DE60310182T2 - Stabilizers for use in thermographic recording materials which are substantially light-insensitive - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The The present invention relates to stabilizers for use in essentially light-insensitive thermographic recording materials.

GENERAL STATE OF THE ART

The Thermography is a heating step comprehensive imaging process and thus also includes the photothermography in which the image forming process involves an imagewise exposure process and a direct thermal process, wherein the imaging process a pictorial heating step includes. Direct thermal printing becomes a visible pattern by imagewise heating of a Produced recording material.

EP-A-0 218 385 discloses a heat-developable photosensitive material comprising at least one light-sensitive silver halide-containing layer on a support and further a compound corresponding to the following general formula (I) X - (- (J) _m -F) _n (I) where X is the rest of the development retarder, J is a divalent bridge member and F is an immobilizing group capable of reducing the diffusivity of the compound of formula (I) or its silver salt or silver complex during heat generation, m is 0 or 1 and n is an integer from 1 to 3. EP-A-0 218 385 discloses the following 2-mercaptobenzothiazole compounds

EP-A-0 256 820 discloses a heat-developable photosensitive material consisting of a support and at least one layer of photosensitive silver halide-containing photographic structural layers thereon, such a photographic structural layer having a compound corresponding to formula (1) X ₁ -L ₁ -A formula (1) wherein X _{1 is} a residual group of a photographic retarder, L _{1 is} a single bond or a divalent group, and A is a hydrogen atom, an amino group, a hydroxyl group, a carboxyl group or its salt, a sulfo group or its salt or a sulfine group or its salt, and a compound corresponding to the general formula (2) X ₂ -L ₂ -B formula (2) wherein X _{2 is} a residual group of a photographic retarder, L _{2 is} a divalent group and B is a ballast group. EP-A-0 256 820 discloses the following 2-mercaptobenzothiazole compounds

in der R¹ ein Wasserstoffatom, eine Alkylgruppe mit bis zu 6 Kohlenstoffatomen, ein Halogenatom, eine Hydroxylgruppe, eine Alkoxygruppe oder Substituenten, die zusammen einen kondensierten Benzolring bilden, darstellt, und einer Verbindung der folgenden Formel (II) enthält

in der R² eine Gruppe bedeutet, die während der Wärmeentwicklung des Materials abgespalten werden kann, und R³ ein Wasserstoffatom, ein Halogenatom, eine Alkylgruppe mit bis zu 4 Kohlenstoffatomen, eine Alkoxygruppe, eine Carboxylgruppe, eine Carbalkoxygruppe, eine Carbonamidgruppe oder eine Sulfonamidgruppe darstellt. In EP-A 0 295 507 wird ferner offenbart, dass das lichtempfindliche Blattmaterial zusätzlich zumindest eine Verbindung gemäß einer der nachstehenden Formeln (III) oder (IV) enthält

in der Q die zum Vervollständigen einer heterocyclischen Gruppe mit einem 5- oder 6-gliedrigen heterocyclischen Ring benötigte Gruppe und X eine Carbonsäuregruppe oder Sulfonsäuregruppe oder einen eine Carbonsäuregruppe oder Sulfonsäuregruppe enthaltenden Rest bedeutet, und

in der R⁴ ein Wasserstoffatom, eine Alkylgruppe mit bis zu 18 Kohlenstoffatomen, eine Alkoxygruppe oder ein Halogenatom, R⁵ ein Wasserstoffatom oder eine Alkylgruppe mit bis zu 18 Kohlenstoffatomen, R⁶ ein Wasserstoffatom oder eine Alkylgruppe mit bis zu 3 Kohlenstoffatomen und n 0, 1 oder 2 bedeutet. In EP-A 0 295 507 wird ferner

als zweckmäßige Verbindung offenbart.EP-A 0 295 507 discloses a process for producing color images after the photographic dye diffusion process, wherein a first photosensitive sheet material is imagewise exposed, the first photosensitive sheet material and / or a second non-photosensitive sheet material is wetted with an aqueous liquid and the two sheet materials are heated together to 50 ° C to 100 ° C with their coated surfaces first in contact with each other and then separated, the first sheet material on a support at least one light-sensitive silver halide emulsion layer and at least one diffusion-resistant coloring compound which is capable of imagewise decomposing during the development process, thereby releasing a diffusible dye, and wherein the second sheet material contains a salt of a strong organic acid and a weak acid, the first sheet m aterially a combination of a compound of the following formula (I)

wherein R ^{1 represents} a hydrogen atom, an alkyl group having up to 6 carbon atoms, a halogen atom, a hydroxyl group, an alkoxy group or substituents which together form a fused benzene ring, and a compound of the following formula (II)

wherein R ^{2 represents} a group which can be split off during the heat development of the material, and R ^{3 represents} a hydrogen atom, a halogen atom, an alkyl group having up to 4 carbon atoms, an alkoxy group, a carboxyl group, a carbalkoxy group, a carbonamide group or a sulfonamide group represents. It is further disclosed in EP-A 0 295 507 that the photosensitive sheet material additionally contains at least one compound according to any of the following formulas (III) or (IV)

wherein Q represents the group required to complete a heterocyclic group having a 5- or 6-membered heterocyclic ring, and X represents a carboxylic acid group or sulfonic acid group or a group containing a carboxylic acid group or sulfonic acid group, and

R ^{4 is} a hydrogen atom, an alkyl group having up to 18 carbon atoms, an alkoxy group or a halogen atom, R ^{5 is} a hydrogen atom or an alkyl group having up to 18 carbon atoms, R ^{6 is} a hydrogen atom or an alkyl group having up to 3 carbon atoms and n is 0, 1 or 2 means. In EP-A 0 295 507 is further

disclosed as a suitable compound.

