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
  • G03C1/49827—Reducing agents
• • 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
  • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers
  • B41M5/32—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers one component being a heavy metal compound, e.g. lead or iron

Definitions

• the present invention relates to thermographic recording materials whose prints have improved archival properties without loss in printability.
• EP 692 733 discloses a direct thermal recording process wherein a direct thermal recording material is heated dot-wise and the direct thermal recording material comprises on a substrate an imaging layer containing uniformly distributed in a film-forming polymeric binder (i) one or more substantially light-insensitive organic silver salts being no double salts, the silver salt(s) being in thermal working relationship with (ii) an organic reducing agent therefor, characterized in that the reducing agent is a benzene compound the benzene nucleus of which is substituted by no more than two hydroxy groups which are present in 3,4-position on the nucleus and have in the 1-position of the nucleus a substituent linked to the nucleus by means of a carbonyl group.
• the reducing agent is a benzene compound the benzene nucleus of which is substituted by no more than two hydroxy groups which are present in 3,4-position on the nucleus and have in the 1-position of the nucleus a substituent linked to the nucleus by means of
• the preferred carbonyl substituted 3,4-dihydroxy-benzene reducing agents are selected from the group consisting of 3,4-dihydroxy-benzoic acid, an alkyl or aryl ester thereof, 3,4-dihydroxy-benzaldehyde, 3,4-dihydroxy-benzamide and aryl or alkyl (3,4-dihydroxyphenyl) ketones.
• EP-A 692 733 exemplifies 3,4-dihydroxy-benzophenone.
• thermographic recording materials It is not only important that fresh prints produced with substantially light-insensitive thermographic recording materials exhibit the bluish tone necessary for reliable diagnosis with X-ray images, but also that the image tone is substantially maintained during storage in the dark in archives and also while being view in transmission using light-boxes i.e. exposed to visible light.
• Substantially light-insensitive thermographic recording materials should therefore be capable of producing bluish prints upon printing and this image tone should be substantially maintained during storage in the dark and during viewing on a light box while maintaining their sensitometry.
• Prior art materials do not provide this balance of properties.
• thermographic recording process for the above-mentioned monosheet black and white substantially light-insensitive thermographic recording material comprising the steps of: (i) providing the thermographic recording material; (ii) bringing the thermographic recording material into the proximity of a heat source; (iii) applying heat imagewise from the heat source to the thermographic recording material; and (iv) removing the thermographic recording material from the proximity of the heat source.
• the heat source is a thermal head.
• the heat source is a thin film thermal head.
• double salt with respect to organic silver salts means that silver is associated with another cation e.g. a magnesium ion or an iron ion.
• 3,4-dihydroxybenzene compound means a benzene compound with a substituent in the 1-position and hydroxy groups in the 3 and 4 positions.
• 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.
• the unified aromaticity index I A is described in C.W. Bird, Tetrahedron, 48(32), 335-340 (1992) and this publication also discloses aromaticity index values for a large range of aromatic groups.
• the substituent of the aryl group of the aryloxo-3,4-dihydroxybenzene in the thermosensitive element thereof is selected from the group consisting of aryl, hydroxy, carboxy, sulfo, sulfoalkyl, sulfoaryl, sulfonylalkyl, sulfonylaryl, annulated aryl, annulated heteroaryl, carboxyalkyl, carboxyaryl, oxoalkyl, oxoaryl, halogen, nitro, cyano and mercapto-alkyl groups.
• the heteroaryl group of the heteroaryloxo-3,4-dihydroxybenzene in the thermosensitive element thereof is selected from the group consisting of thiophenyl, pyrrolyl and pyridinyl groups.
• the aryloxo group of the aryloxo-3,4-dihydroxybenzene in the thermosensitive element thereof is selected from the group consisting of benzoyl, naphthoyl and anthracenoyl and phenanthrenoyl groups.
• the aryloxo-3,4-dihydroxybenzene in the thermosensitive element thereof is selected from the group consisting of 3,4-dihydroxy-4'-iodo-benzophenone, 3,4-dihydroxy-4'-bromo-benzophenone, 3,4-dihydroxy-4'-chloro-benzophenone, 3,4-dihydroxy-3'-chloro-benzophenone, 3,4-dihydroxy-3',4'-dichloro-benzophenone, 3,4-dihydroxy-4'-nitro-benzophenone and 3,4-dihydroxy-4'-cyano-benzophenone.
• Suitable aryloxo- or heteroaryloxo- 3,4-dihydroxybenzenes for use in the thermographic recording material of the present invention are: Combinations of aryloxo- or heteroaryloxo- 3,4-dihydroxy-benzene compounds may also be used that on heating become reactive partners in the reduction of the substantially light-insensitive organic silver salt.
