JP2000048406A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DRAW type optical recording medium which has a good recording characteristic (jitter characteristic) with a red laser of 620 to 690 nm and is capable of performing higher density recording than a CD. SOLUTION: When a recording beam diameter expressed by λ/NA is defined as (r), [where, λ represents the recording wavelength (μm) and Na represents the numerical aperture of an objective lens], the groove pitch of a substrate is defined as (p) (μm), the groove half-value width is defined as wg (μm), the groove depth is defined as dg (nm), the recess half-value width on the groove at a boundary of a reflecting layer of a recording layer formed on the substrate is defined as wd (μm) and the recess depth is defined as dd (nm), the optical recording medium having the recording layer 2 and the metal reflecting layer in this order, in which at least at organic dystuff is incorporated on the transparent substrate 1 having the groove, has a film formation structure on the groove simultaneously satisfying the following relationships: 0.69r<=p<=0.83r (1), 0.35<=wd/p<=0.55 (2), 0.75<=wd/wg<=1.0 (3), 0.50<=dd/dg<=0.70 (4).

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, and more particularly to a write-once optical recording medium capable of recording at a higher density than a CD capable of recording / reproducing with a red laser beam selected from the range of 620 nm to 670 nm. .

[0002]

2. Description of the Related Art A recordable optical recording medium in which a dye is used as a recording layer and a reflective layer is provided on the recording layer for the purpose of obtaining a reflectance,
For example, Optical Data Storage 1989 Technical Digest
Series Vol. 145 (1989), a medium using a cyanine dye or a phthalocyanine dye for the recording layer is supplied to the market as a CD-R medium. However, these are 650
For applications that have only the capacity of MB and record high-capacity information, such as digital moving images, with high quality, the capacity is completely insufficient.

Under these circumstances, in recent years, 620 nm to 670 nm
Has been developed, and a higher-density recording capacity has been made possible. An optical recording medium on which a high-quality moving image of about 2 hours is recorded in the same size (120 mm in diameter) as a CD is a DVD.
It has been developed as a read-only disc. This medium has a recording capacity of 4.7 GB / surface and is a read-only medium made by transferring pits to a substrate. Furthermore, in recent years, with the increase in the output of the red semiconductor laser, a write-once optical recording medium (hereinafter referred to as DVD-R) having the same format as the read-only DVD and having the same large capacity has been strongly developed. Is being sought. In such a background, there are expectations that the DVD-R is most suitable for DVD software authoring verification and that it will be used as a medium for storing even larger amounts of data in the future.

[0004] However, the recording laser beam spot diameter used in DVD-R is smaller than the laser beam spot diameter used in conventional CD-R, but the recording density of DVD-R is smaller than that of the recording beam. The recording density is much higher than the expected recording density. Therefore, in such a high-density recording medium, it is necessary to accurately form recording pits smaller than the beam spot diameter at the time of recording. However, as the recording density increases, problems such as thermal interference between pits and between tracks during recording, crosstalk, and the like cannot be ignored. Therefore, pit edges that are particularly important for signal detection fluctuate (hereinafter, jitter). ), And the error rate deteriorates. Accordingly, there is a strong demand for a high-density write-once medium capable of accurately recording and forming small and small pits with respect to a beam diameter that can avoid such a problem.

On the other hand, a write-once recording medium having a higher density than a CD having an organic dye as a recording film is disclosed in JP-A-6-33608.
No. 6, JP-A-7-262604 and the like, examples of the use of cyanine dyes are disclosed in JP-A-9-58123, JP-A-9-274732, and JP-A-9-32.
No. 3478 discloses an optical recording medium using an azo metal chelate compound dye. However, in the case of cyanine dyes, essential issues remain in terms of durability performance, and in the case of azo dyes, synthesis generally involves difficulties,
In many cases, the solubility is not always excellent, and there is a difficulty in film formation. For this reason, a high-quality recording film having easy workability and excellent durability is required.

