Classifications

• • 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
• • 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
  • G03C1/49836—Additives
  • G03C1/49845—Active additives, e.g. toners, stabilisers, sensitisers
• • 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
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/34—Fog-inhibitors; Stabilisers; Agents inhibiting latent image regression

Definitions

• the present invention concerns stabilizers for use in substantially light-insensitive thermographic recording materials.
• Thermography is an image-forming process including a heating step and hence includes photothermography in which the image-forming process includes image-wise exposure and direct thermal processes in which the image-forming process includes an image-wise heating step.
• direct thermal printing a visible image pattern is produced by image-wise heating of a recording material.
• US 4,451,561 further discloses the presence of an additional compound of following formula [II]: wherein R 3 represents a substituted or unsubstituted alkyl, aryl or heterocyclic radical; R 4 and R 5 each represent a hydroxy or a substituted or unsubstituted alkyl, aryl or heterocyclic radical; Z represents a hydroxy or an amino radical; and m is an integer of 1 or 2.
• R 3 represents a substituted or unsubstituted alkyl, aryl or heterocyclic radical
• R 4 and R 5 each represent a hydroxy or a substituted or unsubstituted alkyl, aryl or heterocyclic radical
• Z represents a hydroxy or an amino radical
• m is an integer of 1 or 2.
• US 4,543,309 discloses a heat-developable image-pattern recording material of enhanced developability and stability having on a support a heat-developable image-pattern recording layer containing (a) a silver salt of a benzotriazole, (b) a reducing agent, (c) a binder, (d) at least one compound having the following formula: wherein R 1 represents a hydrogen, an amino radical, or a substituted or unsubstituted alkyl, alkenyl or aryl radical; R 2 represents a hydrogen, an amino, alkyl, alkenyl or aryl radical; and further contains a compound of the formula: wherein R 3 represents a substituted or unsubstituted alkyl, aryl or heterocyclic radical; R 4 and R 5 each represent a hydroxy or a substituted or unsubstituted alkyl, aryl or heterocyclic radical; Z represents a hydroxy or an amino radical; and m is an integer of 1 or 2. Specifically the following
• US 5,374,514 discloses a photothermographic material comprising photographic silver halide, a reducible silver source, a reducing agent for silver ion, and a binder, and, as an antifoggant and/or image stabilizer, a compound of the formula: wherein: R is a member selected from the group consisting of a hydrogen atom, an alkyl group, an aryl group and a heterocyclic group.
• JP 09-295456 discloses a method of obtaining an image which is long in shelf life and high in density, wherein at least one side of an organic silver salt or developer of organic silver salt is contained in a heat response property micro-capsule, and at least one kind in a group of compounds of a specific formula as a fog inhibitor is contained in a recording layer, the group of compounds including 1-thia-3,4-diazole-tribromomethylsulfone.
• EP-A 0 713 133 discloses a thermal imaging system consisting of (i) a donor element comprising on a support a donor layer containing a binder and a thermotransferable reducing agent capable of reducing a silver source to metallic silver and (ii) a receiving element comprising on a support a receiving layer comprising a silver source, capable of being reduced by means of heat in the presence of a reducing agent, a binder and a stabiliser selected from the group consisting of benzotriazoles, heterocyclic mercaptanes, sulphinic acids, 1,3,4-triazo-indinolines, 1,3-dinitroaryl compounds, 1,2,3-triazoles, phthalic acids and phthalic acid derivatives.