• 3,4-dihydroxyphenyloxobenzenes can be prepared according to well documented procedures. Direct Friedel Craft-acylation on catechol, using acylchlorides or anhydrides and Lewis acid activation has been reported in the following literature: anhydrides and ZnCl 2 in Indian J. Chem. Sect. B, 26B(9), 823-6 (1987); acylbromides and AlBr 3 in CS 2 as a solvent in Chem. Ber., 119(1), 50-64 (1986); acylchlorides and AlCl 3 in chlorobenzene as solvent in Org. Prep. Proced. Int. 17(6), 401-7 (1985); acylchlorides and AlCl 3 in nitrobenzene as solvent in J. Chem. Soc., Dalton Trans., (2), 641-5 (1990); and anhydrides and AlCl 3 in dichloroethane as solvent in Eur. J. Med. Chem., 23(1), 45-52 (1988).
• Veratrol was chosen as the protected catechol, due to its availability in bulk. Friedel Crafts acylations on 1,2-dialkoxy benzenes are well documented in the literature, using e.g. FeCl 3 as a catalyst [C.R. Acad. Sci., Ser. Iic: Chim., 2(7-8), 455-465 (1999) or SnCl 4 as catalyst (Eur. Pat. Appl., 839801 (1998); J. Org. Chem., 55(17), 5078-88 (1990), J. Med. Chem., 30(10), 1914-18 (1987)].
• Several other catalysts and acylating reagents have been reported in the literature (Chem. Commun.
• thermosensitive element as used herein is that element which contains all the ingredients which contribute to image formation.
• the thermosensitive element contains a substantially light-insensitive organic silver salt, a 3,4-dihydroxybenzene compound as a reducing agent 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 salt is in reactive association with the reducing agent 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.
• the organic silver salt is not a double organic salt containing a silver cation associated with a second cation e.g. magnesium or iron ions.
• the organic silver salt is a substantially light-insensitive silver salt of an organic carboxylic acid.
• Organic silver salts may be dispersed by standard dispersion techniques e.g. using 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 a more finely ground dispersions of organic silver salts.
• Combinations of aryloxo- or heteroaryloxo- 3,4-dihydroxy-benzene compounds with at least one further reducing agent may also be used that on heating become reactive partners in the reduction of the substantially light-insensitive organic silver salt.
• thermosensitive element contains a reducing agent in addition to an aryloxo- or heteroaryloxo- 3,4-dihydroxy-benzene compound.
• the thermosensitive element further contains at least one reducing agent selected from the group consisting of 3,4-dihydroxybenzoate alkyl and aryl esters (such as ethyl 3,4-dihydroxybenzoate or n-butyl 3,4-dihydroxybenzoate), 3,4-dihydroxybenzophenone, 3,4-dihydroxy-acetophenone and 3,4-dihydroxybenzonitrile.
• a reducing agent selected from the group consisting of 3,4-dihydroxybenzoate alkyl and aryl esters (such as ethyl 3,4-dihydroxybenzoate or n-butyl 3,4-dihydroxybenzoate), 3,4-dihydroxybenzophenone, 3,4-dihydroxy-acetophenone and 3,4-dihydroxybenzonitrile.
• 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 substantially light-insensitive organic silver salt 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.
• the thermosensitive element contains a binder which does not contain additives or impurities which adversely affect the thermographic properties of the thermographic recording materials in which they are used.
• thermosensitive element further contains a so-called toning agent organic silver salt in order to obtain a neutral black image tone in the higher densities and neutral grey in the lower densities.
• Suitable toning agents are described in US 3,074,809, US 3,446,648 and US 3,844,797 and US 4,082,901.
• Other particularly useful toning agents are the heterocyclic toning 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.
• the thermosensitive element further contains 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
• 7-(ethylcarbonato)-benzo [e][1,3]oxazine-2,4-dione
• Stabilizers may be incorporated into the substantially light-insensitive thermographic recording materials of the present invention in order to obtain improved shelf-life and reduced fogging.
• the thermosensitive element further contains at least one stabilizer selected from the group consisting of benzotriazole; substituted benzotriazoles; tetrazoles; mercaptotetrazoles, such as 1-phenyl-5-mercapto-tetrazole; and aromatic polycarboxylic acids, such as ortho-phthalic acid, 3-nitro-phthalic acid, tetrachlorophthalic acid, mellitic acid, pyromellitic acid and trimellitic acid, and anhydrides thereof.
• benzotriazole substituted benzotriazoles
• tetrazoles mercaptotetrazoles, such as 1-phenyl-5-mercapto-tetrazole
• aromatic polycarboxylic acids such as ortho-phthalic acid, 3-nitro-phthalic acid, tetrachlorophthalic acid, mellitic acid, pyromellitic acid and trimellitic acid, and anhydrides thereof.
• thermosensitive element may comprise in addition at least one optionally substituted aliphatic (saturated as well as unsaturated aliphatic and also cycloaliphatic) 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 used in anhydride form or partially esterified form on the condition that at least two free carboxylic acids remain or are available in the heat recording step.
• thermosensitive element further contains glutaric acid.
