JPH10181203A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high density recording with good recording characteristics while stabilizing tracking at the time of recording by defining a tracking pitch and a groove depth for the diameter of a recording beam thereby defining the optical phase difference including a recording layer and limiting the type of coloring matter. SOLUTION: Assuming the diameter of a recording beam represented by λ/NA is r (λ is the recording wavelength (μm) and NA is the numerical aperture of an objective), the pitch of groove in a substrate is P(μm), the depth of groove is dsub (μm), the thickness of coloring matter layer at the groove part of a recording layer is dg (μm), the thickness of coloring matter layer at the land part is d1 (μm), and the refractive index of the recording layer at the wavelength λis nabs , following relationships are satisfied; 0.66r<=P<=0.89r, 0.12r<=dsub <=0.20r, 1.8<=nabs <=2.7. Furthermore, following relationships are also satisfied; 0.13<=ΔT<=0.14 and dg -d1 <=dsub , where ΔT is the optical phase difference. Coloring matter contained in the recording layer is an azo compound shown by a formula (description of symbols in the formula is omitted) or a metal complex thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 dye is used as a recording layer 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 T
echnical Digest Series Vol.1, 45 (1989),
Media using a cyanine dye or a phthalocyanine dye in the recording layer are commercially available as CD-R media. 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.

However, these media have a capacity of only about 650 MB, and the recording time for recording large-capacity information such as digital moving images is as short as 15 minutes or less. 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 conventional CD-R media described above is
Recording and reproduction were performed using a semiconductor laser having a wavelength of around 780 nm. Recently, semiconductor lasers with a wavelength of 630 to 655 nm have been developed, enabling higher-density recording and / or reproduction. An optical recording medium on which a 2-hour high-quality moving image is recorded 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.
Therefore, there is a need for a recordable optical recording medium having a large capacity close to the recording capacity of a read-only DVD as described above.

In general, to increase the recording capacity of a recordable medium, the recording laser beam may be reduced. The shorter the wavelength of the laser used and the larger the numerical aperture (NA) of the objective lens, the smaller the beam diameter, 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 is not small compared to the conventional CD in comparison with the recording density. Therefore, at the time of recording, smaller pits must be accurately formed in comparison with the beam diameter as compared with the case of the CD-R. But,
As the size of the pits becomes smaller, the modulation degree of the shortest pit 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 that positions the laser along the groove during recording,
It is desired that the unrecorded radial contrast (RCb) is greater than 0.05.

[0005] An optical recording medium using a metal complex of an azo compound having a nitrogen-containing heterocycle as a recording layer is disclosed in Japanese Patent Publication No. 5-67438 and Japanese Patent Publication No. 07-71868. However, the document only describes the conventional recording at a near-infrared laser wavelength, but does not specifically disclose various conditions for increasing the recording density.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to achieve stable tracking during recording even if the track pitch is reduced with respect to the recording beam diameter, and to provide a good pit when smaller pits are formed than before. An object of the present invention is to provide a high-density optical recording medium having recording characteristics.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have optimized the recording beam diameter, track pitch, groove shape and dye, and
The present invention has been proposed. That is, the present invention provides a recording layer containing a dye that absorbs laser light, 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, λ /
The diameter of the recording beam represented by NA is r (where λ is the recording wavelength (μm), NA is the numerical aperture of the objective lens), and the pitch (track pitch) of the groove of the substrate is P (μ
m), the depth of the groove is d _sub (μm), the dye film thickness of the groove portion of the recording layer is d _g (μm), the dye film thickness of the land portion is d _l (μm), and the recording layer is at a wavelength λ. _Is n _abs and the refractive index of the substrate is n _sub , P, d _sub
And n _abs satisfy the following formula: 0.66r ≦ P ≦ 0.89r 0.12r ≦ d _sub ≦ 0.20r 1.8 ≦ n _abs ≦ 2.7 Optical phase difference (ΔT) = 2 [n _sub · d _sub + n _abs (d
_l −d _g )] / λ is represented by the formula 0.13 ≦ ΔT ≦ 0.41, d _g −d _l ≦ d _sub , and the dye contained in the recording layer is represented by the following formula ( 1) A high-density optical recording medium characterized by being an azo compound represented by the following formula (3) or a metal complex thereof:

