JPH0648046A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide a recording medium which has a clear time resolution and is capable of high sensitivity and density recording by laminating a recording film of an amorphous organic coloring matter comprising a specified phthalocyanine compound and a reflection film in sequence on a transparent substrate. CONSTITUTION:A phthalocyanine compound expressed by the structural formula (X1-X4: halogen atom, alkyl group, aryl group, etc.; M: divalent, trivalent, or tertavalent metal; l1-l4: substituents of X1-X4, 0-2 integers, but the total is not 0) is dissolved in an alcohol solvent to prepare a coating liquid for a recording film. The coating liquid is applied on a transparent substrate including glass and a thermoplastic resin, and the coated layer is dried to form a recording film of an amorphous organic coloring matter. A reflection film comprising a metal vapor deposition film of gold, silver, copper, aluminum, etc., is laminated on the recording film by means such as sputtering to obtain an optical recording medium. The optical recording medium effectively produces recording with only the light transmittance in the wave length range of a regenerated laser beam changed, enabling microfine recording and high speed recording.

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 / from which information can be written / read by a laser beam.

[0002]

2. Description of the Related Art Conventionally, there are various media for recording information using a laser beam. One of them is an organic dye such as a cyanine dye or a phthalocyanine dye, which is used as a recording film. By irradiating a recording layer on a substrate, the irradiated part is locally heated to cause physical or chemical changes such as melting, evaporation, sublimation or decomposition, that is, pits are formed to record information. There is.

[0003]

However, as described above, by irradiating the recording layer on the substrate with the laser beam, the irradiated portion is locally heated and the physical or physical properties such as melting, evaporation, sublimation or decomposition are generated. A large amount of light energy, that is, high-power laser irradiation is required to cause the chemical change, and therefore high-speed recording, for example, linear velocity of 10 is required.
When recording at m / sec or more, the sensitivity remarkably decreases. In addition, since the recording pits are formed due to the change in shape due to physical or chemical changes, non-uniformity of the shape of the pits is unavoidable, and therefore the time resolution due to the asymmetry of the pits is not sufficient. The formation of minute pits is not satisfactory, and it cannot be said that it can sufficiently cope with high density recording. In addition, a crystalline material with no pit formation
In the case of an optical recording medium that utilizes an amorphous phase change, the recording film needs to be crystalline, so that crystal grain boundaries and the like are likely to occur, which causes problems such as noise and errors. is there.

[0004]

As a result of intensive studies, the present inventors have developed an optical recording medium capable of achieving high-speed recording and high-density recording corresponding to the formation of minute pits, and also having sufficient time resolution. The invention was completed. That is,
The present invention comprises a laminated body of a transparent substrate / amorphous organic dye recording film / reflection film, and heat energy generated when the amorphous organic dye recording film absorbs recording laser light incident from the transparent substrate. Amorphous organic dye recording in an optical recording medium utilizing the fact that pit formation due to change in state of decomposition, melting, evaporation or sublimation due to The optical recording medium is characterized in that the film is a compound represented by the following general formula [1]. General formula [1]

[0005]

[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 , ^{-N = N-R 1, -N} = CHR 1 wherein, R ¹ and R ² may be the being the same or different, a hydrogen atom, an alkyl group which may have a substituent, It represents an aryl group which may have a substituent, a cycloalkyl group which may have a substituent, an acyl group which may have a substituent, or a polyether group, and R ¹ and R ² may form a 4- to 7-membered ring, in which case it may be a heterocycle further containing a hetero atom such as a nitrogen atom, an oxygen atom, or a sulfur atom. M is
H _{2 represents} a divalent metal or a trivalent or tetravalent metal which may have a hydrogen atom, a halogen atom, an oxygen atom or a hydroxyl group. l _{1 to} l ₄ represent the number of substituents of X _{1 to} X ₄ , respectively. l _{1 to} l ₄ each independently represent an integer of 0 to 2, but are not all 0 at the same time, and further l ₁ + l
_The total of ₂ + l ₃ + l ₄ is 1 or 2. ]

The phase transition in the present invention means that the compound changes from a crystalline state to an amorphous state, or that the compound changes from an amorphous state to a crystalline state.

An example of the optical recording medium of the present invention is a write-once type corresponding to an LD having a structure of transparent substrate / recording film / reflection layer / protective layer, which rotates at high speed and requires very small minute recording. The optical disc is the most typical one, but the present invention is not limited to this, and is generally applicable to all optical recording media in which recording and reproduction are performed by laser light.

