JPH10320829A - Optical recording medium and its recording and/or reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical recording medium and its recording and/or reproducing method capable of excellently recording and/or reproducing for a specified wavelength of recording light or moreover for the light of the short wavelength different from this in addition to this characteristic in the optical recording medium successively formed at least a recording layer, an intermediate layer and a reflecting layer containing the coloring matter absorbing the recording light on a transparent substrate. SOLUTION: The optical recording medium 1, wherein at least the recording layer 3, the intermediate layer 4, the reflecting layer 5 and a protecting layer 6 if necessary containing the coloring matter absorbing the recording light are successively formed on the transparent substrate 2, recording and reproducing are allowed using the recording light of the wavelength λ and moreover α, β obtained from α=n3/k3, β=n4/k3 satisfies either β<=0.8α. or β>=1.25α, when the refraction index of the recording layer 3 in the wavelength λ is meant by n3, the extinction coefficient is meant by k3 and the refraction index of the intermediate layer 4 is meant by n4, is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and a method for recording and / or reproducing the same, especially a recording layer containing at least a dye absorbing recording light on a transparent substrate,
An optical recording medium in which an intermediate layer and a reflective layer are sequentially formed, and an optical recording medium capable of performing good recording and / or reproduction with respect to recording light having a specific wavelength, or a recording medium having a specific wavelength. The present invention relates to an optical recording medium capable of performing good recording and / or reproduction with respect to light, and capable of performing good recording and / or reproduction even with light having a different short wavelength, and a recording and / or reproducing method thereof.

[0002]

2. Description of the Related Art At present, read-only optical disks (hereinafter referred to as CDs and CD-ROMs) are widely used as optical recording media for reproducing information by laser light, for music reproduction and information terminals. This optical recording medium records information by providing an uneven pit array on one side of a transparent substrate having a thickness of 1.2 mm, and providing a reflective film of aluminum, gold, or the like thereon by a sputtering method or a vapor deposition method. Generally, it has a configuration in which a protective film is coated thereon. Then, this optical recording medium shows a change in the reflectance corresponding to the unevenness of the information pit recorded in advance when a semiconductor laser beam having a wavelength of 780 nm is incident through a transparent substrate and reflected by a reflection film. It reads and reproduces information recorded in advance. However, CDs and CD-ROMs are read-only media and do not have an editing function.

[0003] Therefore, write-once optical disks (hereinafter, referred to as CD-R) and rewritable optical disks (hereinafter, referred to as phase change type) which can be recorded only once are developed and put into practical use as recordable optical recording media. Such recordable optical discs have a reproduction function of CD or CD-ROM.
Compatible with ROM. Due to this playback compatibility, C
An information terminal device equipped with a D-ROM playback device can reliably play back recorded CD-R information. By adding a CD-R recording function to a CD-ROM device, it is possible to provide a CD-ROM device with the same capacity as a CD-ROM.
It is possible to use an information recording device of 0 Mbytes. Therefore, in recent years, in particular, CD-Rs have become widespread as information recording media. Further, when editing the information content of the CD-ROM, it is necessary to test-produce the CD-ROM. Even in such an authoring business, which is an editing business, a CD-R compatible with a CD-ROM playback function is not compatible with a CD-ROM.
It is an indispensable key device in the trial operation of ROM.

As the CD-R, those in which a chalcogenite-based compound such as Te, a rare earth metal compound, a porphyrin-based, a cyanine-based, and a naphthalocyanine-based organic compound are applied to a recording layer have been put to practical use. Recently, especially CD-R
Regarding, from the viewpoint of price, pollution-free properties, and complete compatibility of the reproduction characteristics with the above-mentioned CD-ROM, those using an organic compound such as a dye for the recording layer have become mainstream. High-power laser light is made incident according to the information signal, and the incident laser light is absorbed by the organic compound in the recording layer and converted into heat, causing a chemical change and a geometric shape change in the recording layer. To add information. Further, the information recorded in this manner is irradiated with a relatively low-power laser beam of a fixed value or less to recognize a change in the reflectance, specifically, a change in the amount of reflected light, and reproduce the recorded information. Will be performed. Examples of the organic compound used in such a recording layer include, for example, Japanese Patent Application Laid-Open No. 1-145188 for a porphyrin compound, and especially Japanese Patent Application Laid-Open No. 3-1 for a tetraazaporphyrin compound.
No. 3,382, JP-A-3-13384, JP-A-7-27
No. 6804 and the like. Further, phthalocyanine compounds are disclosed in JP-A-2-276676 and the like.
For naphthalocyanine compounds, see Japanese Patent Publication No. 4-209
No. 45 is disclosed.

