JP3365623B2 - Information recording and playback method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium capable of recording (writing) and reproducing (reading) information using a laser beam having a high energy density, and more particularly, a laser used for recording and reproducing information. The present invention relates to an information recording medium having excellent performance in which the variation in performance is small with respect to variations in the wavelength of light, and an optical information recording / reproducing method for recording / reproducing information on / from the medium by light.

[0002]

2. Description of the Related Art In recent years, information recording media using a high energy density beam such as laser light have been developed and put into practical use. This information recording medium is called an optical disc, and is used as a video disc, an audio disc, a large-capacity still image file, a large-capacity computer disk memory, and the like.

The basic structure of an optical disk is a disk-shaped substrate made of glass, synthetic resin or the like, and a metal or semimetal such as Bi, Sn, In, Te, etc. provided on this substrate; or a cyanine-based or metal complex-based substrate. And a recording layer made of a dye such as quinone. Incidentally, on the surface of the substrate on which the recording layer is provided, usually, from the viewpoint of improving the flatness of the substrate, improving the adhesive force with the recording layer, or improving the sensitivity of the optical disk,
An intermediate layer of polymeric material is often provided.

For the purpose of improving the durability of the information recording medium, a protective layer is provided on the recording layer, or as a disc structure, the recording layer is formed on at least one of the two disc-shaped substrates. And an air sandwich structure in which the two substrates are bonded to each other via a ring-shaped inner spacer and a ring-shaped outer spacer so that the recording layer is located inside and a space is formed. . In an optical disk provided with such a protective layer or an optical disk having an air sandwich structure, the recording layer does not come into direct contact with the outside air, and recording and reproduction of information is performed by laser light passing through the substrate. Has an advantage that it is not physically or chemically damaged, or dust is not attached to the surface thereof to hinder information recording or reproduction.

Recording of information on the optical disc and reproduction of information from the optical disc are usually performed by the following method. Information is recorded by irradiating the optical disk with a laser beam, and the irradiated portion of the recording layer absorbs the light and locally rises in temperature, causing a physical or chemical change (for example, in a pit). Is generated),
Information is recorded by changing its optical properties.
Information is also reproduced by irradiating the optical disk with a laser beam, and the information is reproduced by detecting reflected light or transmitted light according to the change in the optical characteristics of the recording layer.

As described above, metals and dyes are known as recording materials for forming the recording layer of such an information recording medium. The information recording medium using a dye has advantages in characteristics of the recording medium itself such as high sensitivity as compared with a recording material such as metal, and the recording layer can be easily formed by a coating method. It has a great advantage over. However, the recording layer made of a dye generally has a drawback that it is difficult to obtain a C / N having a low reflectance or a high reflectance.

Recording of information on the recording layer made of a dye is performed by forming pits in the dye recording layer.
As described above, the dye has high sensitivity, but requires a relatively large recording power to form a complete pit. That is, since a large recording power is required to obtain a recording signal of high C / N, it cannot be said that the sensitivity is really high in many cases. Further, in order to improve the low reflectance which is a defect of the dye recording layer, when a reflective layer is provided,
There is a problem that it becomes more difficult to form pits in the dye recording layer.

Further, the dyes generally used in the dye recording layer are those whose reflectance and transmittance change depending on the wavelength of the laser beam used for recording and reproducing information, and are used for conventional information recording media. The dye is a laser light whose reflectance fluctuation falls within a specific range (for example, ± 10% range) centered on the reflectance at a predetermined (predetermined) wavelength of the laser light. The range of wavelength variation is very narrow, and is generally within about ± 2% around a predetermined (predetermined) wavelength. That is, when the wavelength of the laser light used for recording and reproducing information deviates from the range of about ± 2%, the reflectance of the dye recording layer of the information recording medium changes significantly. Therefore, when the wavelength of the laser beam used for recording or reproducing information deviates a little from a predetermined (predetermined) wavelength, the reflectance of the dye recording layer of the information recording medium is greatly reduced, which results in recording and recording of information. In some cases, a reproduction error may occur, and in some cases, it may be impossible to record and / or reproduce information.