Further, as for the medium structure for the purpose of favorably forming high-density recording pits smaller than the irradiation beam, only the substrate groove shape or the dye film thickness is described. There is no prior technical disclosure about the effect on the width and the groove width followability of the recording layer.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, that is, a recording layer containing an organic dye which absorbs laser light on a transparent substrate having a groove, and a light reflection layer. In a medium having at least a layer,
When pits smaller than the conventional recording beam diameter are formed using light having a wavelength selected from 20 nm to 670 nm, thermal interference and crosstalk between pits and between tracks are avoided, and good pit edge characteristics are obtained. (Jitter characteristics)
And to provide a high-density write-once optical recording medium having good reproduction compatibility with a DVD player.

[0008]

In order to solve the above-mentioned problems, the present inventors have developed a 4.7 GB DVD having a single-sided full capacity.
As a result of intensive studies aimed at obtaining a considerably good recording pit jitter, the expected laser wavelength: 620 to 670 n
In the range of m, the selective application of an organic dye material having good optical properties and thermal decomposition properties for recording, and the film formation shape of the recording layer capable of obtaining stable tracking gain while reducing crosstalk Was found by selecting an appropriate groove substrate and developing a film forming method on the substrate.

That is, a material containing one or more specific organic dyes, in particular, a dipyrromethene metal chelate compound, is selectively applied to the recording layer, and recording is performed by applying a simple coating film forming method to a specific substrate groove shape. It has been found that the ability of the layer to follow the substrate groove can be controlled and the shape of the interface with the reflective layer can be controlled. By controlling the shape of the recording layer, it was found that crosstalk to an adjacent track was suppressed, and a high-density recording pit edge smaller than the recording beam was satisfactorily formed.

That is, according to the present invention, an optical recording medium having at least a recording layer containing an organic dye and a metal reflective layer on a transparent substrate having a groove in this order has a recording beam diameter represented by λ / NA of r.
[Where λ is the recording wavelength (μm) and NA is the numerical aperture of the objective lens], the groove pitch of the substrate is p (μm),
The groove half width is wg (μm), and the groove depth dg (n
m), and when the half width of the dent on the groove at the interface of the reflective layer of the recording layer formed on the substrate is wd (μm) and the depth of the dent is dd (nm), 0.69r ≦ p ≦ 0.83r (1) 0.35 ≦ wd / p ≦ 0.55 (2) 0.75 ≦ wd / wg ≦ 1.0 (3) 0.50 ≦ dd / dg ≦ 0.70 (4) A write-once optical recording medium having a higher density than a groove-recordable CD characterized by a satisfactory film formation structure on a groove, wherein the dye contained in the recording layer is a dipyrromethene metal chelate represented by the following general formula (I): The optical recording medium as described above, comprising a compound,

[0011]

Embedded image (Wherein, R ^{1 to} R ⁹ each independently represent a hydrogen atom, a halogen atom, a nitro group, a cyano group, a substituted or unsubstituted amino group, a carbonyl group, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, C1 to C12 substituted or unsubstituted alkoxy group, C1 to C12 substituted or unsubstituted alkylthio group, C2 to C12 substituted or unsubstituted alkenyl group, C7 to C20 substituted or Represents an unsubstituted aralkyl group, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a substituted or unsubstituted arylthio group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroaryl group having 4 to 20 carbon atoms. , M represents a transition metal.)

The optical recording medium according to the above or the above, wherein the dye contained in the recording layer is a halogen-substituted dipyrromethene metal chelate compound, the substrate groove depth dg is 120 to 230 nm, and the groove half width wg is 0.28 μm to 0.42 μm. An optical recording medium according to any one of the above-mentioned, characterized in that it is selected from the range of: a recording layer on a transparent substrate, a reflective layer, an adhesive layer directly or via another layer, a direct or other layer Characterized by having a structure in which another substrate is bonded through
The optical recording medium according to any one of the above.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail.

The optical recording medium of the present invention is basically an optical recording medium having at least a recording layer and a reflective layer on a transparent substrate having a groove. For example, as shown in FIG. 2, a reflective layer 3 and a protective layer 4 are laminated in this order. Further, a structure in which a substrate is attached to the reflective layer 3 via a protective layer and / or an adhesive layer may be adopted. Another layer may be present between the substrate and the recording layer, between the recording layer and the reflective layer, between the reflective layer and the adhesive layer, and between the bonding substrate and the adhesive layer.

