EP0962815A1 - Aufzeichnungsmaterial mit verbessertem Bildton und/oder verbesserter Lagerfähigkeit nach thermischer Entwicklung - Google Patents

Aufzeichnungsmaterial mit verbessertem Bildton und/oder verbesserter Lagerfähigkeit nach thermischer Entwicklung Download PDF

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Publication number
EP0962815A1
EP0962815A1 EP99201712A EP99201712A EP0962815A1 EP 0962815 A1 EP0962815 A1 EP 0962815A1 EP 99201712 A EP99201712 A EP 99201712A EP 99201712 A EP99201712 A EP 99201712A EP 0962815 A1 EP0962815 A1 EP 0962815A1
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EP
European Patent Office
Prior art keywords
silver
recording material
palmitate
organic
silver palmitate
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EP99201712A
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English (en)
French (fr)
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EP0962815B1 (de
Inventor
Ingrid Geuens
Yvan Gilliams
Dirk Bollen
Yvan Hoogmartens
André Bellens
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Agfa Gevaert NV
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Agfa Gevaert NV
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Priority to EP19990201712 priority Critical patent/EP0962815B1/de
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/494—Silver salt compositions other than silver halide emulsions; Photothermographic systems ; Thermographic systems using noble metal compounds
    • G03C1/498—Photothermographic systems, e.g. dry silver
    • G03C1/49809—Organic silver compounds
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/494—Silver salt compositions other than silver halide emulsions; Photothermographic systems ; Thermographic systems using noble metal compounds
    • G03C1/498—Photothermographic systems, e.g. dry silver
    • G03C1/4989—Photothermographic systems, e.g. dry silver characterised by a thermal imaging step, with or without exposure to light, e.g. with a thermal head, using a laser

Definitions

  • the present invention relates to recording materials with improved shelf-life.
  • Thermal imaging or thermography is a recording process wherein images are generated by the use of thermal energy.
  • Such recording materials become photothermographic upon incorporating a photosensitive agent which after exposure to UV, visible or IR light is capable of catalyzing or participating in a thermographic process bringing about changes in colour or optical density.
  • GB-A 1,542,327 discloses a thermally developable light-sensitive sheet material, comprising a support and (a) a silver salt of an organic acid, (b) a catalyst in an amount capable of catalyzing the reaction in exposed areas of the material of components (a) and (c) after imagewise exposure and heating of the material, (c) a reducing agent for the salt (a), and (d) sulphur in an amount to reduce the colour change after processing and to reduce thermal fogging, the components (a) to (d) being contained, separately or together, in one or more layers coated on the support or being all present in the support or one or more of the components being present in the support and the remainder being in one or more layers coated thereon.
  • GB 1,542,327 includes an exhaustive list of silver salts of an organic acid including silver palmitate. Furthermore, D.S. Avose, V.V. Tsvetkov and V.D. Yagodovskii in Sci. Appl. Photo. volume 35, pages 587-594 published in 1994 by Gordon and Breach Science Publishers S.A. describe the photothermographic materials based on silver bromide and silver palmitate.
  • US 4,273,723 discloses a process for preparing a silver salt of a fatty acid with 12 to 24 carbon atoms consisting essentially of reacting an alkali metal salt of the fatty acid with a water-soluble silver salt, and wherein the reaction is effected in a reaction system consisting essentially of (I) the alkali metal salt of the fatty acid, (II) the water-soluble silver salt, (III) at least one water-soluble or partially water-soluble C 3 -C 8 alcohol and (IV) water, the volume ratio of the component (III) to the component (IV) being 1/5 to 5/1.
  • GB-A 1,378,734 discloses a process of producing a silver salt of an organic carboxylic acid conducted in the presence of a soluble mercury compound and/or a soluble lead compound.
  • EP-A 754 969 discloses a process for producing a suspension of particles containing a substantially light-insensitive silver salt of an organic carboxylic acid, comprising simultaneous metered addition of an aqueous solution or suspension of an organic carboxylic acid or its salt; and an aqueous solution of a silver salt to an aqueous liquid, wherein the metered addition of the aqueous solution or suspension of the organic carboxylic acid or its salt; and/or the aqueous solution of the silver salt is regulated by the concentration of silver ions or the concentration of anions of the silver salt in the aqueous liquid.
  • Research Disclosure number 17029 published in June 1978,gives a survey of different methods of preparing organic heavy metal salts in section II.
  • recording materials comprising a support and a thermosensitive element comprising silver palmitate with a higher crystallinity than prior art silver palmitate, an organic reducing agent therefor in thermal working relationship therewith and a binder exhibit a marked improvement in shelf-life over prior art recording materials with silver palmitate.
