JPH0257030B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photothermal conversion recording medium that records and reproduces information at a high density by using a photothermal conversion effect using a laser or the like. The present invention relates to a photothermal conversion recording medium that effectively absorbs light with wavelengths in the visible and near infrared regions, converts it into thermal energy, and enables high-density recording and optical reproduction.

[Prior art] The photothermal conversion recording medium used in optical disk technology is
High-density information can be recorded by optically detectable small (eg, about 1 micron) pits formed in a photothermal conversion recording layer provided on a substrate in the form of spiral or circular tracks. To write information on such a disk, a focused laser is scanned over the surface of the laser sensitive layer, and only the surface irradiated with this laser beam forms pits, which are formed in the form of a spiral or circular track. do. The laser sensitive layer can absorb laser energy to form optically detectable pits. For example, in the heat mode recording method, the laser energy irradiated to the laser sensitive layer is absorbed and converted into thermal energy, and a small pit can be formed at that location by evaporation or deformation, or an optical Pits can be formed with oxidation degree differences, reflectance differences, or density differences caused by physically detectable chemical changes.

The information recorded on this optical disk is detected by scanning a laser along the track and reading the optical changes in the pitted and non-pitted areas. For example, a laser is scanned along a track and the energy reflected by the disk is monitored by a photodetector. When pits are not formed, the output of the photodetector is reduced, while when pits are formed, the laser beam is sufficiently reflected by the underlying reflective surface and the output of the photodetector is increased.

As a recording medium used for such optical discs,
So far, methods have been proposed that mainly use inorganic materials such as metal thin films such as aluminum vapor-deposited films, bismuth thin films, tellurium oxide thin films, and chalcogenite amorphous glass films.

On the other hand, a liquid crystal element that can use a photothermal conversion recording method can form an optical image corresponding to an optical signal generated from a laser or the like.

Conventionally, a liquid crystal element is prepared in which a mixed liquid crystal of a nematic liquid crystal with a negative dielectric anisotropy and a cholesteric liquid crystal or a smectic liquid crystal with a positive dielectric anisotropy is arranged between two glass substrates. When a laser beam or the like is irradiated onto the area, thermal energy is generated locally at that area, and the area is heated to the isotropic phase. Thereafter, rapid cooling forms a liquid crystal phase with a random orientation different from the initial uniform orientation. As a result, light scattering occurs at the location where the laser beam is irradiated, resulting in a difference in optical characteristics between the liquid crystal phase in the background region, which is in a uniformly aligned state.

This type of liquid crystal element can also erase an optical image formed by laser writing using the method described above. In other words, electrodes are provided on each of the two substrates that make up the liquid crystal element, and the entire liquid crystal element is heated with a laser beam and another heat source (for example, a heater), thereby heating the liquid crystal phase to the isotropic phase. For example, the optical image previously formed by writing can be erased by cooling until a homeotropic structure is formed in the case of a smectic liquid crystal, or a grunge structure in the case of a cholesteric-neomatic liquid crystal.

A liquid crystal device using such a photothermal conversion recording method does not require a matrix electrode structure to form pixels, and can form an image pattern simply by scanning optical signals converted from electrical signals. The advantage is that it can be obtained on a large screen. However, when a laser beam is used, the efficiency of absorbing the laser beam and converting it into thermal energy is not sufficient, and there is a drawback that sufficient writing cannot be performed even if an optical signal is scanned. Therefore, in the past, for example, “Society of Information Display”
International Symposium, Digest of
Technical Paper”P.P34−49, 172−187, 238−
253 (1982), a guest-host type photothermal conversion recording type liquid crystal device in which a black dye is mixed into a smectic liquid crystal has been proposed.

By the way, in recent years, semiconductor lasers have been developed that are small, low-cost, and capable of direct modulation, but the oscillation wavelength of this laser is 700 nm.
In addition, the laser beam power is generally lower than that of gas lasers such as argon lasers and helium-neon lasers.
Therefore, when performing photothermal conversion recording using such a semiconductor laser, the absorption characteristics of the laser sensitive layer have an absorption peak on the long wavelength side (generally between 700 nm and 850 nm).
It is effective to have a

However, conventional photothermal conversion recording media do not have sufficient efficiency in absorbing laser light and converting it into thermal energy. has a drawback that the laser utilization rate is low and high sensitivity characteristics cannot be obtained due to the high reflectivity of the laser beam.Moreover, setting the sensitive wavelength range to 700 nm or more requires changing the layer structure of the laser sensitive layer. It has the disadvantage of increasing complexity. For this reason, in recent years, research has been carried out on organic compounds whose substances can be changed by light energy in a relatively long wavelength range. For example, U.S. Patent No. 4,315,983, “Reseach Disclosure” 20517
(1981.5) and the pyrylium dye disclosed in J.Vac.Scl.
Technol., 18(1), Jan./Feb.1981, P105~
It is known that the organic compound containing the squarerium dye disclosed in P109 is sensitive to a laser of 700 nm or more.

