DE60307213T2 - Barrier layers for substantially light-insensitive thermographic recording materials - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The The present invention relates to barrier layers 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 is an imagewise exposure and direct thermal processes, wherein the imaging process a pictorial heating step includes. Direct thermal printing becomes a visible pattern by imagewise heating of a Produced recording material.

In US Pat. No. 3,832,186 For example, in EXAMPLE 9, there is disclosed a photosensitive thermal development material obtained by coating a polyethylene terephthalate film support with a polyvinyl butyral, silver benzotriazole, mercury bromide, a benzoxazolide hydohydant sensitizing dye, ascorbic acid monomyristate as a reducing agent and 3-mercapto-5-phenyl-4-phenyl-1,2,4-triazole composition containing and coating this composition with a vinyl chloride-vinyl acetate copolymer (weight ratio 85:15) is obtained.

In US 3,933,508 discloses a heat-developable photosensitive material consisting of a support of (1) an organic silver salt, (2) a photosensitive silver halide or a silver halide prepared by reacting the organic silver salt with a halide, (3) a reducing agent, (4) a binder, and (5) a coating layer coated on components (1) - (4), wherein components (1) - (4) coated in a single layer consist essentially of a polymer having a refractive index greater than about 1 , 45 at 20 ° C, is heat resistant to temperatures greater than about 46 ° C and colorless and is soluble in organic solvents, and make the coating layer more translucent. Examples of according to US 3,933,508 Polymers used for the overcoat layer, which are preferably heat resistant, colorless, and soluble in solvents, are polyvinyl chloride, polyvinyl acetate, copolymers of vinyl chloride and vinyl acetate containing greater than 50 mole% vinyl chloride but not sufficient vinyl chloride to lower heat resistance, polyvinyl butyral , Polystyrene, polymethylmethacrylate, benzylcellulose, ethylcellulose, cellulose acetate butyrate, cellulose acetate, polyvinylidene chloride, polyvinylpyrrolidone, cellulose propionate, polyvinylformal, cellulose acetate phthalate, polycarbonates and cellulose acetate propionate. Also preferred are gelatin, gelatin derivatives such as phthalated gelatin, acrylamide polymers, polyisobutylene, butadiene-styrene copolymers (without limitation of monomer content) and polyvinyl alcohol. EXAMPLES 5, 10, 12 and 18 illustrate, for example, a coating layer containing a vinyl chloride-vinyl acetate copolymer (95% by weight of vinyl chloride, 5% by weight of vinyl acetate).

In GB-A-1 422 057 discloses a heat-developable radiation-sensitive material disclosed on a carrier a layer of (1) an organic silver salt, (2) a photosensitive Silver halide, its grains consist of at least 30 mol% of silver iodide, (3) a reducing agent and (4) one on the surface the silver halide grains adsorbed spectral sensitizing dye, wherein the sensitizing dye an oxidation potential of at most 1.00 volts and a difference between its oxidation potential value and its reduction potential value of at least 2.00 volts. EXAMPLE 4 discloses a heat developable silver benzotriazolate radiation-sensitive layer with a cover layer of vinyl chloride-vinyl acetate copolymer (Weight ratio: 85:15).

DE-A 24 39 460 discloses a thermally-developable material which consists of a support comprising (a) an organic silver salt, (b) a catalytic amount of a silver halide or a photosensitive prepared by reacting the organic silver salt with a halide Silver halide, (c) a reducing agent, and (d) a binder having thereon an overcoat layer containing a polymeric layer having kaolin dispersed therein. DE-A 24 39 460 discloses the following polymers for the topcoat layer: (a) copolyesters, (b) nylon compounds, (c) vinylidene dichloride copolymers, (d) ethylene-vinyl acetate copolymers, (e) cellulose ethers, ( (f) polyethylene, (g) synthetic rubbers, (h) cellulose esters, (i) polyvinyl esters, (j) polyacrylates and α-alkyl polyacrylate esters, (k) high molecular weight polyethylene oxides of polyglycols having an average molecular weight of about 4,000 to 1,000,000, (l ) Polyvinylchloride and copolymers, (m) polyvinyl acetals, (n) polyformaldehydes, (o) polyurethanes, (p) polycarbonates, (q) polystyrenes, (r) gelatin and gelatin derivatives, (s) polyvinyl alcohol and (t) natural Colloids. In EXAMPLE 4, a coating layer containing a vinyl chloride-vinyl acetate copolymer (weight ratio 95: 5) is disclosed.

In US 4,197,131 discloses a photosensitive composition comprising an intimate mixture of a substantially photosensitive silver compound which causes a visible change upon reduction and a sufficient amount of a silver halide to catalyze the reduction and, in the areas where the silver halide is exposed, when heated the mixture in the presence of a reducing agent to obtain a visible change, and as a yellow screen dye, a 1-alkyl-4-nitromethylenchinolan, wherein the alkyl substituent contains 1 to 4 carbon atoms. The EXAMPLES describe the coating on the photosensitive dispersion of a coating film containing a vinyl chloride-vinyl acetate copolymer available from Union Carbide under the trade name VYNS.

In the EXAMPLES of US 4,450,229 describes coating a photothermographic element comprising a binder, a photosensitive silver halide in catalytic proximity to a light-insensitive silver source material in the element containing a reducible source of silver ions, a reducing agent for silver ions and a suitable latent image stabilizing compound of a particular class of compounds , described with a vinyl acetate-vinyl chloride copolymer (80 wt .-% vinyl acetate, 20 wt .-% vinyl chloride) containing layer.

In US 4 558 003 discloses an unexposed photothermographic article comprising a support and a silver-containing layer containing a binder, a silver compound having reducible silver ions, silver halide in catalytic proximity to the silver compound, and a silver ion reducing agent, wherein the binder comprises at least 25% by weight of a poly ( vinyl acetal), wherein the article uses an adequate amount of a borate ion, a boric acid salt or a boric acid or one of these substances in combination with an isocyanate to cure the binder. In EXAMPLE 1, a topcoat of a poly (vinyl acetate) / poly (vinyl chloride) copolymer (80/20) is described.