On the other hand, the development of next-generation high-density optical recording media is actively progressing. A major feature of this next-generation high-density optical recording medium is that the wavelength of laser light is 620 to 690 nm.
The recording density is improved by shortening the wavelength and shortening the interval and length of the track pitch, and 3 to 10 G, which is 5 to 10 times larger than the recording capacity of the current CD-ROM of 650 Mbytes.
It enables handling of digital data of bytes. However, according to the current standard, this high-density optical recording medium is also read-only and has no editing function. For this reason, a recordable high-density write-once optical disc having an editing function has been energetically studied. In particular, it is desired to use an organic material for the recording layer like a CD-R. As a specific disclosure, a recording medium in which the light absorption property of a cyanine compound is shifted to a short wavelength is disclosed in JP-A-6-199045, and a recording medium in which an indoline imine dye is applied to a recording layer is further disclosed. The medium is disclosed in JP-A-5-305771 and JP-A-4-252.
272, etc. However, in these patent information, there are some technical problems in realizing a high-density optical recording medium having the same degree of perfection as CD-R.

While such a high-density optical recording medium has been developed, a CD-R (hereinafter referred to as a CD-R) which can be reproduced by a high-density recording-compatible player has been developed because of compatibility with a conventional system which has already been widely used. , CD-R2). Conventional CDs and CD-ROMs have a small wavelength dependence of reflectivity, and can be reproduced by a player that supports high-density recording. However, the conventional CD-R having a dye in the recording layer has a large wavelength dependence of the optical constant of the dye, and hence a large wavelength dependency of the reflectance.
It is difficult to achieve both recording and playback on a DR, CD, and CD-ROM player and playback on a player supporting high-density recording. Recently, this problem has also been actively addressed.
No. 72, JP-A-8-263873, JP-A-8-238873
In JP-A-31010, by setting the refractive index, the extinction coefficient, and the film thickness of the light absorbing layer to appropriate ranges according to different wavelengths, the reflectance of the near-infrared laser having a wavelength of 770 to 830 nm becomes 65. % Or more, and a wavelength of 620 to 690 nm
An optical recording medium CD-R2 satisfying a reflectance of 15% or more with a red laser has been proposed. However, there are still some technical issues in these patent information.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems, that is, at least a recording layer containing a dye absorbing recording light on a transparent substrate,
In an optical recording medium in which an intermediate layer and a reflective layer are sequentially formed,
An optical recording medium capable of good recording and reproduction for recording light of a specific wavelength, or a short wavelength different from that for recording and reproduction of good recording light of a specific wavelength. Optical recording medium capable of good recording and reproduction or reproduction with respect to light, and recording and / or reproduction thereof
Or to provide a reproduction method.

[0008]

The present inventor has made intensive studies to solve the above-mentioned problems, and as a result, in order to solve the above-mentioned problems, it is very important to control the reflectance between the recording layer and the intermediate layer. , The refractive index n3 of the recording layer and the extinction coefficient k
3, and α = n3 / given by the refractive index n4 of the intermediate layer
It has been found that k3, β = n4 / k3 are very important parameters. For a recording light of a certain wavelength,
By setting α and β in a specific range, an optical recording medium capable of excellent recording and reproduction can be set, and α and β can be set in a specific range for light of two different wavelengths. By setting, an optical recording medium capable of good recording and reproduction was found, and the present invention was achieved.

