JPS6332177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a thermally bleachable composition whose electromagnetic absorption properties can be changed by the application of heat, and a layer of such a composition. Concerning photographic elements. The layers described above are useful, for example, as filter layers or antihalation layers. A large number of photographic recording materials are currently known which can be processed by immersion in various processing solutions or baths.
It is also known to incorporate various filter layers (including filter overcoat layers), filter interlayers, and antihalation layers into such materials to produce improved photographic reproductions. The filtering or antihalation ability of these layers can generally be removed during processing of these photographic recording materials by some processing solution or bath. By doing so, it is possible to obtain treated materials that are transparent to the desired region of the electromagnetic spectrum, generally the visible region. Imaging elements are also known and can be processed after imagewise exposure by simply heating the element. These imaging elements include known thermally developable photographic elements (also known as photothermographic elements). It is particularly desirable for thermally developable elements, such as thermally developable photographic films, to have a filter layer or antihalation layer for improved microimaging capabilities. In most cases, these filter or antihalation layers must be rendered substantially transparent by heat treatment to avoid the use of processing solutions or baths. The antihalation layer of a photographic element functions to prevent light rays that pass through the radiation-sensitive layer from reflecting back into the photosensitive layer. If this unwanted reflection is not prevented, the sharpness of the resulting image will be reduced by this reflected light. Antihalation layers, as well as filter layers, have been proposed for use with thermally developable photographic elements. Antihalation layers in thermally developable photographic elements are known to change from colored to colorless upon exposure to heat or light. However, an independent activating component is not used in such an antihalation layer, and here antihalation protection is provided by a dye. However, these dyes generally require higher than desired temperatures before they change from colored to colorless. Additionally, another antihalation layer is known which is used in thermally developable photographic elements containing acidic components of the dye that are neutralized by a base provided by heating. There is. Such an antihalation layer is
For example, it is described in US Pat. No. 3,769,019 by Wiese et al. (the corresponding Japanese application is Japanese Patent Publication No. 16648/1983). Here, the dye is decolorized (colorless) by removing the acidic component by heating. One problem with this antihalation layer is that the dye in its colorless state cannot always remain in the desired state. In the case of such an antihalation layer, since there is a change from a colorless state to a colored state, an adverse effect appears on the image after development. This development can appear undesirably over a short period of time. Photobleachable antihalation layers containing photobleachable dyes are also known. However, providing a photosensitive antihalation layer requires an additional processing operation as a photobleaching step after processing.
Often not advantageous. In general, any layer that may be useful as an antihalation layer or filter layer in a photothermographic element may be useful alone on a support and therefore for thermographic imaging purposes. can provide useful elements. That is, imagewise heating of such elements can achieve thermal bleaching in the imagewise exposed areas. In this imaging method, any color change is useful in forming the image. For example, a substantially colorless dye precursor can be imagewise heated to form a positive color image. Colored dyes can also be imagewise exposed to heat to form a colorless material, thus providing a negative-working image. Note that there are many known thermographic elements that can be used with this concept. Imagewise heating of the element for a short period of time causes migration of the reactants and thus colorlessness in the imagewise heated areas. Many thermographic elements are also useful for making reflective copies, writing with heated pens, or imagewise exposure using lasers. It is also known to image-wise change formazan dyes from colored to colorless by using reducing agents. This imagewise color change method is used, for example, in Research Disclosure , 1974
October, Item 12617, pp. 12-30, Publisher:
Industrial Opportunities Ltd., Homewell,
