JP2002123974A - Optical recording medium and optical recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium which ensures a satisfactory reflectance even under any laser light for reproduction in the range of 750-830 nm and enables good reproduction and to provide an optical recording and reproducing method. SOLUTION: The optical recording medium has a recording layer 3 containing a cyanine organic dye and a reflecting layer 4 in this order on a light transmissive substrate 2. A signal corresponding to information to be recorded is written in the medium by irradiating the medium with laser light for recording having 770-800 nm wavelength from the substrate side to record the information. After this recording, at least part of the cyanine organic dye in the recording layer 3 is faded with light energy in such a way that the difference between the maximum and minimum reflectances of the unrecorded part to light in the range of 750-830 nm from the substrate side is adjusted to <=20% and the recorded signal is read by irradiating the medium with laser light for reproduction having 750-830 nm wavelength from the substrate side to reproduce the information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical recording medium having a recording layer containing an organic dye and a reflective layer on a light transmitting substrate in this order, and an optical recording / reproducing method using the optical recording medium.

[0002]

2. Description of the Related Art In recent years, as an information recording medium, a recordable optical recording medium CD-R (Recordable Comparator) having a dye recording layer has been used.
ct Disk) has been put to practical use.

The basic structure of a write-once type optical recording medium having a dye recording layer mainly includes an organic dye such as a cyanine dye, a phthalocyanine dye, or an azo dye on a light-transmitting substrate made of plastic such as polycarbonate or polyolefin. It is well known that a dye recording layer as a component is provided, and a light reflection layer capable of obtaining a relatively high reflectance such as gold or silver is provided on the recording layer. A concave pre-groove is formed on the surface of the light-transmitting substrate on the recording layer side in advance so as to guide the scanning of the laser light to be irradiated and to accurately follow the position where the laser light is to be irradiated. Have been. A protective layer is usually provided on the light reflecting layer.

When information is recorded on an optical recording medium having such a dye recording layer, a recording laser beam modulated with a signal (usually a digital signal) corresponding to the information to be recorded is transmitted from the light transmitting substrate side. By irradiation, a recording area portion (generally called a pit regardless of the state of the recording area portion) corresponding to the signal is formed in the dye recording layer. When reproducing recorded information, the dye recording layer is irradiated with a laser beam for reproduction, and the reflectance for laser light between the recording area (pit) of the dye recording layer and the surrounding unrecorded area is measured. The recorded signal is read using the difference between the two, and then the recorded signal is reproduced.

In designing an optical recording medium having a dye recording layer, a dye must be selected according to the wavelength of a laser beam used for recording and reproducing on the optical recording medium in order to perform good recording and reproduction. That is, at the time of recording information, it is necessary that the dye layer appropriately absorbs the recording laser light to form pits, while at the time of information reproduction, the dye layer in the unrecorded area is used for reproduction. It is necessary that the laser beam is appropriately reflected and / or transmitted (reflected by the light reflection layer) to obtain a high reflectance.

[0006] Dyes have a wavelength dependence, and while exhibiting appropriate light absorption and / or transmission in a specific wavelength region, they hardly absorb light in other specific wavelength regions, or conversely, emit light. It has properties such as excessive absorption. Due to the wavelength dependence of the dye, a recording laser beam and a reproduction laser beam having substantially the same wavelength region are used for recording and reproduction on an optical recording medium having a dye recording layer. For example, in a CD-R, a recording laser beam having a wavelength of 770 to 800 nm and a reproducing laser beam having a wavelength of 750 to 830 nm are used. In a DVD-R, the wavelength is 635 nm or 6 nm.
A 50 nm recording laser beam and a 650 nm wavelength reproducing laser beam are used.

