MXPA97002044A

MXPA97002044A - Thermographic elements addressable with the

Info

Publication number: MXPA97002044A
Application number: MXPA/A/1997/002044A
Authority: MX
Inventors: E Bills Richard; C Weigel David
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1994-09-27
Filing date: 1997-03-18
Publication date: 1997-06-01

Abstract

A thermographic imaging element contains a substrate that is coated on at least one surface with a thermographic imaging system having at least one layer containing organic track salt insensitive to light, reducing agent for ion-track, a binder organic pigment and a dye that absorbs radiation in the wavelength range from about 750 to 1100 nm. Preferably, there is a layer adjacent to that which contains the organic silver salt insensitive to light, etc., which contains additional binder and dye which absorbs radiation in the range of about 750 to 1100 nm. When the thermographic image element is exposed to radiation from 750 to 1100 nm from 0.10 to 2.0 Joules / cm2 by 0.20 to 200 microseconds, an image density of approximately 1.0 or greater is formed. When an image is formed in a thermographic imaging element with the radiation-absorbing dye in both adjacent layers or only in the binder-containing and dye-containing layer, the radiation is directed through the layer containing the organic silver salt insensitive to light, etc., before incising the adjacent layer containing radiation-absorbing dye and agglutinate

Description

THERMO-DIRECT THERMOGRAPHIC ELEMENTS WITH LASER Field of the Invention The present invention relates to novel thermographic image forming elements and more particularly relates to thermographic image forming elements, which can be formed directly in image using an infrared laser diode. The present invention also relates to processes for forming in image the inventive thermographic image forming elements using an infrared laser diode. BACKGROUND OF THE INVENTION In image forming techniques, image forming elements that can be imaged by light or heat are well known. Photographic and conventional photographic elements of silver halide are the most representative elements of the class of light-sensitive materials. Both conventional photographic elements ("wet silver") and photothermographic ("dry silver") exposure of the silver halide in the photosensitive emulsion to light produces small swarms of silver atoms (Ag °). The image-like distribution of these swarms are known in the art as a latent image. In general, the formed latent image is not visible by ordinary means and the photosensitive emulsion must be further processed in order to produce a visible image. In both wet and dry silver systems, the visible image is produced by the reduction of silver ions that are in catalytic proximity with silver halide grains that contain the swarms of the silver atoms, ie the latent image. This produces a black-and-white image. Conventional photographic silver halide elements require a wet development process to make the latent image visible. The wet chemistry used in this process requires special handling and disposal of spent chemical products. The process equipment is large and requires special plumbing. In the photothermographic elements, the photographic silver halide is in catalytic proximity with a reducible and non-photosensitive silver source (for example silver behenate), such that when the silver nuclei are generated by exposure to the light of the halide of silver, those cores are able to catalyze the reduction of the reducible silver source. The latent image becomes visible by applying uniform heat through the element. Thermal devices used to reveal photothermographic elements solve the problems in conventional photographic elements when using a dry process. However, the photothermographic elements developed using these devices may have a heterogeneous or non-uniform image density, image distortions and / or surface abrasion defects. Defects due to non-uniform image density can occur during the development process due, for example, to surface variations in the heated member, the presence of foreign matter in the photothermographic element or heated element, and insufficient tolerance for gas evolution of materials volatile generated during development. Image distortions may occur due to uncontrolled dimensional changes at the base of the photothermographic element during heating and / or cooling of the photothermographic element. Abrasions or superficial injuries may occur by dragging the photothermographic element through a stationary component in the heating device. In many applications, such as text and line drawings, these defects may be acceptable. However, users of medical diagnostics, industrial, graphic arts, printed circuit boards and other imaging applications want images with uniform and high quality. The patent of the U.S.A. No. 5,041,369 describes a process that capitalizes on the advantages of the dry processed photothermographic element, without the need for surface contact as a heating device. The photothermographic element is exposed as an image with a laser that divides the beam using a second harmonic generation device. In this process, the element is simultaneously exposed with a wavelength of light and thermally activated by the absorption of a near-infrared light-to-heat (NIR) dye at the second wavelength of light. Even though this process has the simultaneous exposure and thermal development of the image, the required equipment is complex and limited by laser outputs capable of generating two useful separated wavelengths. In addition, the photosensitive emulsion still requires that both light and heat activation generate an image. Photosensitive emulsions containing silver halides are well known in the art capable of causing high minimum density (Dmln) in both the visible and ultraviolet (UV) portions of the spectrum. The high UV Dmln is due to the inherent absorption in the near UV of silver halides, particularly silver bromide and silver iodide, and to high veil when salts of organic silver and silver halide are present as a whole. It is undesirable to high-UV DBL for graphic arts scanner and image adjustment films, since it increases the exposure time required during exposure of contacts with other media such as UV-sensitive printing plates, test films and papers. High veil can also lead to loss of image resolution when photothermographic elements formed in image are used as contact films. It is also well known that silver halides in photothermographic elements can lead to deficient light stability of the background image density leading to veiling. A class of image-forming elements that are not based on chemistry based on silver halides are thermographic elements. These materials are widely used in fax machines, labels, tickets, diagrams to record the output of a scientific medical verification device and the like. In the most common form, the thermographic element comprises a support carrying a coating of a thermally sensitive composition, comprising a color former, usually a substantially colorless electron donor dye precursor, and a color developer, usually an acceptor compound of electrons The heat is applied as an image to the element by means of a thermal head, a thermal pen OR a laser beam, and in the case of image-applied heating, the color former instantaneously reacts with the color developer to form an image. The U.S. Patent No. 4,904,572 discloses a thermographic element employing leuco dyes to improve the developed image. A leuco dye is the reduced form of a dye that contains color. In general it is colorless or of a very clear color. In this application, the silver behenate acts as a Lewis acid that reacts with the leuco dye before heat imaging to form a color image. An image of black is achieved by the combination of subtractive colors (light blue, yellow and magenta). It is well known in the art that it is very difficult to achieve a high density neutral tone black, using subtractive colors. Since the image is generated by color pigment formation the absorption of the image in the ultraviolet is weak and therefore provides very little utility as a UV masking film. Conventional thermal films typically require residence times for image formation from one to five seconds. The processing times of this extension are not practical in a laser imaging application. In order to provide an appropriate imaging residence time for a laser addressable system, there is a need for a thermographic film construction that is capable of forming an image in itself in micro seconds. Each of the aforementioned classes of image-forming elements has some disadvantage. For example, conventional silver halide photographic materials have high environmental impact due to the wet processing chemistry; photothermographic materials have less firmness in image light, limited optical density, and poor dimensional stability; in silver halide based emulsions typically use visible sensitizers that require being leached or removed and require handling in dark or dim light; both photographic and conventional photothermographic elements require a two-stage process (exposure and development); and conventional thermographic elements require high imaging energy, residence times for relatively long thermal imaging, and have less firmness to light before image and limited to UV optical density. What is required in the industry are elements and processes of image formation that help overcome the problems described above. It was against this background that the present inventions were developed. In one embodiment, the present invention provides a thermographic imaging element comprising a substrate having coated on at least one surface, a thermographic imaging system comprising at least one layer consisting of an insensible organic silver salt. to the light; reducing agent for silver ion; the binder; organic pigment and a dye that absorbs radiation in the wavelength range of about 750-1100 nm, wherein the layer at least comprises the organic silver salt insensitive to light which forms an image density greater than about 1.0, when it is exposed to 0.10-2.0 joules / cm2 of radiation (having a wavelength in the range of approximately 750 to 1100 nm) in 0.2 to 200 microseconds. In another embodiment, the present invention provides a thermographic imaging element comprising a coated substrate, a thermographic imaging system, the thermographic imaging system comprising at least two adjacent layers, one of the adjacent layers comprising silver salt organic insensitive to light; reducing agent for silver ion; the binder; organic pigment and optionally a dye that absorbs radiation in the wavelength range of about 750-1100 nm, and the other adjacent layer consists essentially of dye that absorbs radiation at the wavelength in the range of about 750 to 1100 nm, and binder such that the layer comprises the organic silver salt insensitive to light which forms an image density greater than about 1.0, when exposed to 0.10-2.0 joules / crn * of radiation (having a wavelength in the range of approximately 750 to 1100 nm) in 0.2 to 200 microseconds. In a further embodiment, the present invention provides a process for forming an image comprising the step of exposing a thermographic image forming element, comprising a substrate coated with a thermographic image forming system, consisting of at least one layer comprising organic silver salt insensitive to light; reducing agent for silver ion; a binder; a dye that absorbs radiation in the wavelength range of about 750-1100 nm; and organic pigment, to radiation in the range of about 750-1100 nm, such that the layer at least comprises the organic silver salt insensitive to light which forms an image density greater than about 1.0, when exposed to 0.10. -2.0 joules / cm2 of radiation (having a wavelength in the range of approximately 750 to 1100 nm) in 0.2 to 200 microseconds.

