JPH10228672A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium capable of having an enough modulation degree under an enough small state of thermal nonuniformity and writing to be suitable for high speed recording and high speed reading by suppressing deterioration of jitters caused by the thermal nonuniformity generated at the time of high speed recording and unbalanced pit lengths and also making a light absorbing layer enough thin in thickness. SOLUTION: This optical information recording medium is for recording information by irradiating the light absorbing layer 3 with recording light L1, and an average film thickness Dav of the light absorbing layer 3 is 40 nm<=Dav<=100nm, and then when an EFM signal is recorded under optimum power, a dyestuff survival rate E in the light absorbing layer 3 is 0.6<=E<=0.9. Thus, since the average film thickness and the dyestuff survival rate of the light absorbing layer are regulated to fall within the specified ranges, the optical information recording medium having a satisfactorily good characteristic against jitters and an enough modulation degree even in the case of high speed recording is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical information recording medium, and more particularly to a writable optical information recording medium having at least a light absorbing layer and a light reflecting layer on a light transmitting substrate.

[0002]

2. Description of the Related Art As a conventional writable optical information recording medium, for example, as disclosed in Japanese Patent Publication No. 7-105065, an organic dye or the like is formed on a light-transmitting substrate having a pregroove formed in a spiral shape. Light absorption layer,
It is based on a structure in which a light reflection layer made of a metal film or the like is further provided on this light absorption layer. By irradiating this optical information recording medium with recording light such as laser light from the substrate side, the light absorbing layer absorbs energy,
Information is recorded by forming recording pits by heat generation and decomposition of the dye in the light absorbing layer, thermal deformation of the substrate, and the like.

Such a writable optical information recording medium is generally known as "CD-R".
-R is particularly compatible with discs such as a read-only CD (compact disc) and a CD-ROM, and has a feature that recording can be performed only once and this recording cannot be erased. It is common and widely used in the information processing field.

[0004] However, with the increase in information data and the complexity and sophistication of information processing, the recording speed and reading speed of optical information recording media have been increasing in recent years. 1996 in the market
By the end of the year, normal 6 × speed recorders and 15 × speed CD-ROM drives for reading were generally available on the market.

In the case of high-speed recording, for example, if the recording speed is 6 times, the linear velocity is increased to 6 times, and a high-power laser beam is output for about 1/6 of the time corresponding to each basic pit length T of the EFM signal. , Resulting in a pit length of 3T or more within a specified range.
The purpose is to obtain an optical information recording medium on which a signal up to 11T is recorded.

Therefore, in controlling the length of the recording pit of each T in the recording machine, there is a problem that accuracy higher than that of the conventional constant speed recording is required. Also, for a medium to be recorded, it is necessary to form each pit of a predetermined length in only a fraction of the conventional time,
There is a problem that the influence of heat generation and thermal interference during recording becomes significantly larger than in the past.

Therefore, there is a problem that jitter is deteriorated due to the thermal non-uniformity generated at the time of high-speed recording, and the pit length becomes uneven.

The deterioration of characteristics at the time of high-speed recording is considered to be caused by the above-mentioned thermal non-uniformity, which is closely related to the thickness (film thickness) of the light absorbing layer. That is, if the thickness of the light absorbing layer is reduced, the influence of heat generation and thermal interference can be reduced. However, CD-R is, in principle,
Since the pit contrast is obtained by diffraction of light generated from the optical phase difference between the pit portion and the non-pit portion, there is a problem that if the thickness of the light absorbing layer is small, it is difficult to obtain sufficient pit brightness, that is, sufficient modulation. There is.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a writable optical information recording medium suitable for high-speed recording.

Another object of the present invention is to provide an optical information recording medium in which the deterioration of jitter due to the thermal non-uniformity occurring at the time of high-speed recording and the deviation of the pit length are suppressed.

Another object of the present invention is to provide an optical information recording medium having a sufficiently small degree of thermal non-uniformity and a sufficient degree of modulation by sufficiently reducing the thickness of the light absorbing layer. As an issue.

[0012]

That is, the present invention focuses on limiting the average thickness Dav of the light absorbing layer and the residual ratio E of the dye in the light absorbing layer to predetermined ranges. A substrate having a pre-groove and having a light-absorbing layer containing a light-absorbing substance composed of a dye that absorbs recording light by laser light, provided on the substrate,
An optical information recording medium, provided on the light absorbing layer, for recording information by irradiating the light absorbing layer with the recording light, the light information recording medium comprising: The average thickness Dav of the absorption layer is 40 nm ≦ Da
v ≦ 100 nm and E at optimal power
An optical information recording medium, characterized in that the dye remaining ratio E in the light absorbing layer satisfies 0.6 ≦ E ≦ 0.9 when FM signal recording is performed.

