JPH08118799A - Optical recording medium - Google Patents

Abstract

PURPOSE: To record or reproduce with infrared laser having a specific wavelength and to reproduce or record and reproduce even with a near infrared laser having another specific wavelength by incorporating azo compound having the absorption maximum in the wavelength of a specific range represented by a special formula in a recording layer. CONSTITUTION: An optical recording medium comprises a recording layer 2, a reflecting layer 3 and a protective layer 4 on a board 1, wherein the medium contains azo compound having the absorption maximum in the wavelength of 450 to 630nm represented by a formula in the layer 2. The medium contains the compound represented by a formula and optical absorbent having the absorption maximum in the wavelength of 650 to 900nm in the layer 2. The weight ratio of the absorbent having the maximum in the wavelength of 650 to 900nm is 0.1 to 50%. The reflectivity measured from the side of a board 1 to the beam selected from the red laser having the wavelength of 620 to 690nm is 20% or more. and the medium can reproduce the red laser having the wavelength of 620 to 690nm.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an optical recording medium, particularly recording / reproducing with a red laser having a wavelength of 620 to 690 nm.
The present invention also relates to an optical recording medium that can be reproduced or recorded / reproduced by a near infrared laser having a wavelength of 770 to 830 nm.

[0002]

2. Description of the Related Art As an optical recording medium having a reflective layer on a substrate, a recordable or recordable CD corresponding to the compact disc (hereinafter abbreviated as CD) standard has been proposed [eg Nikkei Electronics, No. 465, P.I. 10
7, January 23, 1989]. This optical recording medium is shown in FIG.
The recording layer 2, the reflective layer 3, and the protective layer 4 are formed on the substrate 1 as shown in FIG.
Are formed in this order. When the recording layer of this optical recording medium is irradiated with a laser beam such as a semiconductor laser with high power, the recording layer undergoes a physical or chemical change,
Record information in the form of pits. Information on the pits can be reproduced by irradiating the formed pits with low-power laser light and detecting the reflected light. Generally, a wavelength of 770 to 830 nm is used for recording / reproducing of such an optical recording medium.
The near-infrared semiconductor laser is used and conforms to the CD standard of Red Book, Orange Book, etc., and therefore has the feature of being compatible with CD players and CD-ROM players.

Recently, development of semiconductor lasers having a wavelength shorter than 770 nm has progressed, and red semiconductor lasers having wavelengths of 680 nm and 630 nm have been put into practical use [eg Nikkei Electronics, No. 592, P.I. 65, 1993
October 11, issue]. By reducing the beam spot by shortening the wavelength of the recording / reproducing laser, a high-density optical recording medium becomes possible. Large-capacity optical recording media capable of storing moving images have been developed by shortening the wavelength of semiconductor lasers and data compression technology [eg, Nikkei Electronics, No. 589, P.P. 55, August 30, 1993]. Such a high-density optical recording medium can record a large amount of data such as a moving image, and is expected to be used for a video CD and the like [eg, Nikkei Electronics, No. 594, P.I. 169, November 8, 1993]. Further, in JP-A-2-278519, 68
780nm with high sensitivity recording with 0nm short wavelength laser
High-sensitivity and high-speed recording has been proposed by the method of reproducing by.

On the other hand, Japanese Patent Laid-Open No. 6-40162 proposes an optical recording medium capable of recording / reproducing with a short wavelength laser. This medium uses an indocarbocyanine dye in the recording layer, and a 630 nm semiconductor laser or He.
Recording is possible with a Ne laser. A 490 nm blue / green semiconductor laser having a wavelength shorter than 630 nm has also been studied, but has not yet reached the stage of practical application [eg, Applied Physics Letter,
P. 1272-1274, Vol. 59 (1991) and "Nikkei Electronics" No. 552, P.I. 90,1
April 27, 1992]. From such a background, the recording / reproducing wavelength of the optical recording medium tends to be shortened to around 630 nm. Therefore, it is necessary to develop an optical recording medium corresponding to this, and further, a compatible optical recording medium compatible with the conventional 780 nm is also desired.