In yet another embodiment, the present invention provides a method for forming an image comprising the step of exposing a thermographic imaging element comprising a substrate coated with a thermographic imaging system, the thermographic imaging system comprising at least two adjacent layers, one of the adjacent layers comprises organic silver salt insensitive to light; reducing agent for silver ion; the binder; organic pigment and optionally a dye that absorbs radiation having a wavelength in the range of about 750-1100 nm, and the other adjacent layer consists essentially of binder and dye that absorbs radiation having a wavelength in the range of about 750 to 1100 nm, to radiation having a wavelength in the range of about 750 to 1100 nm, which is directed to the thermographic imaging element through the layer comprising the organic silver salt insensitive to light before incising the adjacent layer which essentially consists of binder and dye, such that the layer comprises the organic silver salt insensitive to light which forms an image density greater than about 1.0 when exposed to 0.10-2.0 joules / cm2 of radiation ( which has a wavelength in the range of approximately 750 to 1100 nm) in 0.2 to 200 microseconds. In a preferred embodiment of the above inventions, an image density greater than about 2.00 and more preferably greater than about 2.50, and more preferably greater than about 2.75, comprising metallic silver, is formed in the layer consisting of the silver salt organic insensitive to light, reducing agent, etc., upon exposure to 0.10-2.0 joules / cm2 of radiation (which has a wavelength in the range of approximately 750 to 1100 nm) in 0.2 to 200 microseconds. The layers ("thermographic silver emulsion layers") comprise organic silver salt insensitive to light, reducing agent for silver ion, etc., in all the above-described embodiments of the present invention, they may incorporate up to about 1.0% by weight of Silver halide, based on the total weight of the silver. The silver-based thermographic image forming elements and methods for using the thermographic image forming elements, such as direct laser-addressable writing film, which is provided by the present invention, overcome many of the problems seen in current systems. Since the thermographic image forming element is thermally sensitive instead of photosensitive, it is operable in white light, and does not require removal of a visible sensitizer. Unlike photothermographic and wet silver elements, no further processing steps are required for image development. When a high-energy laser diode is scanned through the thermographic imaging element, a black on-site image is printed on the thermographic silver emulsion, thus allowing many useful applications such as online mask inspection system of photo tool for printed circuit boards. In addition, the The thermal shrinkage of the film is minimized since only the image portion of the emulsion is heated and the temperature of the substrate relatively unchanged. This is especially important for applications where registration is critical, such as image-setting films for color reproduction and photo-printed circuit board tools. In addition, thermographic image forming element is capable of producing high resolution halftone images that are useful in color reproduction processes. Other aspects, advantages and benefits of the present invention will be apparent from the detailed description, examples, drawings and claims.

Figure 1 shows a schematic representation of a laser sensor etro. Figure 2 shows a plot of distance versus the relative intensity of a laser diode comparing the traces for theoretical profile data against current for a laser point in the form of a cone with a flat lid in a film plane.

Figure 3a shows a plot of the total incident exposure energy plotted against the distance through the laser beam in the transverse direction / scan. Figure 3b illustrates a micro-densite profile of a line formed in image with an energy profile illustrated in Figure 3a on a thermographic element. (Example 16 shows N is not illustrated). Figure 4 shows a plot of density against the log of the exposure using the data illustrated in Figure 3a. Figure 5 shows a graph of absorption versus wavelength, comparing the image-formed and non-image-formed areas of a thermographic image-forming element. (Example 16 shows N is not illustrated). Description of the Invention As used herein, "thermographic image forming element" refers to a substrate coated on at least one surface with a "thermographic image forming system". The thermographic image forming system comprises at least one thermographic silver emulsion layer containing organic silver salt insensitive to light; reducing agent para-silver; binder; organic pigment of a dye that absorbs radiation with a wavelength in the range of about 750 to 1100 n. Additionally, the thermographic image forming system may comprise a layer adjacent to the thermographic silver emulsion layer containing additional dye, radiation absorber and binder. In the present invention, the thermographic silver emulsions that are employed comprise a silver salt insensitive to light; a para-silver reducing agent; a dye that absorbs radiation, having a wavelength in the range of about 750 to 1100 nm; a pigment, a binder; and an optional development accelerator. Light-insensitive silver salts are materials, which in the presence of a reducing agent are subjected to reduction at elevated temperatures, for example 60 ° -225 ° C, to form silver metal. Preferably, these materials are silver salts of long chain alkanoic acids (also known as fatty acids or long chain aliphatic carboxylic acids) containing from 4 to 30 carbon atoms; more preferably 8 to 28 carbon atoms; and in particular 10 to 22 carbon atoms. The latter are also known in the art as "silver soaps". Non-limiting examples of silver salts of aliphatic carboxylic acids include silver behenate, silver stearate, silver oleate, silver erucate, silver laurate, silver caproate, silver myristate, silver palmitate, silver maleate, silver, silver tartrate, silver linoleate, silver camphor, and their mixtures. Complexes of organic or inorganic silver salts where the ligand has a net stability constant between 4.0 to 10.0 can also be used. Silver salts of aromatic carboxylic acids and other carboxyl group-containing compounds include silver benzoate, a substituted silver benzoate such as silver 3,5-dihydroxybenzoate, silver o-methylbenzoate, silver m-methylbenzoate, p-methylbenzoate. silver, silver 2,4-dichlorobenzoate, silver idobenzoate acetates, silver p-phenylbenzoate, etc, silver gallate, silver tannate, silver phthalate, silver terephthalate, silver salicylate, silver phenylacetate, pyromelite silver, silver salts of 3-carboxymethyl-4-methyl-thiazoline-2-thiones or the like as described in the US Pat. No. 3,785,830; and silver salts of aliphatic carboxylic acids containing a thioether group as described in U.S. Pat. No. 3,330,663. Silver salts of compounds containing mercapto or thione groups and their derivatives can also be used. Preferred examples of these compounds include 3-mercapto-4-phenyl-1, 2,4-triazolate of silver, 2-mercaptobenzimidazolate of silver, 2-mercapto-5-aminothiadilizolato of silver, 2- (S-ethylglycolamido) benzothiazolate of silver; silver salts of thioglycolic acids such as silver salts of S-alkyl thioglycolic acids (wherein the alkyl group has from 12 to 22 carbon atoms); dithiocarboxylic acids such as silver dithioacetate, silver thioamidate, silver l-methyl-2-phenyl-4-thiopyridine-5-carboxylate, silver triazintiolate, silver 2-sulfidobenzoxazole; and silver salts as described in U.S. Pat. No. 4,123,274. In addition, silver salts of a compound containing an amino group can be used. Preferred examples of these compounds include silver salts of benzotriazoles, such as silver benzotriazolate; silver salts of alkyl-substituted benzotriazoles such as silver methylbenzotriazolate, etc .; silver salts of benzotriazolates substituted with halogen such as silver 5-chlorobenzotriazolate, etc .; silver salts of carboimidobenzotriazoles, etc; silver salts of 1,2,4-triazoles and 1-f-tetrazoles as described in U.S. Pat. No. 4,220,709; silver salts of imidazoles; and similar. Preferably, the light-insensitive silver salt material should be from about 5 to 7% by weight and more preferably from about 30% to 50% by weight, based on the total weight of the thermographic silver emulsion layer . Any reducing agent for silver ion can be used in the present invention. These reducing agents are well known to those skilled in the art. Examples of these reducing agents include, but are not limited to methyl gallate; hindered phenols; catechol; pyrogallol; hydroquinones; substituted hydroquinones; ascorbic acid; ascorbic acid derivative; leuco dyes; and similar. The most preferred reducing agents are methyl gallate, butyl gallate, and propyl gallate. Any reducing agent that was employed in the present invention, preferably an amount of from about 5.0 to 25.0% by weight and more preferably from about 10.0 to 20.0% by weight, based on the total weight of the silver emulsion layer is employed. thermographic Organic pigments are also used in the thermographic silver emulsion layer (s). Examples of organic pigments include phthalacinone, phthalazine, barbituric acid, succinimide and phthalimide. Combinations of organic pigments have been found especially useful, the preferred combinations are phthalazinone with barbituric acid and phthalimide with barbituric acid and more preferred is succinimide with barbituric acid. The organic pigment (s) preferably should be present in an amount in the range of about 0.2 to 10.0% by weight; more preferably about 1.0 to 8.0% by weight and in particular about 2.0 to 6.0% by weight, based on the total weight of the thermographic silver emulsion layer. Auxiliary reducing agents or development accelerators can optionally be included in the photothermographic silver emulsion layer, depending on the silver source used. Preferably, the auxiliary reducing agent comprises a 3-indazolinone or urea compound as a developing accelerator. 3-Indazolinone compounds used in the present invention preferably have the following structure: wherein R is selected from the group consisting of: hydrogen; alkyl group having from 1 to 4 carbon atoms; halogen; -COOH and -R ^ OOH, wherein R1 is an alkyl group having from 1 to 4 carbon atoms. Preferably R is a hydrogen or an alkyl group having 1 to 4 carbon atoms and more preferably R is hydrogen. These 3-indazolinone compounds can be synthesized according to procedures well known to those skilled in the synthetic organic chemistry art. In alternate form, these materials are commercially available such as from Aldrich Chemical Company of ilwaukee, W .; Lancaster Chemical Company of Windha, New Hampshire; and K &K Laboratories of Cleveland, Ohio. As is well understood in this area, a large degree of substitution is not only tolerated but often recommended. Thus, as used herein the phrase "group" is intended to include not only pure hydrocarbon substituents such as methyl or ethyl and the like, but also hydrocarbon substituents containing substituents conventional in the art such as hydroxy, alkoxy, phenyl, halo (F, Cl, Br, I) cyano, nitro, amino, etc. Urea compounds used in the present invention preferably have the following formula: II R2-NH-C-NH-R3 wherein R2 and R3 each independently represent a hydrogen; an alkyl or cycloalkyl group with 1 to 10 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 6 ring atoms. Preferably R2 and R3 represent hydrogen; an alkyl or cycloalkyl group with 1 to 5 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 5 ring atoms. These urea compounds can be easily synthesized and are commercially available. Non-limiting examples of these urea compounds include urea; 1,3-diphenylurea; 1,3-diethyl urea; butyl urea and 2-imidazolidone. The most preferred development accelerator is 2-imidazolidone. The thermographic imaging elements of the present invention are not sensitive to light in the traditional sense and therefore do not require containing photosensitive agents such as silver halides; initiating photo; or photogenerated leachate agents. The thermographic silver emulsion layers may have less than 0.5% or 0% by weight based on the total weight of the thermographic silver emulsion and perform well. The silver halide is considered ineffective if it does not catalyze the formation of a latent image. Light stabilizers such as benzotriazole, phenylmercaptotretazole and other light stabilizers known in the art can be added to the thermographic silver emulsion. The preferred light stabilizer is benzotriazole. The light stabilizer, preferably must be present in an amount in the range of about 0.1% to 3.0% by weight of the thermographic silver emulsion layer and more preferably from 0.3 to 2.0% by weight. The thermographic silver emulsion layer used in the present invention also employs a binder. Any conventional polymeric binder known to those skilled in the art may be used. For example, the binder can be chosen from any of the well-known natural and synthetic resins such as gelatin, polyvinyl acetals, polyvinyl chloride, cellulose acetate, polyolefins, polyesters, polystyrene, polyacrylonitrile, polycarbonates and the like. Copolymers and terpolymers of course include in these definitions examples of which include but are not limited to polyvinyl aldehydes, such as polyvinyl acetals, polyvinyl butyrals, polyvinyl formals and vinyl copolymers. Preferably, the binder should be present in an amount in the range of 10 to 60% by weight and more preferably 15 to 50% by weight based on the total weight of the thermographic silver emulsion layer. The thermographic element of the present invention employs a dye which absorbs electromagnetic radiation and which has a wavelength in the range of between about 750 to 1100 nm, preferably in the range of about 750 to 900 nm, and in particular in the range of about 750 to 870 nm. The dye should be soluble in the coating solvent, preferably ketones or aromatic solvents, such as methyl ethyl ketone or toluene. The dye should also be visible with the binder compatible with the activating silver salts and developers used in the emulsion. For use in UV (ultra violet) contact film or mask applications, the optical density of the dye is preferably greater than 1.0 optical density unit with a concomitant weak absorption less than 0.2 optical density unit in the corresponding UV region at wavelength to exposure devices for which the material will be used as a mask (250-450 nm). The optical density is measured using a densite etro MacBeth model TD523, equipped with a status 18A filter. It is also convenient although not necessary for the dye to have a low visible background absorption.

