JPH08273193A - Optical recording medium - Google Patents

Abstract

PURPOSE: To enable recording and reproduction with light of wavelength λ1 in the region of 770-830nm and to enable reproduction even with light of wavelength λ2 in the region of 630-690nm. CONSTITUTION: This optical recording medium has a half mirror layer, a recording layer contg. a dye and a reflecting layer on the transparent substrate. The refractive index n1 and extinction coefft. k1 of the recording layer to light of wavelength λ1 in the region of 770-830nm are >=1.8 and 0.04-0.15, respectively, and the refractive index n2 and extinction coefft. k2 of the recording layer to light of wavelength λ2 in the region of 630-690nm are >=1.1 and 0.04-0.6, respectively. The reflectance of this medium measured through the substrate is >=65% to light of the wavelength λ1 and >=15% to light of the 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 having at least a half mirror layer, a recording layer containing a dye, and a reflective layer on a transparent substrate, and particularly a recordable compact disc (C
D-R) orange book standard (that is, it means that recording and reproduction can be performed with light having a wavelength selected from 770 to 800 nm), and visible light having a wavelength selected from 630 to 690 nm. The present invention relates to an optical recording medium that can be reproduced by an optical laser beam.

[0002]

2. Description of the Related Art A single-plate type recordable optical recording medium in which a dye is used as a recording layer and a metal reflective layer is provided on the recording layer to increase the reflectance and a protective layer is further provided on the reflective layer is, for example,
Optical Data Storage 1989 Technical Digest Serie
s Vol.1 45 (1989). A medium having a cyanine dye or a phthalocyanine dye used in the present invention in the recording layer of such a medium is commercially available as a CD-R medium. These media can be recorded with a 780 nm semiconductor laser, and are commercially available CD players and CD-ROMs equipped with a 780 nm semiconductor laser.
It has the feature that it can be played on a player.

However, these media have a capacity of only about 650 MB, and the recording time is as short as 15 minutes or less when recording a large amount of information such as a digital moving image. or,
As devices are becoming smaller, conventional media have a large capacity shortage. In the conventional CD-R medium, recording and reproducing were performed by using a semiconductor laser having a wavelength of around 780 nm, but recently, a semiconductor laser of 630 to 690 nm has been developed, which enables higher density recording and / or reproducing. Development of a player for high-density media is under consideration. This player is designed to be able to reproduce a read-only optical recording medium having a high reflectance of 70% or more, in which a pit is formed on the substrate at the time of molding and an aluminum reflection layer is provided. , CD-ROM and CD-R
It is desired that such media as can be played on the high density compatible player.

Since the conventional CD or CD-ROM medium has a high reflectance of 70% or more, it can be easily reproduced by a high density player. However, the CD-R media currently on the market certainly has a reflectance of 65% or more for light around 780 nm, and can be reproduced by a commercially available CD or CD-ROM player. However, when trying to reproduce with light of a short wavelength selected from 630 to 690 nm, the reflectance is 10%.
It will be very small, less than%, and will end. Further, the degree of modulation is small and the reflectance of the recording portion is large, so that low to high recording is performed, and the polarity is opposite to that of a normal CD (high to low recording), which is not preferable. Furthermore, a large distortion is observed in the recorded waveform. Due to these many shortcomings, conventional CDs
-It was difficult to reproduce the R medium by a high density player equipped with a laser selected from 630 to 690 nm. The reason is that the dye used in the recording layer of the above-mentioned conventional CD-R medium has a large wavelength dependency of optical characteristics, and has a large absorption at 600 to 750 nm when measured in a film state, and at the same time, it has a wavelength of about 780 nm. Film thickness and optical constants (refractive index, extinction coefficient) of the recording layer so that
Due to the design, the reflectance at 630-690 nm is small and the modulation is small. The reason for waveform distortion is that the optical path length of the recording pit is 630-69.
It is presumed that it is non-uniform for 0 nm light.