EP-A-0 838 722 discloses a photothermographic material containing the following ingredients: (a) a reducible source of silver, (b) a photocatalyst, (c) a reducing agent, (d) a binder, and (e) at least one compound of the following general Formula (I) XL ₁ -D wherein D is an electron donating group of atoms, with the proviso that when D is a hydrazine group which is not part of a semicarbazide group, no carbon atom directly attached to a nitrogen atom of the hydrazine group is substituted by an oxo group, X is a group containing the Adsorbing to silver halide and L _{1 is} a valence bond or a linking group. In EP-A 0 838 722, the following 2-mercaptobenzothiazole compound is disclosed on page 15 at number 24

in der Z₁ eine Gruppe von zur Bildung eines 5-gliedrigen oder 6-gliedrigen stickstoffhaltigen Heterozyklus benötigten Atomen bedeutet, D und D' jeweils eine Gruppe von zur Bildung eines acyclischen oder cyclischen Säureringes benötigten Atomen bedeuten, R₁ eine Alkylgruppe bedeutet, L₁, L₂, L₃, L₄, L₅, L₆, L₇, L₈, L₉ und L₁₀ jeweils eine Methingruppe bedeuten und einen Ring mit einer anderen Methingruppe oder einen Ring mit einem Auxochrom bilden können, die Buchstaben n1, n2, n3, n4 und n5 jeweils 0 oder 1 bedeuten, M₁ ein die elektrische Ladung neutralisierendes Gegenion bedeutet und Buchstabe m1 eine zum Neutralisieren einer elektrischen Ladung in einem Molekül benötigte ganze Zahl, einschließlich 0, bedeutet. In US 5 922 529 werden ferner die nachstehenden 2-Mercaptobenzthiazol-Verbindungen gemäß Formel (I) offenbart

In US 5,922,529 there is disclosed a photothermographic material containing on at least one surface of a support a binder, an organic silver salt, a silver ion reducing agent, and radiation-sensitive silver halide grains, wherein a radiation-sensitive layer containing the radiation-sensitive silver halide grains further comprises a compound of the formula (I) and a compound of the Formula (II) and the radiation-sensitive layer has an absorbance of 0.15 to 1.0 at an exposure wavelength, RS (M) _n (I) wherein R is an aliphatic hydrocarbon atom, an aryl group or a heterocyclic group, M is a hydrogen atom or a cation and the letter n is a number chosen to neutralize the molecule,

in which Z _{1 represents} a group of atoms required to form a 5-membered or 6-membered nitrogen-containing heterocycle, D and D 'each represent a group of atoms needed to form an acyclic or cyclic acid ring, R _{1 represents} an alkyl group, L ₁ , L ₂ , L ₃ , L ₄ , L ₅ , L ₆ , L ₇ , L ₈ , L ₉ and L ₁₀ each may be a methine group and may form a ring with another methine group or a ring with an auxochrome, the letters n1 , n2, n3, n4 and n5 are each 0 or 1, M _{1 is} an electric charge neutralizing counter ion, and letter m1 means an integer needed to neutralize an electric charge in a molecule, including 0. In US 5,922,529 Further, the following 2-mercaptobenzothiazole compounds according to formula (I) are disclosed

In EP-A 0 218 385, EP-A 0 256 820, EP-A 0 295 507, EP-A 0 838 722 and US 5,922,529 each discloses the use of various 2-mercaptobenzothiazole compounds in photothermographic recording materials. However, the technology of substantially non-photosensitive thermographic materials containing substantially light-insensitive organic silver salts differs substantially from the technology of photothermographic materials containing substantially light-insensitive organic silver salts, despite the fact that the formation of the image in both cases underlies the reduction of organic silver salts. However, this similarity is only superficial and masks the fact that in both cases a very different type of catalyzing these reduction substances, ie in photothermographic recording materials is an imagewise exposure of photo-addressable, heat-developable, radiation-sensitive silver halide-containing elements, while thermographic recording materials are an image-wise heating of heat-sensitive elements which do not contain radiation-sensitive silver halide. This difference in technology is also clearly manifested in the nature of the components used in the two types of materials, the most notable being the absence of radiation-sensitive silver halide and spectral sensitizer in substantially non-photosensitive thermographic recording materials. Also different are the nature of the reducing agents used, wherein in substantially light-insensitive thermographic recording materials stronger reducing agents are used, the nature of the stabilizers, the type of toning agents, etc. Furthermore, the heat development processes themselves are also significantly different in that the whole material in the case of photothermographic recording materials are heated at temperatures of less than 150 ° C within seconds (eg 10 seconds), while in the case of substantially light-insensitive thermographic recording materials the materials are imagewise heated at much higher temperatures within ms time periods (eg 3-20 ms) , In addition, the organic silver salts are present in the heat development of substantially light-insensitive thermographic recording materials in their liquid-crystalline phases, while in the heat-development step in photothermographic recording materials is not the case, even not using the same organic silver salts. Due to the very short heating times, obtaining a neutral image tone is an important problem for substantially non-photothermic thermographic recording materials, while this is much less problematic for photothermographic recording materials due to the much longer heating times.

EP-A-0 713 133 discloses a thermal imaging system comprising: (i) a donor element having a donor layer coated on a support which contains a binder and a thermally transferable reducing agent capable of reducing a silver source to metal silver; (ii) a receiving element having a receiving layer coated on a support which has a silver source which can be reduced under the influence of heat in the presence of a reducing agent 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 acids and phthalic acid derivatives.

EP-A-0 901 040 discloses a substantially light-insensitive single-sheet recording material comprising a support and a thermosensitive element comprising a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermally effective relationship thereto and a binder, characterized in that the thermosensitive element further contains an -SA group-substituted, unsaturated carbocyclic or heterocyclic stabilizer compound, wherein A represents a hydrogen atom, a counter ion for balancing the negative charge of the thiolate group or a symmetrical or asymmetric disulfide-forming group, and the recording material copies with a as the quotient of the fraction (2.5 - 0.1) / (E _2.5 - E _0.1 ) gives a graded number value of more than 2.3, where E _{2.5 is} the one in a dot area of 87 μm × 87 μm of the imaging layer applied energy is in joules that gives an optical density value of 2.5, and E _{0.1 is} the energy in Joules applied in a dot area of the imaging layer material which gives an optical density value of 0.1. EP-A-0 901 040 discloses the following 2-mercaptobenzothiazole compound

In WO 94/16361 is a multilayer heat-sensitive material with discloses a color-forming layer containing the following substances: a color-forming amount of a finely divided, solid, colorless, in a carrier composition distributed noble metal salt or iron salt of an organic acid, a color-developing Amount of a cyclic or aromatic organic reducing agent, this is a color-forming reaction at thermoprinting and printing temperatures to deal with the noble metal or iron salt, and a tinting agent, characterized in that (a) the carrier composition substantially water-soluble polymeric carrier and a dispersant for the noble metal or iron salt contains and (b) the material a Protective cover layer for contains the color-forming layer. Further, WO 94/16361 discloses that suitable antifoggants Well-known photographic antifoggants are, such as Mercaptobenzotriazole, chromate, oxalate, citrate, carbonate, benzotriazole (BZT), 5-methylbenzotriazole, 5,6-dimethylbenzotriazole, 5-bromobenzotriazole, 5-chlorobenzotriazole, 5-nitrobenzotriazole, 4-nitro-6-chlorobenzotriazole, 5-nitro-6-chlorobenz-triazole, 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'-dimethylpyrimidine, 1-ethyl-2-mercapto-5-amine-1,3,4-triazole, 1-ethyl-5-mercapto-1,2,3,4-tetrazole, 2,5-dimercapto-1,3,4-thiodiazole, 2-mercapto-5-aminthiodiazole, dimethyldithiocarbamate and diethyldithiocarbamate.