However, in the range of 750 to 830 nm, the change in the absorbance of an organic dye such as a pentamethine cyanine dye with respect to the wavelength is large. For example, in the case of a pentamethine cyanine dye, in terms of the reflectance in the state of the dye recording layer, the reflectance generally decreases as the wavelength approaches 750 nm.
The reflectance increases as the wavelength approaches 830 nm. For this reason, even if the wavelength of the reproduction laser beam is slightly shifted to the short wavelength side due to the temperature dependency of the laser, etc., the reflectivity of the unrecorded area may be significantly reduced, and good reproduction may be hindered. Becomes In addition, the wavelength of the laser beam for reproduction differs depending on the reproducing machine, and in the case of a reproducing machine using a laser beam for reproducing with a shorter wavelength, a sufficient reflectivity of an unrecorded area portion cannot be obtained, and good reproduction may be difficult. is there.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to
A novel dye recording layer having a dye recording layer recordable with a recording laser beam having a wavelength of 0 to 800 nm, a sufficient reflectance being obtained by any of the reproducing laser beams having a wavelength of 750 to 830 nm, and good reproduction being possible. Another object of the present invention is to provide a simple optical recording medium. Another object of the present invention is to provide a novel optical recording / reproducing method using the optical recording medium.

[0009]

Means for Solving the Problems The present inventors have written (recorded) information on an optical recording medium having a dye recording layer.
The dye in the recording layer is faded or decolored, and 75
By setting the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 0 to 830 nm to 20% or less, the difference in the wavelength of the laser light for reproduction is not affected by a slight shift. It has been found that good reproduction can be performed without selecting a type of a reproducing machine using a reproducing laser beam.

That is, according to the present invention, after information is recorded, the dye in the recording layer is faded or decolored, and the unrecorded portion 7
By setting the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 50 to 830 nm to not more than 20%, a high reflectance at the time of reproduction can be obtained by the reproduction laser light of any wavelength within this wavelength range. Based on the principle.

The present invention relates to an optical recording medium having, in this order, a recording layer containing a cyanine dye and an organic dye on a light-transmitting substrate, and a signal corresponding to information to be recorded.
Writing and recording information by irradiating a recording laser beam having a wavelength of 770 to 800 nm from the substrate side, and after recording, at least a part of the cyanine-based organic dye in the recording layer is unrecorded by treatment with light energy. Part 75
An optical recording medium wherein the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 0 to 830 nm is 20% or less.

The present invention relates to the above optical recording medium, wherein the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 750 to 830 nm of the unrecorded portion before the treatment with light energy is 50% or more. is there. The present invention is the optical recording medium, wherein the optical recording medium contains a pentamethine cyanine dye as the cyanine dye organic dye. The present invention is the optical recording medium, wherein the recording layer optionally contains a singlet oxygen quencher of 10% by weight or less based on the whole organic dye.

According to the present invention, a signal corresponding to information to be recorded is transmitted from the substrate side to an optical recording medium having a recording layer containing a cyanine-based organic dye and a reflective layer on a light transmitting substrate in this order. Writing by irradiating a recording laser beam having a wavelength of 770 to 800 nm, recording information, and after recording,
At least a part of the cyanine organic dye in the recording layer is irradiated with light energy to 750 to 830 nm in an unrecorded portion.
And a laser beam for reproduction having a wavelength of 750 to 830 nm is applied to the optical recording medium after the bleaching process so that the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range described above is 20% or less. An optical recording / reproducing method including irradiating from the side to read a recording signal and reproduce information.

According to the present invention, there is provided the optical recording medium as described above, wherein the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 750 to 830 nm of the unrecorded portion is 50% or more in the optical recording medium before the fading process. It is a reproduction method. The present invention is the optical recording / reproducing method, wherein a pentamethine cyanine dye is used as the cyanine-based organic dye. The present invention is the optical recording / reproducing method, wherein the recording layer contains, as necessary, a singlet oxygen quencher of 10% by weight or less based on the whole organic dye.

According to the present invention, the dye of the recording layer is faded or decolored after information is recorded, and the unrecorded portion of 750 is recorded.
By setting the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 〜830 nm to not more than 20%, the reflectance at the time of reproduction is high even with the reproduction laser light of any wavelength within this wavelength range. And good reproduction can be performed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIG. FIG. 1 is a sectional view showing an example of a layer configuration of the optical recording medium of the present invention. In FIG. 1, an optical recording medium (1) has a dye recording layer (3) mainly containing a cyanine-based organic dye on a disk-shaped light-transmitting substrate (2). It has a reflective layer (4), and usually, an organic protective layer (5) is provided on the light reflective layer (4). Further, a structure in which two disks are bonded may be adopted. The shape of the optical recording medium used in the present invention, in addition to a disk shape, for example, a card type,
Alternatively, it may be shaped like a magnetic tape.