On the other hand, Japanese Patent Laid-Open No. 4-265541 discloses a medium in which a metal semi-transmissive film is provided on the substrate in order to increase the reflectance through the substrate. The medium has a vapor-deposited film of a copper phthalocyanine dye as a recording layer and has a reflectance of 71% for light of 780 nm. However, the medium is a CD
When the same pit edge (mark length) was recorded, a large distortion was observed in the reproduced waveform, the error rate and the jitter became large, and it could not be reproduced by a commercially available CD player.

Japanese Patent Laid-Open No. 5-109116 also discloses a medium in which a first light-reflecting layer is provided between a substrate and a recording layer. This medium contains a pentamethinecyanine dye or an indoorin Ni complex dye as a recording layer. And a reflectance of 75% is obtained for 780 nm light. However, when this medium is also recorded with the same pit edge (mark length) as the CD, a large distortion is observed in the reproduced waveform, the error rate and the jitter are increased, and we find that it cannot be reproduced by a commercially available CD player. It was Furthermore, this medium also has poor durability. Further, Japanese Patent Laid-Open No. 2-113453 discloses a medium in which a first interference film, a phase change recording film, a second interference film, a reflection film and a protective film are laminated on a substrate, and a medium having a wavelength of 780 nm 70 reflectance
% And a reflectance of light having a wavelength of 600 nm of 10% or more is disclosed. This medium has a reflectance of 70% or more with respect to light having a wavelength of 780 nm and can be reproduced by a commercially available CD player. However, as is clear from the examples, it is impossible to record with light of 780 nm. Recording uses light of wavelength 100 to 200 nm shorter than 780 nm.

On the other hand, Optical Data Strage TuC2-1 / 59,19
94 discloses a medium in which a half mirror layer, a dielectric layer, a phase change layer, a dielectric layer and a reflective layer are laminated on a substrate. It is stated that this medium uses an inorganic alloy capable of recording in the recording layer by phase change and is rewritable and satisfies the CD standard. However, this medium has very low sensitivity and requires a very high power laser for recording, which is not preferable. In this way, the conventional optical recording medium can obtain a reflectance of 65% or more for light having a wavelength selected from 770 to 830 nm,
There is no known medium which has high sensitivity, excellent recording characteristics (no waveform distortion, error rate and jitter), and which can be reproduced by light selected from 630 to 690 nm.

[0008]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
The present invention has been completed as a result of various studies to develop a medium capable of recording and reproducing using light having a wavelength selected from 830 nm, and capable of reproducing light having a wavelength selected from 630 to 690 nm. .

[0009]

The present invention has a half mirror layer having at least an appropriate thickness, a recording layer containing a dye which absorbs laser light, and a reflective layer on a transparent substrate,
The refractive index of the recording layer for light of wavelength λ1 selected from 770 to 830 nm is n1, the extinction coefficient is k1, the refractive index for light of wavelength λ2 selected from 630 to 690 nm is n2, and the extinction coefficient is k2. When n1 ≥ 1.8, 0.04 ≤ k1 ≤ 0.15, n2 ≥
1.1, 0.04 ≦ k2 ≦ 0.6, the reflectance measured through the substrate is 65% or more for the light of wavelength λ1, and the wavelength λ2
Is 15% or more with respect to the light of wavelength λ1, information can be recorded and reproduced by laser light of wavelength λ1, and can be reproduced by laser light of wavelength λ2. Further, in the recording layer The dye used is the above-mentioned optical recording medium which is a phthalocyanine dye represented by the following formula (1) and [Chemical Formula 2], and

[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; ] The half mirror layer is made of a metal having a reflectance of 80% or more,
The optical recording medium as described above, wherein the film thickness is 5 to 30 nm,
The optical recording medium according to any one of the above, wherein the reflective layer is made of gold, and the optical recording medium according to any one of the above, wherein the reflectance for light of the wavelength λ2 is 20% or more, and , Having at least a half mirror layer, a recording layer containing a dye and a reflective layer on a transparent substrate, and the reflectance measured through the substrate is 65% or more for light having a wavelength λ1 selected from 770 to 830 nm, Further, using the optical recording medium according to any one of the above, which has a reflectance of 15% or more for light having a wavelength λ2 selected from 630 to 690 nm, recording and reproducing of the recording are performed by laser light having a wavelength λ1, and The gist is a method of recording and reproducing information by reproducing this with a laser beam of wavelength λ 2.

