JP2001307375A - Optical information recording medium and method for optical information recording and reproducing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium in which information can be recorded with laser light in the recording and reproducing wavelength region for a DVD-R and in 390 to 440 nm wavelength region and to provide a method for optical information recording and reproducing to record information in the medium at the above short wavelength and to reproduce the information recorded in the medium by using a conventional recording and reproducing system for a DVD-R. SOLUTION: The optical information recording medium has a recording layer containing a dye compound in which information can be recorded by irradiation of laser light on a board. The recording layer is formed in such a manner that it shows >=20% reflectance for laser light in the wavelength region from 390 to 440 nm and for laser light in the wavelength region from 620 to 690 nm and that the real part n and the absolute value k of the imaginary part of the complex refractive index satisfy n>=1.8 and 0.02<k<0.5, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium capable of recording and reading information by irradiating a laser beam. More specifically, the present invention relates to an optical information recording medium and an optical information recording / reproducing method capable of recording and reading information by irradiating laser light in two wavelength ranges.

[0002]

2. Description of the Related Art A write-once optical information recording medium (a so-called CD-R type optical disk) capable of recording information only once by irradiating a laser beam has been put to practical use. A CD-R type optical disc generally has a recording layer made of a dye on a disc-shaped substrate,
A reflective layer made of metal is provided in this order, and a protective layer made of resin is provided on the reflective layer by coating so as to cover the reflective layer.

A write-once DVD (Digital Video Disk) is an optical disk on which recording and reproduction can be performed using a laser beam having a shorter wavelength than a CD-R type optical disk.
DVD-R) has been proposed (for example, “Nikkei New Media” separate volume “DVD”, published in 1995). DVD
-As an R-type optical disc, a guide groove (pre-groove) for tracking laser light to be irradiated is formed on a transparent disk-shaped substrate formed to be less than half as narrow as a CD-R type optical disc. A recording layer made of an organic dye, and a structure in which two laminates each of which is usually further provided with a reflective layer and a protective layer on the recording layer are bonded with an adhesive with each of the recording layers inside. Or a laminated body composed of the above two sheets, one of which is generally replaced with a disc-shaped protective plate, and only one substrate is provided with a recording layer, a reflective layer, and a protective layer in that order. It is. It is said that this type of optical disk can record 6 to 8 times the capacity of a CD-R type optical disk.

[0004] Writing (recording) and reading (reproduction) of information on the CD-R or DVD-R is performed using a visible laser beam (usually a CD-R having a wavelength of 750 to 800 nm and a DVD-R).
Is performed by irradiating a laser beam having a wavelength in the range of 600 to 700 nm. That is, when the above-mentioned laser light is irradiated on the optical disk, the irradiated part of the dye recording layer absorbs the light and locally raises the temperature, and changes physically or chemically (for example, generation of pits and the like), Information is recorded by changing the optical characteristics. On the other hand, reading of information is also usually performed by irradiating the optical disk with laser light having the same wavelength as the recording laser light, and a portion where the optical characteristics of the dye recording layer has changed (recorded portion due to generation of pits or the like). This is carried out by detecting a difference in reflectance between the part and the part that does not change (unrecorded part).

[0005] Recently, with the rapid spread of networks such as the Internet and Hi-Vision TVs, there has been an increasing demand for large-capacity recording media for easily and inexpensively recording image information. In response to such a demand, an optical disc having a larger recording capacity has been developed by increasing the recording density by using a laser beam having a shorter wavelength than that of the DVD-R. For example, Japanese Patent Application Laid-Open No. 11-53758 discloses an optical information recording medium having a recording layer containing an organic dye and a light reflection layer formed of silver or an alloy thereof, from the recording layer side to the light reflection layer side. Wavelength 5 towards
A recording / reproducing method for recording / reproducing information by irradiating a laser beam of 30 nm or less is disclosed. Specifically, an optical disk using a metal azo dye, a quinophthalone dye or a trimethine cyanine dye as a dye of a recording layer is irradiated with a blue (wavelength 410 nm) or blue-green (wavelength 515 nm) semiconductor laser beam. Has proposed an information recording / reproducing method for recording / reproducing information.