• EP-A 0 901 040 which corresponds to US 6,348,308, discloses a substantially light-insensitive monosheet recording material comprising a support and a thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder, characterized in that said thermosensitive element further contains an unsaturated carbocyclic or heterocyclic stabilizer compound substituted with a -SA group where A is hydrogen, a counterion to compensate the negative charge of the thiolate group or a group forming a symmetrical or an asymmetrical disulfide and said recording material is capable of producing prints with a numerical gradation value defined as the quotient of the fraction (2.5 - 0.1)/(E 2.5 - E 0.1 ) greater than 2.3, where E 2.5 is the energy in Joule applied in a dot area of 87 ⁇ m x 87 ⁇ m of the imaging layer that produces an optical density value of 2.5, and E 0.1 is the energy in Joul
• WO 94/16361 discloses a multilayer heat-sensitive material which comprises: a color-forming layer comprising: a color-forming amount of finely divided, solid colorless noble metal or iron salt of an organic acid distributed in a carrier composition; a color-developing amount of a cyclic or aromatic organic reducing agent, which at thermal copy and printing temperatures is capable of a color-forming reaction with the noble metal or iron salt; and an image-toning agent; characterized in that (a) the carrier composition comprises a substantially water-soluble polymeric carrier and a dispersing agent for the noble metal or iron salt and (b) the material comprises a protective overcoating layer for the color-forming layer.
• WO 94/16361 discloses that suitable antifoggants are well-known photographic anti-foggants such as mercaptobenzotriazole, chromate, oxalate, citrate, carbonate, benzotriazole (BZT), 5-methylbenzotriazole, 5,6-dimethylbenzotriazole, 5-bromobenzotriazole, 5-chlorobenzotriazole, 5-nitro-benzotriazole, 4-nitro-6-chlorobenzotriazole, 5-nitro-6-chlorobenzotriazole, 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, benzimidazole, 2-methylbenzimidazole, 5-nitrobenzimidazole, 1-phenyl-5-mercaptotetrazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptothiazoline, 2-mercapto-4-methyl-6,6'-dimethylpyr
• GB-A 1,501,005 discloses a sensitive photothermographic material which comprises a support coated on one side with a composition containing (a) a photographic silver halide, (b) an image-forming combination comprising (i) a silver salt of a heterocyclic thione of the formula wherein R represents atoms which complete an unsubstituted or substituted heterocyclic ring and Z is an alkylene group having from 1 to 30 carbon atoms and (ii) an organic reducing agent therefor, and (c) a toner which is a mercaptoheterocyclic compound which gives by the test procedure specified herein, a ⁇ D value of from zero to 0.21, the components of the composition being disposed in one or more layers.
• thermographic recording materials Differences between substantially light-insensitive thermographic recording materials and photothermographic recording materials
• thermographic materials in which image formation is based on the reduction of organic silver salts is significantly different from that of photothermographic recording materials, despite the fact that in both cases the image results from the reduction of organic silver salts.
• this a superficial similarity masking the fact that the realization of the species which catalyze this reduction is completely different, being image-wise exposure of photosensitive silver halide-containing photo-addressable thermally developable elements in the case of photothermographic recording materials and image-wise heating of thermosensitive elements which do not contain photosensitive silver halide in the case of thermographic recording materials.
• Substantially light-insensitive thermographic recording materials contain the imaging-forming components after image formation and unwanted image-forming in prints must be hindered during storage and upon exposure to light on light-boxes e.g. during examination by radiologists.
• prior art stabilizers can substantially reduce after image formation and unwanted image-forming during storage and upon exposure to light, but retard the image-forming process thereby reducing the maximum achievable image density and the stabilizer and/or the products of its reaction with other ingredients diffuse to the surface of the substantially light-insensitive thermographic recording material both during and after the image-forming process. There is therefore a need for compounds which provide stabilizing properties, but without the drawback of retarding the image-forming process.
• thermographic recording materials with a higher Dmax for a given coverage per unit area of substantially light-insensitive organic silver salt.
• thermographic recording materials It is therefore a further aspect of the present invention to provide compounds which endow substantially light-insensitive thermographic recording materials with good archivability.
• thermographic recording materials with good photostability.
• thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith, a binder and at least one five-membered heterocyclic ring compound selected from the group consisting of optionally substituted, optionally annelated 1-thia-2,3-diazole compounds; optionally substituted, optionally annelated 1-thia-2,5-diazole compounds; optionally substituted 1-thia-2,4-diazole compounds; optionally substituted 1-thia-3,4-diazole compounds; optionally substituted thiatriazole compounds; optionally substituted, optionally annelated 1-seleno-2,3-diazole compounds; optionally substituted, optionally annelated 1-seleno-2,5-diazole compounds; optionally substituted 1-seleno-2,4-diazole compounds;
• alkyl means all variants possible for each number of carbon atoms in the alkyl group i.e. for three carbon atoms: n-propyl and isopropyl; for four carbon atoms: n-butyl, isobutyl and tertiary-butyl; for five carbon atoms: n-pentyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl and 2-methyl-butyl etc.