In US 4,460,681 there is disclosed a photothermographic color image-forming article comprising a substrate, a photothermographic emulsion layer, an organic solvent-soluble barrier layer and a second photothermographic emulsion layer coated on a polymeric overlay, each of the two photothermographic layers comprising a reducible silver source, radiation-sensitive silver halide, a reducing agent for Further, a first photothermographic layer is sensitized to a portion of the spectrum that differs by at least 60 nm to the region to which the other photothermographic layer is sensitized, and each photothermographic layer is a leuco dye containing, on oxidation, a visible dye whose maximum absorbency is at least 60 nm to that of the at least one other street and wherein the barrier layer is present between the photothermographic layers and is impenetrable to the solvent contained in the second photothermographic layer. As the second layer forming "barrier polymers" according to US 4,460,681, maleic anhydride / vinylmethyl ether copolymers, polyvinylidene chloride (SARAN ^™ ) or polyvinylpyrrolidone can be used with maleic acid copolymers such as alkyl monoesters of poly (methyl vinyl ether / maleic acid) being preferred. The "barrier polymer" which forms the fourth layer and preferably contains the color reagents is typically a methyl methacrylate polymer (preferably a hard polymer having a Tukon hardness of at least 20), a copolymer or a blend with other polymers or copolymers (eg Copolymer with n-butyl acrylate, butyl methacrylate and other acrylates such as acrylic acid, methacrylic acid, acrylic anhydride and the like), polystyrene or a combination of a polyvinyl chloride copolymer with a butadiene-styrene copolymer. Preferred as the polymer is a mixed with soft Methylmethacrylatcopolymeren hard Methylmethacrylathomopolymeren. In EXAMPLE 5, a yellow / magenta barrier layer of a butadiene-styrene copolymer and a polyvinyl chloride-acetate-alcohol polymer (VAGH) is described.

EP-A-0 536 955 discloses a thermally developable photothermographic article comprising: (a) an image-receiving element containing a polymeric image-receiving layer, and (b) a photothermographic imaging member removably adhered to the image-receiving element comprising a plurality of emulsion layers, each comprising a binder, a silver source material and a leuco dye, and containing between each pair of emulsion layers a dye-permeable intermediate layer. It is further disclosed in EP-A 0 536 955 that the first intermediate layer must be impermeable to the solvent used to apply the next layer. However, the polymer used to form the first intermediate layer can be made of any organic solvent. The polymer of the first intermediate layer is preferably a thermoplastic polymer. To form the first intermediate layer For example, homopolymers of vinyl chloride or copolymers of vinyl chloride, preferably having a glass transition point higher than 80 ° C, for example, a copolymer of vinyl chloride (96%) and vinyl acetate (4%) and a mixture of poly (vinyl chloride) (90%) and Poly (vinyl acetate) (10%) can be used. In EXAMPLE 1, for example, an intermediate layer containing a terpolymer of vinyl chloride (83%), vinyl acetate (16%) and maleic acid (1%) is illustrated.

In US 4,942,115 discloses a heat-developable imaging element comprising a support, a heat-developable hydrophobic imaging layer overlying it, and an overcoat layer containing poly (silicic acid) and a hydrophilic monomer or polymer on the support-side of the imaging layer, the element being between the cover layer and the imaging layer contains a polymeric adhesion promoting layer. In US 4,942,115 discloses that useful polymers for use in the adhesion promoting layer are selected from the group consisting of: (1) terpolymers of 2-propenenitrile, 1,1-dichloroethene, and propenoic acid, as described in U.S. Pat US 3,271,345 and (2) terpolymers of 2-propenoic acid, methyl ester, 1,1-dichloroethene and itaconic acid as described in for example US 3,437,484 wherein a polymeric adhesive layer comprising poly (2-propenenitrile-co-1,1-dichloroethene-co-2-propenoic acid) or poly (2-propenoic acid methyl ester-co-1,1-dichloroethene-co-itaconic acid), and a polymeric adhesive layer containing poly (2-propenenitrile-co-1,1-dichloroethene-co-2-propenoic acid) is exemplified.

In US 6,352,819 discloses a high contrast black and white photothermographic material comprising a support and cast thereon (a) one or more heat developable high contrast imaging layers comprising a binder and radiation sensitive silver halide, a nonradiation sensitive source of reducible silver ions, a nonradiative reducing composition Contains a source of reducible silver ions and a strong contrast agent, and (b) a barrier layer coated on said same side of the support as said high contrast imaging layer (s) on said layer (s), said barrier layer forming a film forming layer Contains polymer and is impermeable to or reactive with all components that can diffuse at a temperature above 80 ° C from the (the) imaging layer (s). In US 6,352,819 Further, but not to be claimed, there is disclosed a high contrast black and white thermographic material comprising a support and overcoated thereon (a) one or more heat developable and nonradiation sensitive, high contrast imaging layers which reduce a binder and, in reactive relation thereto, a non-radiation sensitive source Containing silver ions, a reducing composition for the nonradiation-sensitive source of reducible silver ions and a strong contrast agent, and (b) a barrier layer on the same side of the support as the high contrast imaging layer (s) on this layer ( en), wherein the barrier layer contains a film-forming polymer and is impermeable to or reactive with all constituents which can diffuse from the imaging layer (s) at a temperature above 80 ° C. The term "thermographic material" is a generic term that includes photothermographic materials, and the mention of the high contrast thermographic material does not preclude the presence of radiation sensitive substances such as radiation sensitive silver halide US 6,352,819 to find no specific description of substantially light-insensitive thermographic materials and also contains the US 6,352,819 no examples of substantially light-insensitive thermographic materials. Certain particularly useful barrier materials according to US 6,352,819 include polyvinyl alcohol, a styrene polymer (as well as polymers of styrene derivatives), a vinyl halide polymer, a vinyl acetate polymer [such as polyvinyl acetate, poly (ethylene-co-vinyl acetate) or a copolymer of a vinyl halide and vinyl acetate], a polyvinylpyrrolidone, a water-soluble or water-dispersible polyester and gelatin (which also includes demineralized and acid-processed gelatin) or a gelatin derivative (such as phthalated gelatin and carbamoylated gelatin), with the styrenic polymers, vinyl acetate polymers and polyvinyl alcohol being preferred. EXAMPLE 12 describes a barrier layer containing a vinyl chloride-vinyl acetate copolymer; EXAMPLE 32 describes a barrier layer containing a styrene-acrylonitrile copolymer (weight ratio: 75:25); in EXAMPLE 33 a barrier layer is described discloses the vinyl chloride-vinyl acetate copolymer U CAR VYNS from Union Carbide, and EXAMPLE 34 describes a barrier layer containing the vinyl chloride-acetate-vinyl alcohol copolymer U CAR VAGH from Union Carbide.

It has been found that in order to obtain a neutral image tone in substantially light-insensitive monochrome thermographic monochrome sheet materials, reductants and toning agents are required which, despite the presence of an outer protective layer during storage, both diffuse before and after the printing process to the surface of the material and, in extreme cases, cause the user visually observes deposits of reducing agents, tints and reaction products of the image forming process on the surface of the materials. For this reason, are substantially lichtunempfindli However, monochrome thermographic monochrome sheet materials that have acceptable neutral image tone but no precipitate of reducing agents, tints, and reaction products of the imaging process are required.

TASKS OF PRESENT INVENTION

task Therefore, the provision of one is essential to the present invention light-insensitive monochrome monochrome thermographic material, the comes up with an acceptable neutral image tone, but on his surface no formation of precipitate of, for example, a reducing agent, a tint and carboxylic acid having.

Further Objects and advantages of the present invention will be apparent from the following Description visible.