Japanese Patent Application Laid-Open No. 58-56239 discloses a recording layer in which a plurality of dyes are mixed.
An optical recording medium having an optical absorptivity of 80% or more at all wavelengths of 00 nm and adapted to a change in laser light source is described. JP-A-10-181112
In the publication, recording and reproduction are possible at 620 to 690 nm,
An optical recording medium for a DVD-R having a cyanine dye-containing recording layer having n of 1.6 to 4.0, k of 0.01 to 0.45, and a maximum absorption peak wavelength of 500 to 655 nm is described.

Japanese Patent Publication No. 2925121 discloses that a recording layer containing two or more cyanine dyes having an absorption maximum of 600 to 900 nm and an azo dye having an absorption maximum of 350 to 600 nm has improved light resistance. Described optical information recording medium. Japanese Patent Application Laid-Open No. 10-162429 discloses a light source such as a CD-R or DVD-R capable of recording and reproducing information in a wavelength range of 770 to 830 nm and reproducing information in a wavelength of 630 to 680 nm. An information recording medium is described. JP-A-9-66671
The publication discloses n at 780 nm and 630-650 nm.
An optical information recording medium is described, in which recording layers specifying k and k respectively correspond to the Orange Book standard, and are capable of recording and reproducing at a short wavelength.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
By further shortening the recording wavelength as described in JP-A-758-758, it becomes possible to design an optical information recording medium having a larger recording capacity. The recorded image information is usually reproduced using a recording / reproducing system dedicated to short wavelengths using laser light having a wavelength range substantially the same as that of the recording laser light. It would be convenient if it could be played back using an existing recording and playback system used for DVD-Rs.

It is an object of the present invention to provide a recording / reproducing wavelength region for DVD-R and a laser beam having a wavelength region shorter than the wavelength region, in particular, a laser beam having a wavelength in a range of 390 to 440 nm. It is to provide an information recording medium. Another object of the present invention is to provide an optical information recording medium and an optical information recording / reproducing method capable of reproducing information recorded at a short wavelength as described above using an existing recording / reproducing system.

[0010]

According to the research of the present inventors,
By setting the optical constant of the recording layer of the optical information recording medium to be within a specific range, optical information showing good recording / reproducing characteristics with respect to DVD-R laser light and blue or blue-violet laser light. It has been found that recording media can be manufactured. Specifically, as a recording material, a specific rhodocyanine compound having an absorption curve having an absorption maximum wavelength on the shorter wavelength side than the wavelength region of the two laser beams as described above. It has been found that the intended use can produce a desired optical information recording medium.

The present invention relates to an optical information recording medium having a recording layer containing a dye compound on which information can be recorded by irradiating a laser beam on a substrate, wherein the recording layer is 390 to 440n.
The reflectivity of each of the laser light having a wavelength of m and the laser light having a wavelength of 620 to 690 nm is 20%.
Or more (preferably 30% or more, more preferably 40%
The absolute value k of the real part n and the imaginary part of the complex refractive index of the recording layer is n ≧ 1.8 and 0.0
An optical information recording medium characterized by being formed so as to satisfy the relationship of 2 <k <0.5.

Further, according to the present invention, after irradiating the optical information recording medium having the above structure with a laser beam having a wavelength in the range of 390 to 440 nm to record information, the information is recorded at 620 to 690 nm.
There is also an optical information recording / reproducing method characterized in that information is reproduced by irradiating a laser beam having a wavelength in the range described above.

The optical information recording medium and the optical information recording / reproducing method of the present invention are preferably in the following modes. (1) The real part n of the complex refractive index of the recording layer with respect to the laser light having a wavelength in the range of 390 to 440 nm and the laser light having the wavelength in the range of 620 to 690 nm is n ≧ 2.0 (more preferably, n ≧ 2). .1, and particularly preferably n ≧ 2.2). (2) The recording layer has a thickness of 0.05 ≦ k ≦ 0.3 (more preferably 0.08 ≦ k ≦ 0.25, particularly preferably 0. .1
≦ k ≦ 0.2) optical information recording medium.