• the L*, a* and b* CIELAB-values are defined in ASTM Norm E179-90 in a R(45/0) geometry with evaluation according to ASTM Norm E308-90.
• thermographic recording material as used in disclosing the present invention includes both substantially light-insensitive thermographic recording materials and photothermographic recording materials.
• Substantially light-insensitive means not intentionally light sensitive.
• a mercapto as used in disclosing the presence invention is a - SH group or an ionized -SH group e.g. as an ammonium or alkali metal ion salt.
• Annelated as used in disclosing the present invention means that two adjacent atoms in the five-membered heterocyclic ring compound, according to the present invention, and the bond between these two adjacent atoms is included in a further ring system.
• substantially water-free condition means heating at a temperature of 80 to 250°C.
• substantially water-free condition means that the reaction system is approximately in equilibrium with water in the air, and water for inducing or promoting the reaction is not particularly or positively supplied from the exterior to the element. Such a condition is described in T.H. James, "The Theory of the Photographic Process", Fourth Edition, Macmillan 1977, page 374.
• thermographic recording material is a substantially light-insensitive thermographic recording material.
• thermosensitive element further contains photosensitive silver halide and thereby becomes a photothermographic recording material.
• thermosensitive element as used herein is that element which contains all the ingredients which contribute to image formation.
• the thermosensitive element contains one or more substantially light-insensitive organic silver salts, one or more reducing agents therefor in thermal working relationship therewith and a binder.
• the element may comprise a layer system in which the above-mentioned ingredients may be dispersed in different layers, with the proviso that the substantially light-insensitive organic silver salts are in reactive association with the reducing agents 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 particles of substantially light-insensitive organic silver salt so that reduction to silver can occur.
• Such materials include the possibility of one or more substantially light-insensitive organic silver salts and/or one of more organic reducing agents therefor being encapsulated in heat-responsive microcapsules, such as disclosed in EP-A 0 736 799 herein incorporated by reference.
• thermosensitive element When photosensitive silver halide is present in the thermosensitive element, the thermosensitive element becomes a photo-addressable thermally developable element.
• thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith, a binder and at least one five-membered heterocyclic ring compound selected from the group consisting of optionally substituted, optionally annelated 1-thia-2,3-diazole compounds; optionally substituted, optionally annelated 1-thia-2,5-diazole compounds; optionally substituted 1-thia-2,4-diazole compounds; optionally substituted 1-thia-3,4-diazole compounds; optionally substituted thiatriazole compounds; optionally substituted, optionally annelated 1-seleno-2,3-diazole compounds; optionally substituted, optionally annelated 1-seleno-2,5-diazole compounds; optionally substituted 1-seleno-2,4-diazole compounds;
• the optional substitution of the five-membered heterocyclic ring compound is a halogen atom or an optionally substituted alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic, heteroaromatic, alkoxy, thio-alkoxy, aryloxy, amino, amido, carboxy, carboxy ester, acyl, carbonato, carbonato-ester or a SO 2 R group wherein R is an alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic or heteroaromatic group; or two adjacent groups can together constitute the atoms necessary to form an optionally substituted heterocyclic, alicyclic, aromatic or heteroaromatic ring or ring system.
• Optional substitution of the substituents on the five-membered heterocyclic ring compound includes substitution with one or more of an alkyl, an aryl, an alkoxy, a thioalkoxy, an aryloxy, a hydroxy, a five-membered ring system and a -S-five-membered heterocyclic ring system group.
• the optional annelation of the five-membered heterocyclic ring compound is with an aromatic, alicylic or heterocyclic ring system.
• aromatic ring systems are a benzene, naphthalene, anthracene, phenanthrene ring system.
• suitable alicyclic ring systems are a cyclohexane, cyclohexene and a cyclohexadiene ring system.