  • a recording material comprising a support and a thermosensitive element comprising silver palmitate, an organic reducing agent therefor in thermal working relationship therewith and a binder, characterized in that the silver palmitate is not associated with mercury and/or lead ions and when the recording material is irradiated with a copper K ⁇ 1 X-ray source the ratio of the sum of the peak heights of the X-ray diffraction lines attributable to silver palmitate at Bragg angles, 2 ⁇ , of 4.01°, 6.049°, 8.031°, 10.06°, 12.08° and 14.09° to the sum of the peak heights of the X-ray diffraction lines at Bragg angles, 2 ⁇ , of 25.60°, 35.16° and 43.40° of NIST standard 1976, rhombohedral Al 2 O 3 , determined with the same X-ray diffractometer in the same state of adjustment on a sample of the recording material and a sample of the NIST standard 1976 cut to fit a
  • a production process for a dispersion of particles of substantially light-insensitive organic silver salt including silver palmitate in a substantially solvent-free aqueous medium comprising the steps of: i) producing an aqueous dispersion of one or more organic acids including palmitic acid and an anionic surfactant; ii) substantially neutralizing the organic acids with aqueous alkali thereby forming organic acid salts including a palmitic acid salt; (iii) adding an aqueous solution of a silver salt to completely convert the organic acid salt(s) into their silver salts including silver palmitate, characterized in that the anionic surfactant is present in a molar ratio with respect to organic acid greater than 0.15 and the silver salt is added to produce organic silver salt(s) at a rate between 0.025mol/mol organic silver salt(s) • min and 2.25mol/mol organic silver salt(s) • min.
  • Particles of substantially light-insensitive organic silver salt containing silver palmitate producible according to the above-mentioned process are also provided.
  • a recording process is further provided according to the present invention comprising the steps of: (i) bringing an outermost layer of the above-mentioned recording material in proximity with a heat source; and (ii) applying heat from the heat source imagewise to the recording material while maintaining proximity to the heat source to produce an image; and (iii) removing the recording material from the heat source.
  • the heat source is a thermal head with a thin film thermal head being particularly preferred.
  • substantially light-insensitive is meant not intentionally light sensitive.
  • substantially solvent-free aqueous medium is meant that solvent, if present, is present in amounts below 10% by volume of the aqueous medium.
  • thermosensitive element comprises silver palmitate, an organic reducing agent therefor in thermal working relationship therewith and a binder.
  • the element may comprise a layer system in which the ingredients may be dispersed in different layers, with the proviso that the two ingredients are in reactive association with one another i.e. during the thermal development process the reducing agent must be present in such a way that it is able to diffuse to the silver palmitate so that reduction of silver palmitate to silver can occur.
  • thermosensitive element further comprises a photosensitive species capable upon exposure of forming a species capable of catalyzing reduction of the silver palmitate.
  • the silver palmitate in the recording material, of the present invention is characterized in that when the recording material is irradiated with a copper K ⁇ 1 X-ray source the ratio of the sum of the peak heights of the X-ray diffraction lines attributable to silver palmitate at Bragg angles, 2 ⁇ , of 4.01°, 6.049°, 8.031°, 10.06°, 12.08° and 14.09° to the sum of the peak heights of the X-ray diffraction lines at Bragg angles, 2 ⁇ , of 25.60°, 35.16° and 43.40° of NIST (National Institute of Standards, Gaithersburg, MD 20899-0001, USA) standard 1976, rhombohedral Al 2 O 3 , determined with the same X-ray diffractometer in the same state of adjustment, divided by the square root of the quantity of silver in the recording material, expressed in g per m 2 , is greater than 3.09 m/g 0.5 , which is referred to in the detailed description of the present invention as
  • the crystallinity of the silver palmitate in the recording material of the present invention is obtained by determining X-ray diffraction spectra on sheets of a particular recording material and of the NIST standard 1976 cut to fit the sample holder of the X-ray diffractometer used, subtracting the background using standard techniques, determining the peak heights (maxima) of the diffraction peaks, determining for the sample of recording material the sum of the peak heights (maxima), K material , of the XRD lines attributable to silver palmitate at Bragg angles, 2 ⁇ , of 4.01°, 6.049°, 8.031°, 10.06°, 12.08° and 14.09° , determining for the sample of NIST standard 1976 the sum of the peak heights (maxima), K 1976 , of the X-ray diffraction lines at Bragg angles, 2 ⁇ , of 25.60°, 35.16° and 43.40°, calculating the ratio of K material /K 1976 for the recording material, determining the concentration of silver C Ag
  • the concentration of silver present in the recording material can be determined by any known technique e.g. non-destructive methods such as X-ray fluorescence and destructive methods such as dissolution of the silver salt followed by standard volumetric techniques for the determination of silver, such as described in R. Belcher and A.J. Nutten, Quantitative Inorganic Analysis, 2nd Edition, Butterworths, London (1960), pages 201-219.