Havant, Hampshire, P09, 1EF, UK. However, there remains a need to provide new and improved combinations of materials and dyes for thermographic imaging. This type of requirement is particularly imposed on materials in which the color change is more permanent and provides a more stable image. A variety of hexaarylbiimidazole compounds are known for use in imaging elements in which a colorless compound is photolytically converted to a colored compound in the imagewise exposed areas of the element. Imaging materials using hexaarylbiimidazole compounds are currently known, and these materials include what is described as a free radical imaging mechanism, such as that described in U.S. Pat. No. 3,390,994. are doing. Additionally, in the section on heat-developable photographic elements comprising formazan dyes and hexaarylbiimidazole, no discussion regarding the formation of a colorless layer can be found. The above-mentioned elements having a heat-bleachable layer, in particular photothermographic elements containing a heat-bleachable filter layer or an antihalation layer, each suffer from at least one of the following disadvantages: have. (1) Undesirably high temperatures are required to bleach the layer. (2) In many cases, even when dyes are bleached, they are not sufficiently stable and may cause undesirable staining or loss of color after long-term storage after processing. There is a tendency to occur. (3) Considering the purpose of the antihalation and filter layers, the selection of suitable dyes is undesirably limited. Additionally, there is now a need for antihalation layers that provide the desired neutral color for use in photothermographic films. According to the present invention, the problems of the conventional techniques as described above can be solved by (i) a hexaarylbiimidazole compound represented by the following formula: (In the above formula, R and R' are each hydrogen or an alkyl group having 1 to 4 carbon atoms) and (ii) formed when the above hexaarylbiimidazole compound is heated. a thermally bleachable composition comprising a dye selected from the group consisting of formazan, azo, polymethine and oxanol dyes, which is reactive with the product, and a layer comprising such a composition. This can be solved by photographic elements. These inventions will be described in detail below: As a result of intensive research, the present inventors discovered the following components:
In a photographic element comprising: (a) a support, (b) a photosensitive component disposed on said support, and (c) a filter component contained within or above said support. We have found that improvements can be achieved. That is, according to the present invention, the filter component comprises (i) at least one hexaarylbiimidazole as detailed below; and (ii) the hexaarylbiimidazole formed when heated to a temperature of at least about 90°C. containing in reactive combination at least one antihalation dye or filter dye that is reactive with the product (the product of hexaarylbiimidazole) and,
said filter component by at least 40%, preferably at least 90%, becoming colorless within about 20 minutes, generally within about 0.5 minutes, when heated to a temperature of at least about 90°C; Improvements such as this can be achieved. The antihalation or filter components described herein are particularly advantageous because of their post-processing stability. Furthermore, the layer of this component can become at least 40% colorless upon heating and exhibit good shelf life/storage stability. These advantages are based on the following components: (a) a support, in particular a transparent film support, (b) at least one photosensitive layer applied on said support, and (c) within or on said support. at least one type of antihalation component contained above, the antihalation component comprising: (i) at least one type of antihalation component;
and (ii) at least one formazan antihalation dye, and when heated to a temperature of at least about 90°C, said halation occurs within about twenty minutes This is particularly evident in photographic elements according to the invention in which at least about 40%, preferably at least about 90%, of the inhibiting component is colorless. Colored thermally bleachable elements according to the present invention are useful for improved imaging using a variety of methods. These advantages, therefore, include (i) at least one hexaarylbiimidazole as detailed below and (ii) heating the hexaarylbiimidazole to a temperature of at least about 90°C, generally at least about 120°C. a colored heat-bleachable composition containing in reactive combination at least one dye that is reactive with its product (the product of hexaarylbiimidazole) when may turn essentially colorless within about 20 minutes, generally within about 30 seconds, when heated to temperatures down to about 90°C. One embodiment of the present invention represented by such a form comprises a support, and a support provided thereon, comprising: (i) at least one hexaarylbiimidazole as described below; and (ii)
at least one dye, in particular at least one formazan dye, which is reactive with the hexaarylbiimidazole product after heating to a temperature of at least about 90° C.; and (iii) a binder. at least one layer comprising a conjugate of at least 40% of the conjugate, preferably at least 90% of the conjugate within 30 seconds after heating to a temperature of at least 120°C. %, changes to colorless. A variety of hexaarylbiimidazole compounds are useful in photographic recording materials according to the invention. These hexaarylbiimidazole compounds, also referred to herein as "oxidized arylimidazoyl dimers," are known compounds and can be prepared by methods known in the art. For example, hexaarylbiimidazole is hexacyanoferric () as the oxidized form.