• heterocyclic ring systems examples include a pyridine, a quinoline, an isoquinoline, a tetrahydropyridine and a dihydropyridine ring system and a cyclohexane or benzene ring annelated with a five membered heterocyclic ring.
• the at least one optionally annelated five-membered heterocyclic ring compound is annelated with a benzene or a naphthalene ring.
• thermographic recording materials of the present invention can be prepared using classical organic preparative techniques known to one skilled in the art.
• the at least one five-membered heterocyclic ring compound is selected from the group consisting of optionally substituted, optionally annelated 1-thia-2,3-diazole compounds; optionally substituted, optionally annelated 1-thia-2,5-diazole compounds; optionally substituted 1-thia-2,4-diazole compounds; and optionally substituted 1-thia-3,4-diazole compounds.
• the at least one five-membered heterocyclic ring compound is represented by formula (I): where R 1 and R 2 are independently a hydrogen or a halogen atom or an optionally substituted alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic, heteroaromatic, alkoxy, thio-alkoxy, aryloxy, amino, amido, carboxy, carboxy ester, acyl, carbonato, carbonato-ester or a SO 2 R 3 group wherein R 3 is an alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic or heteroaromatic group; or R 1 and R 2 together constitute the atoms necessary to form an optionally substituted heterocyclic, alicyclic, aromatic or heteroaromatic ring or
• the at least one five-membered heterocyclic ring compound is represented by formula (II): where R 4 and R 5 are independently a hydrogen or a halogen atom or an optionally substituted alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic, heteroaromatic, alkoxy, thio-alkoxy, aryloxy, amino, amido, carboxy, carboxy ester, acyl, carbonato, carbonato-ester or a SO 2 R 6 group wherein R 6 is an alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic or heteroaromatic group; or R 4 and R 5 together constitute the atoms necessary to form an optionally substituted heterocyclic, alicyclic, aromatic or heteroaromatic ring
• the at least one five-membered heterocyclic ring compound is represented by formula (III): where R 7 and R 8 are independently a hydrogen or a halogen atom or an optionally substituted alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic, heteroaromatic, alkoxy, thio-alkoxy, aryloxy, amino, amido, carboxy, carboxy ester, acyl, carbonato, carbonato-ester or a SO 2 R 9 group wherein R 9 is an alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic or heteroaromatic group.
• the at least one five-membered heterocyclic ring compound is represented by formula (IV): where R 10 and R 11 are independently a hydrogen or a halogen atom or an optionally substituted alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic, heteroaromatic, alkoxy, thio-alkoxy, aryloxy, amino, amido, carboxy, carboxy ester, acyl, carbonato, carbonato-ester or a SO 2 R 12 group wherein R 12 is an alkyl, alkenyl, alkynyl, alicyclic, aryl, aralkyl, alkaryl, heterocyclic or heteroaromatic group.
• the at least one five-membered heterocyclic ring compound is selected from the group consisting of
• the organic silver salts are not double organic salts containing a silver cation associated with a second cation e.g. magnesium or iron ions.
• At least one of the organic silver salts is a substantially light-insensitive silver salt of an organic carboxylic acid.
• At least one of the organic silver salts is a substantially light-insensitive silver salt of an aliphatic carboxylic acids known as a fatty acid, wherein the aliphatic carbon chain has preferably at least 12 C-atoms, e.g. silver laurate, silver palmitate, silver stearate, silver hydroxystearate, silver oleate and silver behenate, which silver salts are also called "silver soaps".
• Other silver salts of an organic carboxylic acid as described in GB-P 1,439,478, e.g. silver benzoate may likewise be used to produce a thermally developable silver image.
• Combinations of different silver salt of an organic carboxylic acids may also be used in the present invention, as disclosed in EP-A 964 300.
• Organic silver salts may be dispersed by standard dispersion techniques. Ball mills, bead mills, microfluidizers, ultrasonic apparatuses, rotor stator mixers etc. have been found to be useful in this regard. Mixtures of organic silver salt dispersions produced by different techniques may also be used to obtain the desired thermographic properties e.g. of coarser and more finely ground dispersions of organic silver salts.