  • non-destructive methods such as X-ray fluorescence
  • destructive methods such as dissolution of the silver salt followed by standard volumetric techniques for the determination of silver, such as described in R. Belcher and A.J. Nutten, Quantitative Inorganic Analysis, 2nd Edition, Butterworths, London (1960), pages 201-219.
  • Organic silver salt particles containing silver palmitate may contain up to 100mol% of silver palmitate. They preferably contain at least 50mol% of silver palmitate.
  • Preferred substantially light-insensitive organic silver salts used in the present invention are silver salts of organic carboxylic acids for use in the recording materials of the present invention together with silver palmitate are silver salts of other aliphatic carboxylic acids known as fatty acids, wherein the aliphatic carbon chain has preferably at least 12 C-atoms, e.g. silver laurate, silver stearate, silver hydroxystearate, silver behenate and silver arichidate.
  • the silver palmitate of the present invention is not associated with mercury and/or lead ions. This means that mercury/and or silver ions are not intentionally added at any point during the preparation process and therefore are not intentionally associated with the silver palmitate in the recording material of the present invention.
  • a production process for a dispersion of particles of substantially light-insensitive organic silver salt including silver palmitate in a substantially solvent-free aqueous medium comprising the steps of: i) producing an aqueous dispersion of one or more organic acids including palmitic acid and an anionic surfactant; ii) substantially neutralizing the organic acids with aqueous alkali thereby forming organic acid salts including a palmitic acid salt; (iii) adding an aqueous solution of a silver salt to completely convert the organic acid salts into their silver salts including silver palmitate, characterized in that the anionic surfactant is present in a molar ratio with respect to organic acid greater than 0.15 and the silver salt is added to produce organic silver salt(s) at a rate between 0.025mol/mol organic silver salt(s) • min and 2.25mol/mol organic silver salt(s) • min.
  • the anionic surfactant is present in a molar ratio with respect to organic carboxylic acid greater than 0.25 and the silver salt is added to produce organic silver salt(s) at a rate between 0.03mol/mol organic silver salt(s) ⁇ min and 0.7mol/mol organic silver salt(s) ⁇ min, with a molar ratio of anionic surfactant with respect to organic acid greater than 0.3 and a rate of silver salt addition of between 0.04mol/mol organic silver salt(s) ⁇ min and 0.3mol/mol organic silver salt(s) ⁇ min being particularly preferred.
  • step (iii) of the production process of the present invention is carried out such that part of the solution of acid salts produced in step (ii) of the process is present in the reaction vessel prior to silver salt solution addition and part thereof is added simultaneously with the addition of the silver salt solution, with about 25 to 50% of the solution of acid salts produced in step (ii) being in the reaction vessel prior to silver salt addition being particularly preferred.
  • Preferred anionic surfactants for use in the above-mentioned process are alkali or ammonium salts of an acid selected from the group consisting of: alkylsulfonic acids, alkarylsulfonic acids, aralkylsulfonic acids, arylsulfonic acids, alkylsulfuric acids, aralkylsulfuric acids, arylsulfuric acids, alkarylsulfuric acids and organic carboxylic acids.
  • Alkali or ammonium salts of alkylarylsulfonic acids are preferred with alkali or ammonium salts of alkylbenzene sulfonic acids being particularly preferred.
  • Suitable anionic surfactants for use in the above-mentioned process are:
  • the pH used is sufficiently low to avoid the oxidation of silver ions to silver oxide or silver hydroxide for which a pH below 10 is usually required
  • the process temperature is chosen such that it is above the melting point of the organic acid(s) used, about 65°C in the case of palmitic acid, and the pocess is carried out with stirring, the stirring rate being dependent upon: the size of the stirrer relative to the reaction vessel, the type of stirrer used, avoidance of silver oxide or silver hydroxide formation due to insufficient mixing and avoidance of foaming, it usually being between 200 and 1000rpm.
  • a slight excess of an organic acid for example 2mol% of palmitic acid, is preferred.
  • the size of the substantially light-insensitive organic silver salt particles containing silver palmitate can be varied by varying the rate of silver salt addition, the concentration of anionic surfactant and the temperature, the equivalent diameter of the particles increasing with decreasing addition rate, decreasing anionic surfactant concentration and increasing temperature.
  • the dispersion of particles of substantially light-insensitive organic silver salt containing silver palmitate is subjected to ultrafiltration.
  • the ultrafiltration process removes ionic species and concentrates the dispersion of substantially light-insensitive organic silver salt containing silver palmitate by filtration through a cartridge-filter with a pore size sufficiently small to remove the salt produced upon the formation of the organic silver salt without removing the silver palmitate.