The material of the substrate may be basically any material as long as it is transparent to light having a wavelength of 620 to 670 nm assumed for recording and reproduction. For example, an organic polymer material such as an acrylic resin, a polyethylene resin, a polycarbonate resin, a polystyrene resin, a polyolefin resin, and an epoxy resin, and an inorganic material such as glass are used. Among them, injection molded substrates of acrylic resin, polycarbonate resin and polyolefin resin are preferable from the viewpoint of mechanical properties of the substrate, ease of molding of grooves, pre-pits, etc., and economical efficiency. A proven polycarbonate resin substrate is more preferable.

The shape of these transparent substrates may be plate-like or film-like, or may be circular or card-like. D
Considering VD compatibility, diameter 80mm or 120m
It is desirable that a center disk of about 15 mm be formed in the center of an m-type disc.

On the surface of these substrates, grooves and / or prepits on the order of submicrons are usually formed spirally or concentrically. The grooves and pre-pits existing on the surface of the substrate are preferably provided at the time of molding the substrate, but may also be provided by providing a thermosetting resin or an ultraviolet curable resin layer on the substrate.

Here, the design of the groove shape not only governs the servo stability as a tracking guide groove but also directly or indirectly affects the film formation shape of the recording layer formed thereon. This is very important because it has a great effect on the recording characteristics. In order to maintain stable tracking performance and obtain good recording performance described later, a groove pitch with respect to a beam diameter: r:
p is selected from the range of 0.69r to 0.83r.
Here, when p <0.69r, the crosstalk component is large and the tracking servo becomes unstable, and p> 0.83r
However, this is not desirable for the purpose of ensuring the desired high density.

Next, the selection of the groove half width: wg is very important because it is closely related to the film formation shape of the recording layer, which will be described later, in particular, the concave half width on the groove which is the follow-up width. According to our detailed study, wg / p
Good media performance could be derived in a system in which the ratio of... Was selected from the range of 0.4 to 0.6. That is, for example, when the track pitch is set to 0.74 μm in consideration of compatibility with DVD, it is preferable in terms of characteristics that the groove width is selected from the range of 0.28 to 0.44 μm in half width. Here, wg
When /p<0.40, the recording dye content sealed in the groove at the time of forming the recording layer is insufficient, so that there remains a problem in obtaining the recording sensitivity. Conversely, when wg / p> 0.6, the tracking error amplitude It became difficult to obtain media, and it was not practical to convert the media.

At this time, the optimum groove depth: dg
Is preferably selected from the range of 120 to 230 nm, and still more preferably from the range of 150 to 200 nm. Where dg> 230
With nm, it is difficult to transfer the groove to the substrate from the viewpoint of manufacturing, and when dg <120 nm, the recording layer becomes difficult to seal inside the substrate groove, and good properties cannot be maintained. Note that these groove shapes can be measured in detail using a scanning tunneling microscope (STM) or an atomic force microscope (AFM).

In the present invention, the recording layer is 620 of interest.
Recording pits that have moderate absorption in the laser wavelength range of nm to 670 nm, and have physical and chemical deformation, alteration, and decomposition by irradiation of laser light having a certain energy or higher with light-to-heat conversion Be well formed with threshold characteristics
In addition, it is important to have good optical film physical property values in order to secure a high reflectance and a high modulation degree that can be reproduced by a DVD player.