[0005]

However, in the conventional optical recording medium, the organic dye used in the recording layer has a wavelength of 6
It was found that the absorption was large at 20 to 690 nm and the refractive index was small, so that the reflectance was low and reproduction with a red laser having a wavelength of 680 nm or 630 nm was impossible. An object of the present invention is to provide an optical recording medium capable of recording / reproducing with a red laser having a wavelength of 680 or 630 nm and capable of reproducing or recording / reproducing with a near-infrared laser having a wavelength of 780 nm (such as a commercially available CD player). It is in.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have proposed the present invention. That is, this problem is solved by the following invention. The present invention provides an optical recording medium having a recording layer, a reflective layer and a protective layer on a substrate, wherein the recording layer has the formula (1)
An optical recording medium containing an azo compound having an absorption maximum at a wavelength of 450 to 630 nm represented by [Chemical Formula 2],

[0007]

Embedded image (In the formula, n = 1 or 2, R _{1 to} R ₄ are hydrogen atoms, substituted or unsubstituted alkyl groups, alkoxy groups, hydroxy groups, carboxyl groups, halogen atoms, allyl groups, alkylcarboxyl groups, alkylalkoxyl groups, It is selected from an aralkyl group, an alkylcarbonyl group, a sulfonate alkyl group bonded to a metal ion, a nitro group, an amino group, an alkylamino group, a phenyl group, and a phenylethylene group, which may be the same or different. X and Y are CH ₂ , C = O,
It is selected from S, Se, O and NH and may be the same or different. ) A wavelength of 6 in the recording layer together with the compound represented by the formula (1)
An optical recording medium also containing a light absorbing agent having an absorption maximum at 50 to 900 nm, and having a wavelength of 650 to 900 nm.
The weight ratio of the light absorber having the absorption maximum in 0.1 to 50
% Optical recording medium and also has a wavelength of 620 to 690.
The reflectance measured from the substrate side to the light selected from the red laser of 20 nm is 20% or more, and the wavelength is 620 to 69.
The optical recording medium is at least reproducible with a 0 nm red laser, and the reflectance measured from the substrate side for light selected from the red laser with a wavelength of 620 to 690 nm is 20% or more. It is an optical recording medium that can be recorded and reproduced by a red laser, and the reflectance measured from the substrate side for light selected from a near infrared laser having a wavelength of 770 to 830 nm is 65% or more, and is selected from 770 to 830 nm. Is an optical recording medium that can be reproduced by a near-infrared laser with a wavelength of 77
It is an optical recording medium that can be recorded and reproduced by a near infrared laser selected from 0 to 830 nm, and has a wavelength of 620 to 69.
The reflectance measured from the substrate side with respect to the light selected from the 0 nm red laser is 20% or more, and the wavelength is 620 to 6
It is an optical recording medium that can be reproduced by a 90 nm red laser.

According to the present invention, the wavelength of 620 to 690 can be obtained by using the above-mentioned azo compound or a mixture of the azo compound and a compound having an appropriate light absorption in the recording layer.
It is possible to record and reproduce with a red laser of nm, and
An optical recording medium capable of reproduction or recording / reproduction with a laser selected from 830 nm is realized.

The specific structure of the present invention will be described below. The optical recording medium of the present invention has a recording layer and a reflective layer on a substrate. The optical recording medium refers to both a read-only optical read-only medium in which information is recorded in advance and an optical recording medium in which information can be recorded and reproduced. However, here, as a suitable example, an optical recording medium capable of recording and reproducing the latter information, particularly an optical recording medium in which a recording layer, a reflective layer and a protective layer are formed in this order on a substrate will be described. This optical recording medium has a four-layer structure as shown in FIG. That is, the recording layer 2 is formed on the substrate 1, the reflective layer 3 is provided in close contact therewith, and the protective layer 4 further covers the reflective layer 3 thereon.