[0013] The thickness Dg of the light absorbing layer on the pre-groove may be 60 nm ≦ Dg ≦ 140 nm.

The light absorbing layer may contain a single or plural kinds of carbocyanine dyes, and may contain at least 80 wt% of a substance which absorbs the recording light and decomposes by heat.

Hereinafter, a more specific description will be given. FIG. 1 is a cross-sectional view of an optical information recording medium 1 according to the present invention. The optical information recording medium 1 includes a light-transmitting substrate 2, a light absorbing layer 3 formed on the substrate 2, and a light absorbing layer 3. Light reflection layer 4 formed on
And a protective layer 5 formed on the light reflecting layer 4.

The substrate 2 has a pre-groove 6 formed in a spiral shape. On the left and right sides of the pre-groove 6, portions other than the pre-groove 6, that is, lands 7 are located.

The light absorbing layer 3 contains a light absorbing substance composed of a dye that absorbs the laser light L1.

Note that the substrate 2 and the light absorbing layer 3 are in contact with each other by a first layer boundary 8. The light absorbing layer 3 and the light reflecting layer 4 are in contact with each other by a second layer boundary 9. The light reflection layer 4 and the protection layer 5 are in contact with each other by a third layer boundary 10.

As shown, when the optical information recording medium 1 is irradiated with recording light (recording laser light) L1, the light absorbing layer 3 generates heat by absorbing the energy of the laser light L1 and the substrate 2 emits heat. The pits 11 are formed due to thermal deformation on the side. Further, by irradiating a reproduction light (reproduction laser light) L2, a pit contrast is obtained by diffraction of light generated by an optical phase difference between the pit 11 and the non-pit portion (land 7) to read information. Things.

The average thickness of the light absorbing layer 3 is defined as Dav. The average thickness Dav is represented by (volume of the light absorbing layer 3) / (area of the region where the light absorbing layer 3 is formed). The film thickness of the light absorbing layer 3 at the pregroove 6 portion is defined as Dg.

In the optical information recording medium 1 according to the present invention, the average thickness Dav of the light absorbing layer 3 and the residual dye ratio E in the light absorbing layer 3 are within the above-mentioned ranges, that is, 40 nm ≦
By setting Dav ≦ 100 nm and 0.6 ≦ E ≦ 0.9, the amount of heat generated at the time of high-speed recording can be suppressed, and heat conduction to the light reflecting layer made of metal or the like is sufficiently performed. be able to.

Therefore, when recording one pit 11, the difference in thermal state between the initial stage and the final stage of recording is small, and as a result, it is possible to obtain the recording pit 11 which is less affected by thermal interference.

When the average film thickness Dav of the light absorbing layer 3 is larger than the above range, the influence of thermal interference is large, and the optical information recording with sufficiently good jitter characteristics and BLER characteristics at the time of high-speed recording. I can't get the media. If the average film thickness Dav of the light absorbing layer 3 is smaller than the above range, the heat radiation to the light reflecting layer 4 is too large.
There is a problem that sufficient recording cannot be performed and the power of the laser beam L1 for recording must be increased more than necessary.

As described above, a CD-R (writable optical information recording medium) obtains a pit contrast by diffraction of light generated from an optical phase difference between a pit portion and a non-pit portion. . The optical phase difference ΔP is generally represented by ΔP = Δn · d / λ (1) Here, Δn is the difference between the refractive index of the light absorbing layer 3 in the pit portion and the non-pit portion, and d is the thickness (nm) of the light absorbing layer 3 (the average film thickness Dav in the present invention, or on the pregroove 6). Of the light absorbing layer 3), λ
Is the wavelength (n) of the wavelength of the reproduction light (reproduction laser light) L2.
m).

As shown in the above equation (1), the optical phase difference ΔP
Is proportional to the product of the refractive index difference Δn in the light absorbing layer 3 and the thickness d of the light absorbing layer 3. In high-speed recording, as described above, the smaller the thickness d of the light absorbing layer 3 is, the more advantageous it is because the influence of heat generation and heat interference can be reduced. In order to obtain the above-mentioned degree of modulation, it is necessary to make ΔP as a whole higher than the current level, and therefore, it is necessary to make the refractive index difference Δn considerably larger than before.

In order to increase the refractive index difference Δn, it is essential to decompose the dye molecules in the light absorbing layer 3 with higher efficiency. The present inventor has proposed an average film thickness Dav
Within the range (40 nm ≦ Dav ≦ 100 nm),
When the spectral peak ratio in the light absorbing layer 3 before and after recording satisfies 0.6 ≦ E ≦ 0.9, it is found that sufficient modulation can be obtained even if the light absorbing layer 3 is thin. Was. However, the dye remaining ratio E in the light absorbing layer 3 is specifically: E = (film solution spectral peak of light absorbing layer 3 after recording) / (film solution spectral peak of light absorbing layer 3 before recording) It is.