That is, in the optical recording medium according to the present invention, at least a recording layer containing a dye that absorbs recording light, an intermediate layer, and a reflective layer are sequentially formed on a transparent substrate. Recording and reproduction are possible, and the refractive index of the recording layer at the wavelength λ is n3, and the extinction coefficient is k.
3. When the refractive index of the intermediate layer is n4, α = n3 /
α, β given by k3, β = n4 / k3, β ≦ 0.
An optical recording medium characterized by satisfying either 8α or β ≧ 1.25α, further capable of recording and reproduction using recording light having a wavelength λ, and having a wavelength shorter than the wavelength λ. Recording and reproduction or reproduction are possible using light of wavelength λ ′, and when the refractive index of the recording layer at wavelength λ is n3, the extinction coefficient is k3, and the refractive index of the intermediate layer is n4, α and β given by α = n3 / k3 and β = n4 / k3 are β ≦ 0.8α or β ≧ 1.25α
And the refractive index of the recording layer at wavelength λ 'is n3', the extinction coefficient is k3 ', and the refractive index of the intermediate layer is n4', α '= n3' / k
Α ′, β ′ given by 3 ′, β ′ = n4 ′ / k3 ′
Is an optical recording medium characterized by satisfying β ′ ≠ α ′. When α and β satisfy β ≦ 0.8α, α ≧ 1 and β ≦ 40, and when β ≧ 1.25α, α ≦ 40 and β ≧ 1. 770
830 nm, and the λ ′ is 620-690 nm.
a laser beam selected from the group consisting of
An optical recording medium as described above, which is a metal layer. Further, the present invention is an optical recording method using the above optical recording medium for recording with light of wavelength λ, and an optical recording / reproducing method for reproducing with light of wavelength λ or λ ′ after recording. Using the optical recording medium recorded with the light of λ, the wavelength λ or λ ′
This is an optical reproduction method for reproducing with the light.

The refractive index and the extinction coefficient according to the present invention correspond to the real part and the imaginary part of the complex refractive index, respectively.
The recording layer and the intermediate layer separately formed on the quartz substrate are determined based on the film thickness dependence of the reflectance and the transmittance.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The optical recording medium of the present invention will be specifically described below. FIG. 1 is an enlarged cross-sectional view of an optical recording medium according to the present invention. The optical recording medium 1 of the present invention comprises a transparent substrate 2
A recording layer 3 containing a dye that absorbs recording light, an intermediate layer 4, and a reflective layer 5 are formed in this order directly or via another layer, and more preferably, a protective layer 6 is formed.

The material of the transparent substrate 2 is basically required to be transparent at the wavelength of the recording and reproducing light, and more preferably has a low thermal conductivity. Specifically, for example, polycarbonate resin, acrylic resin, epoxy resin, glass, amorphous polyolefin and the like can be used. The substrate may be in a plate shape, a film shape, or a card shape, but is preferably a disk shape defined by an appropriate thickness and diameter with respect to a focal point of an optical system of a laser light used as a light source. It is more preferable that a guide groove is provided on one side, and it is preferable that the guide groove can be formed by cutting or injection molding.

The recording layer 3 has appropriate absorption and heat conversion efficiency with respect to the recording light, and imparts relatively strong energy of the recording light to physically and chemically decompose and degrade the recording light.
There is no particular limitation as long as it involves deformation. Specific examples include phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, detraazaporphyrin dyes, cyanine dyes, and azo dyes. Further, these may include a metal.

The recording layer 3 can be formed by using a spin coating method, a vacuum evaporation method, a sputtering method, or the like. In the spin coating method, a recording layer is formed by dissolving an organic dye in a solvent and dropping the dye solution while rotating the transparent substrate 2.
The dye solution is preferably adjusted to a dye concentration of 0.5 to 5% by weight. The solvent for preparing the dye solution can be used as long as it dissolves the dye and is harmless to the transparent substrate 2. Solvents include methyl alcohol, ethanol, propanol, butanol, tetrafluoro alcohol, acetone methyl ethyl ketone, diethyl ether, dipropyl ether, dibutyl ether, tetrahydrofuran, dioxane, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, benzene, toluene, xylene , Naphthalene,
Hexane, cyclohexane, methyl chloride, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, 2-methoxyethanol, 2-ethoxyethanol, 2-isopropoxyethanol, acetonitrile, triethylamine, dipropylamine, dimethylformamide, etc. . The solvent is determined in consideration of dye solubility, workability, influence on the substrate, and economic efficiency.

