfonaminoethyl group, a propylsulfonaminoethyl group, and the like. Examples of the sulfonamidoalkyl group include a sulfonamidomethyl group, a sulfonamidoethyl group, a sulfonamidopropyl group and the like.

Examples of the alkylaminoalkyl group include:
Examples include an N-methylaminomethyl group, an N, N-dimethylaminomethyl group, an N, N-diethylaminomethyl group, an N, N-dipropylaminomethyl group, and an N, N-dibleaminomethyl group. Examples of the aminoalkyl group include an aminomethyl group, an aminoethyl group, an aminopropyl group and the like. Examples of the alkylsulfonalkyl group include a methylsulfonmethyl group, an ethylsulfonemethyl group, a butylsulfonmethyl group, a methylsulfonethyl group, an ethylsulfonethyl group, a butylsulfonethyl group, and 2,2,3,3-tetrafluoropropyl And a sulfonemethyl group and a 2,2,3,3-tetrachloropropylsulfonemethyl group.

Examples of the substituted or unsubstituted alkenyl groups are alkenyl groups having the same substituents as the above-mentioned alkyl groups, and are preferably a propenyl group, a 1-butenyl group, an iso-butenyl group, -Pentenyl group, 2-pentenyl group, 2-methyl-1-butenyl group, 3-methyl-1-butenyl group, 2-methyl-2-butenyl group, 2,2-dicyanovinyl group, 2-cyano-2- And lower alkenyl groups such as a methylcarboxylvinyl group and a 2-cyano-2-methylsulfonevinyl group. Examples of the substituted or unsubstituted aralkyl groups are aralkyl groups having the same substituents as the above-mentioned alkyl groups, preferably benzyl, nitrobenzyl, cyanobenzyl, hydroxybenzyl, methylbenzyl Group, trifluoromethylbenzyl group, naphthylmethyl group, nitronaphthylmethyl group, cyanonaphthylmethyl group, hydroxynaphthylmethyl group, methylnaphthylmethyl group, trifluoromethylnaphthylmethyl group and the like.

Examples of the substituted or unsubstituted alkoxy groups are the alkoxy groups having the same substituents as the above-mentioned alkyl groups, preferably methoxy, ethoxy, n-propoxy, iso-propoxy. Group, n-butoxy group, iso-butoxy group, sec-butoxy group, t-butoxy group,
Lower alkoxy groups such as n-pentoxy group, iso-pentoxy group, neo-pentoxy group and 2-methylbutoxy group are exemplified. Examples of substituted or unsubstituted aryl groups include
Aryl groups having the same substituents as the alkyl groups mentioned above, preferably phenyl, nitrophenyl, cyanophenyl, hydroxyphenyl, methylphenyl, trifluoromethylphenyl, naphthyl, nitro Examples include a naphthyl group, a cyanonaphthyl group, a hydroxynaphthyl group, a methylnaphthyl group, and a trifluoromethylnaphthyl group.

Examples of the substituted or unsubstituted acyl groups are acyl groups having the same substituents as the above-mentioned alkyl groups, preferably formyl group, methylcarbonyl group, ethylcarbonyl group, n-propyl group. Carbonyl group, iso-propylcarbonyl group, n-butylcarbonyl group, iso-butylcarbonyl group, sec-butylcarbonyl group, t-butylcarbonyl group, n-pentylcarbonyl group,
Examples include an iso-pentylcarbonyl group, a neo-pentylcarbonyl group, a 2-methylbutylcarbonyl group, and a nitrobenzylcarbonyl group. Examples of the substituted or unsubstituted alkyl carboxyl group include an alkyl carboxyl group having the same substituent as the above-described alkyl group, preferably a methyl carboxyl group, an ethyl carboxyl group, an n-propyl carboxyl group, -Propyl carboxyl group, n-butyl carboxyl group, iso-butyl carboxyl group, sec-butyl carboxyl group, t-butyl carboxyl group, n-pentyl carboxyl group, iso-pentyl carboxyl group, neo-pentyl carboxyl group, 2-methyl A lower alkyl carboxyl group such as a butyl carboxyl group is exemplified.

