DE69910719T2 - Thermographic black and white recording material with improved stability against direct sunlight - Google Patents

Description

technical Field of the invention

The present invention relates substantially light-insensitive monochrome thermographic monochrome recording materials with improved durability against direct sunlight.

general State of the art

In thermal imaging or thermography is a recording method, at the pictures with the help of heat energy be generated. In direct thermal thermography becomes a visible Image created by imagewise heating a recording material containing substances whose color or optical Density changes due to chemical or physical processes. at most of the "direct" thermographic Recording materials are those of the chemical type. When heated to a certain transformation temperature is a irreversible chemical reaction, and a colored image is produced.

In BE-A 784 615 a photographic Material with a paper carrier discloses, characterized in that the carrier with a layer having a Sheffield smoothness between 5 and about 100 coated which layer is a first polysaccharide-type binder, a pigment, a second binder, a radiation-sensitive Compound such as 2,4-dihydroxybenzophenone, and an oxidizing-reducing Includes imaging system.

In EP-A 713 133, a thermal Double sheet image generation system disclosed consisting of (i) a Donor element on a support a donor layer with a binder and a thermally transferable Reducing agent that convert a silver source to metallic silver can, contains, and (ii) an image-receiving element supported on a support contains image-receiving layer, the one silver source that is under the action of heat in the presence a reducing agent is reducible, a binder and a Stabilizer from the group consisting of benzotriazoles, heterocyclic Mercaptans, sulfinic acids, 1,3,4-triazoindinolines, 1,3-dinitroaryl compounds, 1,2,3-triazoles, phthalic and phthalic acid derivatives contains.

EP-A 809 142 discloses a recording material discloses a carrier, a thermosensitive element and a protective layer for the heat sensitive Contains element wherein the heat-sensitive element a substantially light-insensitive organic silver salt organic reducing agent for it in a thermally effective relationship thereto and a binder, wherein the heat sensitive Element further in reactive relation to the substantially light-insensitive organic silver salt and the organic reducing agent substituted or unsubstituted Contains compound being for the substitution no groups with an exclusively electron-attracting Kind in question and the connection an unsaturated one 5-membered heterocyclic, with an aromatic ring system contains fused ring, wherein the ring consists of nitrogen and carbon atoms and at least one of the nitrogen atoms has a hydrogen atom and none of the carbon atoms are bonded directly to a sulfur atom is or is part of a carbonyl group.

As with substantially light-insensitive black and white double-sheet thermographic recording materials EP 713 133 In the receiving sheet an image is obtained with imagewise transferred reducing agent, here are in terms of durability completely different requirements than for single sheet materials. Substantially light-insensitive black-and-white monochrome thermographic recording materials containing non-N-substituted benzotriazoles taught by EP-A 809 142 have poor resistance to direct sunlight.

Tasks of present invention

Object of the present invention it is accordingly, a material light-insensitive black-and-white monochrome thermographic recording material based on organic silver salts and reducing agents, that improved durability against direct sunlight and has a picture with an acceptable neutral picture tone is able to provide.

Other tasks and benefits of The present invention will become apparent from the following description seen.

Short illustration of the present invention

It has unexpectedly been found that by embedding non-chlorine-containing 2- (2'-hydroxyphenyl) -benzotriazole derivatives and 2-hydroxybenzophenone derivatives in substantially light-insensitive thermo black and white single-sheet graphic recording materials based on organic silver salts and reducing agents, materials are obtained which give prints with improved resistance to direct sunlight and an acceptably neutral image tone.

Are solved the above Tasks by a substantially light-insensitive, thermographic, a non-chlorine-containing stabilizer containing black and white single-sheet recording material with a carrier and a heat-sensitive one Element, being the heat-sensitive Element a substantially light-insensitive organic silver salt, a reducing agent for it in thermally effective relationship thereto and a binder thereby characterized in that non-chlorine-containing stabilizer from the group consisting of 2- (2'-hydroxyphenyl) benzotriazole derivatives and 2-hydroxybenzophenone derivatives.

Are solved the above Tasks also by a marked by the following steps Recording method: (i) arranging an outer layer of the above-mentioned thermographic Recording material nearby a heat source, (ii) imagewise of the recording material with heat supplied from the heat source Preparation of an image, wherein the recording material in the Near the Heat source is maintained, and (iii) removing the recording material from the heat source.

The objects of the invention are achieved also by the use of a non-chlorine-containing stabilizer from the group consisting of 2- (2'-hydroxyphenyl) benzotriazole derivatives and 2-hydroxybenzophenone derivatives as a stabilizer against direct Sunlight in a substantially light-insensitive thermographic Black and white monosheet recording material with a carrier and a heat-sensitive one Element, being the heat-sensitive Element a substantially light-insensitive organic silver salt, a reducing agent for it in a thermally effective relationship thereto and a binder.

Embodiments preferred according to the invention are in the subclaims described.

Detailed description of the present Invention.

In a preferred embodiment the recording method according to the invention it is the heat source is a thermal head and is a thin-film thermal head particularly preferred.

definitions

By "substantially insensitive to light" is meant "not on purpose sensitive to light. "

By "non-chlorine-containing compound" is meant a Compound containing no chlorine atoms in their structure.

By "polymer having active hydrogen atoms" is meant a Polymer with substituents with very reactive hydrogen atoms such as Hydroxyl groups, thiol groups, carboxyl groups, -N-H groups; amino groups, Amido groups etc.

By "polyisocyanate" is meant a Compound having at least two isocyanate groups, optionally with while a hardening quickly displaceable Groups are blocked.

