JPH06251418A - Optical recording medium - Google Patents

Abstract

PURPOSE:To effectively record and erase information without causing pit formation by laser light by using a mixture film of a compd. expressed by specified formula and an org. compd. having specified melting point as an optical recording film. CONSTITUTION:The optical recording medium consists of a laminated body of transparent substrate/org. dye recording film/reflecting film. Pits are formed not by the change of states due to thermal energy produced by laser light absorbed in the recording film but by change of transmittance of light in the wavelength region of reproducing laser light. The org. dye recording film is a mixture film of laminated films of a phthalocyanine compd. expressed by formula I and an org. compd. having 140-250 deg.C melting point. In formula, X1-X4 are independenly halogen atoms or various groups containing formula II, M is H2, bivalent metal or hydrogen atom, halogen atom, oxygen atom, or metal of formula III having hydroxyl groups, and 11-14 are numbers of substituents of X1-X4, respectively, and are independently 0-2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium on which information can be written, read and erased by a laser beam.

[0002]

2. Description of the Related Art Conventionally, there are various media for recording information by using a laser beam. One of them is an organic dye as a recording film, and laser light is recorded on a substrate. By irradiating the layer, the irradiated part is locally heated, and the optical characteristics of the recording film, especially the transmittance of the reproduction laser beam, can be obtained without causing physical or chemical changes such as melting, evaporation, sublimation or decomposition. Some use changes to record information.

[0003]

However, in these recording media, the recording film material itself is decomposed, evaporated, sublimated,
Although there is no chemical change due to melting or the like and there is no formation of pits, the phenomenon itself is almost irreversible and it can only be used in write-once recording media. That is, it is impossible to erase the recorded information and record new information again.

[0004]

Means for Solving the Problems As a result of intensive investigations, the present inventors have found that an optical recording medium using an organic dye for recording information by using a laser beam is used as a recording film. By irradiating the recording layer on the substrate, the irradiated part is locally heated, without causing physical or chemical changes such as melting, evaporation, sublimation or decomposition, and the optical characteristics of the recording film, especially the reproduction laser beam. Information is recorded by utilizing the change in transmittance of
Further, the inventors have found a constitution in which recording can be erased by irradiating a laser having an output slightly higher than the recording laser power, and completed the present invention.

That is, the present invention comprises a laminated body of a transparent substrate / organic dye recording film / reflection film, and heat energy generated by absorption of light energy of recording laser light incident from the transparent substrate by the recording film. Recording by utilizing only the optical characteristics of the recording film, that is, the phenomenon that the light transmittance in the reproduction laser light wavelength region reversibly changes, without the formation of pits due to changes in the state of decomposition, melting, evaporation or sublimation. In an optical recording medium for reproducing and erasing, the organic dye-based recording film is a mixed film or a laminated film of a phthalocyanine compound represented by the following general formula [1] and an organic compound having a melting point of 140 ° C. to 250 ° C. It is an optical recording medium characterized by the following. General formula [1]

[Chemical 2]

[In the formula, X _{1 to} X ₄ each independently represent a halogen atom, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or a substituent. Good aryl group Acyl group optionally having a substituent, heterocyclic residue optionally having a substituent, nitro group, cyano group, sulfonic acid group, carboxylic acid group, -OR ₁ , -SR ₂ , _{-NHCOR 1, -N = N-R} 1, represents a -N = CHR _1. Here, R ₁ and R ₂ may be the same or different from each other, and are a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, a substituent Represents a cycloalkyl group which may have a group, an acyl group which may have a substituent, or a polyether group, and which may form a 4- to 7-membered ring with R ₁ and R _2. In that case, it may be a heterocycle further containing a hetero atom such as a nitrogen atom, an oxygen atom and a sulfur atom. M is
H _2, a divalent metal or a hydrogen atom, a halogen atom, an oxygen atom, there hydroxyl group Represents a valent metal. Here, R ₃ represents an alkyl group which may have a substituent or an aryl group which may have a substituent.
R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are each an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxy group which may have a substituent, or It represents an aryloxy group which may have a substituent. l _{1 to} l ₄
Are each the number of substituents of X _{1 to} X ₄ , and each independently represent an integer of 0 to 2. ]

An example of the optical recording medium of the present invention has a structure of transparent substrate / recording film / reflection layer / protective layer and can be applied to an erasable optical disk or optical card.