WO 96/10213 discloses a thermographic imaging member comprising a substrate at least one surface of which is coated with a thermographic imaging system comprising at least one layer, the light-insensitive organic silver salt, a silver ion reducing agent, a binder, a toner and containing a radiation in the wavelength range between 750 and 1100 nm absorbing dye, wherein the at least one light-insensitive organic silver salt-containing layer gives an image density of more than about 1.0, when within 0.20 to 200 ms with an energy between 0, 10 and 2.0 Joule / cm ^{2 is} exposed to the above-mentioned radiation. Although no stabilizer against the action of light is described in WO 96/10213, mention is made of the possible use of benzotriazole in the thermographic imaging element, but only by way of example.

Thereby, the image-forming components both before and after image formation in the substantially light-insensitive thermographic recording materials are included, is undesirable Imaging both during the storage of the recording materials prior to their use in a printing cycle than when illuminating copies in viewing devices, e.g. while an examination of the copy of a radiologist, to prevent. Furthermore, such stabilization is without adverse effect on the picture quality and in particular to realize the picture tone. There are currently thermographic Printer with ever higher Throughput services marketed the thermographic recording materials require at such high throughputs without adverse effect on the picture quality are stable. There is thus a need for stabilizers which meet these requirements.

TASKS OF PRESENT INVENTION

task The present invention therefore provides stabilizers, the without adverse effect on the image tone in substantially light-insensitive thermographic recording materials for use in thermographic High-throughput printers can be used.

Further Objects and advantages of the present invention will become apparent from the the following description.

SHORT PRESENTATION THE PRESENT INVENTION

you has unexpectedly found that specific types of 2-mercaptobenzothiazole compounds without adversely affecting the image tone, as evidenced by the measurement CIELAB values a * and b * gives a useful stabilization in substantially light-insensitive thermographic recording materials for Use in thermographic printers with high throughput. The CIELAB values L *, a * and b * become spectrophotometric Measurements according to the ASTM standard E179-90 in a R (45/0) geometry with an evaluation according to the ASTM standard E308-90 received.

in der R¹, R², R³ und R⁴ unabhängig voneinander ein Wasserstoffatom, eine gegebenenfalls substituierte Alkylgruppe, eine gegebenenfalls substituierte Arylgruppe, eine Alkoxygruppe, eine Estergruppe, eine Carbamatgruppe, eine Carbonatgruppe, eine SO₂R⁵-Gruppe, eine -NR⁶R⁷-Gruppe, eine Cyangruppe, eine Acylgruppe, ein Halogenatom, eine gegebenenfalls alkylsubstituierte oder alkoxysubstituierte -SO₂NH-Phenylgruppe, eine Perfluoralkylgruppe, eine -CONHR⁸-Gruppe, eine -NHOCR⁹-Gruppe, eine -OCOOR¹⁰-Gruppe oder eine -NHCOOR¹¹-Gruppe bedeuten, R⁵, R⁹, R¹⁰ und R¹¹ unabhängig voneinander eine gegebenenfalls substituierte Alkylgruppe oder eine Arylgruppe bedeuten, R⁶, R⁷ und R⁸ unabhängig voneinander ein Wasserstoffatom, eine gegebenenfalls substituierte Alkylgruppe oder eine Acylgruppe bedeuten und R¹ und R² zusammen, R² und R³ zusammen und R³ und R⁴ zusammen unabhängig voneinander die zur Bildung eines carbocyclischen, heteroaromatischen oder heterocyclischen Ringes benötigten Atome bedeuten können, mit der Maßgabe, dass R¹, R², R³ und/oder R⁴ ein Wasserstoffatom bedeutet bzw. bedeuten.The objects of the present invention are achieved by a substantially light-insensitive monochrome black-and-white single-sheet recording material having a support and a heat-sensitive element, the heat-sensitive element being a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal effective relation thereto, at least one polycarboxylic acid and / or a polycarboxylic acid Polycarboxylic anhydride in a molar ratio of at least 15, based on the total amount of all organic silver salts and in a thermally effective relationship thereto, a binder and at least one 2-mercaptobenzothiazole compound of the following formula (I)

in which R ¹ , R ² , R ³ and R ⁴ independently of one another represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted aryl group, an alkoxy group, an ester group, a carbamate group, a carbonate group, an SO ₂ R ⁵ group, a NR ⁶ R ⁷ group, a cyano group, an acyl group, a halogen atom, an optionally alkyl-substituted or alkoxy-substituted -SO ₂ NH-phenyl group, a perfluoroalkyl group, a -CONHR ⁸ group, a -NHOCR ⁹ group, an -OCOOR ¹⁰ - group or an -NHCOOR mean ¹¹ group, R ^5, R ^9, R ¹⁰ and R ¹¹ independently represent an optionally substituted alkyl group or an aryl group, R ^6, R ⁷ and R ^{8 are} independently a hydrogen atom, an optionally substituted alkyl group or an acyl group and R ¹ and R ² together, R ² and R ³ together and R ³ and R ⁴ together independently represent the formation of a carbocyclic, heteroaromatic or heterocy may mean atoms required with the proviso that R ¹ , R ² , R ³ and / or R ^{4 represents} or denote a hydrogen atom.

preferred embodiments The present invention will become apparent in the detailed description of the present invention Invention disclosed.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

definitions

Under The term "alkyl" is understood to mean all potential Variants for any number of carbon atoms in the alkyl group, i. for three carbon atoms: n-propyl and isopropyl, for four carbon atoms: n-butyl, isobutyl and t-butyl, for five carbon atoms: n-pentyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl and 2-methylbutyl etc.

Of the Term "acyl group" in the description of the present invention means a - (C = O) -aryl group or a - (C = O) alkyl group.

The CIELAB values L *, a * and b * are in ASTM standard E179-90 in one R (45/0) geometry defined. Their evaluation is based on the ASTM standard E308-90.

"Essential insensitive to light "means not intentionally sensitized to light.

thermosensitive element

Of the as used in the present invention, term "heat-sensitive Element "is that Element containing all the image-forming components. The heat-sensitive according to the invention Element contains one or a plurality of substantially light-insensitive organic silver salts, one or more reducing agents for this in thermal effective Relationship to it and a binder. The element can be made of a layer system exist in which the above-mentioned agents in different Layers can be dispersed however, must the substantially light-insensitive organic silver salts in reactive Relative to the reducing agents, i. during the Heat development process The reducing agent must be present in such a way that it is in the particles the substantially light-insensitive organic silver salt over-diffuse and that with it the reduction to silver can take place. at Such materials may be one or more Substantially light-insensitive organic silver salts and / or a or more organic reducing agents therefor in heat-sensitive microcapsules encapsulate as described in EP-A 0 736 799.