  • Cartridge-filters with 10 000 to 500 000 MW have been found to be suitable for this purpose.
  • the counterion of the anionic surfactant can be changed, if the presence of the original counterion be undesirable in the recording material.
  • the sodium ions in Surfactant nr 1 can be replaced by ammonium ions by washing with an ammonium nitrate solution during the ultrafiltration process and the sodium ion concentration reduced to below 100ppm.
  • the above-mentioned process produces substantially light-insensitive organic silver salt containing silver palmitate in which the silver palmitate has a crystallinity, as defined above, greater than 2.09 m/g 0.5 .
  • recording materials can be produced, if dispersions thereof are produced using dispersion techniques in which the particles themselves are subjected to as little damage as possible commensurate with achieving a satisfactory dispersion quality e.g.using microfluidizers, ultrasonic apparatuses, rotor stator mixers etc.
  • Suitable organic reducing agents for the reduction of organic silver salt particles containing silver palmitate are organic compounds containing at least one active hydrogen atom linked to O, N or C, such as is the case with, aromatic di- and tri-hydroxy compounds.
  • Catechol-type reducing agents i.e. reducing agents containing at least one benzene nucleus with two hydroxy groups (-OH) in ortho-position, such as catechol, 3-(3,4-dihydroxyphenyl) propionic acid, 1,2-dihydroxybenzoic acid, gallic acid and esters e.g.
  • methyl gallate, ethyl gallate, propyl gallate, tannic acid, and 3,4-dihydroxy-benzoic acid esters are preferred, with those described in EP-B 692 733 and EP-A 903 625 being particularly preferred.
  • Suitable reducing agents are sterically hindered phenols, bisphenols and sulfonamidophenols.
  • Combinations of reducing agents may also be used that on heating become reactive partners in the reduction of the substantially light-insensitive organic silver salt comprising silver palmitate.
  • combinations of sterically hindered phenols with sulfonyl hydrazide reducing agents such as disclosed in US-P 5,464,738; trityl hydrazides and formyl-phenyl-hydrazides such as disclosed in US-P 5,496,695; trityl hydrazides and formyl-phenyl-hydrazides with diverse auxiliary reducing agents such as disclosed in US-P 5,545,505, US-P 5.545.507 and US-P 5,558,983; acrylonitrile compounds as disclosed in US-P 5,545,515 and US-P 5,635,339; and 2-substituted malonodialdehyde compounds as disclosed in US-P 5,654,130.
  • thermosensitive element Film-forming binders of the thermosensitive element
  • the film-forming binder of the thermosensitive element containing organic silver salt particles containing silver palmitate may be all kinds of natural, modified natural or synthetic resins or mixtures of such resins, in which the organic silver salt particles containing silver palmitate can be dispersed homogeneously either in aqueous or solvent media: e.g. cellulose derivatives such as ethylcellulose, cellulose esters, e.g.
  • cellulose nitrate carboxymethylcellulose, starch ethers, galactomannan
  • polymers derived from ⁇ , ⁇ -ethylenically unsaturated compounds such as polyvinyl chloride, after-chlorinated polyvinyl chloride, copolymers of vinyl chloride and vinylidene chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl acetate and partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals that are made from polyvinyl alcohol as starting material in which only a part of the repeating vinyl alcohol units may have reacted with an aldehyde, preferably polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters, polystyrene and polyethylene or mixtures thereof.
  • binders or mixtures thereof may be used in conjunction with waxes or "heat solvents” also called “thermal solvents” or “thermosolvents” improving the reaction speed of the redox-reaction at elevated temperature.
  • thermosensitive element contains preferably in admixture with the organic silver salt particles containing silver palmitate and reducing agents a so-called toning agent known from thermography or photothermography.
  • Suitable toning agents are the phthalimides and phthalazinones within the scope of the general formulae described in US-P 4,082,901 and those described in US-P 3,074,809, 3,446,648 and 3,844,797.
  • Other particularly useful toning agents are the heterocyclic toner compounds of the benzoxazine dione or naphthoxazine dione type as disclosed in GB-P 1,439,478, US-P 3,951,660 and US-P 5,599,647.
  • stabilizers and antifoggants may be incorporated into the recording materials of the present invention.
  • the recording material may contain in addition to the ingredients mentioned above other additives such as free fatty acids, surface-active agents, antistatic agents, e.g. non-ionic antistatic agents including a fluorocarbon group as e.g. in F 3 C(CF 2 ) 6 CONH(CH 2 CH 2 O)-H, silicone oil, e.g. BAYSILONETM ⁇ l A (BAYER AG, GERMANY), ultraviolet light absorbing compounds, white light reflecting and/or ultraviolet radiation reflecting pigments and/or optical brightening agents.