The substrate material may basically be transparent at the wavelengths of recording light and reproducing light. For example, a polymer material such as a polycarbonate resin, a vinyl chloride resin, an acrylic resin such as polymethylmethacrylate, a polystyrene resin, an epoxy resin, or an inorganic material such as glass is used. These substrate materials are formed into a disk shape by injection molding or the like. If necessary, grooves may be formed on the surface of the substrate.

A recording layer is formed on the substrate. In the present invention, a dye composed of an azo compound represented by the formula (1) [Chemical Formula 3] is used in the recording layer. That is, the azo dye of the present invention has a λ _max of around 500 nm,
Since the refractive index at ˜690 nm is large and the absorbance is small, a large reflectance can be obtained. Also, since the refractive index at 770 to 830 nm is large and the absorption is small, a CD equipped with a semiconductor laser of 770 to 830 nm currently used is installed.
It can be played on a player or a CD-ROM player.

[0012]

Embedded image In the formula, n = 1 or 2, R _{1 to} R ₄ are hydrogen atoms,
Substituted or unsubstituted alkyl group, alkoxy group, hydroxy group, carboxyl group, halogen atom, allyl group, alkylcarboxyl group, alkylalkoxyl group, aralkyl group, alkylcarbonyl group, sulfonate alkyl group bonded to a metal ion, nitro group, It is selected from an amino group, an alkylamino group, a phenyl group and a phenylethylene group, and may be the same or different. X and Y are CH ₂ , C =
It is selected from O, S, Se, O and NH and may be the same or different, but among these, CH ₂ and C═O are preferable. In the present invention, the content ratio of the azo compound in the recording layer is not particularly limited, but is usually about 30 to 100% by weight.

In the present invention, in order to improve the recording sensitivity with respect to 630 to 690 nm and 770 to 830 nm, 60
A light absorber with a maximum absorption wavelength of 0 to 900 nm is 0.1
They may be mixed in a weight ratio of -50%, preferably 1-25%. If this light absorber is mixed in too much, 630
There is a possibility that the absorption coefficient of the dye film in the range of ˜690 nm and 770 to 830 nm becomes large and the reflectance of the reproducing characteristic is lowered. If the addition amount is too small, 6
The absorption coefficient of the dye film at 30 to 690 nm and 770 to 830 nm is too small, and the effect of improving recording sensitivity is not sufficient.

Examples of such light absorbers include heptamethine cyanine dyes, pentamethine cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, azo dyes, squarylium dyes, pyrylium dyes, and thiopyrylium dyes. , Azurenium dye, naphthoquinone dye, anthraquinone dye, indophenol dye, triphenylmethane dye, xanthene dye, indanthrene dye, indigo dye, thioindigo dye, merocyanine dye, thiazine dye, There are acridine-based dyes, oxazine-based dyes, and the like, but any one having a maximum absorption wavelength in the range of 600 to 900 nm and capable of being mixed with the azo dye described above may be used. Further, a plurality of these dyes may be mixed and used. Among them, a phthalocyanine dye represented by [Chemical Formula 4] or [Chemical Formula 5],

[0015]

[Chemical 4]

[0016]

Embedded image 1,3,3,1 ', 3', 3'-hexamethyl-2,
2 '-(4,5,4', 5'-dibenzo) indodicarbocyanine perchlorate, 3,3'-diethyl-2,
2 '-(6,7,6', 7'-dibenzo) thiadicarbocyanine iodide, 3,3'-diethyl-2,2 '
-Thiadicarbocyanine iodide, 1,1'-diethyl-2,2'-quinodicarbocyanine iodide,
3,3'-Diethyl-2,2'-selenadicarbocyanine iodide, 1,3'-diethyl-4,2'-quinoxadicarbocyanine iodide, 3,3 ', 9-
Triethyl-2,2 '-(4,5,4', 5'-dibenzo) thiadicarbocyanine bromide, 1,1'-diethyl-2,4'-quinodicarbocyanine iodide,
1,3'-diethyl-4,2'-quinothiadicarbocyanine iodide and the like are preferable. If necessary, additives such as a quencher, an ultraviolet absorber and a combustion accelerator can be mixed or introduced as a substituent into the dye. For example, as the additive, the following general formula (2)
(8) Examples include those represented by [Chemical Formula 6] to [Chemical Formula 12].