2-mercaptobenzothiazole compounds

in der R¹, R², R³ und R⁴ unabhängig voneinander ein Wasserstoffatom, eine gegebenenfalls substituierte Alkylgruppe, eine gegebenenfalls substituierte Arylgruppe, eine Alkoxygruppe, eine Estergruppe, eine Carbamatgruppe, eine Carbonatgruppe, eine SO₂R⁵-Gruppe, eine -NR⁶R⁷-Gruppe, eine Cyangruppe, eine Acylgruppe, ein Halogenatom, eine gegebenenfalls alkylsubstituierte oder alkoxysubstituierte -SO₂NH-Phenylgruppe, eine Perfluoralkylgruppe, eine -CONHR⁸-Gruppe, eine -NHOCR⁹-Gruppe, eine -OCOOR¹⁰-Gruppe oder eine -NHCOOR¹¹-Gruppe bedeuten, R⁵, R⁹, R¹⁰ und R¹¹ unabhängig voneinander eine gegebenenfalls substituierte Alkylgruppe oder eine Arylgruppe bedeuten, R⁶, R⁷ und R⁸ unabhängig voneinander ein Wasserstoffatom, eine gegebenenfalls substituierte Alkylgruppe oder eine Acylgruppe bedeuten und R¹ und R² zusammen, R² und R³ zusammen und R³ und R⁴ zusammen unabhängig voneinander die zur Bildung eines carbocyclischen, heteroaromatischen oder heterocyclischen Ringes benötigten Atome bedeuten können, mit der Maßgabe, dass R¹, R², R³ und/oder R⁴ ein Wasserstoffatom bedeutet bzw. bedeuten. Bevorzugte eventuelle Substituenten für die gegebenenfalls substituierte Alkylgruppe und die gegebenenfalls substituierte Arylgruppe sind Halogenatome, Gruppen, die einen 2-Mercaptobenzthiazolanteil enthalten, und eine Alkylgruppe, eine Alkoxygruppe, eine Mercaptogruppe und eine Hydroxylgruppe.The objects of the invention are achieved by a substantially light-insensitive black and white single-sheet thermographic recording material according to the invention, which can contain at least one 2-mercaptobenzothiazole compound of the formula (I)

in which R ¹ , R ² , R ³ and R ⁴ independently of one another represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted aryl group, an alkoxy group, an ester group, a carbamate group, a carbonate group, an SO ₂ R ⁵ group, a NR ⁶ R ⁷ group, a cyano group, an acyl group, a halogen atom, an optionally alkyl-substituted or alkoxy-substituted -SO ₂ NH-phenyl group, a perfluoroalkyl group, a -CONHR ⁸ group, a -NHOCR ⁹ group, an -OCOOR ¹⁰ - group or an -NHCOOR mean ¹¹ group, R ^5, R ^9, R ¹⁰ and R ¹¹ independently represent an optionally substituted alkyl group or an aryl group, R ^6, R ⁷ and R ^{8 are} independently a hydrogen atom, an optionally substituted alkyl group or an acyl group and R ¹ and R ² together, R ² and R ³ together and R ³ and R ⁴ together independently represent the formation of a carbocyclic, heteroaromatic or heterocy may mean atoms required with the proviso that R ¹ , R ² , R ³ and / or R ^{4 represents} or denote a hydrogen atom. Preferred optional substituents for the optionally substituted alkyl group and the optionally substituted aryl group are halogen atoms, groups containing a 2-mercaptobenzothiazole moiety, and an alkyl group, an alkoxy group, a mercapto group and a hydroxyl group.

To a first embodiment of the invention essential light-insensitive monochrome monochrome thermographic recording material the at least one 2-mercaptobenzothiazole compound of the formula (I) an alkyl group, an aryl group, an alkoxy group, substituted a cyano group or an acyl group or a halogen atom 2-Mercaptobenzthiazolverbindung.

According to a second embodiment of the substantially light-insensitive black and white monosheet thermographic recording material according to the invention, the at least one stabilizer corresponds to one of the following formulas

According to a third embodiment of the substantially light-insensitive black and white monosheet thermographic recording material according to the invention, the at least one stabilizer corresponds to one of the following formulas

The 2-mercaptobenzothiazole compounds according to the invention of the formula (I) according to the experts known and in reference works such as Houben-Weyl discussed Standard techniques from organic chemistry using commercial Starting materials are produced.

In the table below, suitable 2-mercaptobenzothiazole compounds (MBT compounds) are listed according to the invention:

Organic silver salt

To a fourth embodiment of the invention essential light-insensitive monochrome monochrome thermographic recording material the organic silver salts no organic double salts, the one Silver cation in combination with a second cation, e.g. Magnesium- or iron ions.

To a fifth embodiment of the invention essential light-insensitive monochrome monochrome thermographic recording material at least one of the organic silver salts is a substantially light-insensitive Silver salt of an organic carboxylic acid.

In a sixth embodiment of the substantially light-insensitive monochrome black-and-white single-sheet recording material of the present invention, at least one of the organic silver is salts a substantially light-insensitive silver salt of an aliphatic carboxylic acid known as fatty acid in which the aliphatic carbon chain preferably contains at least 12 carbon atoms, eg silver laurate, silver palmitate, silver stearate, silver hydroxystearate, silver oleate and silver behenate, these silver salts being also referred to as "silver soaps". Other silver salts of an organic carboxylic acid as described in GB-P 1 439 478, for example silver benzoate, are also suitable for the preparation of a heat-developable silver image. Combinations of various silver salts of an organic carboxylic acid are also suitable for use in the present invention as described in EP-A 964 300.

Organic silver salts can be dispersed by standard dispersion techniques. In this case, for example, ball mills, bead mills, microfluidizers ^®, ultrasonic apparatuses, rotor stator mixers etc. have been found to be usable. Mixtures of dispersions of organic silver salts prepared by various techniques, for example mixtures of coarser and finer ground dispersions of organic silver salts, are also suitable for achieving the desired thermographic properties.

reducing agent

To a seventh embodiment of the thermographic according to the invention Black and white recording material the reducing agent is an organic compound that is at least contains an active, bonded to O, N or C hydrogen atom, such as this is the case with aromatic di- and trihydroxy compounds. Preference is given to 1,2-dihydroxybenzene derivatives, such as catechol, 3- (3,4-Dihydroxyphenyl) propionic acid, 1,2-dihydroxybenzoic acid, gallic acid and Gallussäureester, e.g. Methyl gallate, ethyl gallate, propyl gallate, tannic acid and 3,4-dihydroxybenzoic, in particular those described in EP-A 0 692 733 and EP-A 0 903 625 to be favoured.