When a dye solution is prepared by dissolving a dye in an organic solvent, a light stabilizer and an antioxidant may be contained. As light stabilizers, metal complexes and diimonium salts that are singlet oxygen quencher, hindered amine compounds, benzotriazole compounds as ultraviolet absorbers,
Benzophenone compound, as antioxidant, phenolic antioxidant as primary antioxidant, amine antioxidant, secondary antioxidant as organic sulfur secondary antioxidant, phosphorus secondary antioxidant And the like. These light stabilizers and antioxidants may be used alone or in combination. The amount of the additive is preferably about 0.1 to 200 parts based on 100 parts by weight of the dye.

Further, a resin may be added to the dye solution as a binder. These resins are cellulose esters such as nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose myristate, cellulose palmitate, cellulose acetate / propionate, cellulose acetate / butyrate, methylcellulose, and the like. Ethyl cellulose, propyl cellulose, cellulose ethers such as butyl cellulose, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, vinyl resins such as polyvinyl pyrrolidone, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, Copolymer trees such as styrene-butadiene-acrylonitrile copolymer and vinyl chloride-vinyl acetate copolymer , Polymethyl methacrylate, polymethyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, acrylic resins such as polyacrylonitrile, polyesters such as polyethylene terephthalate, poly (4,4-isopropylidene diphenylene-co- 1,4-cyclohexylene dimethylene carbonate and poly (ethylenedioxy-
3,3-phenylene thiocarbonate), poly (4,4
-Isopropylidene diphenylene carbonate-co-terephthalate), poly (4,4-isopropylidene diphenylene carbonate), poly (4,4-sec-butylidene diphenylene carbonate), poly (4,4-isopropylidene diphenylene carbonate) −Block−
Polyacrylate resins such as oxyethylene), polyamides, epoxy resins, phenolic resins, and polyolefins such as polyethylene, polypropylene, and chlorinated polyethylene can be used. These resins can be added in the range of 1 to 1000 parts per 100 parts by weight of the dye.

In order to form the recording layer 3 by a spin coating method, a desired film thickness is adjusted by the dye concentration, the number of rotations, and the rotation time. When the recording layer 3 is formed by a method such as vapor deposition, it is desirable that the recording layer 3 is vapor deposited at a degree of vacuum of 10 −2 Pa or less. Further, the recording layer 3 can be formed by simultaneously vapor-depositing a vaporizable light stabilizer, an antioxidant and the like. In this case, the light stabilizer, antioxidant and the like are selected from the compounds described above. In the vapor deposition, the recording layer pigment and the additive may be mixed in a predetermined amount and vapor-deposited by one heat source, or the additive and the pigment may be vapor-deposited by separate heat sources.

The intermediate layer 4 preferably has a smaller extinction coefficient than that of the recording layer 3, but does not necessarily have to have an extinction coefficient of zero. Specifically, organic materials such as phenolic resins, vinyl alcohol resins, butyral resins, polyimide resins, acrylic resins, silicone resins and copolymer resins thereof, and oxides such as silicon, titanium and zirconium. , Nitride, MgF ₂ , ZnS and other inorganic materials.

According to the study of the present inventor, in order to maximize the effect of the intermediate layer 4, the refractive index n 3, the extinction coefficient k 3 of the recording layer 3 at the recording wavelength λ, and the refractive index of the intermediate layer 4 parameter given by n4, α = n3 / k3, β
= N4 / k3 control is very important, β ≦ 0.8α
Or β ≧ 1.25α, and more preferably, when β ≦ 0.8α, α ≧ 1 and β ≦ 40, and when β ≧ 1.25α, α
More preferably, ≦ 40 and β ≧ 1. further,
In order to be able to perform recording, reproduction or reproduction using light having a wavelength λ ′ shorter than the recording wavelength λ, the refractive index of the recording layer 3 at the wavelength λ ′ is n3 ′, the extinction coefficient is k3 ′, and the intermediate extinction coefficient is k3 ′. Assuming that the refractive index of the layer 4 is n4 ', α' = n3 '/ k
Α ′, β ′ given by 3 ′, β ′ = n4 ′ / k3 ′
Preferably satisfies β ′ ≠ α ′.