[0017]

[Chemical 6]

[0018]

[Chemical 7]

[0019]

Embedded image

[0020]

[Chemical 9]

[0021]

[Chemical 10]

[0022]

[Chemical 11]

[0023]

[Chemical 12] (However, A and A ′ are an atomic group forming a benzene ring or a substituted benzene ring or forming a naphthalene ring or a substituted naphthalene ring, and may be the same or different. May be singular or plural, but is an alkyl group, an alkoxy group, a hydroxy group, a carboxyl group, a halogen atom, an allyl group, an alkylcarboxyl group, an alkylalkoxyl group, an aralkyl group, an alkylcarbonyl group, a metal ion. And a sulfonate alkyl group, a nitro group, an amino group, an alkylamino group, a phenyl group, a phenylethylene group, etc. R _{9 to} R ₃₁ are substituted or unsubstituted alkyl groups, alkoxy groups, hydroxy groups, carboxyl groups,
Examples include a halogen atom, an allyl group, an alkylcarboxyl group, an alkylalkoxyl group, an aralkyl group, an alkylcarbonyl group, a sulfonatealkyl group bonded to a metal ion, a nitro group, an amino group, an alkylamino group, a phenyl group, and a phenylethylene group. M is Ni, Co,
Transition metals such as Mn, Cu, Pd and Pt are shown. M may have a charge and may have a salt structure with a cation. a'represents the valence of an ionic body and is a positive integer including 0. Z represents a cation, a ′ = b ′ · c ′, and when a ′ = 0, b ′ · c ′ = 0 and Z does not exist, and the compound becomes a neutral body. These dyes have a thickness of 50 to 500 nm, preferably 100 to 150, on a substrate by a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, a vacuum vapor deposition method or the like.
to form a recording layer of nm. Particularly in the coating method, a coating solvent in which a dye is dissolved or dispersed is used, and it is preferable to select a solvent that does not damage the substrate. For example, alcohol solvents such as methanol, aliphatic hydrocarbon solvents such as hexane and octane, cyclic hydrocarbon solvents such as cyclohexane, aromatic hydrocarbon solvents such as benzene, halogenated hydrocarbon solvents such as chloroform, An ether solvent such as dioxane, a cellosolve solvent such as methyl cellosolve, a ketone solvent such as acetone, an ester solvent such as ethyl acetate, and the like are used alone or in combination. Further, the recording layer is not limited to one layer, and a plurality of dyes may be formed in multiple layers, or the dyes may be dispersed in a polymer thin film or the like, preferably about 50% or more. When a solvent that does not damage the substrate cannot be selected, sputtering, chemical vapor deposition, vacuum vapor deposition, etc. are effective.

Next, on the recording layer, a thickness of 50 to 300 nm,
Preferably, a reflective layer having a thickness of 100 to 150 nm is formed. The material of the reflective layer has a sufficiently high reflectance at the wavelength of the reproduction light, such as Au, Al, Ag, Cu, Ti, Cr,
Metals of Ni, Pt, Ta, Cr and Pd can be used alone or as an alloy. Among these, Au
And Al have a high reflectance and are suitable as a material for the reflective layer.
Other than the above, the following may be included. For example,
Mg, Se, Hf, V, Nb, Ru, W, Mn, Re,
Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, I
Metals and semimetals such as n, Si, Ge, Te, Pb, Po, Sn and Bi can be mentioned. Further, a material containing Au as a main component is preferable because a reflective layer having a high reflectance can be easily obtained. Here, the main component means that the content rate is 50% or more. A low refractive index thin film and a high refractive index thin film are alternately stacked with a material other than metal to form a multilayer film,
It can also be used as a reflective layer.

