Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
  • G11B7/246—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing dyes
  • G11B7/248—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing dyes porphines; azaporphines, e.g. phthalocyanines
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
  • G11B7/0045—Recording
  • G11B7/00453—Recording involving spectral or photochemical hole burning
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
  • G11B7/245—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing a polymeric component
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
  • G11B7/246—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing dyes
  • G11B7/2467—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing dyes azo-dyes
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
  • G11B7/244—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only
  • G11B7/249—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising organic materials only containing organometallic compounds

Definitions

• the present invention relates to a new method for optical data storage in a material comprising a carrier and a storage layer which contains a matrix of inorganic or organic material and a chromophore which is adsorbed on the matrix surface, the light having different frequencies in the storage layer spectral holes are generated in the absorption bands of the chromophore.
• Information is stored optically in a large number of storage systems, for example in CD-ROM memories.
• the storage density is 10 to 100 times higher than with conventional magnetic storage devices, but the maximum achievable density is limited to approx. 108 bit / cm2 by the two-dimensional point storage on the surface of the storage medium.
• the reason for this limitation is that a laser beam with a wavelength of approx. 800 nm, as is generally used for reading out information from optical storage systems, cannot be focused further than approx. 1 ⁇ m2 by diffraction phenomena, so that no more than 108 points per cm2 can be optically distinguished.
• FDOS frequency domain optical storage
• FDOS makes use of the fact that chromophores, for example chromophoric molecules, atoms, ions or their aggregates, which are embedded in host matrices which are not strictly organized, for example in real crystals or glasses (polymers or frozen solvents), form a strong inhomogeneous ver - Show broadening of the spectral lines in absorption and emission. This is due to the large number of slightly different installation positions ("sites") that the chromophores can occupy in the matrix. By overlaying the Due to these different installation positions of shifted absorption lines, there is an inhomogeneously broadened absorption band with the half width T.
• chromophores for example chromophoric molecules, atoms, ions or their aggregates, which are embedded in host matrices which are not strictly organized, for example in real crystals or glasses (polymers or frozen solvents
• An absorption or excitation spectrum detected after firing shows a spectral hole at the location of the firing frequency.
• the homogeneous line width r ⁇ * can be determined from the line shape function of the hole.
• the homogeneous line width r-. j rises sharply with increasing temperature and has approximately the same value as the half-value width T j of the absorption band in all systems, even far below room temperature. For this reason and due to the strong electron-phonon coupling, a very low temperature (approx. 4 K) is generally required for spectral hole burning, with liquid helium being used as the coolant.
• the maximum achievable storage density of optical memories can be increased in the following way:
• the frequency of the laser is varied at a focused laser point, so that spectral holes are burned at certain frequency intervals in the absorption band of the molecules exposed to light in the focus become.
• the hole / non-hole pattern generated in this way then contains the bit coding.
• the frequency bit coding at a sampling point can be read out quickly using different methods, for example using frequency modulation techniques.
• the storage density that can be achieved in the frequency dimension depends on how many holes can be burned in the inhomogeneous band of the storage medium, which can be expressed by the ratio of the half-width of the inhomogeneous band r j .homogeneous line width (hole width) r H. In known systems, this ratio is generally 102 to 10- +.
• the capacity of a perforated combustion memory thus expands to approx. 1011 bit / cm 2 and is thus significantly higher than the storage density of conventional optical storage media, which, as already explained, cannot achieve a storage density greater than approx. 108 bit / cm 2 for optical reasons .
• the invention is therefore based on the object of providing a new method for frequency-selective optical data storage in which spectral holes in absorption bands of chromophoric substances can be generated at temperatures such as are achieved by cooling with liquid nitrogen using light of different frequencies.
• optical data storage in a material containing a support and a storage layer which contains a matrix of inorganic or organic material and a chromophore with spectral holes in the absorption bands with light of different frequencies in the storage layer of the chromophore can be achieved advantageously if one uses a matrix that
• a) is microporous, the pore size of the matrix being greater than the molecular diameter of the chromophore, or b) has a cage structure or c) has a layer structure, where the chromophore is adsorbed on the matrix surface, and the spectral holes in the absorption bands of the chromophore are generated at a temperature of 50 50 K.
• the material used in the method according to the invention has a carrier, with transparent carriers such as glass or plastics being suitable as carriers.
• Suitable plastics are, for example, poly (meth) acrylates, polycarbonates, polyesters, epoxies, polyolefins, e.g. Polymethylpentene, polyamide, polyvinyl chloride, polystyrene 10 or polyvinyl ester.
• the storage layer of the material used in the method according to the invention contains a matrix and a chromophore.
• the matrix consists of inorganic or organic material. she is
• microporous the pore size of the matrix being greater than the molecular diameter of the chromophore, or b) a cage structure or c) a layer structure.