The present invention will be described in detail below. The optical recording medium of the present invention has a reflectance of 65% or more measured through a substrate for light having a wavelength selected from 770 to 830 nm, and 630
It has a reflectance of 15% or more for light having a wavelength selected from ~ 690 nm. CDs and CD-ROMs currently on the market
The player is usually equipped with a semiconductor laser having a wavelength of around 780 nm and is made to be compatible with a medium having a reflectance of 65% or more. The medium of the present invention is a commercially available CD or CD-RO.
It can be played on M player. On the other hand, 630-69
There is currently no particular restriction on the reflectance of a medium that can be played back by a high-density compatible player equipped with a laser of a wavelength selected from 0 nm, but it is possible to use a signal from a medium such as a CD recorded with a pit edge (mark length). When the signal is detected, if the reflectance is very small, such as 10% or less, it is practically impossible to detect the signal and it is difficult to reproduce. Furthermore, high-density players are designed to be able to reproduce read-only optical recording media with high reflectance of 70% or more, but media with reflectance of 70% or more and reflections of 10% or less In order to be able to reproduce both the medium and the medium, the dynamic range of the reflectance is too wide, so that a troublesome means such as switching a circuit depending on the reflectance of the medium is required. For this reason, the reflectance for light having a wavelength selected from 630 to 690 nm is preferably 15% or more, more preferably 20% or more.

The optical recording medium of the present invention comprises at least a half mirror layer, a recording layer containing a dye absorbing a laser beam, and a reflective layer laminated on a transparent substrate.
The transparent substrate used in the optical recording medium of the present invention is preferably one having a light transmittance of 85% or more for recording and reading a signal and a small optical anisotropy. For example, known resin substrates such as acrylic resin, polycarbonate resin, and polyolefin resin can be used. These substrates may be plate-shaped or film-shaped, and may be 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 be provided by providing an ultraviolet curable resin layer on the substrate.

In the present invention, the half mirror layer provided on the substrate has a role of reflecting a part of the light incident through the substrate and transmitting the rest. A substance having a high reflectance is used for the half mirror layer, and a metal having a reflectance of 80% or more, for example, a metal such as gold, silver, copper, or aluminum, or an alloy containing these metals as a main component is preferable, and has a high durability. From the viewpoint, gold, copper and alloys thereof are more preferable. The film thickness of this half mirror layer is preferably 5 to 30 nm. If this film thickness is too thin, for example, less than 5 nm, the reflectance for light of λ2 is less than 15%, and if it is too thick, for example, more than 30 nm, the reflectance for light of λ1 is too large, and the recording sensitivity or The degree of modulation is lowered, which is not preferable.

As a method for forming the half mirror layer,
A vacuum deposition method, a sputtering method, an ion plating method and the like can be mentioned. When forming the half mirror layer on the substrate, a layer made of an inorganic material or a polymer may be provided on the substrate in order to improve the heat resistance and recording sensitivity of the substrate.

In the present invention, the recording layer contains a dye that absorbs laser light. The optical characteristics of this recording layer are important in terms of reflectance, recording sensitivity, modulation degree, etc.
Refractive index n for light λ1 of wavelength selected from ~ 830 nm
1 is 1.8 or more, extinction coefficient k1 is 0.04 to 0.15, and 630 to 6
Refractive index n2 for light of wavelength λ2 selected from 90 nm
Is 1.1 or more and the extinction coefficient k2 is preferably 0.04 to 0.6. n
When 1 is less than 1.8 or k1 exceeds 0.15, it becomes difficult to make the reflectance for light of λ1 65% or more, and k
When 1 is less than 0.04, the recording sensitivity for light of λ1 is lowered. If n2 is less than 1.1 or k2 exceeds 0.6, the reflectance for light of λ2 is less than 15%, which is not preferable. The lower limit of k2 is not particularly limited, but it is desirable that recording can be performed with light of λ2, so less than 0.04 is not preferable from the viewpoint of recording sensitivity to light of λ2. The dye used in the recording layer is a dye that absorbs laser light having a wavelength of λ1 used for recording, and examples thereof include phthalocyanine dyes, polymethine dyes, cyanine dyes, azo dyes, and naphthoquinone dyes. The phthalocyanine dye is preferable from the viewpoint of light resistance and durability of the dye, and further, from the viewpoint of recording characteristics such as the optical constant of the recording layer, recording sensitivity, modulation degree, distortion of recording waveform, error rate and jitter, the formula ( The phthalocyanine dye represented by 1) is most preferable.