The radiation-absorbing dye can be used in the same layer as the organic silver salt insensitive to light; reducing agent for silver ion; organic pigment and binder. Alternatively, the colorant can be used in the anterior layer 5 as well as in an adjacent layer or primarily in the adjacent layer. The radiation-absorbing dye can be added directly to the thermographic silver emulsion layer or indirectly by allowing the dye to migrate from the adjacent layer, which contains the dye, into the dye layer.

, Thermographic silver emulsion during the manufacturing process of the thermographic image forming element. Suitable dyes include that although they are not limited to oxonol, squaryliu, chalcogenpyrillarylidene, bis (chalcogenpyryl) polymethine, bis (aminoaryl) polymethine, merocyanine, trinuclear cyanine, bridged polymethine with indene, oxyindolizine, ferrous complex, quinoid, dithiolene nickel complex, and cyanine dyes such as carboxyamine, azacarboxianin, hemicianin, styryl, diazacarboxianin, triazacarboxianin, diazahemixianin, polymethincyanin, azapolymethylazianin, holopolarindocyanine and diazahexanine dyes. The amount of dye present in the thermographic imaging element will depend on whether the dye is incorporated only in the thermographic silver emulsion layer 5 or in an adjacent layer equally. When the colorant is present only in the thermographic silver emulsion layer, the colorant will be present in an amount from 0.10 to 5.0% by weight and preferably 0.2% to 3.0% by weight, based on the total weight of the emulsion layer of thermographic silver. When present in an adjacent layer, the colorant will be present in the thermographic silver emulsion layer in an amount from 0 to 5.0% by weight and preferably from approximately 0 to 1.0% by weight based on the total weight of the layer of thermographic silver emulsion. In the adjacent layer containing colorant and binder, the colorant will be present in an amount from 1 to 25% by weight and preferably 5 to 20% by weight based on the total weight of the adjacent layer. Any suitable base or substrate material known to those skilled in the art can be used in the present invention. These materials can be opaque, translucent or transparent. The commonly used substrate or base material used in the thermographic technique includes but is not limited to paper; opaque or transparent polycarbonate and polyester films; and metal substrates reflecting light specularly, such as silver, gold and aluminum. As used herein, the phrase "metal substrates that reflect light specularly" refers to metal substrates that when struck with light, reflect light at a particular angle, as opposed to reflecting light through a range of angles. Optionally, a protective or anti-adherent layer, placed on the thermographic imaging element, can be used. Any conventional anti-stick material can be employed in the present invention. Examples of these anti-adhesion materials include but are not limited to waxes, silica particles, styrene-containing elastomeric block copolymers such as styrene-butadiene-styrene, styrene-isoprene-styrene, and mixtures thereof, with materials such as acetate of cellulose, cellulose acetate butyrate, cellulose acetate propylate and poly (vinyl butyral). Additional layers may be incorporated into the thermographic elements of the present invention, such as a primer layer or anti-static layer. In addition, an anti-static or anti-adhesion layer can optionally be applied to the back of the support. Materials for these purposes are well known to those skilled in the art. The thermographic image forming system, anti-adhesion layersInfrared or near infrared dye absorbent and anti-static employed in the present invention can be applied by any conventional method such as knife coating, roll coating, dip coating, curtain coating, hopper coating, etc .; If desired, two or more layers may be coated simultaneously by the procedures described in US Pat. No. 2,761,791 and British Patent No. 837,095. The thermographic image forming elements of the present invention are formed in an image by exposure to infrared or near infrared laser radiation, typically from an infrared or near infrared laser diode. As is well known in thermal imaging techniques, infrared or near infrared laser diodes can be advantageously arranged in a set to increase the speed of image formation. Lasers that can be used to provide near infrared or infrared radiation, include substantially any laser capable of generating light in the infrared or near infrared region of the electromagnetic spectrum of about 750 to 1100 nm, including dye lasers; solid-state laser diode lasers such as aluminum gallium arsenide diode lasers emitting in the region of 780 to 870 nm; and solid-state lasers pumped with diode such as Nd: YAG, Nd: YLF or Nd: glass. The following non-limiting examples further illustrate the present invention. EXAMPLES Materials used in the following examples are available from standard commercial sources such as Aldrich Chemical Co. (Milwaukee, Wl) unless otherwise specified. Silver behenate and silver laurate homogenates can be prepared as described in U.S. Pat. No. 4,210,717 (column 2, lines 55-57) or in U.S. Pat. No. 3,457,075 (column 4, lines 23-45 and column 6, lines 37-44). The following dyes were used in several examples that follow: Preparation of Dye 1: 5-Sulfamoll-2,3,3-trimethylindolenine is prepared according to the method described in US Pat. No. 4,062,782. A mixture of 37.0 g of 5-sulphamoyl-2,2,3-trimethylindolein, 16.7 ml of 2-chloroethanesulfonyl chloride and 200 ml of acetonitrile is refluxed for 6 hours. After the addition of 18.5 ml of water, the mixture is stirred overnight.

The separated solid is fixed, washed with acetonitrile and dried to give 11.0 g of a 1-sulfoalkylated quaternary salt intermediate. A mixture of 6.5 g of chlorocyclopenten dialdehyde, 26 g of the quaternary salt intermediate prepared above, 108 ml of anhydrous acetic acid, and 76 ml of acetic acid is stirred for 10 minutes at room temperature. After addition of 12.8 ml of diisopropylethylamine, the mixture is stirred overnight. The separated solid is filtered, washed with the solvent mixture and dried to give 20.0 g of dye 1.

Coloring 2 Preparation of Dye 2: In a 3 L capacity flask, 385 g of trimethylsulfonamido indolenine are added with 250 ml of burilonitrile. To this mixture is added without exotherm, 225 mL (364 g) of butylidene followed by 750 mL of additional butylnitrile. The mixture is heated to reflux with efficient top agitation for 22.5 hours. The heat is removed and the mixture is allowed to cool to about 40 ° C. The agitation is continued for one hour, after the addition of 1 L of ethylacetate. The solid is filtered, washed with methyl acetate and dried to give 595.6 g of N-butyl-2,3,3-dimethyl-5-sulfonamidoindoleninio iodide. To a solution of 370 mL of methylene chloride and 558 mL of dimethyl formamide cooled below 5 ° C, 227 mL of phosphorus oxychloride is added per hour for 1 hour at a rate such that the temperature does not exceed 5 ° C. After the addition is complete, the cooling is removed and the mixture is stirred for one hour. During a 30-minute period, 75mL of cyclopentanone is added in two portions. After the first addition, a slow increase in temperature and color is observed at about 35 ° C, at which time the second portion is added resulting in a large exotherm. After the exotherm ends, the mixture is heated before flow for four hours. The mixture is distilled under a slight vacuum after the addition of 1 L of ethyl acetate. Approximately 250 mL of liquid is collected to which 700 mL of ethyl acetate is added when a precipitate begins to form. The mixture is stirred overnight. The solid is filtered, washed with 1 L of ethylacetate, followed by heptane, and dried under vacuum at 35 ° C for four hours giving 115.8 g of crude chlorocyclopenten dialdehyde. The crude chlorocyclopenten dialdehyde is dissolved in 1250 mL of water. Crystals began to appear after about 1 hour. The mixture is left to rest during the weekend. The coffee solid is filtered, washed with water and dried under vacuum at 35 ° C for seven hours giving rise to 61.0 g of chlorocyclopenten dialdehyde. To a solution of 450 mL of acetic acid and 450 mL of acetic anhydride are added 278.7 g of N-butyl-2,3,3-dimethyl-5-sulfonamide indoleninium iodide and 47.6 g of cyclopentene dialdehyde. To the stirred mixture, 90 L of diethylamine are added per drop for 5 minutes at 60-65 ° C. No great exotherm is observed. The mixture is heated for an additional 30 minutes, after which the heat is removed and the reaction mixture is cooled to 15 ° C. The resulting golden-brown solid is filtered and washed with a 1: 1 mixture of acetic acid: acetic anhydride until the washings were greenish instead of purple. Acetic acid and residual acetic anhydride are removed by suspending the solid in one liter of ethyl acetate, followed by agitation for 90 minutes. The solid was filtered and washed with ethyl acetate. The filtrate had a pink hue. The solid is dried at 45 ° C and the mixture is emptied overnight giving 250.0 g of dye 2.

