JPH0954979A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable recording and reproducing with light of a specified wavelength and to enable reproducing with the light of wavelength different from the recording wavelength by optimizing the optical const. and film thickness of a recording layer having grooves and an optical interference layer of an optical recording medium. SOLUTION: A light-absorbing layer containing a phthalocyanine dye or the like having absorbance for wavelength λ1 selected from 770-830nm wavelength range of laser light is formed on a transparent substrate. A light- reflecting layer is formed directly on this absorbing layer or through an optical interference layer. Reflectance R1 , R2 in the nonrecorded part and recorded part, respectively, when recording is performed with wavelength λ1 through the substrate and reproducing is performed with light of wavelength λ1 , and reflectance R3 , R4 in the nonrecorded part and recorded part, respectively, when reproducing is performed with light of wavelength λ2 selected from 630-690nm region satisfy R1 >=65%, R1 >R2 , R3 <=20%, and R3 <R4 . By this constitution, the obtd. medium enables recording and reproducing with light of wavelength λ1 and reproducing with light of wavelength λ2 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, and more particularly to an optical recording medium satisfying the Orange Book standard which is a standard for recordable compact discs (CD-R) and capable of reproducing at two different wavelengths.

[0002]

2. Description of the Related Art Conventionally, a CD-R (CD-R) has been used as a write-once type optical recording medium satisfying the CD (Compact Disc) standard.
The ECORDABLE) has been actively developed, and has already been put to practical use and provided to the market. This CD-R has a structure in which an organic dye recording layer, a metal reflection layer, and a protective layer are laminated on a transparent substrate, and the organic dye recording layer is changed by laser light emitted from the transparent substrate side for information. To record. The reproduction of this recording is generally performed in a large amount due to the high reflectance and contrast due to the metal reflective layer.
It can be read by the D player.

However, the conventional CD-R is defined in the so-called Orange Book standard on the assumption that recording and reproducing are performed by using a near infrared semiconductor laser having a wavelength of around 780 nm. By the way, there is an increasing demand for recording large-capacity information as typified by digital moving images without changing the size of the current medium. In response to this demand, the current 7
Red semiconductor lasers with wavelengths of 630 to 690 nm, which are shorter than 80 nm, have been developed. By using the short wavelength laser, the beam diameter of the laser light can be further narrowed down, and thus higher density recording and reproduction are possible. Is becoming.

However, a high-density player equipped with such a red semiconductor laser has a read-only medium having a high reflectance of 70% or more, which is formed by forming pits on a substrate at the time of molding and providing an aluminum reflection layer. It is designed to be playable, but of course conventional CDs, CD-ROMs and CD-Rs
From the viewpoint of compatibility, it is strongly desired that the recording medium software such as the above can be reproduced by the high density compatible player.

In this case, in the conventional CD or CD-ROM medium, the pits are formed on the substrate and the aluminum reflection layer is provided, so that the reflectance with respect to the red semiconductor laser light is 70.
Since it has more than 100%, it can be easily played back by a high-density compatible player. However, on the other hand, in the conventional CD-R medium, since the dye is necessarily used in the recording layer, the wavelength dependence of the optical characteristics of the dye is large, and as a result, the characteristics of the CD-R medium vary depending on the wavelength. There is a big problem that it changes greatly. For example, a conventional CD-R medium is 780 nm
Although it has a reflectance of 65% or more for the light in the vicinity and a large modulation degree, it has a short wavelength of 630 to 690 nm.
The reflectance with respect to the red light selected from is extremely low at 10% or less, and the degree of modulation is also small, and it ends up. As described above, if the reflectance is low and the degree of modulation is small, it becomes difficult to detect a signal, and even if it is possible to detect it, the error rate and the jitter are large, and it is not easy to reproduce it on a high-density compatible player.