(3) The recording layer is provided with a laser beam having a wavelength in the range of 390 to 440 nm in a range of 0.03 ≦ k ≦ 0.3.
(More preferably, 0.04 ≦ k ≦ 0.25, particularly preferably, 0.05 ≦ k ≦ 0.2). (4) The dye compound has at least two or more absorption maximum wavelengths in its absorption curve, and the long wavelength side end of the sub-absorption is in the wavelength range of laser light in the range of 390 to 440 nm. Optical information recording medium. (5) An optical information recording medium in which the dye compound is a rhodocyanine compound represented by the following general formula:

[0015]

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[In the above general formula, R ¹ , R ² ,
R ³ and R ⁴ are each independently a saturated or unsaturated alkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 4, and X ⁻ is an organic or inorganic counter ion. is there].

(6) An optical information recording medium in which the dye compound is a rhodocyanine compound represented by the following formula:

[0018]

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(7) The thickness of the recording layer in the pre-groove is 50 to 200 nm (preferably 60 to 150 nm).
nm, particularly preferably 65 to 120 nm).

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The optical information recording medium (sometimes referred to as an optical disk) of the present invention has a recording layer containing a dye compound capable of recording information by irradiating a laser beam on a transparent disc-shaped substrate. Have. And the recording layer is 390-
Laser light having a wavelength in the range of 440 nm and 620 to 690
The reflectivity for laser light having a wavelength in the range of
% Or more, and the real part n of the complex refractive index of the recording layer,
And the absolute value k of the imaginary part thereof is n ≧ 1.8, respectively.
Further, it is characterized by being formed so as to satisfy the relationship of 0.02 <k <0.5. Specifically, a dye compound is selected and used so that the optical characteristics of the recording layer satisfy the above relationship.

In general, the complex refractive index n ₀ is given by n ₀ = n-ik
(N: refractive index, k: extinction coefficient). The complex refractive index of the recording layer containing the dye compound changes depending on the wavelength of the laser beam used. In the optical information recording medium of the present invention, 620 to 690 nm (preferably 630 to 66 nm)
0 nm) and a laser beam having a wavelength in the range of 390 to 440 nm, the recording layer is adjusted to satisfy the above relational expression with respect to the laser beams in these two wavelength ranges. I have. In order for the optical information recording medium of the present invention to obtain better sensitivity and exhibit excellent recording characteristics, k is 0.02 ≦≦ with respect to laser light having a wavelength in the range of 620 to 690 nm. k ≦ 0.3 (more preferably 0.04 ≦ k ≦ 0.25, particularly preferably 0.0
6 ≦ k ≦ 0.2). Also,
For laser light having a wavelength in the range of 390 to 440 nm, k is 0.03 ≦ k ≦ 0.3 (more preferably,
0.04 ≦ k ≦ 0.25, particularly preferably 0.05 ≦
(k ≦ 0.2). On the other hand, in the reproduction characteristics, in order to give a greater degree of modulation, n is n ≧ 2.
0 (more preferably n ≧ 2.2, particularly preferably n ≧
It is preferable that the relationship of 2.5) is satisfied.

The dye compound used in the recording layer is not particularly limited as long as the optical characteristics of the recording layer satisfy the above-mentioned relationship, but the dye compound may be used in a wavelength range of 390-440 nm. It is preferable that the side absorption of the absorption curve can be used. For example, the dye compound used in the present invention has at least two or more absorption maximum wavelengths in its absorption curve, and the long wavelength side end of the sub-absorption has a wavelength of 390 to 440 nm. It is preferably in the wavelength range. That is, the dye compound has the maximum wavelength of the sub-absorption on the shorter wavelength side than the wavelength range of the laser light on the shorter wavelength side (the maximum wavelength of the sub absorption of the dye compound is the wavelength range of the laser light on the shorter wavelength side). Offset to the shorter wavelength side, generally this offset is ± 2
(In the range of 0 nm). Preferable dye compounds having such an absorption curve include, for example, a rhodocyanine compound represented by the following general formula (1) [the meanings of symbols in the formula are as defined above], and particularly, a rhodocyanine compound represented by the following formula (2). be able to.

