JPH10188341A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-capacity optical recording medium which is adequate for short wavelength recording and has high reflectivity. SOLUTION: This recording medium is constituted by laminating a recording layer contg. org. dyestuff which is substantially free from loss at a temp. lower than a main loss initiation temp., is of >=2%/ deg.C in the inclination of the loss in the main loss process and is of >=30% in total loss %, a metallic reflection layer and a protective layer in this order on a specific transparent substrate. In such a case, the recording layer satisfies the conditions of the following (1) or (2): (1) The magnitude of the peak of heat generation in a differential thermal analysis be >=-10 to <=10μV/mg and the peak width be below 20 deg.C. (2) The recording layer consisting of the org. dyestuff of >=10 to <=30μV/mg in the magnitude of the peak of the heat generation in the differential thermal analysis have the metallic reflection layer of >=0.20 to <=0.30/μΩcm in the inverse number of the specific electric resistance value near room temp., >=0.1 to <=0.2 in the refractive index at reproducing light ±5nm and >=3 to <=5 attenuation coefft. thereon.

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,
The present invention relates to an optical recording medium on which recording can be performed by laser light.

[0002]

2. Description of the Related Art In recent years, attention has been paid to shortening the oscillation wavelength of laser light for high-density recording.
There is a demand for an optical recording medium capable of recording and reproducing with a laser beam having a wavelength shorter than m. In such a situation, there are various recording media, and among them, the organic dye-based optical recording media has a feature that it is inexpensive and easy in process. As such a dye of an organic dye medium for short wavelength use, cyanine and the like have been proposed, and are disclosed in JP-A-6-336086, JP-A-7-161068, and JP-A-7-26.
2604, JP-A-7-125441 and JP-A-7-266705. In the recording unit, 78
Like the CD-R at 0 nm, it is considered that the optical constant and the film thickness are reduced by the thermal decomposition of the dye, and the deformation and the like are caused by the softening of the substrate.

[0003]

In the above-mentioned prior art, the recording modulation degree is obtained by only the decomposition of the dye or the deformation of the substrate at the time of recording. In such a case, a large bit extending to the adjacent inter-groove portion is formed, so that crosstalk becomes a problem. In order to solve this problem, the present inventors have disclosed in Japanese Patent Application No. 7-213501 or the like that the optically variable area of the recording portion is sufficiently reduced by adding a large amount of a steep and large dye as a main component or adding a dye. It was proposed to obtain a sufficiently large recording signal intensity with a sufficiently high recording modulation degree and a high reflectance, and to propose a dye skeleton satisfying such requirements. However, when the track pitch is narrowed and the groove width is narrowed to increase the capacity of about 5 gigabytes or more on one side, crosstalk may not be sufficiently reduced in some cases.

[0004]

Means for Solving the Problems The inventors of the present invention have formed a medium capable of forming a fine recording portion with small crosstalk and realizing a high degree of modulation and a high reflectance in order to realize high density recording. As a result of intensive studies, the present invention has been achieved. That is, the gist of the present invention is that, on a transparent substrate, at least, by thermogravimetric analysis, there is substantially no weight loss at a temperature lower than the main weight loss start temperature, and the slope of the weight loss at the main weight loss start temperature is 2% / An optical recording medium which records and reproduces at 500 nm or more and 700 nm or less, in which a recording layer containing an organic dye whose total weight loss is 30% or more, a metal reflective layer, and a protective layer at 30 ° C. or more, is 30% or more. Alternatively, the condition (2) must be satisfied.

(1) The peak of the exothermic peak in the differential thermal analysis is -10 μV / mg or more and 10 μV / mg or less, and the peak width is 20 ° C. or less. (2) Exothermic peak size is 10 μV in the suggestive thermal analysis
The reciprocal of the specific electrical resistance at around room temperature is 0. 0 / mg to 30 μV / mg on the recording layer made of an organic dye.
20 / μΩcm or more and 0.30 / μΩcm or less,
A metal reflective layer having a refractive index at the reproduction light wavelength ± 5 nm of 0.1 or more and 0.2 or less and an extinction coefficient of 3 or more and 5 or less.