SHORT PRESENTATION THE PRESENT INVENTION

Out US 6,352,819 It is known that the barrier layer contains one or more film-forming polymers that react (react) or as with a physical barrier to diffusible by-products resulting from the presence of high contrast agents such as acrylonitrile helper developers, hydrazide helper developers and isoxazole helper developers such lock acts (acts). It has unexpectedly been found that prints of substantially light-insensitive black-and-white monochrome thermographic materials containing heat-sensitive elements which do not contain a strong contrast agent but contain at least a substantially light-insensitive silver salt of a carboxylic acid and ortho-dihydroxybenzene derivatives as a reducing agent in combination with a barrier layer a copolymer having vinyl chloride units and vinyl acetate units and / or vinyl alcohol units and / or a copolymer having styrene units and acrylonitrile units and being present between the outer protective layer and the heat-sensitive element, have acceptably neutral image tones as indicated by the CIELAB values a * and b * surface precipitates are formed neither before nor after the printing process. The CIELAB values L *, a * and b * are obtained according to spectrophotometric measurements according to ASTM standard E179-90 in an R (45/0) geometry with an evaluation according to ASTM standard E308-90.

Be solved the objects of the present invention by a substantially light-insensitive thermographic Black White-sheet recording material with a carrier and on one side of the vehicle a heat sensitive Element, a barrier layer and an outer protective layer, wherein the heat-sensitive Element not a strong contrast agent, but a substantially lichtunempfindliches Silver salt of a carboxylic acid, at least one reducing agent for this in thermal effective Relationship to it, at least a toning agent and contains a binder, characterized in that the at least one reducing agent is an ortho-dihydroxybenzene derivative and the barrier layer is a copolymer with vinyl chloride units and vinyl acetate units and / or vinyl alcohol units, a copolymer having styrene units and acrylonitrile units Copolymer with cationic units and / or a copolymer with Styrene units and maleic acid units contains.

preferred embodiments The present invention is described in the detailed description of the present 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 and 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.

The principal function of the products termed "strong contrast agents", which term is sometimes considered synonymous with "co-developer" or "auxiliary developer", is to increase the contrast of the material by reducing all or most of the reducible silver ions contained in the substantially light-insensitive silver salt of a carboxylic acid Examples of strong contrast agents are acrylonitrile helper developers, hydrazide helper developers, and isoxazole helper developers, as described in U.S. Patent No. 5,376,855 US 6,352,819 ,

The warming in connection with that used in the present invention Expression "essential Anhydrous conditions "means a warming to a temperature of 80 ° C up to 250 ° C. Under the term used in the present invention "substantially anhydrous conditions " itself, that the reaction system is almost in equilibrium with water is in the air and water for the triggering or promoting the reaction not in particular or to a considerable degree of the outside the thermographic recording material is supplied. Such a condition is described by T.H. James in The Theory of the Photographic Process, 4th Edition, Macmillan 1977, page 374 described.

thermosensitive element

Of the as used in the present invention, term "heat-sensitive Element "is that Element containing all the image-forming components. The thermosensitive Element of the invention essential light-insensitive monochrome monochrome thermographic recording material contains one or a plurality of substantially light-insensitive silver salts of a carboxylic acid ortho-dihydroxybenzene derivative as a reducing agent therefor in thermal effective relationship to it, a tinting agent and a binder. The heat-sensitive Element may consist of a layer system in which the above Active ingredients can be dispersed in different layers, however must the substantially light-insensitive silver salt of a carboxylic acid in reactive Relationship to the ortho-dihydroxybenzene derivative reducing agent, i. E. 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 silver salt of a carboxylic acid over-diffuse and that with it the reduction to silver can take place. at Such materials have the possibility of being substantially light-insensitive Silver salt of a carboxylic acid and / or the ortho-dihydroxybenzene derivative reducing agent therefor in heat-sensitive microcapsules encapsulate as described in EP-A 0 736 799.

Essentially light-insensitive Silver salt of a carboxylic acid

To a first embodiment of the invention essential light-insensitive monochrome monochrome thermographic recording material the substantially light-insensitive silver salt of a carboxylic acid no organic double salt containing a silver cation in combination with a second cation, e.g. Magnesium or iron ions.

To a second embodiment of the invention essential light-insensitive black-and-white monochrome thermographic recording material the substantially light-insensitive silver salt of a carboxylic acid essentially light-insensitive silver salt of a fatty acid known aliphatic carboxylic acid, in which the aliphatic carbon chain is preferably at least Contains 12 carbon atoms, e.g. Silver laurate, silver palmitate, silver stearate, silver hydroxystearate, Silver oleate and silver behenate, these silver salts also be referred to as "silver soaps". Other silver salts of an organic carboxylic acid as described in GB-P 1,439,478, e.g. Silver benzoate, also come for the production a heat-developable Silver picture in question. Combinations of different silver salts an organic carboxylic acid are also suitable for use in the present invention, as described in EP-A 964 300.

ortho-dihydroxybenzene derivative

According to a third embodiment of the substantially light-insensitive black and white monosheet thermographic recording material of the present invention, the ortho-dihydroxybenzene derivative is selected from the group consisting of catechol, 3- (3,4-dihydroxyphenyl) propionic acid, 3,4-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid esters Gallic acid, gallic acid esters, for example methyl gallate, ethyl gallate and propyl gallate, 3,4-dihydroxybenzaldehyde, 3,4-dihydroxyacetophenone, 3,4-butyrophenone, 3,4-dihydroxybenzophenone, 3,4-dihydroxybenzophenone derivatives, 3,4-dihydroxybenzonitrile and Tannic acid as described in EP-A 0 692 733, EP-A 0 903 625, EP-A 1 245 403 and EP-A 1 245 404.

It can also combinations of reducing agents are used, which when heated to participants in the reduction reaction of at least become a substantially light-insensitive organic silver salt.

tint

in der R¹ eine gegebenenfalls durch eine Hydroxylgruppe, Carboxylgruppe, Carboxylestergruppe, Acylgruppe oder Carbonatgruppe substituierte Alkylgruppe bedeutet, X S, O oder N-R⁶ ist, R⁶ eine gegebenenfalls substituierte Alkylgruppe bedeutet, R², R³, R⁴ und R⁵ unabhängig voneinander jeweils ein Wasserstoffatom, ein Halogenatom oder eine Alkylgruppe, eine Alkoxygruppe, eine Thioalkoxygruppe, eine Nitrogruppe, eine Cyangruppe, eine Carboxylgruppe, eine Carboxylestergruppe, eine Acylgruppe, eine Aldehydgruppe, eine Acylamidgruppe, eine Sulfonamidgruppe, eine Acylaminogruppe, eine Carbonatgruppe, eine Hydroxylgruppe oder eine Arylgruppe bedeuten oder R² und R³, R³ und R⁴ und/oder R⁴ und R⁵ unabhängig voneinander jeweils die zur Bildung einer carbocyclischen oder heterocyclischen Gruppe benötigten Atome darstellen oder R¹ und R⁵ und/oder R² und R⁶ unabhängig voneinander jeweils die zur Bildung eines heterocyclischen Ringes benötigten Atome darstellen, Verbindungen der Formel (II):