Specific examples of M in the phthalocyanine dye represented by the formula (1) include Cu, Pd, Ni, Mg,
Examples thereof include divalent metals such as Zn, Pb, and Cd, metal oxides such as VO, and metal halides such as AlCl. On the other hand, Z ₁ , Z ₂ , Z ₃ , and Z ₄ are unsubstituted or substituted hydrocarbon groups having 4 to 12 carbon atoms, and specifically, butyl group, pentyl group, hexyl group, heptyl group, Saturated hydrocarbon groups such as octyl group, nonyl group, decyl group, dodecyl group, cyclohexyl group, dimethylcyclohexyl group,
An unsaturated hydrocarbon group such as a butenyl group, a hexenyl group, an octenyl group, a dodecenyl group, a phenyl group, a methylphenyl group, a butylphenyl group and a hexylphenyl group can be used. These hydrocarbon groups may be linear or branched. Further, these hydrocarbon groups may be substituted with halogen, amino group, ether group or the like. Even when it is substituted with an amino group or an ether group, the total number of carbon atoms in the substituent is 4 to 12. Also, X ₁ , X ₂ ,
The halogen represented by X ₃ and X ₄ is fluorine, chlorine,
Examples include bromine and iodine.

The substituents and Y ₁ to Y ₄ in X ₁ to X ₄ described above are attached to the benzene rings constituting phthalocyanine
The substitution position of the substituent is not particularly limited, and the kind and number of the substituents may be different in the four benzene rings in one molecule. Among the phthalocyanine dyes mentioned above,
In view of recording characteristics such as reflectance and sensitivity, waveform distortion, error rate and jitter, 1 is preferably ₁ to l ₄ . More specific examples of preferable phthalocyanine dyes include, for example, JP-A
Examples thereof include dyes described in JP-A-3-62878, JP-A-3-141582, and JP-A-3-215466.

In the present invention, a recording layer containing the above-mentioned dye is provided on the half mirror layer. The method for providing the recording layer includes, for example, a spin coating method, a dipping method, a spraying method, a vapor deposition method and the like, but the spin coating method is simple and preferable. When forming a film by the spin coating method, it is preferable to select a solvent that does not damage the substrate or the half mirror layer. As a coating solvent when forming a film by the spin coating method,
Non-polar solvents and polar solvents are preferred. Specific examples of the non-polar solvent include hexane, heptane, octane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, propylcyclohexane, cyclooctane and other aliphatic hydrocarbon solvents and dipropyl ether, ethers such as dibutyl ether. Examples include system solvents. Specific examples of polar solvents include ethyl alcohol, propyl alcohol, butyl alcohol,
Examples include alcohol solvents such as furfuryl alcohol, ethylene glycol monomethyl ether, and tetrafluoropropanol. At this time, aromatic hydrocarbons such as toluene, xylene and propylbenzene, ester solvents such as ethyl acetate, butyl acetate, amyl acetate and ethylene glycol monoethyl ether acetate, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone Alternatively, a halogen-based solvent such as chloroform, carbon tetrachloride, or methylchloroform, or an ether-based solvent such as dioxane or tetrahydrofuran may be partially used in combination as long as it does not adversely affect the solvent. From the viewpoint of solubility in this solvent, in the phthalocyanine dye of the formula (1), Z ₁ , Z
_The groups represented by ₂ , Z ₃ and Z ₄ are preferably groups having 6 to 12 carbon atoms. Further, after forming the recording layer by the spin coating method, heating may be performed to dry the solvent.