If the dye remaining ratio E is larger than 0.9, the dye is not sufficiently decomposed at the time of forming the pits 11 and the CD
Sufficient modulation that satisfies the standard cannot be obtained. On the other hand, when the dye remaining ratio E is smaller than 0.6, the dye is excessively decomposed, which causes problems such as an increase in crosstalk and an increase in noise level.

In order to keep the dye remaining ratio E in the above-mentioned range within the above-mentioned average film thickness Dav, it is necessary to carry out the dye decomposition more efficiently than in the prior art. It is preferable to contain 80% by weight or more of a single or plural kinds of carbocyanine dyes that absorb and sensitize the recording laser beam L1 and exothermicly decompose at a temperature of 300 ° C. or lower.

Further, the thickness Dg of the light absorbing layer 3 on the pre-groove 6 is desirably 60 nm ≦ Dg ≦ 140 nm. Thickness D on this pre-groove 6
If g is larger than the above range, the influence of thermal interference is large, and it is not possible to obtain an optical information recording medium having sufficiently good jitter characteristics and BLER characteristics at the time of high-speed recording. If it is smaller than the above range, the heat radiation to the light reflection layer 4 is too large, so that sufficient recording cannot be performed, and the power of the laser beam L1 for recording must be increased more than necessary. Problem arises.

[0030]

Next, an optical information recording medium according to an embodiment of the present invention will be described with reference to FIGS. 0.55μ width
m, a depth of 170 nm, a spiral pre-groove 6 having a pitch of 1.6 μm, a thickness of 1.2 mm, and an outer diameter of 1
20 mm, inner diameter 15 mm polycarbonate substrate 2
Is obtained by an injection molding method.

Next, as a recording dye, a carbocyanine dye having a structure shown in FIG.
19) 85 parts by weight as a stabilizer together with 15 parts by weight of a near-infrared absorbing dye (product number IRG-003, manufactured by Nippon Kayaku Co., Ltd.) having a structure shown in FIG.
Dissolve with 25 grams / liter of methyl cellosolve,
This is applied on the substrate 2 by spin coating,
The light absorbing layer 3 having an average film thickness Dav = 70 nm was formed. At this time, the film thickness Dg on the pre-groove 6 was 105 nm. The benzoindolenine cyanine dye has a wavelength of 78
It was known that the material absorbed a laser beam of 0 nm and decomposed by heat. The decomposition temperature was 287 ° C.

A 100 nm thick light reflecting layer 4 made of gold (Au) is formed on the substrate 2 having the dye film by RF sputtering, and an ultraviolet curable resin (Dainippon Ink Co., Ltd.) is formed on the light reflecting layer 4. Chemical Industry Co., Ltd., SD-211)
Is spin-coated, and further irradiated with ultraviolet rays to a thickness of 10 μm.
m of protective layers 5 were formed.

Using the recording device (manufactured by Philips, CDD-2000) using a laser beam L1 having a wavelength of 780 nm on the optical information recording medium thus obtained, reproduction evaluation was performed at a linear velocity of 1.2 m / s over the entire surface of the disk. Was performed, I11 / Itop = 0.63, I3 / Itop = 0.31,
When BLER was 1.3 cps, the CD standard was satisfied, and good characteristics of jitter of 35 ns or less were obtained in all signal regions.

The light absorbing layer 3 of the disc after recording is 200 m
The solution was eluted with 1 liter of ethanol, and the solution spectrum was measured. As shown in FIG. 4, the peak value of the absorption spectrum was 0.833 Abs. The light absorbing layer 3 is formed on the substrate 2
After the protective layer 5 was removed, the light reflecting layer 4 was peeled off, and the ethanol was removed from both the dye on the substrate 2 and the dye adhering to the light reflecting layer 4. And washed.

In an unrecorded disk produced in the same manner, as shown in FIG.
Since it was 957 Abs, the dye remaining ratio E in the light absorbing layer 3 was 0.87.

A disk manufactured in the same manner has a wavelength of 783 nm.
Using a laser beam (PCD, manufactured by Kodak Co., Ltd.)
A Writer 600) was used to record an EFM signal at a linear velocity of 7.2 m / s at a linear velocity of 7.2 m / s at a 6-times speed, and the reproduction was evaluated in the same manner as described above.
0.76, I3 / Itop = 0.34, BLER = 2.1c
In ps, the CD standard was satisfied, and good characteristics of jitter of 35 ns or less were obtained in all signal regions.

The light absorbing layer 3 of the recorded disk is
The solution was eluted with 1 l of ethanol, and the solution spectrum was measured. The peak value of the absorption spectrum was 0.720 Abs. In an unrecorded disk similarly prepared, since the absorption spectrum peak value was 0.957 Abs, the dye remaining ratio E was 0.75.