Coloring 3 Preparation of Dye 3: A mixture of O.l mole of dye 2 prepared above, 0.1 mole of sodium tetraphenyl borate, and 500 L of methanol, are refined with agitation for 10 minutes. The solid is filtered, washed with methanol, followed by water, and then dried to give 0.97 mol of dye 3.

Preparation of Dye 4: A stirred mixture of 26.05 g of 1,8-diaminonaphthalene, 32.66 g of 2-tridecanone, 55 mg of p-toluenesulfonic acid monohydrate, and 250 mL of toluene is heated under reflux under a nitrogen atmosphere using a trap Dean-Stark, to remove the water released from the reaction for 5 hours. The mixture is then washed with saturated sodium bicarbonate solution, dried over anhydrous potassium carbonate, filtered and the solvent removed under reduced pressure. The product is distilled to give 48.86 g of dihydroperimidinate intermediate; boiling point 192 to 213 ° C from 0.3 to 0.4 torr. A stirred mixture of 8.0 g of the intermediate dihydroperimine prepared above, 1.48 g of squaric acid, 64 mL of n-butanol and 64 L of toluene, is heated to reflux under a nitrogen atmosphere using a Dean-Stark trap, to remove the evolved water of the reaction for 3 hours. The mixture is filtered, poured into 600 L of petroleum ether (e.g. 35-60 ° C) and kept at 5 ° C for 18 hours. The product was separated by filtration, washed with petroleum ether and air dried to give 6.45 g of dye 4.

Coloring 5 Preparation of Dye 5: With agitation, 28 g of 2,3,3-trimethyl-5-methoxyindolenine are added to 80 mL of fuming sulfuric acid (10% of S03). The mixture is stirred overnight at room temperature and then poured onto 500 g of crushed ice. The aqueous solution is neutralized with a 30% sodium hydroxide solution and evaporated to dryness in vacuo. The residue is extracted with methanol and the solution is evaporated. The solid is collected in ethanol, filtered, washed with ethanol and dried under vacuum to give 20 g of an indolefin sulfate salt intermediate as yellowish prisms. A mixture of 20 g of intermediate indolenyl sulfate salt prepared above, 20 g of 2,4-butalsulfone, and 80 mL of benzonitrile, is refluxed with stirring for 5 hours. The solid formed was filtered, washed with ethyl acetate and dried in vacuo to give 25 g of an intermediate sulfonated quaternary salt as light brown prisms. A mixture of 14.2 g of the sulphonated quaternary salt intermediate prepared above, 7.5 g of N- (2-chloro-3- (dimethylamino) methylen) -1-cyclohexen-1-yl) -methylene) -N-ethylmetanaminium chloride (prepared as described in EPO Application No. 0288261), 5.4 mL of dicyclohexylethylamine and 75 mL of benzonitrile are stirred at room temperature overnight. The mixture is filtered and ethyl acetate is added to the filtrate. The solid is filtered and dried. The solid is dissolved in 50 mL of ethanol and 3 g of sodium iodide are added. The precipitate is filtered off, washed with acetonitrile and dried to give 3 g of dye 5, green prisms.

Coloring 6 Colorant 6 is commercially available from Eastman Kodak Co., Rochester, NY. Examples 1 to 3 The following coating solutions were used in the preparation of examples 1 to 3. Silver emulsion: silver behenate homogenate 160g (10% by weight in methyl ethyl ketone) Butvar ™ B76 poly (vinyl butyral), available from Monsanto Co. 20g Thermographic Coating Solutions: The thermographic coating solutions for Examples 1 to 3 were prepared by mixing the following ingredients with 20% by weight. g of the silver emulsion described above: Matter L Example 1 Example 2 Example 3 Methyl gallate 0. .6 g 0.6 g 0.6 g P Piirrooggaallooll 0. 0.22 gg 0.2 g 0.2 g Ftalazinone 0..2 g 0.2 g 0.2 g Succinimide 0, .1 g 0.1 g 0.1 g 2-imidazoli-dona 0, .1 g Ol g ol g Barbituric acid 0.05 g 0.05 benzotriazole 0.02 Each of the solutions was coated on a 0.08 mm polyester substrate (3 mils) ) at 0.1 (4 mils) wet thickness and dried in air at 60 ° C for three minutes.

A superior coating solution that absorbs infrared is prepared by mixing 0.08 g of Dye 1, 1.0 g of cellulose acetate resin CA 398-6 and 20.0 MEK. The topcoat solution is coated on the thermographic layer to a wet thickness of 0.05 mm (2 mils) and air dried for three minutes at 60"C. Examples: 4 to 6 The following coating solutions were employed in the preparation of Examples 1 to 3. Silver Emulsion: Complete soap homogenate of silver laurate 160g (10% by weight in methyl ethyl ketone) BX-1 poly (vinyl butyral), available from Sekisul Chemical Co. lOg Thermographic Coating Solutions: The thermographic coating solutions for Examples 4 to 6 were prepared by mixing the following ingredients with 20 g of the silver emulsion described above: Materi l Example 1 Example 3 Ejenplo 3 Methyl gallate 0.6 g 0. 6 g 0 6 g Pirogalol 0.2 g 0. 2 g 0. 2 g Phthalazinone 0.2 g 0. 2 g 0. 2 g Succinimide 0.1 g 0. 1 g 0. 1 g 2-imidazoli-dona Ol g Ol g Ol g Barbituric acid 0.05 g 0.05 benzotriazole 0.02 Each of the solutions was coated on a 0.08 mm (3 mils) polyester substrate at 0.1 (4 mils) wet thickness and air dried at 60 CU for three minutes. A superior coating solution that absorbs infrared, is prepared by mixing 0.08 g of Dye 1, 1.0 g of cellulose acetate resin CA 398-6 and 20.0 MEK. The top coating solution is coated on the thermographic layer to a wet thickness of 0.05 mm (2 mils) and air dried at 60 ° C for three minutes. Table 1 summarizes the results of exposing the materials of Examples 1 to 6 with an 810 nanometer laser diode (available from Spectra Diodo Labs of San Jose, CA) at 1.75 J / cm2 focused on the film plane a (one size) of 7 micron points). Visible optical densities were measured using a Perkin microdensitometer El er PD? 1010M and the UV optical densities were measured using a MacBeth TD523 densitometer equipped with a status ISA filter. The UV light stability is determined by allowing the sample to stand in a fluorescent light box (10,871,640 lux (1010 foot candles), 32.2 ° C (90 ° F)) for 24 hours.