Examples of the substituted or unsubstituted alkylcarbonylamino group include an alkylcarbonylamino group having the same substituent as the above-mentioned alkyl group, preferably a methylcarbonylamino group, an ethylcarbonylamino group, n-propylcarbonylamino group, iso-propylcarbonylamino group, n-butylcarbonylamino group, iso-butylcarbonylamino group, sec-butylcarbonylamino group, t-butylcarbonylamino group, n-pentylcarbonylamino group, iso And lower alkylcarbonylamino groups such as -pentylcarbonylamino group, neo-pentylcarbonylamino group, 2-methylbutylcarbonylamino group, cyclohexylcarbonylamino group, and succinimino group. Examples of the substituted or unsubstituted alkylsulfonamino group include an alkylsulfonamino group having the same substituent as the above-mentioned alkyl group, preferably a methylsulfonamino group, an ethylsulfonamino group, and n-propyl. Sulfonamino group, iso-propylsulfonamino group, n-butylsulfonamino group, is
o-butyl sulfone amino group, sec-butyl sulfone amino group, t-butyl sulfone amino group, n-pentyl sulfone amino group, iso-pentyl sulfone amino group, neo-pentyl sulfone amino group, 2-methylbutyl sulfone amino group,
A lower alkylsulfonamino group such as a cyclohexylsulfonamino group is exemplified.

Examples of the substituted or unsubstituted alkylamino group include an alkylamino group having the same substituent as the above-mentioned alkyl group, preferably an N-methylamino group or an N, N-dimethylamino group. And lower alkylamino groups such as N, N-diethylamino group, N, N-dipropylamino group and N, N-dibutylamino group. Examples of the substituted or unsubstituted alkylsulfone group include an alkylsulfone group having the same substituent as the above-mentioned alkyl group, preferably a methylsulfone group, an ethylsulfone group, an n-propylsulfone group, an iso group. -Propyl sulfone group, n-butyl sulfone group, iso-butyl sulfone group, sec-
Lower grades such as butyl sulfone group, t-butyl sulfone group, n-pentyl sulfone group, iso-pentyl sulfone group, neo-pentyl sulfone group, 2-methylbutyl sulfone group, 2-hydroxyethyl sulfone group, and 2-cyanoethyl sulfone group An alkylsulfone group is exemplified.

Examples of the substituted or unsubstituted alkylthio groups are the alkylthio groups having the same substituents as the above-mentioned alkyl groups, preferably a methylthio group,
Ethylthio, n-propylthio, iso-propylthio, n-butylthio, iso-butylthio, sec-butylthio, t-butylthio, n-pentylthio, iso-pentylthio, neo-pentylthio, 2- And lower alkylthio groups such as methylbutylthio group and methylcarboxylethylthio group. Examples of the substituted or unsubstituted alkylazomethine group include an alkylazomethine group having the same substituent as the above-mentioned alkyl group, preferably a methylazomethine group, an ethylazomethine group, or an n-
Propylazomethine group, iso-propylazomethine group, n-
Butylazomethine group, iso-butylazomethine group, sec-butylazomethine group, t-butylazomethine group, n-pentylazomethine group, iso-pentylazomethine group, neo-pentylazomethine group, 2-methylbutylazomethine group, hydroxyethylazomethine And lower alkylazomethine groups such as a group.

Examples of the substituted or unsubstituted alkylaminosulfone groups include alkylaminosulfone groups having the same substituents as the above-mentioned alkyl groups, preferably N-methylaminosulfone group, N-ethyl Aminosulfone group, N- (n-propyl) aminosulfone group, N- (iso-
Propyl) aminosulfone group, N- (n-butyl) aminosulfone group, N- (iso-butyl) aminosulfone group, N- (sec
-Butyl) aminosulfone group, N- (t-butyl) aminosulfone group, N- (n-pentyl) aminosulfone group, N- (iso
-Pentyl) aminosulfone group, N- (neo-pentyl) aminosulfone group, N- (2-methylbutyl) aminosulfone group, N- (2-hydroxyethyl) aminosulfone group, N- (2
-Cyanoethyl) lower alkylaminosulfone group such as aminosulfone group.