However, organic compounds generally have problems such as their absorption characteristics becoming more unstable in the longer wavelength region and being more easily decomposed by a slight temperature rise.

On the other hand, when a guest-host type photothermal conversion recording type liquid crystal element uses a semiconductor laser as described above, the power is low, so the efficiency of absorbing laser light and converting it into thermal energy is not sufficient, and it is It has the disadvantage of requiring low power or low speed optical signal scanning. In addition, the liquid crystal element using the black dye described above has a drawback in that a white image pattern is formed in a black background, which does not provide good display from an ergonomic point of view.

[Problems to be Solved by the Invention] As mentioned above, it is necessary to satisfy various characteristics required of photothermal conversion recording media used as optical disks and liquid crystal elements, so it is not always possible to fully satisfy them in terms of practicality. At present, it cannot be said that a photothermal conversion recording medium that can perform this conversion has been developed.

Accordingly, a first object of the present invention is to provide a new and useful photothermal conversion recording medium.

The second object of the present invention is to provide a photothermal device that has absorption characteristics in the visible and near-infrared wavelengths, effectively absorbs light and converts it into thermal energy, and enables high-density recording and optical reproduction. The objective is to provide a conversion recording medium.

A third object of the present invention is to provide a thermally stable photothermal conversion recording medium that eliminates the above-mentioned drawbacks.

A fourth object of the present invention is to provide a novel photothermal conversion recording medium for optical discs.

A fifth object of the present invention is to provide a photothermal conversion recording medium for optical disks that is highly sensitive at wavelengths in the visible and near infrared regions and has a sufficient S/N ratio.

A sixth object of the present invention is to provide a liquid crystal element that can use a novel photothermal conversion recording method.

A fourth object of the present invention is to provide a liquid crystal element using a photothermal conversion recording method that can form an optical image pattern in response to optical signal scanning from an optical signal generator using a laser oscillator. .

[Means for Solving the Problems] and [Operations] The objects of the present invention are achieved by a photothermal conversion recording medium containing an azulenium salt compound represented by the following general formula [].

General formula [] In the general formula [], R ₁ to R ₇ are hydrogen atoms,
Halogen atoms (chlorine atoms, bromine atoms, iodine atoms)
Or represents a monovalent organic residue. Monovalent organic residues can be selected from a wide variety of groups, but in particular alkyl groups (methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl,
n-amyl, n-hexyl, n-octyl, 2-
ethylhexyl, t-octyl, etc.), alkoxy groups (methoxy, ethoxy, propoxy, butoxy, etc.), substituted or unsubstituted aryl groups (phenyl, tolyl, xylyl, ethyl phenyl, methoxyphenyl, ethoxyphenyl, chlorophenyl, nitrophenyl, dimethyl aminophenyl, α-naphthyl, β-naphthyl, etc.), substituted or unsubstituted heterocyclic groups (pyridyl, quinolyl,
carbazolyl, furyl, thienyl, pyrazolyl, etc.), substituted or unsubstituted aralkyl groups (benzyl, 2-phenylethyl, 2-phenyl-1-
Methyl ethyl, bromobenzyl, 2-bromophenylethyl. methylbenzyl, methoxybenzyl, nitrobenzyl), acyl groups (acetyl, propionyl, butyryl, valeryl, benzoyl,
trioyl, naphthoyl, phthaloyl, furoyl, etc.), substituted or unsubstituted amino groups (amino,
dimethylamino, diethylamino, dipropylamino, acetylamino, benzoylamino, etc.),
Substituted or unsubstituted styryl group (styryl, dimethylaminostyryl, diethylaminostyryl,
dipropylaminostyryl, methoxystyryl,
ethoxystyryl, methylstyryl, etc.), nitro group, hydroxy group, mercapto group, thioether group, carboxylic acid, carboxylic acid ester, carboxylic acid amide, cyano group, substituted or unsubstituted arylazo group (phenylazo, α-naphthylazo,
β-naphthylazo, dimethylaminophenylazo, chlorophenylazo, nitrophenylazo,
methoxyphenylazo, tolylazo, etc.). Also, R ₁ and R ₂ , R ₂ and R ₃ , R ₃ and
At least one of the combinations of R ₄ , R ⁴ and R ₅ , R ₅ and R ₆ , and R ₆ and R ₇ may form a substituted or unsubstituted fused ring. 5-membered, 6-membered rings as fused rings
It is a condensed ring of 7-membered or 7-membered rings, and includes aromatic rings, heterocycles, and aliphatic chains.