[0006]

Embodiments of the present invention will be described below. The recording layer in the present invention, the thickness is reduced by increasing the temperature by absorbing the recording laser light, the film thickness is reduced,
The phase of the return light changes due to the change in the optical characteristics,
The portion where the reflectance changes is used as a recording portion.

In the present invention, as the transparent substrate, a resin such as polycarbonate, polymethacrylate, amorphous polyolefin or the like, glass or the like is used, and a guide groove for servo is used. have.
The groove has a depth of usually 100 nm or more and 200 nm or less, preferably 140 nm or more and 180 nm or less.
The groove width is usually 0.2 μm or more and 0.4 μm or less, the track pitch is usually 0.7 μm or more and 1 μm or less,
The groove shape is preferably a U-shaped groove. When the depth of the groove is less than 100 nm, a sufficient change does not occur during recording, and a sufficient recording modulation degree may not be obtained. If the thickness exceeds 200 nm, the reflectance difference between the groove and the groove is too large, and in the case of recording on the groove, the reflectance is too low, which is not good. If the groove width is less than 0.2 μm, it may be difficult to obtain a sufficient tracking error signal amplitude, and the groove transfer rate of the substrate may be low, which is not preferable. Also, 0.4μ
If the groove width exceeds m, it is not preferable because the recording portion tends to spread laterally when recording is performed. Further, the narrower the groove width is, the more advantageous it is to obtain a higher recording modulation degree. But,
As described above, the crosstalk tends to increase.
The present invention is particularly effective when recording on a groove having a narrow groove width of 0.2 to 0.3 μm. The track pitch is preferably 0.7 μm or more and 1 μm or less for high capacity applications. In addition, when the groove shape has a pitch of 1 μm or more,
It is determined by optical measurement using a He-Cd laser, and when the track pitch is narrower than that, the profile is measured by STM or AFM. In this case,
Determined by STM and AFM.