The light transmissive substrate (2) is made of, for example, glass, acrylic resin such as polymethyl methacrylate, polyvinyl chloride resin such as polyvinyl chloride or vinyl chloride copolymer, epoxy resin, polycarbonate resin, polyolefin resin, or It is formed from various materials such as polyester resin. Here, the “light transmitting property” means a property that both the recording laser light and the reproducing laser light can be transmitted. Among these materials, good light transmittance,
Polycarbonate resins, polyolefin resins, and the like are preferable for various reasons such as ease of molding and low-cost production.

The light-transmitting substrate is usually in the form of a disk, and when used as a CD-R, the thickness is about 1.2 mm.
The diameter is about 80 to 120 mm. The light transmitting substrate may be manufactured according to a known method such as injection molding. At this time, it is preferable to form the pregroove (21) on the substrate surface on the side where the dye recording layer (3) is provided, for tracking, addressing, and the like. After manufacturing the substrate, a resin layer having a pre-groove may be formed by a 2P method or the like.

The pre-groove (21) is preferably a spiral continuous groove having a depth of 10 to 500 nm.
Preferably 50 to 300 nm, width 0.2 to 1.1 μm
m, and the width of the land (portion between adjacent pregrooves) is preferably 0.3 to 1.4 μm. With such a configuration of the pre-groove, a good tracking signal can be obtained without lowering the reflection level of the groove portion. Note that the pregrooves and lands may be provided with irregularities for address signals. Further, it is preferable that the recording light is applied to the recording layer in the pre-groove.

On the substrate surface on the side where the dye recording layer (3) is provided, the flatness is improved, the adhesive strength with the dye recording layer is improved, the solvent resistance of the light transmitting substrate is improved, and the dye recording layer is deteriorated. An undercoat layer may be provided for the purpose of, for example, preventing the occurrence of an undercoat. The undercoat layer generally has a thickness of 0.005 to 20 μm, preferably 0.01 to 20 μm.
It is provided with a thickness of 10 to 10 μm.

A dye recording layer (3) containing a cyanine-based organic dye as a main component is formed on the light transmitting substrate (2) or the undercoat layer. As the cyanine organic dye for the dye recording layer (3),
There is no particular limitation as long as the recording area (pit) is formed by a recording laser beam having a wavelength in the range of 770 to 800 nm, and after recording, the recording area is faded or erased by light energy. For example, as the cyanine-based organic dye, a pentamethine cyanine-based dye, a trimethine cyanine-based dye, a monomethine cyanine-based dye, and the like which have been conventionally used in an optical recording medium can be used. When selecting a cyanine-based organic dye, in the fading treatment after information recording, appropriate fading or decoloring is performed by applying an appropriate light energy that does not adversely affect the optical recording medium (for example, deterioration of pits or the like). It is preferable to choose one. In the present invention, only one organic dye may be used, or two or more organic dyes may be used in combination. It can also be used in combination with various auxiliary components. The mechanism of fading is considered to be due to cleavage of the methine chain constituting the dye, but the details are not clear.

In the present invention, a pentamethine cyanine dye is preferable because a recording laser beam having a wavelength in the range of 770 to 800 nm is used as the cyanine-based organic dye.

The pentamethine cyanine dye is represented by the general formula (A).

Embedded image (Where Q and Q ′ each represent a condensed aromatic ring, R1 and R1 ′ each represent a substituted or unsubstituted alkyl group, and R2, R2 ′, R3, and R3 ′ represent
L represents an alkyl group or an aryl group,
Represents a pentamethine linking group to form a cyanine dye, X ^- represents an anion, m is 0 or 1. )

Specific examples of the above formula (A) include, but are not particularly limited to, the following pentamethine cyanine dyes (B) to (D).

Embedded image

Embedded image

Embedded image

Each of these pentamethine cyanine dyes is a cyanine dye having a maximum absorption wavelength near 680 nm when a thin film is formed, and is applicable to recording with a laser light wavelength near 770 to 800 nm. These dyes may be used alone or in combination of two or more.