As a method of forming the reflective layer, for example,
The sputtering method, the chemical vapor deposition method, the vacuum vapor deposition method, etc. are mentioned.
Further, a reflection amplification layer or an adhesive layer may be provided between the recording layer and the reflection layer in order to increase the reflectance or improve the adhesion. The present invention thus obtained is a medium in which a recording layer and a reflective layer are formed on a substrate.
The reflectance from the substrate side with respect to the light of the wavelength selected from the range of 690 nm is 20% or more, preferably 30% or more, and the reflectance from the substrate side with respect to the light of the wavelength selected from the range of 770 nm to 830 nm. Has 65% or more, preferably 70% or more, and the Red Book (C
D) Standard and Orange Book (CD-R) standard reflectance are satisfied. If these standards are satisfied, it can be satisfactorily reproduced even by a CD player that has been commercially available in the past.

Further, a protective layer may be formed on the reflective layer. The material of the protective layer is not particularly limited as long as it protects the reflective layer from external force. Examples of the organic substance include a thermoplastic resin, a thermosetting resin, a UV curable resin, and the like. Among them, UV curable resin is preferable. Further, as the inorganic substance, SiO ₂ , SiN ₄ , Mg
F _2, SnO ₂ and the like. A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in a suitable solvent, applying a coating solution, and drying. The UV curable resin can be formed as it is or by dissolving it in a suitable solvent to prepare a coating solution, applying the coating solution, and irradiating it with UV light to cure it. As the UV curable resin, for example, an acrylate resin such as urethane acrylate, epoxy acrylate, polyester acrylate can be used. These materials may be used alone or as a mixture, and may be used not only as a single layer but also as a multilayer film. As a method of forming the protective layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used as in the recording layer, and among them, the spin coating method is preferable.

The red laser used in the present invention is 630 to 630.
Any laser having a wavelength of 690 nm may be used. For example, there are dye lasers capable of wavelength selection in a wide range of the visible region, helium neon lasers having a wavelength of 633 nm, high-power semiconductor lasers having a wavelength of 680 nm and semiconductor lasers having a wavelength of 635 nm which have been recently developed. And semiconductor lasers are preferred. Also,
The near infrared laser may be any laser having a wavelength of 770 to 830 nm, but a commercially available CD player or CD
The semiconductor laser used in the recorder is suitable.

[0028]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. [Example 1] 0.2 g of the azo dye (A) represented by the formula (1) and [Table 1] and a pentamethine cyanine dye NK2929 (1, 3, 3, 1 ', 3', 3 ') as a light absorber. -Hexamethyl-2,2 '-(4,5,4', 5'-dibenzo) indodicarbocyanine perchlorate) (manufactured by Japan Photosensitive Dye Research Institute) 0.02 g was added to 10 ml of diacetone alcohol (Tokyo Kasei). Dissolve and prepare a dye solution. The substrate is made of polycarbonate resin and has a continuous guide groove (track pitch: 1.6 μm) and a diameter of 120 m.
A disk-shaped one with mφ and a thickness of 1.2 mm was used. A dye solution was spin-coated on this substrate at a rotation speed of 1500 rpm and dried at 70 ° C. for 2 hours to form a recording layer. On this recording layer, a Balzers sputtering device (CDI-90
0) was used to sputter Au to form a reflective layer having a thickness of 100 nm. Argon gas was used as the sputtering gas. The sputtering conditions were sputtering power of 2.5 kW and sputtering gas pressure of 1.0 × 10 ^-2 Torr. Further, an ultraviolet curable resin SD-17 (manufactured by Dainippon Ink and Chemicals, Inc.) was spin-coated on the reflective layer and then irradiated with ultraviolet rays to form a protective layer having a thickness of 6 μm. Optical disk evaluation device DDU-1000 and KENWOOD manufactured by Pulstec Industrial Co., Ltd. equipped with a 680 nm red semiconductor laser head.
Linear velocity of 5.6 m / s, using an EFM encoder manufactured by
Recording was performed with a laser power of 10 mW. 635n after recording
m A signal was reproduced using an evaluation device equipped with a red semiconductor laser head, and the reflectance was measured. Further, the recorded sample was subjected to reproduction evaluation with a commercially available CD player having a reproduction wavelength of 780 nm, and the error rate was measured.