Further, for example, Japanese Patent Laid-Open No. 3-162728 and Japanese Patent Laid-Open No. 5-67352 propose a medium having a structure similar to that of the present invention, but at a specific single wavelength, for example, 780 nm. For the purpose of increasing the reflectance or for expanding the range of the extinction coefficient of the organic dye layer used for the light absorption layer, the CD-R medium which can be reproduced at a wavelength shorter than the recording wavelength is No conditions have been defined, and according to the study of the present inventors, it is impossible to obtain a medium which has a large degree of modulation at the wavelength of the red semiconductor laser and can be reproduced by a high density player. Of.

[0007]

SUMMARY OF THE INVENTION The present invention has an object of solving the above problems and has a structure in which at least a light absorbing layer, and optionally a light interference layer and a light reflecting layer are laminated on a transparent substrate, By satisfying the Orange Book standard, which is a CD-R standard, it is possible to record and reproduce with a light having a wavelength selected from 770 to 830 nm, and to reproduce a signal well with a light having a wavelength selected from 630 to 690 nm. An object is to provide an optical recording medium that can be used.

[0008]

In order to solve the above-mentioned problems, the present inventors have proposed a light-absorbing layer containing a dye and a light-reflecting layer directly on the light-absorbing layer or through a light interference layer. In the recording medium, the optical constant and film thickness of the groove-shaped recording layer,
630-690n by optimizing the optical interference layer
It was found that even when the reflectance of the unrecorded portion is as low as less than 20% when read with light having a wavelength λ ₂ selected from m, the reflectance of the recorded portion is increased and a large modulation degree is obtained. We have completed an optical recording medium that can reproduce signals even with light of λ ₂ .

That is, according to the present invention, a light absorbing layer containing at least a dye that absorbs laser light is provided directly or through another layer on a transparent substrate having relatively shallow guide grooves. An optical recording medium having a light reflection layer laminated directly on or via an optical interference layer, comprising: 770-83
A recordable through the substrate at selected wavelengths lambda ₁ of light from 0 nm, the lambda ₁ of the record with light lambda ₁ when read through the substrate in the optical unrecorded area and reflectance of the recording portions each R ₁ when the R _2, and when read out through the substrate with light having a wavelength lambda ₂ selected from 630~690nm an unrecorded portion and a reflectance of the recording portion was _{R 3, R 4, R 1} ≧ 65
%, R ₁ > R ₂ , R ₃ ≦ 20%, R ₃ <R ₄ , and 7
An optical recording medium characterized by being capable of recording and reproducing with light having a wavelength selected from 70 to 830 nm and reproducing a signal even with light having a wavelength selected from 630 to 690 nm, and R ₁ and R ₂ , R ₃ and R ₄ are R ₂ /
The optical recording medium as described above, wherein R ₁ ≦ 0.5 and R ₃ / R ₄ ≦ 0.7, and the optical recording medium as described above, wherein an optical interference layer is laminated on a light absorbing layer. The optical recording medium described above, wherein the depth of the guide groove is 40 nm to 130 nm, and the depth of the guide groove is 50 nm to 100 n.
m is the optical recording medium described above, and the dye used in the light absorbing layer is a phthalocyanine dye, and the phthalocyanine dye is represented by the formula (1) The optical recording medium as described above, which is a dye represented by

[0010]

Embedded image [In the formula (1), M represents two hydrogen, or a metal, a metal oxide, or a metal halide, and Y ₁ , Y ₂ , Y ₃ ,
Y ₄ is oxygen or sulfur, and Z ₁ , Z ₂ , Z ₃ and Z ₄ are 4 to
An unsubstituted or substituted hydrocarbon group having 12 carbons is represented by X
₁ , X ₂ , X ₃ , X ₄ are halogens, l ₁ , l ₂ ,
l ₃ and l ₄ are 1 or 2, and m ₁ , m ₂ , m ₃ and m ₄ are 0
Represents an integer of 3; Further, the present invention provides a light absorbing layer containing a dye that absorbs at least laser light directly or through another layer on a transparent substrate, and light reflection on the light absorbing layer directly or through a light interference layer. It is made up of layers and has a reflectance of 77 measured through the substrate.
65 for light λ ₁ having a wavelength selected from 0 to 830 nm
% Or more, light having a wavelength selected from 630 to 690 nm λ ₂
Is a recording / reproducing method of recording and reproducing information on an optical recording medium of 20% or less by using a laser beam of wavelength λ ₁ , and further by using a laser beam of wavelength λ _2. It is a recording / reproducing method characterized by being possible.