[0008]

Embedded image Wherein R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted allyl group,
Represents a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, and R ₃ , R ₄ , R ₅ and R ₆ each independently represent a hydrogen atom, a halogen atom, a hydroxy group, a carboxyl group, a sulfonamide group, an amino group; Group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkoxy group,
Substituted or unsubstituted allyl group, substituted or unsubstituted acyl group, substituted or unsubstituted alkylcarboxyl group, substituted or unsubstituted aralkyl group, substituted or unsubstituted alkylcarbonylamino group, substituted or unsubstituted alkylsulfone Represents an amino group, a substituted or unsubstituted alkylamino group, a substituted or unsubstituted alkylsulfone group, or a substituted or unsubstituted alkenyl group, wherein R ₁ and R ₄ , R ₂ and R _6, and R ₁ and R ₂ are linked; A ring may be formed via a group. R ₇ , R ₈ and R ₉ each independently represent a hydrogen atom, a halogen atom, a hydroxy group, a carboxyl group, a sulfone group, a sulfonamide group, an amino group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, Substituted or unsubstituted allyl group, substituted or unsubstituted acyl group, substituted or unsubstituted alkylcarboxyl group, substituted or unsubstituted aralkyl group, substituted or unsubstituted alkylcarbonylamino group, substituted or unsubstituted alkylsulfone Amino group, substituted or unsubstituted alkylamino group, substituted or unsubstituted alkylsulfone group, substituted or unsubstituted alkenyl group, cyano group, nitro group, mercapto group, thiocyano group, chlorosulfonic acid, substituted or unsubstituted Alkylthio group, substituted or unsubstituted alkylazomethine group, substituted or unsubstituted Alkyl amino sulfone group, R ₇ and R _8, R ₈ and R ₉ may form a ring through a linking group. The high-density optical recording medium according to the above, wherein the dye contained in the recording layer is a metal complex of an azo compound represented by the following formula (2):

[0009]

Embedded image [Wherein R ₁ , R ₂ , R ₄ , R ₆ , R ₇ , R ₈ and R ₉
Has the same meaning as in formula (1), one of R ₁₀ and R ₁₁ represents a hydroxy group or a carboxyl group, and the other represents a hydrogen atom. Λ is 0.630 to 0.655 μm, NA is 0.58
Or a high-density optical recording medium as described in or above.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording medium according to the present invention has a recording layer containing a dye and a reflective layer on a substrate in which grooves are formed in a spiral shape. Even when the pitch is reduced, tracking at the time of recording is stable with an appropriate value of the radial contrast (RCb) value, and when a smaller pit is formed than before, the modulation degree is large, and the jitter and error rate are good. This enables high-density recording.

The layer structure of the optical recording medium of the present invention is shown in FIG.
Substrate 1, recording layer 2, reflective layer 3, and protective layer 4 as shown in FIG.
Are sequentially laminated, or a substrate 1 ', a recording layer 2', and a reflective layer 3 'are sequentially laminated as shown in FIG. 2 (FIG. 2), and a substrate 5' is formed thereon via an adhesive layer 4 '. Are bonded to each other.

When a dye is used for the recording layer, the recording layer can be formed by spin coating. When a recording layer is formed by a spin coating method on a substrate having a groove,
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). Normally, 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 the 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. This is because, even if the track pitch is reduced indefinitely, 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.