[0023]

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FIG. 1 shows an absorption spectrum (absorption curve) of the above dye compound in a wavelength range of blue or blue-violet to red. For example, as will be described later, for the laser light having a wavelength of 408 nm (blue violet) used in the examples of the present invention, by utilizing the sub-absorption maximum (sub-absorption peak) of about 390 nm of the dye compound, Recording and reproduction can be performed. On the other hand, for a laser beam having a wavelength of 638 nm (red), recording and reproduction can be performed in the same manner by using the 600 nm main absorption maximum (main absorption peak) of the dye compound.

Next, a method for manufacturing the optical information recording medium of the present invention in which a recording layer having the above-described optical characteristics is provided on a substrate will be described. The optical information recording medium of the present invention is manufactured by providing a recording layer on a substrate. The optical information recording medium of the present invention can have various configurations. Possible configurations include, for example, a configuration having a recording layer and a reflective layer on a transparent disc-shaped substrate in this order, a configuration having a recording layer, a reflective layer and a protective layer on the disc-shaped substrate in this order, or the disc-shaped A structure in which two laminates each having a recording layer and a reflective layer, and further a protective layer provided on a substrate are joined by an adhesive layer such that the recording layer side is inside, or the laminate and a disc shape A structure in which a protective substrate (a reflective layer other than the recording layer may be provided on the substrate) may be similarly bonded so that the recording layer side is on the inside. In the case of these configurations, laser light is emitted from the transparent substrate side.

Further, the optical information recording medium has a structure in which a reflective layer, a recording layer, and a protective layer are sequentially formed on a disk-shaped substrate. Configuration having in order, or protective layer, recording layer, reflective layer,
It is also possible to adopt a configuration having a disk-shaped substrate, an adhesive layer, a disk-shaped substrate, a reflective layer, a recording layer, and a protective layer in that order. In the case of these configurations, laser light is applied from the protective layer side. In the case of these configurations, the disc-shaped substrate does not need to be transparent. It is preferable that the optical information recording medium of the present invention has a mode in which a laser beam is irradiated from the substrate side.
Hereinafter, a method for manufacturing the optical information recording medium of the present invention will be described in detail by taking an optical information recording medium having only a recording layer on a transparent disk-shaped substrate as an example.

The substrate can be arbitrarily selected from various materials used as a substrate of a conventional optical information recording medium. Examples of the substrate material include glass; polycarbonate; acrylic resins such as polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer; epoxy resins; amorphous polyolefin and polyester; May be used in combination. Note that these materials can be used in the form of a film or a rigid substrate. Among the above materials, polycarbonate is preferred from the viewpoints of moisture resistance, dimensional stability, cost, and the like.

It is preferable that a pre-groove having a constant track pitch is formed on the surface of the substrate on which the recording layer is provided. The track pitch of the pre-groove formed on the substrate of the optical information recording medium of the present invention is, for example, 0.5 to 1.0 μm (more preferably, to match the track pitch formed for the conventional DVD-R). Is
(0.6-0.9 μm) can be set,
In accordance with the laser light (recording light) in the range of 390 to 440 nm, the width can be set to be narrower, whereby the recording density can be increased. The track pitch of the pre-groove adjusted to the short-wavelength laser light is 0.2
5 to 0.7 μm (more preferably, 0.3 to 0.55 μm
m, particularly preferably 0.35 to 0.50 μm).