[0011]

Embodiments of the present invention will be described below. In the optical recording medium of the present invention, 770 to 830
The reflectance R ₁ of the unrecorded portion from the substrate surface with respect to the light of the wavelength selected from nm is 65% or more, and 630 to 6
The reflectance R ₃ of the unrecorded portion from the substrate surface with respect to the light of the wavelength selected from 90 nm is 20% or less, the reflectance R ₁ is the reflectance R ₂ of the recording portion or more, and the reflection of the unrecorded portion is the same. The ratio R ₃ is preferably smaller than the reflectance R ₄ of the recording portion. To obtain practical signal characteristics, the contrast R
It is more preferable that ₂ / R ₁ ≦ 0.5 and R ₃ / R ₄ ≦ 0.7. CDs and CD-ROM players currently on the market are usually equipped with a semiconductor laser having a wavelength of about 780 nm, and are designed to be compatible with a medium having a reflectance of 65% or more. It can be played back on such a CD or CD-ROM player. On the other hand, there is currently no particular limitation on the reflectance of a medium that can be reproduced by a high-density compatible player equipped with a laser having a wavelength selected from 630 to 690 nm, but the player has a reflectance of 20% or more. Is practically preferable. In this case, the reflectance of 20% or more may be unrecorded or recorded. A normal CD-R must be in a so-called High to Low recording mode in which the reflectance of the recording portion becomes lower than the reflectance of the unrecorded portion when recording and reproducing with a laser beam having a wavelength selected from 770 to 830 nm. There is no particular limitation on the reproduction signal in the high density player, and even in the so-called Low to High recording mode in which the reflectance of the recorded portion is higher than that of the unrecorded portion, there is a certain difference in reflectance (so-called modulation degree), and tracking signals and If the polarity of the track cross signal is not reversed, it can be played on high density players.

Whether a high to low recording mode is set by a laser having a wavelength selected from 630 to 690 nm,
Although the condition regarding whether to enter the Low to High recording mode cannot be unconditionally specified, the condition of the present invention is Low.
Adopt a to High recording mode. The optical recording medium of the present invention comprises a transparent substrate on which a light absorbing layer containing at least a dye that absorbs laser light is provided, and a light reflecting layer is sequentially laminated on the light absorbing layer directly or via a light interference layer.

The transparent substrate used in the present invention is preferably a highly transparent material having a refractive index of about 1.4 to 1.6 with respect to light in order to record and read signals. Further, it is desirable that the light transmittance is 85% or more and the optical anisotropy is small. For example, a preferable example is a substrate using a thermoplastic resin such as an acrylic resin, a polycarbonate resin, a polyamide resin, a vinyl chloride resin, or a polyolefin resin. Among these, injection-molded resin substrates of acrylic resin, polycarbonate resin, and polyolefin resin are preferable from the viewpoint of mechanical strength of the substrate, easiness of giving a guide groove or reproduction-only signal, and economical efficiency, and particularly polycarbonate is preferable. A resin substrate is more desirable.