[0009]

DISCLOSURE OF THE INVENTION According to the present invention, a recording layer containing a dye is provided on a substrate, the fluctuation of the performance is small with respect to the variation of the wavelength of the laser beam used for recording and reproducing the information, and It reduces errors during recording and reproduction, has stable and excellent performance, has a wide allowable range of the wavelength of the laser light used, and there are few off-grade products.
It is also an object of the present invention to provide an information recording medium that can be manufactured with high productivity. The present invention also records information on the information recording medium by light with almost no error,
An object is to provide an optical information recording / reproducing method for reproducing.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides a dye recording layer and a metal capable of recording and reproducing information by a laser beam having a predetermined wavelength on a disk-shaped substrate having a tracking guide provided on the surface thereof. After recording information by irradiating the above-mentioned laser beam on an information recording medium in which a reflective layer having a layer thickness of 100 to 3000Å and a protective layer are laminated in this order,
An optical information recording / reproducing method comprising reproducing recorded information, wherein the information recording medium is a laser beam having a wavelength shifted within a range of ± 3% around the wavelength of the laser beam. The information recording / reproducing method is characterized in that the information recording medium is used in which the fluctuation of the reflectance of the recording medium is within a range of ± 10% around the reflectance with respect to the laser beam having the predetermined wavelength. On the way. Information of the present invention
In the information recording / reproducing method, the dye recording layer is used as the information recording medium.
However, the thickness is 1300Å, and the thickness is 130
When 0Å gold reflective layer is laminated, 740-870nm
The reflectance is 74 to 9 for the laser light of the wavelength within the range of
Information recording medium that is a dye recording layer that varies only within the range of 0%
It is preferable to use the body.

The preferred embodiments of the information recording medium used in the present invention are as follows. 1) An information recording medium in which the shift range of laser light having a wavelength shifted around the wavelength of the laser light is within ± 5%. 2) The dye in the recording layer is a cyanine dye, azurenium dye, squarylium dye, phthalocyanine dye, pyrylium dye, thiopyrylium dye, indophenol dye, indoaniline dye, triphenylmethane dye, quinone dye. , An aminium-based dye, a diimmonium-based dye, a metal complex salt-based dye, etc., and the reflection of the recording medium with respect to a laser beam having a wavelength shifted within a range of ± 3% around the wavelength of the laser beam. An information recording medium comprising one or two or more dyes capable of having a fluctuation of the ratio within a range of ± 10% centering on the reflectance with respect to the laser light of the predetermined wavelength.

3) The recording layer further contains a metal complex dye in an amount of 0.001 to 1 part by mole of the above dye or dye mixture.
An information recording medium containing 0.2 part by mole. 4) An information recording medium in which the layer thickness of the recording layer is in the range of 500 to 2000Å. 5) The reflective layer is made of Au, Ag, Cu, Pt, Cr, Ti,
It is made of at least one metal or alloy selected from the group consisting of Al and stainless steel.

6) The thickness of the reflective layer is 500 to 2000Å
Information recording medium in the range of. 7) An information recording medium in which a protective layer is provided on the reflective layer. 8) An information recording medium in which the substrate material is polycarbonate, polyolefin or cell cast polymethylmethacrylate. 9) The predetermined wavelength of the laser light is 780-830.
Information recording medium in the range of nm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The information recording medium of the present invention has a basic structure in which a recording layer and a reflecting layer containing one or more kinds of dyes having specific properties are sequentially provided on a disk-shaped substrate.

The substrate is preferably a substrate made of plastic, and this plastic can be arbitrarily selected from various materials used as the substrate of the conventional information recording medium. Substrate optical properties, planarity,
From the viewpoints of processability, handleability, stability over time, and manufacturing costs, examples of substrate materials include acrylic resins such as cell cast polymethylmethacrylate and injection-molded polymethylmethacrylate; polyvinyl chloride, vinyl chloride copolymer, etc. Vinyl chloride resin; epoxy resin; polycarbonate resin, amorphous polyolefin, and polyester. Preferred are polycarbonate, polyolefins and cell cast polymethylmethacrylate.