In the present invention, in order to perform recording so as to reduce crosstalk and improve jitter without sacrificing the degree of modulation at the time of reproduction, the recording beam diameter represented by λ / NA must be set to r.
Then, the pitch of the groove (track pitch) (P)
Is preferably set to 0.66r to 0.89r. If the track pitch is less than 0.66r, the jitter and error rate increase, which is not preferable. If the track pitch exceeds 0.89r, the recording density in the radial direction does not increase, and the desired recording capacity cannot be obtained.

Further, as shown in FIG. 1, the depth of the groove portion of the substrate is d _sub (μm), the dye film thickness of the groove portion of the recording layer is d _g (μm), and the dye film of the land portion is Thickness d
_l (μm), the refractive index of the recording layer at the wavelength λ is n _abs , and the refractive index of the substrate is n _sub , in order to obtain a sufficient degree of modulation and radial contrast (RCb), d _{su b}
Is preferably set to 0.12r to 0.20r. Further, the optical distance (X _p ) of the groove is n _abs · d _g , and the optical distance (X _l ) of the land is n _sub · d _sub +
because it is n _abs · d _l, when irradiated with a laser beam having a wavelength λ from the substrate side, the optical phase difference between the laser beam reflected by the portion and the land portion of the groove by the reflecting layer 3 (△ T =
2 (X _l -X _p ) / λ) is △ T = 2 [n _sub · d _sub + n _abs
(d _l -d _g )] / λ (where d _g -d _l ≤
d _sub ), and the range of ΔT is 0.13 to
It is preferably 0.41. That is, the organic dye layer undergoes changes such as decomposition, combustion, and deformation by the recording laser beam,
Since the difference between the reflectance and the unchanged portion becomes the degree of modulation of the signal, it is necessary to take a sufficient optical path length of the dye film in order to obtain a large degree of modulation. In addition, unrecorded R
In consideration of the optical phase difference for sufficiently obtaining Cb, it is preferable that the above-described conditions of the depth of the substrate and the optical phase difference are satisfied. When the depth of the groove is less than 0.12r, the modulation factor and RCb are small, and the jitter characteristic is also deteriorated. If it exceeds 0.20r, it will be difficult to reduce the reflectance and form the substrate. When ΔT is less than 0.13, the modulation degree and RCb cannot be sufficiently obtained, and when it exceeds 0.41, the reflectance is reduced.

At the wavelength λ of the laser light, the refractive index n _abs 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. If n _abs is smaller than 1.8, a large reflectance and signal modulation cannot be obtained, and accurate signal reading cannot be performed. In addition, the extinction coefficient (k _abs) is 0.04
It is preferably 0.20. If k _abs is less than 0.04, the recording sensitivity is remarkably reduced, and recording is difficult with the current output of the semiconductor laser. If k _abs is more than 0.20, the reflectance required for accurate signal reading cannot be obtained. Instead, 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 is shorter and the numerical aperture (NA) of the objective lens is larger, which is preferable for high-density recording. As a high-output laser that can be used for recording from the viewpoint that the optical system can be simplified and the economical efficiency of the device, a semiconductor laser of 0.630 to 0.655 μm is preferable, and 0.630 to 0.640 μm is preferable. More preferred. Further, the upper 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. In the present invention, NA is preferably 0.58 to 0.70.

The substrate used in the optical recording medium of the present invention has a light transmittance for recording and reading signals.
Those having 85% or more and small optical anisotropy are preferred.
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 plate-like or film-like, 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. Although the track pitch and the depth of the groove have been described above, the width of the groove is preferably about 0.25 to 0.37 μm.

In the present invention, the recording layer contains a dye, and the dye used in the recording layer is important in terms of recording sensitivity, reflectance, modulation degree, and the like. In high-density recording, a large degree of modulation is obtained when pits of the same size are formed, and a dye excellent in threshold characteristics is particularly preferable. A complex or a metal complex of the azo compound represented by the formula (2) is preferable.