The shape of these transparent substrates may be plate-shaped, film-shaped, circular or card-shaped. The surfaces of these substrates may have guide grooves or pits indicating recording positions. Such guide grooves and pits are preferably provided at the time of molding the substrate, but can also be provided by applying an ultraviolet curable resin layer on the substrate, superposing it on a stamper, and performing ultraviolet exposure. When used as a normal CD, the thickness is about 1.2 mm and the diameter is 80 to 130 m.
It has a disk shape of about m and has a hole with a diameter of about 15 mm in the center. In the present invention, the depth of the guide groove is important in terms of the recording mode and the degree of modulation, and a relatively shallow groove having an appropriate depth is used. That is, the depth of the guide groove is preferably 40 nm to 130 nm, and preferably 50 nm to
100 nm is more preferable. When the groove depth is much smaller than 40 nm, signals such as radial contrast and push-pull become small, which makes stable recording difficult. On the other hand, when the groove depth became too deep and became 130 nm or more, the red laser wavelength could be stably reproduced in the Low to High mode.
This is not preferable because the degree of modulation in the High recording mode becomes small.

In the present invention, the light absorbing layer contains a dye, and the optical characteristics of this light absorbing layer are important in terms of reflectance, recording sensitivity, modulation degree, etc., and are 770 to 830 nm.
For light having a wavelength λ ₁ selected from among, the real part n ₁ of the complex refractive index of the light absorption layer is 1.8 or more, and the imaginary part k ₁ is 0.04.
It is preferable that the real part n ₂ and the imaginary part k ₂ of the complex index of refraction for light having a wavelength λ ₂ selected from ˜0.15 and 630 to 690 nm be 1.1 or more. n ₁ is 1.
When it is less than 8 or when k ₁ exceeds 0.15, the reflectance for light of λ ₁ is less than 65%, and k ₁ is 0.04.
If it is less than ₁ , the recording sensitivity to light of λ ₁ is lowered. Further, when n ₂ is less than 1.1, it is not preferable from the viewpoint of the reflectance and the degree of modulation with respect to the light of λ ₂ . As for the lower limit of k ₂ , it is desirable that recording can be performed with light of λ _2.
From the viewpoint of recording sensitivity to the light of _2, the value less than 0.04 is not preferable.

The dye used in the light-absorbing layer is a dye having a light-absorbing ability with respect to the laser light wavelength λ _1. Specifically, it is a phthalocyanine dye, a polymethine dye, a cyanine dye, an azo dye, or a naphthoquinone dye. Examples of the dye include phthalocyanine dyes, and more preferable are the phthalocyanine dyes represented by the formula (1) [Chemical Formula 3] in view of the optical characteristics of the light absorbing layer.

[0017]

Embedded image [In the formula (1), M represents two hydrogen, or a metal, a metal oxide, or a metal halide, and Y ₁ , Y ₂ , Y ₃ ,
Y ₄ is oxygen or sulfur, and Z ₁ , Z ₂ , Z ₃ and Z ₄ are 4 to
An unsubstituted or substituted hydrocarbon group having 12 carbons is represented by X
₁ , X ₂ , X ₃ , X ₄ are halogens, l ₁ , l ₂ ,
l ₃ and l ₄ are 1 or 2, and m ₁ , m ₂ , m ₃ and m ₄ are 0
Represents an integer of 3; Specific examples of preferable phthalocyanine dyes include dyes described in JP-A-3-62878, JP-A-3-141582, JP-A-3-215466, and the like. These are corresponding dicyano compounds and metal or metal compounds. Can be easily synthesized according to a known method.

When the light absorbing layer is prepared, a substituted phthalocyanine, a substituted naphthalocyanine, a substituted porphyrin dye, a cyanine dye, a dithiol metal complex and an anthraquinone having a structure other than those described above are further used to improve recording properties and optical properties. Other organic pigments such as pigments, organometallic complexes such as metallocenes, metal complexes of diketones, resins such as nitrocellulose, ethyl cellulose, acrylic resins, polystyrene resins, urethane resins and various additives such as leveling agents and defoaming agents. They can also be used in combination as long as the effects of the present invention are not impaired.