As for the absorption spectrum (maximum absorption wavelength) of the organic dye, the absorption spectrum at the time of forming the thin film is important in order to function as the dye recording layer of the optical recording medium.
The absorption spectrum of a thin film generally behaves differently from the absorption spectrum in a solution. An example of measuring an absorption spectrum of a thin film will be described. The dye whose absorption spectrum is to be measured is dissolved in an organic solvent having a boiling point in the air of 50 to 180 ° C. at a concentration of 1 to 20% by weight. The solution is applied by a spin coating method onto a polycarbonate flat plate having no grooves or pits so as to have a film thickness of about 60 to 200 nm so that the dye does not have a specific orientation.
Dye is remarkably crystallized during solvent evaporation during spin coating,
Alternatively, in the case of association, another solvent is selected. In general, the transmission absorption spectrum of the polycarbonate substrate with the dye thin film thus prepared is measured with a spectrophotometer.

It is preferable that the dye recording layer does not contain a component such as a singlet oxygen quencher that hinders fading, but a small amount can be added to stabilize the dye before recording. When using a singlet oxygen quencher, the content is 10% by weight or less based on the whole organic dye,
It is preferably at most 5% by weight. When the content of the quencher exceeds 10% by weight, it is difficult to obtain good fading due to the fact that it takes a long time for fading, depending on the structure and stability of the dye.

Examples of the quencher include metal complexes such as acetylacetonate-based, bisdithio-α-diketone-based and bisphenyldithiol-based bisdithiol-based, thiocatechol-based, salicylaldehyde oxime-based, and thiobisphenolate-based metal complexes. Can be In addition, an amine-based quencher such as an amine-based compound having a nitrogen radical cation or a hindered amine may also be used.

The dye recording layer can be formed by a spin coating method as in the prior art. That is, a dye and, if necessary, a singlet oxygen quencher, a binder and the like are dissolved in an appropriate solvent to prepare a coating solution, and the coating solution is applied on a substrate by spin coating, and applied as needed. Dry the membrane. Further, a coating method such as a screen printing method and a dipping method may be used. The organic solvent used in the coating liquid for forming the recording layer may be appropriately selected from alcohols, ketones, esters, ethers, aromatics, fluorines, alkyl halides, and the like depending on the dye used. I just need. The thickness of the dye recording layer is generally 10 at the groove.
５００500 nm, preferably 50-300 nm.
nm range.

In the present invention, a light reflecting layer (4) is provided on the dye recording layer (3). The light reflecting layer is made of Au, Ag, Al, Cu, P
It is generally composed of metallic materials such as t, Ni and Cr.
The light reflecting layer can be formed by various vapor deposition methods such as sputtering, vapor deposition, and ion plating.
As a material of the light reflection layer, an inorganic substance can be used in addition to metal. Conventionally, Au was mainly used, but has been replaced by Ag which is inexpensive and has high reflectivity.

In particular, in the present invention, the organic dye in the recording layer is faded or decolored after information is recorded, so that the recording layer has a very high transmittance of reproducing laser light during reproduction. For this reason, although the reflectivity is lower than that of Ag, inexpensive A
Replacement with l or the like is also possible. Al is CD-RO
It is used for M and music CDs and has a reflectance that can be put to practical use. Also, since the recording layer mainly uses a highly sensitive cyanine dye, it is possible to form a thin dye recording layer in which the amount of the organic dye is originally reduced. In this respect, the transmittance of the reproducing laser beam is high, and Al and the like are used. Replacement with is also possible. Generally, the thickness of the light reflecting layer is preferably in the range of 10 to 300 nm.

An organic protective layer (5) is usually provided on the light reflecting layer (4).
Is provided. The protective film only needs to be able to protect the organic dye recording film and the reflective film, and the constituent material of the protective film is not particularly limited. As a material of the protective film, an ultraviolet curable acrylic resin is generally used because the protective film can be easily formed. The material of the protective film may be an organic material such as a vinyl chloride resin, an epoxy resin, or a polyester resin, or an inorganic material such as SiO ₂ or AlN. These materials may be used alone or as a mixture. In addition, different materials may be used in layers by using the protective film as a multilayer film. The thickness of the organic protective layer is
Generally, it is in the range of 1 to 50 μm. The protective film is preferably formed by a spin coating method in order to avoid damage to the reflective film, but may be formed by a screen printing method, a dipping method, a spray coating method, or the like.

A label printing layer may be further provided on the organic protective layer (5). Alternatively, in the case where such an optical recording medium is attached with an adhesive layer provided on the side opposite to the light incident surface, the adhesive layer may also serve as a protective film.

