JPH06320868A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium enabling high speed recording and the high density recording corresponding to the formation of a fine pit by successively laminating a recording film composed of a mixture of a phthalocyanine dye and a polymer, a reflecting film and a protective film on a transparent substrate. CONSTITUTION:A phthalocyanine dye represented by formula (wherein Pc is a phthalocyanine residue, M is a metal atom, A is -COO-, m and n are an integer of 1-4 and R1 and R2 are a hydrogen atom and an alkyl group) and a polymer are dissolved in a general-purpose org. solvent to prepare a coating soln. which is, in turn, applied to a transparent substrate composed of glass or an acrylic resin and dried to form a recording film. A metal such as gold, silver or copper or an alloy thereof is applied to the recording film by vacuum vapor deposition or sputtering to laminate a reflecting film on the recording film. Further, a coating soln. prepared by dissolving an ultraviolet curable resin in an org. solvent is applied to the reflecting film and dried to laminate a protective film on the reflecting film to obtain an optical recording medium.

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 capable of recording and reproducing information by laser light.

[0002]

2. Description of the Related Art Conventionally, there are various media for recording information using a laser beam, one of which is a recording film made of an organic dye such as a cyanine dye and a phthalocyanine dye.
By irradiating the recording film layer on the substrate with laser light, 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 form information. There is something to record. However, by irradiating the recording film layer on the substrate with laser light, the irradiated portion is locally heated to cause a physical or chemical change such as melting, evaporation, sublimation, or decomposition. That is, high-power laser irradiation is required, and therefore high-speed recording, for example, linear velocity 1
When recording at 0 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 was not satisfactory, and it was hard to say that it could sufficiently cope with high-density recording. Further, in the case of an optical recording medium utilizing a crystalline-amorphous phase change without formation of pits, the recording film needs to be crystalline, so that crystal grain boundaries easily occur and noise, There is a problem that it is likely to cause an error. This problem is caused by using the phthalocyanine-based dye represented by the above general formula [1] as a recording film, so that thermal energy generated by absorbing recording laser light causes melting, evaporation, sublimation or decomposition of the irradiated portion. The problem is solved by an optical recording medium that utilizes the change in the light transmittance in the reproduction laser light wavelength range without the formation of pits or the phase transition due to the change in the state.

[0003]

However, when the phthalocyanine dye represented by the above general formula [1] is used as the recording film, the irradiated portion is melted and evaporated by the thermal energy generated by absorbing the recording laser light. In the case of an optical recording medium that utilizes changes in light transmittance in the reproduction laser light wavelength range without pit formation or phase transition due to state changes due to sublimation or decomposition, this recording state is
Under normal operating conditions, the change in light transmittance gradually decreases over time, approaching the light transmittance before recording by laser light, and as a result, the modulation of the recording signal significantly deteriorates, causing noise, errors, etc. The frequency of occurrence tends to be extremely high, and there are problems in terms of storage stability of recorded signals and long-term reliability. Moreover, this phenomenon is further accelerated under high temperature and high humidity conditions.

[0004]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention obtained high-density recording corresponding to high-speed recording and formation of minute pits, and sufficient time resolution.
Moreover, the present invention has been completed by developing an optical recording medium excellent in storage stability and reliability of recording signals.

That is, the present invention is a transparent substrate / dye recording film /
It is composed of a laminated body of a reflective film / protective film, and the recording film absorbs a recording laser beam incident from a transparent substrate to generate thermal energy, thereby forming pits due to a change in state of decomposition, melting, evaporation or sublimation, or An optical recording medium utilizing the fact that the light transmittance in the wavelength region of a reproducing laser light without a phase transition is changed is characterized in that the recording film is composed of a mixed film of an amorphous phthalocyanine dye and a polymer. It is an optical recording medium.

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.

The phthalocyanine dye used in the recording film of the present invention is represented by the following general formula [1]. General formula [1]

[Chemical 2] In the formula, Pc: Phthalocyanine residue M: Central atom of metal atom or metal oxide or metal hydroxide or halide A: divalent bonding group or direct bond shown below —COO—, —CH _{2 NR '-, - CH 2 NHCOCH} 2
_{NH -, - SO 2 NR '} -, - CONR' - (R ' represents a saturated or unsaturated alkyl group of hydrogen atoms or carbon atoms 1~20) m, n: each independently 1-4
R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a heterocycle containing at least a nitrogen atom for R ₁ and R ₂ .

The polymer used in the recording film of the present invention has a glass transition temperature of -50 ° C or higher and 200 ° C or lower.