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, improving solvent resistance of the substrate and preventing alteration of the recording layer. Good. Examples of the material of the undercoat layer include polymethylmethacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol,
N-methylolacrylamide, styrene / sulfonic acid copolymer, styrene / vinyltoluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, Polymeric substances such as ethylene / vinyl acetate copolymer, polyethylene, polypropylene, and polycarbonate; organic substances such as silane coupling agents; and inorganic oxides (SiO ₂ , Al ₂ O)
₃ etc.), and inorganic substances such as inorganic fluoride (MgF ₂ ).

The undercoat layer is prepared by, for example, dissolving or dispersing the above materials in a suitable solvent to prepare a coating solution, and then applying the coating solution to the substrate by a coating method such as spin coating, dip coating or extrusion coating. It can be formed by applying to the surface. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably 0.0
It is in the range of 1 to 10 μm.

A tracking guide is provided on the substrate (or undercoat layer). That is, generally, a pregroove layer and / or a prepit layer is provided for the purpose of forming a groove for tracking or unevenness representing information such as an address signal. As a material for the pregroove layer or the like, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetraester and a photopolymerization initiator can be used.

To form the pre-groove layer, first, a precisely prepared mother die (stamper) is coated with a mixed solution of the above-mentioned acrylic ester and a polymerization initiator, and the substrate is further coated on this coating solution layer. After mounting, a method of irradiating ultraviolet rays through the substrate or the master to cure the liquid layer to fix the substrate and the liquid layer, and then peeling the substrate from the master can be used. By the method, a substrate having a pre-groove layer is obtained. The layer thickness of the pregroove layer is generally in the range of 0.05 to 100 μm, preferably 0.
It is in the range of 1 to 50 μm. When the substrate material is plastic, pregrooves and / or prepits may be provided directly on the substrate by injection molding or extrusion molding.

A recording layer containing a dye capable of recording (writing) and reproducing (reading) information by a laser beam is provided on the tracking guide provided on the substrate, and a reflection layer made of metal is further provided thereon. Layers are provided and constitute the information recording medium of the present invention. The present invention is characterized in that the dye in the recording layer and the reflective layer are provided on the dye recording layer.

That is, the dye in the recording layer of the information recording medium of the present invention has a reflectance of the information recording medium with respect to a laser beam having a wavelength shifted within a range of ± 3% around the wavelength of the laser beam. Of the laser beam having the predetermined wavelength can be adjusted within the range of ± 10%.

Further, in the information recording medium of the present invention,
The fluctuation of the reflectance of the information recording medium with respect to the laser light having a wavelength shifted within ± 5% around the wavelength of the laser light is reflected by the laser light with the predetermined wavelength. It is preferably within a range of ± 10% centering on the rate.

In this specification, the reflectance of the information recording medium is a value measured by a regular specular reflection measuring method.

In an information recording medium having a recording layer containing a dye as described above and a reflective layer provided thereon,
Even if the reflectance of the medium changes due to a change in the reflectance of the dye, if the changed reflectance is within ± 10% of the predetermined reflectance, errors during recording and reproducing of information are substantially Does not happen. However, the laser light that is generally used for recording and reproducing information is scattered within a range of about ± 3% around the set wavelength, and the color of the dye changes depending on the change in the wavelength of the laser light. The reflectance changes, and the reflectance of the recording layer of the information recording medium also changes accordingly. When the reflectance fluctuates greatly (for example, more than ± 10%) in response to a very slight change in the wavelength of the laser light (for example, ± 2% range) as in a conventionally known information recording medium, An error will occur when recording or reproducing information.

In the information recording medium of the present invention, the fluctuation of the reflectance of the information recording medium with respect to the laser light having a wavelength shifted within ± 3% with respect to the wavelength of the laser light used for recording and reproduction is centered. , The reflectance of the laser beam having the predetermined wavelength is centered within ± 10%, in other words, the variation range of the reflectance is the reflection at the predetermined wavelength. Since the range of variation of the wavelength of the laser light within the range of ± 10% of the ratio is a wide range of ± 3% of the predetermined wavelength of the laser light used for recording and reproduction. In addition, even when using a laser beam that is generally used for recording and reproducing information and has a variation in wavelength, it is possible to reliably record and reproduce information without any error.