in der R⁷ eine gegebenenfalls substituierte Alkylgruppe bedeutet, Y S, O oder N-R¹⁰ bedeutet, R¹⁰ eine gegebenenfalls substituierte Alkylgruppe bedeutet, R⁸ und R⁹ unabhängig voneinander jeweils ein Wasserstoffatom, ein Halogenatom oder eine Alkylgruppe, eine Alkoxygruppe, eine Thioalkoxygruppe, eine Nitrogruppe, eine Cyangruppe, eine Carboxylgruppe, eine Carboxylestergruppe, eine Arylgruppe, eine Aldehydgruppe, eine Acylamidgruppe, eine Sulfonamidgruppe, eine Acylaminogruppe, eine Carbonatgruppe, eine Hydroxylgruppe oder eine Arylgruppe bedeuten oder R⁸ und R⁹ die zur Bildung eines heterocyclischen oder nicht-aromatischen carbocyclischen Ringes benötigten Atome darstellen oder R⁸ und R¹⁰ und/oder R⁹ und R⁷ unabhängig voneinander jeweils die zur Bildung eines heterocyclischen Ringes benötigten Atome bedeuten und R⁸ und R⁹ nicht beide eine Alkylgruppe bedeuten können, und Verbindungen der Formel (III):

in der R¹¹ ein Wasserstoffatom oder eine C1- bis C3-Alkylgruppe, eine C1- bis C3-Alkenylgruppe, eine C1- bis C3-Alkynylgruppe, eine Cycloalkylgruppe, eine Alkarylgruppe, eine Arylgruppe, eine heterocyclische Gruppe oder eine Heteroarylgruppe bedeutet, wobei all diese Gruppen gegebenenfalls substituiert sind, mit der Maßgabe, dass R¹¹ kein Wasserstoffatom sein darf, falls sowohl R¹² als R¹³ beide Wasserstoffatome sind, R¹² und R¹³ unabhängig voneinander ein Wasserstoffatom oder eine Amidgruppe, eine Estergruppe, eine Carboxylgruppe, eine Carbonatgruppe, eine Alkylgruppe, eine Alkenylgruppe, eine Alkynylgruppe, eine Cycloalkylgruppe, eine Alkarylgruppe, eine Arylgruppe, eine heterocyclische Gruppe oder eine Heteroarylgruppe bedeuten, wobei all diese Gruppen gegebenenfalls substituiert sind, R¹² und R¹³ zusammen die zum Vervollständigen eines gegebenenfalls substituierten alicyclischen, heterocyclischen oder heteroaromatischen Ringes benötigten Atome bedeuten können und X eine Carbonylgruppe oder eine -N-R¹⁴-Gruppe bedeutet, in der R¹⁴ eine Alkylgruppe bedeutet.According to a fourth embodiment of the substantially light-insensitive black and white monosheet thermographic recording material of the present invention, the tinting agent (s) are selected from the group consisting of phthalazinone, phthalazinone derivatives, benzoxazine dione and benzoxazine dione derivatives, naphthoxazine dione and naphthoxazine dione derivatives, pyridazone, pyridazone derivatives , Compounds of formula (I):

wherein R ^{1 is} an alkyl group optionally substituted by a hydroxyl group, carboxyl group, carboxyl ester group, acyl group or carbonate group, X is S, O or NR ⁶ , R ^{6 is} an optionally substituted alkyl group, R ² , R ³ , R ⁴ and R ^{5 are} independently each represents a hydrogen atom, a halogen atom or an alkyl group, an alkoxy group, a thioalkoxy group, a nitro group, a cyano group, a carboxyl group, a carboxylester group, an acyl group, an aldehyde group, an acylamide group, a sulfonamide group, an acylamino group, a carbonate group, a hydroxyl group or a Aryl group or R ² and R ³ , R ³ and R ⁴ and / or R ⁴ and R ⁵ are each independently the atoms required to form a carbocyclic or heterocyclic group or R ¹ and R ⁵ and / or R ² and R ⁶ each independently represent the atoms required to form a heterocyclic ring, compounds of Formula (II):

wherein R ^{7 is} an optionally substituted alkyl group, YS, O or NR ¹⁰ , R ^{10 is} an optionally substituted alkyl group, R ⁸ and R ⁹ are each independently a hydrogen atom, a halogen atom or an alkyl group, an alkoxy group, a Thioalkoxygruppe, a Nitro group, a cyano group, a carboxyl group, a carboxyl ester group, an aryl group, an aldehyde group, an acylamide group, a sulfonamide group, an acylamino group, a carbonate group, a hydroxyl group or an aryl group, or R ⁸ and R ⁹ to form a heterocyclic or non-aromatic carbocyclic ring required atoms represent or R ⁸ and R ¹⁰ and / or R ⁹ and R ⁷ independently of one another are each necessary for forming a heterocyclic ring atoms and R ⁸ and R ^{9 are} not both an alkyl group, and compounds of the formula (III ):

in the R ^{11 is} a hydrogen atom or a C 1 to C 3 alkyl group, a C 1 to C 3 alkenyl group, a C 1 to C3-alkynyl group, a cycloalkyl group, an alkaryl group, an aryl group, a heterocyclic group or a heteroaryl group, where all these groups are optionally substituted, with the proviso that R ¹¹ can not be a hydrogen atom, if both R ^{12 and} R ¹³ are both hydrogen atoms R ¹² and R ¹³ independently of one another denote a hydrogen atom or an amide group, an ester group, a carboxyl group, a carbonate group, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an alkaryl group, an aryl group, a heterocyclic group or a heteroaryl group, wherein all of these groups are optionally substituted, R ¹² and R ^{13 may} together represent the atoms needed to complete an optionally substituted alicyclic, heterocyclic or heteroaromatic ring, and X represents a carbonyl group or an -NR ¹⁴ group in which R ^{14 represents} an alkyl group ,

Suitable suitable substituents for the alkyl groups of R ¹ , R ⁶ , R ⁷ and R ¹⁰ are independently a carboxyl group and a carboxyl ester to name. Suitable substituted alkyl groups include a -CH ₂ COOH group, a -C ₂ H ₄ COOH group and a -C ₂ H ₄ COOC ₂ H ₅ group.

Suitable benzoxazine dione toning agents for use in the thermographic material of the present invention are described in U.S. Patent No. 4,348,830 GB 1 439 478 . US 3,951,660 and US Pat. No. 5,599,647 ,

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, 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 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 of 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.

junction

Be solved the objects of the present invention by a substantially light-insensitive thermographic Black White-sheet recording material with a carrier and on one side of the vehicle a heat sensitive Element, a barrier layer and an outer protective layer, wherein the heat-sensitive Element not a strong contrast agent, but a substantially lichtunempfindliches Silver salt of a carboxylic acid, at least one reducing agent for this in thermal effective Relationship to it, at least a toning agent and contains a binder, characterized in that the at least one reducing agent is an ortho-dihydroxybenzene derivative and the barrier layer is a copolymer with vinyl chloride units and vinyl acetate units and / or vinyl alcohol units, a copolymer having styrene units and acrylonitrile units Copolymer with cationic units and / or a copolymer with Styrene units and maleic acid units contains.

