EP0741320A1 - Photothermographic Photosensitive Recording Material with Hugh Gradient - Google Patents

Abstract

Photothermographic material has a base with binder layer(s) contg. light-sensitive Ag halide and a light-insensitive Ag salt of an organic acid. This layer also contains or is in reactive contact with a layer contg. a reducing agent and opt. a toner. At least one of these layers contains a hydrazinoethene deriv. of formula R1R3C=CH-NH-NH-R2 (I) to increase the gradation, where R1 is -CN or R4-CO-; R2 is H or an at most 12C alkyl or (alk)aryl; R3 is CN or an up to 12C alkyl, aryl, acyl or alkoxycarbonyl; and R4 is NH2 or a 1-6C alkyl, alkoxy or alkylamino.

Description

The invention relates to a light-sensitive material for high-contrast black-and-white images, in which the exposed image can be developed by a heat treatment.

Materials of this type are also known under the names "photothermographic recording materials" or "dry silver materials" for short and are described, for example, in Research Disclosures No. 170 029 (June 1978) and 299 063 (March 1989).

The photosensitive coating of "System B" of the former publication contains photosensitive silver halide and an imaging redox mixture in a binder. The redox mixture consists of a metal salt of an organic compound as an oxidizing agent and an organic reducing or developing agent. The metal salt is usually a light-insensitive silver salt.

The formation of the image in these dry silver materials is based on the fact that the latent image formed in the silver halide during exposure catalyzes the reaction of the insensitive silver salt with the reducing agent during the heat treatment.

The research disclosures mentioned also provide a compilation of numerous processes and substances that are used to improve certain properties of the dry silver materials in order to make them useful for practical use.

A constant problem with dry silver materials is the generally moderate optical maximum density and the resulting flat gradation. Often strong from neutral black deviating picture tone makes this disadvantage appear even more serious when observed or measured with white light. Attempts are therefore being made to increase the amount of silver developed by means of development accelerators and to darken the color tone of the image by means of toner and thus to achieve higher density and gradation. Such toners are mentioned in Research Disclosure 170029, Chapter V, and 299063, Chapter XXII. Examples of useful toners are phthalazinone and its derivatives, for example 2-acetylphthalazinone, phthalimide and derivatives such as N-hydroxyphthalimide, succinimide, N-hydroxy-1,8-naphthalimide. Thus, maximum densities of about 2.5 and gradations (gamma values) of about 3 can be achieved (David A. Morgan, New Capabilities with Dry Silver Recording Materials, Journal of Imaging Technology, Volume 13, page 4 ff. (1987)).

Research Disclosure 177011 (Volume 177, January 1979) discloses photothermographic materials with a hydrophilic binder (type "System A" of the above-mentioned Research Disclosure 170 029), which contain special hydrazides as activator-stabilizer precursor compounds. When heated, these form basic compounds which enable the exposed silver halide to develop through the developer compound which is also present.

EP-A-02 19 087 describes photothermographic materials which contain a light-sensitive silver halide, a developer compound, a polymerizable compound, a color former and a combination of special hydrazine compounds. During the heat development, the color former is immobilized imagewise under essentially water-free conditions.

For a number of applications, in particular in the field of reproduction technology, a recording material with a gamma value of about 3 is not sufficient. Gamma values of at least 6, preferably over 10, are required there.

The object of the invention is therefore to provide a light-sensitive recording material for black-and-white images which can be developed by heat treatment and which can be developed to a gamma value of at least 6.

This object is achieved by a material according to the main claim.

It has been observed that the addition of hydrazine compounds which are substituted with an ethene group on one of their nitrogen atoms to a layer on the light-sensitive side of the dry silver material significantly increases the gradation of the image.

Examples of gradation-increasing compounds according to the invention are:

Particularly suitable compounds of this type are 1,1-diethoxycarbonyl-2-hydrazinoethene (compound I-1) and 1-ethoxycarbonyl-1-nitrilo-2-hydrazinoethene (I-10).

The amount of the characteristic compounds to be used is 0.001 to 1 mol per mol of the metal salt of the organic compound, preferably 0.01 to 0.1 mol.