The substituted or unsubstituted alkyl group includes
A linear, branched or cyclic alkyl group having 1 to 15 carbon atoms,
Alkoxyalkyl group, alkoxyalkoxyalkyl group, alkoxyalkoxyalkoxyalkyl group, alkoxycarbonylalkyl group, alkoxycarbonyloxyalkyl group, alkoxyalkoxycarbonyloxyalkyl group, hydroxyalkyl group, hydroxyalkoxyalkyl group, hydroxyalkoxyalkoxyalkyl group, cyanoalkyl Group, acyloxyalkyl group, acyloxyalkoxyalkyl group, acyloxyalkoxyalkoxyalkyl group, halogenated alkyl group, sulfonealkyl group, alkylcarbonylaminoalkyl group, alkylsulfonaminoalkyl group, sulfonamidoalkyl group, alkylaminoalkyl group, aminoalkyl And alkylsulfonalkyl groups.

Here, the linear, branched or cyclic alkyl group is a hydrocarbon group having 1 to 15 carbon atoms, such as a methyl group,
Ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, t-butyl, n-pentyl, iso-pentyl, 2-methylbutyl, 1-methylbutyl, neo-
Pentyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, cyclopentyl, n-hexyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl , 3,3-dimethylbutyl group, 2,3-
Dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 1,2-dimethylbutyl, 1,1-dimethylbutyl, 3-ethylbutyl, 2-ethylbutyl, 1-ethylbutyl , 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, 5-methylhexyl, 2,4-dimethylpentyl, n-octyl, 2-ethylhexyl, 2,5-dimethylhexyl, 2,5,5-trimethylpentyl, 2 , 4-dimethylhexyl group, 2,2,4-trimethylpentyl group, n-nonyl group, n-decyl group, 4-ethyloctyl group, 4-ethyl-4,5-methylhexyl group, n-undecyl group, n-dodecyl group, 1,3,5,7-tetraethyloctyl group, 4-butyloctyl group, 6,6-diethyloctyl group, n-
Tridecyl group, 4-butyl-6-methyloctyl group, n-tetradecyl group, n-pentadecyl group, 3,5-dimethylheptyl group, 2,6-dimethylheptyl group, 2,4-dimethylheptyl group, 2,2 , 5,5-tetramethylhexyl group, 1-cyclopentyl-2,2-dimethylpropyl group, 1-cyclohexyl-2,2-
And a dimethylpropyl group.

Examples of the alkoxyalkyl group include methoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl, methoxyethyl, ethoxyethyl,
Propoxyethyl group, butoxyethyl group, n-hexyloxyethyl group, 4-methylpentoxyethyl group, 1,3-dimethylbutoxyethyl group, 2-ethylhexyloxyethyl group, n-octyloxyethyl group, 3,5, 5-trimethylhexyloxyethyl group, 2-methyl-1-isopropylpropoxyethyl group, 3-methyl-1-isopropylbutyloxyethyl group, 2-ethoxy-1-methylethyl group, 3-methoxybutyl group, 3,3 , 3-trifluoropropoxyethyl group, 3,
2-1 carbon atoms such as 3,3-trichloropropoxyethyl group
5 are mentioned.

Examples of the substituted or unsubstituted alkylsulfonamino group include alkylsulfonamino groups having the same substituents as the above-mentioned alkyl groups, such as methylsulfonamino group, ethylsulfonamino group,
n-propyl sulfone amino group, isopropyl sulfone amino group, n-butyl sulfone amino group, isobutyl sulfone amino group, sec-butyl sulfone amino group, t-butyl sulfone amino group, n-pentyl sulfone amino group, isopentyl sulfone amino group And lower alkylsulfonamino groups such as neopentylsulfonamino group, 2-methylbutylsulfonamino group, and cyclohexylsulfonamino group.