It can be prepared by interfacial oxidation of the starting triarylimidazole using potassium acid. Common hexaarylbiimidazole compounds useful in accordance with the present invention include:
For example, they are described in the following US patents and can be arbitrarily selected from them: 3734733; 339097; 3383212; 3445234;
3395018; 3390994; 3615481; 3666466; 3630736
and ;3533797. Common examples of useful hexaarylbiimidazole compounds include oxidized 2,4,5-triarylimidazolyl dimers in which the aryl group is a p-isopropylphenyl group,
It is an aryl group selected from the group consisting of p-methoxyphenyl group, p-n-butylphenyl group, p-methylphenyl group, and p-ethylphenyl group. A particularly useful compound has the following formula: () (In the above formula, R and R' are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group and a butyl group) It is an oxidized arylimidazoyl dimer of the compound. If desired, mixtures of hexaarylimidazole compounds can also be used advantageously. An example of such a mixture is, for example, a compound represented by the above structural formula () in which R and R' are hydrogen atoms, and (a) a compound represented by the above structural formula () in which R and R' are hydrogen atoms. is a mixture with (b) where is an isopropyl group. The selection of the optimal hexaarylbiimidazole compound or mixture of such compounds depends on a variety of factors, such as the particular antihalation dye or filter dyes to be used, the processing conditions, and the dye in the dye-containing layer. will depend on the degree of bleaching desired or the solubility characteristics of the ingredients. According to the invention, various dyes and dye precursors can be advantageously used with the hexaarylbiimidazole compounds described above. According to the present invention, any dye or dye precursor that changes color, i.e., by reaction with what is believed to be a free radical formed by heating the above-mentioned hexaarylbiimidazole compound, Any dye or dye precursor that has altered electromagnetic absorption properties can be used. For antihalation layer purposes, for example, it is desirable that the heat-bleachable layer exhibit substantially uniform absorption in the spectral region to which the imaging composition is sensitive. Additionally, the antihalation dye or dye precursor comprises at least about 40% of the layer containing it.
Preferably at least 90% should change color from colored to colorless or to such an extent that the layer has substantially no optical density. Various dyes are known as dyes that can be bleached or converted to a colorless state. Formazan dyes and azo dyes are examples of useful dyes. A particularly useful antihalation dye is a formazan dye. Useful formazan dyes can be represented, for example, by the following structural formula. In the above formula, R ² is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 14 carbon atoms, such as methyl, ethyl, hexyl, phenyl, p-nitrophenyl. and a dimethoxyphenyl group, R ³ being an aryl group having 6 to 14 carbon atoms, preferably, for example a p-nitrophenyl group,
a phenyl group, including substituted phenyl groups such as p-methoxyphenyl and anthraquinonyl, and R ⁴ is an aryl group having 6 to 14 carbon atoms, preferably, for example a p-nitrophenyl group,
p-methoxyphenyl group and phenyl group including substituted phenyl groups such as anthraquinonyl group. Particularly useful formazan dyes are, for example, the compounds described below. 1 1,3,5-triphenylformazan 2 1-(4-chlorophenyl)-3,5-diphenylformazan 3 1-p-nitrophenyl-3,5-(diphenyl)formazan 4 1,5-diphenyl-3- Methylformazan 5 1,5-diphenyl-3-(3-iodophenyl)formazan 6 1,5-diphenyl-3-(2-naphthyl)
formazan, and 7 1-(2-carboxyphenyl)-3,5-
Diphenylformazan Other useful formazan dyes include, e.g.