The optical recording / reproducing method of the present invention is carried out by the following steps using the above optical recording medium. The optical recording medium is irradiated with a recording laser beam having a wavelength of 770 to 800 nm modulated with a signal such as a digital signal corresponding to the information to be recorded from the light-transmitting substrate side, and the dye recording layer responds to the signal. Information recording step of forming a recording area (pit) to be recorded. A fading process for fading the dye in the dye recording layer. In this step, the dye is bleached so that the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 750 to 830 nm of the unrecorded area becomes 20% or less. After the fading treatment, the substrate is irradiated with a reproducing laser light having a wavelength of 750 to 830 nm from the substrate side, and the reflectance of the dye recording layer after the fading treatment with respect to the reproducing laser light between the recording region and the unrecorded region is measured. An information reproducing step of reading a digital signal using the difference and reproducing the digital signal.

According to the optical recording / reproducing method of the present invention, the above-described new fading process is performed, and then the reproducing process is performed. The step of recording information on the optical recording medium can be performed by a conventional method.

Information Recording Step Information is recorded on an optical recording medium by irradiating a recording laser beam modulated with a signal such as a digital signal corresponding to the information to be recorded from the light-transmitting substrate side to a dye recording layer. First, a recording area (pit) corresponding to the signal is formed. That is, as a result of the laser irradiation area of the dye recording layer absorbing light and locally increasing the temperature, the organic dye is altered and pits are formed. Information is recorded by changing the optical characteristics of the recording area. In the present invention, 7
A recording laser beam having a wavelength in the range of 70 to 800 nm is used. Depending on the organic dye applied to the recording layer, laser light having a wavelength in this range can be selected.

Dye Discoloration Treatment Step After forming the pits as described above, light energy is applied to the dye recording layer to cause the organic dye in the dye recording layer to fade or decolor.

In an optical recording medium in which a pentamethine cyanine dye is used for the dye recording layer, before the fading treatment, generally, the maximum value (rf _max) of the reflectance from the substrate side in the range of 750 to 830 nm of the unrecorded portion. ) And the minimum value (rf
_min ) is 50% or more. That is, rf _max −
rf _min ≧ 50%. Usually, rf _max is 830n
m is obtained on the long wavelength side near m, and rf _min is obtained on the short wavelength side near 750 nm. Since the change in the reflectance with respect to the wavelength is large, unless the dye is subjected to the fading treatment, the reflectance of the unrecorded area decreases due to the shift of the wavelength of the reproducing laser light (particularly, shift toward the short wavelength side), Good reproduction becomes difficult.

In the present invention, in the dye fading process, the difference between the maximum value (Rf _max ) and the minimum value (Rf _min ) of the reflectance from the substrate side in the range of 750 to 830 nm in the unrecorded area is determined. The color of the dye is faded to 20% or less, preferably 10% or less. Rf _max- Rf _min
≦ 20%. The wavelength at which Rf _max and Rf _min are obtained depends on the dye or the fading condition, and is 750 to 830.
It can vary in the nm range.

As described above, according to the present invention, before the fading process,
In this case, the maximum value of the reflectance (rf_{ma x}) And the minimum value (rf
_min) Was 50% or more.
In other words, the change in reflectance with wavelength is large and quite small.
(There are wavelengths for which only reflectance can be obtained)
Therefore, the maximum value of the reflectance (Rf_max) And the minimum value (Rf
_min) Is 20% or less. As a result, the fading process
Later, in the entire range of 750 to 830 nm, high anti-
Emissivity, for example, a reflectance of 60% or more is obtained.
Good reproduction by any reproducing laser light of any wavelength
Is achieved.

Here, the reflectance from the substrate side can be easily measured using a spectrophotometer. The reflectance measured by this spectrophotometer is one of the standard discs
The value approximates the measured value of the reflectance by laser light from a measuring device or a reproducing device calibrated by the PHILIPS STANDARD DISC "5B", and is approximately the same value if the reflectance of the same disc is measured by both measuring methods Becomes

With respect to the degree of fading of the dye, Rf _max −
Rf _min ≦ 20% may be satisfied, and fading is not necessarily required until the dye recording layer becomes colorless. If the degree of color fading of the dye increases and the organic dye layer becomes almost colorless by decoloring, a very high reflectance can be obtained in the entire range of 750 to 830 nm.