Examples of the substituted or unsubstituted alkylamino group include an alkylamino group having the same substituent as the above-mentioned alkyl group. Examples thereof include an N-methylamino group and an N, N-dimethylamino group. , N, N-diethylamino group, N,
And lower alkylamino groups such as N-dipropylamino group and N, N-dibutylamino group.

Examples of the substituted or unsubstituted alkylsulfone groups include alkylsulfone groups having the same substituents as the above-mentioned alkyl groups, such as methylsulfone group, ethylsulfone group and n-propylsulfone group. , Isopropyl sulfone group, n-butyl sulfone group, isobutyl sulfone group, sec-butyl sulfone group, t-butyl sulfone group, n-pentyl sulfone group, isopentyl sulfone group, neopentyl sulfone group, 2-methylbutyl sulfone group, And lower alkylsulfone groups such as a 2-hydroxyethylsulfone group and a 2-cyanoethylsulfone group.

Examples of the substituted or unsubstituted alkenyl groups are alkenyl groups having the same substituents as the above-mentioned alkyl groups, and include, for example, propenyl group, 1-butenyl group, isobutenyl group and 1-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-methylcarboxyl vinyl group, 2-cyano-2
-Lower alkenyl groups such as methylsulfonevinyl groups.

Examples of the substituted or unsubstituted alkylthio groups are the alkylthio groups having the same substituents as the above-mentioned alkyl groups, such as methylthio, ethylthio, n-propylthio, isopropylthio, n-
Butylthio group, isobutylthio group, sec-butylthio group,
and lower alkylthio groups such as a t-butylthio group, an n-pentylthio group, an isopentylthio group, a neopentylthio group, a 2-methylbutylthio group, and a methylcarboxylethylthio group.

Examples of the substituted or unsubstituted alkylazomethine group include alkylazomethine groups having the same substituents as the above-mentioned alkyl groups, such as methylazomethine group, ethylazomethine group and n-propylazomethine group. , Isopropylazomethine group, n-butylazomethine group, isobutylazomethine group, sec-butylazomethine group, t-butylazomethine group, n-pentylazomethine group,
Lower alkyl azomethine groups such as isopentyl azomethine group, neopentyl azomethine group, 2-methylbutyl azomethine group, and hydroxy azomethine group.

Examples of the substituted or unsubstituted alkylaminosulfone groups include alkylaminosulfone groups having the same substituents as the above-mentioned alkyl groups, such as N-methylaminosulfone group and N-ethylamino group. Sulfone group, N- (n-propyl) aminosulfone group, N- (isopropyl) aminosulfone group, N- (n-butyl) aminosulfone group, N- (isobutyl) aminosulfone group, N- (sec-butyl) Amino sulfone group, N- (t-butyl) amino sulfone group, N- (n-pentyl) amino sulfone group, N- (isopentyl) amino sulfone group, N- (neopentyl) amino sulfone group, N- (2-methylbutyl) ) Aminosulfone group,
And lower alkylaminosulfone groups such as N- (2-hydroxyethyl) aminosulfone group and N- (2-cyanoethyl) aminosulfone group.

Examples of the ring in which R ₁ and R ₄ or R ₂ and R ₆ form a linking group include a substituted or unsubstituted alkylene chain having 2 or 3 carbon atoms. R ₁ and R
Examples of the case where ₂ forms a ring via a linking group include a group forming a 6-membered ring composed of a substituted or unsubstituted carbon atom, oxygen atom and nitrogen atom. R ₇ and R ₈ or R ₈
And R ₉ form a ring via a linking group, for example, a ring forming a substituted or unsubstituted benzene ring, a substituted or unsubstituted naphthalene ring, or a substituted or unsubstituted cyclohexine ring.

The azo compounds represented by the formulas (1) and (2) of the present invention can be produced by a known method. That is, the amine component represented by the formula (3) (Chemical Formula 5) is diazotized, added to a solution of the coupling component represented by the formula (4) (Chemical Formula 5), and subjected to a coupling reaction to be represented by the formula (1). Is obtained.