2- (2'-hydroxyphenyl) benzotriazole derivatives and 2-hydroxybenzophenone derivatives

• – STAB 01: 2-(2'-Hydroxy-5-methylphenyl)-benztriazol, TINUVIN^TM P von CIBA-GEIGY,
• – STAB 02: 2-(2'-Hydroxy-5'-t-octylphenyl)-benztriazol, CYASORB^TM UV 5411 von American Cyanamid Co.,
• – STAB 03: 2-[2'-Hydroxy-3',5'-(di-t-butyl)-phenyl]-benztriazol, TINUVIN^TM 320 von CIBA-GEIGY:
  
• – STAB 04: 2-[2'-Hydroxy-3',5'-(di-t-amyl)-phenyl]-benztriazol, TINUVIN^TM 328 von CIBA-GEIGY:
  
• – STAB 05: 2-[2'-Hydroxy-3',5'-di-(α,α-dimethylbenzyl)-phenyl]-benztriazol, TINUVIN^TM 900 von CIBA-GEIGY:
  
• – STAB 06: 2-[2'-Hydroxy-5-(1'',1'',3'',3''-tetramethylbutyl)-phenyl]-benztriazol:
• – STAB 07: 2,2-Methylen-bis-[5-(2H-benztriazol-1-yl)-3-(1'',1'',3'',3''-tetramethylbutyl)-phenol]:
  
• – STAB 08: 2-{3'-t-Butyl-2'-hydroxy-5'-[2-ethyl-(methylpolyethylenoxid)-keton]-phenyl}-benztriazol:
  
• – STAB 09: TINUVIN^TM 213 von CIBA-GEIGY,
• – STAB10: 2-{3'-t-Butyl-2'-hydroxy-5-3-(octylpropionat)-phenyl}-benztriazol, TINUVIN^TM 384 von CIBA-GEIGY:
  
• – STAB 11:
  

Preferred non-chloro-containing 2- (2'-hydroxyphenyl) -benzotriazole derivatives have substituents on the benzene ring of the benzotriazole and / or phenyl group, for example, alkyl groups such as a methyl group, a t-butyl group, a t-amyl group, a t -Octyl group, etc., an aryl group, an alkaryl group, an aralkyl group such as a benzyl group, an α, α-dimethylbenzyl group, etc., an alkoxy group, an alkylcarboxylate group, etc. These groups may further be represented by a hydroxyl group, an alkyl group, an alkaryl group, a Aralkyl group, an aryl group, an alkoxy group, an alkylcarboxylate group, a 2-benztriazole group, etc. For use in the substantially light-insensitive stabilizer-containing monochrome single-sheet recording material of the present invention, suitable non-chloro-containing 2- (2'-hydroxyphenyl) -benzotriazole derivatives which do not impair the neutrality of the image tone of the image background are

• STAB 01: 2- (2'-hydroxy-5-methylphenyl) benzotriazole, TINUVIN ^™ P from CIBA-GEIGY,
• STAGE 02: 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, CYASORB ^™ UV 5411 from American Cyanamid Co.,
• STAGE 03: 2- [2'-hydroxy-3 ', 5' - (di-t-butyl) -phenyl] -benzotriazole, TINUVIN ^™ 320 from CIBA-GEIGY:
  
• STAB 04: 2- [2'-hydroxy-3 ', 5' - (di-t-amyl) -phenyl] -benzotriazole, TINUVIN ^™ 328 from CIBA-GEIGY:
  
• STAGE 05: 2- [2'-hydroxy-3 ', 5'-di (α, α-dimethylbenzyl) -phenyl] -benzotriazole, TINUVIN ^™ 900 from CIBA-GEIGY:
  
• STAGE 06: 2- [2'-Hydroxy-5- (1 '', 1 '', 3 '', 3 '' - tetramethylbutyl) -phenyl] -benzotriazole:
• STAB 07: 2,2-methylenebis [5- (2H-benztriazol-1-yl) -3- (1 '', 1 '', 3 '', 3 '' - tetramethylbutyl) phenol]:
  
• - STAB 08: 2- {3'-t-butyl-2'-hydroxy-5 '- [2-ethyl- (methylpolyethyleneoxide) -ketone] -phenyl} -benzotriazole:
  
• - STAB 09: TINUVIN ^™ 213 from CIBA-GEIGY,
• STAB10: 2- {3'-t-butyl-2'-hydroxy-5-3- (octylpropionate) -phenyl} -benzotriazole, TINUVIN ^™ 384 from CIBA-GEIGY:
  
• - STAB 11:
  

• – STAB 12: 2,4-Dihydroxybenzophenon,
• – STAB 13: 2-Hydroxy-4-methoxybenzophenon
  
• – STAB 14: 2-Hydroxy-4-n-octyloxybenzophenon,
• – STAB 15: 2-Hydroxy-4-isooctyloxybenzophenon,
• – STAB 16: 2-Hydroxy-4-dodecyloxybenzophenon,
• – STAB 17: 2,2'-Dihydroxy-4-methoxybenzophenon,
• – STAB 18: 2,2',4,4'-Tetrahydroxybenzophenon,
• – STAB 19: 2,2'-Dihydroxy-4,4'-dimethoxybenzophenon.

Preferred non-chloro-2-hydroxybenzophenone derivatives have substituents on the benzene ring of one or both benzene rings, for example, an alkyl group, an aryl group, an alkaryl group, an aralkyl group, a hydroxyl group, an alkoxy group, an alkyl carboxylate group, etc. For use in the substantially light-insensitive, stabilizer-containing monochrome monosheet recording material are suitable non-chloro-2-hydroxybenzophenone derivatives which do not affect the neutrality of the image background image tone

• STAB 12: 2,4-dihydroxybenzophenone,
• - STAB 13: 2-hydroxy-4-methoxybenzophenone
  
• STAGE 14: 2-hydroxy-4-n-octyloxybenzophenone,
• STAGE 15: 2-hydroxy-4-isooctyloxybenzophenone,
• STAGE 16: 2-hydroxy-4-dodecyloxybenzophenone,
• STAGE 17: 2,2'-dihydroxy-4-methoxybenzophenone,
• STAB 18: 2,2 ', 4,4'-tetrahydroxybenzophenone,
• STAGE 19: 2,2'-dihydroxy-4,4'-dimethoxybenzophenone.

gewählt.In a preferred embodiment of the thermographic recording material according to the invention, the non-chlorine-containing 2- (2'-hydroxyphenyl) -benzotriazole derivative contains a 2-hydroxybenzophenone group. In a further preferred embodiment of the present invention, the non-chlorine-containing 2- (2'-hydroxyphenyl) -benzotriazole derivative used according to the invention is selected from the group consisting of 2- [2'-hydroxy-3 ', 5' - (di-t-butyl ) -phenyl] -benzotriazole, 2- [2'-hydroxy-3 ', 5'-di- (α, α-dimethylbenzyl) -phenyl] -benzotriazole, 2,2-methylene-bis- [5- (2H-) benztriazol-1-yl) -3- (1 '', 1 '', 3 '', 3 '' - tetramethylbutyl) -phenol], 2,2-methylenebis [5- (2H-benztriazole-1] yl) -3- (1 '', 1 '', 3 '', 3 '' - tetramethylbutyl) -phenol],

selected.