The recording layer is usually obtained by spin-coating a solution of an organic dye or the like in a solvent such as ethanol, 3-hydroxy-3-methyl-2-butanone, diacetone alcohol or fluorinated alcohol. Examples of the solvent include a fluorinated alcohol having a boiling point of 100 ° C. or higher and 150 ° C. and having 3 or more carbon atoms, that is, 1H, 1
H, 3H-tetrafluoropropanol, 1H, 1H,
5H-octafluoropentanol, 1H, 1H, 3H
-Hexafluorobutanol and the like are preferably used.
When the boiling point is less than 100 ° C., the solvent evaporates quickly during spin coating, so that the coating liquid does not spread to the outer peripheral side from the radius of 40 mm of the disk, the thickness distribution in the radial direction becomes extremely large, and good characteristics are obtained. It is not preferable because it may not be obtained. When the boiling point exceeds 150 ° C.,
It takes time to evaporate, and the solvent tends to remain in the film,
Such a case is not preferable because good recording jitter is often not obtained. The film thickness at the inter-groove portion is preferably about 50 nm or more and 100 nm or less, and is preferably 90 nm or more and 180 nm or less at the groove portion. When the thickness of the recording layer in the inter-groove portion and the groove portion is smaller than this range, there is a possibility that a sufficient recording modulation degree cannot be obtained because the film thickness is too small. On the other hand, if the thickness exceeds this range, the film thickness is too large and the recording portion tends to spread in the track direction and the land direction, which may increase jitter and crosstalk. Actually, it is difficult to accurately know the thickness of the groove portion and the thickness of the inter-groove portion. In general, the film thickness of the inter-groove portion is often used instead (for example, see Japanese Patent Laid-Open No. 4-109).
No. 441, Japanese Patent Application Laid-Open No. 4-182944), the ratio of the film thickness of the groove to the film thickness of the inter-groove portion depends on the coating solvent, spin coating speed, wind speed, temperature, solution concentration, solution viscosity, etc. Since it varies depending on conditions, groove depth, groove width, and the like, it is difficult to know the average film thickness of the groove and the groove, or the groove film thickness only from the film thickness of the groove and the groove depth of the coating film. . On the other hand, if the ratio of the groove depth of the coating film to the groove depth of the substrate, the film thickness of the inter-groove portion, and the groove depth of the substrate are known, the film thickness of the groove portion can be obtained. The groove depth of this coating film is 50% or more of the groove depth of the substrate,
It is preferably 80% or less. When the thickness is less than this range, the reflectance is low because the groove portion is too thick, and there is a possibility that a tracking error signal cannot be sufficiently obtained. On the other hand, if it exceeds 80%, the groove thickness may be too thin and a sufficient recording modulation degree may not be obtained. Note that the ratio between the groove depth of the substrate and the groove depth of the coating film can be obtained from the depth obtained by measuring each under the same measurement conditions using AFM (or STM). Further, the film thickness of the groove portion can be obtained by forming a film on the mirror surface substrate and measuring the coating start portion with a three-dimensional surface roughness meter after forming the reflective layer. As shown in FIG. 1, the range of the film thickness (groove portion) in the present invention covers the first peak region of the reflectance.
FIG. 1 shows n _abs · d / λ (d is the film thickness of the recording layer) of Japanese _Patent Publication No. Conventionally, the range of the groove thickness of the recording layer is a range corresponding to the “film thickness” typified by the thickness of the inter-groove portion in the CD-R, and the present invention is a range that is one mountain shallower than the CD-R. Which is greater than 500 nm and 70
Although it is 0 nm or less, it is a preferable condition to be satisfied by the high-reflectance, high-capacity recording medium for recording and reproduction. In addition, FIG.
(B) and (c) show that the refractive index n at a wavelength of 640 nm is 2.
4, the extinction coefficient k is 0.05 and n = 2.3, k = 0.05,
Wavelength 640 nm for the case of n = 2.6 and k = 0.08
Reflectance (n = 0.166, k
= 3.15, film thickness 100 nm). FIG. 2 shows n _abs · d / λ at which the reflectance is 60% or more.
(d is the thickness of the recording layer) and the extinction coefficient k. Since these reflectivities do not include the shape of the groove, the reflectivity on the actual groove can be regarded as about 80% of this value. In addition, the monolayer film of the dye satisfying such optical characteristics has an absorption maximum or a shoulder of absorption on the short wavelength side closest to the reproduction wavelength, on the 40 nm to 60 nm shorter wavelength side than the reproduction wavelength.