More specifically, the five-membered ring consisting of a nitrogen atom and Y or Y 'includes an indoline ring (Y, Y'
Is CR ₄ R ₅ , A ₁ and A ₂ or A ₃ and A ₄ form a benzene ring), and a benzoindoline ring (Y and Y ′ are CR ₄
In R ₅ , A ₁ and A ₂ or A ₃ and A ₄ form a naphthalene ring), a thiazole ring (Y and Y ′ are S), a benzothiazole ring (Y and Y ′ are S and A ₁ and A ₂ Or A ₃ and A ₄
Forms a benzene ring), a naphthothiazole ring (Y, Y ′
Is S, A ₁ and A ₂ or A ₃ and A ₄ form a naphthalene ring), an oxazole ring (Y and Y ′ are O), a benzoxazole ring (Y and Y ′ are O and A ₁ and A ₂ Or A ₃ and A ₄ form a benzene ring), a naphthoxazole ring (Y and Y ′ are O and A ₁ and A ₂ or A ₃ and A ₄ form a naphthalene ring), an imidazole ring (Y and Y ′ Is N
R ₆ ), a benzimidazole ring (Y and Y ′ are NR ₆₎
A ₁ and A ₂ or A ₃ and A ₄ form a benzene ring), a naphthoimidazole ring (Y and Y ′ are NR ₆ and A ₁ and A ₂
Or A ₃ and A ₄ form a naphthalene ring), a selenazole ring (Y and Y ′ are Se), a benzoselenazole ring, a naphthoselenazole ring and the like.

The benzene or naphthalene ring formed by A ₁ and A ₂ or A ₃ and A ₄ may have a substituent. Specific examples of the substituent include halogen such as fluorine, chlorine, bromine, and iodine, an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, and an arylthio group. X is a halogen ion,
Monovalent anions such as perchlorate ions, phosphonium ions, sulfonium ions, and metal dithiol complex anions known as singlet oxygen quencher are exemplified.

In the present invention, a recording layer containing the above-mentioned dye is provided on a substrate directly or via an inorganic or organic undercoat layer. The method for providing the recording layer includes, for example, a spin coating method, a dipping method, a spraying method, and a vapor deposition method, and the spin coating method is preferable. The coating solvent used for forming a film by spin coating is not particularly limited as long as it does not damage the substrate. Preferred solvents include, for example, alcohol solvents such as ethyl alcohol, propyl alcohol, butyl alcohol, furfuryl alcohol, ethylene glycol monomethyl ether, and tetrafluoropropanol. If a non-polar group is added to the side chain of the dye, it is possible to use an aliphatic hydrocarbon solvent such as hexane having a lower polarity than the alcohol solvent, or an ether solvent such as dibutyl ether. These solvents may be used alone or as a mixture of two or more solvents.

In forming the recording layer, a binder can be used together if necessary. Preferred binders include nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polyvinyl butyral, polycarbonate, polyolefin and the like. Further, other dyes can be added for improving recording characteristics and the like. The thickness of the recording layer affects the degree of modulation and the reflectance, but in the present invention, the thickness on the groove is 40 nm to 300 nm.
m, preferably 60 nm to 200 nm. When forming the recording layer on the substrate, a layer made of an inorganic substance or a polymer may be provided on the substrate in order to improve the solvent resistance, the reflectance, the recording sensitivity, and the like of the substrate.