Mixtures of one or more 2- (2'-hydroxyphenyl) benzotriazole derivatives, one or more 2-hydroxybenzophenone derivatives or one or more several 2- (2'-hydroxyphenyl) benzotriazole derivatives with one or more 2-hydroxybenzophenone derivatives also come for use in the thermographic according to the invention Recording material in question.

thermosensitive element

The heat-sensitive element of the invention contains a substantial light-insensitive organic silver salt, a reducing agent for in thermally effective relationship thereto and a binder. The element may contain a layer dressing in which the ingredients in various layers can be dispersed, with the proviso that the essential light-insensitive organic silver salt and the reducing agent are in reactive relationship with each other, d. H. during the heat generation must the reducing agent so be that included to diffuse to the particles of the substantially light-insensitive organic silver salt able to cause the reduction to silver. In a preferred embodiment contains the heat sensitive Element furthermore a polymer with active hydrogen atoms, from which at least a part has reacted with a polyisocyanate.

organic silver salts

Preferred substantially light-insensitive organic silver salts for use in the thermosensitive element of used according to the invention substantially light-insensitive black-and-white thermographic recording material are silver salts of as fatty acids known aliphatic carboxylic acids, in which the aliphatic carbon chain is preferably at least Contains 12 carbon atoms, these silver salts are also referred to as "silver soaps". Combinations of various organic silver salts are also suitable for Use in the recording materials according to the invention.

reducing agent

Suitable organic reducing agents for the reduction of the substantially light-insensitive organic silver salts are organic compounds containing at least one active, bonded to O, N or C hydrogen atom, as is the case for catechol, hydroquinone, aminophenols, METOL ^™ , p-phenylenediamines, alkoxynaphthols , z. For example, 4-methoxy-1-naphthol, as described in US-P 3,094,417, reducing agent of the pyrazolidin-3-one type, z. PHENIDONE ^™ , pyrazolin-5-ones, indane-1,3-dione derivatives, hydroxytetronic acids, hydroxytetronimides, hydroxylamine derivatives, as described, for example, in U.S. Pat. No. 4,082,901, hydrazine derivatives and reductones, e.g. As ascorbic acid. It should also be noted in U.S. Patents 3,074,809, 3,080,254, 3,094,417 and 3,887,378.

in der bedeuten:
n 0 oder 1,
R -(C=O)R¹, -(C=O)NR¹R², -CN, -SO₃R¹, -SO₂R¹, -SOR¹, -SO₂NR¹R² oder -PO₃R¹R²,
R¹ ein Wasserstoffatom, eine gegebenenfalls substituierte Alkylgruppe oder eine gegebenenfalls substituierte Arylgruppe,
R² ein Wasserstoffatom, eine gegebenenfalls substituierte Alkylgruppe oder eine gegebenenfalls substituierte Arylgruppe, und wobei R¹ und R² zusammen die zum Schließen eines Ringes benötigten Atome bedeuten dürfen, wobei es sich um einen carbocyclischen Ring handeln kann, dessen Atome ausschließlich Kohlenstoffatome sind, oder um einen heterocyclischen Ring, dessen Atome Kohlenstoffatome und zumindest ein Nicht-Kohlenstoffatom wie z. B. Stickstoff, Schwefel, Sauerstoff, Phosphor usw. sind. Die Alkylgruppen und Arylgruppen dürfen ebenfalls mit einer oder mehreren Gruppen aus der Reihe bestehend aus einer Hydroxylgruppe, einer Cyangruppe, einer Thiolgruppe und einem Halogenatom substituiert sein. Besonders bevorzugte -(CH=CH)_nR-Gruppen sind eine Formylgruppe, eine Oxoalkylgruppe, eine Oxoarylgruppe, eine Cyangruppe, eine Carbamidogruppe, eine Diphenoxyphosphorylgruppe, eine Alkylsulfinylgruppe, eine Alkylsulfonylgruppe und eine Sulfonylaminogruppe.The heat sensitivity of the imaging material and the gradation of the image are determined by the choice of reducing agent type. Image forming materials containing gallates, for example, have a high gradation. In a preferred embodiment according to the invention, the thermographic element contains a 3,4-dihydroxyphenyl compound with ethyl 3,4-dihydroxybenzoate, butyl 3,4-dihydroxybenzoate and 3,4-dihydroxybenzoic acid and compounds of the formula (I):

in which mean
n 0 or 1,
R - (C =O) R ¹ , - (C =O) NR ¹ R ² , -CN, -SO ₃ R ¹ , -SO ₂ R ¹ , -SOR ¹ , -SO ₂ NR ¹ R ² or -PO ₃ R ¹ R ² ,
R ^{1 represents} a hydrogen atom, an optionally substituted alkyl group or an optionally substituted aryl group,
R ^{2 is} a hydrogen atom, an optionally substituted alkyl group or an optionally substituted aryl group, and wherein R ¹ and R ² together may be the atoms needed to close a ring, which may be a carbocyclic ring whose atoms are exclusively carbon atoms, or to a heterocyclic ring whose atoms have carbon atoms and at least one non-carbon atom such. As nitrogen, sulfur, oxygen, phosphorus, etc. are. The alkyl groups and aryl groups may also be substituted with one or more of the group consisting of a hydroxyl group, a cyano group, a thiol group and a halogen atom. Particularly preferred - (CH = CH) _n R groups are a formyl group, an oxoalkyl group, an oxoaryl group, a cyano group, a carbamido group, a diphenoxyphosphoryl group, an alkylsulfinyl group, an alkylsulfonyl group and a sulfonylamino group.