R ₈ and R ₉ are substituted or unsubstituted alkyl groups (methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-amyl, n
-hexyl, n-octyl, 2-ethylhexyl, t-octyl, etc.), substituted or unsubstituted aryl groups (phenyl, tolyl, xylyl, ethylphenyl, chlorophenyl, nitrophenyl,
methoxyphenyl, ethoxyphenyl, α-naphthyl, β-naphthyl, etc.) or substituted or unsubstituted aralkyl groups (benzyl, 2-phenylethyl, 2-phenyl-1-methylethyl, methylbenzyl, methoxybenzyl, nitrobenzyl, etc.) represents. Further, R ₈ and R ₉ can form a 5- to 6-membered ring (morpholino, pyrrolidino, piperidinylpiperazino, phenothiazino, phenoxazino, carbazolyl, indolyl, pyrrolyl, pyrazolyl, etc.) together with the nitrogen atom.

Ar ₁ and Ar ₂ are substituted or unsubstituted aryl groups (phenylene, 1,4-naphthylene, 1,5
-naphthylene, 9,10-antrylene, etc.). Substituents include alkyl groups (methyl, ethyl, n-propyl, isopropyl, n-butyl,
(t-butyl, n-hexyl, 2-ethylhexyl, etc.), alkoxy groups (methoxy, ethoxy, propoxy, butoxy, etc.), halogen atoms (chlorine atom, bromine atom, iodine atom), and the like.

Z represents an anion residue, and specific examples of Z include perchlorate, fluoroborate, sulfoacetate, iodide, chloride, bromide, p-toluenesulfonate, alkylsulfonate, alkyldisulfonate, benzenedisulfonate, halosulfonate, picrate. , represents an anion residue such as tetracyanoethylene anion, tetracyanodimethane anion, etc.

Specific examples of the azulenium salt compounds used in the present invention are listed below.

Compounds represented by the general formula [ ] are included in the Journal
of the chemical Society P.1110~P.1117 (1958
), Journal of the chemical Society P.494～
P.501 (1960) and Journal of the chemistry
It can be obtained by mixing an azulene compound and a corresponding aldehyde compound in a suitable solvent in the presence of a strong acid as described in Society P.3579-P.3593 (1961).

Synthesis examples of the compounds of the present invention will be shown below.

Synthesis Example 0.81 g of thionyl chloride was added to 1.89 g of 4-dimethylaminoazobenzene-4'-carboxylic acid (manufactured by Tokyo Kasei Co., Ltd.: M0423) and reacted to obtain 1.71 g of p-dimethylaminoazobenzene-4'-chloride.

Next, this compound was hydrogenated for 8 hours using palladium as a catalyst to obtain an aldehyde. 1.35g of this aldehyde and 0.68g of azulene are mixed with methanol.
After adding 80 ml and dissolving it, drop a mixed solution of 1.5 ml of 70% perchloric acid and 20 ml of methanol to this solution64
It was refluxed at ℃ for 1 hour. A precipitate formed by leaving the reaction solution to stand was filtered out, washed twice with 30 ml of cold methanol, and dried to obtain Compound No. 1.

Yield: 28% Elemental analysis: Molecular formula C ₂₅ H ₂₂ N ₃ Theoretical value (%) Analytical value (%) C 82.39 82.80 H 6.08 5.78 N 11.53 11.42 The reaction solvent used is alcohol such as ethanol, butanol, benzyl alcohol, etc. nitriles such as acetonitrile and propionitrile, organic carboxylic acids such as acetic acid, acid anhydrides such as acetic anhydride, alicyclic ethers such as dioxane and tetrahydrofuran, and the like.
Furthermore, aromatic hydrocarbons such as benzene can be mixed with butanol, benzyl alcohol, and the like. The temperature during the reaction can be selected from the range of room temperature to boiling point.

