Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/36—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties
  • B41M5/363—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties using materials comprising a polymeric matrix containing a low molecular weight organic compound such as a fatty acid, e.g. for reversible recording

Definitions

• the invention relates to dispersion solutions and dispersion layers, consisting essentially of a polymer and a low molecular weight organic substance, which acts as an inclusion compound.
• All types of information can be recorded on transparent media if they are to be stored visually.
• These information carriers mostly consist of a transparent carrier material on which a dispersion layer containing a (co) polymer and an inclusion compound incorporated therein is applied. If the dispersion layer is self-supporting, it is also possible, if necessary, to dispense with a carrier layer.
• Suitable bistable reversible layers are known from DE-A-2 907 352.
• low molecular weight organic substances such as docosanic acid or docosanol are dispersed in the polymer matrix, for example made of polyester, a copolymer of vinylidene chloride and acrylonitrile or a copolymer of vinyl chloride and vinyl acetate.
• Deleted recording materials can therefore be used again for data recordings.
• the heat required for image generation can be supplied in any manner, preferably by means of finely bundled infrared or light radiation or by contact heat, for example from electrical conductor tracks. The finer the radiation and the dimensions of the conductor tracks, the sharper the recordings can be obtained.
• Laser beams are used to achieve a maximum resolution of a few micrometers in the dispersion layers mentioned in DE-A-2 907 352.
• dispersion layers according to DE-OS are out of the question because of their insufficiently high resolving power.
• the object was therefore to provide a dispersion solution which can be processed into a bistable reversible dispersion layer, the resolution of which is improved to such an extent that recordings of 1 ⁇ m and below are possible.
• the object is achieved by providing a dispersion solution containing a polymer and a low molecular weight organic substance which acts as an inclusion compound, characterized in that the dispersion solution also contains a monomer and, if appropriate, an initiator.
• Thermoplastic or thermosetting plastics as well as natural and synthetic resins can be used as matrix materials in the dispersion solution according to the invention. In addition, they should be able to form mechanically stable layers and be film-forming. Polyesters, polyamides, polystyrene, polyacrylates and polymethacrylates and silicone resins, preferably with molecular weights of 10,000 to 20,000, are suitable. Among the polyesters, the high molecular weight, linear and saturated polyesters are particularly suitable. Polyvinylidene chloride-acrylonitrile copolymers, polyvinyl chloride, vinyl chloride-vinyl acetate and other vinyl acetate copolymers and / or polyester are particularly preferred. The polymers or copolymers are described in DE-A-2 907 352.
• DE-A-2 907 352 also discloses the low molecular weight organic substances which are suitable for the dispersion layers according to the invention and which act as inclusion compounds.
• the compounds mentioned preferably consist of 10 to 60, in particular 10 to 38 and particularly preferably 10 to 30, carbon atoms, which are straight-chain Form a chain.
• Halogen is chlorine and bromine, but especially chlorine.
• a phenyl or a substituted phenyl group is preferred as the aryl.
• these compounds have at least one heteroatom, e.g. Oxygen, nitrogen, sulfur and / or halogen.
• heteroatom e.g. Oxygen, nitrogen, sulfur and / or halogen.
• Higher fatty acids and their derivatives are particularly preferred. These include docosanoic acid, docosanol, stearic acid, arachic acid and mellissic acid.
• the molecular weights of the inclusion compounds are in the range from 100 to 700, preferably from 300 to 500.
• the weight ratio of low molecular weight organic substance and matrix material is in the range from 1: 3 to 1:16, preferably from 1: 6 to 1:12.
• acrylates and methacrylates of mono- and polyhydric, straight or branched chain alcohols can be used as monomers.
• Preferred alcohol components consist of 2 to 10, preferably 4 to 6 carbon atoms and in particular carry two terminal hydroxyl groups.
• a third hydroxyl group can be present in addition, preferably not adjacent to one of the terminal hydroxyl groups. Examples include 1,6-hexanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate and trimethylolpropane tri (meth) acrylate.
• Both radical starters and thermal starters can be used as initiators.
• radical starters ®Irgacure 651 Ph-CO-C (OCH3) 2-Ph
• benzil benzoin, methyl ether, ethylanthraquinone and benzophenone and their derivatives are suitable.
• the initiators are used in concentrations of 0.5 to 5% by weight, preferably 1 to 3% by weight, based on the weight of the solution.
• dyes into the coating solution as UV or IR absorbers. All temperature and light stable dyes are suitable.
• soot has also proven itself.
• the blue copper phthalocyanine can be used, for example, to increase the absorption of red He / Ne laser light, while soot is advantageous for a rather broad-band absorption, from the ultraviolet to the infrared spectral range.
• the absorbents should be as soluble as possible in the coating solution and are predominantly in parts by weight from 1 to 15 wt .-%, based on the weight of the solution, incorporated.
• a special embodiment consists of, before applying the coating solution, the layer support with an absorption layer made of an optical aid that is suitable for this layer, such as e.g. To coat copper phthalocyanine or carbon black, and the actual coating solution, but now preferably without an absorbent contained therein, on this intermediate layer.