To a fifth embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material is the barrier layer between the thermosensitive element and the outer protective layer inserted.

Though is the mechanism of restrictive Influence of the barrier layers according to the invention the diffusion of ingredients and reaction products of the imaging process to the surface the protective layer is unknown, but it is assumed that that these layers can play a dual role, i. they form one impenetrable barrier over certain of the ingredients and at the same time react with others of the over-diffusing Substances. The in the barrier layer of the thermographic according to the invention Materials used in the copolymers all contain a more polar substance, e.g. Vinyl chloride, acrylonitrile, maleic acid and cationic units, and less polar substances, e.g. Styrene and vinyl acetate. Such could polar substances a barrier opposite to form the diffusion of non-polar substances.

To a sixth embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the copolymer with vinyl chloride units and vinyl acetate units up to 95% by weight of vinyl chloride. The weight ratio of vinyl chloride to vinyl acetate did not turn out to be critical. The copolymer can be further Comonomers included, however, it has been found that such no critical role in the performance of the copolymer as a barrier to the Diffusion of ingredients or reaction products of the imaging process play.

To a seventh embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the copolymer with styrene units and acrylonitrile units between 20% by weight and 60% by weight of acrylonitrile.

To an eighth embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the copolymer with cationic units quaternary ammonium units, quaternary phosphonium units or ternary Sulfonium.

To a ninth embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the copolymer having cationic units of methacrylamidepropyltrimethylammonium chloride units or dimethyldiallylammonium chloride units.

It has shown that the barrier layers an optimal limiting Influence on the diffusion of ingredients and reaction products of the image forming process, if their order from 5 to 20 wt .-% of the copolymer-containing coating solutions and / or in a wet layer thickness between 5 and 20 μm he follows.

Suitable copolymers for use in the substantially light-insensitive monochrome thermographic black-and-white single sheet recording material of the invention are listed in the following table:

protective layer

The Outer protective layer protects the heat sensitive 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, which is the outermost layer, can be solved from one Lubricant and / or a particulate material, such as e.g. Talc particles, which optionally consist of the outer layer protrude. examples for suitable lubricants are surfactants, liquid lubricants, solid lubricants or mixtures thereof with or without polymeric binder.

To a tenth embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the outer protective layer the reaction product of at least one hydrolyzed polyalkoxysilane and a hydroxyl group-containing polymer.

To an eleventh embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the outer protective layer the reaction product of a hydrolyzed tetraalkoxysilane, e.g. Tetramethoxysilane or tetraethoxysilane, and polyvinyl alcohol.

stabilizers

To a twelfth embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the heat sensitive Element further a stabilizer.

in der R¹⁵ eine -NR¹⁶R¹⁷-Gruppe, eine -OR¹⁸Gruppe oder eine gegebenenfalls substituierte Arylgruppe oder Heteroarylgruppe ist, wobei R¹⁶ ein Wasserstoffatom oder eine gegebenenfalls substituierte Alkylgruppe, Arylgruppe oder Heteroarylgruppe ist, R¹⁷ eine gegebenenfalls substituierte Arylgruppe oder Heteroarylgruppe ist und R¹⁸ eine gegebenenfalls substituierte Arylgruppe ist, und Verbindungen mit zwei oder mehr Gruppen der Formel (V):

in der Q die zur Bildung eines 5- oder 6-gliedrigen ungesättigten heterocyclischen Ringes benötigten Atome bedeutet, A ein Wasserstoffatom oder ein Gegenion zum Ausgleichen der Negativladung der Thiolatgruppe bedeutet oder zwei oder mehr A-Gruppen eine Verbindungsgruppe zwischen den zwei oder mehr Gruppen der Formel (V) darstellen.According to a thirteenth embodiment of the substantially light-insensitive black and white monosheet thermographic recording material, the thermosensitive element further contains a stabilizer selected from the group consisting of benzotriazole, substituted benzotriazoles, aromatic polycarboxylic acids such as orthophthalic acid, 3-nitrophthalic acid, tetrachlorophthalic acid, mellitic acid, pyromellitic acid and trimellitic acid, and the like Anhydrides, 1-phenyl-5-mercaptotetrazole compounds in which the phenyl group is substituted by a substituent with an optionally substituted aryl group, 1- (5-mercapto-1-tetrazolyl) -acetyl compounds of the formula (IV):

wherein R ^{15 is} an -NR ¹⁶ R ¹⁷ group, an -OR ¹⁸ group or an optionally substituted aryl group or heteroaryl group, wherein R ^{16 is} a hydrogen atom or an optionally substituted alkyl group, aryl group or heteroaryl group, R ^{17 is} an optionally substituted aryl group or Heteroaryl group and R ^{18 is} an optionally substituted aryl group, and compounds having two or more groups of formula (V):

wherein Q is the atom needed to form a 5- or 6-membered unsaturated heterocyclic ring, A is a hydrogen atom or a counterion to balance the negative charge of the thiolate group, or two or more A groups are a linking group between the two or more groups of the formula (V).

To a fourteenth embodiment the substantially light-insensitive monochrome black-and-white single-sheet recording material contains the heat sensitive Element further at least one optionally substituted aliphatic or carbocyclic polycarboxylic acid and / or a polycarboxylic anhydride in a molar ratio of at least 15 mol%, based on the total amount of the organic silver salt (s) and in a thermally effective relationship thereto. The polycarboxylic acid can 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 contain. Suitable dispersants are natural polymeric substances, synthetic polymeric substances and finely divided powders, for example finely divided non-metallic inorganic powders such as silica. you has found that the addition of a silicone oil in the coating solution of the Copolymer of the barrier layer solution imparts improved network characteristics.

According to a fifteenth embodiment of the substantially light-insensitive thermographic Black and white single-sheet recording material, the barrier layer contains a silicone oil.

carrier

To a sixteenth embodiment of the invention essential light-insensitive monochrome monochrome thermographic recording material the carrier translucent or translucent, and is preferably a thin flexible carrier sheet transparent resin, e.g. from a cellulose ester, e.g. cellulose triacetate, Polypropylene, polycarbonate or polyester, e.g. Polyethylene terephthalate. The carrier may be in the form of a bow, ribbon or web and subbed, if necessary, for adhesion to the thermosensitive element applied thereto improve. The carrier can colored or pigmented to the image with a translucent stained background to provide.