Research Disclosure (ibid.), October 1974,
Item 12617, pages 12-30. In order to obtain the desired absorbance, mixtures of formazan dyes can be used with particular advantage. An example of such a mixture of formazan dyes is
For example, a mixture of triphenylformazan and 1-(p-nitrophenyl)-3-methyl-5-phenylformazan can be mentioned. Formazan dyes and methods of their preparation are known in the art. For example, Chemical
Formazan dyes can be prepared using techniques known in the art, such as those described in Reviws, 1955, p. 356 et seq. The coating amounts and proportions of the various components constituting the dye-biimidazole conjugate of the present invention as described above will vary depending on, for example, the specific use, the position of the antihalation component or filter component within the element, the desired absorbency, or Depending on the various filters, the processing temperature can be varied over a wide range. For example, in some thermographic applications, the concentration of the dye may be sufficient to provide an optical density of at least about 0.05. To provide discrimination, the hexaarylbiimidazole is used in an amount sufficient to reduce the concentration of the dye to (at least) such a degree as to provide the desired image when the element is heated above about 70°C. It is necessary to make it exist. On the other hand, for purposes of preventing halation, it is desirable that the concentration of the dye be sufficient to provide an optical density of at least about 0.2, such as from about 0.3 to about 0.8. The hexaarylbiimidazole must be present in a minimum sufficient concentration to effect bleaching of at least 40% of the dye as described above. For example, when using a formazan dye, useful concentrations of hexaarylbiimidazole are from 0.2 to 10 moles per mole of formazan dye. Typically,
Excess amounts of the hexaarylbiimidazole compound can be used to ensure the desired degree of reaction with the dyes described above in elements in which the dyes are used for antihalation purposes. A preferred molar ratio of hexaarylbiimidazole compound and dye is about 0.4 to 3.0, and a particularly preferred molar ratio is about 1.0 to 1.5. However, the exact mechanism by which the dyes and dye-containing layers described above change from colored to colorless has not yet been fully understood. However, hexaarylbiimidazole compounds form radicals upon heating, and these radicals then react with the dye in a way that changes the structure of the dye into a colored material with a lighter color. It is thought that they may do so. It is believed that this reaction significantly contributes to the great stability of the colorless layer after heating. Elements according to the invention can contain various colloids and polymers, alone or in combination, which can be included as vehicles, binders, and in various layers. Suitable materials include hydrophilic materials and hydrophobic materials. These colloids and polymers are transparent or translucent and the inclusions in these colloids and polymers do not adversely affect, for example, reactions that change dyes from colored to colorless and are compatible with the processing temperatures used. It is a durable material. These colloids and polymers include, for example, proteins such as gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, etc., and synthetic polymeric materials such as water-soluble polyvinyl compounds such as poly(vinylpyrrolidone). ), acrylamide polymers, and others. Other synthetic polymeric compounds which can be advantageously used here include, for example, dispersed vinyl compounds in the form of a latex. Useful polymers include high molecular weight materials, polymers and resins that are compatible with the imaging materials of the elements of this invention. When using formazan dyes with hexaarylbiimidazole to prevent halation, useful binders are polysulfonamides. A useful polysulfonamide binder is poly(ethylene-co-1,4-cyclohexylene-dimethylene-1-methyl-2,4-benzenedisulfonamide) binder. If desired, mixtures of colloids and polymers as mentioned above can also be used advantageously. moreover,
Latexes that are compatible with water-insoluble polymers such as poly(vinyl butyral), such as BUTVARB-76 (trade name of a product manufactured by Monsanto, USA) and antihalation or filter compounds, are also suitable. Useful. Antihalation layers as described above can be advantageously used in a variety of photographic elements.
Useful photographic elements are those constructed in which an image, such as a color image, is derived from photographic silver halide or those constructed for non-silver imaging processes. Photographic elements configured for microimaging are particularly useful when using antihalation materials according to the invention. Hexaarylbiimidazole compounds and dyes,
Conjugates such as those described above, particularly with formazan dyes, can be interposed at any suitable location within the imaging element so that the desired bleaching of the dye can be achieved after heating. Among the constituent components of the image forming element according to the present invention, components other than those mentioned above can be interposed at any appropriate position within the element to form a desired image.
For example, if desired, one or more components of an imaging element according to the invention may be present in one or more layers of the element.
Optionally, specific amounts (proportions) of reducing agents, image stabilizers or their precursors, dyes and/or other additives as described above are incorporated into the protective layer on the thermally developable element. Sometimes it is desirable. In some cases, through doing so, migration of certain additives between layers of the element as described above can be reduced. In order to provide the desired image, it is necessary to reactively combine the imaging components contained in photographic elements according to the invention with one another. moreover,
It is also necessary to reactively combine the dye and the hexaarylbiimidazole compound with each other to effect the desired thermal bleaching within the imaging element. Note that "reactively combining" is often used in this specification.