In the optical recording medium of the present invention, the phthalocyanine compound is most effective as the organic dye used in the recording film. Further, as the phthalocyanine compound applicable to the present invention, a phthalocyanine compound molecularly modified with a specific organic substituent is particularly preferable for the reasons described below. By introducing an organic substituent to the phthalocyanine ring, the strong stacking property peculiar to the phthalocyanine molecule, which is a planar molecule, is hindered, and as a result, crystallization is less likely to occur and the intended amorphous recording film can be easily formed. There is an advantage that it is easy to form. However, as the number of introduced substituents increases, the distance between the phthalocyanine molecules increases, and the free volume for thermal motion increases accordingly, so that the stacking property peculiar to the phthalocyanine molecules deteriorates too much. Therefore, even a small amount of intermolecular interaction that occurs even in the amorphous state disappears, and it approaches an amorphous state similar to a solution state, and even when irradiated with a recording laser beam, the phthalocyanine molecule aggregates in the amorphous state. I couldn't get a clear change of state,
In some cases, sufficient recording characteristics cannot be realized.

Therefore, in order to form a recording film in an amorphous state while appropriately reducing the stacking property between the phthalocyanine molecules and slightly maintaining the intermolecular interaction,
It is necessary to control the type of substituent and the number of substituents introduced into the phthalocyanine ring. That is, the phthalocyanine-based compound to be the recording film of the present invention has the substituents represented by the general formula (1), and the total number of the introduced substituents is most preferably 1 or 2. By using such a phthalocyanine-based compound, the desired amorphous recording film is formed without causing the above-mentioned inconvenience, and further, the recording laser light causes a change in the optical characteristics depending on the molecular aggregation state, Sufficient recording characteristics are realized.

The optical recording medium of the present invention is recorded by mixing or laminating an organic compound having a melting point of 140 to 250 ° C. with a phthalocyanine compound whose transmittance changes by laser irradiation in the constitution of the recording film. Information can be erased. That is, as in the mechanism described above, the recording state in which the transmittance increases with the change in the molecular aggregation state of the phthalocyanine-based compound is irradiated with a laser of higher output, so that the melting point of the mixed or laminated layer is within a specific range. The organic compound melts, and the effect as a solvent is exhibited with the melting, and the molecular aggregation state of the phthalocyanine-based compound returns to the unrecorded state and the erasing is performed.

The organic compound having a melting point in the range of 140 to 250 ° C. is not particularly limited, but typical compounds include the following compounds. Abietic acid, aminobenzoic acid, 5-amino-2-naphthol, o-amino-
Phenol, anthrone, methyl isocyanurate, isophthalonitrile, 3-indolylacetic acid, estradiol, ethylenediphenyldisulfone, epicolecitanol, 1-oxyanthraquinone, 2-oxy-m-toluic acid, auxin, α-carotene, β- Examples include carotene, copper (II) citrate, chlorsalicylic acid, and o-chlorobenzenesulfonamide.

In the optical recording medium of the present invention, a phthalocyanine compound single film, a mixture of a phthalocyanine compound and an organic compound having a specific melting point, or an organic compound single film having a specific melting point is formed by a dry process such as vacuum deposition. It is also possible to use a wet process, for example, a spin coat method, a dip method, a spray method, a roll coat method or an LB (Langmuir-Blodgett) method. The material contained in the recording layer of the optical recording medium of the present invention is a general-purpose organic solvent, for example, alcohol-based, ketone-based, cellosolve-based,
When it is dissolved in a halogenated hydrocarbon-based or fluorocarbon-based solvent, a method of forming a film by a spin coat method is preferable from the viewpoint of productivity and uniformity of a recording film.