Table 1 Eie plo 1 2 D ax Visible 3.06 3.23 3.25 Dmin Visible 0.05 0.05 0.05 Dmin UV 0.15 0.14 0.13 D in UV 0.55 0.61 0.23 stability 24 hours Table 1 cont. Example 5 6 Visible Dmax 3.87 3.84 3.83 Dmin Visible 0.07 0.07 0.07 Dmin UV 0.19 0.15 0.16 Dmin UV 0.53 0.59 0.25 24 hour stability Examples 3 and 6 clearly illustrate a significant improvement in light stability of Dmin UV when benzotriazole is added to the thermographic silver emulsion. Example 7 The following coating solutions were used in the preparation of Example 7. Silver Emulsion: Silver behenate homogenate 160g (10% by weight in methyl ethyl ketone) BX-1 poly (vinyl butyral), available from Sekisul Chemical Co lOg Thermographic Coating Solution: The thermographic coating solutions are prepared by adding 20 g of the silver emulsion to 0.6 g of methyl gallate, 0.1 g of suction, 0.1 g of phthalimide, 0.1 g of tetrachlorophthalic anhydride, 0.02 g of bentroziazol , 0.5 g of barbituric acid with 4 L of methanol. and 1 L of MEK. The solution is coated on a 0.08 mm (3 mils) polyester substrate at a wet thickness of 0.08 mm (3 mils) and air dried at 50 ° C for three minutes at 60 ° C. Infrared light is prepared by mixing 0.08 g of Dye 1, 0.5 g of Sekisul BX-1 poly (vinyl butyral), and 20.0 MEK. The topcoat solution is covered over the thermographic layer to a wet thickness of 0.08 mm (3 mils) and air dried for three minutes at 60 ° C. Example 7 is exposed with an 810 nanometer laser diode (available from Spectra Diode Labs of San José, CA) at 1.75 J / cm2 focused on the film plane a (a dot size of 7 microns). The film formed in the image resulted in Visible Dmax of 3.4, Visible Dmin of 0.08, Dmax UV of 3.6 and Dmin of UV of 0.17. Visible optical densities were measured using a Perkin Elder PDS 1010M microdensitometer. The UV optical densities were measured using a MacBeth model TD523 densitometer equipped with a status 18A filter. Example 8 The following coating solutions were used in the preparation of Example 8. Silver Emulsion: silver behenate homogenate 160g (10% by weight in methyl ethyl ketone) BX-1 poly (vinyl butyral), available from Sekisul Chemical Co. 15g Acryloid Acrylic Resin * "1 A-21 Rohm &Haas 6g Methyl ethyl ketone (MEK) 50g Thermoraphic Coating Solution: The thermographic coating solution is prepared by adding 15 g of the silver emulsion to 0.6 g of methyl gallate, 0.1 g of phtalizinone, 0.1 g of 2-imidazolidone, 0.1 g of tetrachlorophthalic anhydride, 0.5 g of barbituric acid with 4 mL of methanol, 1 mL of MEK and 1 mL of tetrahydrofuran. Prior to coating, 0.13 g of Dye 1 is added to the solution. The solution is coated on a 0.08 mm (3 mils) polyester substrate at a wet thickness of 0.08 mm (3 mils) and air dried at 50 ° C for three minutes. A top coating solution that contains 2.4 % by weight of Sekisul BX-1 poly (vinyl butyral) solution is overcoated on the thermographic layer to a thickness at a wet thickness of 0.08 mm (3 mils) and air-dried for three minutes at 60 ° C. Examples 9 The following coating solutions were used in the preparation of Examples 9-10: Silver Emulsion: silver behenate homogenate 160g (10% by weight of methyl ethyl ketone) BX-1 poly (vinyl butyral), available from Sekisul Chemical Co. 5g Thermographic Coating Solution: The thermographic coating solutions are prepared by adding 15 g of the silver emulsion to 0.6 g of methyl gallate, 0.1 g of succimide, 0.1 g of 2-imidazolidone, 0.1 g of tetrachlorophthalic anhydride, 0.05 g of acid barbiturate with 4 L of methanol. and 1 L of MEK. Prior to coating, 0.08 g of Dye 2 is added to the solution of Example 2, and 0.08 g of Dye 3 are added to the solution of Example 3. The solution is coated on a 0.08 mm (3 mils) polyester substrate at a thickness Wet of 0.08 mm (3 mils) and air dry at 50 ° C for three minutes. A topcoat solution containing 2.4% by weight of Sekisul BX-1 poly (vinyl butyral) solution is coated on the thermographic layer at a wet thickness of 0.08 mm (3 mils) and air-dried at 50 ° C for three minutes Examples 11 to 12 The following coating solutions were used in the preparation of Examples 11 to 12. Silver Emulsion: Silver behenate homogenate 160g (10% by weight of methyl ethyl ketone) ButvarMR B76 poly (vinyl butyral), available of Monsanto Co. 20g Thermographic Coating Solution: The thermographic coating solutions were prepared at 15 g of the silver emulsion to 0.8 g of methyl gallate, 0.2 g of succimide, 0.1 g of phthalazinone, 0.1 g of 2-imidazolidone in 4 mL of methanol and 1 mL of methyl ethyl ketone. Before coating 0.05 g of Dye 4 is added to the solution in Example 11, and 0.08 g of Dye 5 is added to the solution in Example 12. The solutions are coated on a 0.08 mm (3 mils) polyester substrate. to a wet thickness of 0.01 mm (4 mils) and dry in air at 21 ° C for ten minutes. A topcoat solution containing a 2.4 wt% solution of CA 398-6 cellulose acetate available from Eastman Kodak Co. is overcoated in the thermographic layer to a wet thickness of 0.05 mm (2 mils) and air dried at 21 ° C for twenty minutes. Table 2 summarizes the results of exposing the materials of Examples 8 to 12 with a laser diode of 810 nanometers (available from Spectra Diode Labs of San Jose, CA) at 1.75 J / cm2 focused on the film plane a (a 7 micdot size). The maximum optical densities (D "ax) and minimum (D ^ ,,) were measured using a MacBeth densitometer model TD523 equipped with a status 18A filter. Table 2 Example # 8 9 10 11 12 Exposure Time 72 45 45 45 7 2 (microseconds) D. 3.2 3.0 1.55 2.5 3.1 UV Dmln 0.19 0.16 0.13 0.18 0.1 8 Visible Dmln 0.07 0.7 0.7 0.07 0.1 3 Example 13 To show the effect of having halide ion present in the thermographic silver emulsion, 0.2 g of calcium bromide is added to the thermographic coating solution in example 9. The thermographic layer is turned completely black, when it air dried 21 ° C for 3 minutes. EXAMPLE 14 The following coating solutions were used in the preparation of Example 14: Silver Emulsion: Joints: Ter oarphic Coating: Thermographic coating solutions were prepared by adding 0.6 g of methyl gallate, 0.2 g of phthalazinone, 0.1 g of succinimide, 0.1 g of 2-imidazolidone and 0.2 g of pyrogallol to 20 g of the silver emulsion. The solution is coated on a 0.08 mm (3 mils) polyester substrate to a wet thickness of 0.01 mm (4 mils) and air dried at 21"C for ten minutes.A superior infrared absorbing solution is prepared by mixing 0.03 g of dye 6, 1.0 g of cellulose acetate resin CA 398-6 and 20.0 g of MEK The top coating solution is coated on the thermographic layer at a wet thickness of 0.05 mm (2 mils) and air dried by three minutes to 60"c. E 15 The following coating solutions were used in the preparation of Example 15. Silver Emulsion: Silver behenate homogenate 160g (10% by weight of methyl ethyl ketone) Butvar "* B76 poly (vinyl butyral), available from Monsanto Co. 20g Thermographic Coating Solutions: The thermographic coating solution was prepared by adding 0.6 g of methyl gallate, 0.2 g of imidazolidone, and 0.2 g of L-ascorbic acid palmitate to 20 g of the silver emulsion. The solution is coated with a polyester substrate .08 mm (mils) to 0.1 mm (4 mils) in wet thickness and air-dried at 60 ° C for three minutes. A superior infrared absorbing coating solution is prepared by mixing 0.08 g of Dye 6, 1.0 of cellulose acetate resin CA 398-6 and 21.0 g of MEK. The topcoat solution is coated on the thermographic layer to a wet thickness of 0.05 mm (2 mils) and air dried for three minutes at 60 ° C. Table 2 summarizes the laser exposure results for each example. Maximum and minimum optical densities were measured using a MacBeth densitometer model TD-523 equipped with a filter and status 18A. Table 3 Example 14 15 Dmax 3.73 2.73 Dmln 0.09 0.10 The radiation-absorbing dye is incorporated primarily into the thermographic silver emulsion layer. The thermographic silver emulsion layer is considered to be heated above its vitreous transition temperature, thereby allowing the silver ion reducing agent to migrate to the light-insensitive organic silver salt (e.g., silver behenate) within the layer. The silver behenate is reduced by the reducing agent to elemental silver, forming a brown / black color image. Organic pigments are incorporated into the formulation to obtain a more neutral black color. The formation of the elemental silver in the image forming area 5 not only provides UV opacity of the final element image but also an infrared absorber that accelerates the image forming process. The intensity of the infrared laser beam decreases exponentially as it penetrates the thermographic silver emulsion layer. The thickness of the layer , 0 thermographic silver emulsion and the concentration of the infrared dye will affect the sharpness of the image due to the decreased intensity of the laser beam, as a function of the distance through the layer. The thickness of the thermographic silver emulsion layer is preferably between approximately ] 1 and 10 microns and more preferably between about 2 and 6 microns. The concentration of the infrared dye and the thickness of the layer is adjusted such that the IR absorption of the layer is generally between 20 to 99%; preferably 50 and 90% and more preferably 60 to 85%. In conditions of high resolution image formation, where the pixel residence time is short and the laser peak intensity is high, ablation may occur if the infrared dye is incorporated only in the thermographic emulsion layer of the construction. The speed of The heating is higher at the surface where the laser beam enters the thermographic silver emulsion layer. As the elemental silver is formed, the absorption of the laser beam increases. This can cause the thermographic silver emulsion layer to overheat, thereby causing smoke, damage or ablation. By eliminating or decreasing the concentration of infrared dye in the thermographic silver emulsion layer and adding infrared dye in a layer adjacent to the thermographic silver emulsion layer, the penetration of the laser beam into the thermographic silver emulsion layer can be increased . The thermographic imaging element is exposed by directing the laser beam through the thermographic silver emulsion layer before striking the adjacent layer containing the infrared dye. The infrared absorbent layer can be placed either above or below the thermographic silver emulsion layer with respect to the substrate on which the adjacent layers are deposited. The concentration of the infrared dye in the infrared absorbent layer is chosen such that the highest heating rate occurs at the interface between the infrared absorbent layer and the thermographic silver emulsion layer. The concentration of infrared dye will depend on the thickness of the thermographic layer and the physical properties of the dye. For example, the concentration of the infrared dye in a thermographic layer with a thickness of one miera, is adjusted to achieve an absorption of preferably of approximately 90% or more. During the course of the image-forming laser pulse, elemental silver forms at this interface. The elemental silver formed increases the infrared absorption in this region of the thermographic silver emulsion layer and acts as a heat source for the image area within the thermographic silver emulsion layer. As the elemental silver density adjacent to the infrared absorbent layer accumulates, the intensity near the opposite surface of the thermographic silver emulsion layer is attenuated, thereby reducing its reheat in this region. The profile of the pixel image will resemble an hourglass shape, thus resulting in a sharper image. EXAMPLE 16 This example demonstrates the effect of the thickness of the thermographic silver emulsion layer, the resin / silver ratio, the concentration of the infrared dye and the type of top coat on the imaging characteristics of the thermographic imaging element of the invention. The following coating solutions are used in the preparation of samples A-P. X are variables specified in Table 4. Silver Em lsion; Silver behenate homogenate 160g (10% by weight in methyl ethyl ketone) Butvar ™ B76 poly (vinyl butyral), available from Monsanto Co. Xg Thermographic Coating Solution: The thermographic coating solution is prepared by adding 15 g of the silver emulsion to 0.08 g of methyl gallate, 0.2 g of succinimide, 0.1 g of phthalazinone, 0.1 g of 2-imidalozidinone in 4 mL of methanol and 1 mL of methyl ethyl ketone. Before coating Xg of Dye 2 are added to the solution. The solutions were coated on a 0.08mm (3 mil) polyester substrate at a wet thickness X and air dried at 70 ° C for three minutes. A topcoat solution comprising