When forming the recording layer, a binder may be used together if necessary. Preferred binders include nitrocellulose, cellulose acetate, ketone resins, acrylic resins, polyvinyl butyral, polycarbonates, polyolefins and the like. Further, other dyes may be added to improve recording characteristics.
The film thickness of the recording layer affects the degree of modulation and reflectance, but in the present invention, it is 70 nm to 300 nm, preferably 80 nm to 250 nm. When the recording layer is formed, a layer made of an inorganic dielectric material, a polymer or an organic compound may be further provided between the half mirror layer and the recording layer in order to improve recording characteristics, reflectance and the like.

In the present invention, a reflective layer is provided on the recording layer. As the reflective layer, metals such as gold, silver, aluminum and copper and alloys containing these metals are used, and gold is preferable from the viewpoint of reflectance and durability. Of course, other metals may be added in small amounts. The amount of other metals added is 10
% Or less, preferably 5% or less, more preferably 2% or less. The thickness of the reflective layer is usually 40 nm to 300 nm, preferably
60 nm to 200 nm. Examples of the method for forming the reflective layer include vacuum vapor deposition, sputtering, and ion plating. When the reflective layer is provided, an intermediate layer made of an inorganic dielectric material, a polymer, a dye or an organic compound may be provided between the recording layer and the reflective layer in order to improve reflectance and recording characteristics.

Further, in the present invention, in order to protect the recording layer and the reflective layer, a protective layer may be provided on the reflective layer or a film or a resin substrate may be laminated. Further, two sheets of the medium of the present invention may be stuck together. As the protective layer, an ultraviolet curable acrylic resin, an ultraviolet curable epoxy resin, a silicone hard coat resin or the like is used. The thickness of the protective layer is usually about 1 to 100 μm. Further, an ultraviolet curable resin, an inorganic thin film, or the like may be formed on the mirror surface side of the substrate to protect the surface and prevent adhesion of dust and the like. The thus-obtained optical recording medium of the present invention can perform recording and reproduction by focusing laser light on the recording layer. A signal used for recording is, for example, an EFM used in a CD or the like.
Modulated signals are preferred for achieving the effects of the present invention.

The optical recording medium of the present invention uses a dye having absorption in the vicinity of 770 to 830 nm in the recording layer, and 770 to 830 n.
Since a reflectance of 65% or more with respect to light having a wavelength selected from m is obtained, recording and reproduction can be performed with laser light having a wavelength of around 780 nm. Also, the recorded information can be recorded on a commercially available CD or CD.
-Can be played on a ROM player. The reproduced signal characteristics sufficiently satisfy the Orange Book standard, which is the CD-R standard. The optical recording medium of the present invention further comprises 630-
A reflectance of 15% or more for light of a wavelength selected from 690 nm is obtained, and it can be played back even by a high-density optical disc player equipped with a next-generation 630-690 nm laser. The wavelength of light used for the next high density compatible player is 630
The wavelength of the laser for practical use is, for example, about 635 nm, 650 nm, or 680 nm.
Further, the medium of the present invention has an absorption at 630 to 690 nm,
It is also possible to record using light with a wavelength selected from 630 to 690 nm.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited thereto. Example 1 An injection-molded polycarbonate substrate having a spiral groove (depth 140 nm, width 0.4 μm, pitch 1.2 μm) having a thickness of 1.2 mm and a diameter of 120 mm has a thickness of 15 nm by sputtering. A half mirror layer of gold was deposited. Next, a brominated phthalocyanine dye obtained by adding an average of 3.5 bromine per molecule to Pd-phthalocyanine having a 1-isopropyl-isoamyloxy group at each α-position of each of the four benzene rings constituting phthalocyanine
A 3.5 wt% dimethylcyclohexane solution was dropped, and the resin substrate was rotated to form a recording layer on the half mirror layer by a spin coating method.
The thickness of the recording layer was 150 nm. The optical constants of this recording layer are such that the refractive index n1 is 2.2 and the extinction coefficient k1 is 0.08 for light having a wavelength of 780 nm, and the refractive index n2 is 1.2 and extinction coefficient is for light having a wavelength of 635 nm. Was 0.34. next,
A gold thin film with a thickness of 80 nm was formed as a reflective layer on this recording layer by sputtering, and then an ultraviolet curable resin (SD-17, made by Dainippon Ink) was spin-coated on this reflective layer. Was irradiated to form a protective layer having a film thickness of 5 μm to manufacture an optical recording medium. This optical recording medium is placed on a turntable, and while rotating at a linear velocity of 2.8 m / s, the laser beam is passed through the substrate using a drive (Philips CDD-521) equipped with a semiconductor laser having an oscillation wavelength of 780 nm. While controlling to focus on the recording layer on the groove and recording the EFM modulation signal while changing the recording laser power, the laser output is 1 m using the same device.
The signal recorded at W was read. The error rate was the smallest at the laser output of 8.5 mW (optimum recording power), which was 4 × 10 ^-3 . The reflectance of the unrecorded area is
74%, Jitter 23 ns, Modulation degree was large enough, and very good recording and reproducing was possible. Also, almost no distortion was observed in the reproduced waveform. Also, this medium could be played back without trouble on a commercial CD player equipped with a laser with a wavelength of 786 nm. Next, the recorded optical recording medium was reproduced with a high density compatible player equipped with a 635 nm semiconductor laser. The reflectance was 28%, the degree of modulation was large, and the reflectance of the recording portion was high to low recording.
Moreover, both the error rate and the jitter were small, and very good reproduction was possible. Furthermore, when reproduced with a player equipped with a 680 nm semiconductor laser, the reflectivity of the unrecorded part is 23%, high to low recording, the degree of modulation is large, and
The error rate and jitter were small and very good reproduction was possible. In addition, when recorded with 680 nm light, this medium is 8.
It was confirmed that very good recording was possible with a recording power of 8.8 mW at a linear velocity of 4 m / s. The refractive index of the recording layer for light of 680 nm was 1.20 and the extinction coefficient was 0.49.