As described above, when the film is formed by the so-called coating method, a polymer binder may be added if necessary. Acrylic resin and polycarbonate as the polymer binder
Bone resin, polyester resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, nitrocellulose
However, the present invention is not limited to these. The mixing ratio of the polymer binder is not particularly limited, but it is necessary to add it in such an amount that the change in the aggregated state of the organic dye is not hindered, and 10% by weight or less based on the organic dye is preferable.

The recording film of the present invention has a light stability of the recording film,
UV absorbers, UV stabilizers, oxygen quenchers for the purpose of further improving environmental resistance and stability of repeated regeneration.
You may add additives, such as.

The optimum film thickness of the recording film is not particularly limited because it varies depending on the type and combination of recording materials, and is in the range of 500 to 3
000 angstrom is preferable, and 1000 to
2500 angstrom is the optimum film thickness range.

The transparent substrate used in the present invention preferably has a light transmittance of 85% or more for writing and reading signals and has a small optical anisotropy. For example, glass or acrylic resin, polycarbonate resin, polyester resin, polyamide resin, vinyl chloride resin, polyvinyl ester resin, polystyrene resin, polyolefin resin (for example, poly-4-methylpentene, etc.), polyester Substrates using a thermoplastic resin such as tersulphone resin or a thermosetting resin such as an epoxy resin or an allyl resin may be mentioned. Among these, the above-mentioned thermoplastic resins are preferable because of their ease of molding and the ease of providing guide grooves and address signals.

In the present invention, the thickness of these transparent substrates is not particularly limited and may be plate-like or film-like. The shape may be circular or card-like, and the size is not particularly limited. In other words, it is not limited to a disc-shaped recording medium such as a general optical disc, and may be an optical card, a tape-shaped recording medium, or a sheet-shaped recording medium. The transparent substrate of the present invention usually has guide grooves for position control at the time of recording and reading and unevenness for pre-formatting such as address signals and various marks. Molding thermoplastic resin as described above (injection molding, compression molding)
It is preferable to use a stamper or the like for the application, but a so-called 2P method using a photopolymer resin can also be used.

The shape of the guide groove of the present invention is not particularly limited, and may be a short shape, a trapezoidal shape, or a U-shape. Regarding the dimensions of the guide groove, the optimum values differ depending on the type and combination of the materials used for the recording layer, but the average groove width (width at half the groove depth) is 0.3 to 0. It is preferably 6 microns and the groove depth is in the range of 500 to 2000 angstroms.

When the optical recording medium of the present invention has a reflective layer, the material for the reflective layer is a metal such as gold, silver, copper, platinum, aluminum, cobalt or tin, and an alloy containing these as the main components. Examples thereof include metal oxides such as MgO, ZnO, and SnO, and nitrides such as SiN ₄ , AlN, and TiN. Gold is most preferable because it has a high absolute reflectance and excellent stability. The optimum film thickness of the reflective layer is not particularly limited, but is preferably in the range of 400 to 1300 angstrom.

In the optical recording medium of the present invention, a protective layer for protecting the medium is formed of a transparent substrate for the purpose of preventing chemical deterioration (eg, oxidation, water absorption, etc.) and physical deterioration (scratches, scratches, etc.) of the medium. When a reflection film is laminated on the laser incident surface side and on the recording film or on the recording film, it may be provided on the reflection film. As a material for the protective layer, a method in which an ultraviolet curable resin is used and applied by spin coating and cured by ultraviolet irradiation is preferable, but the material is not limited thereto. Regarding the optimum thickness of the protective layer, if it is thin,
Since the effect of protection is lowered and when the resin is thick, shrinkage during curing of the resin causes deterioration of mechanical properties such as warpage of the medium, it is preferable to form a film within a range of 2 to 20 μm. Further, for the purpose of functions other than the protective film, for example, antireflection, antistatic, moistureproof, etc., a low-refractive index material, a fluororesin or a conductive resin, etc. are formed on the transparent substrate at the laser incident surface side and recording like the protective film. When a reflective film is laminated on the film or the recording film, it may be provided on the reflective film.

[0021]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples. In the examples, “part” means “part by weight”.