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 layer no. 01 on the emulsified carrier side has the following composition:

Ingredients of the heat-sensitive Elements except the above 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,
• R03 = ethyl 3,4-dihydroxybenzoate,

stabilizers:

• S01 = glutaric acid
• SO 2 = tetrachlorophthalic anhydride
• S03 = benzotriazole
• S04 = adipic acid

Compositions of the heat-sensitive elements used:

Ingredients of the barrier layers:

ingredients the protective layer:

• ERCOL ^TM 48 20 = a polyvinylalcohol from ACETEX EUROPE, LEVASIL ^™ VP AC 4055 = a 15% aqueous dispersion of colloidal silica having predominantly neutralized with sodium ions acid groups and a specific surface area of 500 m ² / g of BAYER AG / was converted to the ammonium salt .
• ULTRAVON ^™ W = 75-85% concentrate of a sodium aryl sulphonate from Ciba Geigy, converted to a Acid after passage through an ion exchange column,
• SYLOID ^TM 72 = Silica from Grace,
• SERVOXYL ^TM VPDZ 3/100 = a mono [isotridecyl polyglycol ether (3 EO)] 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 to 24 and EXAMPLES OF THE INVENTION 1 to 31

• ERCOL^TM 48 20 = 2,1 g/m²
• LEVASIL^TM VP AC 4055 = 1,05 g/m2
• ULTRAVON^TM W = 0,075 g/m²
• SYLOID^TM 72 = 0,09 g/m²
• SERVOXYL^TM VPDZ 3/100 = 0,075 g/m²
• SERVOXYL^TM VPAZ 100 = 0,075 g/m²
• MICROACE TALC P3 = 0,045 g/m²
• RILANIT^TM GMS = 0,15 g/m²
• TMOS = 0,87 g/m² (bei vollständiger Umsetzung von TMOS in SiO₂)

The substantially light-insensitive thermographic materials of COMPARATIVE EXAMPLES 1 to 24 and INVENTION EXAMPLES 1 to 31 are prepared by coating a dispersion containing the following ingredients of the Type 1 thermosensitive element in 2-butanone on a 175 μm blue-pigmented polyethylene terephthalate support, the support comprising a CIELAB a * value of -9.5 and 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 thermosensitive elements of type 1 are obtained (composition: see above). The type 1 thermosensitive elements are then coated with a barrier layer from a 2-butanone solution. For the type of copolymer used and the coating weight, see Tables 1A and 1B. The barrier layers are then coated in a wet layer thickness of 85 μm with an aqueous composition containing the following ingredients with a pH adjusted to 3.8 with 1N nitric acid and the coating is dried for 15 minutes at 50 ° C., with a L-protective layer having the following composition is obtained:

• ERCOL ^™ 48 20 = 2.1 g / m ²
• LEVASIL ^TM VP 4055 = 1.05 g / m2
• ULTRAVON ^™ 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 ^™ 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 to 24 and INVENTION EXAMPLES 1 to 31 are used in a DRYSTAR ^™ 4500 printer of 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 (Dmax) measured behind a visible light filter with a MACBETH ^™ TR924 densitometer are all greater than 2.0.

Evaluation of Diffusion of Ingredients and Reaction Products of the Image Forming Element Process to the Surface of the Protective Layer The diffusion of ingredients and reaction products of the image forming element process to the surface of the protective layer is evaluated visually according to a scale of 0 to 5 according to the following criteria:

• * ohne Schutzschicht

Tabelle 1B:

• * ohne Schutzschicht/der Druck erfolgt mit einer dünnen Folie zwischen dem wärmeempfindlichen Element und dem Thermokopf des Druckers
• # Beschichtung aus einer wässrigen Lösung

The results for both non-printed and printed materials after various periods under ambient conditions (25 ° C) are listed in Table 1A below for COMPARATIVE EXAMPLES 1 to 24 and in Table 1B below for INVENTION EXAMPLES 1 to 31. Table 1A:

• * without protective layer

Table 1B:

• * no protective layer / the print is made with a thin film between the heat-sensitive element and the thermal head of the printer
• # Coating from an aqueous solution

The Results of COMPARATIVE EXAMPLE 1 show that it is a very considerable Diffusion of ingredients and reaction products of the imaging element process to the surface the protective layer gives, even on the non-printed material. The results of COMPARATIVE EXAMPLE 2 show that the protective layer based on the reaction product of polyvinyl alcohol with hydrolyzed Tetramethoxysilane is capable of further diffusion to the surface of the Protect protective layer of non-printed material. To However, the printing process is a considerable after 20 days of storage Diffusion of ingredients and reaction products of the imaging element process to observe.

From the results of COMPARATIVE EXAMPLES 3 to 24, it can be seen that the ability of barrier layers containing non-inventive polymers Nos. 1 to 21 to prevent diffusion to the surface of the protective layer is inferior to the result without barrier layer. It is to be noted that Polymers Nos. 1 to 4 are used in combination with a protective layer based on the reaction product of polysilicic acid and a hydroxyl-containing polymer according to U.S. Pat US 5,264,334 ensure a proper barrier to the diffusion of ingredients.

On the other hand, from the results of INVENTION EXAMPLES 1 to 31, it can be seen that the copolymers of the present invention Nos. 1 to 3, 6 to 8 and 11 to 14 when used in a ratio of less than 0.25 g / m ² to over 2 g / m ^{2 are} unexpectedly able to prevent the diffusion of ingredients and reaction products of the imaging process to the surface of the protective layer over a period of 30 days under ambient conditions (25 ° C) before and after the printing cycle.

These Copolymers can in copolymers with vinyl chloride units and vinyl acetate units (Copolymers Nos. 1 to 3), copolymers with styrene units and acrylonitrile units (Copolymers Nos. 6 to 8), copolymers with cationic units (Copolymers Nos. 11 to 13) and styrene-maleic acid copolymers (copolymer no. 14).

COMPARATIVE EXAMPLES 25 to 29 and INVENTION EXAMPLES 32 to 38

The essentially light-insensitive thermographic materials of the COMPARATIVE EXAMPLES 25 to 29 and INVENTIVE EXAMPLES 32 to 38 will be like for COMPARATIVE EXAMPLES 1 to 24 and INVENTION EXAMPLES 1 to 31 described except those in the tables 2A and 2B for COMPARATIVE EXAMPLES 25 to 29 and INVESTIGATIVE EXAMPLES, respectively 32 to 38 mentioned Barrier layers.

The Diffusion of ingredients and reaction products of the imaging process to the surface the protective layer in COMPARATIVE EXAMPLES 25 to 29 and INVENTIVE EXAMPLES 32 to 38 will be like for COMPARATIVE EXAMPLES 1 to 24 and INVENTION EXAMPLES 1 to 31 described before and after the printing cycle evaluated. The Results of the diffusion experiments are also listed in Table 2.

The Results of the diffusion experiments in Table 2 confirm the Findings of the INVENTION EXAMPLES 1 to 31, i. Copolymers 1 to 3 and 6 to 8 are capable of the diffusion of ingredients and reaction products of the imaging process to the surface the thermographic material both before and after the printing cycle over a Period of 30 days under ambient conditions (25 ° C).