The photothermal conversion recording medium of the present invention can be used for optical disc recording. For example, a thin film 2 containing the azulenium salt compound described above may be formed on a substrate 1 as shown in FIG.
Such a thin film 2 can be formed by vacuum deposition of the azulenium salt compound represented by the above-mentioned general formula [], or by applying a coating liquid containing the above-mentioned azulenium salt compound in a suitable solvent. can be formed. When forming a film by coating, the azulenium salt compound described above may be contained in a solvent in a dispersed state or in an amorphous state. In addition, a resin can be included as a binder in the coating solution,
Suitable binders can be selected from a wide variety of resins. Specifically, cellulose esters such as nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose myristate, cellulose palmitate, cellulose acetate/propionate, cellulose acetate/butyrate, methyl cellulose, Cellulose ethers such as ethyl cellulose, propyl cellulose, and butyl cellulose, vinyl resins such as polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, and polyvinyl pyrodrine, styrene-butadiene copolymer, styrene-acrylonitrile Copolymers, copolymer resins such as styrene-butadiene-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, acrylics such as polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, and polyacrylonitrile. Resins, polyesters such as polyethylene terephthalate, poly(4,
4'-isopropylidenediphenylene-co-1,4
-0 cyclohexylene dimethylene carbonate),
Poly(ethylene dioxy-3,3'-phenylene thiocarbonate), poly(4,4-isopropylidene diphenylene carbonate-coterephthalate), poly(4,4'-isopropylidene diphenylene carbonate), poly (4,4′-sec-bridendiphenylene carbonate), poly(4,
Polyarylate resins such as 4'-isopropylidene diphenylene carbonate-block oxyethylene), or polyolefins such as polyamides, polyimides, epoxy resins, phenolic resins, polyethylene, polypropylene, and chlorinated polyethylene, etc. Can be used.

The organic solvent that can be used during coating varies depending on the type of binder and whether the above-mentioned compound is contained in the binder in a dispersed or amorphous state, but in general, , alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N,N-dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, Ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, butyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichlorethylene, or benzene. , toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, and other aromatic compounds.

Coating can be performed using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, a curtain coating method, or the like.

When forming the thin film 2 together with a binder, the content of the azulenium salt compound described above in the thin film 2 is 0.1 to 99% by weight, preferably 40 to 90% by weight. Further, the dry film thickness or vapor deposited film thickness of the thin film 2 is 10 microns or less, preferably 2 microns or less.

As the substrate 1, plastics such as polyester, acrylic resin, polyolefin resin, phenolic resin, epoxy resin, polyamide, polyimide, glass, metals, etc. can be used.

The photothermal conversion recording medium of the present invention is obtained by forming the aforementioned thin film 2 (electromagnetic radiation sensitive layer) on the substrate 1 used as a support, but various auxiliary layers can be provided. For example, it is possible to use a substrate having a surface coating made of an inorganic or organic substance on the surface of the substrate 1 for the purpose of adjusting the thermal constant. Further, a protective layer made of a transparent material can be provided on the thin film 2, and this protective layer is effective in preventing mechanical damage and, by forming it with an appropriate thickness, can prevent reflection. Since it can be formed into a film, it is also effective in improving sensitivity. Also, the second
As shown in the figure, a reflective layer 3 can be provided between the thin film 2 and the substrate 1. This reflective layer 3 can be a vapor deposited layer or a laminate layer of a reflective metal such as aluminum, silver, or chromium.

Furthermore, the photothermal conversion recording medium of the present invention has
It is possible to form a pregroove having a function such as a track guide groove or an address designation groove as described in the specification of No. 72374.

The photothermal conversion recording medium of the present invention, as shown in FIG.
m), argon gas laser (oscillation wavelength: 488.515n)
m), helium-neon gas laser (oscillation wavelength:
632.8 nm) In addition, the pits 5 can be formed by irradiating or contacting with various short pulse light emitting lamps such as a laser having an oscillation wavelength from the visible region to the infrared region, a xenon flash lamp, infrared lamp light, or a heater. can. The reflectance of the pit-formed portion is different from that of the non-pit-formed portion. Therefore, by scanning electron radiation along a track, for example, a pit is formed, and the pit-formed portion and the pit-free portion are separated. A low power laser is scanned along the aforementioned track and the difference in reflectance can be read by a photodetector.