Natural and synthetic polymers such as cellulose acetates, polyvinyl acetals, polyolefins, polymeric esters, for example terephthalic acid, polyamides, are used as binders. Poly- (N-vinyl) amides, polyvinyl / vinylidene chloride, polystyrene, polyacrylonitrile, polycarbonates and the like as well as copolymers of the monomers on which the polymers mentioned are concerned.

The non-photosensitive silver salt is preferably a salt of an unbranched fatty acid having 12 to 22 carbon atoms, for example lauric, myristic, palmitic, stearic, arachic or behenic acid, or a mixture of such salts. Silver stearate is particularly preferred.

Aromatic dihydroxy compounds such as hydroquinone, pyrocatechol or their precursor compounds can be used as reducing agents. Other compounds which act as photographic developers are also suitable, such as m- or p-aminophenols, 3-pyrazolidinones, ascorbic acid and their derivatives. Bisphenols, for example bis (2-hydroxy-3-t-butyl-6-methylphenyl) methane, are preferred. The reducing agent can be contained in the light-sensitive layer or also in a layer which is reactive with it, for example in an adjacent auxiliary layer. Its amount is usually 0.1 to 3 equivalents based on the total amount of reducible silver salts.

The dry silver material according to the invention can also contain a toner, as described above in the description of the prior art.

The photosensitive silver halide can be prepared "in situ" from the non-photosensitive silver salt by reaction with a limited amount of a compound that can release halide ions. Such compounds are, for example, the halides of the alkali metals and ammonium or organic N-halogen compounds such as N-bromosuccinimide, N-bromophthalimide, N-chlorophthalazinone, N-bromoacetamide and others. Other methods of this type are described in the publications cited in Research Disclosure No. 170029, Chapter I (June 1978) and No. 299063, Chapter XV (March 1989).

The silver halide is preferably produced in a separate operation ("ex situ") in an aqueous solution which contains a hydrophilic colloid, preferably gelatin. The methods of precipitation and chemical and spectral sensitization known from the conventional technique of photographic silver halide emulsions are used. The silver halide can then be separated from the protective colloid, for example by the process of GB 13 54 186. The isolated and optionally sensitized silver halide is then added to the coating composition for the light-sensitive layer of the dry silver material. Silver bromide and silver bromoiodide with an iodide content of up to 10 mole percent are preferred as the silver halide. The grain size of the silver halide is preferably between 0.05 and 0.5 μm, its share in the total silver salt content of the light-sensitive layer is generally less than 10, preferably 0.2 to 2 mol percent.

In addition to the photosensitive layer, the dry silver materials can contain further layers, for example auxiliary layers arranged above or below the photosensitive layer, such as protective layers or adhesion-promoting layers, or antihalo or anti-curl layers applied to the back of the support. In this case, it is preferred to add the gradation-increasing compound contained in the material to an auxiliary layer which is reactive in relation to the light-sensitive layer, ie which is arranged such that diffusion from this layer into the light-sensitive layer containing the silver salts and vice versa can take place . A protective layer arranged above the photosensitive layer, in particular a so-called overmolding, ie a layer which is arranged on the side of the layer package applied on the photosensitive side of the material, is particularly preferred for this purpose.

worin

X

Chlor oder Brom und

A

eine ggf. substituierte Aminogruppe oder eine Thioethergruppe bedeuten.

The dry silver material according to the invention preferably contains a fog-inhibiting compound in the light-sensitive layer or in a layer which is in a reactive relationship therewith. This in particular inhibits the formation of fog during the heat development. Examples of such compounds are given in the abovementioned prior art, in particular in Research Disclosure 299063, Chapter II (March 1989) and 170029, Chapter VII (June 1978), and also, for example, in EP-A-02 23 606, EP-A -04 97 053, EP-A-06 00 587 and EP-A-06 05 981. 1-Hydroxybenzotriazole and 1,2,3-benzotriazin-4 (3H) -one are also suitable. Particularly preferred anti-fog compounds are pyridazones of the general formula (A)

wherein

X

Chlorine or bromine and

A

is an optionally substituted amino group or a thioether group.

Both clear and colored or pigmented plastic films, for example made of polyethylene terephthalate or cellulose acetate, and also raw or coated papers can serve as layer supports.