The term indicates that the components are oriented and relative to each other as described above to permit the desired processing and thermal bleaching and to provide a more effective developed image. It is used to explain. Additionally, the term refers to a compound in which the hexaarylbiimidazole compound and the dye are brought into position relative to each other such that when the compound and the dye are heated as described above, the desired change in the dye from colored to colorless is possible. It is also used to explain what is happening. For example, one of the components can be present in one layer of the imaging element and the remaining components can be present in one or more other layers (provided the components are combined reactively). . As mentioned above, the heat-developable photographic recording material of the present invention contains a photosensitive component, and this photosensitive component may be either a silver-sensitive component or a non-silver photosensitive component. . When using silver photosensitive elements, photosensitive silver halides may be particularly useful because they have superior photosensitivity compared to other photographic elements. Typical concentrations of light-sensitive silver halide contained within heat-developable photographic elements according to the invention range from about 1 x 10 ^-4 per square meter of support to about
10 ^-1 mole. Preferred photographic silver halides are silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof. For purposes of this invention, silver iodide is also one of the useful photographic silver halides.
It is thought that this is the case. Ultrafine grain photographic silver halides are also useful, although coarse grain or fine grain photographic silver halides can be used if desired. Photographic silver halides can be prepared using any of the techniques known in the photographic art, particularly those involving the preparation of photographic silver halide-gelatin emulsions. Preparation methods and forms of photographic silver halide useful for the purposes of the present invention are described, for example, in Product Licensing
Index, Volume 92, December 1971,
Publication9232, 107 pages, Publisher: Industrial
Opportuities Ltd. (supra).
Also, Research Disclosure (cited above)
Vol.148, August 1976, Item 14879 and same book 1974
The silver halide compositions described in September 2003, pages 43-45 are another example of useful silver halide materials. Particularly useful photosensitive components are those intended for microimaging. Thermally developable photographic elements as described above can have a variety of reducing agents, particularly organic reducing agents (generally photographic silver halide developers). These reducing agents can also be used advantageously in combination. Particularly useful reducing agents include silver halide developers containing polyhydroxybenzene, aminophenol reducing agents, ascorbic acid developers,
Hydroxylamine reducing agents, 3-pyrazolidone reducing agents, reductone reducing agents, gallic acid ester reducing agents, such as Research Disclosure (ibid.),
and phenylenediamine silver halide developers, such as those described in J. 1973, pp. 16-21. Particularly useful thermally developable photographic elements can contain mixtures of reducing agents as described above. The optimal concentration of the reducing agent can be determined, for example, depending on the desired image,
The determination can take into account various factors such as other components included in the heat-developable material, processing conditions, etc. “Reducing agent” as used herein
The term is used to include therein the reducing agent precursor as well as the reducing agent itself. That is, the reducing agent precursor can include a compound such that the reducing agent is formed upon heating or upon exposure to some other condition (at a desired time). Imaging elements according to the present invention may contain imaging toners, ie toning agents, to provide a neutral or black image with better tone after processing. The optimal imaging toner or toning agent is, for example, a specific imaging material,
It will depend on various factors such as the desired image, specific processing conditions, etc. In some cases, certain image toning agents or toners can produce much better results with certain imaging materials than with other materials. . If desired, toning agents or toner mixtures can be advantageously used. The optimum concentration of toning agent or toning agent mixture will depend on various factors such as, for example, the particular imaging material, processing conditions, or desired image. It is also often useful to include melt-forming compounds or melt formers in imaging elements according to the invention, such as in the imaging layer and in the antihalation layer or filter layer as described above. Also, if necessary, melt-forming compounds or mixtures of melt-forming bodies can be advantageously used. As used herein, the term "melt-forming compound" or "melt former" refers to a compound that forms a modified reaction medium, generally a molten medium, after heating to a given processing temperature. It is therefore used to refer to compounds in which reactive conjugates such as those described above may result in better images in this medium. Although the exact properties of this reaction medium at the processing temperature are not yet completely clear, a melt is formed at the reaction temperature, and this melt is responsible for the interactions between the reaction components. It is thought that the reason is to improve the reaction. Useful melt-forming compounds are usually separate and independent components from the reactive conjugate, although they can participate in melt formation. Generally useful melt-forming components are those that are compatible with other components of the material of the present invention, such as amides, imides, and cyclic ureas. and triazoles. Useful melt-forming compounds or melt formers include:
For example, Research Disclosure (ibid.),
Described in Vol. 150, October 1976, Item 15049. As mentioned above, the antihalation layer or filter layer of the present invention can contain a melt-forming compound, if necessary. A wide range of concentrations of melt-forming compounds or melt formers are useful in thermally developable photographic elements such as those described herein. The optimum concentration of melt-forming compound will depend on various factors such as, for example, the particular imaging material, the desired image, or processing conditions. In the imaging elements and compositions of the invention as described above, spectral sensitizing dyes or mixtures thereof can be advantageously used to impart additional sensitivity to those elements and compositions. Useful sensitizing dyes are described, for example, in Product Licensing Index (ibid.), Vol. 92, December 1971, Publication 9232;
Pages 107-110, Section XV. Imaging elements according to the invention can further have a wide range of pAg values. Here, the pAg value can be measured by using a conventional calomel electrode and an Ag-AgCl electrode connected to an Orion digital PH meter. Typical pAg values range from about 2 to about 13 in thermally developable photographic elements according to the invention. The optimal pAg value will depend on various factors mentioned above, such as, for example, the particular imaging element, the desired image, or processing conditions. Imaging elements according to the present invention generally have a PH range that leans toward the acidic side of the neutral range, ie, a PH value of less than about 7. For thermally developable photographic elements according to the present invention, a generally useful range of PH values is from about 2 to about 6, preferably from about 3.5 to about 5.0. The biimidazole-dye conjugate described above also has a neutral range that leans toward the acidic side, that is, a PH of less than about 7.
useful in value. In the aforementioned imaging elements according to the present invention, it is often desirable to use a stabilizer or stabilizer precursor in the element to improve the stability of the image after processing. In some cases, thermally developable photographic elements according to the present invention may be sufficiently stable in the absence of a separate stabilizer or stabilizer precursor. However, in many cases where photographic silver halide is used as a light-sensitive component, the silver halide must be stabilized after processing is complete to avoid undesired post-processing print-out. This is desirable. A variety of stabilizers or stabilizer precursors are useful in thermally developable photographic elements such as those described above. These stabilizers or stabilizer precursors may be used alone or in combination, if necessary. Generally useful stabilizers or stabilizer precursors are sulfur-containing compounds that can form stable silver mercaptides by heating them in a thermally developable photographic element. Useful stabilizers or stabilizer precursors are, for example, those described in Belgian Patent No. 768071.
Furthermore, if necessary, polyhalogenated organic compounds activated by photolysis can also be advantageously used. Such photolytically activated polyhalogenated organic compounds are described, for example, in US Pat. Nos. 3,874,946 and 3,707,377. A wide range of concentrations of the stabilizer or stabilizer precursor or mixtures of these compounds to be included in the imaging elements described above are useful. The optimum concentration of stabilizer or stabilizer precursor or mixture of these compounds will depend on various factors such as, for example, the particular imaging element, processing conditions, or desired stability. In the imaging elements of the present invention as described above, development activators (also known as alkali-releasing agents, base-releasing agents or activator precursors) can be advantageously used. The term "development activator" as used herein means a medium or compound capable of assisting a developer to develop a latent image within an imaging element at processing temperatures. ing. Useful developer activators or activator precursors include:
For example, Belgian Patent No. 709967 and
Research Disclosure (cited above), Vol.155, 1977
March, Item 15567. Useful activator precursors include, for example, guanidinium compounds such as guanidinium trichloroacetate,
diguanidinium glutarate, diguanidinium succinate and diguanidinium malonate; quaternary ammonium malonate; amino acids such as 6-aminocaproic acid and glycine; and; 2-carboxycarboxamide activator precursor. In some cases, e.g.