It is also possible to use combinations of reducing agents which, when heated, become participants in the reduction reaction of the at least one substantially light-insensitive organic silver salt. Useful combinations include, for example, combinations of sterically hindered phenols with sulfonyl hydrazide reducing agents, as described in EP-A-0 022 931 US 5,464,738 , Trityl hydrazides and formylphenyl hydrazides, as in US 5,496,695 described trityl hydrazides and formylphenyl hydrazides with various auxiliary reducing agents as described in US 5,545,505 . US 5,545,507 and US 5 558 983 , Acrylonitrile compounds as described in US 5,545,515 and US 5 635 339 , and 2-substituted malondialdehyde compounds as described in U.S. Pat US 5,654,130 ,

binder the heat-sensitive Elements

When film-forming binder for the heat sensitive Element are all kinds of natural, modified natural or synthetic resins or mixtures of such resins in which the organic silver salt (s) either in aqueous Media or solvent media is homogeneously dispersible, e.g. Cellulose derivatives, starch ethers, Gallactomannan, polymers derived from α, β-ethylenically unsaturated Compounds, such as polyvinyl chloride, postchlorinated 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 made from polyvinyl alcohol as starting material, in which only part of the repeating Optionally reacted with an aldehyde, are prepared, preferably polyvinyl butyral, copolymers Acrylonitrile and acrylamide, polyacrylates, polymethacrylates, 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, polysaccharides and water-soluble cellulose derivatives. A preferred water-soluble Binders for use in the thermographic recording materials according to the invention is gelatin.

The weight ratio the binder to the organic silver salt is preferably between 0.2 and 7 and the strength the heat-sensitive Elements preferably between 5 and 50 microns. Preference is given to binders without additives, such as certain antioxidants (e.g., 2,6-di-tert-butyl-4-methylphenol), or foreign substances that are the thermographic properties of the thermographic Recording materials in which they are used, affect.

tint

To an eighth embodiment of the thermographic according to the invention Black White-sheet recording material contains the heat sensitive Element a tinting agent, by a neutral black image tone in the upper density zones and neutral gray in the lower density zones.

According to a ninth embodiment of the monochrome black-and-white thermographic recording material according to the present invention, the thermosensitive element further contains a tinting agent selected from the group consisting of phthalimides, phthalazinones, benzoxazinediones and naphthoxazinediones, for example those represented by the general formulas U.S. 4,082,901 corresponding phthalimides and phthalazinones, which are in US 3,074,809 US Pat. No. 3,446,648 and US Pat US Pat. No. 3,844,797 mentioned toning agent and the in GB 1 439 478 . US 3,951,660 and US Pat. No. 5,599,647 benzoxazine dione or naphthoxazine dione type heterocyclic toner compounds described.

To a tenth embodiment of the invention essential The light-insensitive black and white monosheet thermographic recording material contains the essential light-insensitive thermographic material is a heat-sensitive Element containing one or more toning agents from the group consisting of phthalazinone, benzo [e] - [1,3] -oxazine-2,4-dione, 7-Methylbenzo [e] - [1,3] -oxazine-2,4-dione, 7-methoxybenzo [e] - [1,3] -oxazine-2,4-dione and 7- (ethyl carbonate) benzo [e] - [1,3] oxazine-2,4-dione.

Auxiliary antifoggants

To an eleventh embodiment of the thermographic according to the invention Black White-sheet recording material contains the thermographic recording material further comprises an auxiliary fog-inhibiting agent, by improving the shelf life and reducing it from fogging.

To a twelfth embodiment of the thermographic according to the invention Black White-sheet recording material contains the thermographic recording material further comprises a fog-proofing agent from the group consisting of benzotriazole, substituted benzotriazoles and aromatic polycarboxylic acids, like orthophthalic acid, 3-nitrophthalic acid, tetrachlorophthalic acid, mellitic Pyromellitic acid and trimellitic acid, and their anhydrides.

To a thirteenth embodiment of the thermographic according to the invention Black White-sheet recording material contains the heat sensitive Element further an optionally substituted benzotriazole.

Polycarboxylic acids and polycarboxylic

To a fourteenth embodiment of the thermographic according to the invention Black White-sheet recording material may be the polycarboxylic acid an aliphatic (saturated or unsaturated aliphatic and also cycloaliphatic) polycarboxylic acid or an aromatic polycarboxylic acid be, these acids be substituted and in anhydride form or partially esterified Form, provided that that contain at least two free carboxylic acids or in the Heat recording step available.

Surfactants and dispersant

surfactants and dispersants facilitate the dispersion of ingredients, which are not soluble in the dispersion medium used. The invention used Substantially light-insensitive thermographic material can be 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 Powder, for example, finely divided non-metallic inorganic Powder like silica.

carrier

According to a fifteenth embodiment of the substantially light-insensitive black and white monosheet thermographic recording material of the present invention, the support is translucent or translucent, and is preferably a thin flexible support sheet of transparent resin, eg, egg cellulose ester, eg cellulose triacetate, polypropylene, polycarbonate or polyester, eg polyethylene terephthalate. The backing may be in the form of a sheet, ribbon or web and, if necessary, subbed to improve adhesion to the heat-sensitive element applied thereon. The support can be dyed or pigmented to provide the image with a translucent colored background.

protective layer

To a sixteenth embodiment of the invention essential light-insensitive monochrome monochrome thermographic recording material the heat sensitive Element coated with a protective layer. The protective layer protects that thermosensitive Element usually from humidity and surface damage by scratching etc. and prevents direct contact from printheads or Heat sources with the recording layers. On protective layers for heat-sensitive Elements that come into contact with a heating source and under pressure brought past it Need to become, 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. A sliding layer, the outermost layer is, can be solved from one Lubricant and / or a particulate material, such as e.g. Talc particles, consist of, optionally, the outer layer protrude. examples for suitable lubricants are surfactants, liquid lubricants, solid lubricants or mixtures thereof with or without polymeric Binder.

coating techniques

Of the Application of any layer of the inventively used substantially light-insensitive thermographic Material can be made 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, USA. For coating one can watery Media or solvent media use, in which case dried, partially dried or undried Layers are coated.

thermographic processing

The thermographic image formation takes place by imagewise exposure 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 a Nd: YAG laser or other infrared laser, one essential light-insensitive thermographic material, preferably contains an infrared absorbing compound, or by 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 operating temperature of conventional thermal printheads is between 300 and 400 ° C and the heating time per pixel may be 1.0 ms or less, wherein the pressure contact of the thermal printhead with the recording material, for example, between 200 and 1000 g / running cm, ie at a Contact area (grip area) between 200 and 300 microns, a pressure between 5,000 and 50,000 g / cm ^{2 is} applied to ensure good heat transfer.