• thermographic recording materials of the present invention may contain one or more surfactants, which may be anionic, non-ionic or cationic surfactants and/or one or more dispersants.
• the recording material may contain in addition to the ingredients mentioned above other additives such as levelling agents e.g. BAYSILONTM MA (from BAYER AG, GERMANY).
• levelling agents e.g. BAYSILONTM MA (from BAYER AG, GERMANY).
• the support for the thermosensitive element according to the present invention may be transparent, translucent or opaque and is a thin flexible carrier made of transparent resin film, e.g. made of a cellulose ester, cellulose triacetate, polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate.
• transparent resin film e.g. made of a cellulose ester, cellulose triacetate, 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. It may be pigmented with a blue pigment as so-called blue-base.
• One or more backing layers may be provided to control physical properties such as curl and static.
• thermosensitive element is provided with a protective layer to avoid local deformation of the thermosensitive element and to improve resistance against abrasion.
• thermosensitive element is provided with a protective layer comprising 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.
• thermosensitive element is provided with a protective layer comprising solvent-soluble polycarbonates as binders as described in EP-A 614 769.
• the thermosensitive element is provided with a protective layer comprising a water-soluble or water-dispersible binder, 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.
• the protective layer according to the present invention may be crosslinked. Crosslinking can be achieved by using crosslinking agents such as described in WO 95/12495. Solid or liquid lubricants or combinations thereof are suitable for improving the slip characteristics of the thermographic recording materials according to the present invention.
• thermosensitive element is provided with a protective layer comprising a solid thermomeltable lubricant such as those described in WO 94/11199.
• the protective layer of the thermographic recording material according to the present invention may comprise a matting agent.
• the thermosensitive element is provided with a protective layer comprising a matting agent such as described in WO 94/11198, e.g. talc particles, and optionally protrude from the protective layer.
• 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 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 1.0ms, 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.
• 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.
• 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 of the substantially light-insensitive recording materials of the INVENTION and COMPARATIVE EXAMPLES are:
• thermosensitive element Preparation of the thermosensitive element
• thermosensitive elements of COMPARATIVE EXAMPLES 1 to 12 and COMPARATIVE EXAMPLES 1 to 5 were produced by coating a 2-butanone dispersion with the following ingredients onto a subbed 168 ⁇ m thick blue-pigmented polyethylene terephthalate support, with CIELAB a* and b* values of -7.9 and -16.6 respectively, to produce layers with the compositions given in Table 1.
• thermosensitive elements of the thermographic recording materials of INVENTION EXAMPLES 1 to 12 and COMPARATIVE EXAMPLES 1 to 5 were then coated with an aqueous composition with the following composition:
• thermographic recording materials of INVENTION EXAMPLES 1 to 12 and COMPARATIVE EXAMPLES 1 to 5 were printed using a DRYSTAR® 2000 printer from AGFA-GEVAERT equipped with a thin film thermal head with adapted to increase its resolution from 300 dpi (standard) to 508 dpi and operated with a line time of 12 ms and a maximum printing power of 34 mW/pixel (the line time being the time needed for printing one line). During this line time the print head received constant power.
• the thermal head resistors were time-modulated to produce different image densities.
• the image tone of fresh prints made with the substantially light-insensitive thermographic recording materials of INVENTION EXAMPLES 1 to 12 and COMPARATIVE EXAMPLES 1 to 5 was assessed on the basis of the L*, a* and b* CIELAB-values.
• the L*, a* and b* CIELAB-values were determined by spectrophotometric measurements according to ASTM Norm E179-90 in a R(45/0) geometry with evaluation according to ASTM Norm E308-90.
• the a* and b* CIELAB-values of fresh prints of the substantially light-insensitive thermographic recording materials of INVENTION EXAMPLES 1 to 12 and COMPARATIVE EXAMPLES 1 to 5 at an optical density, D, of 1.0 are given in Table 2.
• a negative CIELAB a*-value indicates a greenish image-tone becoming greener as a* becomes more negative, a positive a*-value indicating a reddish image-tone becoming redder as a* becomes more positive.
• a negative CIELAB b*-value indicates a bluish tone which becomes increasingly bluer as b* becomes more negative and a positive b*-value indicates a yellowish image-tone becoming more yellow as b* becomes more positive.
• the image tone of elements of the image with a density of 1.0 have a stronger effect than the image tone of elements with lower or higher optical density.
• the substantially light-insensitive thermographic recording materials of INVENTION EXAMPLES 2, 3, 5 to 10 and 12 exhibit much bluer image tones at a density of 1.0, as shown by their simultaneously exhibiting highly positive a* and highly positive b* CIELAB-values.

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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)
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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 2001
  • 2001-03-29 EP EP01000096A patent/EP1245404A1/fr not_active Withdrawn
• 2002
  • 2002-03-28 JP JP2002091967A patent/JP3856379B2/ja not_active Expired - Fee Related

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