• the reducing agent is an organic compound 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.
• 1,2-dihydroxybenzene derivatives 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-A 0 692 733 and EP-A 0 903 625 being particularly preferred.
• Combinations of reducing agents may also be used that on heating become reactive partners in the reduction of the one or more substantially light-insensitive organic silver salt.
• combinations of sterically hindered phenols with sulfonyl hydrazide reducing agents such as disclosed in US 5,464,738; trityl hydrazides and formyl-phenyl-hydrazides such as disclosed in US 5,496,695; trityl hydrazides and formyl-phenyl-hydrazides with diverse auxiliary reducing agents as disclosed in US 5,545,505, US 5,545,507 and US 5,558,983; acrylonitrile compounds as disclosed in US 5,545,515 and US 5,635,339; and 2-substituted malonodialdehyde compounds as disclosed in US 5,654,130.
• thermosensitive element Binder of the thermosensitive element
• the film-forming binder of the thermosensitive element may be all kinds of natural, modified natural or synthetic resins or mixtures of such resins, in which the at least one organic silver salt can be dispersed homogeneously either in aqueous or solvent media: e.g.
• cellulose derivatives 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, polyacrylates, polymethacrylates, polystyrene and polyethylene or mixtures thereof.
• aldehyde preferably polyvinyl butyral
• copolymers of acrylonitrile and acrylamide copolymers of acrylonitrile and
• thermographic recording materials are: polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethyleneglycol, proteinaceous binders, polysaccharides and water-soluble cellulose derivatives.
• a preferred water-soluble binder for use in the thermographic recording materials of the present invention is gelatine.
• the binder to organic silver salt weight ratio is preferably in the range of 0.2 to 7, and the thickness of the thermosensitive element is preferably in the range of 5 to 50 ⁇ m. Binders are preferred which do not contain additives, such as certain antioxidants (e.g. 2,6-di-tert-butyl-4-methylphenol), or impurities which adversely affect the thermographic properties of the thermographic recording materials in which they are used.
• additives such as certain antioxidants (e.g. 2,6-di-tert-butyl-4-methylphenol), or impurities which adversely affect the thermographic properties of the thermographic recording materials in which they are used.
• thermosensitive element contains a toning agent, which enables a neutral black image tone to be obtained in the higher densities and neutral grey in the lower densities.
• thermosensitive element further contains a toning agent selected from the group consisting of phthalimides, phthalazinones, benzoxazine diones and naphthoxazine diones e.g.
• phthalimides and phthalazinones within the scope of the general formulae described in US 4,082,901; the toning agents described in US 3,074,809, 3,446,648 and 3,844,797; and the heterocyclic toner compounds of the benzoxazine dione or naphthoxazine dione type as disclosed in GB 1,439,478, US 3,951,660 and US 5,599,647, herein incorporated by reference.
• the substantially light-insensitive thermographic material contains a thermosensitive element, the thermosensitive element containing one or more toning agents selected from the group consisting of phthalazinone, benzo[e][1,3]oxazine-2,4-dione, 7-methyl-benzo[e][1,3]oxazine-2,4-dione, 7-methoxy-benzo[e][1,3]oxazine-2,4-dione and 7-(ethylcarbonato)-benzo[e][1,3]oxazine-2,4-dione.
• phthalazinone benzo[e][1,3]oxazine-2,4-dione
• 7-methyl-benzo[e][1,3]oxazine-2,4-dione 7-methoxy-benzo[e][1,3]oxazine-2,4-dione
• thermographic recording material further contains an auxiliary antifoggant to obtain improved shelf-life and reduced fogging.
• thermographic recording material further contains an antifoggant selected from the group consisting of aromatic polycarboxylic acid such as ortho-phthalic acid, 3-nitro-phthalic acid, tetrachlorophthalic acid, mellitic acid, pyromellitic acid and trimellitic acid and anhydrides thereof.
• aromatic polycarboxylic acid such as ortho-phthalic acid, 3-nitro-phthalic acid, tetrachlorophthalic acid, mellitic acid, pyromellitic acid and trimellitic acid and anhydrides thereof.