Organic dyes used for optical recording include:
Phthalocyanine dyes, cyanine dyes, metal-containing azo dyes, dibenzofuranone-based, metal-containing indoanilines, and the like have been proposed, but the thermal characteristics of the organic dyes constituting the recording layer greatly affect the recording characteristics. In order to obtain sufficient properties for short wavelength applications, it is necessary that the weight loss in the main weight loss process in thermogravimetric analysis be sharp with temperature. This is because the organic dye film is decomposed by the reaction in the main weight loss process, causing a decrease in the film thickness and a change in the optical constant.
As a result, a bit (recording portion) in an optical sense is formed. At this time, the dye has a refractive index of 2.2 or more and 2.8 or less at a reproduction light wavelength, preferably 2.4 or more and 2.8 or less, and an extinction coefficient k of 0.03 or more and 0.09 or less. Preferably,
A value in the range of 0.03 or more and 0.06 or less is preferable because the reflectance of the disc is large and a large reflectance contrast before and after recording can be obtained. In many cases, the substrate below the recording bit is deformed by the temperature rise due to heat absorption of the dye layer during recording, and the groove width is widened as shown in FIG. In the present invention, the magnitude of the deformation (the groove width of the recorded portion) is 1.0 to 1.5 of the groove width of the unrecorded portion, that is, W ₁ / W ₀ = 1 or more,
1.5 or less. If it exceeds 1.5, it is not preferable to reduce the track pitch to 0.8 μm or less, because crosstalk increases and jitter is deteriorated. Also,
Since the dye layer, which is the recording layer, absorbs light to form a bit, if the main weight loss is slow with respect to temperature, that is, if weight loss occurs over a wide temperature range, optical change of the recording layer and The change in the film thickness is formed over a wide area. In the case of high-density bit length recording, bits overlap with each other, resulting in poor jitter and bit resolution, which is extremely disadvantageous. Therefore, there is a need for a dye that causes a sharp decrease in weight with respect to temperature. In the present invention, for the same reason, when a dye whose weight loss process is performed in two stages is used, that is, when a dye whose weight is reduced in a temperature region lower than the main weight loss start temperature is used. It is. In the present invention, the slope of weight loss in the main weight loss process is 2% / ° C or more, and the total weight loss% in the process is 30% or more, preferably, the slope of weight loss is 10% / ° C or more,
The total weight loss% is 35% or more. If the slope of the weight loss is less than the above range, a thin recording portion which is not sufficiently small and does not spread in the land direction cannot be formed, jitter and bit resolution deteriorate, and it is difficult to perform short bit length recording corresponding to high density. On the other hand, if the total weight loss is less than 30%, sufficient reflectance contrast before and after recording cannot be obtained, and sufficient short bit characteristics cannot be obtained because the recording modulation degree is small. Further, in order to obtain a recording medium with sufficiently small crosstalk at a narrow track pitch, the magnitude of the heat generation peak in the main weight loss process of the dye is in the range of −10 μV / mg to 10 μV / mg, preferably −5 μV / mg. More than 5 μV / mg.
If it exceeds this range, the crosstalk when the groove width is reduced to 0.3 μm or less exceeds 50%, and good jitter characteristics cannot be obtained. If it is less than this range, the heat absorption becomes too large, and the recording sensitivity deteriorates. Further, the peak width of the heat generation and heat absorption is preferably 20 ° C. or less. Exceeding this range makes it difficult to form good recording marks with sharp edges. The temperature at which the dye starts to lose weight is from 150 ° C. to 340 ° C., preferably from 150 ° C. to 200 ° C.

In the present invention, the slope of the weight loss is obtained as follows. (See FIG. 3.) The organic dye of mass M ₀ is heated at 10 ° C./min in nitrogen. As the temperature rises, the mass initially decreases by a small amount, and draws a substantially linear ab weight loss line,
Then, the weight starts to decrease rapidly, and the weight loss of 15% or more is reduced substantially along the straight line d ₁ -d ₂ . This is the main reduction process, the main weight reduction initiation temperature is that of the T _1. After that, the weight loss process is substantially indicated by a straight line cc. Straight line d ₁
If the temperature at the intersection of −d ₂ and the line cc is T ₂ , the weight is m ₂ , and the initial weight is m ₁ , the slope of the weight loss here is:

[0011]

## EQU1 ## A value represented by (m ₁ −m ₂ ) (%) / (T ₂ −T ₁ ) (° C.), and the weight loss% based on the total weight (total weight loss%)
Is

[0012]

## EQU2 ## This is a value represented by (m ₁ −m ₂ ) (%). In the case shown in FIG. 4, the slope of the weight loss in the main weight loss process is

[0013]

(M ₁ −m ₂ ) (%) / (T ₂ −T ₁ ) (° C.), and the weight loss% (total weight loss%) based on the total weight is

[0014]

## EQU4 ## (m ₁ −m ₃ ) (%)

Further, the calorific value in the present invention is obtained as follows. A differential heat curve (DTA curve) as shown in FIG. 5 is obtained together with the weight loss curve. The sample reference is an aluminum container containing no sample, and is heated at a rate of 10 ° C./min in nitrogen at a flow rate of 200 mL / min. Here, the aluminum container used in this measurement is a container having a diameter of 5 mmφ and a height of 2.5 mm, and the sample is put in the container in a powder state. The sample volume should not exceed 80% of the height of the aluminum container. The data sampling interval was 1 second.