The pregroove has a side wall of 55 to 80 °.
(More preferably, it is preferable to incline at an angle in the range of 60 to 80 °.) Here, the inclination angle of the side wall refers to a point on the side wall of the groove at a position 10% of the depth of the groove from the bottom surface of the pre-groove (concave groove) and 5% of the depth of the groove.
It means the angle formed by the extension of the straight line connecting the point on the side wall of the groove at the 0% position and the horizontal plane on the bottom surface of the concave groove. By setting the inclination angle of the side wall of the pre-groove to a steep angle in this manner, crosstalk can be suppressed even when the track pitch of the pre-groove becomes narrow, and an increase in the jitter value can be suppressed. The pregroove having such a shape is formed by, for example, using a resin molding stamper (die) that has been processed so as to have a sidewall having a predetermined inclination angle when the substrate is subjected to injection molding or extrusion molding. Can be formed.

The groove shape (depth and width) of the pre-groove can be set to be narrower than that of a DVD-R according to the laser light (recording light) in the range of 390 to 440 nm. The depth of the pregroove is 30 to 170 nm (more preferably 50 to 140 nm, particularly preferably 65 to 1 nm).
30 nm), and the width (half width) of the pre-groove is 65 to 300 nm (more preferably 95 to 260 nm, particularly preferably 130 to 2 nm).
30 nm).

An undercoat layer may be provided on the surface of the substrate on which the recording layer is provided, for the purpose of improving flatness, improving adhesive strength, preventing deterioration of the recording layer, and the like. As the material of the undercoat layer, for example, polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, styrene / vinyltoluene copolymer,
Chlorsulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester,
Examples include polyimide, a polymer substance such as vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, and polycarbonate; and a surface modifier such as a silane coupling agent. The undercoat layer is prepared by dissolving or dispersing the above substance in an appropriate solvent to prepare a coating solution, and then applying the coating solution to the substrate surface using a coating method such as spin coating, dip coating, or extrusion coating. Can be formed. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably in the range of 0.01 to 10 μm.

The pre-groove may be formed by providing a pre-groove layer. As a material for the pregroove layer, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetraester and a photopolymerization initiator can be used. For the formation of the pre-groove layer, for example, first, a mixed solution composed of the above-mentioned acrylate ester and the polymerization initiator was applied on a precisely formed master (stamper), and further, a substrate was placed on this coating solution layer. Thereafter, the coating layer is cured by irradiating ultraviolet rays through the substrate or the matrix to fix the substrate and the coating layer. Next, it can be obtained by peeling the substrate from the matrix. The thickness of the pre-groove layer is generally from 0.03 to 70
It is in the range of μm, preferably in the range of 0.06 to 35 μm.

A recording layer containing a dye compound is provided on the substrate. The recording layer was formed, for example, by dissolving the specific dye compound in a solvent to prepare a coating solution, and applying the coating solution to the surface of the substrate on which the pre-groove was formed to form a coating film. Thereafter, drying can be performed. In preparing the coating solution, a discoloration inhibitor may be added, and if desired, a binder may be added.

Examples of the solvent for the coating solution for forming the recording layer include esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; dichloromethane;
Chlorinated hydrocarbons such as dichloroethane and chloroform; amides such as dimethylformamide; hydrocarbons such as cyclohexane; ethers such as tetrahydrofuran, ethyl ether and dioxane; ethanol, n-propanol, isopropanol, n-butanol and diacetone alcohol. Alcohols such as 2,2,3,3-tetrafluoropropanol; and glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and propylene glycol monomethyl ether. The above solvents can be used alone or in combination of two or more in consideration of the solubility of the compound to be used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution according to the purpose.

Representative examples of the anti-fading agent include nitroso compounds, metal complexes, diammonium salts, and aminium salts. These examples are described, for example, in JP-A-2-300288 and JP-A-3-224793.
Or each of the publications such as JP-A No. 4-146189. When an anti-fading agent is used, its amount is usually 0.1 to 50% by weight based on the amount of the coloring compound.
, Preferably in the range of 0.5 to 45% by weight, more preferably in the range of 3 to 40% by weight, in particular 5 to 45% by weight.
It is in the range of 25% by weight.