There can also be combinations be used by reducing agents that when heated to participants on the reduction reaction of the substantially light-insensitive organic Become silver salt.

tint

To obtain a neutral black Picture tones in the upper density zones and from neutral gray in the lower ones Contains density zones the heat sensitive Element preferably also a so-called, from the thermography or photothermography known Tönungsmittel.

Suitable toning agents are the general ones Formulas in US-P 4 082 901 corresponding phthalimides and phthalazinones and the in US Pat. No. 3,074,809, US Pat. No. 3,446,648 and US Pat. No. 3,844,797. Other particularly useful toning agents are the heterocyclic toner compounds of the benzoxazinedione or naphthoxazinedione type as described in GB-P 1,439,478, US-P 3,951,660 and U.S. Patent 5,599,647.

binder

As the film-forming binder of the heat-sensitive element containing mixed crystals of two or more organic silver salts, any kinds of natural, modified natural or synthetic resins or mixtures of such resins in which the organic silver salts are homogeneously dispersible either in aqueous media or solvent media are suitable , z. As cellulose derivatives such as ethyl cellulose, cellulose esters, eg. Cellulose nitrate, carboxymethyl cellulose, starch ethers, gallactomannan, Polymers derived from α, β-ethylenically unsaturated compounds such as polyvinyl chloride, post-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 acetal derived from polyvinyl alcohol as starting material, wherein only a part of polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters, polystyrene and polyethylene or mixtures thereof.

Suitable water-soluble film-forming binders for use in thermographic according to the invention Recording materials are polyvinyl alcohol, polyacrylamide, polymethacrylamide, Polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, Polyethylene glycol, proteinaceous binders such as gelatin, modified Gelatins such as phthaloyl gelatin, polysaccharides such as starch, gum arabic and dextran, and water-soluble Cellulose derivatives. A preferred water-soluble binder for use in the thermographic according to the invention Recording materials is gelatin.

Preferred water-dispersible binders for use in the present invention are water-dispersible film-forming polymers with covalently bonded ionic groups from the group consisting of sulfonate, sulfinate, carboxylate, phosphate, quaternary ammonium groups, tertiary Sulfonium groups and quaternary Phosphonium. Further preferred water-dispersible binders for use in the present invention are water-dispersible Film-forming polymers with covalently bonded portions with a or more acid groups. Water-dispersible binders with crosslinkable groups, eg. B. Epoxy groups, acetoacetoxy groups and crosslinkable double bonds are also preferred. Further preferred water-dispersible Binders for use in the thermographic recording materials according to the invention are polymeric latices.

The weight ratio of the binder to Organic silver salt is preferably between 0.2 and 6 and the strenght the heat-sensitive Elements preferably between 5 and 50 microns.

Other stabilizers and antifreeze

To improve the shelf life and for limitation of fogging can in the invention used substantially light-insensitive black-and-white thermographic recording material Stabilizers and antifreezes are embedded. to use according to the invention suitable stabilizer compounds are unsaturated, carbocyclic or heterocyclic -SA group-substituted compounds, where A is a hydrogen atom, a counterion for balancing the negative charge of Thiolate group or a symmetrical or asymmetric disulfide is forming group.

Surfactants and dispersant

Facilitate surfactants and dispersants dispersing ingredients that are not in the dispersion medium used soluble are. The invention used substantially light-insensitive black-and-white thermographic recording material may be one or more anionic, nonionic or cationic surfactants and / or one or more dispersants.

Suitable dispersants are natural polymeric substances, synthetic polymeric substances and finely divided powders, for example, finely divided non-metallic inorganic powders like silica.

Other ingredients

In addition to the above-mentioned ingredients, the substantially light-insensitive black-and-white thermographic recording material may contain other ingredients such as free fatty acids, antistatic agents, e.g. As non-ionic antistatic agents with a fluorocarbon group such as. In F ₃ C (CF ₂ ) ₆ CONH (CH ₂ CH ₂ O) -H, silicone oil and silica.

carrier

The support for the invention used substantially light-insensitive black-and-white thermographic recording material can be translucent or translucent and is preferably a thinner pliable carrier made of translucent Resin, z. B. from a cellulose ester, for. B. cellulose triacetate, Polypropylene, polycarbonate or polyester, e.g. For example, polyethylene terephthalate. The carrier may be in the form of a bow, ribbon or web and if necessary subbed to bond to the heat-sensitive material applied to it Element to improve. The carrier can be colored or pigmented to give the picture a translucent colored background to rent.

protective layer

The protective layer protects that thermosensitive Element from humidity and surface damage from scratching, etc. and prevents direct contact of printheads or heat sources with the Recording layers. On protective layers that come in contact with a Heat source come and be conveyed past it under pressure have to, the requirement is made that they be resistant to local deformation and have good sliding properties when used during the Heating be promoted by the heat source over.

Solid or liquid lubricants or combinations the same are suitable for improving the sliding properties the thermographic invention Recording materials. Solid lubricants usable in accordance with the invention are polyolefin waxes, ester waxes, polyolefin-polyether block copolymers, amide waxes, Polyglycols, fatty acids, Fatty alcohols, natural Waxes and solid phosphoric acid derivatives. preferred Solid lubricants are thermally melting particles such as those in WO 94/11199 described. Usable according to the invention liquid lubricant are fatty acid esters such as glycerol trioleate, sorbitan monooleate and sorbitan trioleate, silicone oil derivatives and phosphoric acid derivatives.

The protective layer of the recording material according to the invention may contain a matting agent. Suitable matting agents are described in WO 94/11198, u. a. Talc particles, and optionally protrude from the Protective layer out.