[0033]

Embedded image [In the above formula, R _{1 to} R ₉ represent the same meaning as in formula (1). ]

In the present invention, the method for producing the metal complex of the azo compound is a known method, for example, Furukawa;
a It can be produced according to the method described in Chimica Acta 140 (1982) 281-289, and the like. Examples of the metal forming the metal complex of the azo compound include nickel, cobalt,
Metals such as iron, ruthenium, rhodium, palladium, copper, osmium, iridium, platinum, zinc, magnesium and manganese are preferred, and nickel, cobalt, copper, palladium, iron, zinc and manganese are particularly preferred. These metals form a complex coordinated to the azo compound as an ion. The metal complex of the azo compound may be used alone or as a mixture of a plurality of compounds. Further, a quencher such as a dithiol complex may be mixed.

In the present invention, a recording layer containing the above-mentioned dye is provided directly on the substrate or via another inorganic or organic layer (undercoat layer). The method for providing the recording layer includes, for example, a spin coating method, an immersion method, a spray method, and a vapor deposition method, and the spin coating method is preferable.

The coating solvent for forming a film by spin coating is not particularly limited as long as it does not damage the substrate. Preferred solvents include alcohol solvents such as ethyl alcohol, propyl alcohol, butyl alcohol, furfuryl alcohol, ethylene glycol monomethyl ether, and tetrafluoropropanol.

When 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 pre-groove is 40 nm to 300 nm, preferably 60 nm to 200 nm.

When the recording layer is formed 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 reflective layer is provided directly on the recording layer or via another layer. The reflective layer may be made of a metal such as gold, silver, aluminum, copper, platinum or the like. Although an alloy containing a metal is used, gold, aluminum, silver, and an alloy containing these metals as main components are preferable in terms of reflectance and durability. The thickness of the reflective layer is usually 40 nm
300300 nm, preferably 60 nm-200 nm. The method for forming the reflective layer includes, for example, vacuum deposition, sputtering, and ion plating.

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, since the numerical aperture of the objective lens is large, the thickness of the substrate is set to 0.5 to reduce aberration.
It is preferably about 0.8 mm. At this time, in order to improve the strength and mechanical properties of the medium, two sheets may be attached to each other 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 can perform recording and reproduction at a much higher density than the beam diameter by focusing the laser beam on the recording layer. Signals for recording include, for example, CDs and DVs.
A modulated signal used for D or the like is preferable for achieving the effects of the present invention.

[0043]

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 a surface having a groove 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 ( 5) A 1.5 wt% 2,2,3,3-tetrafluoro-1-propanol solution of a Ni complex of an azo dye represented by the formula (6) is dropped, and a recording layer consisting essentially of the dye is dropped on the substrate. Was formed (groove film thickness: 120 nm, land film thickness: 40 nm). The refractive index (n _abs ) of the recording layer at 635 nm was 2.3, and the refractive index (n _sub ) of the substrate was 1.58.

[0044]

Embedded image

After a gold thin film having a thickness of 80 nm was formed as a reflective layer on the recording layer by sputtering, an ultraviolet curing adhesive was applied on the reflective layer. The same 0.6 mm substrate as described above was overlaid on this adhesive, rotated at high speed to remove excess adhesive, and then irradiated with ultraviolet rays to produce an optical recording medium which was bonded.