In the information recording medium of the present invention, ± 5 is centered around the wavelength of the laser beam having the above predetermined wavelength.
% Variation in the information recording medium with respect to the laser light having a wavelength shifted within the range of 10% (particularly within the range of ± 10%), the reflectance with respect to the laser light with the predetermined wavelength. It is preferable to be within ± 10% with respect to the center.

Further, in the information recording medium of the present invention, the change of the transmittance with respect to the variation of the wavelength of the laser light also affects the performance of the information recording medium, though the change of the reflectance of the dye is not so large.

The dyes having the above-mentioned properties used in the recording layer of the information recording medium of the present invention include, for example, cyanine dyes, azurenium dyes and squarylium dyes,
Selected from phthalocyanine dyes, pyrylium dyes, thiopyrylium dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, quinone dyes, aminium dyes, diimmonium dyes, metal complex dyes (ie , Which is preferable as a dye in the recording layer of the information recording medium), and the fluctuation of the reflectance of the information recording medium with respect to the laser light having a wavelength shifted within ± 3% around the wavelength of the laser light is ± 1 centering on the reflectance with respect to the laser light of the predetermined wavelength
It is a dye that can be adjusted to fall within the range of 0%, and may be a single dye or a mixture of two or more dyes.

As a single dye having the above properties, for example, a dye represented by the following formula (I) can be mentioned.

[0030]

[Chemical 1]

The dye represented by the above formula (I) is 740 to
For a wavelength in the range of 870 nm (805 nm ± 8%), when gold is laminated as the reflective layer, the reflectance is 74.
It is a dye that varies only in the range of 90% to 90% (82% ± 10%).

When a cyanine dye is used, it is preferable to use the above metal complex dye or aminium-diimmonium dye together as a quencher.
In that case, as a quencher, it is preferable that 0.001 to 0.2 part by mole of a metal complex salt type dye is contained with respect to 1 part by mole of all the dyes.

To form the recording layer, the above dye and, if desired, a binder are dissolved in a solvent to prepare a coating solution, and then the coating solution is applied to the surface of the substrate to form a coating film and then dried. Can be done by.

Examples of the solvent for preparing the dye coating solution include esters such as ethyl acetate, butyl acetate and cellosolve acetate, ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone, dichloromethane, 1,2.
Halogenated hydrocarbons such as dichloroethane and chloroform, ethers such as tetrahydrofuran, ethyl ether and dioxane, alcohols such as ethanol, n-propanol, isopropanol and n-butanol, amides such as dimethylformamide, 2,2,3,3 Fluorine-based solvents such as 3-tetrafluoropropanol may be mentioned. In addition, these non-hydrocarbon-based organic solvents,
A hydrocarbon solvent such as an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, or an aromatic hydrocarbon solvent may be contained as long as it is within 50% by volume.

Various additives such as an antioxidant, a UV absorber, a plasticizer and a lubricant may be further added to the coating liquid depending on the purpose.

When the binder is used, the binder is
For example, gelatin, cellulose derivatives such as nitrocellulose and cellulose acetate, natural organic polymer substances such as dextran, rosin and rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene and polyisobutylene, polyvinyl chloride and polyvinylidene chloride. , Vinyl-based resins such as polyvinyl chloride / polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyolefins, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde Mention may be made of synthetic organic polymeric substances such as precondensates of thermosetting resins such as resins.

Examples of the coating method include spraying method, spin coating method, dipping method, roll coating method, blade coating method, doctor roll method and screen printing method. In order to form a good alignment state of the dye, it is preferable to use the spin coating method. Furthermore, during spin coating, the spinner rotation speed is set to 500 to 500.
0r. p. m. And the drying time is 1 to 60
It is preferable to carry out in the range of seconds for promoting good orientation of the dye.

When a binder is used as a material of the recording layer, the ratio of the dye to the binder is generally 0.01 to 9.
It is in the range of 9% (weight ratio), preferably 1.0 to 95.
% (Weight ratio).

The layer thickness of the dye recording layer is generally 200 to 30.
It is in the range of 00Å, preferably 500 to 2000Å.

In the information recording medium of the present invention, a reflective layer is provided on the recording layer. By providing the reflective layer, it is possible to obtain the effect of improving the reflectance, the effect of improving the S / N ratio when reproducing information, and the effect of improving the sensitivity during recording.