  • antistatic agents e.g. non-ionic antistatic agents including a fluorocarbon group as e.g. in F 3 C(CF 2 ) 6 CONH(CH 2 CH 2 O)-H
  • silicone oil e.g. BAYSILONETM ⁇ l A (BAYER AG, GERMANY)
  • ultraviolet light absorbing compounds e.g. BAYER AG, GERMANY
  • the support for the thermosensitive element according to the present invention may be transparent, translucent or opaque, e.g. having a white light reflecting aspect and is preferably a thin flexible carrier e.g. polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate.
  • a thin flexible carrier e.g. polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate.
  • the support may be in sheet, ribbon or web form and subbed if need be to improve the adherence to the thereon coated thermosensitive element.
  • the support may be made of an opacified resin composition. Should a transparent base be used, the base may be colourless or coloured, e.g. having a blue colour.
  • One or more backing layers may be provided to control physical properties such as curl and static.
  • the outermost layer of the recording material may in different embodiments of the present invention be the outermost layer of the thermosensitive element, a protective layer applied to the thermosensitive element or a layer on the opposite side of the support to the thermosensitive element.
  • the thermosensitive element is provided with a protective layer to avoid local deformation of the thermosensitive element and to improve resistance against abrasion.
  • the protective layer preferably comprises a binder, which may be solvent-soluble, solvent-dispersible, water-soluble or water-dispersible.
  • a binder which may be solvent-soluble, solvent-dispersible, water-soluble or water-dispersible.
  • solvent-soluble binders polycarbonates as described in EP-A 614 769 are particularly preferred.
  • water-soluble or water-dispersible binders are preferred for the protective layer, as coating can be performed from an aqueous composition and mixing of the protective layer with the immediate underlayer can be avoided by using a solvent-soluble or solvent-dispersible binder in the immediate underlayer.
  • a protective layer according to the present invention may comprise in addition a thermomeltable particle optionally with a lubricant present on top of the protective layer as described in WO 94 /11199.
  • a thermomeltable particle optionally with a lubricant present on top of the protective layer as described in WO 94 /11199.
  • at least one solid lubricant having a melting point below 150°C and at least one liquid lubricant in a binder is present, wherein at least one of the lubricants is a phosphoric acid derivative.
  • the outermost layer according to the present invention may be crosslinked.
  • Crosslinking can be achieved by using crosslinking agents such as described in WO 95/12495 for protective layers, e.g. tetra-alkoxysilanes, polyisocyanates, zirconates, titanates, melamine resins etc., with tetraalkoxysilanes such as tetramethylorthosilicate and tetraethylorthosilicate being preferred.
  • the outermost layer of the recording material according to the present invention may comprise a matting agent.
  • Suitable matting agents are described in WO 94/11198 and include e.g. talc particles and optionally protrude from the outermost layer.
  • Solid or liquid lubricants or combinations thereof are suitable for improving the slip characteristics of the recording materials according to the present invention.
  • Preferred solid lubricants are thermomeltable particles such as those described in WO 94/11199.
  • a preferred photosensitive species capable upon exposure of forming species capable of catalyzing reduction of the silver palmitate of the present invention is silver halide.
  • the photosensitive silver halide used in the present invention may be employed in a range of 0.1 to 100 mol percent; preferably, from 0.2 to 80 mol percent; particularly preferably from 0.3 to 50 mol percent; especially preferably from 0.5 to 35 mol %; and especially from 1 to 12 mol % of substantially light-insensitive organic silver salt.
  • the silver halide may be any photosensitive silver halide such as silver bromide, silver iodide, silver chloride, silver bromoiodide, silver chlorobromoiodide, silver chlorobromide etc.
  • the silver halide may be in any form which is photosensitive including, but not limited to, cubic, orthorhombic, tabular, tetrahedral, octagonal etc. and may have epitaxial growth of crystals thereon.
  • the silver halide used in the present invention may be employed without modification. However, it may be chemically sensitized with a chemical sensitizing agent such as a compound containing sulphur, selenium, tellurium etc., or a compound containing gold, platinum, palladium, iron, ruthenium, rhodium or iridium etc., a reducing agent such as a tin halide etc., or a combination thereof.
  • a chemical sensitizing agent such as a compound containing sulphur, selenium, tellurium etc., or a compound containing gold, platinum, palladium, iron, ruthenium, rhodium or iridium etc.
  • a reducing agent such as a tin halide etc.
  • thermosensitive element may contain an infra-red sensitizer, an ultra-violet light sensitizer or a visible light sensitizer.
  • Suitable sensitizers include cyanine, merocyanine, styryl, hemicyanine, oxonol, hemioxonol and xanthene dyes.