• the matrix is microporous, it usually has an amorphous or microcrystalline structure with a heterogeneous surface.
• the matrix can furthermore also have a surface within a cage or layer structure 25 which permits the chromophore to be embedded or intercalated. Structures of this type provide a number of places with different energies.
• Suitable microporous inorganic matrices are e.g. from the series of 30 aluminum oxides, such as ⁇ -aluminum oxide, ⁇ -aluminum oxide, 3r-aluminum oxide or ⁇ -aluminum oxide, or the silicon dioxide, such as silica gel or diatomaceous earth.
• Suitable microporous organic matrices can be built up, for example, from small spherical polymer particles (diameter: approx. 10 to 10,000 nm), the space between the particles representing the micropores. Such products are known per se and are used, for example, as calibration standards in electron microscopy. They come, for example, from the polystyrene series (US-A-4 937 171). Suitable inorganic matrices with a cage structure come, for example, from the series of zeolites or non-zeolitic molecular sieves.
• Zeolites are crystalline aluminosilicates which have a highly ordered structure with a rigid three-dimensional network of SiO 4 or Al 4 tetrahedra 5 which are connected by common oxygen atoms.
• the ratio of the silicon and aluminum atoms to oxygen is 1: 2 (see Ullmanns Encyclopedia of Industrial Chemistry, 4th edition, volume 24, page 575).
• the electrovalence of the tetrahedra containing aluminum is due to the inclusion of cations in the crystal, for example one Alkali metal 10 or hydrogen ions, balanced. A cation exchange is possible.
• the spaces between the tetrahedra are occupied by drying or calcining water molecules before dehydration.
• Zeolites are divided into different groups according to their structure.
• the tetrahedra In the case of the mordenite group, chains or in the case of the chabasite group, layers of tetrahedra form the zeolite structure, while in the faujasite group the tetrahedra are arranged in polyhedra, e.g. in the form of a cubo-octahedron made up of four or six rings.
• zeolites of type A, L, X or Y are arranged in polyhedra, e.g. in the form of a cubo-octahedron made up of four or six rings.
• Zeolites which are suitable for the process according to the invention are those from the mordenite group, narrow-pore zeolites of the erionite or chabasite type or zeolites of the faujasite type, e.g. Y, X or L zeolites. 25 This group of zeolites also includes the so-called “ultra-stable" zeolites of the faujasite type, i.e. dealuminated zeolites. Methods of making such zeolites are e.g. in US-A-4,512,961.
• the basic building block 30 has in common a five-membered ring made of SiO 4 tetrahedra. They are characterized by a high Si0 2 : Al 2 ⁇ 3 ratio and by pore sizes between those of type A zeolites and those of type X or Y.
• Suitable inorganic matrices with a layer structure come e.g. from the range of clays, such as bentonite or montmorillonite.
• Suitable organic matrices with a layer structure can be built up, for example, from suitable plastic films lying one above the other.
• a method of operation is preferred in which a storage layer A is used which has a matrix of inorganic material.
• Such matrices have a high temperature resistance, high strength and a favorable adsorption capacity.
• a storage layer which has a microporous matrix, matrices from the series of aluminum oxides or silicon dioxide being preferred.
• matrices with a specific surface area of at least 30 m2 / g and preferably at least 100 m2 / g should be mentioned in particular.
• the chromophore contained in the storage layer of the material is e.g. a dye into consideration, which is optically excitable with a laser. Dyes which absorb in the wavelength range of approximately 400 to 1100 nm are preferably used.
• Suitable chromophores are e.g. from the class of anthraquinone, phthalocyanine, porphyrin, carbazole or oxazine dyes.
• chromophores that can be used in the process according to the invention are e.g. Dyes from the class of naphthalocyanine dyes, methine dyes, squaric acid dyes, azo dyes, di- or triphenylmethane dyes, metal complex dyes, thiazine dyes, phenazine dyes, indigoid dyes or metal dithiolenes.
• a procedure is preferred in which a chromophore from the class of the anthraquinone, oxazine, porphyrin or phthalocyanine dyes is located in the storage layer of the material.
• a method in which a chromophore from the class of the anthraquinone or oxazine dyes is located in the storage layer of the material is particularly preferred.
• Quinizarin or cresyl violet is located as a chromophore in the storage layer of the material.
• the chromophore is adsorbed on the matrix surface.
• Adsorption in the sense of the invention includes both physisorption, ie the formation of hydrogen bonds or van der Waalschen bonds between the chromophore and the matrix surface, and chemisorption, ie the formation of ionic bonds, covalent bonds or coordinative bonds between chromophore and matrix surface, understood.
• the chromophore can be adsorbed onto the matrix surface directly or also by means of an external functional group (e.g. a basic or acidic residue) which is linked to the chromophore via a spacer.