For this reason, the absorption maximum (λma
x) exists around 550 nm to 600 nm, and the refractive index: n is large (n> 1.
9) It is essential that the absorption (attenuation constant: k) is appropriate (k <0.40). Here, when n <1.9, the reflectivity is reduced and the modulation is not obtained, which causes a problem in compatibility with DVD players. When the attenuation constant k> 0.40, the absorption amount is too large, and the reflectivity is also too large. Is extremely lowered, and the damage due to the reproduction light becomes apparent. Further, from the viewpoint of thermal characteristics, it is essential for the formation of stable high-density recording pits that both the melting point and the decomposition point of the dye material be 200 ° C. or higher. Under these circumstances, specific dyes such as cyanine-based, azo-based, phthalocyanine-based, indigo-based, and porphyrin-based have been proposed. In the present invention, however, good optical properties, thermal properties, durability, and coating processing As a result of various investigations from the viewpoint of the easiness and the like, the recording layer containing the dipyrromethene-based metal chelate compound represented by the general formula (I) is excellent in balance, and particularly, the dependence on the groove width shape of the optical recording medium of the present invention. Can be taken out clearly.

In the general formula (I), the substituents represented by R ^{1 to} R ⁹ each independently represent a hydrogen atom, a halogen atom, a nitro group, a cyano group, a substituted or unsubstituted amino group, a carbonyl group, Substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, substituted or unsubstituted alkylthio group having 1 to 12 carbon atoms, substituted or unsubstituted having 2 to 12 carbon atoms A substituted alkenyl group, a substituted or unsubstituted aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms,
A substituted or unsubstituted arylthio group having 6 to 20 carbon atoms,
Examples thereof include a substituted or unsubstituted heteroaryl group having 4 to 20 carbon atoms.

Here, the halogen atom includes fluorine,
They are chlorine, bromine and iodine, preferably chlorine and bromine.

The substituted or unsubstituted alkyl group having 1 to 12 carbon atoms includes a linear, branched or cyclic alkyl group,
Or a halogen atom, an alkoxy group, a hydroxy group,
Examples include the above-mentioned alkyl groups substituted with a cyano group, an amino group, and the like.

Examples of the substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms are a linear, branched or cyclic alkoxy group or an alkoxy group having the same substituent as in the above-mentioned alkyl group. Preferably, a lower alkoxy group such as a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group and a sec-butoxy group is exemplified.

Examples of the alkylthio group having 1 to 12 carbon atoms are a linear, branched or cyclic alkylthio group or an alkylthio group having the same substituent as in the above-mentioned alkyl group.

Examples of the substituted or unsubstituted alkenyl group having 2 to 12 carbon atoms include an unsubstituted alkenyl group, an alkenyl group having the same substituent as the above-mentioned alkyl group, and an aryl group such as styryl. Is an alkenyl group having

Examples of the substituted or unsubstituted aryl group having 6 to 20 carbon atoms include an unsubstituted aryl group and an aryl group having the same substituent as the above-mentioned alkyl group. Is a phenyl group, an alkyl-substituted phenyl group, a nitrophenyl group, a cyanophenyl group,
And an aminophenyl group.

Examples of the substituted or unsubstituted arylthio group having 6 to 20 carbon atoms include an unsubstituted arylthio group, an arylthio group having a substituent similar to the above-mentioned alkyl group, and a C4 to C20 arylthio group. Examples of the substituted or unsubstituted heteroaryl group are an unsubstituted heteroaryl group, or a heteroaryl group having the same substituent as in the case of the above-mentioned alkyl group, preferably having a substituent And a thienyl group and a furyl group.

Coordinated metal: M is not particularly limited as long as it is a metal capable of forming a complex with a dipyrromethene compound, but from the viewpoints of stability and optical properties, Ni, Co,
Transition metals such as Cu, Pd and Zn are preferred. These dipyrromethene-based metal chelate compounds may be used alone or as a mixture of a plurality of compounds.

Further, it is desirable that the dipyrromethene metal chelate compound used herein is more preferably halogen-substituted. For example, in the general formula (I), the above R ¹
R ⁹ to R ⁹ are directly substituted with one or more halogen atoms, or as a substituent containing a halogen atom, for example, a linear, branched or cyclic halogenated alkyl group having 1 to 12 carbon atoms; Those substituted with one or more of the substituted aryl halide groups having 6 to 20 carbon atoms or the like are preferable. In particular, the introduction of a bromine atom or a bromine substituent is very effective in reducing the temperature difference between the melting point of the dye and the decomposition point of the dye.