The light absorbing layer of the present invention can be formed by a method such as spin coating, dip coating, spray coating, roll coating, vapor deposition or the like, but from the viewpoint of ease of film formation, spin coating is used. The coating method is preferred. A solvent that does not damage the substrate when the dye is formed by spin coating, for example, hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, an aliphatic or alicyclic hydrocarbon solvent such as dimethylcyclohexane, diethyl. Ether-based solvents such as ether, dibutyl ether and diisopropyl ether, alcohol-based solvents such as methyl alcohol, ethyl alcohol, isopropyl alcohol, allyl alcohol and methyl cellosolve, halogen-based solvents such as carbon tetrachloride and tetrafluoropropanol are preferable. In addition to the above-mentioned solvents, for example, ester-based, ketone-based, aromatic-based or halogen-based solvents may be mixed and used within a range that does not damage the substrate.

In the present invention, the thickness of the light absorbing layer containing the dye is preferably in the range of 80 to 250 nm.
When the film thickness is made much smaller than 80 nm, the modulation degree (signal amplitude) becomes small and the CD standard is not satisfied. On the other hand, when the film thickness becomes much thicker than 250 nm, the reflectance decreases and C
Not only will the D standard not be satisfied, but the reproduction signal characteristics will also deteriorate.

In the present invention, the light absorbing layer is formed on the substrate. At this time, the solvent resistance of the substrate is improved between the substrate and the light absorbing layer, and recording characteristics and reflectance are improved. An intermediate layer may be provided for improvement. As a material used for the intermediate layer, a substance used for an optical interference layer, which will be described later, can be formed to a similar thickness and used.

In the present invention, it is also preferable to form a light interference layer on the light absorption layer. Examples of the light interference layer used include various polymers that are transparent in their thickness and similarly transparent inorganic compounds. The interference layer in the present invention has a function of compensating for the tendency that the degree of modulation when reading with light of long wavelength λ ₁ tends to be small when a relatively shallow guide groove is adopted. Specifically, inorganic compounds include oxides and nitrides of silicon, aluminum, titanium, thallium, zirconium, scandium, etc., such as silicon nitride, zinc, cadmium, tin sulfides, such as zinc sulfide, and the like. Examples of the polymer include polystyrene, polyvinylpyrrolidone, polyvinyl alcohol, methyl cellulose, nitrocellulose, and silicone resin.

As a method for producing the light interference layer, a known method such as a sputtering method or a vacuum film forming method such as a vacuum deposition method is used when it is formed of an inorganic compound, and when it is formed of a polymer, As with the light absorbing layer, methods such as spin coating, dip coating, spray coating and roll coating are used. The film thickness is usually 5 to 120 nm, and 20 to 7
About 0 nm is more preferable. As the material of the light reflecting layer used in the present invention, metals such as Au, Ag, Pt, Al and Cu which show high reflectance at the laser light wavelengths λ ₁ and λ ₂ and alloys of these metals are preferable. From the point of view, Au is most preferable. As a method for producing the light reflecting layer, a vacuum film forming method such as a vacuum vapor deposition method, a sputtering method, or an ion plating method is used. In the present invention, the thickness of the light reflection layer is usually 30 to 300 nm, more preferably about 50 to 150 nm.

In the present invention, a protective layer may be provided on the reflective layer to protect the recording layer or the reflective layer, a film or a resin substrate may be attached, or two media of the present invention may be attached. good. Materials used for the protective layer include acrylic resin, polycarbonate resin, ultraviolet curable resin,
Electron beam curing resin, polysiloxane resin, etc. are used,
A resin with excellent impact resistance is selected.

The protective layer is generally obtained by applying monomers and oligomers that can be polymerized to form polymers and then subjecting them to a crosslinking reaction. The material is not limited to an organic compound, and may be a mixed component of an organic compound and an inorganic compound, or an inorganic material may be formed by a method such as a sputtering method or a vacuum deposition method. In addition, when this is obtained as an organic polymer by a crosslinking reaction, a reactive acryloyl group in the molecule,
Alternatively, a method in which a small amount of a reaction initiator and a reaction catalyst are added to a mixture of monomers and oligomers of a polymerizable organic compound having one or more epoxy groups, a liquid mixture of these is applied, and the mixture is crosslinked by irradiation with ultraviolet rays or electron beams. But,
It is advantageous in terms of workability.