In another specific example of the present invention, it can be applied as a liquid crystal element using a photothermal conversion recording method. for example,
As shown in FIG. 4, a cross-sectional view of a liquid crystal element which is an example of the photothermal conversion recording medium of the present invention, the liquid crystal composition 108
As the liquid crystal, a liquid crystal in which an azulenium salt compound represented by the above-mentioned general formula [] is dissolved is used.
Smectic liquid crystal is suitable for the liquid crystal used in the liquid crystal element applied to the photothermal conversion recording medium of the present invention.
In particular, the A of smectic liquid crystals with positive dielectric anisotropy
Phase or C phase is suitable. Such smectic liquid crystals are arranged in the smectic phase of a homeotropic structure until they are locally heated by a laser beam, and can undergo a phase change from the smectic phase of the homeotropic structure to the neomatic phase to the isotropic phase as the temperature rises. . Next, when the phase is changed from the isotropic phase to the smectic phase under rapid cooling, a smectic phase with a focal conic structure having light scattering properties is formed. Therefore, when the smectic phase in a liquid crystal element is locally heated to an isotropic phase by irradiation with a laser beam, and then rapidly cooled, the area becomes a smectic phase of a focal conic structure, and this state has light scattering properties. Therefore, a still image pattern can be formed by scanning the optical signal with the preceding laser beam.

Compounds capable of forming a smectic phase with positive dielectric anisotropy used in the liquid crystal element of the present invention include:
For example, JP-A-56-150030, JP-A-57-
Compounds described in JP-A-40429, JP-A-57-51779, etc. can be used.

The azulenium salt compound represented by the general formula [] is added to the liquid crystal composition 1 in an amount of 0.1% by weight or more, preferably in the range of 1% to 3% by weight based on the liquid crystal.
08.

Further, the liquid crystal element of the present invention can also use a mixed liquid crystal of a smectic liquid crystal and a cholesteric liquid crystal having positive dielectric anisotropy. The cholesteric liquid crystal is suitably contained in the liquid crystal composition 108 in an amount of 0.5% to 15% by weight, preferably 1% to 5% by weight.

Cholesteric liquid crystals that can be used in the present invention include cholesteryl chloride, cholesteryl bromide, cholesteryl iodide, cholesteryl nitrate, cholesteryl chlorodecanoate,
Cholesteryl butyrate, cholesteryl caprate, cholesteryl oleate, cholesteryl linoleate, cholesteryl laurate, cholesteryl myristate, cholesteryl heptycarbamate,
Examples include cholesteryl compounds such as cholesteryl decyl ether, cholesteryl lauryl ether, and cholesteryl oleyl ether.

A liquid crystal element using such a mixed liquid crystal undergoes a phase change from a homeotropic smectic phase to an isotropic phase by local heating with a laser beam, and when this is rapidly cooled, a focal conic structure smectic phase is formed as described above. Can be done.

A liquid crystal element recorded by the above-mentioned method is produced by heating the entire surface of the liquid crystal composition 108 using, for example, a heater to change the phase to an isotropic phase, and then applying the liquid crystal composition 108 to the substrates 101 and 102 (for example,
By applying an appropriate direct current or alternating current between the electrodes 103 and 104 provided on a plastic plate (such as a transparent glass plate or an acrylic plate) and slowly cooling it, a phase change occurs from an isotropic phase to a nematic phase to a smectic phase. can occur. At this time, since the liquid crystal has a positive dielectric anisotropy in the nematic phase, the nematic liquid crystal is aligned in the direction of the electric field, and when it is further cooled, a smectic A phase or C phase with a homeotropic structure is formed, and the written image pattern is formed. will be deleted. Electrodes 103 and 104
In the general formula, indium oxide, tin oxide or
It can be obtained with a transparent conductive film of ITO (Indium Tin Oxide), and if necessary, with a conductive film of metal such as aluminum, chromium, silver, or nickel. The electrodes 103 and 104 are desirably coated over the entire surfaces of the substrates 101 and 102, and do not necessarily have to have a predetermined pattern shape or matrix electrode structure. However, it is also possible to design a predetermined pattern shape or matrix electrode structure as desired.

In the liquid crystal element of the present invention, alignment control films 106 and 107 made of insulating material films can be provided on the electrodes 103 and 104, respectively. The alignment control films 106 and 107 have a surface structure capable of controlling the alignment direction of the liquid crystal composition 108 that is in contact with these critical surfaces to a desired state.
The alignment control films 106 and 107 also function as insulating films that can prevent the generation of current flowing through the liquid crystal composition 108. This type of alignment control films 106 and 107 are made of, for example, silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride, polyvinyl alcohol, polyimide. Insulating materials such as polyamideimide, polyesterimide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, acrylic resin, organosiloxane, polyethylene fluoride, etc. It can be obtained by forming a film using a vapor deposition method, a dip coating method, a spinner coating method, or a spray coating method.