Example 2 A medium was prepared and evaluated according to Example 1 except that 7 nm copper was used for the half mirror layer. The optimum recording power at 780 nm is
At 9.0mW, the reflectance was 70%, the error rate and the jitter were 2 × 10 ^-3 and 24ns, respectively, and the degree of modulation was sufficiently large, and extremely good recording and reproducing were possible. Also, almost no distortion was observed in the reproduced waveform. Moreover, it could be reproduced well even with a commercially available CD player. Furthermore, when reproduced at 635 nm, the reflectance is 23%, high to low recording, the degree of modulation is large, and
The error rate and jitter were small and very good reproduction was possible.

Comparative Examples 1 and 2 The same method as in Example 1 was adopted except that the half mirror layer was made extremely thin with a thickness of 3 nm (Comparative Example 1) and was extremely thick with 40 nm (Comparative Example 2). Each medium was made and evaluated. The medium of Comparative Example 1 has an optimum recording power of 8.6 mW, 63
The reflectance at the wavelength of 5 nm is 10% and low to h
With igh recording, the degree of modulation was so small that it could not be played on a high-density compatible player. In addition, the recording medium has a recording power of Comparative Example 2.
Almost no recording was possible even at 17mW.

Example 3 A Cu / phthalocyanine dye having a 1-isopropyl-isoamyloxy group at one α-position of each of four benzene rings constituting phthalocyanine was used as the dye, and 25 nm of gold was used as the half mirror layer. Was evaluated by making a medium in the same manner as in Example 1. The optical constant of the recording layer of this medium is such that the refractive index n1 is 2.0 for light having a wavelength of 780 nm,
The extinction coefficient k1 was 0.06, the refractive index n2 was 1.2 and the extinction coefficient was 0.30 for light with a wavelength of 635 nm. 780nm
The optimum recording power was 9.2 mW, the reflectance was 74%, the error rate and the jitter were 4 × 10 ^-3 and 25 ns, respectively, and the degree of modulation was sufficiently large, and extremely good recording and reproducing were possible. Almost no distortion was observed in the reproduced waveform, and good reproduction was possible even with a commercially available CD player. Also, when reproduced at 635 nm, a reflectance of 30% was obtained, high to low recording, a large degree of modulation, a small error rate and a small jitter, and extremely excellent reproduction was possible.