[0029]

[Table 1]

Example 2 In Example 1, the formula (1)
An optical recording medium was prepared in the same manner except that the azo dye (B) shown in [Table 1] was used. An optical disk evaluation device D manufactured by Pulstec Industrial Co., in which the manufactured medium was mounted with a 680 nm red semiconductor laser head as in Example 1
Linear velocity of 5.6 m / s, laser power of 10 using DU-1000 and EFM encoder manufactured by KENWOOD
Recorded in mW. After recording, the same measurement as in Example 1 was performed.

[Embodiment 3] In Embodiment 1, the formula (1)
An optical recording medium was prepared in the same manner except that the azo dye (C) shown in [Table 1] was used. The manufactured medium is an optical disk evaluation device DDU-1000 and K manufactured by Pulstec Industrial Co., Ltd., which is equipped with a 780 nm semiconductor laser head.
Recording was performed at a linear velocity of 2.8 m / s and a laser power of 10 mW using an EFM encoder manufactured by ENWOOD. After recording, the same measurement as in Example 1 was performed.

Example 4 The azo dye (A) and the pentamethine cyanine dye NK2929 (1, in Example 1)
3,3,1 ', 3', 3'-hexamethyl-2,2'-
0.2 g of the phthalocyanine dye represented by [Chemical Formula 5] on the dye layer formed by (4,5,4 ', 5'-dibenzo) indodicarbocyanine perchlorate) (manufactured by Japan Photosensitive Dye Research Institute) N-Octane (Tokyo Kasei) 10m
An optical recording medium was prepared in the same manner except that a dye film was formed under the same conditions by a spin coating method using a dye solution dissolved in 1 and the recording layer was composed of two layers. The optical disk evaluation device D manufactured by Pulstec Industrial Co., in which the manufactured medium was mounted with a 780 nm semiconductor laser head as in Example 3
Linear velocity 2.8 m / s, laser power 10 using DU-1000 and EFM encoder manufactured by KENWOOD
Recorded in mW. After recording, the same measurement as in Example 1 was performed.

Comparative Example 1 The dye used in Example 1 was the pentamethine cyanine dye NK2929 (1, 3, 3, 3).
1 ', 3', 3'-hexamethyl-2,2 '-(4
An optical recording medium was prepared in the same manner except that 5,4 ′, 5′-dibenzo) indodicarbocyanine perchlorate) (manufactured by Japan Photosensitive Dye Research Institute) was used. An optical disk evaluation device D manufactured by Pulstec Industrial Co., in which the manufactured medium was mounted with a 680 nm red semiconductor laser head as in Example 1
Linear velocity of 5.6 m / s, laser power of 10 using DU-1000 and EFM encoder manufactured by KENWOOD
Recorded in mW. After recording, the same measurement as in Example 1 was performed.

Comparative Example 2 The dye used in Example 1 was the pentamethinecyanine dye NK2627 (3,3'-diethyl-2,2 '-(6,7,6', 7'-dibenzo) thiadicarbocyanine aio. An optical recording medium was prepared in the same manner except that Dyed) (manufactured by Japan Photosensitive Dye Research Institute) was used. The produced medium was recorded at a linear velocity of 5.6 m / s and a laser power of 10 mW by using an optical disk evaluation device DDU-1000 manufactured by Pulstec Industrial Co., Ltd. equipped with a 680 nm red semiconductor laser head and an EFM encoder manufactured by KENWOOD as in Example 1. did. After recording, the same measurement as in Example 1 was performed.