The protective layer is usually prepared by spin coating, dip coating, spray coating, roll coating,
The film can be formed by a means such as a screen printing method, but a spin coating method or a screen printing method is preferable from the viewpoint of easy film formation. The thickness of the protective layer is generally 0.1.
It is in the range of μm to 100 μm. In the present invention, the thickness of the protective layer is preferably 3 to 30 μm,
20 μm is more preferred. The optical recording medium of the present invention can be further printed with a label or the like on the protective layer.

As a method of recording information on the optical recording medium of the present invention, for example, an optical recording medium is used at a constant linear velocity (preferably 1
˜15 m / sec) while irradiating with laser light from the transparent substrate side to the bottom of the guide groove to form a reproduction pit in the guide groove-shaped light absorbing layer to record a signal. . As the signal, for example, EF of CD standard
The method of recording the M signal is preferable for obtaining the effect of the present invention. In addition, the pit means that the organic dye contained in the transparent substrate and / or the light absorption layer absorbs laser light and generates heat.
By melting, evaporation, sublimation, deformation or alteration,
Changes such as convex, corrugated, or concave between the transparent substrate and the light absorption layer, changes within the light absorption layer, changes between the light absorption layer and the light interference layer, etc. Of any of the following forms.

The optical recording medium of the present invention has a thickness of 770 to 830 nm.
It is possible to record and reproduce with a laser beam having a wavelength selected from. Particularly, laser light having a wavelength of about 780 nm is preferable. Further, it is possible to record with light having a wavelength selected from 630 to 690 nm. The laser output for recording varies depending on the rotation speed of the medium, but is usually 4 to 20 m.
It is about W. Further, the medium of the present invention has an unrecorded portion reflectance measured by incident light from the substrate side of 65% or more for light having a wavelength selected from 770 to 830 nm, and 630 to 690.
20% or less for light of a wavelength selected from nm,
The degree of modulation is also large enough. Therefore, a commercially available CD player or CD-R equipped with a laser with a wavelength of around 780 nm
It can be easily played back on an OM player or the like. Furthermore, for example, 635n selected from 630 to 690 nm
It can also be played on high-density players equipped with lasers with wavelengths around m, around 650 nm, and around 680 nm.

[0029]

According to the present inventors, the wavelength of 770 to 830 nm is optimized by optimizing the refractive index and film thickness of the light interference layer and the groove shape of the substrate for a specific light absorption layer.
A light having a reflectance of 65% or more with respect to a laser beam having a wavelength selected from, capable of recording / reproducing in accordance with the CD standard, and reproducible with a laser beam having a wavelength selected from 630 to 690 nm. A recording medium (CD-R) is realized. A medium with a particularly shallow guide groove, specifically, the depth of the guide groove is 40 nm to 130 nm, preferably 50 nm to 1
These compatible media can be realized by using an optical recording medium of 00 nm. Hereinafter, a more specific example of the embodiment of the present invention will be described with reference to examples. The technical scope of the present invention is not limited thereby.

[0030]

【Example】

[Example 1] A 3.5 wt% dimethylcyclohexane solution of Pd-phthalocyanine having one 1-isopropyl-isoamyloxy group at each α-position of each of four benzene rings constituting phthalocyanine was introduced into a guide groove (width: 0. 4μ
m, depth: 60 nm, pitch: 1.6 μm) polycarbonate resin substrate (diameter 120 mmφ, thickness 1.2)
mm disk) and spin coated at 2000 rpm.
It dried at 0 degreeC for 2 hours, and formed the light absorption layer with a film thickness of 100 nm. Si is used as an optical interference layer on this recording layer by reactive sputtering using a sputtering device manufactured by Shibaura Seisakusho.
_{A 3} N ₄ film having a thickness of 60 nm was formed. 780nm and 635n
The refractive index of this thin film measured at m was 1.84 for both wavelengths.