After the information recording on the optical recording medium is completed, the fading processing can be performed, for example, by applying light energy to the entire surface of the optical recording medium.

In order to give light energy, it is possible to irradiate ultraviolet light, electron beam or visible light. In particular, in the present invention, it is preferable to irradiate ultraviolet rays. As the ultraviolet ray source, a mercury lamp, preferably a xenon lamp light or a light source having a shorter wavelength may be used. The amount of light energy (light amount) required for dye fading is determined by the amount of organic dye that constitutes the dye recording layer,
And other components (eg, the singlet oxygen quencher, radical generator, etc.). For example, when using xenon lamp light or the like, the integrated light amount is 10 to 1
It is preferable to irradiate at an amount in the range of 0000 klx · h (kilolux × hour).

In the fading treatment, it is necessary to pay attention so that the organic dye in the dye recording layer is faded or decolored so as not to adversely affect other portions of the optical recording medium. If it has an adverse effect, good reproduction cannot be performed.

Information Reproducing Step After the color fading process, a laser beam for reproduction having a wavelength of 750 to 830 nm is irradiated from the substrate side to reproduce between the recording area portion and the unrecorded area portion of the dye recording layer after the color fading process. A digital signal is read using the difference in reflectance with respect to laser light. This step itself is the same as the conventional one, but 750 to 83
It is an advantage of the present invention that good reproduction is achieved with reproduction laser light of any wavelength in the range of 0 nm. That is, after the fading process, the change in reflectance with respect to wavelength in the range of 750 to 830 nm is very small,
And the reflectance is high. Therefore, there is no problem with a shift in the wavelength of the laser beam for reproduction due to the temperature dependence or a variation in the wavelength of the laser beam for reproduction due to the difference in the reproducing machine.

In the reproducing step, the reflectivity of the reproducing laser beam may have a different value depending on the configuration of the pickup head used for the measurement. The reflectance of the reproduction laser light shown in this specification, unless otherwise specified,
PHILIPS STANDARD DISC "5
It is a measured value by laser light in a measuring device or a reproducing device calibrated by “B”. By performing the fading process,
At the time of reproduction, a reflectance of 45% or more, preferably 65% or more of the reproduction laser beam is obtained.

[0048]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. In particular, as the wavelength of the light used for the fading process, light having a shorter wavelength can be applied in addition to the xenon lamp light.

[Example 1] 2 g of the cyanine dye represented by the above (B) was added to 2,2,3,3-tetrafluoro-1-
It was dissolved in 100 g of propanol (TFP) to prepare a coating solution. The coating solution was applied onto a polycarbonate injection molded substrate having a diameter of 120 mm and a thickness of 1.2 mm having a pregroove having a depth of 180 nm by a spin coating method and dried. In the spin coating, the initial rotation speed when the coating solution was dropped onto the substrate was set to 300 to 500 rpm, and the rotation speed was gradually increased to finally reach 5000 rpm. After drying, the thickness is 100 nm by sputtering.
Of UV-curable acrylic resin (DAICURE CLEAR SD318 (manufactured by Dainippon Ink and Chemicals, Inc.)) is further applied thereon by spin coating to form a protective film having a thickness of 5 μm. Thus, an optical recording medium of the present invention was produced. The thickness of the dye recording layer is 200 to 3 in the groove portion.
00 (approximately 250) nm. (15 in the land
(About 0 nm)

Recording was performed on the obtained optical recording medium with a recording device (DDU1000, manufactured by Pulstec) having a semiconductor laser beam having a wavelength of 780 nm at a constant linear speed of 1.2 m / sec and a recording power of 6.0 mW. went. A xenon lamp (Xenon fade-Ometer) is provided on the dye recording layer of the optical recording medium after recording.
2000 klx using Ci35AF (6500W) manufactured by Atlas
The recording layer was discolored by irradiating light with the integrated light quantity of h.

Before and after the fading treatment, a fine spectrophotometer (MPS-200, manufactured by Shimadzu Corp.)
The reflectance from the substrate side in the range of 50 to 830 nm was measured. Before the fading process, the difference between the maximum value and the minimum value of the reflectance was 50% or more, but after the fading process, the maximum value: 9
0%, minimum value: 80%, and the difference between them was 20% or less. The reflectance measured value by the spectrophotometer is a value that is close to the measured value by a laser beam in a reproducing machine calibrated by PHILIPS STANDARD DISC “5B” which is one of the standard disks.