In the recording layer, additives such as a resin, a leveling material, a quencher, a dye thermal decomposition accelerator, and an ultraviolet absorber can be mixed or introduced as a substituent, if necessary. Of course, the organic dye of the present invention may be used alone or in combination of two or more.

Regarding the shape of the film to be formed,
In order to control crosstalk to an adjacent track when performing higher-density recording, and to improve the pit edge as a result, the groove half width of the substrate: wg, and the formed recording layer surface portion, That is, it is extremely important to control the half width of the recess on the groove at the interface of the reflective layer: wd, and to control the follow-up shape of the recess depth: dd to the groove depth: dg used. This indicates that it is important that the interface shape between the recording layer and the reflective layer on the groove irradiated with laser, that is, the effective contact area, is in an appropriate range when thermally forming high-density recording pits. It is thought that it is.

The present inventors systematically change the groove width shape of the substrate to be used and the film forming conditions (in the case of a coating method, the rotation conditions, solvent conditions, environmental conditions (temperature, air volume, etc.)). As a result of the analysis of the correlation with the signal characteristics, the ratio of the half width of the recess on the groove: wd to the pitch of the groove: p: wd / p is in the range of 0.35 to 0.55, and the depth of the recess at that time : Dd: Ratio of groove depth: dg to dd
It has been found that it is preferable in terms of characteristics to form a recording layer in a range of / dg of 0.5 to 0.7. That is, film formation that satisfies 0.69r <p <0.83r and 0.35 <wd / p <0.55 and 0.75 <wd / wg <1.0 and 0.5 <dd / dg <0.7. Shape is important.

Here, when wd / p <0.35, the recording portion could not fit inside the narrow groove, and as a result, large crosstalk was detected, and the jitter component could not be ignored at the formed pit edge. When wd / p> 0.55, the tracking error amplitude was significantly reduced.

When dd / dg <0.5, the output gain of the tracking error signal becomes small, and dd / dg>
At 0.7, there was a limit in securing the reflectance.

The groove half width: wg, the groove depth: dg, the half width of the recess on the groove at the reflective layer interface of the formed recording layer: wd, and the recess depth: dd are schematically shown in FIG. The relationship shown in FIG.

With respect to the method for forming the dye film, coating methods such as spin coating and casting, spraying,
It is not particularly limited as long as it can be achieved by applying optimization conditions such as a sputtering method, a chemical vapor deposition method, and a vacuum deposition method. The film formation shape could be controlled mainly by optimizing the application rotation conditions, solvent conditions, application environment conditions (temperature, air volume, etc.). Here, in particular, for good high-density recording, the above-described setting of the film thickness on the groove substrate is important.
In order to obtain particularly good jitter performance, it is about 60 to 150 nm on the groove and 30 to 10 nm on the land.
About 0 nm was preferable. In particular, if the dye film thickness on the groove is too large, heat storage during recording becomes too large, so that thermal interference with peripheral pit portions cannot be ignored, and a large decrease in reflectance occurs. On the other hand, if the thickness is too small, heat radiation to the reflective layer is too large to obtain sufficient sensitivity, and further, a large degree of modulation is lowered, so that the S / N of the signal is deteriorated and the jitter is affected.
Further, the control of the land film thickness is also important especially for avoiding thermal interference (crosstalk, crosswrite) in the track direction. In controlling the thickness of the dye film in the groove and land portions and controlling the half width of the dent: wd on the groove, which is the shape of the coating film, it is important to select a coating solvent and a solution concentration (viscosity). In the rotation condition, it is particularly important to control an initial flow process in which the coating liquid is fixed in a groove shape while flowing on the substrate groove with evaporation. In that sense, the shape of the coating film can be controlled by controlling the rotation conditions and the rotation gradient immediately after the application of the liquid droplets. Further, the most effective control of the film thickness is to control the time of the high-speed rotation and the rising gradient to the high-speed rotation under the rotation condition.