a solution of 2.4% by weight of cellulose acetate CA 398-6; Scriptset ™ 540 aleonic-styrene anhydride copolymer available from Monsanto Company; styrene-acrylonitrile resin Tyril "18 880B available from Dow Chemical Company, or poly (vinyl alcohol) (PVA) AirvolMR 523 available from Air Products and Chemicals, Inc, Allentown, PA, and X% dye 2, are overcoated on the Thermographic layer at 3X humid thickness and air-drying at 50 ° for three minutes AP samples were scanned with a laser sensitometer at several different scanning speeds in the range of 20 or 30 cm / sec. 415 nanometers were measured using a Perkin-Elmer PDSM m-densitometer, optical density measurements were taken at 826 nanometers (laser diode wavelength) and at 415 nanometers for the non-image elements using a Shi adzu MPC-3100 spectrophotometer. / UV3101PC Table 4 Sample # ABCD Layer Thickness 0.10 0.05 0.10 0.05 Thermographic (Moist, mm) Layer Thickness 0 0 0 0 Superior Coating (Wet, mm) Resin Type no no no no Supe Coating rior Content of 20g 20g lOg lOg Butvar in silver layer Dye 0.05g 0.05g Q.Q5g 0.05g infrared in thermographic layer Table 4 Sample # A B C D Coloring 0 0 0 0 infrared in top coating Dmin (415 nm) 0.95 0.14 1.1 0.3 Optical Density @ 825 nm Table 4 cont. Sample # E F G H Thickness of Layer 0.10 0.05 0.10 0.10 Thermographic (Wet, mm) Layer Thickness 0 0 0.05 0.05 Superior Coating (Wet, mm) Resin Type of no PVA PVA Top Coating Content of 5g 5g 0 0 Butvar in Silver layer Dye 0.05g 0.05g 0 0.01 infrared Table 4 cont. Sample i.fiJL in thermographic layer Coloring 0 0.10g 0.15g infrared in top coating Dmin (415 nm) 1.24 0.75 0.34 0.53 Optical Density 0.79 0.27 1.80 3.20 @ 825 nm Sample # I J K L Thickness of Layer 0.10 0.05 0.10 0.05 Thermographic (Moist, mm) Layer Thickness 0.05 0.5 0.05 0.05 Superior Coating (Humid, mm) Resin Type acetate acetate acetate Coating of de of Superior cellulose cellulose cellulose cellulose Content of lOg lOg lOg lOg Butvar in Silver layer Dye 0.07g 0.07g 0.10g 0.10 Table 4 cont. Sample # I J K L infrared in Thermographic layer Dye 0 0 0 0 infrared in top coating Dmin (415 nm) 0.23 0.07 0.42 0.12 Optical Density 0.75 0.30 1.40 0.84 @ 825 nm Table 4 cont. Sample # M N 0 P Layer Thickness 0.10 0.10 0.10 0.10 Thermographic (Wet, mm) Layer Thickness 0.05 0.05 0.05 0.05 Superior Coating (Wet, mm) Resin Type of TirilME ScripsetMR Scripset ^ Scripset " Top Coating Content of 0 0 0 0 Butvar in Table 4 cont. Sample I M N O Silver layer Coloring 0 O.Olg O.Olg infrared in thermogáfica layer Coloring 0 0.10g 0.15g 0.10g infrared in top coating Dmin (415 nm) 0.55 0.35 0.29 0.42 Optical Density 0.76 0.84 1.45 1.11 < _ 825 nm A laser sensor (1), illustrated in Figure 1, was used to evaluate the thermographic imaging elements in example 16. A beam of 700 milliwatts (2) emitted from a fiber coupled laser diode 2361 -P2 (3) (available from Spectrum Diode Labs) was focused on a rotating drum (4). The core diameter of the fiber (5) with 100 micrometers and the wavelength from a Laser (3) was 826 nanometers. The energy in the rotary drum (4) was 210 milliwatts, and the point shape was a flat top cone with a point size of 45 micras total width at the maximum medium (FWHM). The profile of cone with flat tip is characterized by r0 / the radius of the peak intensity of the cone and r_, the outer radius of the cone where the intensity is almost zero. A profiler with scanning slot beam is used to measure the intensity profile of the laser point. Since the profiler integrates the intensity in the direction perpendicular to the groove movement, the current point profile is inferred from the profiler data. Figure 2 shows a comparison of data of the profiler (6) and the calculated profile data (7) that are expected for a flat cone cone intensity profile with r0 equal to 10 micrometers and rx equal to 36 micrometers. The curve is calculated by integrating the cone intensity profile with flat top model in one direction and readjusting in scale. As the intensity profile is scanned through the film, points placed under the dotted profile will receive a finite exposure energy. This exposure energy depends on the location of the point with respect to the scanned point as well as the scanning speed of points. Figure 3a shows the total incident exposure energy plotted against the distance through the beam in the transverse direction / scan. The curve is calculated for the fiber-coupled sensitometer model beam shape, considering a scanning speed of 40 centimeters / second. In Figure 3b, a microdensitometer profile of a line formed in image with the energy profile illustrated in Figure 3a, on the thermographic element is illustrated. (Example 16, sample N not illustrated). The density data are collected using a narrowband filter at 415 nanometers. The density edges in Figure 3b exhibit gradients that are larger than those of the incident exposure profile illustrated in Figure 3a, indicating that the thermographic element (Example 16, Sample N not shown) has a high contrast. The contrast of the thermographic element can be examined more quantitatively using a D-logE curve. A D-logE curve is a trace of the film density formed in image, against the logarithm of the incident exposure energy. The theoretical form for this curve is given by D = ylog (EEp / Eo); where y is equal to the slope of the D-logE curve, E is equal to the incident exposure energy, Er is equal to the effective energy background or fog, Eo is equal to the minimum energy required to start the development of the image, and D is equal to the optical density of the element when exposed to the exposure energy E. Using the data illustrated in Figure 3, a D-logE curve is calculated and plotted in Figure 4. From the curve model described by the optical density equation, the range or contrast of the element corresponds to the slope of the D-logE curve. The gamma value for the D-logE curve in Figure 4 is 34. For a relative comparison, a typical fast-access wet-processed silver halide film has a range of about 10. The superior contrast is an advantage for applications in graphic arts, since high-contrast half-tone points are desired for consistent tone curve control and also for new stochastic classification processes. Similar advantages are used in photo-tool applications for printed circuit boards. The D-logE curve in Figure 4 shows that the density development starts at approximately 0.9 J / cm and that the density saturation at maximum density (DHax) occurs at 1.2 J / cm2. It will be understood that the optimum image forming speed and explorer exposure conditions will be unique to the particular explorer employed to image the thermographic element. Each of the samples described in Table 4 were scanned with the laser sensitometer of Figure 1 at various different speeds in the range of 20 to 60 centimeters / second. D-logE curves were calculated with a Perkin-Elmer microdensitometer using the data of the density profiles of these lines at 415 nanometers. The novel parameters in the density equation described above were determined from the D-logE curves and are summarized below in Table 5. Table 5 Sample i A B C D Dmax 4.5 (415 nm) mD Eo, 50 0.77 0.85 0.74 0.93 0.93 0.90 mD Esat, 50 1.30 1.40 1.40 1.80 D Dmin, 50 3.50 3.50 3.65 1.50 3.60 Table 5 Sample # ABCDE range, 50 0.85 0.40 0.55 0.65 0.80 mD Eo, LOO 11.65 14.30 11.19 9.93 8.98 D Dsat, 100 0.966 0.94 0.96 1.00 1.03 mD Dmax, 100 1.27 1.30 1.26 10.00 1.32 D Dmin, 100 3.5 3.0 3.4 0.0 3.6 range, 100 0.80 0.35 0.80 0.00 0.80 Range 100 22.72 18.82 22.02 0.00 25.99 / Range 50 1.95 1.32 1.97 0.00 2.89 Sample # F I J K L Dmax (415 n) mD Eo, 50 0.65 0.80 1.13 0.56 0.35 D East, 50 1.60 1.26 2.00 11.30 1.00 mD Dmax, 50 3.70 3.60 3.50 3.70 3.60 D Dmin, 50 0.70 0.40 0.30 0.60 0.35 range, 50 7.80 16.22 12.90 8.47 7.12 mD Eo, 50 1.00 0.90 1.00 0.66 0.661 mD Dsat, 100 10.00 1.16 10.00 1.00 1. .042 D Dmax, 100 0.0 3.5 0.0 3.6 3.5 mD Dmin, 100 0.00 0.30 0.00 0.70 0.40 range, 100 0.00 29.03 0.00 16.07 15.88 Range 100 0.00 1.79 0.00 1.90 2.20 / Range 50 Sample # N 0 Dmax (4L5 nm) 5.00 4.4 D Eo, 50 0.95 0.88 mD Esat, 50 1.65 1.26 D Dmax, 100 3.70 3.80 mD Dmin, 50 0.70 0.50 range, 50 12.51 21.16 mD Eo, 100 0.96 0.97 mD Dsat, 100 1.20 1.26 mD Dmax, 100 3.7 3.8 mD Dmin, 100 0.40 0.50 range, 100 34.05 29.05 Range 100 2.72 1.37 / crama 50 D Eo, 50 = Eo value of the D-logE curve, scanning speed at 20 centimeters / second (cm / s) mD Esat, 50 = Value Esat of the curve D-logE scanning speed at 20 cm / s mD Dmax, 50 = Maximum density at 20 cm / s mD Dmin, 50 = minimum density at 20 cm / s range, 50 = range value when scanned at 20 cm / s mD Eo, 100 = Eo value of the DlogE curve, scanning speed at 40 cm / s mD Esat, 100 = Value Esat of the D-loge curve scan at 40 cm / s mD Dmax, 100 = Maximum density at 40 cm / s mD Dmin, 100 = Minimum density at 40 cm / s range, 100 = range value when scanned at 40 cm / s range 100 / range 50 = (range at 40 cm / s) divided by (range at 20 cm / s) The average value Eo for the stras A to L is 0.8 ± 0. 2 Joules / cm2 at a scanning speed of 20 cm / s and 0.9 ± 0.2 joules / cm2 at a scanning speed of 40 cm / s. The minimum exposure energy required to begin the development of density development is relatively independent of the scanning speed. Esat values are independent of speed equally. The average value for Esat is 1.3 ± 0.2 Joules / cm2 at a scanning speed of 20 cm / s and 1.2 ± 0.1 Joules / cma at a scanning speed of 40 cm / s. Gamma values show evidence of image information performance differences at the two speeds. The average range value for samples A to L, at a scanning speed of 20 cm / s is 12 ± 4, while the average range value at 40 cm / s is 24 ± 6. In this way, gamma values appear increase significantly, as the scanning speed increases. It is possible that at lower scanning speeds, the thermal diffusion is more significant, resulting in loss of sharpness of the edges and thus reducing the range of the image. Unlike photothermographic silver media, thermographic silver elements show a more pronounced effect of exposure conditions. Samples C, I, and K were coated with different concentrations of infrared dye. Samples C and I have an absorption of 80% at the laser wavelength of 826 nanometers. Sample K is coated to the same thickness, but is loaded with more infrared dye in a way that absorbs 96% at 826 nanometers. The average of Eo and Esat for the average values C and I are 0.93 joules / cm2 and 1.21 Joul.es/cm2, respectively at an exploration speed of 40 cm / s. The values Eo and Esat for the sample k are 0.66 Joules / cm2 and 1.0 Joule / cm2 respectively. The sensitivity of the film seems to be slightly improved by the 16% increase in layer absorption. The effect is more pronounced for thinner coatings. Samples D, J and L were coated at half the thickness of C, I and K. Samples D and J only absorb approximately 50% of the incident laser radiation and do not form an image at the scanning speed of 40 cm / s. The L sample absorbs 85% of the incident laser radiation. The average values Eo and Esat for D and J are 1.0 Joules / cm2 and 1.9 Joules / cm2, respectively, 20 cm / s, while the values Eo and Esat for sample L are 0.35 Joules / cm2 and 1.0 Joules / cm2, respectively. The exposure energy values for copying are lower than for D and J. The sensitivity is improved by increasing the laser absorption and in the thermographic silver emission layer, or with an increased concentration of infrared dye. The edges of the image-formed lines scanned at 40 cm / s in samples K and L were smoother than the other single-infrared layer samples. Line border sharpness can be improved by increasing the concentration of an infrared dye in the layer. A comparison of the samples with different thicknesses, but similar percentages of absorption, indicate that the thinnest coating with a higher concentration of the infrared dye is more sensitive than a thicker coating. The Eo and Esat values for K are 0.56 and 1.3 joules / cm2, respectively, at 20 cm / s, while the Eo and Esat values for L are 0.35 and 1.0 Joules / cm2, respectively. The thickness of the sample of L is half of K but it absorbs 85% of the laser radiation, which is approximately comparable with that of K. Increasing the concentration of infrared dye may cause ablation, due to increasing at peak temperatures in the layer ter ogáfica. The sensitivity of a single layer of thermographic silver emulsion containing the infrared dye can be maximized to reverse the thermographic silver emulsion layer as thinly as possible with the highest achievable infrared dye concentration, while maintaining the density maximum of 0.