Comparative Example 3 The dye used in Example 1 was pentamethinecyanine dye NK1456 (1,1′-diethyl-2,2′-quinodicarbocyanine iodide).
An optical recording medium was prepared in the same manner except that [manufactured by Japan Photosensitive Dye Research Institute] was used. The produced medium was recorded at a linear velocity of 2.8 m / s and a laser power of 10 mW using an optical disc evaluation device DDU-1000 manufactured by Pulstec Industrial Co., Ltd. equipped with a 780 nm semiconductor laser head and an EFM encoder manufactured by KENWOOD as in Example 6. . After recording, the same measurement as in Example 1 was performed. These results are summarized in [Table 2].

[0036]

[Table 2]

[0037]

According to the present invention, by using a dye composed of an azo compound as a recording layer, recording / reproducing can be performed by a near-infrared laser of 780 nm which has been conventionally used, and it has been shifting in recent years. , The wavelength is 635 nm or 6
It is possible to provide a compatible optical recording medium capable of recording and reproducing even with a red laser of 80 nm.

[Brief description of drawings]

FIG. 1 is a cross-sectional structure diagram of an optical recording medium.

[Explanation of symbols]

 1 substrate 2 recording layer 3 reflective layer 4 protective layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location G11B 7/24 516 7215-5D (72) Inventor Sumio Hirose 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Keisuke Takuma 1190, Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Denmi Misawa 1190, Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Chemical Within the corporation

Claims (8)

[Claims] 1. An optical recording medium having a recording layer, a reflective layer and a protective layer on a substrate, wherein the recording layer has the formula (1)
And an optical recording medium containing an azo compound having an absorption maximum at a wavelength of 450 to 630 nm. Embedded image (In the formula, n = 1 or 2, R _{1 to} R ₄ are hydrogen atoms, substituted or unsubstituted alkyl groups, alkoxy groups, hydroxy groups, carboxyl groups, halogen atoms, allyl groups, alkylcarboxyl groups, alkylalkoxyl groups, It is selected from an aralkyl group, an alkylcarbonyl group, a sulfonate alkyl group bonded to a metal ion, a nitro group, an amino group, an alkylamino group, a phenyl group, and a phenylethylene group, which may be the same or different. X and Y are CH ₂ , C = O,
It is selected from S, Se, O and NH and may be the same or different. ) 2. The optical recording medium according to claim 1, wherein the recording layer also contains a light absorber having an absorption maximum at a wavelength of 650 to 900 nm together with the compound represented by the formula (1). 3. The optical recording medium according to claim 2, wherein the weight ratio of the light absorber having an absorption maximum at a wavelength of 650 to 900 nm is 0.1 to 50%. 4. The reflectance measured from the substrate side with respect to light selected from a red laser having a wavelength of 620 to 690 nm is 2.
The optical recording medium according to any one of claims 1 to 3, which is 0% or more and is at least reproducible by a red laser having a wavelength of 620 to 690 nm. 5. The reflectance measured from the substrate side with respect to light selected from a red laser having a wavelength of 620 to 690 nm is 2.
The optical recording medium according to any one of claims 1 to 3, which is 0% or more and can be recorded and reproduced by a red laser having a wavelength of 620 to 690 nm. 6. The reflectance measured from the substrate side with respect to the light selected from the near infrared laser having a wavelength of 770 to 830 nm is 65% or more, and the light can be reproduced by the near infrared laser selected from 770 to 830 nm. The optical recording medium according to claim 1. 7. The optical recording medium according to claim 1, which is recordable and reproducible with a near infrared laser having a wavelength of 770 to 830 nm. 8. The reflectance measured from the substrate side for light selected from a red laser having a wavelength of 620 to 690 nm is 2.
The optical recording medium according to any one of claims 1 to 3 or claim 6, which is 0% or more and is reproducible with a red laser having a wavelength of 620 to 690 nm.