The alignment control films 106 and 107 are coated with the liquid crystal composition 10 by rubbing the surface with cloth, paper, velvet, etc., or by using an oblique vapor deposition method when forming the film, depending on a predetermined writing method.
It is possible to have a surface structure that homogeneously aligns 8, or the surface can be
Silane compounds having a barfluoroalkyl group described in JP-A No. 36150, alkyltrialkoxysilanes described in JP-A-50-50947, tetraalkoxysilanes described in JP-A-50-63955, etc. By treating with a compound, the liquid crystal composition 108 can have a surface structure that provides homeotropic alignment.

The optimum film thickness of the alignment control films 106 and 107 varies depending on the type of insulating material used, but is generally in the range of 100 Å to 1 μ, preferably 500 Å to 1 μ.
It is suitable to set the thickness in the range of Å to 2000 Å, and it is also desirable to set the thickness so that the alignment control films 106 and 107 also function as antireflection films.

Further, the liquid crystal element of the present invention forms the above-mentioned still image by irradiating the laser beam 110 from the rear direction as shown in the figure, and also receives natural light and light from the front direction.
The above-mentioned still image can be observed by making observation light 109 such as halogen lamp light, xenon lamp light, or fluorescent lamp light enter the element and using this light beam as reflected light from the cold mirror 105. This cold mirror 105 generally has sufficiently high reflectance for visible light and high transmittance for long wavelength light of 600 nm or more.
Specifically, Ge/MgF ₂ (1/4λ)/CeO ₂ (1/4
A multilayer film consisting of λ)/MgF ₂ (1/4λ)/CeO ₂ (1/4λ) is known. However, in the present invention, the use of cold mirror 105 can also be omitted.
Further, in the element of the present invention, a cold filter (not shown) can be provided between the electrode 103 and the alignment control film 106. This cold filter has a sufficiently high transmittance for visible light and a sufficiently high reflectance for long wavelength light.

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

Example 1 Nitrocellulose solution (Daicel Chemical Industries, Ltd.)
Manufactured by Ohares Latzker: Nitrocellulose 25
12 parts by weight of methyl ethyl ketone solution), 3 parts by weight of the aforementioned compound No. (1), and 70 parts by weight of methyl ethyl ketone were thoroughly mixed in a ball mill. This mixed solution was applied onto a disk-shaped aluminum vapor-deposited glass plate with a diameter of 30 cm by a spinner coating method, and then dried to obtain a recording layer of 0.6 g/m ² .

The optical disk recording medium created in this way is mounted on a turntable, and the turntable is driven by a motor.
Spot size while giving 1000rpm rotation
Recording was carried out by scanning a gallium-aluminum-arsenic semiconductor laser (oscillation wavelength: 780 nm) on the surface of the recording layer in a track-like manner with an output of 5 mW and a pulse width of 8 MHz, which was focused to 1.0 microns.

When the recorded surface of the optical disc was observed using a scanning electron microscope, clear pits were observed. Furthermore, when a low-output gallium-aluminum-arsenic semiconductor laser was incident on this optical disk and reflected light was detected, a waveform with a sufficient S/N ratio was obtained.

In addition, in order to measure the durability stability over time after recording, the recorded recording medium was heated to 35°C.
After being left in a forced environment at ℃ and 95% relative humidity for 240 hours, the surface of the recorded recording medium was observed under a microscope in the same manner as described above, and pits similar to those observed before the durability test were observed. . Furthermore, when a low-power gallium-arsenic-aluminum semiconductor laser was incident on this recorded and durability-tested recording medium and the reflected light was detected, a waveform with a sufficiently high S/N ratio was obtained. Ta.

Example 2 The above compound No. (3) was coated on a disk-shaped aluminum vapor-deposited glass plate with a diameter of 30 cm using the spinner coating method in the same manner as in Example 1.
An optical disc recording medium having a recording layer of 0.6 g/m ² was prepared.

When information was recorded on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed.
Further, a durability test after recording was carried out in the same manner as in Example 1, and similar results were obtained.

Example 3 The above-mentioned compound No. (6) was coated on a disk-shaped aluminum vapor-deposited glass plate with a diameter of 30 cm using the spinner coating method in the same manner as in Example 1.
An optical disc recording medium having a recording layer of 0.6 g/m ² was prepared.

When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Further, a durability test after recording was carried out in the same manner as in Example 1, and similar results were obtained.

Example 4 The above compound No. (8) was coated on a disc-shaped aluminum vapor-deposited glass plate with a diameter of 30 cm using the spinner coating method in the same manner as in Example 1.
An optical disc recording medium having a recording layer of 0.8 g/m ² was prepared.