In the present invention, a light interference layer may be provided between the recording layer containing the dye and the reflection layer in order to improve the characteristics such as the reflectance and the degree of modulation. Examples of a material for forming the light interference layer include an inorganic dielectric, a polymer, and a dye. In the present invention, a reflective layer is provided on the recording layer. As the reflective layer, metals such as gold, silver, aluminum, copper and platinum and alloys containing these metals are used. From the viewpoint of efficiency and durability, gold, aluminum, silver and alloys containing these metals as main components are preferable. The thickness of the reflective layer is usually 40 nm to 300 nm, preferably 60 nm to 200 nm. Examples of the method for forming the reflective layer include vacuum deposition, sputtering, and ion plating.

In the present invention, since the numerical aperture of the objective lens is large and the aberration is reduced, the thickness of the substrate is
It is preferably about 0.5 to 0.8 mm. At this time, in order to improve the strength and mechanical properties of the medium, the two sheets may be bonded using an adhesive. In bonding, the bonding can be performed without forming a protective layer on the reflective layer or after forming the protective layer. As the protective layer, an ultraviolet curable acrylic resin, an ultraviolet curable epoxy resin, a silicone hard coat resin, or the like is used. In addition, as an adhesive for bonding, an ultraviolet curable acrylic resin, an ultraviolet curable epoxy resin, a hot melt adhesive, or the like is used. The optical recording medium of the present invention thus obtained is
By focusing the laser beam on the recording layer, recording and reproduction can be performed at a much higher density than the beam diameter. Signals for recording include, for example, CDs and DVDs.
The modulation signal used for the above is preferable for achieving the effects of the present invention.

[0039]

EXAMPLES The present invention will be described below in more detail with reference to examples, but embodiments of the present invention are not limited thereto. Example 1 While rotating this resin substrate on the grooved surface of an injection-molded polycarbonate substrate having a spiral groove (depth 150 nm, pitch 0.74 μm) having a thickness of 0.6 mm and a diameter of 120 mm, the following formula (2) was used. Dye 1 represented by (Chemical Formula 3), that is, 3-ethyl-2- [2-[(3-ethylnaphtho [2,1-d] thiazole-2- (3H) -ylidene) methyl] trimethinecyanine dye -1-butenyl] naphtho [2,1-d] thiazolium iodide (NK-1056, manufactured by Japan Photographic Dye Laboratory Co., Ltd.)
A solution in which 5.0% by weight of 2,2,3,3-tetrafluoro-1-propanol was dissolved was dropped and spin-coated to form a dye layer on the substrate (groove film thickness 130 nm, land film thickness).
50 nm). The refractive index of the dye at 635 nm, nabs
Was 2.2 and the refractive index nsub of the substrate was 1.6.

[0040]

Embedded image

On this recording layer, a 80 n thick reflective layer
After forming a gold thin film of m by sputtering, an ultraviolet curing adhesive was applied on this reflective layer. The same 0.6 mm substrate as described above was superimposed on this adhesive, spin-coated at a high speed, and then irradiated with ultraviolet rays to produce an optical recording medium. This optical recording medium is put on a turntable and rotated at a linear speed of 3.5 m / s. An optical disk manufactured by Pulstec Industrial, equipped with a semiconductor laser having an oscillation wavelength of 635 nm and an optical head consisting of an objective lens with NA of 0.6. Evaluation device (DDU-1000) and KENWOOD
After recording an EFM modulated signal with a minimum pit length of 0.44 μm while changing the recording laser power while controlling the laser beam to focus on the recording layer on the groove using the EFM encoder manufactured by The recorded signal was read out at a laser output of 0.5 mW using. Note that when reading, an equalization process was performed. When the recording power is 9.0 mW laser output, the error rate is the smallest (optimal recording power), the byte error rate is 5 × 10 ^-4 , and the jitter at that time is the rising and falling of the pits and the channel bit clock. 8%. The reflectance of the unrecorded area is 52%, and the modulation degree of the shortest pit (I3 / Itop = [(maximum intensity of 3T signal)-(minimum intensity of 3T signal)] / (maximum intensity of 11T signal)) is 22%. There was good recording and reproduction. Almost no distortion was observed in the reproduced waveform. The unrecorded RCb was 0.07, and tracking was stable. The error rate was measured using a Kenwood CD decoder (DR3552), and RCb was determined by the following equation. RCb = 2 (Il-Ig) / (Il + Ig) Il: Unrecorded land reflection potential Ig: Unrecorded groove reflection potential In this case, dsub is 0.14r, P is 0.70r, and ΔT is
It is 0.20.