Here, it is a matter of course that the solvent must be one that easily dissolves or disperses the dye and does not damage the substrate. However, in controlling the film thickness and wd, the solvent must have a low evaporation rate. The selection focused on is particularly important and effective. The coating solvent is 70 ° C.
150 ° C, preferably 90 ° C to 13 ° C.
More preferably, it is selected from the range of 0 ° C. Of course, it is also possible to apply a mixed solvent, control the evaporation rate by adjusting the dye dissolution concentration, and control the environmental temperature. Specific coating solvents include hydrocarbon solvents (hexane,
Cyclohexane, octane, toluene, xylene, etc.), halogenated hydrocarbon solvents (chloroform, carbon tetrachloride, dichlorodifluoroethane, etc.), ether solvents, cellosolve solvents, etc.
Attention is paid to the viscosity and the like, and one or a plurality of them are selected and used by mixing. In particular, in the case of applying a dipyrromethene metal chelate compound, selection from a hydrocarbon nonpolar solvent having 7 to 10 carbon atoms is very effective.

Also in the spray method, the shape following the groove can be controlled by controlling the shape of the droplet and the surface tension of the liquid when the film is deposited on the substrate.

The recording layer thus formed can be laminated into two layers with an intermediate layer interposed therebetween. The recording layer and the recording layer are used for the purpose of obtaining the enhancement effect of the reflection layer and for the purpose of improving the recording characteristics. An inorganic dielectric layer as an intermediate layer at the interface of the layers,
It is also possible to laminate a plurality of dye layers and the like.

Next, as a material of the reflection layer, one having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag,
Metals such as Cu, Ti, Cr, Ni, Pt, and Cr can be used alone or as an alloy. Among them, Au, Al, Ag, Cu and alloys thereof are most suitable because of their high reflectivity.

As a method for forming the reflective layer, for example, a sputtering method, a chemical vapor deposition method, a vacuum vapor deposition method, an plating method and the like can be mentioned, and the film is usually formed with a thickness of 30 to 200 nm. Preferably it is 50 to 150 nm. In some cases, an adhesive layer is provided between the recording layer and the reflective layer in order to enhance the adhesion of the reflective layer.

In the present invention, in order to protect the recording layer and the reflective layer, a protective layer may be further provided on the reflective layer by a known method, or two substrates may be bonded together.

The material of the protective layer is not particularly limited as long as it protects the recording layer and the reflective layer from external force. Examples of the organic substance include a thermoplastic resin, a thermosetting resin, and a UV curable resin. Among them, UV curable resins are preferred.

As a method for forming the protective layer, a coating method such as a spin coating method or a casting method is applied similarly to the recording layer.

The optical recording medium of the present invention can be used for printing a label or the like on the protective layer. Further, on the mirror side of the substrate, an ultraviolet curable resin or an inorganic thin film may be formed to protect the surface or prevent adhesion of dust and the like.

As a method of recording information on the optical recording medium of the present invention, for example, while rotating the optical recording medium at a constant linear velocity, the bottom of the guide groove is irradiated with laser light from the transparent substrate side to be on the guide groove. This is performed by forming pits for reproduction in the recording layer. The signal is the same EFM as DVD
It is preferable to record the + signal and quantify the pit edge fluctuation with respect to the channel bit clock at that time as jitter to evaluate the effect of the present invention.

[0050]

EXAMPLES The present invention will be described below in detail with reference to examples, but the embodiments of the present invention are not limited to these examples.

Example 1 A spiral groove having a thickness of 0.6 mm and a diameter of 120 mm (depth (d): 150 nm, half width (wg): 0.1 mm).
(37 μm, pitch (p): 0.74 μm) A brominated dipyrromethene Cu complex compound represented by the following formula (A): 20 g / l is dissolved in ethylcyclohexane on an injection-molded polycarbonate substrate having a pitch of 23 μC and 50% RH. Under atmosphere, rotate at 700 rpm for 2 seconds and 0.5 seconds for 120
It was raised to 0 rpm, where it was rotated for 4 seconds. Thereafter, the speed was increased to 3000 rpm with a gradient of 1 second and rotated for 5 seconds to form a recording layer consisting essentially of only the dye on the groove. At this time, the film thickness on the groove measured by the cross-sectional SEM was 125 nm, and the film thickness on the land was 55 nm.
When the follow-up width to the groove shape in the recording layer was measured by AFM, wd = 0.32 μm and dd = 80 nm (wd /
p = 0.43, wd / wg = 0.86, dd / dg =
0.53).