  • the thermosensitive element further includes a supersensitizer.
  • the recording materials used in the present invention may also contain antihalation or acutance dyes which absorb light which has passed through the photosensitive thermally developable photographic material, thereby preventing its reflection.
  • Such dyes may be incorporated into the photosensitive thermally developable photographic material or in any other layer of the photographic material of the present invention.
  • any layer of the recording material of the present invention may proceed by any coating technique e.g. such as described in Modern Coating and Drying Technology, edited by Edward D. Cohen and Edgar B. Gutoff, (1992) VCH Publishers Inc. 220 East 23rd Street, Suite 909 New York, NY 10010, U.S.A.
  • Thermographic imaging is carried out by the image-wise application of heat either in analogue fashion by direct exposure through an image of by reflection from an image, or in digital fashion pixel by pixel either by using an infra-red heat source, for example with a Nd-YAG laser or other infra-red laser, with a thermographic material preferably containing an infra-red absorbing compound, or by direct thermal imaging with a thermal head.
  • an infra-red heat source for example with a Nd-YAG laser or other infra-red laser
  • a thermographic material preferably containing an infra-red absorbing compound
  • thermal printing image signals are converted into electric pulses and then through a driver circuit selectively transferred to a thermal printhead.
  • the thermal printhead consists of microscopic heat resistor elements, which convert the electrical energy into heat via Joule effect.
  • Such thermal printing heads may be used in contact or close proximity with the recording material.
  • the operating temperature of common thermal printheads is in the range of 300 to 400°C and the heating time per picture element (pixel) may be less than 1.0ms, the pressure contact of the thermal printhead with the recording material being e.g. 200-500g/cm 2 to ensure a good transfer of heat.
  • the image-wise heating of the recording material with the thermal printing heads may proceed through a contacting but removable resin sheet or web wherefrom during the heating no transfer of recording material can take place.
  • Activation of the heating elements can be power-modulated or pulse-length modulated at constant power.
  • the image-wise heating can be carried out such that heating elements not required to produce an image pixel generate an amount of heat (H e ) in accordance with the following formula: 0.5 H D ⁇ H e ⁇ H D wherein H D represents the minimum amount of heat required to cause visible image formation in the recording material.
  • EP-A 654 355 discloses a method for making an image by image-wise heating by means of a thermal head having energizable heating elements, wherein the activation of the heating elements is executed duty cycled pulsewise.
  • EP-A 622 217 discloses a method for making an image using a direct thermal imaging element producing improvements in continuous tone reproduction.
  • Image-wise heating of the recording material can also be carried out using an electrically resistive ribbon incorporated into the material.
  • Image- or pattern-wise heating of the recording material may also proceed by means of pixel-wise modulated ultra-sound.
  • Photothermographic recording materials may be exposed with radiation of wavelength between an X-ray wavelength and a 5 microns wavelength with the image either being obtained by pixel-wise exposure with a finely focused light source, a UV, visible or IR wavelength laser or a light emitting diode or by direct exposure to the object itself or an image therefrom with appropriate illumination.
  • any sort of heat source can be used that enables the recording materials to be uniformly heated to the development temperature in a time acceptable for the application concerned.
  • Thermographic and photothermographic imaging can be used for the production of transparencies and reflection type prints.
  • Application of the present invention is envisaged in the fields of both graphics images requiring high contrast images with a very steep dependence of print density upon applied dot energy and continuous tone images requiring a weaker dependence of print density upon applied dot energy, such as required in the medical diagnostic field.
  • graphics images requiring high contrast images with a very steep dependence of print density upon applied dot energy
  • continuous tone images requiring a weaker dependence of print density upon applied dot energy, such as required in the medical diagnostic field.
  • black-imaged transparencies are widely used in inspection techniques operating with a light box.
  • A was first prepared by adding 0.15 moles of solid sodium hydroxide to a dispersion of 0.1575 moles and 0.176 moles of palmitic acid respectively in 1L of deionized water at 68°C thereby producing a solution of sodium palmitate with a pH of ca. 9.
  • Solution B 250mL of 0.6M aqueous silver nitrate acidified with 0.4g of 65% nitric acid at a temperature of 58°C, was then added with vigorous stirring to solution A in 15s while maintaining a temperature of 68°C. After 1 minute the resulting suspension of silver palmitate was cooled to room temperature and had a pH of ca. 5 and a UAg of ca. 350mV. The silver palmitate was filtered off under reduced pressure, washed twice each time with about 5L of deionized water and dried in a forced air drying cupboard at 40°C.