This optical recording medium is put on a turntable,
While rotating at a linear velocity of 3.0 m / s, an optical disk evaluation device (DDU-1000) manufactured by Pulstec Industrial and an EFM manufactured by KENWOOD equipped with an optical head composed of a semiconductor laser having an oscillation wavelength of 635 nm and an objective lens having an NA of 0.6 while rotating at a linear speed of 3.0 m / s. An EF with a minimum pit length of 0.40 μm while changing the recording laser power while controlling the laser beam to focus on the recording layer on the groove through the substrate using the encoder
After recording the M-modulated signal, the recorded signal was read out using the same device at a laser output of 0.5 mW.
Note that when reading, an equalization process was performed. When the recording power is 7.5mW laser output, the error rate is the smallest (optimum recording power), and the byte error rate is
4 × 10 ^-4 , and the jitter at that time, both rising and falling of the pit, was 7.4% of the channel bit clock. The reflectance of the unrecorded part is 50%, the modulation degree of the shortest pit (I3 / Itop = [(3T signal maximum intensity)-(3T signal minimum intensity)]
/ (Maximum intensity of 11T signal)) is 21%, good recording,
I was able to play. Almost no distortion was observed in the reproduced waveform. The unrecorded RCb was 0.08, and tracking was stable. The error rate was measured using a Kenwood CD decoder (DR3552),
b was determined by the following equation. RCb = 2 (Il-Ig) / (Il + Ig) Il: unrecorded land reflex potential Ig: unrecorded groove reflex potential also this P in this case is 0.70r, d _sub is 0.14r, △ T is
0.17.

(Examples 2 to 5 and Comparative Examples 1 to 3) A medium was prepared and evaluated in the same manner as in Example 1 except that a groove-shaped substrate shown in Table 1 was used. The results are summarized in (Table 2). As is clear from Table 2, extremely good recording and reproduction were possible in the example of the present invention, but the modulation degree (I3 /
Itop) is small, error rate and jitter are large,
Good recording and reproduction could not be performed. Also, in particular, Comparative Example 1
In this case, tracking during recording became unstable because RCb was small.

[0048]

[Table 1]

[0049]

[Table 2]

Examples 6 to 16 and Comparative Example 4 The azo compounds represented by the following formulas (6) to (11) and the azo compounds (Table 3) are shown as dyes used in the recording layer. A medium was prepared and evaluated in the same manner as in Example 1 except that a metal complex and a phthalocyanine dye were used, and a substrate having a track pitch of 0.8 μm and a depth of 150 nm was used.

The evaluation was performed while rotating at a linear speed of 3.0 m / s.
The procedure was performed in the same manner as in Example 1 except that an optical disk evaluation apparatus (DDU-1000) manufactured by Pulstec Industrial Co., Ltd. equipped with an optical head composed of a semiconductor laser having an oscillation wavelength of 3 nm and an objective lens having an NA of 0.63 was used.

[0052] In addition, P in this case is 0.80r, is d _sub 0.
15r, and the refractive index of the dye, the dye film thickness and ΔT are summarized in (Table 3). The evaluation results are summarized in (Table 4). As is clear from (Table 4), extremely good recording and reproduction were possible in the examples of the present invention, but in the comparative examples,
Since the modulation degree (I3 / Itop) of RCb or the shortest pit is small or the reflectance is small, the error rate and the jitter are increased, and actual measurement may not be possible.

[0053]

Embedded image

[0054]

[Table 3]

[0055]

[Table 4]

(Example 12) In Example 1, 633 nm
A medium is made in the same manner as in Example 1 except that an optical disk evaluation device equipped with an optical head including a semiconductor laser having an oscillation wavelength of and an objective lens having an NA of 0.68 is used.
evaluated. At that time, the modulation degree of the shortest pit (I3 / Itop)
25%, error rate 2 × 10 ^-4 and jitter 7.
It was 2%, and good recording and reproduction were possible. In this case,
P is 0.80 r, d _sub is 0.16 r, and ΔT is 0.17.