To the Prevent from direct contact of the thermal printheads with the at the same Side of the vehicle like the heat sensitive Element applied outer layer, at least if this outer layer is not a protective layer, can be the imagewise heating of the recording material with the thermal printheads through a resinous sheet in contact therewith but removable or Harzbahn of the (the) during the heating no recording material can be transferred made become.

The Control of the heating elements can be power modulated or at constant Power pulse length modulated 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. In EP-A 622 217 a method for producing a Image using a direct thermal imaging element discloses improvements in halftone reproduction become.

For the imagewise warming of the Recording material is also suitable embedded in the material electrical resistance band. The imagewise or patternwise heating of the Recording material can also be modulated by a pixel-by-pixel Ultrasound treatment be made.

industrial application

The thermographic imaging can be used for the generation of both Supervision copies and transparencies are used, in particular in medical diagnostics, when working with a viewing device exam techniques Black-and-white transparency find widespread application.

The The following comparative and inventive examples illustrate the present invention. The percentages and ratios in these examples are in weight, unless otherwise stated is.

Adhesive layers on the emulsified Support page:

Adhesive layer no. 1 has the following composition

Adhesive layer no. 2 has the following composition

• BL5HP = S-LEC BL5HP, ein Polyvinylbutyral von SEKISUI,
• Öl = BAYSILON, ein Silikonöl von BAYER,
• VL = DESMODUR VL, ein 4,4'-Diisocyanatdiphenylmethan von BAYER,

Ingredients of the heat-sensitive element other than the above-mentioned ingredients:

• BL5HP = S-LEC BL5HP, a polyvinyl butyral from SEKISUI,
• Oil = BAYSILON, a silicone oil from BAYER,
• VL = DESMODUR VL, a 4,4'-diisocyanatodiphenylmethane from BAYER,

Reducing agent:

• R01 = 3,4-dihydroxybenzonitrile,
• R02 = 3,4-dihydroxybenzophenone,

Tint:

• TO1 = 7- (ethyl carbonate) benzo [e] - [1,3] oxazine-2,4-dione,
• TO2 = 7-methylbenzo [e] - [1,3] -oxazine-2,4-dione,

stabilizers:

• S01 = glutaric acid
• SO 2 = tetrachlorophthalic anhydride
• S03 = benzotriazole
  
  

Ingredients of the protective layer:

• ERCOL ^™ 48 20 = a polyvinyl alcohol from ACETEX EUROPE,
• LEVASIL ^™ VP AC 4055 = a 15% aqueous dispersion of colloidal silica with acid groups neutralized predominantly with sodium ions and a specific surface area of 500 m ² / g of BAYER AG / converted into the ammonium salt,
• ULTRAVON ^™ W = 75-85% concentrate of a Natriumarylsulfonats from Ciba Geigy converted into acid form by passing through an ion exchange column,
• SYLOID ^TM 72 = Silica from Grace,
• SERVOXYL ^TM VPDZ 3/100 = a mono [isotridecylpolyglycol ether (3EO)] phosphate from SERVO DELDEN BV
• SERVOXYL ^TM VPAZ 100 = a mixture of monolauryl and dilauryl phosphate from SERVO DELDEN BV,
• MICROACE TALC P3 = an Indian talc from NIPPON TALC,
• RILANIT ^™ GMS = a glycerol monothalic acid ester from HENKEL AG,
• TMOS = tetramethylorthosilicate hydrolyzed in the presence of methanesulfonic acid.

COMPARATIVE EXAMPLES 1 and 2 and INVENTION EXAMPLES 1 and 2

• ° VB : vergleichendes Beispiel,
• + EB = erfindungsgemäßes Beispiel,
• * Molprozentsatz, bezogen auf AgB.

The substantially light-insensitive thermographic materials of COMPARATIVE EXAMPLES 1 and 2 and INVENTION EXAMPLES 1 and 2 are prepared by coating a dispersion containing the following ingredients in 2-butanone on a 175 μm blue-pigmented polyethylene terephthalate support, the support having a CIELAB a * value of -9.5 and has a CIELAB b * value of -17.9 and is coated on its emulsion side with adhesive layer 01. After drying for 1 hour at 50 ° C. in a drying oven, layers having the compositions mentioned in Table 1 below are obtained. Table 1

• ° VB: comparative example,
• + EB = example according to the invention,
• * Molar percentage, based on AgB.

Subsequently, the heat-sensitive elements are coated in a wet thickness of 85 .mu.m with an aqueous composition containing the following ingredients with a pH adjusted to 3.8 with 1N nitric acid, and the coating is dried at 50.degree. C. for 15 minutes to give a protective layer PRO-L having the following composition is obtained ERCOL ^TM 48 20 = 2.1 g / m ² LEVASIL ^TM VP AC 4055 = 1.05 g / m ² ULTRAVON ^TM W = 0.075 g / m ² SYLOID ^TM 72 = 0.09 g / m ² SERVOXYL ^TM VPDZ 3/100 = 0.075 g / m ² SERVOXYL ^TM VPAZ 100 = 0.075 g / m ² MICROACE TALC P3 = 0.045 g / m ² RILANIT ^TM GMS = 0.15 g / m ² TMOS = 0.87 g / m ² (with complete conversion of TMOS into SiO ₂ )

The applied protective layer is characterized by 7-day heating of the essential light-insensitive thermographic material at 45 ° C and a cured relative humidity of 70%.

thermographic print

The substantially light-insensitive thermographic recording materials of COMPARATIVE EXAMPLES 1 and 2 and INVENTION EXAMPLES 1 and 2 are used in a DRYSTAR ^™ 4500 printer manufactured by AGFA-GEVAERT in a printing cycle. The printer prints at a resolution of 508 dpi, which had been changed to print at a print speed of 14 mm / s and a line time of 3.5 ms instead of 7.1 ms. In the printer, the 75 μm long (in the direction of conveyance) and 50 μm wide thermal head resistors are power modulated to print different image densities.

The maximum densities of the images (D _max ) measured behind a visible light filter with a MACBETH ^™ TR924 densitometer are all greater than 2.2.

evaluation thermographic properties

Of the Picture tone fresher, with the substantially light-insensitive thermographic Recording materials of COMPARATIVE EXAMPLES 1 and 2 and of the INVENTION EXAMPLES 1 and 2 printed prints is based on the CIELAB values L *, a * and b * in an optical Density D of 1.0 and 2.0 evaluated. The results of the evaluation are listed in Table 2.