In a preferred embodiment of the invention essential light-insensitive black-and-white monochrome thermographic recording material the heat sensitive Element covered with a protective layer, the one second polymer with active hydrogen atoms and a second one Polyisocyanate contains.

antihalation

Except for the above ingredients can the invention used thermographic recording materials also infrared light contain anti-halation dyes or shade dyes, the infrared light, which is the heat-sensitive one Element has penetrated, absorb and convert into heat and thus reflection to prevent this light. Such dyes can in the heat-sensitive Element or incorporated into any other layer of the novel recording material become.

coating techniques

The order of any layer of the used according to the invention essentially light-insensitive black-and-white thermographic recording material can be done by any coating technique, 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, UNITED STATES. The coating may be from an aqueous medium or a solvent medium by coating dried, partially dried or non-dried layers take place.

thermographic pressure

The direct thermal imaging takes place by imagewise admission with heat, either analogously by direct exposure through an image or by reflection from an image or in a digital manner pixel-by-pixel exposure with an infrared heater source, for example an Nd-YAG laser or other infrared laser, or through direct thermal imaging with a thermal head.

Under thermal pressure, image signals are converted into electrical impulses which are then selectively applied to a thermal print head via a driver circuit. The thermal print head consists of microscopic thermal resistance elements that convert the electrical energy into heat via the Joule effect. The electrical pulses thus converted into thermal signals express themselves as heat transmitted to the surface of the thermal paper in which the color-developing chemical reaction takes place. Such thermal printheads may be placed in contact with or in close proximity to the recording layer. The operating temperature of conventional thermal print heads is between 300 and 400 ° C and the heating time per pixel (pixel) may be less than 1.0 ms, wherein the pressure contact of the thermal print head with the recording material z. B. between 200 and 500 g / cm ² , to ensure good heat transfer.

In order to prevent direct contact of the thermal printheads with a recording layer not coated with an outer protective layer, the imagewise heating of the recording layer with the thermal printheads may be prevented by an in contact, but removable, resin sheet or resin sheet to which recording material can not be transferred during the heating.

The image signals for modulating the Laser beam or current in the micro-resistances of a thermal printhead are either received directly or from a cache, optionally connected to a digital imaging workstation in which The image information can be processed to special needs meet.

The control of the heating elements can be power modulated or pulse length modulated at constant power become. EP-A 654 355 describes a method of production a picture by imagewise heating by means of a thermal head with excitable heating elements, wherein the Control of the heating elements after a duty cycling operation he follows. When used in thermographic thermal head printheads Recording the recording materials are not suitable for reproduction of pictures with a fairly high number of grayscale, like which is required for halftone reproduction. In EP-A 622 217 is a method of generating an image using a for direct thermal imaging of suitable element disclosed, wherein a improved halftone reproduction is achieved. For the imagewise heating of the thermographic Material is also suitable embedded in the material electrical resistance band. The pictorial or patterned heating of the thermographic material can also by a pixel by pixel modulated ultrasound treatment are made.

industrial application

The thermographic imaging can for the generation of both transparencies and supervisory copies be used. Purpose as an application of the present invention is the area of graphic images where high-contrast Pictures with very steep dependence the print density of the energy applied to a point is required. For hard copies thermographic is used Recording materials on a white opaque carrier, while at with a viewing device working examination techniques Find black-image transparent widespread application.

• – organisches Silbersalz: AgBeh = Silberbehenat,
• – Bindemittel: BR 18 = PIOLOFORM BR 18, ein Polyvinylbutyral von WACKER CHEMIE, LL4160 = PIOLOFORM LL4160, ein Polyvinylbutyral von WACKER CHEMIE,
• – Reduktionsmittel: R01 = Ethyl-3,4-dihydroxybenzoat, R02 =
  
• – Polyisocyanate: N100 = DESMODUR^TM N100 von BAYER,
• – Tönungsmittel: T01 = Benzo[e]-[1,3]-oxazin-2,4-dion, T02 = 7-(Ethylcarbonat)-benzo[e]-[1,3]-oxazin-2,4-dion,
• – Silikonöl: Öl = BAYSILON^TM MA, ein Polydimethylsiloxan von BAYER,
• – Stabilisatoren: S01 = Tetrachlorphthalsäureanhydrid, S02 = 3'-Decanoylamino-1-phenyl-1H-tetrazol-5-thiol
  
  S05 = TINUVIN^TM 327, ein 2-[2'-Hydroxy-3',5'-(di-t-butyl)-phenyl)-5-chlorbenztriazol von CIBA-GEIGY:
  
  
  S07 = Zinkoxid, und in der Schutzschicht werden die nachstehenden zusätzlichen Ingredienzien verwendet:
• – MICRODOL^TM SUPER, ein Talk von Norwegian Talc AS,
• – TEGOGLIDE^TM 410, ein Polysiloxan/Polyether-Blockcopolymer von Goldschmidt,
• – SYLOID^TM 72, eine kolloidale Kieselsäure von GRACE.

The following examples of the invention and comparative examples illustrate the present invention. The percentages and ratios in these examples are by weight unless otherwise stated. In addition to the above-mentioned ingredients, the following ingredients are also used in the examples and comparative examples of the present invention:
in the heat-sensitive element:

• - organic silver salt: AgBeh = silver behenate,
• Binder: BR 18 = PIOLOFORM BR 18, a polyvinyl butyral from WACKER CHEMIE, LL 4160 = PIOLOFORM LL 4160, a polyvinyl butyral from WACKER CHEMIE,
• Reducing agent: R01 = ethyl-3,4-dihydroxybenzoate, R02 =
  
• Polyisocyanates: N100 = DESMODUR ^™ N100 from BAYER,
• Tinting agent: T01 = benzo [e] - [1,3] oxazine-2,4-dione, T02 = 7- (ethyl carbonate) benzo [e] - [1,3] oxazine-2,4-dione .
• Silicone oil: oil = BAYSILON ^™ MA, a BAYER polydimethylsiloxane,
• Stabilizers: S01 = tetrachlorophthalic anhydride, S02 = 3'-decanoylamino-1-phenyl-1H-tetrazole-5-thiol
  
  S05 = TINUVIN ^™ 327, a 2- [2'-hydroxy-3 ', 5' - (di-t-butyl) -phenyl) -5-chlorobenzotriazole from CIBA-GEIGY:
  
  
  S07 = zinc oxide, and in the protective layer the following additional ingredients are used:
• - MICRODOL ^™ SUPER, a talc from Norwegian Talc AS,
• TEGOGLIDE ^™ 410, a polysiloxane / polyether block copolymer from Goldschmidt,
• - SYLOID ^TM 72, a colloidal silicic acid from GRACE.