  • the tone modifier dispersion was prepared by first dissolving 11g of K7598 in 69g of deionized water by first adding the gelatin, then allowing the gelatin to swell for 30 minutes and finally heating to 50°C. 20 g of T01 was added with ULTRA-TURRAXTM stirring to this gelatin solution at 50°C, and the stirring continued for a further 5 minutes. Finally the resulting dispersion was pumped through a DYNOMILLTM for 2 hours to produce the final tone modifier dispersion containing: 20% of T01 and 8.8% of gelatin.
  • thermosensitive element thermosensitive element
  • thermosensitive emulsion was produced as follows: 2.341g of K7598 was allowed to swell for 30 minutes with deionized water (for quantity used in the preparation of the thermographic emulsion for the particular recording material see table 2) and the resulting gel heated to 36°C, then with stirring the following ingredients were added: 5.699g of the tone modifier dispersion at 36°C, then 8.120g of LATEX 01 followed by 5 minutes stirring, the corresponding silver palmitate dispersion (for quantity and silver palmitate concentration therein for the thermosensitive emulsion for the particular recording material see table 2) followed by 5 minutes stirring, 12.35g of a 10.95% ethanol solution of R01 at 45°C and finally 2.880g of a 3.7% aqueous solution of formaldehyde.
  • thermosensitive dispersions were doctor blade-coated onto a 175 ⁇ m subbed PET support and dried for 10 minutes at 50°C thereby producing the thermosensitive elements of COMPARATIVE EXAMPLES 1 & 2.
  • the printer was equipped with a thin film thermal head with a resolution of 300 dpi and was operated with a line time of 19ms (the line time being the time needed for printing one line). During this line time the printhead received constant power.
  • the average printing power being the total amount of electrical input energy during one line time divided by the line time and by the surface area of the heat-generating resistors, was 1.6 mJ/dot and was sufficient to obtain maximum optical density in each of the thermographic materials of COMPARATIVE EXAMPLES 1 & 2.
  • the printhead was separated from the imaging layer by a thin intermediate material contacted with a slipping layer of a separable 5 ⁇ m thick polyethylene terephthalate ribbon coated successively with a subbing layer, heat-resistant layer and the slipping layer (anti-friction layer) giving a ribbon with a total thickness of 6 ⁇ m.
  • the maximum densities, D max , and minimum densities, D min , of the prints given in table 3 were measured through a visible filter with a MACBETHTM TR924 densitometer in the grey scale steps corresponding to data levels of 64 and 0 respectively and are given in table 3 for COMPARATIVE EXAMPLES 1 & 2.
  • a sodium palmitate solution was prepared by dissolving with stirring 24.5 g of sodium palmitate in a mixture of 80 mL of 2-propanol and 288 mL of deionized water at 70°C to give a 6.53% by weight solution.
  • the silver palmitate synthesis was carried out at a constant UAg of 400mV as follows: to a stirred solution of 30g of K17881 in 1000mL of distilled water at 71°C in a double walled reactor, several drops of a 2.94M aqueous solution of silver nitrate were added to adjust the UAg at the start of the reaction to 400mV and then 340g of the above-mentioned sodium palmitate solution at a temperature of 75°C was metered into the reactor at a rate of 48mL/min and simultaneously a 3.792% by weight aqueous solution of silver nitrate was metered into the reactor, its addition rate being controlled by the quantity of the silver nitrate solution necessary to maintain a UAg of 400 ⁇ 5mV in the dispersing medium in the reactor.
  • Both the sodium palmitate and silver nitrate solutions were added to the dispersing medium via small diameter tubes positioned just under the surface of the dispersing medium. By the end of the addition step 0.080moles of sodium behenate and 0.094 moles of silver nitrate had been added. The mixture was then stirred for a further 30 minutes. The resulting silver palmitate dispersion contained 1.63% by weight of silver behenate and 1.69% by weight of K17881.
  • EP-A 754 969 produces silver palmitate with a crystallinity, as determined according to the present invention, below 3.09 m/g 0.5 and hence outside the disclosure of the present invention.
  • type III silver palmitate was carried out in the dark in a thermostatted stainless steel vessel with pH, pAg and temperature being continually monitored.
  • the reagents were brought to the same temperature as the vessel prior to addition and were added at a known rate by a pumping system controlled by a computer with appropriate software.
  • Palmitic acid was dissolved in ethanol at 65°C. 0.255N aqueous sodium hydroxide was added until the equivalence point was attained to obtain the sodium salt followed by a 0.401M aqueous solution of silver nitrate to complete conversion to form silver palmitate. The silver palmitate was then filtered off under reduced pressure, washed twice with deionized water and dried.
  • 75g of dried type III silver palmitate was dispersed in 75g of a 10% aqueous solution of Surfactant Nr 1 by first producing a coarse suspension using an ULTRATURRAXTM and then dispersing the resulting coarse suspension in a MICROFLUIDICSTM M-110Y high pressure microfluidizer at a jet pressure of at 350 bar to produce the final dispersion with 20.173% silver palmitate.