It is useful to coat one "overcoat" layer over the imaging layer and antihalation layer or filter layer according to the invention. The overcoat layer can be one or more of the aforementioned polymers that are also useful as binders. However, other polymeric materials that are compatible with the imaging layers of the elements of the invention and can tolerate the applied processing temperatures may also be used to advantage. Such other binders or polymeric materials include, for example, cellulose acetate and polyvinyl chloride.
It is also useful, if desired, to provide mixtures of these polymeric materials for overcoating purposes. Imaging elements, particularly photographic silver halide imaging elements, according to the invention may contain other additives, such as development modifiers, hardeners, plasticizers and lubricants, coating aids, which act as speed-enhancing compounds, It may contain brighteners, antistatic agents or antistatic layers or antifoggants. These additives are described in, for example, Product Licensing Index (ibid.), Vol. 92, December 1971, Publication 9232,
It is described on pages 107-110. Imaging elements according to the invention can have a variety of supports capable of tolerating the processing temperatures applied according to the invention. Common supports include, for example, U.S. Pat.
Cellulose ester film, poly(vinyl acetal) film, poly(ethylene terephthalate) as described in No. 3725070
Mention may be made of film, polycarbonate film and polyester film supports. Additionally, related film and resinous supports, as well as glass, paper, metal, and similar supports that can withstand certain processing temperatures are also useful. Generally, flexible supports are most useful. Antihalation compounds include conjugates of dyes (particularly formazan dyes) and hexaarylbiimidazole compounds, as described above. The antihalation compound can optionally be present in a transparent support, such as a transparent film support. For example, cellulose triacetate and polyester film supports useful for thermally developable photographic elements can contain combinations of hexaarylbiimidazole compounds and dyes, particularly formazan dyes, as described above. The antihalation and filter components of this invention, as well as the other compositions described above, can be coated onto a suitable support using a variety of coating methods known in the photographic art. Although various components are useful in antihalation layers according to the present invention as described above, among such components, there are particularly
It is often desirable to have a conjugate that is 90% colorless. This conjugate can be advantageously used in photothermographic elements as described above. Also, this combination is
It can also be used advantageously in thermographic elements. In some cases, a low concentration of the biimidazole compound-containing conjugate, typically support 1
It is useful to include up to about 6 mg per square foot of 1-naphthoic acid. Like this 1-
The presence of naphthoic acid can alleviate the disadvantage of volatile components being released from the conjugate containing the biimidazole compound.
Other acids that may also be useful include, for example, 2-naphthoic acid and benzoic acid. Furthermore, the desirability of adding a separate acidic compound can also be influenced through the selection of a suitable binder. One particularly useful embodiment of the invention comprises the following components: (a) a support, (b) at least one photosensitive silver halide layer disposed on said support, and (c) at least one antihalation layer, the antihalation layer comprising (i) at least one compound represented by formula () as described above; (ii) at least one formazan dye; and (iii) at least one formazan dye. containing in reactive combination a polymeric binder comprising a maleic anhydride-styrene copolymer and at least about 90% of the antihalation layer within about 30 seconds when heated to a temperature of at least about 120°C. It is a photographic element in which % changes to colorless. Various imagewise exposure means are useful in forming images according to the present invention. The elements according to the invention are normally sensitive to the ultraviolet and blue regions of the spectrum, and the exposure means are therefore advantageously those which emit such radiation. Generally, however, if spectral sensitizing dyes are used in the photographic elements described above, exposure means using other regions of the electromagnetic spectrum are advantageous. Typically, photosensitive elements according to the invention can be subjected to imagewise exposure using a visible light source, such as a tungsten lamp, to form a developable image. However, other radiation sources can also be effectively used, such as laser beams, electron beams, etc. In the case of a thermographic element according to the invention, the imagewise heating means used herein may be any heating means capable of forming a visible image in the heated region of the element.