INVENTIVE EXAMPLES 1 to 6 and COMPARATIVE EXAMPLES 1 to 9

Production of heat-sensitive Elements

A composition containing 2-butanone as solvent / dispersion medium is knife-coated onto the 120 μm thick substrated polyethylene terephthalate support. After 3 minutes of curing at 85 ° C., a heat-sensitive element having the compositions listed in Table 1 below is obtained: AgBeh 3.149 g / m ² BR 18 3.149 g / m ² R01 0.643 g / m ² T01 0.172 g / m ² oil 0.012 g / m ² S01 0.075 g / m ² S02 0.068 g / m ² N100 0.315 g / m ²

On the thermosensitive element of the thermographic recording materials of COMPARATIVE EXAMPLES 1 to 9 and the INVENTION EXAMPLES 1 to 6, the following protective layer compositions are then applied and cured at 85 ° C for 3 minutes: Table 1

thermographic pressure

The printer comes with a thin-film thermal print head with a resolution equipped with 300 dpi and is at a line time of 6.5 ms (the line time is the time required to print a single line). While This line time, the print head is constantly energized. The middle Printing power, which is the total amount needed to print a line Energy, divided by the line time and the specific surface of the heat-generating resistors, corresponds to 1.6 mJ / dot and extends to all the thermographic recording materials COMPARATIVE EXAMPLES 1 to 9 and the INVENTION EXAMPLES 1 to 6 to obtain a maximum optical density.

The maximum and minimum density of the prints are measured in a MACBETH ^™ TR924 densitometer behind an optical filter in the gray scale step corresponding to the data planes 64 and 0, respectively. The measured values are listed in Table 2.

Storage stability test

For the evaluation of the storage stability of the thermographic recording materials of COMPARATIVE EXAMPLES 1 to 9 and the INVENTION EXAMPLES 1 to 6, the changes of the maximum density (ΔD _max ) and the change of the CIELAB values a * and b * at the minimum density are determined. The CIELAB values are determined according to spectrophotometric measurements according to ASTM standard E179-90 in an R (45/0) geometry and the evaluation is carried out according to ASTM standard E308-90. The results are listed in Table 2.

light resistance

The thermographic recording materials COMPARATIVE EXAMPLES 1 to 9 and the INVENTION EXAMPLES 1 to 6 are used in a SUNTEST CPS device marketed by HERAEUS Exposed to sunlight test. The thermographic recording materials be under ambient conditions through a glass filter, the infrared light with a wavelength over 700 nm and ultraviolet light having a wavelength below 310 nm, one of a low-pressure xenon lamp NXE 1500 originating Luminous flux of about 110 kLux exposed. The results are in Table 2 listed.

Table 2

The increase in the CIELAB b * value of the background image of prints after the 240 hours Sunlight test is clearly lower in the thermographic Recording materials of INVENTION EXAMPLES 1 to 6, which the non-chlorine-containing stabilizers STAB 03, 05, 07, 08 and 13 contained as the stabilizer-free thermographic recording material COMPARATIVE EXAMPLE 1, d. H. the tonal neutrality of the picture is during the sunlight test better maintained. The resistance the image tone of the image background of the thermographic recording materials of the INVENTION EXAMPLES 1 and 2, which contain the stabilizers STAB 13 and STAB 07, respectively, is noticeably worse than in the INVENTION EXAMPLES 3 to 6, the non-chlorine stabilizers STAB 03, STAB 05 and STAB 08, as evidenced by the change in the CIELAB a * value and CIELAB b * value.

This proves that thermographic Recording materials containing non-chlorinated 2- (2'-hydroxyphenyl) -benzotriazole derivatives (Stabilizers STAB 03, 05, 07 and 08) and non-chlorine-containing 2-hydroxybenzophenone derivatives Stabilizer STAB 13), better resistance the background image and in particular the background image tone against a simulated exposure to direct sunlight as thermographic recording materials containing the above stabilizers not included.

COMPARATIVE EXAMPLES 10 to 14 & the invention of the invention 7

The thermosensitive elements of the substantially light-insensitive monochrome monochrome thermographic recording materials COMPARATIVE EXAMPLES 10 to 14 and the inventive example 7 will be like for the INVENTION EXAMPLES 1 to 6 and COMPARATIVE EXAMPLES 1 to 9 described, with the difference that the used in Table 3 below and 3 minutes at 90 ° C instead of 3 minutes at 85 ° C are cured.

Table 3

The thermographic evaluation of substantially light-insensitive monochrome monochrome thermographic recording materials of the invention example 7 and COMPARATIVE EXAMPLES 10 to 14 becomes as for the INVENTION EXAMPLES 1 to 6 and COMPARATIVE EXAMPLES 1 to 9 described, with the difference that the thermographic recording materials also a 5 day BB test be subjected. In the BB test, the thermographic recording materials For 5 days under ambient conditions 1 meter directly under one 2000 W halogen lamp of type THS 3007 from Siefried Theimer GmbH, 6484 Birnstein, Germany. This light source generates UVA light (320-380 nm), UVB light (280-320 nm) and UVC light (below 280 nm). All results are in table 4 listed.