  • thermosensitive element thermosensitive element
  • thermosensitive elements of the recording materials of INVENTION EXAMPLES 1 was produced as described for the thermosensitive element of the recording material of COMPARATIVE EXAMPLES 1 & 2 except that the quantity of deionized water, the silver palmitate type, concentration and quantity of dispersion used were as given in table 5 below.
  • Aqueous dispersions of the silver palmitate types IV & V were produced as follows:
  • thermosensitive element thermosensitive element
  • thermosensitive elements of the recording materials of INVENTION EXAMPLES 2 & 3 were produced as described for the thermosensitive element of the recording material of COMPARATIVE EXAMPLES 1 & 2 except that the quantity of deionized water used, the silver palmitate type, concentration and quantity of dispersion used were as given in table 9 below.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
EP19990201712 1998-06-06 1999-05-25 Aufzeichnungsmaterial mit verbessertem Bildton und/oder verbesserter Lagerfähigkeit nach thermischer Entwicklung Expired - Lifetime EP0962815B1 (de)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1094362A1 (de) * 1999-10-20 2001-04-25 Fuji Photo Film Co., Ltd. Verfahren zur Herstellung von Silbersalzen organischer Säure und diese verwendendes photothermographisches Material
WO2001059520A1 (en) * 2000-02-10 2001-08-16 Eastman Kodak Company Silver carboxylate nanoparticles with polyacrylamide surface modifiers
US6355408B1 (en) 2000-05-04 2002-03-12 Eastman Kodak Company Core-shell silver salts and imaging compositions, materials and methods using same
US6472131B1 (en) 2000-05-04 2002-10-29 Eastman Kodak Company Asymmetric silver salt dimers and imaging compositions, materials and methods using same
US6803177B2 (en) 2002-07-30 2004-10-12 Eastman Kodak Company Silver compounds and compositions, thermally developable materials containing same, and methods of preparation

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0754969A2 (de) * 1995-07-18 1997-01-22 Agfa-Gevaert N.V. Verfahren zur Herstellung einer wässrigen Suspension von Teilchen, die ein im wesentlichen lichtunempfindliches Silbersalz einer organischen Carbonsäure enthalten, für die Herstellung (photo)thermographischen Materialien
EP0848286A1 (de) * 1996-12-10 1998-06-17 Agfa-Gevaert N.V. Thermographisches Aufzeichnungsmaterial mit verbesserten Bildton und/oder verbesserter Lagerfähigkeit nach thermischer Entwicklung

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0754969A2 (de) * 1995-07-18 1997-01-22 Agfa-Gevaert N.V. Verfahren zur Herstellung einer wässrigen Suspension von Teilchen, die ein im wesentlichen lichtunempfindliches Silbersalz einer organischen Carbonsäure enthalten, für die Herstellung (photo)thermographischen Materialien
EP0848286A1 (de) * 1996-12-10 1998-06-17 Agfa-Gevaert N.V. Thermographisches Aufzeichnungsmaterial mit verbesserten Bildton und/oder verbesserter Lagerfähigkeit nach thermischer Entwicklung

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1094362A1 (de) * 1999-10-20 2001-04-25 Fuji Photo Film Co., Ltd. Verfahren zur Herstellung von Silbersalzen organischer Säure und diese verwendendes photothermographisches Material
US6630293B1 (en) 1999-10-20 2003-10-07 Fuji Photo Film Co., Ltd. Method for producing silver salt of organic acid and photothermographic material utilizing the same
WO2001059520A1 (en) * 2000-02-10 2001-08-16 Eastman Kodak Company Silver carboxylate nanoparticles with polyacrylamide surface modifiers
US6355408B1 (en) 2000-05-04 2002-03-12 Eastman Kodak Company Core-shell silver salts and imaging compositions, materials and methods using same
US6465167B2 (en) 2000-05-04 2002-10-15 Eastman Kodak Company Core-shell silver salts and imaging compositions, materials and methods using same
US6472131B1 (en) 2000-05-04 2002-10-29 Eastman Kodak Company Asymmetric silver salt dimers and imaging compositions, materials and methods using same
US6566045B1 (en) 2000-05-04 2003-05-20 Eastman Kodak Company Asymmetric silver salt dimers and imaging compositions, materials and methods using same
US6803177B2 (en) 2002-07-30 2004-10-12 Eastman Kodak Company Silver compounds and compositions, thermally developable materials containing same, and methods of preparation
US7060426B2 (en) 2002-07-30 2006-06-13 Eastman Kodak Company Silver compounds and compositions, thermally developable materials containing same, and methods of preparation

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