Examples of the binder include natural organic high molecular substances such as gelatin, cellulose derivatives, dextran, rosin and rubber; and hydrocarbon resins such as polyurethane, polyethylene, polypropylene, polystyrene and polyisobutylene; polyvinyl chloride Vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride / polyvinyl acetate copolymer; acrylic resins such as polymethyl acrylate and polymethyl methacrylate; polyvinyl alcohol, chlorinated polyethylene, epoxy resin, butyral resin, rubber derivatives And synthetic organic polymers such as precondensates of thermosetting resins such as phenol-formaldehyde resins. When a binder is used in combination as a material for the recording layer, the amount of the binder used is 0.2 to 20 parts by weight, preferably 0.5 to 10 parts by weight, and more preferably 1 to 100 parts by weight for the dye compound. -5 parts by weight. The concentration of the dye compound in the coating solution thus prepared is generally 0.1.
0.1 to 10% by weight, preferably 0.1 to 5% by weight.
% By weight.

Examples of the coating method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. The recording layer may be a single layer or a multilayer. The thickness of the recording layer (average thickness after drying) is generally 10 to 350 n.
m, preferably in the range of 30 to 250 nm. In the case of the optical information recording medium of the present invention, the thickness of the recording layer in the pre-groove is preferably in the range of 50 to 200 nm, more preferably in the range of 60 to 150 nm,
Particularly preferably, it is in the range of 65 to 120 nm. Further, the thickness of the land is preferably in the range of 30 to 150 nm, more preferably in the range of 40 to 120 nm, and particularly preferably in the range of 50 to 100 nm.

Through the above steps, the optical information recording medium of the present invention having a recording layer on a substrate can be manufactured.

The case where a reflective layer and a protective layer are provided will be described below. The reflective layer is generally provided on the recording layer or on the substrate for the purpose of improving the reflectance at the time of reproducing information. The light-reflective substance that is the material of the reflection layer is a substance having a high reflectance to laser light.
g, Se, Y, Ti, Zr, Hf, V, Nb, Ta, C
r, Mo, W, Mn, Re, Fe, Co, Ni, Ru,
Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, C
d, Al, Ga, In, Si, Ge, Te, Pb, P
Metals and semimetals such as o, Sn, Bi, and stainless steel can be mentioned. Preferred among these are Cr, Ni, Pt, Cu, Ag, Au, Al and stainless steel. These substances may be used alone, or in combination of two or more kinds, or as an alloy. Particularly preferred are Au, Ag, and alloys containing these metals. The reflective layer can be formed on the recording layer or on the substrate by, for example, vapor deposition, sputtering or ion plating of the above-mentioned reflective substance. The thickness of the reflective layer is generally 5 to 5
It is in the range of 00 nm, preferably in the range of 10 to 350 nm, more preferably in the range of 30 to 200 nm.

The protective layer is provided for the purpose of physically and chemically protecting the recording layer and the reflective layer. As a material used for the protective layer, for example, SiO, SiO ₂ , MgF
₂ , organic substances such as inorganic substances such as SnO ₂ and Si ₃ N ₄ , thermoplastic resins, thermosetting resins, and UV curable resins. The protective layer is preferably formed of a resin. When the protective layer is provided on the reflective layer, the protective layer
For example, a film obtained by extrusion of plastic
It can be formed by laminating on a reflective layer via an adhesive layer. Alternatively, the protective layer may be provided by a method such as vacuum deposition, sputtering, or coating. In the case of a thermoplastic resin or a thermosetting resin, a protective layer can be formed by dissolving these in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying. . In the case of a UV-curable resin, a coating solution is prepared as it is or dissolved in an appropriate solvent, and then the coating solution is applied and cured by irradiation with UV light to form a protective layer. Various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added to these coating solutions according to the purpose. The thickness of the protective layer is generally in the range of 0.05 to 70 μm.