Next, a thickness of 1 was formed on the recording layer by using a Balzers sputtering device (CDI-900).
Au having a thickness of 00 nm was sputtered to form a reflective layer. Further, an ultraviolet curable resin SD-17 (manufactured by Dainippon Ink and Chemicals, Inc.) was spin-coated on the reflective layer, and then irradiated with ultraviolet rays to form a protective layer having a thickness of 6 μm to prepare an optical recording medium.

This optical recording medium is equipped with a 780 nm semiconductor laser head, a Philips writer (CDD
-521) was used to record the EFM signal at a linear velocity of 2.8 m / s and a laser power of 9.5 mW. After recording, the signal was reproduced using a commercially available CD player (YAMAHA CDX-1050, laser wavelength 786 nm) to evaluate the characteristics. As a result, the reflectance, the degree of modulation, the error rate,
Both the jitters satisfied the Orange Book standard, and the reproduced signal had almost no distortion, and very good results were obtained.

Next, the signal recorded on this medium was reproduced by the writer (CDD-521) using an optical disc evaluation device (DDU-1000) manufactured by Pulstec Industrial Co., Ltd. equipped with a 635 nm red semiconductor laser head, evaluated. As a result, the reflectivity of the unrecorded portion was 18%, the reflectivity of the longest pit portion was 32%, and there was almost no reproduced waveform distortion and the error rate was low, and very good reproduction was possible. In addition, this medium has a reflectance of 13% in the unrecorded portion even with light having a wavelength of 680 nm, and a reflectance of the longest pit is 23%.
%, Good reproduction without waveform distortion was possible. In addition, good recording was possible with this evaluation device having a laser beam having a wavelength of 680 nm.

Reference Example 1 The same medium as in Example 1 was prepared except that the Si ₃ N ₄ film was not formed. This medium was recorded and reproduced in the same manner as in Example 1 with a laser power of 9.0 mW. As a result of evaluation with a laser having a wavelength of 780 nm, the characteristics satisfied the Orange Book standard, and the reproduction could be performed for the time being. However, as a result of reproduction with an evaluation machine equipped with a 635 nm laser, the reflectance of the unrecorded portion was 18%, the reflectance of the longest pit was 21%, and the error rate was high, and the reproduction could not be performed very well.

[Example 2] After stacking the dye light-absorbing layer, polyvinylpyrrolidone was used as an interference layer by spin coating.
nm film is formed, the width of the guide groove of the substrate is 0.5 μm, and the depth is 9
The same medium as in Example 1 was prepared except that the thickness was 5 nm. Next, this medium was recorded and reproduced in the same manner as in Example 1 with a laser power of 10.0 mW. As a result of reproducing with a commercially available CD player, all the characteristics satisfied the Orange Book standard, and the error rate was low and the jitter was good. In addition, the reproduction result with the evaluation machine equipped with the 635 nm laser is that the reflectance of the unrecorded portion is 15%, the reflectance of the longest pit is 34%, there is almost no reproduced waveform distortion, and the error rate is very low. I was able to play. Furthermore, signals were reproduced from this medium by a high density player equipped with a 680 nm semiconductor laser. The reflectance of the unrecorded portion was 11%, the reflectance of the longest pit was 32%, there was no waveform distortion, and good reproduction was possible with a low error rate.

[Example 3] The depth of the guide groove of the substrate used in Example 1 was set to 70 nm, and a dye was prepared by introducing one octylthio group into each α-position of the four benzene rings constituting phthalocyanine. A medium was prepared and evaluated in the same manner as in Example 1 except that a phthalocyanine dye was used to form a 110 nm stacked layer, and ZnS was formed in the optical interference layer to a thickness of 30 nm by the RF sputtering method. When the refractive index of this thin film was measured, it was almost constant at 2.3 in the wavelength range of 800 nm to 600 nm.