Materials for the reflective layer include Mg, Se, Y,
Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W,
Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, I
r, Pt, Cu, Ag, Au, Zn, Cd, Al, G
a, In, Si, Ge, Te, Pb, Po, Sn, Bi
Mention may be made of metals and semi-metals such as Further, it may be an alloy such as stainless steel. In the present invention,
High thermal conductivity at a temperature of 400K, at least 10
It is preferable to provide a reflective layer made of a metal having a w / m · k or more. As a result, heat generated when the dye recording layer is irradiated with laser light can be rapidly conducted to the reflective layer.
Among these, Au, Ag, Cu, Pt, Al, Cr,
Ni and stainless steel are particularly preferred. These substances may be used alone, in a combination of two or more, or as an alloy.

The reflective layer can be formed on the dye recording layer by vapor deposition, sputtering or ion plating of a light reflective substance. The layer thickness of the reflective layer is generally in the range of 100 to 3000Å, preferably in the range of 500 to 2000Å.

A protective layer is provided on the reflective layer for the purpose of physically and chemically protecting the recording layer and the entire information recording medium. The protective layer also has the effect of enhancing scratch resistance and moisture resistance on the side of the substrate on which the recording layer is not provided.

Examples of materials used for forming the protective layer include SiO, SiO ₂ , Si ₃ N ₄ , and
Mention may be made of MgF _2, SnO ₂ and the like. Examples of the organic substance include a thermoplastic resin, a thermosetting resin, a UV curable resin, and the like, and a UV curable resin is preferable. In the present invention, a remarkable effect can be obtained when the above substance is provided by coating. It is particularly effective when the above organic substance is provided by coating.

That is, it can also be formed by dissolving a thermoplastic resin, a thermosetting resin or the like in a suitable solvent to prepare a coating solution, coating the coating solution, and then drying. In the case of a UV curable resin, it can also be formed by preparing a coating solution as it is or by dissolving it in an appropriate solvent, applying this coating solution, and irradiating it with UV light to cure it. UV curable resins include urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate and other (meth) acrylate oligomers, (meth) acrylic acid ester and other monomers, and further photopolymerization. Conventional UV curable resins such as initiators can be used. In these coating liquids, an antistatic agent, an antioxidant, U
Various additives such as V absorber may be added depending on the purpose. In the present invention, it is preferable to use a UV curable resin.

The layer thickness of the protective layer is generally 0.1 to 100 μm.
It is in the range of m.

In addition to the above, the protective layer can be formed, for example, by laminating a film obtained by extrusion processing of plastic on the dye recording layer via an adhesive layer. Alternatively, it may be provided by a method such as vacuum vapor deposition, sputtering, and coating.

[0048]

[Example] [Example 1] The following structural formula:

[0049]

[Chemical 2]

The dye having the above is dissolved in 2,2,3,3-tetrafluoropropanol to prepare a recording layer coating solution (dye concentration:
2.0% by weight) was prepared. Disc-shaped polycarbonate substrate with tracking guide (outer diameter: 130m
m, inner diameter: 15 mm, thickness: 1.2 mm, track pitch: 1.6 μm, groove depth: 800 Å), the above coating solution was spin-coated at a rotation speed of 500 rpm. p.
m. Coating at a speed of 1 hour and drying for 30 seconds to obtain a film thickness of 1300
A dye recording layer of Å was formed. Au on top of this dye recording layer
Was subjected to DC sputtering to form a reflective layer having a layer thickness of 1300Å.

On the reflective layer, a UV curable resin (manufactured by ThreeBond, trade name: 3070) was used as a protective layer by a spin coating method at a rotation speed of 850 rpm. p. m. After coating at a speed of 1, the coating was irradiated with ultraviolet rays from a high-pressure mercury lamp and cured to form a protective layer having a layer thickness of 3 μm, to manufacture an information recording medium comprising a substrate, a recording layer, a reflective layer and a protective layer.

The obtained information recording medium was measured according to the following evaluation method using a spectrophotometer at a wavelength of 780 n.
The fresh reflectance and C / N were measured at m, 805 nm and 830 nm. The results are shown in Table 1.