As shown in the figure, in the vicinity of the time corresponding to the steep decrease in the TG curve, the DTA generates heat or an endothermic peak. The peak value of heat generation (endotherm) is C in the figure.
H, and in this case, a platinum-rhodium thermocouple (platinum:
The electromotive voltage difference of rhodium (87:13) was indicated as a temperature difference, and a value obtained by dividing the peak value by the weight of the measurement sample was obtained. In addition, when the peak was divided into two, the larger value was taken. The peak width was calculated by multiplying the time difference (minutes) between B 'and D' in the figure by 10 ° C at the heating rate, and "peak width (° C)".
I asked. As a dye satisfying the above conditions,

[0017]

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(Wherein R ¹ represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms, and R ² and R ³ represent 1 to 6 carbon atoms) Represents a straight-chain or branched alkyl group, or a methoxyethyl group or an ethoxyethyl group, Y ¹ represents a hydroxyl group or a carboxyl group, and Y ² is substituted by a straight-chain or branched halogen atom having 1 to 6 carbon atoms. An optionally substituted alkyl group, X and Z
Represents an electron withdrawing group such as a cyano group or a carboxylic acid derivative group. M ²⁺ represents a divalent ion such as nickel, cobalt, and copper. Is particularly preferred. For example,

[0019]

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[0020]

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[0021]

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[0022]

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And the like. However, organic dyes are not limited to dyes having a calorific value of 10 μV / mg or less and exhibiting good characteristics as a recording layer. Therefore, in the case of an organic dye having a calorific value of more than 10 μV / mg and not more than 30 μV / mg, the metal reflective layer on the dye layer has a reciprocal of specific electric resistance near room temperature of 0.20 / μΩcm. that's all,
The “heat quenching effect at the time of recording on the recording layer” obtained by setting the density to 0.30 / μΩcm or less is used.
That is, as indicated by the Wiedemann-Franz law, there is a proportional relationship between the electrical conductivity and the thermal conductivity, so that the magnitude of the thermal conductivity of the thin film can be estimated from the electrical conductivity. In this case, the surface resistance R of a sputtered metal film of about 100 nm on a slide glass was measured by the four-terminal method, and the reciprocal of the specific electric resistance (electric conductivity) = (π / ln2)
Rt (where t is the film thickness) determined the reciprocal of the specific electrical resistance, that is, the electrical conductivity. In the present case, the thermal conductivity is larger than that of gold, because the reciprocal of the specific electric resistance value is 0.20 / μΩcm or more and 0.30 / μΩ.
cm or less. Further, since it is necessary that the reflectivity of the disk is sufficiently high as the metal reflection layer, the refractive index and the extinction coefficient at the reproduction light wavelength ± 5 nm are each 0.1%.
Not less than 0.2, not less than 3, not less than 5, and not more than 5. Specifically, silver and its alloys are mentioned. With this combination, it is possible to suppress the recording bit from spreading in the direction of the adjacent track due to the rapid cooling phenomenon, and as a result, it is possible to reduce the crosstalk. In this case, the reciprocals of the specific electric resistance values were 0.15 / μΩcm and 0.27 / μΩcm for gold and silver, respectively.