[0057]

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

[Brief description of the drawings]

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

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

[Explanation of symbols]

 DESCRIPTION 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 Hideki Umehara 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Toatsu Chemicals Co., Ltd. Within Chemical Co., Ltd. (72) Inventor Sumio Hirose 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] 1. A base in which grooves are formed spirally.
Absorbs laser light directly or through another layer on the plate
A recording layer containing a coloring matter, and
Is applied to an optical recording medium having a metal reflective layer via another layer.
And the diameter of the recording beam represented by λ / NA is r [here
Where λ is the recording wavelength (μm) and NA is the numerical aperture of the objective lens
Represents the pitch of the groove on the substrate (track pitch)
Is P (μm), and the depth of the groove is d._sub(Μm),
The dye thickness of the groove portion of the recording layer is d _g(Μm), land
The dye film thickness of d_l(Μm), refractive index of recording layer at wavelength λ
To n_abs, The refractive index of the substrate is n_subAnd P, d
_subAnd n_absSatisfies the following equation: 0.66r ≦ P ≦ 0.89r 0.12r ≦ d_sub≦ 0.20r 1.8 ≦ n_abs≦ 2.7 Optical phase difference (ΔT) = 2 [n_sub・ D_sub+ N_abs(d
_l-d_g)] / Λ is represented by the following formula: 0.13 ≦ ΔT ≦ 0.41;_g-D_l≦ d_subAnd the recording layer
Is a dye represented by the following formula (1)
Azo compound or a metal complex thereof.
Density optical recording medium. Embedded image[Wherein, R₁And R_TwoAre each independently a hydrogen atom, substituted or
Is an unsubstituted alkyl group, a substituted or unsubstituted allyl group,
Substituted or unsubstituted aralkyl group, substituted or unsubstituted
Represents an alkenyl group;_Three, R_Four, R_FiveAnd R₆Are each
Independently hydrogen, halogen, hydroxy, carbo
Xyl group, sulfonamide group, amino group, substituted or unsubstituted
A substituted alkyl group, a substituted or unsubstituted alkoxy group,
Substituted or unsubstituted allyl group, substituted or unsubstituted acyl
Group, substituted or unsubstituted alkylcarboxyl group,
Substituted or unsubstituted aralkyl groups, substituted or unsubstituted
Alkylcarbonylamino group, substituted or unsubstituted alkyl
Sulfonamino group, substituted or unsubstituted alkylamino
Groups, substituted or unsubstituted alkylsulfone groups,
Or an unsubstituted alkenyl group;₁And R_Four, R_TwoWhen
R₆And R₁And R_TwoMay form a ring via a linking group
No. R₇, R₈, R₉Are each independently a hydrogen atom or a halogen
Atom, hydroxy group, carboxyl group, sulfone group,
Rufonamide group, amino group, substituted or unsubstituted alkyl
Group, substituted or unsubstituted alkoxy group, substituted or unsubstituted
A substituted allyl group, a substituted or unsubstituted acyl group,
Or unsubstituted alkyl carboxyl group, substituted or unsubstituted
Substituted aralkyl groups, substituted or unsubstituted alkylcarbo
Nylamino group, substituted or unsubstituted alkyl sulfone
Amino group, substituted or unsubstituted alkylamino group,
Or unsubstituted alkylsulfone group, substituted or unsubstituted
Alkenyl group, cyano group, nitro group, mercapto group,
An cyano group, chlorosulfonic acid, a substituted or unsubstituted
Alkylthiomethine, substituted or unsubstituted alkylazomethine
Group, substituted or unsubstituted alkylaminosulfone group
Then R₇And R₈, R₈And R₉Forms a ring via a linking group
May be. ] 2. The dye contained in the recording layer is represented by the following formula (2):
2. The high-density optical recording medium according to claim 1, which is a metal complex of an azo compound represented by the following chemical formula (2). Embedded image [Wherein R ₁ , R ₂ , R ₄ , R ₆ , R ₇ , R ₈ and R ₉
Has the same meaning as in formula (1), one of R ₁₀ and R ₁₁ represents a hydroxy group or a carboxyl group, and the other represents a hydrogen atom. ] 3. λ is 0.630 to 0.655 μm, NA
3. The high-density optical recording medium according to claim 1, wherein is 0.58 to 0.70.