[Evaluation of Information Recording Medium] A semiconductor laser beam having a predetermined wavelength (805 nm) was used as an information recording medium, a constant linear velocity was 1.3 m / sec, a recording power was 6 mW, and a modulation frequency was 720 kHz. A single signal (duty: 33%) was recorded.

(Reflectance) The fresh reflectance obtained above corresponds to the reflectance in the area where no pit is formed on the information recording medium after recording. .

(C / N) The information recorded under the above conditions is
Reproduction power 0.5m using laser light of wavelength 780nm
The ratio (C / N) of carrier and noise output levels was measured with a spectrum analyzer (RBW: 10 kHz, VBW: 100 Hz) at W and a constant linear velocity of 1.3 m / sec.

[Comparative Example 1] A dye having the following structural formula:

[0057]

[Chemical 3]

With a dye having a dye density of 2.7
The coating liquid for the recording layer was prepared by changing the amount to 5% by weight, and the rotation number at the time of coating by the spin coating method was 1000 rpm. p. m. An information recording medium was manufactured in the same manner as in Example 1 except that

Regarding the obtained information recording medium, Example 1
Evaluation was made in the same manner as in. The results are shown in Table 1.

[0060]

[Table 1]                                 Table 1 ────────────────────────────────────                               Reflectance C / N ──────────────────────────────────── Laser wavelength 780nm 805nm 830nm 780nm ──────────────────────────────────── Example 1 79% 82% 85% 52 dB Comparative Example 1 67% 80% 91% 51 dB ────────────────────────────────────

As is clear from the results in Table 1, when the wavelength of the laser light varies by 805 nm ± about 3%, the reflectance of the information recording medium obtained in Comparative Example 1 is 80%, While it varies in the range of 16.3% to + 13.8%, the reflectance of the information recording medium obtained in Example 1 is -3.7% to + 3.7% with respect to 82%. The fluctuation range of the reflectance is extremely small. Also,
Also for C / N, the predetermined wavelength (805 nm)
The information recording medium obtained in Example 1 is superior to the information recording medium obtained in Comparative Example 1 when reproduced with a laser beam having a shorter wavelength of 780 nm.

[0062]

The information recording medium of the present invention is stable in that the fluctuation of the reflectance is small with respect to the variation in the wavelength of the laser beam used for recording and reproducing information, and the error during recording or reproducing of information is reduced. It is an information recording medium that has excellent performance and has a remarkably excellent effect that it can be manufactured with high productivity with few things to be off-grade due to the wide allowable range of the wavelength of laser light used.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masao Yabe               Fuji-Sha, 200, Onakazato, Fujinomiya-shi, Shizuoka Prefecture               Shin Film Co., Ltd. (72) Inventor Mitsuru Sawano               Fuji-Sha, 200, Onakazato, Fujinomiya-shi, Shizuoka Prefecture               Shin Film Co., Ltd.                (56) Reference JP-A-1-136786 (JP, A)                 JP-A-63-231987 (JP, A)                 JP-A-61-27291 (JP, A)

Claims (2)

(57) [Claims] 1. A dye recording layer capable of recording and reproducing information by a laser beam having a predetermined wavelength on a disk-shaped substrate having a tracking guide provided on the surface, and made of a metal.
An information recording medium in which a reflective layer having a layer thickness of 100 to 3000 Å and a protective layer are laminated in this order is irradiated with the laser beam to record information, and then the light is formed by reproducing the recorded information. An information recording / reproducing method, wherein, as the information recording medium, a change in reflectance of the recording medium with respect to a laser beam having a wavelength shifted within a range of ± 3% around the wavelength of the laser beam, An information recording / reproducing method characterized by using an information recording medium within a range of ± 10% centering on a reflectance with respect to a laser beam having a predetermined wavelength. 2. As an information recording medium, when a dye recording layer has a thickness of 1300Å and a gold reflecting layer having a thickness of 1300Å is laminated thereon, a laser beam having a wavelength in the range of 740 to 870 nm is obtained. On the other hand, the information recording / reproducing method according to claim 1, wherein the information recording medium is a dye recording layer whose reflectance changes only in a range of 74 to 90%.