Examples 2 to 5 and Comparative Examples 1 to 3 In Example 1, a medium was prepared in the same manner as in Example 1 except that a groove-shaped substrate shown in Table 1 (Tables 1 and 2) was used. Made and evaluated. At this time, the dye 2: 5,6-dichloro-2- [3- represented by the following formula (3)
(5,6-dichloro-1,3-diethyl-2 (3H)-
Benzimidazooilidene) -1-propenyl] -1,
3-Diethylbenzimidazolium iodide (NK-1420, manufactured by Japan Photographic Dye Laboratories), dye 3: 2- [3- (1,3) represented by the following formula (4)
-Dihydro-1,3,3-trimethyl-2H-indole-2-ylidene) -1-propenyl] -1,3,3-
Trimethyl-3H-indolium iodide (NK-79, manufactured by Japan Photosensitive Dye Laboratories, Inc.), the following formula (5)
Dye 4: 3-ethyl-2- [3-
(3-Ethyl-2 (3H) -benzoxazolylidene) -1-propenyl] benzoxazolium iodide (NK-85, manufactured by Japan Photographic Dye Laboratory Co., Ltd.) was used.

[0043]

Embedded image

In Comparative Example, Dye 1 was prepared according to the following formula (6).
Dye 5 represented by the following formula (5): 1-ethyl-2- [5-
(1-Ethylnaphtho [1,2-d] thiazole-2 (1
H) -Ilidene) -1,3-pentadiethyl] naphtho [1,2-d] thiazolium iodide (NK-2409, manufactured by Japan Photographic Dye Laboratories, Inc.), the following formula (7)
Dye 6: 1-ethyl-4- [5-
(1-ethyl-4 (1H) -quinolinylidene) -1,3
-Pentadiethyl] quinolinium iodide (NK-1144, manufactured by Japan Photographic Dye Laboratories, Inc.), dye 7: 1-ethyl-2- represented by the following formula (8)
[3- (1-Ethyl-2 (1H) -quinolinylidene)-
1-Propenyl] quinolinium iodide (NK-3, manufactured by Japan Photographic Dye Laboratory Co., Ltd.) was used. The result is the second
The results are summarized in Table (Table 3). As is clear from Table 2, in the example of the present invention, extremely good recording and reproduction were performed, but in the comparative example, the modulation degree of the shortest pit (I3 / Itop) was obtained.
And the error rate and jitter were large, and good recording and reproduction could not be performed. In some comparative examples, tracking during recording was unstable due to low radial contrast (RCb).

[0045]

Embedded image

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

Examples 5 to 7 and Comparative Example 6 Dyes 2, 3, and 4 and a phthalocyanine dye of Dye 8 represented by the following formula (9) were used as dyes for the recording layer, and a track pitch was used. A medium was prepared and evaluated in the same manner as in Example 1 except that a substrate having a thickness of 0.8 μm and a depth of 150 nm was used. The evaluation was 633 while rotating at a linear speed of 3.5 m / s.
A semiconductor laser having an oscillation wavelength of nm and an NA of 0.63
Example 1 was performed except that an optical disk evaluation device (DDU-1000) manufactured by Pulstec Industrial Co., Ltd. equipped with an optical head including the objective lens was used. In this case, dsub is 0.15r, P is 0.80r, and the dye film thickness and ΔT
Are summarized in Table 3 (Table 4). The evaluation results are summarized in Table 4 (Table 5). As is clear from Table 4, in the embodiment of the present invention, extremely good recording and reproduction were performed.
In the comparative example, the reflectance was low, the signal waveform was dirty, and the modulation of the shortest pit (I3 / Itop) and jitter could not be measured.