When β> 0.8α or β <1.25α,
Even if the intermediate layer 4 is provided, the effect is hardly seen, and problems such as a decrease in reflectivity and a disturbance in a reproduced signal waveform are not preferable. When β ≦ 0.8α is satisfied, α <1 or β> 40 or β ≧ 1.25α
When α> 40 or β <1, the effect of the intermediate layer 4 is slightly reduced, but the effect is extremely small, which again causes problems such as a decrease in reflectivity and disturbance of a reproduced signal, which is not preferable. .

When recording and reproduction or reproduction is performed using light having a wavelength λ ′ shorter than the wavelength λ, α ′ and β ′
Is somewhat relaxed, as long as α ′ ≠ β ′. α '
When β = β ′, the effect of the intermediate layer 4 is scarcely observed, which causes problems such as a decrease in reflectivity and a disturbance in the reproduced signal waveform, which is not preferable.

The reflective layer 5 is made of a material having a high reflectance with respect to the wavelength of the used light source. The material used is preferably a metal,
Aluminum, silver, gold, iron, nickel, cobalt,
Tin, zinc, copper and the like are preferable, and these can be used alone or as an alloy. These reflective layers are formed to a thickness of about 10 to 200 nm by a sputtering method or the like.

The protective layer 6 is provided for protecting the recording layer 3 or the reflective layer 5 from scratches and stains and for preservation stability. As the inorganic material, SiO or SiO ₂ can be used. Organic materials include polymethyl acrylate, polycarbonate, epoxy resin, polystyrene, polyester resin,
Thermosoftening and heat melting resins such as vinyl resin, cellulose, aliphatic hydrocarbon resin, aromatic hydrocarbon resin, natural rubber, wax, alkyd resin, drying oil and rosin can also be used. Further, a flame retardant, a stabilizer, an antistatic agent and the like can be added to the protective layer 6 as needed. Alternatively, a resin substrate may be bonded with an adhesive. With this configuration, it is possible to realize a write-once optical recording having high reflectance and excellent signal output characteristics without readout destruction due to repeated reproduction.

Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto. (Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIG. The substrate 2 was a disc-shaped transparent substrate made of polycarbonate, which was injection molded into a shape having a thickness of 1.2 mm, a pitch of 1.6 μm, a width of 0.5 μm, and a depth of 50 nm. On this substrate, tin chloride phthalocyanine represented by the formula (Formula 1) was formed as a recording layer 3 by a vacuum evaporation method so as to have an average film thickness of 50 nm, and polycarbonate was formed thereon as an intermediate layer 4 by vacuum evaporation. 100, 120, 140, 160, 180, 2
A film was formed to a thickness of 00 nm. Next, a reflective layer 5 is formed on the intermediate layer 4.
A gold thin film having a thickness of 100 nm was formed by sputtering. Further, an ultraviolet curable resin was applied on the reflective layer 5 by a spin coating method, and was cured by irradiating ultraviolet rays, and this was used as a protective layer 6 to produce the optical recording medium 1.

[0025]

Embedded image

The optical constant of the recording layer 3 is 780 n
m, the refractive index n3 = 4.24 and the extinction coefficient k3 = 0.
79, refractive index n3 = 1.65 at a wavelength of 680 nm,
Extinction coefficient k3 = 1.47, refractive index n3 = 1.28 at 650 nm wavelength, extinction coefficient k3 = 1.19, wavelength 63
At 5 nm, the refractive index n3 = 0.99, the extinction coefficient k3 =
0.90, the optical constant of the intermediate layer 4 is 780, 68
Refractive index n4 = 1.5 at 0, 650 and 635 nm
9, the extinction coefficient k4 = 0, so α = 5.37, β = 2.01 at a wavelength of 780 nm, α = 1.12, β = 1.08 at a wavelength of 680 nm, α = 1.08 at a wavelength of 650 nm, β = 1.34, α = 1.10 and β = 1.77 at a wavelength of 635 nm.

780 nm incident on the substrate surface of this optical recording medium
Was 65 to 80%. FIG. 2 shows a plot of the reflectance at 780 nm with respect to the thickness of the intermediate layer. In this optical recording medium, the extinction coefficient of the recording layer was 0.79.
It can be seen that despite having a very large value, it has an appropriate reflectance over a wide range of 100 to 200 nm. In addition, since the thickness gradually changes with respect to the thickness of the intermediate layer, it is understood that the process management of the film formation is relatively easy.