• an absorption layer made of an optical aid that is suitable for this layer, such as e.g. To coat copper phthalocyanine or carbon black, and the actual coating solution, but now preferably without an absorbent contained therein, on this intermediate layer.
• the coating solutions can also contain a solvent or solvent mixture which should be compatible with all other constituents of the layer and moreover must have a boiling point which makes it possible for the solvent to be removed from the coating solution by evaporation.
• a solvent or solvent mixture which should be compatible with all other constituents of the layer and moreover must have a boiling point which makes it possible for the solvent to be removed from the coating solution by evaporation.
• tetrahydrofuran trichlorethylene and butyl ethyl ketone are also suitable as solvents.
• the monomer contained in the coating solution preferably takes over the function of the solvent, it being possible for the monomer to be blended with the solvent with up to 30% of its proportion in the dispersion solution without impairing the solubility and the crosslinking.
• the coating solutions or the bistable reversible dispersion layers produced therefrom can be produced in various ways.
• One method is to mix the polymer, the low molecular weight organic substance as well as the monomer and the initiator and possibly the substances to improve the optical properties, to a certain temperature, which depends on the chosen starter, and thus the possibly to coat the heated substrate. This is to ensure that the inclusion compound remains dissolved for as long as possible and thus avoid the precipitation of coarse particles before the crosslinking reaction begins.
• the liquid monomer present in the solution takes over the function of the solvent.
• the organic substance, the polymer, the monomer and the initiator and, if appropriate, the substances for improving the optical properties are dissolved in a solvent, in particular tetrahydrofuran, and then the solvent evaporated while shaping the matrix material.
• a solvent in particular tetrahydrofuran
• the temperatures chosen here correspond to those which are also used in the first method, so that the crosslinking reaction which begins can prevent the precipitation of coarse particles of the inclusion compound.
• the third method is to melt the coating components presented above with the exception of the solvent.
• the crosslinking reaction is triggered by the action of UV light.
• the selected temperature in accordance with the three production methods of the bistable reversible dispersion layer described above, plays a minor role and can range from room temperature to 70 ° C., preferably from 30 to 50 ° C.
• heating the solution to trigger the crosslinking reaction when using the thermal starter is necessary.
• these temperatures are between 30 and 80 ° C., preferably between 40 and 70 ° C.
• the shape i.e. the transfer of the coating components into the bistable reversible dispersion layer can be carried out using all known shaping processes.
• the components of the coating solution can be mixed in an extruder and then shaped into foils or plates using a slot die. In this case, the layers are self-supporting.
• the coating solutions which have previously been heated to a necessary temperature, onto a possibly heated substrate, such as a glass plate or a plastic film, possibly with a reflection layer, and to polymerize there.
• the coating solution applied in this way is preferably covered with a cover film or layer to protect it against oxygen.
• the thickness of the coating can be varied as desired and is generally between about 10 ⁇ 6 m and a few millimeters. Coating thicknesses in the range of 10 ⁇ m and 10 ⁇ m are preferred.
• the coating thickness of the absorption layer which can also be as thin as 10 ⁇ 7 m.
• the recordings can be made both by heat and by light, both a positive process and a negative process being possible.
• the bistable reversible dispersion layer is brought to a temperature T 1, the quenching temperature, and then cooled to room temperature. Then you can use e.g. a laser by regional heating above a temperature T2, the turbidity temperature, opaque images can be created on the layer. After cooling to room temperatures, these images are stable, but can again be erased by heating to a temperature T 1 due to the reversibility of the layer.
• image areas of maximum cloudiness are gradually heated by heating to a temperature between room temperature and T 1, depending on the temperature selected brightened, that is, designed increasingly transparent.
• halftones can be achieved if the finished image is exposed to temperatures between room temperature and T 1 in the completely cloudy areas.
• DE-A-2 907 352 describes a coating solution which contains a monomer and / or oligomer and / or prepolymer of the matrix material without a polymer with an organic substance and a hardener incorporated therein. Layers were reworked according to this process, i.e. polymerized. It was found that no reproducible switching temperatures T1 and T2 can be achieved. This is understandable since this process produces polymers with an undetermined molecular weight distribution and thus with non-reproducible temperatures. In contrast, the coating solutions according to the invention have constant results with regard to the quenching temperature and the clouding temperature.
• the coating solutions according to the invention differ from those described in DE-A-2 907 352 in the surprising property of increasing the temperature difference between T 1 and T 2 when using certain monomers, such as methacrylates.
• T1 and thus the Increasing the difference between T1 and T2 reduces the risk of unintentional deletion.