The reason for this will be described below. By introducing an organic substituent into the phthalocyanine ring as shown in the above general formula [1], 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 An amorphous recording film is formed. When this recording film is irradiated with a recording laser beam, the light transmittance is changed due to a change in the aggregated state of phthalocyanine molecules, a three-dimensional structural change in the molecule, or a synergistic effect thereof, and recording is performed. However, this recording state gradually returns to the original pre-recording state over time under normal use environment, so the change in light transmittance gradually decreases, and approaches the light transmittance before recording by laser light. As a result, the degree of modulation of the recording signal is significantly deteriorated and the occurrence of noise, errors, etc. is extremely increased, which causes problems in storage stability and long-term reliability of the recording signal. Further, this phenomenon tends to be further accelerated under high temperature and high humidity conditions. On the other hand, -50 ° C
When a recording laser light is irradiated to a recording film in which a polymer having the above glass transition temperature and the phthalocyanine-based dye represented by the above general formula [1] are mixed, the aggregated state of phthalocyanine molecules is changed, and the three-dimensional intramolecular Due to the structural change or their synergistic effect, a change in the light transmittance occurs and the recording state in which recording is performed can be fixed. Therefore, it is possible to greatly improve the storage stability and long-term reliability of recorded signals under the conditions of time and high temperature and high humidity. However, when the glass transition temperature of the polymer is 200 ° C. or higher, the power of the recording laser beam required at the time of recording remarkably increases, so a polymer having a glass transition temperature of 200 ° C. or lower is desirable.

The type of polymer used in the recording film of the present invention is not particularly limited, and specifically, acrylic resin, polycarbonate resin, polyester resin, polyether resin, polyamide resin, polyimide resin, vinyl chloride resin, acetic acid. Examples thereof include vinyl resin, nitrocellulose resin and the like, or a mixture thereof. In addition, even if a thermosetting type compound containing a curing agent such as a phenol resin, an amino resin or an isocyanate resin is added as necessary, U
Even by utilizing V-curing, EB-curing or the like, if the glass transition temperature of the final polymer is −50 ° C. or higher and 200 ° C. or lower, the present invention is not impaired. The mixing ratio of the phthalocyanine dye and the polymer used in the recording film of the present invention is not particularly limited.

In the optical recording medium of the present invention, the recording film is a phthalocyanine-based dye and polymer, and a general-purpose organic solvent such as alcohol-based, halogenated alcohol-based, ketone-based, cellosolve-based, hydrocarbon-based, halogenated hydrocarbon-based solvents. A chlorofluorocarbon-based solvent or the like, or a mixed solvent thereof is used to dissolve, and a film is formed by a wet process such as a spin coating method, a dipping method, a spraying method, or a roll coating method. Particularly in the case of an optical recording medium, a method of forming a film by a spin coating method is preferable from the viewpoint of productivity and uniformity of a recording film.

The recording film of the present invention has a light stability of the recording film,
For the purpose of improving environmental resistance and stability of repeated reproduction,
You may add additives, such as a ultraviolet absorber, a ultraviolet stabilizer, and an oxygen quencher.

The optimum film thickness of the recording film is not particularly limited because it depends on the type and combination of phthalocyanine dye and polymer and the compounding ratio, but is preferably 300 to 3000 angstroms, more preferably 500 to 2000 angstroms. Is.

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.), polyether sulfone resin, etc. Examples of the substrate include a thermosetting resin such as a thermoplastic resin, an epoxy resin, or an allyl resin. 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. That is, the optical disk is not limited to a disk-shaped recording medium, 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 preformatting such as address signals and various marks. These unevennesses are as described above. It is preferable to use a stamper or the like when molding (injection molding, compression molding) such a thermoplastic resin, but it is also possible to use a so-called 2P method using a photopolymer resin.

The shape of the guide groove of the present invention is not particularly limited and may be rectangular, trapezoidal or U-shaped. The size of the guide groove is not particularly limited because its optimum value varies depending on the type and combination of phthalocyanine dye and polymer used in the recording film and the compounding ratio, but the average groove width (1/2 of the groove depth). It is preferable that the width) is 0.2 to 0.7 μm and the groove depth is 500 to 3000 angstrom.