Table 2:

Evaluation of thermographic properties

In order to a barrier layer for use in substantially light-insensitive thermographic materials, it is important that she is not only capable of the diffusion of ingredients and reaction products of the image forming process to the surface of the Restrict protective layer, but also no adverse effect on the image of the deductions having.

Of the Picture tone fresher, with the substantially light-insensitive thermographic Recording Materials of COMPARATIVE EXAMPLES 25 to 29 and the INVENTION EXAMPLES 32 and 38 printed prints is based on the CIELAB values L *, a * and b * in an optical Density D of 1.0 and 1.5 evaluated. The results of the evaluation are listed in Table 3.

Out It can be seen from the results in Table 3 that barrier layers, Copolymer Nos. 1 to 3 and 6 to 8 contain the CIELAB b * values fresh thermobonding materials containing barrier layers deductions slightly negative towards the corresponding thermographic material of the COMPARATIVE EXAMPLES 25 and 26. This makes a more acceptable for a radiologist Image tone received.

Table 3:

COMPARATIVE EXAMPLE 30 and INVENTION EXAMPLES 39 to 50

The essentially light-insensitive thermographic materials of the COMPARATIVE EXAMPLE 30 and the INVENTION EXAMPLES 39 to 50 are made by order one of the ingredients of the heat-sensitive Elements of type 2 in 2-butanone-containing dispersion on a 175 μm thick blue pigmented polyethylene terephthalate support, wherein the carrier a CIELAB a * value of -9.5 and a CIELAB b * value of -17.9 and coated on its emulsion side with adhesive layer 01 is. After 3 minutes Drying at 85 ° C in a drying oven become heat-sensitive Elements of type 2 obtained (composition of heat-sensitive Elements of type 2: see above). The heat-sensitive elements of the Type 2 will follow from a 2-butanone solution coated with a barrier layer. For the Type of copolymer used and the coating weight is on table 4 referenced. Subsequently Coating the barrier layers with the same protective layer as with the substantially light-insensitive thermographic materials COMPARATIVE EXAMPLES 1 to 24 and the EXAMPLES OF THE INVENTION 1 to 31.

The diffusion of ingredients and reaction products of the imaging process to the surface of the protective layer in COMPARATIVE EXAMPLE 30 and the INVENTION EXAMPLES 39 to 50 is evaluated as described for COMPARATIVE EXAMPLES 1 to 24 and INVENTION EXAMPLES 1 to 31 after 3, 6, 9, 12, 15 and 18 day storage of the prints at 57 ° C and 34% RH. This test provides a more rigorous test of the ability of these barrier layers to confine the diffusion of ingredients and reaction products of the imaging process to the surface. The results of these diffusion experiments are also listed in Table 4.

Table 4:

From the results in Table 4, it can be seen that the barrier layers containing copolymer No. 2, a vinyl chloride-vinyl acetate-maleic anhydride copolymer, even under these severe conditions, provide excellent confinement of the diffusion of ingredients and reaction products of the image forming process to the surface Also, the barrier layers containing copolymer No. 7, a styrene-acrylonitrile copolymer, under these conditions satisfactorily restricts diffusion of ingredients and reaction products of the imaging process to the surface.

Evaluation of thermographic properties

In order to a barrier layer for use in substantially light-insensitive thermographic materials, it is important that she is not only capable of the diffusion of ingredients and reaction products of the image forming process to the surface of the Restrict protective layer, but also no adverse effect on the image of the deductions having.

Of the Picture tone fresher, with the substantially light-insensitive thermographic Recording materials of COMPARATIVE EXAMPLE 30 and the INVENTIVE EXAMPLES 39 to 50 printed prints is based on the CIELAB values L *, a * and b * in an optical Density D of 1.0 and 1.5 evaluated. The results of the evaluation are listed in Table 5.

Table 5:

It can be seen from the results in Table 5 that barrier layers containing Copolymer Nos. 2 and 7 obtain the CIELAB b * values of fresh thermobonding materials containing barrier layers slightly more negative than the corresponding thermographic material of COMPARATIVE EXAMPLE 30. This provides a more acceptable image tone for a radiologist. Furthermore, it has been found that the achievable D _max value for a given barrier layer ratio decreases as the wet layer thickness decreases, ie as the ratio of the copolymer in the coating solution increases. A wet layer thickness of more than 30 μm has no further influence on D _max at copolymer ratios of less than 0.4 g / m ² and a wet layer thickness of 20 μm is possible at copolymer ratios of less than 0.3 g / m ² .

COMPARATIVE EXAMPLE 31 and INVENTION EXAMPLES 51 to 62

• * Beschichtung aus einer wässrigen Lösung bei einem pH von 3,8
• # Beschichtung aus einer wässrigen Lösung bei einem pH von 7

The substantially light-insensitive thermographic materials of COMPARATIVE EXAMPLE 31 and INVENTION EXAMPLES 51-62 are prepared as described for COMPARATIVE EXAMPLE 30 and INVENTION EXAMPLES 39-50, except that Type 2 thermosensitive elements and those mentioned in Table 6 are used Barrier layers are used. Table 6:

• Coating from an aqueous solution at a pH of 3.8
• # Coating from an aqueous solution at a pH of 7

The Diffusion of ingredients and reaction products of the imaging process to the surface the protective layer in COMPARATIVE EXAMPLE 31 and in the EXAMPLES OF THE INVENTION 51 to 62 will be like for COMPARATIVE EXAMPLES 1 to 24 and INVENTION EXAMPLES 1 to 31 described after 3 days Storage of prints at 57 ° C and 34% relative humidity. The results are also listed in Table 6.

When using the barrier layers containing the copolymers Nos. 2 to 7, 9 to 12 and 14 in a ratio of 1 g / m ² , no diffusion of ingredients and reaction products of the image forming process to the surface is observed. The majority of these barrier layers are applied from 2-butanone solutions, but the application of the barrier layers containing the copolymers Nos. 11, 12 and 14 takes place from aqueous solutions. These copolymers can be mainly divided into copolymers with vinyl chloride units and vinyl acetate units (copolymer Nos. 1 to 5), copolymers with styrene units and acrylonitrile units (copolymer Nos. 6 to 10) and copolymers with cationic units (copolymers Nos. 11 and 12).

evaluation thermographic properties

• * Beschichtung aus einer wässrigen Lösung bei einem pH von 3,8
• # Beschichtung aus einer wässrigen Lösung bei einem pH von 7

The image tone fresher, with the substantially light-insensitive thermographic recording materials of COMPARATIVE EXAMPLE 31 and the INVENTIVE EXAMPLES 51 to 62 of printed prints, is calculated on the basis of the CIELAB values L *, a * and b * at an optical density D of 1.0 and 1 , 5 evaluated. The results of the evaluation are listed in Table 7. Table 7:

• Coating from an aqueous solution at a pH of 3.8
• # Coating from an aqueous solution at a pH of 7

Out It can be seen from the results in Table 7 that certain barrier layers, Copolymer Nos. 2 to 7, 9 to 12 and 14 contain CIELAB b * values of fresh thermobonding materials containing barrier layers obtained deductions slightly negative towards the corresponding thermographic material of the COMPARATIVE EXAMPLE 31 (e.g., barrier layers, Copolymer Nos. 2-7 and 9 and 10), which improves the picture tone and other barrier layers slightly increase the CIELAB b * values make opposite the corresponding thermographic material of the COMPARATIVE EXAMPLE 31 (e.g., barrier layers, Copolymer Nos. 11, 12 and 14 contained and all three from aqueous solutions are applied).