The metal reflection layer is a metal film that efficiently reflects the laser beam transmitted through the recording layer, and has a thickness of 500 nm or more.
Since the reflectance does not decrease at 700 nm or less, the refractive index of light in the wavelength region of recording / reproducing wavelength ± 5 nm is 0.1 or more,
Preferably, the extinction coefficient k is 3 or more and 5 or less. As a preferable metal reflection film, a metal reflection film containing silver as a main component is particularly preferable. This is because silver, which is a metal having a particularly high thermal conductivity, has the effect of rapidly cooling the temperature rise during recording of the recording layer, thereby suppressing the substrate from being greatly deformed in the inter-groove portion. Talk becomes smaller. Further, silver has a higher reflectivity than gold, an aluminum alloy, or the like, so that a larger signal amplitude can be obtained when short-bit recording is performed. When this is used as a reflective layer, short-bit characteristics are improved. In order to improve weatherability and fine-tune the thermal conductivity, silver, Ti, Rh, Cu, T
a, Pd, Ni, V, Co, Cr, Si, C, B, S
It is preferable to add additional elements of n, P, Zn, Sb, and Mo in a range of 3 atomic% or less. . The thickness of the metal reflection layer is
Preferably, the film thickness is 80 nm or more, which does not excessively suppress the deformation of the recording layer and does not excessively deteriorate the recording sensitivity.

In the optical recording medium of the present invention, a protective layer is laminated on the reflective layer, which has the effect of preventing the formation of holes in the metal reflective layer of the recording portion and suppressing the asymmetry of deformation. I have. An ultraviolet curing connection is preferred as the protective layer. Further, the thickness is usually set to 1 μm or more, preferably 3 μm or more so that the suppression of curing by oxygen or the like does not occur. Further, a hot-melt or ultraviolet-curing adhesive may be provided thereon to 10 to 20 μm, and the two sheets may be bonded to each other. Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples unless it exceeds the gist.

[0026]

【Example】

Example 1 Groove depth 150 nm, groove width (half width of groove) 0.25 μm
(0.80 μm pitch) (above, measurement results with AFM)
On a 0.6 mm thick polycarbonate substrate having a U-shaped guide groove of the following structural formula [IV]

[0027]

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0.06 g of the metal-containing azo dye represented by the formula is dissolved in 5 g of octafluoropentanol (OFP),
This was spin-coated at 00 rpm and annealed in an oven at 80 ° C. for 1 hour to form a recording layer. The weight loss characteristics of this dye are of the type shown in FIG. 2, the weight loss during the main weight loss process is 47.0%, the temperature difference is 7.1 ° C., and the slope of the weight loss is 6.
6% / ° C (primary weight loss starting temperature is 313 ° C), total weight loss is 5%
9.7%, the exothermic peak value was +3.4 μV / mg, and the peak width was 14.7 ° C. The thermogravimetric analysis and the differential thermal analysis are performed using a differential thermal balance (“SSC5200H”) manufactured by Seiko Instruments Inc.
Series "TG-DTA-320"). The refractive index n and the extinction coefficient k at 640 nm of this dye monolayer are 2.2 and 0.06, respectively, and the absorption shoulder is 577.
nm.

Gold was sputtered on this recording layer to a thickness of 100 nm, and the groove depth of the coating film measured by AFM in this state was 55% of the groove depth of the substrate. In addition,
The inter-groove film thickness of the recording layer was 80 nm (accordingly, the groove film thickness was 140 nm). A UV curable resin (“SD-318” manufactured by Dainippon Ink) was spin-coated on the metal layer at about 3 μm and cured with an ultraviolet lamp to produce a disk. The disks produced in the same manner were bonded together by a hot melt method. This bonded disk is 640n
m semiconductor laser evaluation machine (numerical aperture NA = 0.6)
When a quadruple-speed EFM signal (n-1) T of a CD-R was recorded at a linear velocity of 2.7 m / s, a good eye pattern was obtained at 7.4 mW with the center of the eye located at the center of the 11T waveform. Was. Itop = 50% In this recording conditions, I ₁₁ / I _top =
At 68%, the 3T jitter was 9 ns. When the signal was reproduced in the groove (land) adjacent to the groove recorded under this condition, the signal amplitude was 38% of the reproduction amplitude in the groove.
Deterioration of jitter due to recording of tracks on both sides showed a sufficiently small crosstalk characteristic of 1 ns. Peel the bonded surface of this disk, peel off the reflective film with double-sided tape,
When the dye was washed away with ethanol and the deformation of the substrate under the recording portion was observed by AFM, a protrusion of about 20 nm was formed, and the deformation of the groove width was 1.1 times the groove width of the unrecorded portion. A mark was formed.