Example 1 A transparent substrate having a thickness of 1.2 mm was dissolved in a mixture of 58 mg of phthalocyanine compound (a) and 2 mg of 1-oxyanthraquinone on a transparent layer of a polycarbonate substrate having a thickness of 1 ml of diacetone alcohol. A coating layer prepared through a micron filter was used to form a recording layer with a film thickness of 1200 Å by a spin coater. Further, a gold film having a thickness of 1000 angstrom was formed on the recording layer thus obtained by sputtering. Further, a protective layer having a film thickness of 5 μm was formed thereon by using an ultraviolet curable resin to prepare an optical disc.
With respect to the optical disc thus created, a wavelength of 78 is obtained by using an optical disc evaluator manufactured by Pulstec and a function generator manufactured by Hewlett-Packard.
5 nm, N.W. A. The recording and reproducing characteristics were evaluated with a semiconductor laser of = 0.5. As a result, by irradiating a laser with an output of 10 mW, the reflection level increased to 56% from 42% in the unrecorded state, and recording with a C / N ratio of 48 dB was possible. Further, by irradiating the recording portion with a laser having an output of 15 mW, the reflection level of the recording portion was reduced to 43%, and the state was returned to the unrecorded state. In addition, when recording was performed again on the erased part, the reflection level was 5
It was increased to 4% and a record with a C / N ratio of 47% could be reproduced.
Further, as a result of removing the protective film and the reflective film of the optical disc recorded in this way and observing the recording film with a microscope,
No pit formation due to the shape change was observed in the recording portion irradiated with the laser.

Phthalocyanine compound (a)

[Chemical 3]

[0024]

In the optical recording medium having the constitution of the present invention, the recording film is composed of a mixed film or a laminated film of a phthalocyanine compound having a specific substituent and an organic compound having a specific melting point. Since the phthalocyanine molecules in the film are in an amorphous state while slightly interacting with each other, recording in which only the light transmittance in the reproduction laser wavelength range is changed without the formation of pits by the laser beam is effective. It is also possible to erase recorded information by irradiating with a high-power laser beam that can reach the melting region due to the presence of an organic compound having a specific melting point.

Claims (1)

[Claims] 1. A layered product of a transparent substrate / organic dye-based recording film / reflective film, which decomposes and melts due to the thermal energy generated when the optical energy of the recording laser light incident from the transparent substrate is absorbed by the recording film. In an optical recording medium for recording, reproducing, and erasing by utilizing the phenomenon that the light transmittance in the reproduction laser light wavelength range changes without the formation of pits due to a change in the state of evaporation or sublimation, an organic dye-based recording film is used. ,
An optical recording medium, which is a mixed film or a laminated film of a phthalocyanine compound represented by the following general formula [1] and an organic compound having a melting point in the range of 140 ° C to 250 ° C. General formula [1] [Wherein, X _{1 to} X ₄ are each independently a halogen atom,
An alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, an acyl group which may have a substituent, and a substituent which has a substituent Good heterocyclic residue, nitro group, cyano group, sulfonic acid group, carboxylic acid group, -OR ₁ , -SR ₂ , _{-NHCOR 1, -N = N-R} 1, represents a -N = CHR _1. Here, R ₁ and R ₂ may be the same or different from each other, and are a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, a substituent Represents a cycloalkyl group which may have a group, an acyl group which may have a substituent, or a polyether group, and which may form a 4- to 7-membered ring with R ₁ and R _2. In that case, it may be a heterocycle further containing a hetero atom such as a nitrogen atom, an oxygen atom and a sulfur atom. M is
H _2, a divalent metal or a hydrogen atom, a halogen atom, an oxygen atom, there hydroxyl group Represents the metal. Here, R ₃ represents an alkyl group which may have a substituent or an aryl group which may have a substituent. R
₄ , R ₅ , R ₆ , R ₇ and R ₈ are each an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxy group which may have a substituent or a substituent. Represents an aryloxy group which may have a group. l _{1 to} l
₄ is the number of substituents of X _{1 to} X ₄ , and each independently represents an integer of 0 to 2. ]