Table 4

From the results of the thermographic Evaluation of the thermographic recording materials of the COMPARATIVE EXAMPLES 10 to 14 and INVENTION EXAMPLE 12 are shown clearly that through Use of zinc oxide as a UV absorber in the protective layer unwanted yellowing of the picture, as can be seen from the noticeably higher CIELAB a * values of the Background from with the thermographic recording materials COMPARATIVE EXAMPLES 10 to 14 produced in comparison to the CIELAB a * value of the thermographic recording material of the invention example 7, and a weaker background tone resistance in 5 days BB test, in particular as far as the CIELAB a * value is concerned.

For this reason is by embedding zinc oxide, which is a known inorganic UV stabilizer, in the thermographic recording materials no resistance received against direct sunlight.

COMPARATIVE EXAMPLE 15 & INVENTIVE EXAMPLES 8 to 16

The heat-sensitive elements of the substantially light-insensitive black and white monosheet thermographic recording materials of INVENTION EXAMPLES 8 to 16 and COMPARATIVE EXAMPLE 15 are prepared as described for INVENTION EXAMPLES 1 to 6 and COMPARATIVE EXAMPLES 1 to 9, but with the difference that instead of T01 T02 is added to the heat-sensitive element 0.102 g / m ² R02 and the protective layers are used with the compositions given in Table 5 below.

Table 5

The thermographic evaluation of substantially light-insensitive monochrome monochrome thermographic recording materials of the INVENTION EXAMPLES 8 to 16 and COMPARATIVE EXAMPLE 15 will be as for the INVENTION EXAMPLES 1 to 6 and the COMPARATIVE EXAMPLES 1 to 9 described. The results are listed in Table 6.

The thermographic results of thermographic recording materials of the COMPARATIVE EXAMPLE 15 and the INVENTION EXAMPLES 8 to 16 confirm those with the thermographic recording materials of the INVENTION EXAMPLES 1 to 6 results obtained that after the 240-hour sunlight test determined increase of the CIELAB b * value of the image background of with thermographic stabilizers STAB 03, 05, 07 and 13 lower prints obtained is than with the stabilizer-free thermographic material obtained in COMPARATIVE EXAMPLE 15, d. H. the tonal neutrality of the picture is during the sunlight test better maintained.

Table 6

This evaluation proves that with the thermographic recording materials containing the non-chlorine-containing 2- (2'-hydroxyphenyl) benzotriazole derivatives (Stabilizers STAB 03, 05 and 07) and the non-chlorine-containing 2-hydroxybenzophenone derivatives Stabilizer STAB 13), better resistance of the image background and in particular the image tone against a simulated Exposure to direct sunlight is obtained as with the thermographic Recording materials that do not contain the above stabilizers.

INVENTIVE EXAMPLE 17

Stabilizer in both the heat sensitive Element as the protective layer

The thermosensitive elements of the substantially light-insensitive black and white monosheet thermographic recording materials of INVENTION EXAMPLE 17 are prepared as described for INVENTION EXAMPLES 1 to 6 and COMPARATIVE EXAMPLES 1 to 9, except that the thermosensitive element has the following composition: AgBeh 3.89 g / m ² BR 18 3.89 g / m ² STAB 03 0.15 g / m ² R01 0.855 g / m ² T02 0.219 g / m ² oil 0.144 g / m ² S01 0.094 g / m ² S02 0.085 g / m ² N100 0.401 g / m ²

On the thermosensitive element of the thermographic recording materials of INVENTION EXAMPLE 17, the following protective layer composition is then applied and cured at 85 ° C for 3 minutes: BR 182 1,844 g / m ² MICRODOL ^TM SUPER 0.184 g / m ² STAB 03 0.228 g / m ² oil 0.012 g / m ² N100 0.183 g / m ²

The thermographic evaluation of substantially light-insensitive monochrome monochrome thermographic recording materials of the CREATIVE COMPETITION 17 will be like for the INVENTION EXAMPLES 1 to 6 and the COMPARATIVE EXAMPLES 1 to 9 described. The results are listed in Table 7.

Table 7

By use of a stabilizer according to the invention in both the heat-sensitive Element as the protective layer of the thermographic recording material of the invention example 17 is the increase in the CIELAB b * value after a 5-day exposure with a 2000 W halogen lamp less pronounced than when the same stabilizer (STAB 03) is used only in the protective layer (see INVENTION EXAMPLE 12).

INVENTIVE EXAMPLES 18 to 26

The thermosensitive elements of the substantially light-insensitive monochrome monochrome thermographic recording materials of the INVENTION EXAMPLES 18 to 26 will be like for the INVENTION EXAMPLES 1 to 6 and COMPARATIVE EXAMPLES 1 to 9 described, but with the difference that for the heat-sensitive Element uses the compositions listed in Table 8 and the materials for 15 minutes at 85 ° C without coating with a protective layer hardened become.

Table 8

The thermographic evaluation is as for the INVENTION EXAMPLES 1 to 6 and COMPARATIVE EXAMPLES 1 to 9 described, however, with the difference that the printhead through a thin one intermediate material in contact with a sliding layer of a separable, 5 microns strong polyethylene terephthalate tape from the image-forming layer is held separately, the tape in turn with a Adhesive layer, a heat-resistant Layer and the sliding layer (friction protection layer) coated is and a total strength of 6 μm having.

The storage life tests are as for the INVENTION EXAMPLES 1 to 6 and the COMPARATIVE EXAMPLES 1 to 9 described and the image evaluation will be as for the INVENTION EXAMPLES 1 to 6 and COMPARATIVE EXAMPLE 1 are described. The Results are listed in Table 9.

Light Box Test

For the evaluation of the resistance against a re-exposure of the image background of the developed Image of prints, those with the thermographic recording materials of the INVENTION EXAMPLES 18 to 26 are made, fresh prints are 3 days on the white PVC window a specially built light box in one at a temperature of 30 ° C and a relative humidity (RH) of 85% adjusted VOTSCH climatic tester exposed. The test materials are only on a central, 550 mm long and 500 mm wide Area of the window arranged to ensure a uniform exposure.