Two laminates having a recording layer, a reflective layer, and, if desired, a protective layer provided on a substrate are prepared, and the two recording layers are bonded together with an adhesive or the like so that each recording layer faces inside. An optical information recording medium having a layer can be manufactured. Further, the obtained laminate and a disc-shaped protective substrate having substantially the same dimensions as the substrate of the laminate are bonded with an adhesive or the like so that the recording layer is on the inside, so that the recording layer is provided only on one side. An optical information recording medium can be manufactured. The bonding can be performed using the UV curable resin used for forming the protective layer, a synthetic adhesive, or a double-sided tape. The adhesive layer thus formed usually has a thickness of 0.05 to 70 μm (preferably 3 to 5 μm).
0 μm).

The information recording / reproducing method using the optical information recording medium of the present invention is carried out, for example, as follows. While rotating the optical information recording medium at a predetermined constant linear velocity (in the case of the CD format, a single speed of 1.2 to 1.4 m / sec) or a predetermined constant angular velocity, the semiconductor laser light is emitted from the substrate side or the protective layer side. A recording laser beam such as a laser beam is condensed through an optical system and irradiated on a recording layer. Due to the irradiation of the laser beam, the irradiated portion of the recording layer absorbs the light and locally raises the temperature,
Information is recorded by physical or chemical changes that alter its optical properties. In the present invention, a semiconductor laser beam having a red light oscillation wavelength in the range of 620 to 690 nm as recording light, and 390 to 440
A semiconductor laser beam having an oscillation wavelength of blue light or blue-violet light in the range of nm is used. The recording light is
It is preferable that the light is condensed through an optical system having an NA of 0.55 to 0.7.

To reproduce the information recorded as described above, the semiconductor laser light is irradiated from the substrate side or the protective layer side while rotating the optical information recording medium after recording at a predetermined constant linear speed. This is performed by detecting the reflected light. The optical information recording medium of the present invention can perform recording and reproduction using laser light having an oscillation wavelength in any of the above ranges. In the present invention, it is preferable to use a recording / reproducing method in which recording is performed using a semiconductor laser beam having a blue or blue-violet oscillation wavelength, and reproduction is performed using a semiconductor laser beam having a red oscillation wavelength. By using this method, for example, an optical information recording medium manufactured by recording image information using blue or blue-violet laser light as a recording light can be used as a dedicated reproduction system having the same oscillation wavelength as the recording light. There is an advantage that reproduction can be performed using a recording / reproducing system that is already widely used for DVD-R without using it.

[0044]

EXAMPLES Examples and comparative examples of the present invention will be described below.

Example 1 Production of a Disc-Shaped Substrate A polycarbonate (resin trade name: Panlite AD55) was prepared using an injection molding machine incorporating a stamper produced to have a predetermined track pitch and groove (pre-groove).
03, Teijin Limited) Disc-shaped resin substrate (120 m in diameter)
m, inner diameter 15 mm, thickness 0.6 mm). The track pitch of the concave groove (pregroove) of the obtained resin substrate is 0.48 μm, the depth of the groove is 90 nm, the width of the groove is 190 nm, and the inclination angle of the side wall of the groove (from the bottom of the groove to the depth of the groove). Formed by a straight line extension connecting a point on the side wall of the groove at 10% of the depth and a point on the side wall of the groove at 50% of the depth of the groove, and a horizontal plane on the bottom surface of the concave groove. Angle) was 60 °. The measurement of these shapes is based on AF
M.

[0046]

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The above dye was dissolved in 2,2,3,3-tetrafluoro-1-propanol so that the concentration of the dye in the solution was 1% by weight to prepare a coating solution for forming a recording layer. This coating solution is applied to the surface of the disc-shaped polycarbonate substrate obtained above, on which the pre-groove is provided, by spin coating, dried, and dried to form a recording layer (the thickness in the groove: 120 nm, the thickness of the land portion). The optical information recording medium (optical disk) according to the present invention was manufactured.