After the fading process, the recorded signal is reproduced by a reproducing device (DD) having a semiconductor laser beam having a wavelength of 780 nm.
U1000 (manufactured by Pulstec) at a constant linear velocity of 1.2 m / sec and a reproduction power of 0.7 mW. Using the same player, measure the amount of reflected light when the reflectance at this wavelength is tracked in an unrecorded premises, and a medium with a known reflectance PHILIPS STANDARD DI
It was 60% or more when measured by comparing with the reflected light amount of SC “5B”. Reproduction laser light wavelength 830
Similarly, when the recorded signal was reproduced in place of nm or 750 nm, good reproduction was possible. Similarly, when the reflectance at these wavelengths was measured, it was 60% or more.

Example 2 An optical recording medium was prepared in the same manner as in Example 1, except that the dye used was changed to the cyanine dye shown in (C). Reproduction evaluation was performed. Before and after the fading treatment, the same result of the reflectance by the spectrophotometer as in Example 1 was obtained.
Good reproduction was possible with any of the reproduction laser beams having wavelengths of 780 nm, 830 nm and 750 nm.

Example 3 An optical recording medium was prepared in the same manner as in Example 1, except that the dye used was changed to the cyanine dye shown in (D). Reproduction evaluation was performed. Before and after the fading treatment, the same result of the reflectance by the spectrophotometer as in Example 1 was obtained.
Good reproduction was possible with any of the reproduction laser beams having wavelengths of 780 nm, 830 nm and 750 nm.

Comparative Example 1 Recording, fading, and reproduction evaluation were performed in the same manner as in Example 1 except that a CD-R having a recording layer containing a phthalocyanine dye was used. As a result of measuring the reflectance with the same spectrophotometer as in Example 1 after the fading process, the difference between the maximum value and the minimum value of the reflectance before the fading process was 5%.
The value of 0% or more was almost unchanged after the fading treatment. Further, in the reproducing apparatus having a laser light wavelength of 780 nm, the reproduction signal was slightly deteriorated by the fading process, but reproduction at a practical level was possible. However, laser light wavelength 7
With a reproducing device of 50 to 770 nm, the reflectance was lowered, and a sufficient reproduced signal could not be obtained.

[Comparative Example 2] Recording, fading treatment and reproduction evaluation were performed in the same manner as in Example 1 except that a CD-R having a recording layer containing an azo dye was used. As a result of performing reflectance measurement using the same spectrophotometer as in Example 1 after the fading process, the difference between the maximum value and the minimum value of the reflectance before the fading process was 50% or more, even after the fading process. The value was almost unchanged. Further, in the reproducing apparatus having a laser light wavelength of 780 nm, the reproduction signal was slightly deteriorated by the fading process, but reproduction at a practical level was possible. However, the laser light wavelength 750-7
In the case of a 70-nm reproducing apparatus, the reflectance was lowered, and a sufficient reproducing signal was not obtained.

As described above, according to the present invention, when the fading process is performed after recording information (Examples 1 to 3),
The difference between the maximum value and the minimum value of the reflectance by the spectrophotometer in the range of 50 to 830 nm was 20% or less, and the recording signal could be reproduced well. On the other hand, when a CD-R containing a dye other than a cyanine dye was used, the reflectance was not improved by the bleaching treatment, and the reproduction signal quality was slightly deteriorated in a reproducing machine with a laser wavelength of 780 nm. However, in the case of a reproducing machine having a laser light wavelength of 750 to 770 nm, the reflectance was reduced, and a sufficient reproduced signal was not obtained.

[0058]

According to the present invention, there is provided a novel optical recording / reproducing method in the range of 750 to 830 nm which does not depend on the wavelength of a laser beam during reproduction, and an optical recording medium for use in the method. According to the present invention, the dye in the recording layer is faded after the information is recorded, and good reproduction with few errors can be performed by the reproduction laser light having any wavelength in the range of 750 to 830 nm. Therefore, it is possible to apply a wide range of laser light wavelengths for reproduction,
There is no need to choose the type of regenerator. That is, for example, CD
-An optical recording medium recorded by an R recorder is converted to a conventional commercially available CD.
Good reproduction is possible using any of a player, a CD-ROM drive, and a shorter wavelength reproducing device.