[0050]

Embedded image

[0051]

[Table 4]

[0052]

[Table 5]

Example 8 A medium was prepared and evaluated in the same manner as in Example 1 except that Dye 1 was used as a dye for the recording layer. The evaluation was carried out while rotating at a linear velocity of 3.5 m / s, an optical disk evaluation device (DDU-1 manufactured by Pulstec Industrial Co., Ltd.) equipped with a semiconductor laser having an oscillation wavelength of 633 nm and an optical head comprising an objective lens with an NA of 0.68.
000) was used, except that 000) was used. d
sub is 0.14r, P is 0.74r, and the groove film thickness is 130n.
m, the land thickness was 45 nm, and ΔT was 0.14. The error rate was the smallest when the recording power was 8.5 mW, and the byte error rate was 6 × 10 ^-4 , and the jitter at that time was 9.0% of the channel bit clock. The reflectivity of the unrecorded area was 50%, and the modulation degree of the shortest pit was 20%. Almost no distortion was observed in the reproduced waveform.

[0054]

According to the present invention, in an optical recording medium having a recording layer containing at least a dye and a reflective layer on a substrate, the track pitch and groove depth are set to λ / NA.
The recording beam diameter (λ is the recording wavelength, NA is the numerical aperture of the objective lens), the optical phase difference including the recording layer, and the type of dye are limited by An optical recording medium which is stable in tracking and has good recording characteristics and capable of high-density recording is realized.

[Brief description of the drawings]

FIG. 1 is a sectional structural view showing a layer configuration of an optical recording medium of the present invention.

FIG. 2 is a sectional structural view showing a layer configuration of the optical recording medium of the present invention.

[Explanation of symbols]

 1: substrate 2: recording layer 3: reflective layer 4: protective layer 1 ': substrate 2': recording layer 3 ': reflective layer 4': adhesive layer 5 ': substrate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiteru Taniguchi 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Tomoyoshi Sasakawa 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Within Chemical Co., Ltd. (72) Inventor Sumio Hirose 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. A recording layer containing a dye that absorbs laser light directly or via another layer on a substrate having a spiral groove formed thereon, and directly or via another layer on the recording layer. In an optical recording medium having a metal reflective layer,
The diameter of the recording beam represented by λ / NA is r (where λ is the recording wavelength (μm), NA is the numerical aperture of the objective lens), the pitch of the groove of the substrate is P (μm), and the depth of the groove is Is dsub (μm), the dye film thickness at the groove portion of the recording layer is dg (μm), and the dye film thickness at the land portion is dl (μm).
m), assuming that the refractive index of the recording layer at the wavelength λ is nabs and the refractive index of the substrate is nsub, the following relationship is established: 0.66r ≦ P ≦ 0.89r 0.12r ≦ dsub ≦ 0. 20r 1.8 ≦ nabs ≦ 2.7 Also, the optical phase difference (ΔT) = 2 [nsub · dsub + nab
s (dl−dg)] / λ is 0.13 ≦ ΔT ≦ 0.41
And dg-dl≤dsub, and the dye contained in the recording layer is a trimethinecyanine compound represented by the general formula (Formula 1). Embedded image [Wherein, Y and Y ′ are each CR ₄ R ₅ , O, S, S
e or NR ₆ , wherein R _{1 to} R ₆ are a hydrogen atom or an unsubstituted or substituted alkyl group having 1 to 12 carbon atoms, A ₁ to
A ₄ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, A ₁ and A ₂ , A ₃ and A ₄ may form an unsubstituted or substituted benzene ring or a naphthalene ring;
Represents a monovalent anion. However, when R ₁ is a monovalent anionic substituent, X does not exist.] 2. λ is 0.630 to 0.655 μm, NA
2. The high-density optical recording medium according to claim 1, wherein is 0.58 to 0.70.