• the differences between the coating solutions according to the invention and those in DE-A-2 907 352 are evident above all from the size of the particles of the inclusion compound in the polymer in the recording layer. While the layers according to DE-A-2 907 352 have particles with an average diameter of 0.3 ⁇ m to 1.2 ⁇ m, the dispersion layers according to the invention only contain particles with a maximum diameter of up to 0.2 ⁇ m.
• the finer structure of the crosslinked dispersion layer according to the invention was determined on the basis of microscopic examinations and by means of scattered light measurements.
• the transparent dispersion layers in the light microscope magnification 640 x
• the uncrosslinked dispersion layers, according to DE-A-2 907 352 the failed inclusion compounds can be seen, while in the crosslinked dispersion layers according to the invention, no structures are found in the transparent sample were recognizable.
• the diameters of the inclusion compounds in the different layers were therefore determined with the scanning electron microscope (SEM) on layer cross sections.
• Scattered light measurements generally provide more accurate results.
• both transparent and cloudy samples are exposed to a vertical, Low-intensity He / Ne laser light exposed and the spatial distribution of the scattered light (forward and backward scattering) measured.
• the size of the ratio of forward and backward scattering in both a transparent and a cloudy sample is a measure of the size of their internal structures. The larger the respective ratio, the larger the structures, ie the inclusion connections.
• the ratios of the dispersion layers according to DE-A-2 907 352 are considerably larger than those which could be determined in the phase according to the invention.
• a coating solution was made from 2 g of a copolymer of vinyl chloride and vinyl acetate, 1 g docosanoic acid and 0.5 g ®Irgacure 651 in 20 ml 1,6-hexane diol diacrylate.
• the clear solution was applied with a doctor blade to a glass plate preheated to 50 ° C. and covered with a polyester film to exclude oxygen. With a high-pressure mercury lamp, the warm layer package was irradiated. In the hardened state, the cover film was peeled off and the approximately 0.3 mm thick layer was lifted off the glass plate.
• the switching temperatures of the layer were determined after this layer had been introduced into a water bath. Temperatures T1 of 71 ° C and T2 of 81 ° C were measured.
• bistable, opaque dispersion layers according to the invention allow a large number of write-erase cycles to be expected.
• a quick method of checking the number of these cycles is to alternately immerse the sample in water baths at temperatures T 1 and T 2. Over 200 cycles were verified on the present sample.
• the measurement method is explained in more detail in the description.
• a coating solution was made from 2 g of a copolymer of vinyl chloride and vinyl acetate, 1 g of stearic acid and 0.5 g ®Irgacure 651 in 20 ml 1,6-hexane diol diacrylate.
• the number of write-erase cycles determined, as well as the results of the scattered light measurements correspond to those from Example 1.
• a coating solution was made from 2 g of a copolymer of vinyl chloride and vinyl acetate, 1 g of stearic acid and 0.5 g ®Irgacure 651 in 20 ml 1,6-hexane diol diacrylate.
• optical He / Ne laser light optical aperture 0.5
• a coating solution was made from 6 g of a copolymer of vinyl chloride and vinyl acetate, 1 g docosanoic acid, 0.7 g copper phthalocyanine, 1 drop of a 16% ®Fluarad solution.
• the clear solution was applied to a polyester film using a centrifuge and the film thus coated was dried at 140 ° C. for 5 minutes.
• the temperature T 1 for the transparent position at 71 ° C. and the temperature T 2 for the cloudy position at 80 ° C. were determined.
• T1 71 ° C
• graded with parallel He / Ne light Intensity radiated 25 ⁇ s had to be irradiated in the present layer until the signal was recognized. It had to be exposed for so long to recognize the recording point in the noise of the recording layer.
• a coating solution was made from 2 g of a copolymer of vinyl chloride and vinyl acetate, 1 g of stearic acid and 0.5 g ®Irgacure 651 in 20 ml 1,6-hexane diol diacrylate.
• a coating solution was made from 2 g a copolymer of vinyl chloride and vinyl acetate, 1 g of stearic acid and 0.5 g R Irgacure 651 in 20 ml 1,6-hexane diol dimethacrylate.
• the clear solution was applied with a doctor blade to a glass plate preheated to 50 ° C. and covered with a polyester film.
• the warm layer package was irradiated with a high pressure mercury lamp. After the layer had hardened completely, the cover film was removed and the approximately 0.3 ⁇ m thick layer was then lifted off the glass plate.
• the switching temperatures could be determined using water baths at different temperatures or with a Kofler bench; the temperature for the transparent position T1 was 110 ° C, that of the cloudy position T2 78 ° C.
• T1 is above T2 and enables a particularly large temperature difference, which results in high switching reliability.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)
• Paints Or Removers (AREA)
• Laminated Bodies (AREA)

Applications Claiming Priority (2)

Publications (3)

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ID=6333092

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Cited By (5)

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Citations (5)

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• 1987
  • 1987-08-05 DE DE19873725948 patent/DE3725948A1/de not_active Withdrawn
• 1988
  • 1988-07-27 EP EP88112108A patent/EP0302374B1/fr not_active Expired - Lifetime
  • 1988-07-27 DE DE8888112108T patent/DE3881781D1/de not_active Expired - Fee Related
  • 1988-08-04 JP JP63193569A patent/JPS6462368A/ja active Pending

Patent Citations (5)

Non-Patent Citations (1)

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