Further, from the viewpoint of the design of the optical recording medium, in the present invention, since the wavelength dependence of the laser beam at the time of reproduction is eliminated, only the dye having high sensitivity at the time of recording is used as the dye of the dye recording layer. be able to. Therefore, the recording sensitivity of the optical recording medium can be kept at the same level as the conventional one with a smaller amount of the dye than before, and the thickness of the dye recording layer can be reduced. As a result, the transmittance of the laser beam during reproduction of the recording layer increases, so that it is possible to change to a reflective layer made of a material which is less reflective than Ag but less expensive than Ag.

From another point of view, since the laser light transmittance for reproduction of the recording layer is enhanced by the fading treatment of the dye, it is possible to use a larger amount of the dye in the recording layer than before. The use of a large amount of dye increases the amount of light absorbed during recording, and can achieve high sensitivity of the optical recording medium. That is, it is possible to increase the recording speed at the time of recording, and it is expected that the recording time will be shortened.

Further, generally, the dye is faded (deteriorated) by irradiation with ordinary light such as sunlight, but when the dye is subjected to the fading treatment as in the present invention, further fading (deterioration) due to light irradiation is very large. Less. Therefore, after recording and fading, the recording layer becomes highly light-resistant, and the stability of the optical recording medium is improved.

[Brief description of the drawings]

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

[Explanation of symbols]

 (1) Optical recording medium (2) Optically transparent substrate (3) Dye recording layer (4) Light reflecting layer (5) Organic protective layer (21) Pregroove

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // C09B 23/00 B41M 5/26 Y (72) Inventor Mamoru Usami 1-13-1 Nihombashi, Chuo-ku, Tokyo T F-term in DK Corporation (reference) 2H111 EA03 EA12 EA25 EA43 FA12 FB43 FB63 4H056 CA01 CC02 CC08 CE03 DD03 FA06 5D029 JA04 JB47 JC02 JC17 5D090 AA01 BB03 CC06 CC20 DD03 KK07 5D121 AA01 EE22 EE28 GG

Claims (8)

[Claims] 1. An optical recording medium comprising a recording layer containing a cyanine dye organic dye on a light-transmitting substrate and a reflection layer in this order, wherein a signal corresponding to information to be recorded is transmitted from the substrate side to 770 ~
Writing and recording information by irradiating a recording laser beam having a wavelength of 800 nm, and after recording, at least a part of the cyanine-based organic dye in the recording layer is treated with light energy so that an unrecorded portion has a thickness of 750 to 830 nm. The difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 20% or less. 2. The difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 750 to 830 nm of the unrecorded portion before the treatment with light energy is 50% or more.
The optical recording medium according to claim 1. 3. The optical recording medium according to claim 1, wherein the cyanine-based organic dye includes a pentamethine cyanine dye. 4. The light according to claim 1, wherein the recording layer contains, as necessary, 10% by weight or less of a singlet oxygen quencher based on the total amount of the organic dye. recoding media. 5. An optical recording medium having a recording layer containing a cyanine-based organic dye and a reflective layer on a light-transmitting substrate in this order,
Signals corresponding to information to be recorded are transmitted from the
By writing and recording information by irradiating a recording laser beam having a wavelength of 800 nm, after recording, at least a part of the cyanine organic dye in the recording layer is irradiated with light energy to 750 to 8 in an unrecorded portion.
Fading is performed so that the difference between the maximum value and the minimum value of the reflectance from the substrate side in a range of 30 nm is 20% or less, and a reproduction laser beam having a wavelength of 750 to 830 nm is applied to the optical recording medium after the fading process. An optical recording / reproducing method which includes reading a recording signal by irradiating from a substrate side and reproducing information. 6. The optical recording medium according to claim 5, wherein the difference between the maximum value and the minimum value of the reflectance from the substrate side in the range of 750 to 830 nm of the unrecorded portion in the optical recording medium before the fading treatment is 50% or more. The optical recording / reproducing method according to the above. 7. The pentamethine cyanine dye is used as the cyanine-based organic dye.
3. The optical recording / reproducing method according to item 1. 8. The light according to claim 5, wherein the recording layer optionally contains a singlet oxygen quencher of 10% by weight or less based on the whole organic dye. Recording and playback method.