As the material of the reflective film of the optical recording medium of the present invention, metals such as gold, silver, copper, platinum, aluminum, cobalt and tin and alloys containing these as a main component, for example Mg.
O, ZnO, SnO and other metal oxides, SiN ₄ , Al
Examples thereof include nitrides such as N and TiN, and gold is most preferable because of its high absolute reflectance and excellent stability. In order to form a reflective film in the optical recording medium of the present invention, a dry process, such as a vacuum vapor deposition method or sputtering, can be used. The optimum film thickness of the reflective layer is not particularly limited, but is preferably in the range of 400 to 2000 angstrom.

As a material for the protective film of the optical recording medium of the present invention, a method of applying an ultraviolet curable resin by spin coating and curing by ultraviolet irradiation suppresses thermal damage to the optical recording medium. It is preferable in that a coating film having excellent performance as a protective film can be obtained, but the invention is not limited thereto. Further, for the purpose of functions other than the protective film, for example, antireflection, antistatic, moistureproof, etc., a low refraction material, a fluororesin, a conductive resin, or the like is formed on the transparent substrate on the laser incident surface side and the protective film as well as the protective layer. It may be provided on.

[0019]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 A depth of 1000 angstroms, a spiral guide groove having a pitch of 1.6 μm, a thickness of 1.2 mm, and an outer diameter of 120 m.
m, an inner diameter of 15 mm, on a polycarbonate resin substrate, phthalocyanine compound (a) 30 mg, epoxy resin (Yukaka Shell Epoxy Co., trade name Epicoat 1004) 1
A recording film was formed in a thickness of 1000 angstrom by a spin coater using a solution prepared by dissolving 5 mg of ethyl cellosolve in a concentration of 1 ml and passing through a 0.2 micron filter. Further, a gold reflection film was formed on the recording film thus obtained by a sputtering method so as to have a thickness of 1200 angstrom. 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. Using the optical disc manufactured in this way, an optical disc evaluation device made by Pulstec, a function generator made by Hewlett-Packard, and a modulation domain
Using an analyzer, 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 at linear velocities of 11 m / sec and 18 m / sec. As a result, the reflection level of the laser irradiation part becomes higher than that of the non-irradiation part, and
The change in the light transmittance at 5 nm is 14%, and the recording is the reverse of the polarity of a normal optical disc.
C / N ratio of 45d at recording power of 10mW even at m / sec
B or more, and the jitter was 5 nsec. 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 In addition, in order to examine the storage stability and long-term reliability of the recorded state, after a lapse of 100 hours at a temperature of 60 ° C. and a relative humidity of 90%, the change in light transmittance was measured and found to be 14%. No change, C / N
The ratio was 45 dB, which was almost unchanged.

Phthalocyanine compound (a)

[Chemical 3]

Example 2 Depth 1000 angstrom, thickness 1.2 mm with spiral guide grooves with pitch 1.6 μm, outer diameter 120 m
30 m of the phthalocyanine compound (a) used in Example 1 on a polycarbonate resin substrate having an inner diameter of 15 mm and an inner diameter of 15 mm.
g, UV curable polymer (3Bond, trade name 3
070) Dissolved at a concentration of 1 ml of Elcellosolve in 15 mg and coated with a spin coater using a solution prepared through a 0.2 micron filter,
It was photocured by a UV exposure device to form a recording film with a film thickness of 1000 angstrom. Further, a gold reflection film was formed on the recording film thus obtained by a sputtering method so as to have a thickness of 1200 angstrom. 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. Using the optical disc manufactured in this manner, an optical disc evaluation device manufactured by Pulstec, a function generator manufactured by Hewlett-Packard, and a modulation domain analyzer were used, and the wavelength was 785 nm. A. = 0.
5 semiconductor lasers with linear velocities of 11 m / sec and 18
The recording / reproducing characteristics of a single signal having a frequency of 8.5 MHz were evaluated by m / sec. As a result, the reflection level of the laser irradiation part becomes higher than that of the non-irradiation part, and the wavelength is 785n.
The change in the light transmittance at m is 14%, and the recording is the opposite of the polarity in the case of an ordinary optical disc.
C / N ratio of 45d at recording power of 10mW even at m / sec
B or more, and the jitter was 5 nsec. 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. . Further, the protective film and the reflective film of the optical disk thus recorded 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. . Furthermore, in order to examine the storage stability and reliability of the recorded state, the temperature was changed to 14% when the change in light transmittance was measured after 100 hours at a temperature of 60 ° C. and a relative humidity of 90%. None, C / N ratio is 4
There was almost no change at 4 dB.