• the thermosensitive element further contains at least one polycarboxylic acid and/or anhydride thereof in a molar percentage of at least 15 with respect to all the organic silver salt(s) present and in thermal working relationship therewith.
• the polycarboxylic acid may be aliphatic (saturated as well as unsaturated aliphatic and also cycloaliphatic) or an aromatic polycarboxylic acid, may be substituted and may be used in anhydride form or partially esterified on the condition that at least two free carboxylic acids remain or are available in the heat recording step.
• the substantially light-insensitive thermographic material used in the present invention may contain one or more surfactants, which may be anionic, non-ionic or cationic surfactants and/or one or more dispersants.
• Suitable dispersants are natural polymeric substances, synthetic polymeric substances and finely divided powders, e.g. finely divided non-metallic inorganic powders such as silica.
• the support is transparent or translucent. It is preferably a thin flexible carrier made transparent resin film, e.g. made of a cellulose ester, e.g. cellulose triacetate, polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate.
• the support may be in sheet, ribbon or web form and subbed if needs be to improve the adherence to the thereon coated thermosensitive element.
• the support may be dyed or pigmented to provide a transparent coloured background for the image.
• thermosensitive element is provided with a protective layer.
• a protective layer In general this protects the thermosensitive element from atmospheric humidity and from surface damage by scratching etc. and prevents direct contact of printheads or heat sources with the recording layers.
• Protective layers for thermosensitive elements which come into contact with and have to be transported past a heat source under pressure, have to exhibit resistance to local deformation and good slipping characteristics during transport past the heat source during heating.
• a slipping layer being the outermost layer, may comprise a dissolved lubricating material and/or particulate material, e.g. talc particles, optionally protruding from the outermost layer. Examples of suitable lubricating materials are a surface active agent, a liquid lubricant, a solid lubricant or mixtures thereof, with or without a polymeric binder.
• the photosensitive silver halide used the present invention 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.
• the grain size of the silver halide particles can be determined by the Moeller Teller method in the sample containing silver halide particles is sedimented upon a filter paper, which is submerged in electrolyte together with a negative platinum needle-shaped electrode and a reference electrode.
• the silver halide particles on the filter paper are slowly scanned individually with the needle-shaped electrode, whereupon the silver halide grains are individually electrochemically reduced at the cathode.
• This electrochemical reduction is accompanied by a current pulse, which is registered as a function of time and integrated to give the charge transfer Q for the electrochemical reduction of the silver halide particle, which is proportional to its volume. From their volume the equivalent circular grain diameter of each grain can be determined and therefrom the average particle size and size distribution.
• 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 silver salt of an organic carboxylic acid.
• So-called in-situ silver halide can be prepared by conversion of a substantially light-insensitive silver salt of an organic carboxylic acid with a non-fluoro halide ion source such as described in US 3,457,075, WO 97/48104 and WO 97/48105 herein incorporated by reference.
• the photo-addressable thermally developable element of the photothermographic recording material and aqueous dispersions may contain a spectral sensitizer, optionally together with a supersensitizer, for the silver halide appropriate for the wavelength of the light source which may in the near UV, visible, e.g. 630nm, 670nm etc., or IR, parts of spectrum.
• the silver halide may be spectrally sensitized with various known dyes including cyanine, merocyanine, styryl, hemicyanine, oxonol, hemioxonol and xanthene dyes optionally, particularly in the case of sensitization to infra-red radiation, in the presence of a so-called supersensitizer.
• various known dyes including cyanine, merocyanine, styryl, hemicyanine, oxonol, hemioxonol and xanthene dyes optionally, particularly in the case of sensitization to infra-red radiation, in the presence of a so-called supersensitizer.
• Useful cyanine dyes include those having a basic nucleus, such as a thiazoline nucleus, an oxazoline nucleus, a pyrroline nucleus, a pyridine nucleus, an oxazole nucleus, a thiazole nucleus, a selenazole nucleus and an imidazole nucleus.
• a basic nucleus such as a thiazoline nucleus, an oxazoline nucleus, a pyrroline nucleus, a pyridine nucleus, an oxazole nucleus, a thiazole nucleus, a selenazole nucleus and an imidazole nucleus.