The Composition of the barrier layers, the copolymers with vinyl chloride and vinyl acetate units in different weight percentages of Vinyl chloride and vinyl acetate units (copolymer no. 2 to 5) has no noticeable influence on the picture tone, i. at a weight percentage of vinyl chloride units between 60 and 91 and at a weight percentage of vinyl acetate units between 3 and 15.

The Composition of the barrier layers, the copolymers with styrene and Acrylonitrile units in different weight percentages of Styrene and acrylonitrile (Copolymer Nos. 6, 7, 9 and 10), has no appreciable effect on the picture tone, i. at a weight percentage of styrene units between 54 and 75 and at a weight percentage of acrylonitrile units between 25 and 46.

COMPARATIVE EXAMPLES 32 to 39 and INVENTION EXAMPLES 63 to 74

The essentially light-insensitive thermographic materials of the COMPARATIVE EXAMPLES 32 to 39 and the EXAMPLES OF THE INVENTION 63 to 74 are made by applying dispersions containing the ingredients for the respective type of heat-sensitive Element contained in 2-butanone (see Table 8 for the in the various COMPARATIVE or INVENTIVE EXAMPLES Type of heat-sensitive Element) on the for COMPARATIVE EXAMPLES 1 to 24 and the INVENTION EXAMPLES 1 to 31 described carrier prepared, after 3minütiger Drying at 85 ° C in a drying cabinet for each COMPARATIVE or INVENTIVE EXAMPLE is a particular one Type of heat-sensitive Element is obtained. If necessary, the heat-sensitive Elements then coated from a 2-butanone solution with a barrier copolymer (See Table 8 for the type of copolymer and the coating weight). The barrier layers are subsequently with the same protective layer as with the substantially light-insensitive thermographic materials of COMPARATIVE EXAMPLES 1 to 24 and the INVENTION EXAMPLES 1 to 31 coated.

• ° TWE: Typ von wärmeempfindlichem Element
• * ohne Schutzschicht/der Druck erfolgt mit einer dünnen Folie zwischen dem wärmeempfindlichen Element und dem Thermokopf des Druckers

The diffusion of ingredients and reaction products of the imaging process to the surface of the protective layer in COMPARATIVE EXAMPLES 32 to 39 and INVENTION EXAMPLES 63 to 74 is described as for COMPARATIVE EXAMPLES 1 to 24 and INVENTION EXAMPLES 1 to 31 after testing for fresh material and prints evaluated in different tests: 3 days and 6 days at 57 ° C and 34% relative humidity and 7 days at 45 ° C and 70% relative humidity. The results are listed in Table 8. Table 8:

• ° TWE: Type of heat-sensitive element
• * no protective layer / the print is made with a thin film between the heat-sensitive element and the thermal head of the printer

From the experiments mentioned in Table 8 it can be seen whether the barrier layers according to the invention can be used with a variety of thermosensitive elements of different composition. From the barrier layers containing copolymer No. 6 in a 0.79 g / m ² ratio, it can be seen that this barrier layer provides excellent confinement of the diffusion of ingredients and reaction products of the imaging process to the surface of the thermographic material. The results for INVENTIVE EXAMPLES 63 to 67, 69, 71 and 73 further show that the bare barrier layer ensures this limitation, which means that the selection of the protective layer does not play a critical role in limiting the diffusion of ingredients and the design of the protective layer can be tuned only to optimize the mechanical interaction between the thermal print head and the adhesion to the barrier layer.

Claims (10)

A substantially light-insensitive monochrome black-and-white single-sheet recording material having a support and on one side of the support a heat-sensitive element, a barrier layer and an outer protective layer, wherein the heat-sensitive element is not a strong contrast agent, but at least one substantially light-insensitive silver salt of a carboxylic acid, at least one thermal reducing agent therefor effective relationship thereto, at least one tinting agent and at least one binder, characterized in that the at least one reducing agent is an ortho-dihydroxybenzene derivative and the barrier layer is a copolymer having vinyl chloride units and vinyl acetate units and / or vinyl alcohol units, a copolymer having styrene units and acrylonitrile units Copolymer with cationic units and / or a copolymer containing styrene units and maleic acid units. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 1, characterized in that the barrier layer between the heat sensitive Element and the outer protective layer is present. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 1 or 2, characterized in that the copolymer with Vinyl chloride units and vinyl acetate units up to 95% by weight Contains vinyl chloride. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 1 or 2, characterized in that the copolymer with Styrene units and acrylonitrile units between 20 and 60% by weight Contains acrylonitrile. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 1 or 2, characterized in that the copolymer with cationic units quaternary ammonium units, quaternary Phosphonium units or ternary Contains sulfonium units. Substantially light-insensitive thermographic Black and white single sheet recording material behind Claim 5, characterized in that the quaternary ammonium units Methacrylamidpropyltrimethylammoniumchlorideinheiten or dimethyldiallylammonium chloride units. Substantially light-insensitive black and white monosheet thermographic recording material according to any one of the preceding claims, characterized in that the tinting agent is selected from the group consisting of naphthoxazinedione, naphthoxazine dione derivatives, 7-methyl-benzo [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. Substantially light-insensitive thermographic Black and white single sheet recording material behind one of the preceding claims, characterized in that the ortho-dihydroxybenzene derivative is selected from the group consisting of catechol, 3- (3,4-dihydroxyphenyl) propionic acid, 3,4-dihydroxybenzoic acid, 3,4 Dihydroxybenzosäureestern, Gallic acid, Gallussäureestern, 3,4-dihydroxybenzaldehyde, 3,4-dihydroxyacetophenone, 3,4-butyrophenone, 3,4-dihydroxybenzophenone, 3,4-dihydroxybenzophenone derivatives, 3,4-dihydroxybenzonitrile and tannic acid chosen becomes. Substantially light-insensitive thermographic Black and white single sheet recording material behind one of the preceding claims, characterized in that the outer protective layer is the reaction product of at least one hydrolyzed polyalkoxysilane and a hydroxyl-containing one Contains polymer. Substantially light-insensitive thermographic Black and white single sheet recording material behind one of the preceding claims, characterized in that the outer protective layer is the reaction product of a hydrolyzed tetraalkoxysilane, e.g. tetramethoxysilane or tetraethoxysilane, and polyvinyl alcohol.