Archivierbarkeitstests

The long-term archivability is tested in simulation tests, where with the substantially light-insensitive thermographic recording materials COMPARATIVE EXAMPLES 1 and 2 and the INVENTION EXAMPLES 1 and 2 prints obtained 3 days at 57 ° C and 34% relative humidity in the dark and then heated Shifts in the CIELAB values a * and b * are determined. The Results are also listed in Table 2.

Light box tests

It Light box tests are carried out, with the substantially light-insensitive thermographic materials of COMPARATIVE EXAMPLES 1 and 2 and the INVENTION EXAMPLES 1 and 2 for 3 days on the white PVC windows of a purpose built light box in one at a temperature of 30 ° C and a relative humidity (RH) of 85% Votsch climatic tester set be stored. 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 top of the light box and Loss of light from the light box, except for the loss of light through the white PVC plate, is prevented. 9 Planilux ^™ TLD 36W / 54 27mm diameter fluorescent lamps are placed in the length and equidistant from the two sides with the lamps equidistant from each other and to the sides across 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. The displacements of the CIELAB values a * and b * at an optical density D of 1.0 and the shift of the CIELAB value b * for the COMPARATIVE EXAMPLES 1 and 2 and the INVENTION EXAMPLES 1 and 2 are determined. The results are also listed in Table 2 below.

• * VB = vergleichendes Beispiel,
• + EB = erfindungsgemäßes Beispiel,
• ° SB : Stabilisatortyp.

In the luminous field tests, the substantially light-insensitive thermographic recording materials of INVENTION EXAMPLES 1 and 2 containing the compounds of the invention MBT-1 and MBT-2, respectively, have a significantly lower shift of the CIELAB b * values at an optical density D of 1.0 and of the CIELAB b * value at Dmin than in COMPARATIVE EXAMPLE 2 containing the compound MBT-C1. The substituted 2-mercaptobenzothiazoles MBT-1 and MBT-2 thus provide substantially light-insensitive thermographic recording materials with a significantly higher lightfastness than the unsubstituted 2-mercaptobenzothiazole MBT-C1. Table 2:

• * VB = comparative example,
• + EB = example according to the invention,
• ° SB: stabilizer type.

COMPARATIVE EXAMPLES 3 and 4

• ° VB : vergleichendes Beispiel,
• * Molprozentsatz, bezogen auf AgB.

The substantially light-insensitive thermographic material of COMPARATIVE EXAMPLES 3 and 4 is prepared by coating a dispersion containing the following ingredients in 2-butanone on the supports described above for COMPARATIVE EXAMPLES 1 and 2 and INVENTION EXAMPLES 1 and 2. After 3 minutes of drying at 85 ° C in a drying oven, layers having the compositions mentioned in Table 3 below are obtained. Table 3

• ° VB: comparative example,
• * Molar percentage, based on AgB.

Then coated one the heat sensitive ones Elements analogous to those for COMPARATIVE EXAMPLES 1 and 2 and the INVENTION EXAMPLES 1 and 2 described procedure with a protective layer.

• * VB = vergleichendes Beispiel,
• ° SB : Stabilisatortyp.

Evaluation of the thermographic properties of the substantially light-insensitive thermographic recording materials of COMPARATIVE EXAMPLES 3 and 4 is as described for COMPARATIVE EXAMPLES 1 and 2 and INVENTION EXAMPLES 1 and 2. The results are listed in Table 4. Table 4

• * VB = comparative example,
• ° SB: stabilizer type.

• * VB = vergleichendes Beispiel,
• ° SB : Stabilisatortyp.

The results listed in Table 4 are obtained with substantially non-photosensitive thermographic recording materials having a composition other than the composition of the substantially light-insensitive thermographic recording material obtained in Table 2. However, the effect of this difference in composition can be evaluated by comparing the results in the two tables obtained with substantially light-insensitive thermographic recording materials with the same stabilizer. The results for the substantially light-insensitive thermographic recording materials of COMPARATIVE EXAMPLE 1, COMPARATIVE EXAMPLE 3 and COMPARATIVE EXAMPLE 4, each employing the benzotriazole stabilizer SO 3, are listed in Table 5. Table 5

• * VB = comparative example,
• ° SB: stabilizer type.

• • negativere b*-Werte bei D = 1,0,
• • stärkere Verschiebungen der CIELAB b*-Werte nach 3tägiger Lagerung bei 57°C und 34% RF im Dunkeln und
• • um etwa 2,0 niedrigere Verschiebungen der CIELAB b*-Werte nach Belichtung im Leuchtkasten,

im Vergleich zur Zusammensetzung der für die VERGLEICHENDEN BEISPIELE 1 und 2 und die ERFINDUNGSGEMÄßEN BEISPIELE 1 und 2 benutzten wesentlich lichtunempfindlichen thermografischen Aufzeichnungsmaterialien. Aufgrund dieser Information können die in den Tabellen 2 und 4 aufgelisteten Ergebnisse als Ganzes betrachtet werden.From this comparison, it can be seen that the following values are obtained with the composition of the substantially light-insensitive thermographic recording material used for COMPARATIVE EXAMPLES 3 and 4

• • more negative b * values at D = 1.0,
• • stronger shifts in the CIELAB b * values after 3 days storage at 57 ° C and 34% RH in the dark and
• • by about 2.0 lower shifts in the CIELAB b * values after exposure in the lightbox,

Compared to the composition of the substantially light-insensitive thermographic recording materials used for COMPARATIVE EXAMPLES 1 and 2 and INVENTION EXAMPLES 1 and 2. Based on this information, the results listed in Tables 2 and 4 can be considered as a whole.

in the CIELAB system has a negative CIELAB b * value on a bluish one Picture tone, which becomes the bluer the more negative b * becomes and points a positive b * value indicates a yellowish tone, the more so becomes more yellow, the more positive b * becomes. What the visual recognition of a Image as a whole, has the picture tone of picture elements with a density of 1.0 a stronger one Effect as the picture of elements with a lower or higher optical density.

Image tone evaluation uses the image tone of AGFA-GEVAERT medical grade SCOPIX ^™ LT2B silver halide emulsion hardcopy film sold as a reference.