All these optical recording media have a wavelength of 780
nm, using a semiconductor laser with a linear speed of 1.2 m / sec.
c, An EFM modulated signal was recorded with a recording laser power of 8 mW. Then, this recorded signal was reproduced with a 780 nm semiconductor laser of 0.5 mW. In each case, the reflectance was reduced in the recording portion, the modulation was sufficiently large, the jitter was good, and almost no distortion was observed in the waveform of the recording / reproducing signal. Further, the wavelength 770 nm to 830
The same tendency was confirmed when recording and reproduction were performed using a semiconductor laser of nm while maintaining the optical characteristics of the intermediate layer described above.

The recorded signals are converted to a wavelength 68
As a result of reproducing with an output of a semiconductor laser of 0.5 mW of 0, 650, and 635 nm, the reflectance was 40% or more, and the jitter was good. This tendency was observed at wavelengths of 620 nm to 690 nm.
A similar tendency was confirmed by maintaining the above-mentioned optical properties of the intermediate layer in the range of nm.

Comparative Example 1 A semiconductor laser having a wavelength of 680, 650, or 635 nm was used as recording light for an optical recording medium in which the thickness of the intermediate layer in Example 1 was 160, 180, or 200 nm. The reflectance at a wavelength of 680 nm is
When the thickness of the intermediate layer was 160 nm, it was smaller than 65%, when the thickness of the intermediate layer was 180 nm, it was larger than 80%, and when the thickness of the intermediate layer was 200 nm, it was smaller than 65%.
Similarly, the reflectance at a wavelength of 650 nm is smaller than 65% when the thickness of the intermediate layer is 160 nm, larger than 80% when the thickness of the intermediate layer is 180 nm, and the reflectance of the intermediate layer is 2%.
It was smaller than 65% at 00 nm. It is apparent that the thickness dependency of the intermediate layer is large. It was also found that when the reflectance at the recording wavelength was greater than 80%, the absorption was reduced and recording became difficult.

On the other hand, the reflectance at a wavelength of 635 nm is
It was found that the film thickness of the intermediate layer was 65 to 80% when the thickness was 160 to 200 nm, that the intermediate layer had an appropriate reflectance, and that good recording could be performed.

Further, the wavelength range 77 of the recording light and the reproduction light
When at least one of the optical characteristics of the intermediate layer was not maintained at 0 nm to 830 nm, good reproduction results could not be obtained. This is because the wavelength of the reproduction light is 620 nm to 6 nm.
The same was true for 90 nm.

(Example 2) As an intermediate layer, a polysiloxane resin was spin-coated to a thickness of 160, 180 or
An optical recording medium was produced in the same manner as in Example 1 except that the film was formed to have a thickness of 200 nm. The optical constant of this intermediate layer is 78
At 0, 680, 650 and 635 nm, the refractive index n4 =
1.40, extinction coefficient k4 = 0, therefore wavelength 780 nm
Α = 5.37, β = 1.77, wavelength 680 nm
Α = 1.12, β = 0.95, wavelength 650 nm
Α = 1.08, β = 1.18, wavelength 635 nm
In this case, α = 1.10 and β = 1.56.

780 of the optical recording medium incident on the substrate surface
The reflectivity in nm was all 65-80%. EFM modulated signals were recorded on all of these optical recording media using a semiconductor laser having a wavelength of 780 nm at a linear velocity of 1.2 m / sec and a recording laser power of 8 mW. Then, this recorded signal was reproduced with a 780 nm semiconductor laser of 0.5 mW. In each case, the reflectance was reduced in the recording portion, the modulation was sufficiently large, the jitter was good, and almost no distortion was observed in the waveform of the recording / reproducing signal. Further, when recording and reproduction were performed using a semiconductor laser having a wavelength of 770 nm to 830 nm while maintaining the above-mentioned optical characteristics of the intermediate layer, the same tendency was confirmed.

The recorded signals are converted to a wavelength 68
As a result of reproducing with an output of a semiconductor laser of 0.5 mW of 0, 650, and 635 nm, the reflectance was 40% or more, and the jitter was good. This tendency was observed at wavelengths of 620 nm to 690 nm.
A similar tendency was confirmed by maintaining the above-mentioned optical properties of the intermediate layer in the range of nm.