Example 4 Ni having an octylthio group at one α-position of each of four benzene rings constituting phthalocyanine as a dye
A medium was prepared and evaluated in the same manner as in Example 1 except that the phthalocyanine dye was used. The optical constants of the recording layer of this medium have a refractive index n1 of 2.3 and an extinction coefficient k1 of 0.12 for light having a wavelength of 780 nm, and a refractive index of 1.2 and an extinction coefficient for light of a wavelength of 635 nm. Was 0.30. Optimum recording power at 780nm is 8.7mW, reflectance is 69%, error rate,
The jitter was 6 × 10 ^-3 and 28 ns, respectively, and the degree of modulation was sufficiently large, and extremely good recording and reproduction were possible. Almost no distortion was observed in the reproduced waveform, and good reproduction was possible even with a commercially available CD player. 30% reflectance when reproduced at 635 nm
Thus, the degree of modulation was large, the error rate and the jitter were small, and very good reproduction was possible.

Comparative Example 3 According to Example 1 of Japanese Patent Application Laid-Open No. 4-265541, gold was formed on a polycarbonate substrate to a thickness of 10 nm by a vacuum deposition method, and then copper phthalocyanine was deposited to a thickness of 100 nm to form a recording layer. A 60 nm thick gold layer was formed thereon as a reflective layer by a vacuum vapor deposition method, and an ultraviolet curable resin [SD-17, manufactured by Dainippon Ink and Chemicals, Inc.] was spin-coated to prepare an optical recording medium medium for evaluation.
When recording the same EFM modulated signal as CD, a large distortion was observed in the reproduced waveform, the error rate and the jitter far exceeded the standard values, and it could not be reproduced by the CD player.

[0029]

As is clear from the examples and comparative examples of the present invention, in the present invention, at least a half mirror layer, a recording layer containing a specific phthalocyanine dye, on a substrate,
In an optical recording medium having a reflective layer, the optical constant of the recording layer and the film thickness of the half mirror layer are optimized,
Recording with the light of wavelength λ1 by setting the reflectance for light of wavelength λ1 selected from 0 nm to 65% or more and the reflectance to light of wavelength λ2 selected from 630 to 690 nm of 15% or more. Can be reproduced (satisfies the Orange Book standard) and can be reproduced by using light having a wavelength of λ2.

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

Claims (6)

[Claims] 1. A transparent substrate having a half mirror layer of at least an appropriate thickness, a recording layer containing a dye for absorbing laser light and a reflective layer, and having a wavelength λ1 selected from 770 to 830 nm of the recording layer. When the refractive index for light is n1, the extinction coefficient is k1, and the refractive index for light of wavelength λ2 selected from 630 to 690 nm is n2 and the extinction coefficient is k2, n1 ≥1.8
, 0.04 ≤ k1 ≤ 0.15, n2 ≥ 1.1, 0.04 ≤ k2 ≤ 0.6
The reflectance measured through the substrate is 65% or more for light of wavelength λ1 and 15% or more for light of wavelength λ2, and information can be recorded and reproduced by laser light of wavelength λ1. An optical recording medium that can be reproduced by a laser beam having a wavelength of λ2. 2. The optical recording medium according to claim 1, wherein the dye used in the recording layer is a phthalocyanine dye represented by the following 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; ] 3. The optical recording medium according to claim 1, wherein the half mirror layer is made of a metal having a reflectance of 80% or more and the film thickness is 5 to 30 nm. 4. The optical recording medium according to claim 1, wherein the reflective layer is made of gold. 5. The reflectance for light of the wavelength λ2 is 20%
It is above, The optical recording medium in any one of Claims 1-4. 6. A transparent substrate having at least a half mirror layer, a recording layer containing a dye and a reflective layer, and having a reflectance measured through the substrate of light having a wavelength λ1 selected from 770 to 830 nm. Recording with a laser beam of wavelength λ1 using the optical recording medium according to any one of claims 1 to 5, which has a reflectance of 65% or more and a reflectance of light of wavelength λ2 selected from 630 to 690 nm of 15% or more. And playing the recording,
Also, a method of recording and reproducing information by reproducing this with laser light of wavelength λ2.