Examples 2 to 5 and Comparative Examples 1 to 3 Substrates and UV curable resin layers used in the following Examples and Comparative Examples are all the same as those in Example 1. 100 nm of gold (Example 5 is 100 nm of silver
m), the dye was changed to that of the following structural formula, and the recording conditions were exactly the same in all examples. The characteristics are as shown in Table 1. In the table, "crosstalk" indicates the value of the reproduction signal amplitude at the inter-groove portion / the reproduction signal amplitude on the groove (%) when recording on the grooves on both sides. It is. In any case, the film thickness of the inter-groove portion is 80 nm to 90 nm, the groove depth of the coating film is 55% to 60% of that of the substrate, and eventually the film thickness of the groove portion is 130 nm to 90 nm.
140 nm. In each case, recording was performed with a recording power capable of obtaining an eye pattern in which the center of the eye was located at the center of the 11T waveform. The amount of the sample used for measuring the calorific value by DTA is shown in the upper part of the chart in each of FIGS.

[0031]

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[0032]

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[0033]

[Table 1]

The recording power was 7.4, 6.6, 8.6, 6.4, 6.5, and 6.5 mW in Examples 1 to 6, respectively.
And 7.2, 7.0, and 7. in Comparative Examples 1 to 3, respectively.
It was 2 mW. Comparative Example 4 A disk was prepared in the same manner as in Example 6, except that the groove width of the substrate was changed to 0.35 μm. Was the disc is recorded in the same manner as in Example 6, I ₁₁ / I _top is obtained only 54% was much smaller than in Example 6. This indicates that the smaller the groove width, the higher the recording modulation degree can be obtained.

[0035]

According to the present invention, it is possible to obtain a high-capacity optical recording medium having a high reflectivity, which is suitable for short-wavelength recording, has a small crosstalk even if the track pitch and the groove width are sufficiently small, and is suitable for short-wavelength recording.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a calculation result showing a range of n _abs · d / λ and a reflectance in the present case.

FIG. 2 n _abs · d / in the present case that the reflectance is 60% or more
Explanatory drawing which shows the range of (lambda) and the extinction coefficient k.

FIG. 3 is an explanatory diagram showing groove widths of a substrate in a recorded portion and an unrecorded portion.

FIG. 4 shows the main weight loss process of the organic dye, the total weight loss of the main weight loss process,
FIG. 5 is an explanatory diagram of a chart of a differential thermal balance for explaining a method of obtaining a slope of weight loss.

FIG. 5 is an explanatory diagram of a chart of a suggestive thermobalance for explaining a main weight loss process of an organic dye, a total weight loss in the main weight loss process, and a method of obtaining a slope of the weight loss, which are different from FIG.

FIG. 6 is an explanatory diagram of a chart of a differential thermal balance for explaining a method of obtaining a heat generation (endothermic) peak value and a peak width in differential thermal analysis.

FIG. 7 is a chart of a differential thermal balance of the dye of Example 1.

FIG. 8 is a chart of a differential thermal balance of the dye of Example 2.

FIG. 9 is a chart of a differential thermal balance of a dye of Example 3.

FIG. 10 is a chart of a differential thermal balance of a dye of Example 4.

FIG. 11 is a chart of a differential thermal balance of a dye of Example 5.

FIG. 12 is a chart of a differential thermal balance of the dyes of Example 6 and Comparative Example 4.

FIG. 13 is a chart of a differential thermal balance of the dye of Comparative Example 1.

FIG. 14 is a chart of a differential thermal balance of the dye of Comparative Example 2.