• Useful merocyanine dyes which are preferred include those having not only the above described basic nuclei but also acid nuclei, such as a thiohydantoin nucleus, a rhodanine nucleus, an oxazolidinedione nucleus, a thiazolidinedione nucleus, a barbituric acid nucleus, a thiazolinone nucleus, a malononitrile nucleus and a pyrazolone nucleus.
• acid nuclei such as a thiohydantoin nucleus, a rhodanine nucleus, an oxazolidinedione nucleus, a thiazolidinedione nucleus, a barbituric acid nucleus, a thiazolinone nucleus, a malononitrile nucleus and a pyrazolone nucleus.
• imino groups or carboxyl groups are particularly effective.
• the photo-addressable thermally developable element and aqueous dispersions may further include a supersensitizer.
• Preferred supersensitizers are selected from the group of compounds consisting of: mercapto-compounds, disulfide-compounds, stilbene compounds, organoborate compounds and styryl compounds.
• any layer of the substantially light-insensitive thermographic material used in 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, USA. Coating may proceed from aqueous or solvent media with overcoating of dried, partially dried or undried layers.
• Thermographic imaging is carried out by the image-wise application of heat either in analogue fashion by direct exposure through an image or 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 substantially light-insensitive thermographic material preferably containing an infra-red absorbing compound, or by direct thermal imaging with a thermal head.
• 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.
• 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 1.0 ms, the pressure contact of the thermal printhead with the recording material being e.g. 200-1000g/linear cm, i.e. with a contact zone (nip) of 200 to 300 ⁇ m a pressure of 5000 to 50,000 g/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.
• 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, such as a CRT light source; a UV, visible or IR wavelength laser, such as a He/Ne-laser or an IR-laser diode, e.g. emitting at 780nm, 830nm or 850nm; or a light emitting diode, for example one emitting at 659nm; or by direct exposure to the object itself or an image therefrom with appropriate illumination e.g. with UV, visible or IR light.
• a finely focused light source such as a CRT light source
• a UV, visible or IR wavelength laser such as a He/Ne-laser or an IR-laser diode, e.g. emitting at 780nm, 830nm or 850nm
• a light emitting diode for example one
• 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 e.g. contact heating, radiative heating, microwave heating etc.
• Thermographic imaging can be used for the production of reflection type prints and transparencies, in particular for use in the medical diagnostic field in which black-imaged transparencies are widely used in inspection techniques operating with a light box.
• thermosensitive element in addition to the above-mentioned ingredients:
• thermographic materials of COMPARATIVE EXAMPLES 1 to 7 and INVENTION EXAMPLES 1 to 4 were prepared by coating a dispersion with the following ingredients in 2-butanone onto a 175 ⁇ m thick blue-pigmented polyethylene terephthalate support with CIELAB a*- and b*- values of -9.5 and -17.9 respectively subbed on the emulsion-coated side with subbing layer giving layers after drying at 85°C for 3 minutes in a drying cupboard with the compositions given in Table 1.
• the protective layer was hardened by heating the substantially light-insensitive thermographic material at 45°C for 7 days at a relative humidity of 70%.
• thermographic recording materials of COMPARATIVE EXAMPLES 1 to 7 and INVENTION EXAMPLES 1 to 4 were printed using a DRYSTARTM 4500 printer from AGFA-GEVAERT with a resolution of 508 dpi which had been modified to operate at a printing speed of 14 mm/s and a line-time of 3.5 ms instead of 7.1 ms and in which the 75 ⁇ m long (in the transport direction) and 50 ⁇ m wide thermal head resistors were power-modulated to produce different image densities.
• the maximum densities of the images were measured through a visible filter with a MACBETHTM TR924 densitometer.
• the stainless steel light-box used was 650mm long, 600mm wide and 120mm high with an opening 610mm long and 560mm wide with a rim 10mm wide and 5mm deep round the opening, thereby forming a platform for a 5mm thick plate of white PVC 630mm long and 580mm wide, making the white PVC-plate flush with the top of the light-box and preventing light loss from the light-box other than through the white PVC-plate.