(Comparative Example 2) The reflectance of the optical recording medium of Example 2 at a wavelength of 700 nm upon incidence on the substrate was examined. The optical constant of this recording layer is a refractive index n at a wavelength of 700 nm.
3 ′ = 1.40, extinction coefficient k3 ′ = 1.62, and the optical constant of this intermediate layer is a refractive index n4 ′ =
1.40, extinction coefficient k4 '= 0, thus 700n wavelength
At m, α ′ = 0.86 and β ′ = 0.86. In all the optical recording media of Example 2, the reflectance was 40%.
It has been found that reproduction becomes difficult when α ′ = β ′.

Further, the wavelength range 77 of the recording light and the reproducing light
When at least one of 0 nm to 830 nm and the above-described optical characteristics of the intermediate layer was not maintained, a poor reproduction result was similarly obtained. This is because the wavelength of the reproduction light is 620 nm or more.
The same was true for 690 nm.

(Example 3) An optical recording medium was produced in the same manner as in Example 1 except that ZrO ₂ was formed into a film with a thickness of 80, 100, or 120 nm by vacuum evaporation as an intermediate layer. The optical constants of this intermediate layer are 780, 680, 65
At 635 nm, the refractive index n4 = 2.21 and the extinction coefficient k4 = 0, so that at the wavelength of 780 nm, α = 5.
37, β = 2.80, α = 1.80 at a wavelength of 680 nm.
12, β = 1.50, α = 1.
08, β = 1.86, α = 1.6 at a wavelength of 635 nm.
10, β = 2.46.

780 of these optical recording media incident on the substrate surface
The reflectivity in nm was all 65-80%. EFM modulated signals were recorded on all of these optical recording media using a semiconductor laser having a wavelength of 780 nm at a linear velocity of 1.2 m / sec and a recording laser power of 10 mW. Then, the recorded signal is converted into a 780 nm semiconductor laser 0.5 mW.
Played with. In each case, the reflectance was reduced in the recording portion, the modulation was sufficiently large, the jitter was good, and almost no distortion was observed in the waveform of the recording / reproducing signal. Further, when recording and reproduction were performed using a semiconductor laser having a wavelength of 770 nm to 830 nm while maintaining the above-mentioned optical characteristics of the intermediate layer, the same tendency was confirmed.

The recorded signals are converted to a wavelength 68
As a result of reproducing with an output of a semiconductor laser of 0.5 mW of 0, 650, and 635 nm, the reflectance was 40% or more, and the jitter was good. This tendency was observed at wavelengths of 620 nm to 690 nm.
A similar tendency was confirmed by maintaining the above-mentioned optical properties of the intermediate layer in the range of nm.

Comparative Example 3 The reflectance of the optical recording medium of Example 3 at wavelengths of 740 and 850 nm incident on the substrate was examined. The optical constants of this recording layer are: refractive index n3 = 2.96, extinction coefficient k3 = 3.24 at wavelength 740 nm, refractive index n3 = 3.65, extinction coefficient k at wavelength 850 nm.
3 = 0.05, and the optical constant of this intermediate layer is 740, 8
Refractive index n4 = 2.21 at 50 nm, extinction coefficient k4
= 0, thus α = 0.91 at a wavelength of 740 nm,
β = 0.68, α = 73.0 at a wavelength of 850 nm,
β = 44.2. In all the optical recording media of Example 3, the reflectance was less than 40% at the wavelength of 740 nm, and was greater than 80% at the wavelength of 850 nm. Thus, when α <1, the reflectance decreases, and β> 4
It has been found that when the value is 0, the absorption decreases, and good recording becomes difficult.

The wavelength range 77 of the recording light and the reproducing light is
When at least one of 0 nm to 830 nm and the above-described optical characteristics of the intermediate layer was not maintained, a poor reproduction result was similarly obtained. This is because the wavelength of the reproduction light is 620 nm or more.
The same was true for 690 nm.