The stainless steel lightbox is 650 mm long, 600 mm wide and 120 mm high and has a 610 mm long and 560 mm wide opening and a 10 mm wide and 5 mm deep edge around the opening, creating a platform for a 5 mm thick, 630 mm long and 580 mm wide plate is made of white PVC, the white PVC plate is in the same plane as the light box and light loss is prevented from the light box, except the loss of light through the white PVC plate out. In this light box 9 PLANILUX ^™ TLD 36W / 54 fluorescent lamps with a diameter of 27 mm are arranged in the length and equidistant from the two sides, the lamps being equidistant from one another and from the sides over the entire width of the light box and the top of the fluorescent tubes is 30 mm below the bottom of the white PVC plate and 35 mm below the materials to be tested.

Based on the CIELAB values L *, a * and b * of the background, according to spectrophotometric measurements determined according to ASTM standard E179-90 in an R (45/0) geometry with the evaluation according to ASTM standard E308-90, determine to what extent a material is suitable. The results are listed in Table 9.

Table 9

The measurements of the values a * and b * in the lightbox show an excellent image tone in the Image background, which is also reflected in the low increase in the values a * and b * compared to the values a * and b * of the fresh prints. This is especially the case with the thermographic recording materials of the INVENTION EXAMPLES 21, 22, 25 and 26.

INVENTIVE EXAMPLES 27 to 34

Stabilizer in both the heat sensitive Element as the protective layer

The thermosensitive elements of the substantially light-insensitive monochrome monochrome thermographic recording materials of the INVENTION EXAMPLES 27 to 34 correspond to the heat-sensitive Elements of the substantially light-insensitive black-and-white monochrome thermographic recording materials of the INVENTION EXAMPLES 19 to 26. The heat-sensitive Elements of the Thermographic Recording Materials of the INVENTION EXAMPLES 27 to 34 are then coated with a protective layer with the in Table 10 coated compositions and finally 3 Minutes at 85 ° C hardened.

Table 10

The thermographic evaluation of substantially light-insensitive monochrome monochrome thermographic recording materials of the INVENTION EXAMPLES 27 to 34 will be like for the INVENTIVE EXAMPLES 18 to 26 described. The results are in table 11 listed.

Table 11

The measurements of the values a * and b * in the lightbox for the thermographic recording materials of the INVENTION EXAMPLES 29 to 34 give even lower values a * and b * than for thermographic ones Recording materials of INVENTION EXAMPLES 21 to 26, whose thermosensitive Elements contain the same compositions, which indicates that by Application of a protective layer with 2.1 mol% STAB 07 an additional Improvement of the resistance of the image background is obtained. This improvement is special pronounced in the thermographic recording materials of the INVENTION EXAMPLES 30, 31, 32, 33 and 34, where b * values of 3.91, 4.12, 4.07, 3.86 and 3.44 are measured.

After taking note of the detailed described preferred embodiments The present invention will be apparent to those skilled in the art Modifications of the description according to the invention open, without from the invention, in the following claims deviate from the defined scope of protection.

Claims (11)

A substantially light-insensitive, thermographic, non-chlorine-containing stabilizer-containing black-and-white single-sheet recording material comprising a support and a heat-sensitive element, wherein the heat-sensitive element is a substantially light-insensitive organic silver salt A reducing agent therefor in thermally effective relationship thereto and a binder, characterized in that the non-chlorine-containing stabilizer is selected from the group consisting of 2- (2'-hydroxyphenyl) benzotriazole derivatives and 2-hydroxybenzophenone derivatives. Thermographic recording material according to claim 1, characterized in that the non-chlorine-containing 2- (2'-hydroxyphenyl) benzotriazole derivative contains a 2-hydroxybenzophenone group. Thermographic recording material according to Claim 1, characterized in that the non-chlorine-containing 3- (2'-hydroxyphenyl) -benzotriazole derivative is selected from the group consisting of 2- [2'-hydroxy-3 ', 5' - (di-t-) butyl) -phenyl] -benzotriazole, 2- [2'-hydroxy-3 ', 5'-di (α, α-dimethylbenzyl) -phenyl] -benzotriazole, 2,2-methylene-bis- [5- (2H -benztriazol-1-yl) -3- (1 '', 1 '', 3 '', 3 '' - tetramethylbutyl) -phenol], 2,2-methylene-bis- [5- (2H-benztriazole-1 -yl) -3- (1 '', 1 '', 3 '', 3 '' - tetramethylbutyl) -phenol],

and

is selected. Thermographic recording material according to a the claims 1 to 3, characterized in that the reducing agent a 1,2-dihydroxybenzene derivative. Thermographic recording material according to a the preceding claims, characterized in that the Binder is a first polymer having active hydrogen atoms, of which at least a part reacts with a first polyisocyanate Has. Thermographic recording material according to a the preceding claims, characterized in that the essentially light-insensitive organic silver salt, a silver salt an aliphatic carboxylic acid with at least 12 carbon atoms. Thermographic recording material according to a the preceding claims, characterized in that the thermosensitive Element is further coated with a protective layer. Thermographic recording material according to claim 7, characterized in that the protection layer contains a second polymer having active hydrogen atoms, at least part of which has reacted with a second polyisocyanate. A marked by the following steps Recording method: (i) arranging an outer layer of a thermographic A recording material according to any one of the preceding claims in Near one Heat source, (ii) imagewise of the thermographic recording material from the heat source supplied heat for producing an image, wherein the recording material in nearby the heat source is maintained, and (iii) removing the thermographic Recording material from the heat source. Recording method according to claim 9, characterized characterized in that Heat source a thin-film thermal head is. Use of a non-chlorine-containing stabilizer from the group consisting of 2- (2'-hydroxyphenyl) benzotriazole derivatives and 2-hydroxybenzophenone derivatives as a stabilizer against direct Sunlight in a substantially light-insensitive thermographic Black and white monosheet recording material with a carrier and a heat-sensitive one Element, being the heat-sensitive Element a substantially light-insensitive organic silver salt, a reducing agent for it in a thermally effective relationship thereto and a binder.