• an external functional group e.g. a basic or acidic residue
• the adsorption of the chromophore on the matrix surface takes place according to methods known per se.
• the matrix can be treated with a solution of the chromophore in a solvent.
• Suitable solvents are e.g. Methanol, ethanol, propanol, isopropanol, butanol, diacetone alcohol, methyl ethyl ketone, benzene, toluene, bromoform, 1, 1,2-trichloroethane, methylene chloride, diethyl ether, methyl isobutyl ether, chloronaphthalene or mixtures thereof.
• water or a compatible mixture with the solvents mentioned above can also be used.
• the solution expediently has a concentration of dissolved chromophore of 10-6 to 10 -3 moi / i.
• the matrix can then be dried at a temperature of 0 to 150 ° C.
• the drying step is expediently carried out under reduced pressure (for example 10 ⁇ 5 to 1 mbar) in order to ensure that the solvent is completely removed.
• the amount of chromophore which is adsorbed on the matrix surface in the process according to the invention is generally 10 -7 to 10 -3 mol chromophore / g matrix, preferably 10 ⁇ 6 to 10 _
• the storage layer thus obtained can then be placed on the carrier. It is also possible to first apply the untreated matrix to the support and then to carry out the treatment with the chromophore solution.
• the matrix is applied to the carrier by methods known per se, for example a matrix dispersion in an inert solvent (see the solvents mentioned above by way of example), optionally in the presence of auxiliaries, for example binders or adhesion promoters, by knife coating, Spin, pour or dip are placed on the support, followed by a drying process (temperature: 0 to 150 ° C, pressure 10 _ 5 to 1 mbar). It is also possible to fill the storage layer into glass or suitable plastic containers (for example in glass tubes) and to melt them.
• Suitable light sources in the process according to the invention are light sources which emit narrowband light and are continuously tunable, for example tunable dye lasers, tunable solid-state lasers, e.g. the titanium sapphire laser, or semiconductor laser.
• the temperature at which the spectral holes are generated in the absorption bands of the chromophore in the process according to the invention is 50 50 K, preferably 77 77 K.
• This temperature range is e.g. achieved if you cool the material with liquid nitrogen.
• the spectral holes in the absorption bands of the chromophore produced in the process according to the invention generally have a hole width of 25 10 to 20 cm -1, so that the storage space increase on the frequency axis ⁇ I / Ti) is in the range of 50 to 100 bits / absorption band. Together with a local maximum storage density of 108 bits / cm2, this results in a total storage density of 5 • 109 to 1010 bits / cm2.
• the spectral holes produced in the method according to the invention are detected by transmission, and in the case of non-transparent materials by means of fluorescence excitation spectroscopy.
• the information is also read at a temperature of> 50 K, preferably ⁇ 77 K.
• the method according to the invention can be carried out using a chromophore which has a two-photon four-level system (2P4N system), such as e.g. in US-A-4,458,345.
• 2P4N system two-photon four-level system
• the advantage of the method according to the invention is that it can be carried out at a much higher temperature than the previous methods, so that cooling with liquid helium can be dispensed with.
• the following examples are intended to explain the invention in more detail.
• the storage material obtained in this way which had an occupancy of dye of 0.1%, based on the specific surface area (BET) of 3r aluminum oxide, was melted into a glass cuvette (internal dimensions: 1 mm ⁇ 10 mm ⁇ 20 mm).
• the material obtained in this way was cooled to 80 K with liquid nitrogen.
• the material was produced as in Example 1. Instead of the quinizarin solution, however, a solution of 10 -7 mol cresyl violet in 20 ml methanol was used.
• the storage material obtained had an occupancy of approximately 0.5%, based on the specific surface area (BET) of j-aluminum oxide.
• BET specific surface area
• holes were produced in the absorption band of cresyl violet at 80 K within 600 seconds with a power density of 42 mW / cm2.
• the half width * ⁇ of the spectral holes was 15 cm ---. Its depth was 1%.
• Examples 1, 2 and 4 show that, compared to Examples 3 and 5 (1.6 K), the hole width in Examples 1, 2 and 4 (80 K) increases significantly, but is still so narrow that approx. 10 up to 100 holes (corresponding to an increase in the number of bits from 10 to 100 per laser spot) can be produced in the absorption band.

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• 1991
  • 1991-05-13 WO PCT/EP1991/000912 patent/WO1991020078A1/de not_active Application Discontinuation
  • 1991-05-13 JP JP91509261A patent/JPH05507807A/ja active Pending
  • 1991-05-13 EP EP91910104A patent/EP0535009A1/de not_active Withdrawn
• 1992
  • 1992-12-21 KR KR1019920703288A patent/KR930701807A/ko not_active Application Discontinuation

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