In the optical recording medium of the present invention, a phthalocyanine compound is used as the amorphous organic dye used in the recording film, and in particular, the number of substituents introduced into the phthalocyanine ring is 2.
It is characterized by the following.

The reason for this will be described below. By introducing an organic substituent into 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. In some cases, a clear change in state cannot be obtained and 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 number of substituents introduced into the phthalocyanine ring. That is, the total number of the substituents introduced into the phthalocyanine ring of the phthalocyanine-based compound which is the recording film of the present invention is 1 or 2. By using such a phthalocyanine-based compound, the target amorphous recording film is formed without causing the above-mentioned disadvantages, and further, the recording laser light causes a change in the optical characteristics associated with the molecular aggregation state, Sufficient recording characteristics are realized.

In the optical recording medium of the present invention, a recording layer is formed by a dry process, for example, a vacuum evaporation method,
Although it is possible to use the sputtering method, it is also possible to use a wet process such as a spin coat method, a dip method, a spray method, a roll coat method or an LB (Langmuir-Blodgett) method. The recording 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 it is preferably 10% by weight or less with respect to the amorphous organic dye.

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 polycarbonate substrate having a thickness of 1.2 mm was dissolved on a transparent layer in a concentration of 1 ml of diacetone alcohol with respect to 60 mg of the phthalocyanine compound (a), and the coating was adjusted through a 0.2 micron filter. Using a liquid, spin
The recording layer was formed into a film having a thickness of 1200 angstroms using a magnetic tape. 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. The optical disc prepared in this manner was measured by using an optical disc evaluator manufactured by Pulstec and a function generator manufactured by Hewlett-Packard Co., and a wavelength of 785 nm, N. A. The recording / reproducing characteristics of a single signal with a frequency of 8.5 MHz were evaluated with a semiconductor laser of = 0.5 and a linear velocity of 11 m / sec and 18 m / sec. As a result, the reflection level of the laser-irradiated recording portion becomes higher than that of the non-irradiated portion, and the recording is reversed from the polarity of the case of a normal optical disc, but even at 18 m / sec, the recording power is 10 mW and the C / N ratio is 48 dB or more. Further, the jitter was 5 nsec or less. This recording / reproducing characteristic is a characteristic that can sufficiently cope with high-speed and high-density recording, and is a level that can sufficiently cope with a normal LD recording signal that FM-modulates each signal of video, analog audio, and digital audio in the LD format. . The protective film and the reflective film of the optical disc recorded in this way were removed, and the recording film was observed under a microscope. As a result, no pit formation due to the shape change was observed in the recording portion irradiated with the laser. It was Further, when the X-ray analysis pattern of the transparent substrate / phthalocyanine compound (a) single film before and after recording was measured, no clear peak was observed for both, and before recording (FIG. 1) and after recording ( 2), the state of the recording film was amorphous.

[0023]

[Chemical 3] Phthalocyanine compound (a)

[0024]

[Figure 1]

[0025]

[Fig. 2]

Example 2 A coating solution prepared by dissolving 40 mg of the phthalocyanine compound (b) in a concentration of 1 ml of ethoxyethanol on a transparent substrate on a polycarbonate substrate having a thickness of 1.2 mm and passing through a 0.2-micron filter. Was used to form a recording layer having a film thickness of 1500 angstrom 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. The optical disc prepared in this manner was measured by an optical disc evaluator manufactured by Pulstec and a function generator manufactured by Hewlett-Packard, at a wavelength of 785 nm, and an N.M. A. The recording / reproducing characteristics of a single signal with a frequency of 8.5 MHz were evaluated with a semiconductor laser of = 0.5 and a linear velocity of 11 m / sec and 18 m / sec. As a result, the reflection level of the laser-irradiated recording portion becomes higher than that of the non-irradiated portion, and the recording is reversed from the polarity of the case of an ordinary optical disk, but even at 18 m / sec, the recording power is 10 mW and the C / N ratio is 45 dB or more. Further, the jitter was 5 nsec or less. This recording / reproducing characteristic is a characteristic that can sufficiently cope with high-speed and high-density recording, and is a level that can sufficiently cope with a normal LD recording signal that FM-modulates each signal of video, analog audio, and digital audio in the LD format. . The protective film and the reflective film of the optical disc recorded in this way were removed, and the recording film was observed under a microscope. As a result, no pit formation due to the shape change was observed in the recording portion irradiated with the laser. It was

Phthalocyanine compound (b)

[Chemical 4]