[0043]

According to the present invention, as is apparent from the above Examples and Comparative Examples, at least a recording layer containing a dye absorbing a recording light, an intermediate layer, and a reflective layer are sequentially formed on a transparent substrate. Α = n3 / k3 given by the refractive index n3 of the recording layer, the extinction coefficient k3, and the refractive index n4 of the intermediate layer, for the recording light of a specific wavelength in the optical recording medium.
By setting β = n4 / k3 to a specific range,
An optical recording medium on which good recording and reproduction can be performed can be provided. Also, for recording light of a specific wavelength,
Α = n3 / k3, β = n4 / k3 given by the refractive index n3 of the recording layer, the extinction coefficient k3, and the refractive index n4 of the intermediate layer.
Is set to a specific range, good recording and reproduction can be performed, and the refractive index n3 'of the recording layer, the extinction coefficient k3', and the intermediate layer Α ′ = n3 ′ / k given by refractive index n4 ′
By setting 3 ′ and β ′ = n4 ′ / k3 ′ in a specific range, it is possible to provide an optical recording medium capable of excellent recording and / or reproduction, and a recording and / or reproducing method thereof.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a write-once optical recording medium used in the present invention.

FIG. 2 is a characteristic diagram showing an example of the relationship between the thickness of an intermediate layer and the reflectance in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical recording medium 2 Transparent substrate 3 Recording layer 4 Intermediate layer 5 Reflective layer 6 Protective layer

Claims (13)

[Claims] 1. An optical recording medium in which a recording layer containing a dye that absorbs recording light, an intermediate layer, and a reflective layer are sequentially formed on a transparent substrate, at least using a recording light having a wavelength λ. Alternatively, when reproduction is possible and the refractive index of the recording layer at a wavelength λ is n3, the extinction coefficient is k3, and the refractive index of the intermediate layer is n4, α = n3 / k3,
An optical recording medium characterized in that α and β given by β = n4 / k3 satisfy either β ≦ 0.8α or β ≧ 1.25α. 2. The optical recording medium according to claim 1, wherein said λ is 770 to 830 nm. 3. When α and β satisfy β ≦ 0.8α, α ≧ 1 and β ≦ 40, and when β and 1.25α, α ≦ 40 and β ≧ 1. The optical recording medium according to claim 1, wherein: 4. An optical recording medium in which at least a recording layer containing a dye absorbing recording light, an intermediate layer, and a reflection layer are sequentially formed on a transparent substrate, recording and / or using a recording light having a wavelength λ. Or recording and reproduction or reproduction using light having a wavelength λ ′ shorter than the wavelength λ, and the refractive index of the recording layer at the wavelength λ is n3, and the extinction coefficient is Is k3 and the refractive index of the intermediate layer is n4, α and β given by α = n3 / k3 and β = n4 / k3 are β ≦ 0.8α or β ≧ 1.25α
And at the wavelength λ ′, the refractive index of the recording layer is n3 ′, the extinction coefficient is k3 ′, and the refractive index of the intermediate layer is n4 ′, α ′ = n3 ′ / k
Α ′, β ′ given by 3 ′, β ′ = n4 ′ / k3 ′
Satisfies β ′ ≠ α ′. 5. The optical recording medium according to claim 4, wherein said λ is a laser beam selected from 770 to 830 nm, and said λ ′ is a laser beam selected from 620 to 690 nm. 6. When α and β satisfy β ≦ 0.8α, α ≧ 1 and β ≦ 40, and when β ≧ 1.25α, α ≦ 40 and β ≧ 1. The optical recording medium according to claim 4 or 5, wherein 7. The laser beam according to claim 1, wherein said λ is a laser beam selected from 770 to 830 nm, and said λ ′ is a laser beam selected from 620 to 690 nm.
7. The optical recording medium according to any one of 6. 8. An optical recording method using the optical recording medium according to claim 1 for recording with light having a wavelength of λ. 9. In addition to the optical recording method according to claim 8,
An optical recording / reproducing method in which reproduction is performed with light having a wavelength λ after recording. 10. The optical recording medium according to claim 1, wherein the optical recording medium is recorded with light having a wavelength of λ and is reproduced with light having a wavelength of λ. 11. An optical recording method for performing recording with light having a wavelength of λ using the optical recording medium according to claim 4. 12. An optical recording / reproducing method in which, in addition to the optical recording method according to claim 11, reproduction is further performed with light having a wavelength λ ′ after recording. 13. An optical recording medium according to claim 4, wherein said optical recording medium is recorded with light having a wavelength of λ, and is reproduced with light having a wavelength of λ ′.