[Evaluation as Optical Information Recording Medium] (1) Using a recording / reproducing device described below, a rectangular wave signal having a constant linear velocity of 3.5 m / sec and a frequency of 1 MHz was applied to the obtained optical disk to record power. Recording was performed with the optimum recording power while varying from 3 to 10 mW. Recording / reproducing device: DDU1000 (manufactured by Pulstec) Laser: semiconductor laser having a blue-violet emission wavelength of 408 nm Pickup NA: 0.6 Rim intensity: tangential direction 0.33 Radial direction 0.21 Use circularly polarized beam Focus on the knife-edge method,
Tracking was performed using the push-pull method.
The refractive index n of the recording layer obtained with respect to the laser light having a wavelength of 408 nm was 2.2, and the extinction coefficient k was 0.05.

After recording, the recording signal was reproduced with a laser power of 0.5 mW using laser light having the same wavelength as the recording laser light, and the degree of modulation was measured. The degree of modulation is defined as A, the maximum value of the reflected light level of the DC reproduction waveform when the signal recorded under the above conditions is reproduced, and B, the minimum value of the reflected light level, when the groove tracking is performed in the unrecorded portion. R was determined from the following equation. Modulation degree (%) = (AB) / R × 100% As a result, a modulation degree of 62% was obtained.

(2) A semiconductor laser having a red emission wavelength of 638 nm was mounted on the recording / reproducing apparatus, and signals were recorded on an optical disk in the same manner as in (1). 63
The refractive index n of the recording layer obtained with respect to the laser beam having a wavelength of 8 nm was 2.3, and the extinction coefficient k was 0.1. Thereafter, reproduction was performed using laser light of the same wavelength, and the degree of modulation was measured in the same manner. As a result, a degree of modulation of 65% was obtained.

(3) After recording a signal using the semiconductor laser having a blue-violet emission wavelength of 408 nm, 638
When the recorded signal was reproduced using a semiconductor laser having a red emission wavelength of nm, the signal could be reproduced with high resolution.

[0052]

By using the optical information recording medium according to the present invention, recording and reproduction can be performed in the wavelength range of laser light for DVD-R and blue or blue-violet laser light. Moreover, the optical information recording medium according to the present invention exhibits good recording / reproducing characteristics with laser light in both wavelength ranges. Therefore, information recorded using a blue or blue-violet laser beam can be reproduced using a DVD-R laser beam. Further, by using blue or blue-violet laser light, higher-density recording becomes possible, and an optical information recording medium having a larger recording capacity can be manufactured.

[Brief description of the drawings]

FIG. 1 shows an absorption spectrum of a preferred dye compound used for a recording layer of an optical information recording medium of the present invention.

Claims (4)

[Claims] 1. An optical information recording medium having a recording layer containing a dye compound capable of recording information by irradiating a laser beam on a substrate, wherein the recording layer has a wavelength of 390 to 440 nm. And the reflectance for each of the laser beams having a wavelength in the range of 620 to 690 nm is 20% or more, and the absolute value k of the real part n and the imaginary part of the complex refractive index of the recording layer is n ≧ 1.8. And 0.02 <k <
An optical information recording medium formed so as to satisfy 0.5. 2. A dye compound having at least two absorption maximum wavelengths of a main absorption and a sub-absorption in an absorption curve thereof, and an end on the long wavelength side of the sub-absorption is 39.
The optical information recording medium according to claim 1, wherein the optical information recording medium is in a wavelength range of 0 to 440 nm. 3. The optical information recording medium according to claim 1, wherein the dye compound is a rhodocyanine compound represented by the following general formula. Embedded image [In the above general formula, R ¹ , R ² , R ³ , and R
⁴ are each independently a saturated or unsaturated alkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 4 and X ^- is an organic or inorganic counter ion. ] 4. After recording the information by irradiating the optical information recording medium according to claim 1 with a laser beam having a wavelength in the range of 390 to 440 nm, the optical information recording medium has a wavelength of 620 to 6 nm.
An optical information recording / reproducing method, wherein information is reproduced by irradiating a laser beam having a wavelength in a range of 90 nm.