• This light-box was fitted with 9 PlaniluxTM TLD 36W/54 fluorescent lamps 27mm in diameter mounted length-wise equidistantly from the two sides, with the lamps positioned equidistantly to one another and the sides over the whole width of the light-box and with the tops of the fluorescent tubes 30mm below the bottom of the white PVC plate and 35mm below the materials being tested.
• the shifts in CIELAB a*- and b*-values at an optical density, D, of 1.0 and the shift in the CIELAB b*-value were determined for COMPARATIVE EXAMPLES 1 to 7 and INVENTION EXAMPLES 1 to 4 and the results are also given in Table 2.
• thermographic recording materials of INVENTION EXAMPLES 1 to 4 whose thermosensitive elements contain TDZ-03, TDZ-04, TDZ-05 and TDZ-10, optionally substituted, optionally annelated five-membered heterocyclic ring compounds according to the present invention, instead of benzotriazole surprisingly exhibited better CIELAB b*-stability in archivability tests and much higher Dmax values than those observed with thermographic recording materials of COMPARATIVE EXAMPLES 3 to 7 whose thermosensitive elements contained optionally substituted, optionally annelated five-membered heterocyclic ring compounds all with the five-membered ring directly substituted with a mercapto group.
• thermographic recording materials of INVENTION EXAMPLES 1 to 4 containing TDZ-03, TDZ-04, TDZ-05 and TDZ-10 respectively instead of benzotriazole exhibited significantly higher maximum image densities, Dmax, when compared with the thermographic recording material of COMPARATIVE EXAMPLE 2 with benzotriazole, indicating a higher Dmax for a given coverage per unit area of substantially light-insensitive organic silver salt.
• thermographic recording material of COMPARATIVE EXAMPLES 1 in which the benzotriazole was omitted, a worse CIELAB b*-stability upon exposure in the light box than the thermographic recording material of COMPARATIVE EXAMPLE 2 containing benzotriazole.
• thermographic recording materials of INVENTION EXAMPLES 1 to 4 containing TDZ-03, TDZ-04, TDZ-05 and TDZ-10 respectively instead of benzotriazole exhibit comparable image tone of the fresh print, comparable CIELAB a*-archivability, improved CIELAB b*-archivability and better or comparable stability in light box experiments in addition to higher Dmax values.
• thermographic materials of COMPARATIVE EXAMPLES 8 to 13 were prepared by coating a dispersion with the following ingredients in 2-butanone onto the support described for COMPARATIVE EXAMPLES 1 to 7 and INVENTION EXAMPLES 1 to 4 giving layers after drying at 85°C for 3 minutes in a drying cupboard with the compositions given in Table 3. Comparative example nr.
• thermosensitive elements were then provided with a protective layer as described for COMPARATIVE EXAMPLES 1 to 7 and INVENTION EXAMPLES 1 to 4.
• thermographic properties of the substantially light-insensitive thermographic recording materials of COMPARATIVE EXAMPLES 8 to 13 were evaluated as described for COMPARATIVE EXAMPLES 1 to 7 and INVENTION EXAMPLES 1 to 4. The results are given in Table 4. Comparative Example nr.
• thermographic recording materials of COMPARATIVE EXAMPLES 10 to 13 whose thermosensitive elements contain 1-thia-3,4-diazole compounds with a mercapto (-SH) group instead of benzotriazole exhibited very poor CIELAB b*-stability to light box exposure, particularly with regard to Dmin-stability.
• thermographic recording materials of COMPARATIVE EXAMPLES 10 to 13 whose thermosensitive elements contain COMP-6 to COMP-9 exhibit Dmax values which are no higher than the substantially light-insensitive thermographic recording materials of COMPARATIVE EXAMPLES 8 and 9 with no stabilizer and benzotriazole respectively indicating no increase in Dmax for a given coverage per unit area of substantially light-insensitive organic silver salt with optionally annelated five-membered heterocyclic ring compounds outside the scope of the present invention.
• the present invention may include any feature or combination of features disclosed herein either implicitly or explicitly or any generalisation thereof irrespective of whether it relates to the presently claimed invention.

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