The quality of the line formed in the image is affected by the ratio of resin to silver. Exposure energy values and gamma values are not significantly affected by changes in the ratio of resin to silver, as shown in Table 5 for samples A, C and E. However, microphotographs of these samples indicate that the proportion from resin to silver affects the image quality of the lines. As the ratio of resin to silver decreases, the edges of the lines become coarse and serrated and the uniformity of density across and along the line formed in the image is diminished. Decreasing resin concentration should improve the sensitivity of the material, due to less heat bulk material. However, jagged edges seem to have displaced this advantage. The ratio of resin to silver is preferably between about 25 to 50% by weight. Another embodiment of the present invention comprises the addition of infrared dye in a layer adjacent to the thermographic silver emulsion layer. The samples N, O, G, H and P in Example 16 in valued from the addition of an infrared dye in the top coat have thermographic elements. For some unknown reason, samples M, G and H were poorly imaged and therefore are not included in Table 4. Samples N. O and P exhibit improved line quality compared to samples containing infrared dye in the thermographic layer only. The layers of thermographatric plates samples N, O and P were overcoated with a coating of 0.5 mm of Scripset resins containing a high concentration of infrared dye. A piece of adhesive tape over pressure to separate the upper coating of the thermographic silver emulsion layer, to verify that the two layers did not get mixed. Samples N and 0 have gamma values greater than 34 and 30, respectively, at a scanning speed of 40 cm / s. These gamma values are comparable to a conventional silver halide duplication film. For comparison, a typical fast-access silver halide film has a range of about 10. The sample quality P is similar to N and O, although a D-logE curve is not calculated for these samples. Both N and 0 exhibit smooth line edges with roughly one edge roughness. The samples containing infrared dye in the thermographic silver layer only had coarser edges than the N and O samples. The density uniformity of the N, O and P samples was within ± 5%. The sensitivity of the N and O samples is comparable to the samples that do not have an upper coating containing infrared dye. No ablation of N, O and P samples is observed. Improved edge contrast, edge sharpness and density uniformity can be achieved by the addition of infrared dye in a layer adjacent to the thermographic silver layer. In addition, the susceptibility to ablation is also reduced in this construction. The concentration of the infrared dye in the thermographic silver layer is in an amount that the absorption of the laser radiation in the thermographic layer is preferably less than or equal to 40% and more preferably less than or equal to 35%. Figure 5 shows the transmission spectra formed in image (8) and not formed in image (background) (9) for Example 16, sample N. The absorption peak of improved infrared dye at 820 nanometers is clearly evident. The density of the laser diode wavelength of 826 manometers is increased from 0.84 (14.5% transmission) to 1.26 (5.5% transmission), while the density at 415 nanometers increases from 0.355 (44.2% transmission) to 5.0 (about 0% transmission). The elemental silver formed in the thermographic layer during exposure, provides an improved absorption difference in the ultraviolet (UV) which is an advantage in UV mask applications. In Table 5, the Dnax measured by the microdensitometer was 3.7, which is lower than the value obtained by the spectrophotometer. Apparently, the maximum optical density that can be measured by the densitometer is limited to approximately 3.7. This implies that many of the gamma values calculated in Table 5 are smaller than the values and therefore should be treated as conservative estimates. In order to incorporate the imaging characteristics of the thermographic elements with effects due to heat dissipation, in Examples 1, 2, 3, 4, 5, 6 and 16 (sample N) images are formed using 150 milliwatts of (SDL-5422, available from Spectra Diode Labs) 150 milliwatt (110 milliwatts in the image plane) emitting at 811 nanometers. The beam was focused at a size of 8 micrometers (full width at level 1 / e2) and scanned at 213 centimeters / second, with a tansversal scan line spacing of 4.5 micrometers. Table 6 summarizes the result of the evaluation. TABLE 6 Example Dmax, Dmin Dmax Dmax 365 nm 365 nm Dmin, Dmin 365 nm 1 2.17 0.31 1.85 2.48 2 2.58 0.39 2.19 2.94 3 1.78 0.39 1.39 1.85 4 3.05 0.63 2.42 3.13 5 4.50 0.57 3.93 5.00 6 4.04 0.90 3.14 5.00 16, 4.40 0.47 3.92 5.00 Sample N TABLE 6 Cont. Example Dmin, D ax - 415 nm Dmin, 415 nm 1 0.25 2.23 TABLE 6 Cont. Example Dmin, Dmax- 415 nm Dmin, 415 nm 0.29 2.65 3 0.29 1.56 4 0.57 2.56 5 0.42 4.58 6 0.59 4.01 16 0.53 4.46 Sample N The data shows that the higher contrast films (Dmax-Dmin) are achieved when the silver opening is used in conjunction with barbituric acid in the emulsion layer of thermographic silver (Examples 5 and 6) or a higher concentration of methyl gallate is used in the silver behenate formulation (Example 16, sample N). In order to improve the work-up UV contrast applications, the preferred contrast is greater than about 2.50. The data also show that the addition of benzontriazole inhibits the speed of the film; however, the decrease in speed is minimized when silver laurate is used for silver soap. Even though a visible decrease in velocity can be observed, stability will improve light, as illustrated in Table 1 provides an advantage to include benzotrlasol in the thermographic silver emulsion. Reasonable variations and modifications of the foregoing description are possible, without departing from the spirit and scope of the present as defined in the claims.