[0052]

Embedded image

Next, Au was sputtered on the recording layer using a Balzers sputtering apparatus (CDI-900) to form a reflective layer having a thickness of 80 nm. In addition, U
V-curable resin SD-17 (Dainippon Ink and Chemicals)
After spin coating, UV irradiation was performed to form a protective layer having a thickness of 3 μm. A UV-curable resin SD-301 (Dainippon Ink and Chemicals) was applied thereon, and the same 0.6 mm substrate as described above was overlaid on the adhesive, and rotated at high speed to remove excess adhesive. After that, an optical recording medium bonded by irradiation with UV light was produced.

This optical recording medium is placed on a turntable,
While rotating at a linear velocity of 3.7 m / s, wavelength = 639n
optical disk evaluation device (DDU-10) manufactured by Pulstec Industrial equipped with a laser of m and an optical head of NA = 0.60.
00) and an EFM + encoder manufactured by KENWOOD, while recording a EFM + modulated signal having a minimum pit length of 0.40 μm while performing pulse train correction while continuously changing the recording power, and then setting the laser output to 0 using the same device. The recording signal was read at 0.5 mW. In addition,
At the time of signal reproduction, an equalization process conforming to the DVD reproduction standard was performed. As a result, the jitter was 8.2% of the channel bit clock, and the crosstalk to the adjacent track was 0.60.

This medium is, for example, a DVD manufactured by Matsushita Electric Industrial Co., Ltd.
Good reproduction was possible with the player (DVD-A300).

Example 2 In Example 1, except that a mixed solution of 1,2-dimethylcyclohexane and xylene 3% was used as a coating solvent.
A medium was experimentally produced and evaluated under exactly the same film forming conditions as in Example 1.

As a result, when the film thickness on the groove was 130 nm, the groove half width at half maximum was wd = 0.30 μm and dd = 77 n.
m was achieved. Jitter and crosstalk could be evaluated as 8.1% and 0.58, respectively, and more favorable properties could be confirmed.

Example 3 The same dye as in Example 2 was formed on a substrate having a groove depth: dg = 180 nm and a groove half width: wg = 0.35 μm by the same method as in Example 2. The results are shown in Table 1.

Example 4 A medium was prepared and evaluated in the same manner as in Example 1 except that a brominated dipyrromethene Cu complex represented by the following formula (B) was used. Good results as shown in Table 1 were confirmed.

[0060]

Embedded image

Example 5 Using the brominated dipyrromethene Cu complex represented by the formula (B), the same as in Example 1 on a substrate having a groove pitch: p = 0.68 μm and a groove half width: wg = 0.37 μm. And a similar evaluation was performed. As a result, good jitter performance was confirmed as shown in Table 1.

Comparative Example 1 A medium was prepared in the same manner as in Example 1 except that the substrate used had a groove depth: dg = 149 nm and a groove half-value width: wg = 0.25 μm, and signal evaluation was performed.

At this time, wd = 0.20 μm (wd / p
= 0.27), dd = 78 nm (dd / dg = 0.5)
2) and analyzed by AFM. As a result, the crosstalk was greatly increased to 0.81, and the jitter value was as poor as 15.5%.

Comparative Example 2 A medium was prepared on a wide substrate having a groove depth: dg = 148 nm and a groove half-value width: wg = 0.55 μm in the same manner as in Example 1, and signal evaluation was performed.

At this time, wd = 0.45 μm and dd = 7
It was evaluated as 5 nm, but tracking was very difficult with the medium, and good reproduction evaluation was impossible.

Comparative Example 3 Using the substrate and the dye of Example 1, a coating film was formed in the same manner except that the coating temperature was 30 ° C., and the initial speed was 400 rpm for 3 seconds.