When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Further, a durability test after recording was carried out in the same manner as in Example 1, and similar results were obtained.

Example 5 The above compound No. (10) was coated on a disc-shaped aluminum vapor-deposited glass plate with a diameter of 30 cm using the spinner coating method in the same manner as in Example 1.
An optical disc recording medium having a recording layer of 0.6 g/m ² was prepared.

When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Further, a durability test after recording was carried out in the same manner as in Example 1, and similar results were obtained.

Example 6 The above-mentioned compound No. (15) was coated on a disk-shaped aluminum vapor-deposited glass plate with a diameter of 30 cm by spinner coating method in the same manner as in Example 1 to form a recording layer of 0.8 g/m ^{2 .} An optical disc recording body having the following was created.

When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Further, a durability test after recording was carried out in the same manner as in Example 1, and similar results were obtained.

Example 7 The above-mentioned compound No. (20) was coated on a disk-shaped aluminum vapor-deposited glass plate with a diameter of 30 cm by spinner coating method in the same manner as in Example 1 to form a recording layer of 0.6 g/m ^{2 .} An optical disc recording body having the following was created.

When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Further, a durability test after recording was carried out in the same manner as in Example 1, and similar results were obtained.

Example 8 FIG. 5 shows an example in which a display pattern was formed using the device of the present invention.

Among the compounds represented by the above general formula [], compound No. (1) was added in an amount of 2% by weight to smectic liquid crystal (4,4-cyanooctylbiphenyl; has positive dielectric anisotropy). It was dissolved in proportion. At this time, the liquid crystal composition is heated until it becomes an isotropic phase, the above-mentioned compound is added, and this liquid is injected into a cell whose inner wall surface has been subjected to a homeotropic alignment treatment. A structured smectic phase liquid crystal was formed.

A laser oscillator 202 that emits a laser beam used to write an image on the liquid crystal cell 201
can be selected from those with wavelengths corresponding to the absorption efficiency of the above-mentioned compounds contained in the liquid crystal, but in particular long-wavelength laser beams emitted from helium-neon lasers, semiconductor lasers, or YAG lasers, or argon A short wavelength laser beam emitted by a laser can be used.
A laser beam emitted from a laser oscillator 202 passes through a modulator 203, a slit 204, a Y-axis deflector 205, and an X-axis deflector 206, is modulated and deflected, is focused by a writing lens 208, and is focused by a dichroic mirror. The light is irradiated from the back side of the liquid crystal element 201 via the light source 209 . The aforementioned modulator 2
03, Y-axis deflector 205, X-axis deflector 206,
It is connected to a signal source 211 via a driving amplifier 210, which controls the laser beam and converts the digital electrical signal from the signal source 211 into an optical signal. This optical signal causes the liquid crystal element 20 to
An image pattern is written to 1. After that,
The Peltier element 212 attached to the periphery of the liquid crystal element 201 is activated by the power supply 213 to bring it into a rapid cooling state, thereby cooling the liquid crystal element 201 and forming a smectic phase of a focal conic structure. An image pattern was formed in which spots were in a light scattering state. At this time, Peltier element 2
12 is temperature controlled by a temperature controller 214.

This image pattern is created by lighting the illumination source 215 placed in front of the liquid crystal element 201.
can be observed.

Then, to erase the aforementioned image pattern,
A transparent heater 216 (for example, an indium oxide film, a tin oxide film, an ITO film) provided on the liquid crystal element 201 is connected to a heater power source 2 via a temperature controller 217.
18 to cause a phase change from a liquid crystal phase to an isotropic phase. After that, the liquid crystal element 20
AC power supply 2 between electrodes 219 and 220 provided in 1
The liquid crystal element 201 was slowly cooled while applying a voltage from 21 to form a smectic phase having a homeotropic structure. As a result, the written image pattern was erased.

Comparative Example 1 Example 1 except that a compound with the following structure was used instead of compound No. (1) obtained in Example 1.
An optical disk recording medium was prepared in the same manner as above. Recording was performed on the optical disk recording body thus prepared in the same manner as in Example 1, and when the recorded optical disk surface was observed with a scanning electron microscope, clear pits were observed. Furthermore, when a low-power gallium-aluminum-arsenic semiconductor laser was incident on this optical disk and the reflected light was detected, a sufficient S/N ratio was obtained.
A waveform with a ratio was obtained.