This medium was evaluated in the same manner as in Example 1. When recorded at a recording power of 9.0 mW and reproduced by a commercially available CD player, good reproduction satisfying all CD standards was achieved. Next, when reproduced with a player having a laser wavelength of 635 nm, the reflectance of the unrecorded portion is 14
%, The reflectance of the longest pit was 23%, and good reproduction with a low error rate was achieved.

[0038]

According to the present invention, there is provided an optical recording medium comprising a substrate having a specific light absorption layer and a light reflection layer via a transparent light interference layer.
The reflectance of the unrecorded portion with respect to the light having the wavelength λ ₁ selected from 770 to 830 nm is 65% or more and 630 to 690 nm.
By setting the reflectance of the recording portion to be equal to or higher than the reflectance of the unrecorded portion when the reflectance of the light having the wavelength λ ₂ selected from the above is less than 20%, it is possible to record and reproduce with the light of λ _1.
There is provided an optical recording medium which can be reproduced by _two lights.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideki Umehara 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (8)

[Claims] 1. A light absorbing layer containing a dye that absorbs at least laser light is provided directly or through another layer on a transparent substrate having a relatively shallow guide groove, and the light absorbing layer is directly or directly provided on the light absorbing layer. An optical recording medium comprising a light reflection layer laminated via an optical interference layer, capable of recording with a light having a wavelength λ ₁ selected from 770 to 830 nm through a substrate, and recording with the light having the λ _{1 1} of the reflectivity each R ₁ of the unrecorded portion and the recorded portion when read through the substrate with light, and R _2, and unrecorded when read through the substrate with light of a selected wavelength lambda ₂ from 630~690nm when the parts and reflectance of the recording portion was _{R 3, R 4, R 1} ≧ 65%, R 1> R 2, R
₃ ≦ 20%, R ₃ <R ₄ , recording / reproducing with light having a wavelength selected from 770 to 830 nm, and 630 to 69
An optical recording medium capable of reproducing a signal even with light having a wavelength selected from 0 nm. 2. R ₁ , R ₂ , R ₃ and R ₄ are R ₂ / R
The optical recording medium according to claim 1, wherein ₁ ≤ 0.5 and R ₃ / R ₄ ≤ 0.7. 3. The optical recording medium according to claim 1, wherein a light interference layer is laminated on the light absorption layer. 4. The depth of the guide groove is 40 nm to 130 nm.
The optical recording medium according to any one of claims 1 to 3. 5. The depth of the guide groove is 50 nm to 100 nm.
The optical recording medium according to any one of claims 1 to 3. 6. The optical recording medium according to claim 1, wherein the dye used in the light absorbing layer is a phthalocyanine dye. 7. The optical recording medium according to claim 6, wherein the phthalocyanine dye is a dye represented by the formula (1) [Chemical Formula 1]. Embedded image [In the formula (1), M represents two hydrogen, or a metal, a metal oxide, or a metal halide, and Y ₁ , Y ₂ , Y ₃ ,
Y ₄ is oxygen or sulfur, and Z ₁ , Z ₂ , Z ₃ and Z ₄ are 4 to
An unsubstituted or substituted hydrocarbon group having 12 carbons is represented by X
₁ , X ₂ , X ₃ , X ₄ are halogens, l ₁ , l ₂ ,
l ₃ and l ₄ are 1 or 2, and m ₁ , m ₂ , m ₃ and m ₄ are 0
Represents an integer of 3; ] 8. A light absorbing layer containing a dye that absorbs at least laser light directly or through another layer on a transparent substrate, and a light reflecting layer directly or through a light interference layer on the light absorbing layer. Laminated, the reflectivity measured through the substrate is 77
65 for light λ ₁ having a wavelength selected from 0 to 830 nm
% Or more, light having a wavelength selected from 630 to 690 nm λ ₂
Is a recording / reproducing method of recording and reproducing information on an optical recording medium of 20% or less by using a laser beam of wavelength λ ₁ , and further by using a laser beam of wavelength λ _2. A recording / reproducing method characterized by being possible.