Example 3 A polycarbonate substrate having a thickness of 1.2 mm was coated on a transparent layer by dissolving 50 mg of the phthalocyanine compound (c) in a concentration of 1 ml of diacetone alcohol, and adjusting the concentration through a 0.2-micron filter. Using a liquid, spin
The recording layer was formed into a film having a thickness of 1500 angstroms. 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. The optical disc prepared in this manner was measured by an optical disc evaluator manufactured by Pulstec and a function generator manufactured by Hewlett-Packard, at a wavelength of 785 nm, and an N.M. A. The recording / reproducing characteristics of a single signal with a frequency of 8.5 MHz were evaluated with a semiconductor laser of 0.5 for linear velocities of 11 m / sec and 18 m / sec. As a result, the reflection level of the laser-irradiated recording portion is higher than that of the non-irradiated portion, and the recording is reversed from the polarity of the case of a normal optical disc, but even at 18 m / sec, the recording power is 10 mW and the C / N ratio is 40 dB or more. Further, the jitter was 5 nsec or less. This recording / reproducing characteristic is a characteristic that can sufficiently cope with high-speed and high-density recording, and is a level that can sufficiently cope with a normal LD recording signal that FM-modulates each signal of video, analog audio, and digital audio in the LD format. . The protective film and the reflective film of the optical disc recorded in this way were removed, and the recording film was observed under a microscope. As a result, no pit formation due to the shape change was observed in the recording portion irradiated with the laser. It was

Phthalocyanine compound (c)

[Chemical 5]

Comparative Example 1 An optical disc prepared by using the phthalocyanine compound (d) in the same manner as in Example 1 was recorded in the same manner as in Example 1, but no recording was possible at a linear velocity of 18 m / sec. .

Phthalocyanine compound (d)

[Chemical 6]

Comparative Example 2 An optical disc prepared by using the phthalocyanine compound (e) in the same manner as in Example 2 was recorded in the same manner as in Example 1, but no recording was possible at a linear velocity of 18 m / sec. .

Phthalocyanine compound (e)

[Chemical 7]

Comparative Example 3 An optical disc prepared by using the phthalocyanine compound (f) in the same manner as in Example 3 was recorded in the same manner as in Example 1, but no recording was possible at a linear velocity of 18 m / sec. .

Phthalocyanine compound (F)

[Chemical 8]

[0036]

In the optical recording medium having the constitution of the present invention, the total number of the substituents introduced into the ring of the phthalocyanine compound used in the recording film is set to 1 or 2, whereby the phthalocyanine molecules in the recording film are slightly separated from each other. Since it becomes an amorphous state while maintaining the interaction, recording that effectively changes only the light transmittance in the reproduction laser wavelength range without the formation of pits by the laser beam, resulting in a very clear time resolution. It is possible to realize excellent recording with high sensitivity and high density recording and reproduction, and it can be an optical recording medium compatible with minute recording and high-speed recording.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of the phthalocyanine compound (a) before irradiation with laser light of 780 nm. FIG. 2 is an X-ray diffraction diagram of the phthalocyanine compound (a) before irradiation with laser light of 780 nm.

Claims (1)

[Claims] 1. Heat generated when a recording laser beam incident from a transparent substrate is absorbed by the amorphous organic dye recording film, which is composed of a laminated body of a transparent substrate / amorphous organic dye recording film / reflection film. An amorphous organic dye is used in an optical recording medium utilizing the fact that pits are formed due to a change in the state of decomposition, melting, evaporation or sublimation due to energy, or the light transmittance in the reproduction laser light wavelength region is not accompanied by a phase transition. An optical recording medium, wherein the recording film is a compound represented by the following general formula [1]. 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 , ^{-N = N-R 1, -N} = CHR 1 wherein, R ¹ and R ² may be the being the same or different, a hydrogen atom, an alkyl group which may have a substituent, It represents an aryl group which may have a substituent, a cycloalkyl group which may have a substituent, an acyl group which may have a substituent, or a polyether group, and R ¹ and R ² may form a 4- to 7-membered ring, in which case it may be a heterocycle further containing a hetero atom such as a nitrogen atom, an oxygen atom, or a sulfur atom. M is
H _{2 represents} a divalent metal or a trivalent or tetravalent metal which may have a hydrogen atom, a halogen atom, an oxygen atom or a hydroxyl group. l _{1 to} l ₄ represent the number of substituents of X _{1 to} X ₄ , respectively. l _{1 to} l ₄ each independently represent an integer of 0 to 2, but are not all 0 at the same time, and further l ₁ + l
_The total of ₂ + l ₃ + l ₄ is 1 or 2. ]