On the other hand, in order to measure the durability stability over time, the above-mentioned recorded optical disc was left under the same conditions as in Example 1.

When the surface of this optical disk was observed with a microscope, pits similar to those observed before the durability test were observed, but a low-power gallium-aluminum-arsenic semiconductor laser was incident on this optical disk and the reflected light was detected. As a result, a decrease in the S/N ratio value was observed compared to Example 1.

[Effects of the Invention] The effects of the present invention are listed below.

The photothermal conversion recording medium of the present invention has a thin electromagnetic radiation sensitive layer that has a high absorption efficiency for electromagnetic radiation, and enables recording with a low energy density helium-neon gas laser or xenon flash lamp, and moreover, on the long wavelength side. It is also effective for recording using a semiconductor laser having an oscillation wavelength. Furthermore, the S/N ratio is high and the regeneration efficiency is good. Furthermore, the azulenium salt compound of the present invention has superior thermal stability compared to conventionally known azulenium salt compounds.

Further, the liquid crystal element related to the photothermal conversion recording medium of the present invention can be applied as a large screen display, and can also be used in a recording method in which optical signals containing predetermined information are scanned along a track to form pits. It can also be applied to optical disk systems.

[Brief explanation of drawings]

1 and 2 are sectional views of the photothermal conversion recording medium for optical disks of the present invention, respectively. Figure 3 shows
FIG. 2 is an explanatory diagram showing an embodiment of a photothermal conversion recording medium. FIG. 4 is a cross-sectional view of a liquid crystal element showing an example of the photothermal conversion recording medium of the present invention. FIG. 5 is an explanatory diagram showing one example of a display method using the liquid crystal element of the present invention. 1: Substrate, 2: Thin film, 3: Reflective layer, 4: Electromagnetic radiation, 5: Pit, 101, 102: Substrate, 10
3,104: Electrode, 105: Cold mirror, 1
06,107: Orientation control film, 108: Liquid crystal composition, 109: Observation light, 110: Laser beam.

Claims (1)

[Scope of Claims] 1. A photothermal conversion recording medium characterized by containing an azulenium salt compound represented by the following general formula []. General formula [] [However, in the general formula [], R ₁ , R ₂ , R ₃ ,
R ₄ , R ₅ , R ₆ and R ₇ are hydrogen atoms, halogen atoms, monovalent organic residues, or R ₁ and
R ₂ , R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₅ and R ₆ and
Represents a substituted or unsubstituted condensed ring formed by at least one combination of R ₆ and R ₇ . R ₈ and R ₉ represent any one of a substituted or unsubstituted alkyl group, aryl group, or aralkyl group, or a ring formed by R ₈ and R ₉ together with a nitrogen atom. Ar ₁ and Ar ₂ represent substituted or unsubstituted arylene groups, and Z represents an anion residue. 2. The photothermal conversion recording medium according to claim 1, wherein the photothermal conversion recording medium is formed by forming a coating containing an azulenium salt compound represented by the following general formula [] on a substrate. General formula [] [However, in the general formula [], R ₁ , R ₂ , R ₃ ,
R ₄ , R ₅ , R ₆ and R ₇ are hydrogen atoms, halogen atoms, monovalent organic residues, or R ₁ and
R ₂ , R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₅ and R ₆ and
Represents a substituted or unsubstituted condensed ring formed by at least one combination of R ₆ and R ₇ . R ₈ and R ₉ represent any one of a substituted or unsubstituted alkyl group, aryl group, or aralkyl group, or a ring formed by R ₈ and R ₉ together with a nitrogen atom. Ar ₁ and Ar ₂ represent substituted or unsubstituted arylene groups, and Z represents an anion residue. 3. The photothermal conversion recording medium according to claim 1, wherein the photothermal conversion recording medium comprises a liquid crystal element having a liquid crystal composition containing an azulenium salt compound represented by the following general formula []. General formula [] [However, in the general formula [], R ₁ , R ₂ , R ₃ ,
R ₄ , R ₅ , R ₆ and R ₇ are any one of a hydrogen atom, a halogen atom or a monovalent organic residue, or R ₁ and
R ₂ , R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ , R ₅ and R ₆ and
Represents a substituted or unsubstituted condensed ring formed by at least one combination of R ₆ and R ₇ . R ₈ and R ₉ represent any one of a substituted or unsubstituted alkyl group, aryl group, or aralkyl group, or a ring formed by R ₈ and R ₉ together with a nitrogen atom. Ar ₁ and Ar ₂ represent substituted or unsubstituted arylene groups, and Z represents an anion residue. ]