As a result, wd = 0.22 μm, dd = 6
A film shape of 5 nm could be formed (wd / p = 0.2
9, wd / wg = 0.59, dd / dg = 0.43),
The recording quality was extremely poor.

The results are all shown in Table 1.

[0069]

[Table 1]

As apparent from Table 1, in the examples of the present invention, extremely good jitter performance was confirmed.
In the comparative example, the deterioration of the jitter characteristic cannot be ignored.

[0071]

According to the optical recording medium having a recording layer containing at least an organic dye, particularly a dipyrromethene metal chelate compound, and a metal reflection layer on a transparent substrate having grooves in this order, a wavelength of 620 to 670 nm is selected. In the area, crosstalk can be reduced by forming a recording layer shape having a specific groove follow-up width on a substrate having a specific groove width, good recording jitter performance is obtained, and a recording medium having a higher density than a CD can be obtained. Is achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram according to an embodiment of an optical recording medium of the present invention.

FIG. 2 is a sectional view of a film formation shape according to an embodiment of the optical recording medium of the present invention.

[Explanation of symbols]

 1. Substrate 2. Recording layer 3. Reflective layer 4. Protective layer

Continued on the front page (72) Inventor Yuji Inatomi 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Chemical Co., Ltd. (72) Inventor Yoshiteru Taniguchi 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemical Co., Ltd. (72) Invention Person Denzawa Misawa 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside of Mitsui Chemicals Co., Ltd. (72) Inventor Masashi Koike 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Mitsui Chemicals Co., Ltd.F-term (reference) FA12 FA15 FA23 FB42 4C063 AA01 BB03 BB04 CC07 DD04 EE10 5D029 JA04 WB14 WB17 WC01 WC07 WD10 WD16

Claims (5)

[Claims] 1. In an optical recording medium having a recording layer containing at least an organic dye and a metal reflective layer in this order on a transparent substrate having a groove, a recording beam diameter represented by λ / NA is r [where, λ is the recording wavelength (μm), NA is the numerical aperture of the objective lens], and the groove pitch of the substrate is p
(Μm), wg (μm), groove depth dg (nm), and groove half-width on the groove at the interface of the reflective layer of the recording layer formed on the substrate.
(Μm) and dd (nm) as the recess depth, 0.69r ≦ p ≦ 0.83r (1) 0.35 ≦ wd / p ≦ 0.55 (2) 0.75 ≦ wd / wg ≤ 1.0 (3) 0.50 ≤ dd / dg ≤ 0.70 (4) A write-once type optical recording with a higher density than a CD capable of groove recording characterized by a film formation structure on a groove that simultaneously satisfies the following conditions: Medium. 2. The optical recording medium according to claim 1, wherein the dye contained in the recording layer contains a dipyrromethene metal chelate compound represented by the following general formula (I). Embedded image (Wherein, R ^{1 to} R ⁹ each independently represent a hydrogen atom, a halogen atom, a nitro group, a cyano group, a substituted or unsubstituted amino group, a carbonyl group, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, C1 to C12 substituted or unsubstituted alkoxy group, C1 to C12 substituted or unsubstituted alkylthio group, C2 to C12 substituted or unsubstituted alkenyl group, C7 to C20 substituted or Represents an unsubstituted aralkyl group, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a substituted or unsubstituted arylthio group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroaryl group having 4 to 20 carbon atoms. , M represents a transition metal.) 3. The dye contained in the recording layer is a halogen-substituted dipyrromethene metal chelate compound.
Or the optical recording medium according to 2. 4. The substrate groove depth dg is 120 to 230.
nm, groove half-value width wg is 0.28 μm to 0.42 μm
4. The distance is selected from the range of m.
The optical recording medium according to any one of the above. 5. A structure in which a recording layer, a reflective layer, an adhesive layer directly or through another layer is bonded to another substrate, and another substrate is bonded directly or through another layer on a transparent substrate. The optical recording medium according to any one of claims 1 to 4, wherein: