JPH02202484A - Optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an optical recording medium on which information can be written and read by changing the aggregation state of molecules in an optical recording layer by irradiation with a laser beam.

TECHNICAL BACKGROUND OF THE INVENTION AND PROBLEMS There have been various known optical recording media that record and read information using laser beams. One method is to irradiate the recording layer on the substrate with a laser beam,
Optical recording media are known that perform recording by causing changes such as melting, evaporation, and decomposition in the irradiated area.

For example, JP-A-57-82093, JP-A-58-
56892, JP 60-89842, JP 60-150243, etc. disclose a transparent substrate,
An optical recording medium is disclosed that includes an optical recording layer formed of an organic dye thin film layer provided on this substrate. Irradiation is used to write and read information. In such an optical recording medium, microscopic pits are easily formed in the optical recording layer by melting, evaporating, decomposing, or the like the organic dye by irradiation with a semiconductor laser.

However, in the above-mentioned optical recording medium, recording is performed by forming pits in the optical recording layer that change the shape of the recording layer, so when recording is repeatedly performed on this optical recording medium, the recording characteristics change significantly. There was a problem that it was decreasing. Furthermore, in order to obtain stable signal strength, high laser power is required, and there is also the problem of poor sensitivity.

The inventors of the present invention conducted intensive research to solve the above-mentioned problems, and found that an optical recording layer made of a cyanine dye and a deformation suppressing layer of the optical recording layer are provided in this order on a transparent substrate. When the optical recording layer is irradiated with a recording laser, pits (holes) are not formed in the optical recording layer, but the state of aggregation of the dye changes and recording is performed. The present invention has been completed based on the discovery that this method is possible, and therefore has excellent repeat recording characteristics and that stable signal strength can be obtained even with low recording laser power.

Purpose of the Invention The present invention is an attempt to solve the problems associated with the prior art as described above, and is directed to forming pits (holes) in the optical recording layer when the optical recording layer is irradiated with a recording laser. Optical recording that does not record data, but instead records by changing the aggregation state of the dye in the optical recording layer, has excellent repeat recording characteristics, and can obtain stable signal intensity even with low recording laser power. The purpose is to provide a medium.

Summary of the Invention The optical recording medium according to the present invention has an optical recording layer made of a cyanine dye and a deformation suppressing layer of the optical recording layer on a transparent substrate.
It is characterized by being provided in this order.

DETAILED DESCRIPTION OF THE INVENTION First, a first optical recording medium according to the present invention will be specifically described.

In the present invention, the transparent substrate used is a substrate that has a light transmittance of 85% or more for writing or reading information and has small optical anisotropy, which is commonly used as a substrate for optical recording media. It will be done. Specific examples of such transparent substrates include glass, acrylic resin, polycarbonate resin, polyester resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, polystyrene resin, and polyolefin resin such as poly4-methylpentene. , US Pat. No. 4,614,778, a substrate made of a thermoplastic resin such as an amorphous polyolefin resin or a polyethersulfone resin, or a thermosetting resin such as an epoxy resin or an allyl resin is used. Among these, it is preferable to use an amorphous polyolefin resin substrate because of the variety of solvents that can be used when dissolving the dye.

The thickness of such a transparent substrate is not particularly limited, and its shape may be a plate, a film, a circle, or a card, and there are no particular restrictions on its size. There isn't. In addition, the transparent substrate is usually provided with guide grooves for position control during recording and reading, and unevenness for preformatting such as address signals and various marks. It can be applied using a stun bar or the like when molding the thermoplastic resin by injection molding, compression molding, or the like.

The optical recording medium according to the present invention has an optical recording layer and a deformation suppressing layer of the optical recording layer provided in this order on a transparent substrate as described above, and this recording layer contains a cyanine dye. has been done.

As the cyanine dye, a compound represented by the following formula [11] is used.

Φ-L-ma (X) ... [1] In the above formula [I], Φ and Taira represent an indole ring or a thiazole ring to which an aromatic ring such as a benzene ring, a naphthalene ring, or a phenanthrene ring may be fused. , oxazole ring, selenazole ring, imidazole ring, pyridine ring, etc.

These Φ and Ma may be the same or different, but are usually the same, and in some cases, various substituents may be bonded to these rings. Note that in Φ, the nitrogen atom in the ring has a positive charge, and in Sato, the nitrogen atom in the ring is neutral.

As these Φ and the lower skeletal ring, the following can be specifically exemplified.

Φ 3 Φ Φ4 (R4) 9 Φ 5 Φ 6 Φ 7 Φ Φ In such a ring, the group R (RS
R") is a substituted or unsubstituted alkyl group or aryl group.

In such a ring, groups R, R' bonded to the nitrogen atom
The number of carbon atoms is preferably 8 to 18 from the viewpoint of facilitating changes in the aggregation state. In addition, when R and R' further have a substituent, such substituents include a sulfonic acid group, an alkylcarbonyloxy group, an alkylamide group, an alkylsulfonamide group, an alkoxycarbonyl group, an alkylamino group, an alkylcarbamoyl group. group, an alkylsulfamoyl group, a hydroxyl group, a carboxy group, a halogen atom, and the like.

Note that when m, which will be described later, is 0, the group R1 bonded to the nitrogen atom in Φ is a substituted alkyl group or an aryl group and has a negative charge.

Further, when the rings Φ and Ma are fused or non-fused indole rings (formulas Φ1 to Φ4), two substituents R1R3 are preferably bonded to the 3-positions thereof. In this case, the two substituents bonded to the 3-position are preferably an alkyl group or an aryl group.

Among these, unsubstituted alkyl groups having 1 or 2 carbon atoms are preferred, and unsubstituted alkyl groups having 1 carbon atom are particularly preferred.

On the other hand, at a predetermined position in the ring represented by Φ and W,
Furthermore, another substituent R4 may be bonded. Examples of such substituents R4 include alkyl groups, aryl groups, heterocyclic residues, halogen atoms, alkoxy groups, alkylthio groups, alkyloxycarbonyl groups, alkylcarbonyloxy groups, and carboxylic acid groups. The number of these substituents (p, q, 'rs+t) is usually about 0 or 1 to 4. In addition, pr Q+ r+
When Sr t is 2 or more, a plurality of R4s may be the same or different from each other. Among these,
Those having a fused or non-fused indole ring of formulas (Φ1) to (Φ4) are preferred. Optical recording media in which Φ and M are such cyanine-based dyes have excellent coating properties and stability, exhibit extremely high reflectance, and have a high C/C ratio for information readout.
The N ratio becomes extremely high.

In formula [1], L represents a linking group for forming a mono-, di-, tri- or tetracarbocyanine dye,
In particular, any one of the following formulas (Ll) to (L=1+) is preferable.

Formula (L 1 ) C11-CH-CIl-CI-C-C
Il-CH-CII-C) + formula (R2-C11-C
H-CH-C-CI -C11-C11 formula (L 7 )
CH-CH-C-CH-CH formula (L8) Cl-
C-Cl1-CI! Formula (R9) Formula (L10) In the above formula, Y represents a hydrogen atom, a monovalent group, or an atom other than a hydrogen atom. In this case, the groups 111IIi or atoms other than hydrogen atoms include lower alkyl groups such as methyl groups, lower alkoxy groups such as methoxy groups, dimethylamino groups, diphenylamino groups, methylphenylamino groups, morpholino groups, and imidazolidine groups. , di-substituted amino groups such as ethoxycarbonylbiverazine groups, alkylcarbonyloxy groups such as acetoxy groups, alkylthio groups such as methylthio groups, cyano groups, nitro groups, Br, Cjll
Preferred are halogen atoms such as.

Examples include dyes such as

Further, R and R9 each represent a hydrogen atom or a lower alkyl group such as a methyl group. And g is 0 or 1.

1゜Among the above formulas (Ll) to (L-8''), tricarbocyanine linking groups are preferred, particularly those of formula (R2) or formula (
A linking group represented by R3) is preferred.

In the above formula [I], X is an anion, and as a preferable example, IBr and m are 0 or 1
However, when m is 0, R1 of Φ usually has a negative charge and becomes an inner salt.

Specific examples of cyanine dyes used in the present invention include (Dl) to (D58) in Table 1.
Although cyanine dyes as described above are preferably used in the optical recording layer, organic dyes as described in numbers (1) to (6) below can also be used. Number (1) below
When using the organic dye (6), the same effect as when using a cyanine dye can be obtained by laminating a deformation suppressing layer on the optical recording layer made of such a dye. An optical recording medium is obtained.

(1) Croconium dye (2) Azulene dye However, X represents a chromophore, M represents a cation, and YO represents an anion; however, when an anion is contained in the chromophore, YO shall not exist.

RSR, RSR and R5 represent a hydrogen atom, an alkyl group, an alkoxy group, or a substituted or unsubstituted aryl group.

(3) Triphuedithiazine compound However, R and R2 may be the same or different and represent a hydrogen atom or a halogen atom, respectively, but may include an alkyl group, an alkoxy group, a carboxy group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, etc. It may be substituted with one or more groups and sulfonic acid groups.

(4) Tetradehydrocholine compound where R represents an alkyl group or carbalkoxy group, such as -COOCR, R1 represents a hydrogen atom, an alkyl group, etc., and M represents H, Ni (■), Co (II)
, Co (m), etc., and X is Br5C
Represents Ω04, etc.

(5) Dioxazine compounds and derivatives thereof a) Condensation ring-closing reaction produced between aromatic amines and fluoranil, chloranil, bromanyl, iodoanyl, where A represents a residue of an unsubstituted or substituted aromatic amine, and X represents -F, -C
It represents fl, -Br, -■.

(H3CH3, where X represents -F, -Cfl, -Br, -1, and R represents -H, -No, -NH2, -OCH, -Q
CH, -F-Cfl-Br, -1. It represents an aromatic group, etc., and m and n represent integers of 1 to 4.

(6) Anthraquinone derivative This derivative can be represented by the following structural formulas [I] and [II].

Structural formula [I hydrogen atom, alkyl group, hydroxyl group, nitro group,
represents an amino group, a cyano group and a halogen atom, Y represents a hydrogen atom and a sulfonate group, Ar1 represents a hydrogen atom, a phenyl group, a naphthyl group and their sulfonates and salts, and the phenyl group represents an alkyl group, an alkoxy may be substituted by amino groups, alkylcarbonyl groups, methylthio groups, halogens and phenylcarbonyl groups. Ar2 represents a hydrogen atom, a phenyl group, or a sulfonated product or salt thereof, and the phenyl group may be substituted with an alkyl group, an alkoxy group, an amino group, an alkylcarbonyl group, a phenylcarbonyl group, or a halogen atom.

Structural formula [11] However, x Sx Sx and X4 are the above [I
], X5 is a hydrogen atom and -N
represents H-A r 1, Z is a hydrogen atom, -NH-A
r and −S −A r t, and Ar
t has the same meaning as in the case of [I] above.

In particular, compounds having an indanthrene skeleton, such as the structural formula [nl, have a maximum absorption wavelength around 800 nm, and are therefore optimal as semiconductor laser irradiation type optical recording materials.

Examples of anthraquinone derivatives represented by the above structural formulas [1] and [1] are shown below.

That is, l-amino-4-(4-sulfonic acid phenylamino)-6,7-sinitroanthraquinone sodium salt, 1-anilino-2-sulfonic acid sodium-4-(
4-methylphenylamino)anthraquinone, 8.17
-bis-(4-methoxyphenylamino)-indanthrene, 1,4-bis(3-sulfonate sodium-4-
methoxyphenylamino)-8,7-dicyazanthraquinone, ■,4-bis-3-sulfonate sodium-4
-chlorophenylamino)-5,8-dichloroanthraquinone, sodium 1-(2-methylphenylamino)-2-sulfonate-4-(4-aminophenylamino)
-6,7-sinitroanthraquinone, 1,4-bis(3
-Sodium sulfonate-4-anilino-1-anthraquinolyl amino)benzene, 1,4-bis(4-(4-
Examples include sodium sulfonate (phenylamino)-1-anthraquinolyl amino)benzene.

Further, the optical recording layer of the optical recording medium according to the present invention may contain a polymer binder, if necessary. Examples of such polymeric binders include vinyl chloride resins, acrylic resins, polyester resins, polyamide resins, polycarbonate resins, epoxy resins, methacrylic resins, vinyl acetate resins, nitrocellulose, and phenol resins. When using such a polymer binder, the content of the polymer binder in the optical recording layer should be 10% by weight or less because the polymer binder may inhibit thermal movement and scooking of dye molecules. It is preferable that

The thickness of the optical recording layer formed on the transparent substrate is preferably 10 μm or less, preferably 500 to 2 μm.

In the optical recording medium according to the present invention, a deformation suppressing layer for the optical recording layer is provided on the optical recording layer as described above.

Specifically, the deformation suppressing layer of the optical recording layer is SiO, S10. Oxides such as ZnO, SiN
, A, 9N, nitrides such as TiN, SiC, Tic
So-called dielectric materials such as carbides, thermoplastic resins, and thermosetting resins, chalcogen compounds including T es S e s S, etc., semiconductors made of Ge5Si compounds, gold, silver, body, platinum, aluminum, cobalt, nichrome Metals such as are used.

Among these, dielectrics and semiconductor materials with low thermal conductivity are particularly preferred due to the influence of heat diffusion of laser light. Moreover, these layers can also be used by stacking several layers.

The thickness of the deformation suppressing layer of the optical recording layer is 0.01 to 10 μm.
m is preferably about 0.02 to 1.0 μm.

By providing the deformation suppressing layer for the optical recording layer as described above on the optical recording layer, pits (holes) are not formed in the optical recording layer when the optical recording layer is irradiated with a recording laser beam. Instead, the aggregation state of the cyanine dye contained in the optical recording layer changes, making it possible to perform recording.

Further, in the present invention, a layer for suppressing deformation of the optical recording layer as described above may be provided between the transparent substrate and the optical recording layer, and a layer for suppressing deformation of the optical recording layer as described above can be provided between the transparent substrate and the optical recording layer. By providing the suppression layer, it is possible to further suppress the change in shape of the optical recording layer when the optical recording layer is irradiated with a recording laser beam.

Next, a method for manufacturing an optical recording medium according to the present invention will be explained.

First, a cyanine dye as described above is dissolved or dispersed in an organic solvent to prepare a dye solution. In this case, as the organic solvent, an organic solvent having a low boiling point, preferably 200°C or lower, more preferably 150°C or lower, is used.

Specifically, the following organic solvents are used.

(i) Alcohols such as methanol, ethanol, 1-propanol,
1-butanol, isobutyl alcohol, tart-butyl alcohol, -pentanol, etc.

(i) Ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone and the like.

(i) Amides such as dimethylformamide, dimethylacetamide, etc.

(1v) Sulfoxides For example, dimethyl sulfoxide.

(V) Ethers such as diethyl ether, dipropyl ether, dibutyl ether, etc.

(vl) Esters For example, ethyl acetate, propyl acetate, etc.

(Vi) Aliphatic halogenated hydrocarbons such as 1,2-dichloroethane, methyl chloride, carbon tetrachloride, chloroform, dichlorobenzene and the like.

(■) Aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene.

These organic solvents may be used alone or in a mixture at a certain ratio.

Further, a polymer binder may be added to the dye solution as described above, if necessary.

Next, the optical recording layer according to the present invention can be formed by applying the dye solution prepared as described above onto a transparent substrate and drying to remove the organic solvent from the dye film. To apply the dye solution onto a transparent substrate,
For example, a spin code method, a dip method, a spray method, etc. can be employed.

In the present invention, the recording layer thus formed on the transparent substrate can also be heat-treated at 80 to 280°C, preferably 100 to 250°C, by external heating.

The heating time varies greatly depending on the heating temperature, but is usually preferably about 30 seconds to 90 minutes, more preferably about 3 to 60 minutes. There are no particular restrictions on the method of heating the recording layer from the outside, including a method using a heating oven, a method of bringing the recording layer into contact with a heating roll or a hot plate, a method of irradiating the recording layer with infrared rays using an infrared lamp,
A method such as heat pressing can be adopted.

It is preferable to heat-treat the recording layer at a temperature of 80 to 280°C in this manner because the optical properties and stability of the recording layer may be improved. It is presumed that this is because the state of molecular assembly inside the recording layer becomes more dense by heat-treating the recording layer.

The heat treatment of the recording layer is preferably carried out in an inert atmosphere such as nitrogen gas or an oxygen-containing atmosphere such as air.

After the recording layer is heat-treated at a temperature of 80 to 280°C as described above, the absorption wavelength of the recording layer is shifted to the longer wavelength side by exposing the recording layer to the vapor of an organic solvent such as chloroform, tetrahydrofuran, or toluene. In some cases, the sensitivity to light in the oscillation wavelength range of the semiconductor laser can be significantly improved.

Next, on the recording layer provided on the substrate as described above,
At least one deformation suppressing layer of the optical recording layer is formed by a dry film forming method such as a vacuum evaporation method, a sputtering method, a plasma CVD method, an ion blating method, a spin cord method, a dip method, a spray method, a roll method, etc. provided by

In order to record on the optical recording medium obtained as described above, the recording layer may be irradiated with a laser beam focused to about 1 μm, preferably a semiconductor laser beam. The aggregation state of the dye in the area irradiated with laser light changes, allowing information to be recorded. To reproduce the information recorded on the recording layer in this way, a laser beam or the like is irradiated to the area where information is recorded and the area where no information is recorded, and the difference in reflectance between them is read. It is carried out by

In the optical recording medium according to the present invention, information can be written again by slowly irradiating the recorded portion with a weak laser beam or by rapidly irradiating the recording area with a strong laser beam. In the optical recording medium according to the present invention, when the optical recording layer is irradiated with a recording laser, recording is performed by changing the aggregation state of the dye in the recording layer instead of forming pits in the optical recording layer. Therefore, repeated recording is possible using the method described above.

The laser beam irradiated to the recording layer when reproducing information must have a lower energy than the laser beam used when writing information on the recording layer, and must not change the aggregation state of the recording layer when reproducing information. is preferred.

Various lasers such as a He--Ne laser, an Ar laser, and a semiconductor laser can be used for writing or reproducing information on the recording layer, but semiconductor lasers are particularly preferred in terms of cost and size. As a semiconductor laser, the center wavelength is 830 nm, 780 nm
nm and shorter wavelength lasers can be used.

Effects of the Invention The optical recording medium obtained according to the present invention can be repeatedly recorded, and moreover, stable signal intensity can be obtained with low recording laser power.

[Examples] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 In Table 1, the dye number (D 57
), 2.0 parts by weight of this dye was dissolved in dichloroethane, and the resulting solution was spun onto a grooved disk substrate injection-molded amorphous polyolefin resin using a spin cord method. Number 80 Orpm is 90
A film was formed to a thickness of 0.03 mm to form an optical recording layer. On this recording layer, a film of 5102 was formed to a thickness of about 100 microns by sputtering, and a film of ultraviolet curable resin was formed to a thickness of 1.0 microns by a spin code method at a rotational speed of 40 Orpm. After that, the ultraviolet curing resin was cured using an ultraviolet lamp to obtain an optical recording medium.

Example 2 In Example 1, as the dye, the dye number (
An optical recording medium was obtained in the same manner as in Example 1 except that the dye represented by D58) was used.

Comparative Example 1 An optical recording layer was formed on a substrate in the same manner as in Example 1 using the dye shown by dye number (A1) in Table 1 as the dye to obtain an optical recording medium.

Note that at this time, a deformation suppressing layer of the optical recording layer was not formed on the optical recording layer.

The optical recording medium obtained as described above was evaluated as follows.

Evaluation: Using a semiconductor laser with a wavelength of 830 runs, a disk linear velocity of 9.4 m/s, and a recording frequency of 1. QMHz, 1~
The optical recording media of Example 1.2 and Comparative Example 1 were irradiated with a laser at an intensity of 10 mW to record information. After this,
The signal was read with a power of 0.6 mW.

FIG. 1 shows the relationship between recording laser power and signal intensity.

It can be seen from FIG. 1 that the optical recording medium according to the present invention provides a stable signal strength from the beginning of writing, compared to the conventional recording medium using the perforation method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between recording laser power and signal intensity of an optical recording medium according to the present invention and an optical recording medium according to a comparative example.

Claims (1)

[Claims] 1) An optical recording medium characterized in that an optical recording layer made of a cyanine dye and a deformation suppressing layer of the optical recording layer are provided in this order on a transparent substrate.