With the dry silver materials according to the invention, images with a gradient of 10 to 15 can be generated.

These materials are characterized by good resistance even when stored in the unused state, especially with regard to the veil and the maximum density.

The processing latitude, ie the range of the combination of processing temperature and time allowed for a perfect image with minimal veil, is also included in the Materials according to the invention enlarged compared to the prior art.

The materials according to the invention can be used for the production of images by means of exposure and heat development, in particular for contact copies, projection enlargements and camera recordings in reproduction technology.

Embodiment

A photosensitive coating composition for a dry silver material was prepared in the following way:

In a pearl mill
196 g silver stearate,
1500 ml ethanol,
40 g of polyvinylpyrrolidone K 30 (molecular weight 40,000),
4 ml nonylphenol ethoxylate (10 EO) and
7 g behenic acid
ground with 1000 ml glass beads (2 mm diameter) with cooling for 18 hours. To check the degree of grinding, a sample of the dispersion was viewed under a microscope at a magnification of 100 times, no particles being visible. The coating solution thus prepared is designated A.

This dispersion was stirred
60 g polyvinylpyrrolidone,
1.28 g of mercury (II) chloride in 200 ml of ethanol,
16 g phthalazinone in 200 ml ethanol and
6.4 g of 5-nitroindazole in 250 ml of ethanol and
8 g of 4- (4-morpholinyl) -5-bromo-3- (2H) pyridazone
added. After the glass beads had been separated off, this coating solution B was ready for coating.

In a mixed solvent
400 ml methylene chloride and
80 ml of isopropanol were
4 ml nonylphenol ethoxylate (10 EO),
40 g polyvinyl butyral (molecular weight 36,000),
34 g of 3,3'-di-t-butyl-2,2'-dihydroxy-5,5'-dimethyldiphenylmethane
dissolved to form the coating solution C.

To prepare the coating solution D, 2.0 g of the compound I-10 were dissolved in a batch of solution C.

Coating solution B was applied with a layer thickness of 60 μm to a clear, colorless polyethylene terephthalate support and dried. Coating solution C or D was applied to the dry layer with a layer thickness of 100 μm and dried again.

In this way, dry silver films 1 and 2 were obtained, of which only film 2 contained the gradation-increasing compound according to the invention in the non-light-sensitive protective layer. Samples of these films were exposed imagewise in a contact exposure device through a wedge template and developed by contact with a metal surface that had a temperature of 105 ° C. for 15 s. The gradient measured between the transmission densities 0.1 and 3.0 was 2.7 for film 1 compared to 13 for film 2.

Claims (5)

Photographic recording material which can be developed by heat treatment and which contains at least one light-sensitive silver halide and one light-insensitive silver salt of an organic acid in at least one binder layer applied to a layer support, and in this or in at least one further layer which is reactive with this layer, a reducing agent and optionally a toner contains
characterized in that
at least one of these layers is a gradation-increasing compound of the general formula

contains what mean
R _{1 is} the group -CN or a group R ₄ -CO-,
R _{2 is} hydrogen, an alkyl group or an aryl group which is optionally substituted by alkyl and in each case in total not more than 12 carbon atoms,
R _{3 is} an alkyl, aryl, acyl or alkoxycarbonyl group with at most 12 carbon atoms or the group -CN,
R _{4 is} an alkyl, alkoxy or alkylamino group with 1 to 6 carbon atoms or an amino group, Material according to claim 1,
characterized in that
the compound of general formula (I) is 1,1-diethoxycarbonyl-2-hydrazinoethene or 1-ethoxycarbonyl-1-nitrilo-2-hydrazinoethene. Material according to claim 1 or 2,
characterized in that
the amount of the compound of the general formula (I) contained in the material is 0.001 to 1, preferably 0.01 to 0.1 mol per mol of the silver salt of the organic acid. Material according to one of claims 1 to 3,
characterized in that
the silver halide is formed ex situ and is chemically and possibly spectrally sensitized. Material according to one of claims 1 to 4,
characterized in that
the compound of the general formula (I) is contained in an auxiliary layer arranged over the light-sensitive layer.