• • das wesentlich lichtunempfindliche thermografische, MBT-C1 enthaltende Aufzeichnungsmaterial des VERGLEICHENDEN BEISPIELS 2 weist eine schwache Lichtbeständigkeit im Leuchtkastentest auf, wie sich aus den starken Verschiebungen der CIELAB b*-Werte bei D = 1,0 und D_min ergibt, und
• • das wesentlich lichtunempfindliche thermografische, MBT-C2 enthaltende Aufzeichnungsmaterial des VERGLEICHENDEN BEISPIELS 4 weist eine schwache Archivierungsbeständigkeit im Archivierbarkeitskastentest auf, wie sich aus den starken Verschiebungen der CIELAB b*-Werte bei D = 1,0 ergibt, und

die wesentlich lichtunempfindlichen thermografischen Aufzeichnungsmaterialien der ERFINDUNGSGEMÄßEN BEISPIELE 1 und 2, die MBT-1 bzw. MBT-2 enthalten, weisen einen akzeptablen Bildton, eine akzeptable Archivierungsbeständigkeit und eine erheblich verbesserte Lichtbeständigkeit auf gegenüber dem wesentlich lichtunempfindlichen thermografischen, MBT-C1 enthaltenden Aufzeichnungsmaterial des VERGLEICHENDEN BEISPIELS 4.Considering the results listed in Table 2 and Table 4 for substantially light-insensitive thermographic 2-mercaptobenzothiazole (MBTs) containing recording materials as a whole, the following may be concluded

• The substantially light-insensitive, MBT-C1-containing thermographic recording material of COMPARATIVE EXAMPLE 2 has poor lightfastness in the luminous box test, as evidenced by the large displacements of the CIELAB b * values at D = 1.0 and D _min , and
• The substantially light-insensitive thermographic MBT-C2-containing recording material of COMPARATIVE EXAMPLE 4 has poor archival stability in the Archivability Box Test, as evidenced by the large displacements of the CIELAB b * values at D = 1.0, and

the substantially light-insensitive thermographic recording materials of INVENTION EXAMPLES 1 and 2 containing MBT-1 and MBT-2, respectively, have acceptable image tone, archival stability, and significantly improved lightfastness over the substantially light-insensitive thermographic MBT-C1 containing recording material of the COMPARATIVE EXAMPLE 4.

COMPARATIVE EXAMPLES 5 to 7 and INVENTION EXAMPLES 3 to 11

• + VB : vergleichendes Beispiel,
• ° EB : erfindungsgemäßes Beispiel,
• * Molprozentsatz, bezogen auf AgB.

The substantially light-insensitive thermographic materials of COMPARATIVE EXAMPLES 5 to 7 and INVENTION EXAMPLES 3 to 11 are prepared by coating a dispersion containing the following ingredients in 2-butanone on the supports described above for COMPARATIVE EXAMPLES 1 and 2 and INVENTION EXAMPLES 1 and 2 produced. After 3 minutes of drying at 85 ° C in a drying oven, layers having the compositions mentioned in Table 6 below are obtained. Table 6

• + VB: comparative example,
• ° EB: example according to the invention,
• * Molar percentage, based on AgB.

Then coated one the heat sensitive ones Elements analogous to those for COMPARATIVE EXAMPLES 1 and 2 and the INVENTION EXAMPLES 1 and 2 described procedure with a protective layer.

The Evaluation of the thermographic properties of the substantially light-insensitive thermographic recording materials of COMPARATIVE EXAMPLES 5-7 and the INVENTION EXAMPLES 3 to 11 is as above for COMPARATIVE EXAMPLES 1 and 2 and the INVENTION EXAMPLES 1 and 2 described. The results are listed in Table 7.

• * VB = vergleichendes Beispiel,
• + EB = erfindungsgemäßes Beispiel,
• ° SB : Stabilisatortyp.

The substantially light-insensitive thermographic recording materials of INVENTION EXAMPLES 3 to 11 containing the stabilizers MBT-3 to MBT-11 exhibit improved lightness fastness, ie, reduced displacements of the CIELAB b * value at Dmin, as compared to those containing no stabilizer light-insensitive recording materials of COMPARATIVE EXAMPLE 7, as well as a comparable or reduced shift of the CIELAB b * value at Dmin as compared to the benzotriazole-containing substantially light-insensitive recording materials of COMPARATIVE EXAMPLE 8. Table 7

• * VB = comparative example,
• + EB = example according to the invention,
• ° SB: stabilizer type.

The The present invention may implicitly or explicitly include any herein property described, any combination of those described herein Include properties or generalization thereof. Due to the above Description of the present invention should be apparent to those skilled in the art clear that here within the scope of protection Numerous modifications are possible with the present invention.

Claims (7)

A substantially light-insensitive monochrome black-and-white single-sheet recording material comprising a support and a heat-sensitive element, the heat-sensitive element being a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal effective relationship thereto, at least one polycarboxylic acid and / or one polycarboxylic anhydride in a molar ratio of at least 15, based on the total amount of all organic silver salts and in a thermally effective relationship thereto, a binder and at least one 2-mercaptobenzothiazole compound of the following formula (I)

in which R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, an optionally substituted Al kylgruppe, an optionally substituted aryl group, an alkoxy group, an ester group, a carbamate group, a carbonate group, an SO ₂ R ⁵ group, an -NR ⁶ R ⁷ group, a cyano group, an acyl group, a halogen atom, an optionally alkyl-substituted or alkoxy-substituted -SO _{2 is} NH-phenyl, perfluoroalkyl, -CONHR ⁸ , -NHOCR ⁹ , -OCOOR ¹⁰ or -NHCOOR ¹¹ , R ⁵ , R ⁹ , R ¹⁰ and R ¹¹ independently of one another are an optionally substituted alkyl group or an aryl group, R ⁶ , R ⁷ and R ⁸ independently of one another represent a hydrogen atom, an optionally substituted alkyl group or an acyl group and R ¹ and R ² together, R ² and R ³ together and R ³ and R ⁴ together independently of one another may be the atoms required for forming a carbocyclic, heteroaromatic or heterocyclic ring, with the proviso that R ¹ , R ² , R ³ and / or R ^{4 is} a Wass atomic atom means or mean. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 1, characterized in that the at least one 2-mercaptobenzothiazole compound of the formula (I) represents an alkyl group, an aryl group, a Alkoxy group, a cyano group or an acyl group or a halogen atom substituted 2-mercaptobenzothiazole compound. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 1, characterized in that at least one of optionally substituted alkyl groups by a group selected from the group from halogen atoms, groups containing a 2-mercaptobenzothiazole moiety containing an alkyl group, an alkoxy group, a mercapto group and a hydroxyl group. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 1, characterized in that at least one of optionally substituted aryl groups by a group from the group from halogen atoms, groups containing a 2-mercaptobenzothiazole moiety containing an alkyl group, an alkoxy group, a mercapto group and a hydroxyl group. Substantially light-insensitive black and white monosheet thermographic recording material according to one of the preceding claims, characterized in that the at least one stabilizer

Substantially light-insensitive black and white monosheet thermographic recording material according to one of the preceding claims, characterized in that the at least one stabilizer

Substantially light-insensitive thermographic Black and white single sheet recording material behind one of the preceding claims, characterized in that the heat-sensitive element is further contains an optionally substituted benzotriazole.