FIG. 15 is a chart of a differential thermal balance of a dye of Comparative Example 3.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kurose 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsubishi Chemical Research Laboratory (72) Inventor Shuichi Maeda 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa Mitsubishi Chemical Research Institute Yokohama Research Laboratory

Claims (8)

[Claims] 1. A track pitch of 0.7 μm or more and 1.0 μm or more.
m, the depth is 100 nm or more and 200 nm or less, and the width (the groove width where the groove depth is halved) is 0.2 to
On a transparent substrate on which a recording / reproducing light guide groove of 0.4 μm is formed, at least thermal analysis shows that there is substantially no weight loss at a temperature lower than the main weight loss start temperature, and weight loss in the main weight loss process. Is more than 2% / ℃, and the total weight loss is 3%
In an optical recording medium in which a recording layer containing an organic dye of 0% or more, a metal reflective layer, and a protective layer are laminated in this order, the recording layer satisfies the following condition (1) or (2): An optical recording medium for recording and reproducing at a wavelength of 500 nm or more and 700 nm or less. (1) Exothermic peak size in differential thermal analysis is -10μ
V / mg or more and 10 μV / mg or less and peak width of 20 ° C. or less. (2) The magnitude of the exothermic peak in the differential thermal analysis is 10 μV /
The reciprocal of the specific electrical resistance near room temperature is 0.2 g on the recording layer made of an organic dye having a concentration of 30 μV / mg or less
0 / μΩcm or more and 0.30 / μΩcm or less, and the refractive index at ± 5 nm of reproduction light is 0.1 or more and 0.2 or less,
A metal reflection layer having an extinction coefficient of 3 or more and 5 or less. 2. The recording is performed on a groove, and the groove width (W ₁ ) of the substrate below the recording portion is at least one time greater than the groove width (W ₀ ) of the unrecorded portion.
2. The optical recording medium according to claim 1, wherein the ratio is 1.5 times or less. 3. The single-layered recording layer has a refractive index n of 2.2 to 2.8 at a reproduction light wavelength of ± 5 nm and an extinction coefficient of 0.0.
The optical recording medium according to claim 1, wherein the number is 3 or more and 0.09 or less. 4. A recording layer having a thickness of 50 nm or more above a groove of a recording layer.
4. The light according to claim 1, wherein the groove depth of the recording layer coating film is 50% or more and 80% or less of the groove depth of the transparent substrate. 5. recoding media. 5. The optical recording medium according to claim 1, wherein the dye constituting the recording layer is a compound represented by any one of the following structural formulas [I] to [III]. Embedded image (In the formula, R ¹ represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms, and R ² and R ³ represent a straight-chain alkyl group having 1 to 6 carbon atoms. A chain or branched alkyl group, or a methoxyethyl group or an ethoxyethyl group, Y ¹ represents a hydroxyl group or a carboxyl group, and Y ² is substituted with a linear or branched halogen atom having 1 to 6 carbon atoms. X and Z represent a cyano group, a carboxylate group, or a C1-6 group;
Represents a linear or branched alkyl group. M ²⁺ represents a divalent ion of nickel, cobalt, or copper. ) 6. The method according to claim 1, wherein the metal reflection layer is made of Ti, Rh, Cu, Ta,
Pd, Ni, V, Co, Cr, Si, C, B, Su,
The additive element selected from the group consisting of P, Zn, and Mo
6. Silver according to claim 1, wherein the silver is 3 atomic%.
The optical recording medium according to item 1. 7. The substrate has a thickness of 0.6 mm ± 0.03 mm, a track pitch of a guide groove of the substrate is 0.7 μm or more and 1.0 μm or less, a groove depth of 100 nm or more,
The optical recording medium according to any one of claims 1 to 6, wherein the groove width (groove width at which the groove depth is halved) is 0.2 µm or more and 0.3 µm or less at 200 nm or less. 8. The optical recording medium according to claim 1, wherein said protective layer mainly comprises an ultraviolet curable resin.