Claims

CLAIMS 1.- Thermohic image forming element, comprising a substrate having at least one surface, a thermohic imaging system, comprising at least one layer consisting of an organic silver salt insensitive to light; reducing agent for silver ion; binder, light stabilizer; organic pigment; and a dye that absorbs radiation in the wavelength range of 750 to 1100 n, wherein at least one layer comprises the organic silver salt insensitive to light, forms an image density greater than about 1.0, when exposed to 0.10 - 2.0 Joules / cm2 of radiation in 0.20 to 200 microseconds. 2. The element according to claim 1, wherein the image density is greater than about
2.00 and comprises metallic silver.
3. The element according to claim 1, wherein the image density is greater than about 2.50 and comprises metallic silver.
4. The element according to claim 1, wherein the density of image formation is greater than about 2.75 and comprises metallic silver.
5. The element according to claim 1, wherein the dye absorbs radiation in the wavelength range from about 750 to 900 nm.
6. - The element according to claim 1, wherein the thermohic image forming system further comprises a development accelerator.
7. The element according to claim 1, wherein the organic silver salt insensitive to light is a silver salt of a carboxylic acid containing 10 to 30 carbon atoms.
8. The element according to claim 7, wherein the silver salt is silver behenate or silver laurate.
9. The element according to claim 6, wherein the development accelerator is a selection of the group consisting of: (i) a 3-indazolinone compound: wherein: R is selected from the group consisting of hydrogen, an alkyl group of 1 to 4 carbon atoms; halogen; -COOH; and RxCOOH, wherein R1 is an alkyl group of 1 to 4 carbon atoms; and (ii) a urea compound of the formula: II R-NH-C-NH-R3 wherein R2 and R3 each independently represent hydrogen; an alkyl or cycloalkyl group with 1 to 10 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 6 ring atoms.
10. The element of conformity with the claim 9, wherein R represents hydrogen; R2 and R3 each independently represents an alkyl or cycloalkyl group with 1 to 5 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 5 ring atoms.
11.- The element of conformity with the claim 1, wherein the organic pigment is at least one selected from the group consisting of phthalazinone, phthalazine, barbituric acid, succinimide and phthalamide.
12.- Thermohic imaging element comprising a substrate is coated with a thermohic imaging system, the thermohic imaging system comprises at least two adjacent layers, one of the adjacent layers comprises salt of organic silver insensitive to light; reducing agent for silver ion; organic pigment; binder, light stabilizer; and optionally a dye that absorbs radiation having a wavelength in the range of about 750 to 1100 nm; and the other adjacent layer consists essentially of binder and dye that absorbs radiation in the wavelength range of about 750 to 1100 nm, wherein the layer comprising the organic silver salt insensitive to light forms a higher image density that approximately 1.0, when exposed to 0.10 - 2.0 Joules / cm2 of radiation in 0.20 to 200 icro-seconds.
13. The element according to claim 12, wherein the organic silver salt insensitive to light is a silver salt of a carboxylic acid containing 10-30 carbon atoms.
14. The element according to claim 12, wherein the silver salt of a carboxylic acid is silver behenate or silver laurate.
15. The element according to claim 12, wherein the thermographic image forming system further comprises a development accelerator.
16. The element according to claim 15, wherein the development accelerator is selected from the group consisting of: (i) a 3-indazolindole compound: wherein: R is selected from the group consisting of hydrogen; an alkyl group of 1 to 4 carbon atoms; halogen; -COOH; and R1COOH, wherein Ra is an alkyl group of 1 to 4 carbon atoms; and (ii) a urea compound of the formula: R2-NH-C-NH-R3 wherein R2 and R3, each independently represents hydrogen; an alkyl or cycloalkyl group with 1 to 10 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 6 ring atoms.
17.- The element of conformity with the claim 16, wherein R represents hydrogen; R2 and R3 each independently represents an alkyl or cycloalkyl group with 1 to 5 carbon atoms; or phenyl; or R2 and R 'together form a heterocyclic group containing up to 5 ring atoms.
18. The element according to claim 12, wherein the dye absorbs radiation having a wavelength in the range of about 750 to 900 nm.
19. The element according to claim 12, wherein the image density is greater than about 2.00 and comprises metallic silver.
20. The element according to claim 12, wherein the image density is greater than about 2.50 and comprises metallic silver.
21. The element according to claim 12, wherein the image density is greater than about 2.75 and comprises metallic silver.
22. - The element according to claim 12, wherein the organic pigment is at least one selected from the group consisting of phthalazinone, phthalazine, barbituric acid, succinimide and phthalimide.
23. A method for forming an image, comprising the step of exposing a thermographic image forming element, comprising a substrate coated with a thermographic imaging system, the thermographic image forming system comprising at least one layer comprising salt of organic silver insensitive to light; reducing agent for silver ion; binder, light stabilizer; a dye that absorbs radiation having a wavelength in the range of 750 to 1100 nm; organic pigment; light stabilizer and binder, to radiation having a wavelength in the range of about 750 to 1100 nm, wherein the layer comprising at least the organic silver salt insensitive to light forms an image density greater than about 1.0 when exposed to 0.10 - 2.0 Joules / cm2 of radiation in 0.20 to 200 microseconds.
24. The process according to claim 23, wherein the organic silver salt insensitive to light is a silver salt of a carboxylic acid containing 10-30 carbon atoms.
25. The process according to claim 24, wherein the silver salt of a carboxylic acid is silver behenate or silver laurate.
26. The method according to claim 23, wherein the thermographic image forming system further comprises a development accelerator.
27. The method according to claim 26, wherein the development accelerator is selected from the group consisting of: (i) a 3-indazolindole compound: wherein: R is selected from the group consisting of hydrogen, an alkyl group of 1 to 4 carbon atoms; halogen; -COOH; and R 1 COOH, wherein R 1 is an alkyl group of 1 to 4 carbon atoms; and (ii) a urea compound of the formula: 0 || R2-NH-C-NH-R3 wherein R2 and R3 each independently represent hydrogen; an alkyl or cycloalkyl group with 1 to 10 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 6 ring atoms.
28. - The process according to claim 27, wherein R represents hydrogen; R2 and R3 each independently represents an alkyl or cycloalkyl group with 1 to 5 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 5 ring atoms.
29. The procedure according to claim 23, wherein the dye absorbs radiation having a wavelength in the range of about 750 to 900 nm.
30. The method according to claim 23, wherein the image density is greater than about 2.00 and comprises metallic silver.
31. The method according to claim 23, wherein the image density is greater than about 2.50 and comprises metallic silver.
32. The method according to claim 23, wherein the image density is greater than about 2.75 and comprises metallic silver.
33. The method according to claim 23, wherein the organic pigment is at least one selected from the group consisting of phthalazinone, phthalazine, barbituric acid, succinimide, and phthalimide.
34.- A method for forming an image, comprising the step of exposing a thermographic image forming element, comprising a substrate coated with a thermographic image forming system, the thermographic image forming system comprising at least two adjacent layers, one of the adjacent layers comprises organic silver salt insensitive to light; reducing agent for silver ion; organice-binder pigment; light stabilizer; and optionally a dye that absorbs radiation having a wavelength in the range of about 750 to 1100 nm; and the other adjacent layer consists essentially of binder and the dye absorbing radiation in wavelength range of about 750 to 1100 nm, to radiation having a range of wavelengths of about 750 to 1100 nm, which is directed to the element thermographic image former through the layer comprising the organic silver salt insensitive to light, before the adjacent layer consisting essentially of binder and the dye absorbing radiation impinges, such that the cap comprising the salt of Organic silver insensitive to light forms an image density greater than about 1.0, when exposed to 0.10 - 2.0 Joules / cm2 of radiation in 0.20 to 200 microseconds.
35. The process according to claim 34, wherein the light-insensitive organic silver salt is a silver salt of a carboxylic acid containing 10-30 carbon atoms.
36. The process according to claim 34, wherein the silver salt of a carboxylic acid is silver behenate or silver laurate.
37.- The method according to claim 34, wherein the thermographic image forming system further comprises a development accelerator.
38.- The method according to claim 37, wherein the development accelerator is selected from the group consisting of: (i) a 3-indazolinone compound: wherein: R is selected from the group consisting of hydrogen; an alkyl group of 1 to 4 carbon atoms; halogen; -COOH; and R 1 COOH wherein R 1 is an alkyl group of 1 to 4 carbon atoms; and (ii) a urea compound of the formula: 0 || R2-NH-C-NH-R3 wherein R2 and R3 each independently represent hydrogen; an alkyl or cycloalkyl group with 1 to 10 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 6 ring atoms.
39. - The process according to claim 38, wherein R represents hydrogen; R2 and R3 each independently represents an alkyl or cycloalkyl group with 1 to 5 carbon atoms; or phenyl; or R2 and R3 together form a heterocyclic group containing up to 5 ring atoms.
40.- The method according to claim 34, wherein the dye absorbs radiation having a wavelength in the range from about 750 to 900 nm.
41.- The method according to claim 34, wherein the image density is greater than about 2.00 and comprises metallic silver.
42.- The method according to claim 34, wherein the image density is greater than about 2.50 and comprises metallic silver.
43.- The method according to claim 34, wherein the image density is greater than about 2.75.
44. The method according to claim 34, wherein the organic pigment is at least a selection of the group consisting of phthalazinone, phthalazine, barbituric acid, succinimide, and phthalimide.
45. The method according to claim 34, wherein the dye that absorbs radiation having a wavelength in the range of about 750 to 900 nm, is present in both adjacent layers.