Comparative Example 1 Depth of 1000 angstrom, thickness of 1.2 mm with spiral guide grooves having a pitch of 1.6 μm, outer diameter of 120 m
30 mg of the phthalocyanine compound (a) used in Example 1 on a polycarbonate resin substrate having an inner diameter of 15 mm and an inner diameter of 15 mm.
, And dissolved at a concentration of 1 ml of ethyl cellosolve,
A recording film having a film thickness of 1000 angstrom was formed by a spin coater using the solution prepared through a 2 micron filter. Further, a gold reflection film having a thickness of 12 is formed on the recording film thus obtained by a sputtering method.
The film was formed to have a thickness of 00 angstrom. further,
An optical disk was prepared by providing a protective layer of 5 μm thick with an ultraviolet curable resin on this. Using the optical disk thus produced, an optical disk evaluation device manufactured by Pulstec, a function generator manufactured by Hewlett-Packard, and a modulation domain analyzer were used to measure a wavelength of 785 nm N.V. A. = 0.5 m semiconductor laser with linear velocities of 11 m / sec and 18 m / s
The recording / reproducing characteristics of a single signal with a frequency of 8.5 MHz were evaluated by ec. As a result, the reflection level of the laser-irradiated portion was higher than that of the non-irradiated portion, and the change in the light transmittance at the wavelength of 785 nm was 10%, resulting in recording that is the reverse of the polarity in the case of a normal optical disc, but 18 m / sec
However, the recording power was 10 mW, the C / N ratio was 45 dB or more, and the jitter was 5 nsec. This recording / reproducing characteristic is a characteristic that can sufficiently cope with high-speed and high-density recording, and the signals of video, analog audio, and digital audio are L
The level was sufficiently high for a normal LD recording signal FM-modulated in the D format. 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 layer with a microscope, no pit formation due to the shape change was observed in the recording portion irradiated with the laser. . In addition, in order to examine the storage stability and reliability of the recorded state, after a lapse of 100 hours in an environment of a temperature of 60 ° C. and a relative humidity of 90%, the change in light transmittance was measured to be 4%. It is decreasing and the C / N ratio is also 20d
It had dropped to B.

[0024]

EFFECTS OF THE INVENTION With the constitution of the present invention, a very sharp time resolution utilizing recording in which only the light transmittance in the reproduction laser wavelength range is changed without pit formation by the laser beam, high sensitivity and high density It is possible to improve the storage stability and long-term reliability of the optical recording medium that is compatible with the minute recording capable of recording and reproducing and the high-speed recording.

Claims (3)

[Claims] 1. A recording film comprising a laminated body of a transparent substrate / recording film / reflection film / protective film, wherein the recording laser light incident from the transparent substrate surface side is absorbed by the recording film to generate thermal energy. In the optical recording medium utilizing the phenomenon that the light transmittance in the reproduction laser light wavelength range changes without the formation of pits due to the change of state such as decomposition, melting, evaporation, or sublimation of the components constituting the An optical recording medium comprising a mixed film of a phthalocyanine dye and a polymer. 2. A recording film comprising a laminated body of a transparent substrate / recording film / reflection film / protective film, wherein thermal energy generated by absorption of light energy of recording laser light incident from the transparent substrate surface side by the recording film. In the optical recording medium utilizing the phenomenon that the light transmittance in the reproduction laser light wavelength range changes without the formation of pits due to the change of state such as decomposition, melting, evaporation, or sublimation of the components constituting the An optical recording medium comprising a mixed film of a phthalocyanine dye represented by the following general formula [1] and a polymer.
General formula [1] In the formula, Pc: Phthalocyanine residue M: Central atom of metal atom or metal oxide or metal hydroxide or halide A: divalent bonding group or direct bond shown below —COO—, —CH _{2 NR '-, - CH 2 NHCOCH} 2
_{NH -, - SO 2 NR '} -, - CONR' - (R ' represents a saturated or unsaturated alkyl group of hydrogen atoms or carbon atoms 1~20) m, n: each independently 1 to 4 integer R ₁ , R ₂ : each independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a heterocycle containing at least a nitrogen atom for R ₁ and R ₂ . 3. A recording film comprising a laminated body of a transparent substrate / recording film / reflection film / protective film, wherein the recording laser light incident from the transparent substrate surface side is absorbed by the recording film to generate thermal energy. In the optical recording medium utilizing the phenomenon that the light transmittance in the reproduction laser light wavelength range changes without the formation of pits due to the change of state such as decomposition, melting, evaporation, or sublimation of the components constituting the An optical recording medium comprising a mixed film of a phthalocyanine dye and a polymer having a glass transition temperature of -50 ° C or higher and 200 ° C or lower.