[0038]

Comparative Example A carbocyanine dye (NK-3219) 35 having the structure shown in FIG. 2, which is a benzoindolenine cyanine dye, was prepared on a substrate 2 similar to that used in the example.
Parts by weight, and an indocyanine dye having the structure shown in FIG.
3345) 50 parts by weight of an aminium salt, FIG.
(IRG-003) 15
Together with parts by weight, it was dissolved in methyl cellosolve at 25 grams / liter.

This solution was spin-coated on the substrate 2 to obtain an average film thickness Dav = 68 nm and a film thickness Dg on the pregroove 6.
A disk was produced in the same manner as in the example except that the light absorption layer 3 having a thickness of 104 nm was provided.

The dye (NK-3345) shown in FIG.
Does not have a light absorption band near the wavelength of 780 nm, and cannot absorb or emit laser light having a wavelength of 780 nm to generate or decompose it. The thermal decomposition temperature is 271 ° C.

The disk obtained in this manner was subjected to a linear velocity of 1. using the same recorder (CDD-2000) as in the example.
The same constant speed recording was performed at 2 m / s. When this was evaluated for recording using the same reproducing machine, I11 / Itop =
0.42, I3 / Itop = 0.19, BLER = 310c
In ps, the CD standard was not satisfied.

The solution spectrum of the disc after recording and the light absorbing layer 3 of the unrecorded disc were measured in the same manner as in the example. The peak of the absorption spectrum was 0.972 Abs after recording. 1.0 in the state
31 Abs, and thus the residual dye ratio E was 0.9
42.

When recording at 6 × speed was performed in the same manner as in the embodiment and the reproduction was evaluated, I11 / Itop = 0.58 and I3 / Ito
p = 0.26 and BLER = 250 cps, which did not satisfy the CD standard. When the same solution spectrum was measured for this disk, the absorption spectrum peak value was 0.938 Abs after recording, and was 1.031 Abs in the unrecorded state. Therefore, the dye residual ratio E was 0.941. .

[0044]

As described above, according to the present invention, the average film thickness of the light absorbing layer and the residual ratio of the dye are regulated within predetermined ranges. Thus, an optical information recording medium having a sufficient modulation degree margin can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical information recording medium 1 according to the present invention.

FIG. 2 shows a benzoindolenine cyanine dye (carbocyanine dye) used as a recording dye in the example.
(Product number NK-3219, manufactured by Japan Photosensitive Dye Laboratories Inc.)
FIG. 3 is a diagram showing a structural formula of FIG.

FIG. 3 is a view showing a structural formula of a near-infrared absorbing dye (manufactured by Nippon Kayaku Co., Ltd., product number IRG-003) used in Examples.

FIG. 4 is a graph showing a solution spectrum of the light absorbing layer 3 of the disc after recording in the example.

FIG. 5 is a graph showing a solution spectrum of a light absorption layer 3 of a disc in an unrecorded state in the example.

FIG. 6 is a view showing the structural formula of a dye (product number NK-3345, manufactured by Japan Photographic Dye Laboratories Co., Ltd.) used in a comparative example.

[Explanation of symbols]

 Reference Signs List 1 optical information recording medium (FIG. 1) 2 translucent substrate 3 light absorbing layer 4 light reflecting layer 5 protective layer 6 spiral pregroove 7 land 8 first layer boundary 9 second layer boundary 10 third Layer boundary 11 pits L1 Recording light (recording laser light) L2 Reproduction light (reproduction laser light) Dav Average thickness of light absorption layer 3 Dg Thickness of light absorption layer 3 on pregroove 6

Claims (3)

[Claims] 1. A substrate having a light-transmitting property and having a pregroove formed thereon, a light-absorbing layer provided on the substrate and containing a light-absorbing substance composed of a dye absorbing recording light by laser light, An optical information recording medium provided on a light absorbing layer and recording light by irradiating the light absorbing layer with the recording light, the light information recording medium comprising: When the average film thickness Dav of the layer is 40 nm ≦ Dav ≦ 100 nm, and the EFM signal recording is performed at the optimum power, the dye remaining ratio E in the light absorbing layer is 0.6 ≦ E ≦ 0.9. An optical information recording medium, characterized in that: 2. The optical information recording medium according to claim 1, wherein the thickness Dg of the light absorbing layer on the pregroove satisfies 60 nm ≦ Dg ≦ 140 nm. 3. The light absorbing layer according to claim 1, wherein the light absorbing layer has one or more kinds of carbocyanine dyes and contains at least 80 wt% of a substance that absorbs the recording light and decomposes by heat. Optical information recording medium.