Examples include simple hot plates, infrared heating means, and the like. In a thermally developable photographic element according to the invention,
By simply uniformly heating the thermally developable element to a suitably elevated temperature, a visible image can be developed within a short time after imagewise exposure. For example, after the imagewise exposure is completed, the latent image is developed, but at the same time it is thermally developed to a temperature range that provides the temperature necessary to change the antihalation layer or filter layer from colored to colorless. Possible photographic elements can be heated. The temperature range for the above heating is about 90 to about 250°C, for example about 90°C.
~250°C. Heating can generally be carried out until the desired image is developed and the antihalation layer or filter layer is bleached to the desired degree. This heating time is
Generally, from about 1 second to about 20 minutes, such as about 1
seconds to about 90 seconds. Thermally developable photographic elements of this invention are typically heated to a temperature of about 90 DEG to about 250 DEG C. for a period of about 1 second to about 20 minutes. Another aspect of the invention includes (a) developing an image in a photothermographic element after exposure as described above, and (b) converting the antihalation component contained in the element from a colored state to a colorless state ( at least 40%, preferably at least 90%), said color changing step (b) comprising at least 40% of the antihalation component
Preferably comprising heating the element to a temperature of at least about 90°C until at least 90% changes from colored to colorless. Thermally developable photosensitive elements according to the present invention are useful for forming negative-working or positive-working images. Here, forming a negative or positive image, for example, will depend primarily on the selection of a particular photosensitive silver halide. One class of useful photosensitive silver halide components is the group of direct positive photographic silver halides whose purpose is to form positive working images. Processing according to the invention is typically carried out under ambient pressure and humidity conditions. Of course, pressures and humidity outside standard atmospheric conditions can be used if desired. However, it is advantageous to use standard atmospheric conditions. A variety of heating means can be used to provide the necessary heating to the thermally developable photographic or thermographic elements of the present invention as described above. Such heating means can be, for example, a simple hot plate, an iron, a roller, an infrared heating means, or the like. It is often desirable to use organic solvents to aid in the preparation of the coatings used to make the photographic elements of this invention, since for some compounds their solubility is only limited. from). Common organic solvents useful for preparing compositions for coatings such as antihalation layers or filter layers according to the invention are, for example, tetrahydrofuran, methylene chloride, acetone and butanol. moreover,
using means known in the field of photographic technology,
It is also possible to carry out mixing of these solvents with the aforementioned components (according to the invention). The antihalation component or filter component according to the present invention may be a photosensitive diazo compound, if necessary.
type materials, cellular imaging materials or other non-silver imaging materials. The examples detailed below are provided to further facilitate understanding of the present invention. Example 1 An oxidized dimer of 2,4,5-triphenylimidazole (also known as lofin dimer) was prepared according to the procedure described in Journal of Organic Chemistry , 36 , p. 2265 (1971). Next, 35 mg of this was taken and dissolved in 1 g of tetrahydrofuran. To the resulting composition was added 2 g of polysulfonamide:poly(ethylene-co-1,4-
cyclohexylene dimethylene-1-methyl-2,
A 20% by weight acetone solution of 4-benzenedisulfonamide) was added. 7 mg of 1,5-diphenyl-3-(p-methoxyphenyl) formazan dye was dissolved in this solution. The resulting dye solution was coated onto a poly(ethylene terephthalate) film support at a wet film thickness of 6 mils (using a doctor blade coater). The resulting coating was dried to obtain a thermally bleachable element according to the invention. Heating by placing the resulting element on a hot metal block at a temperature of 150 DEG C. and contacting them for a few seconds caused rapid and complete bleaching of the element. The activation enthalpy was determined from the bleaching rate at temperatures of 90°C and 112°C and was approximately 29 Kcal/mol. Example 2 The procedure described in Example 1 above was repeated using methylene chloride solvent in place of tetrahydrofuran. The dye-containing composition was coated onto a poly(ethylene terephthalate) film support at a wet film thickness of 2 mils. The coating amount of the dye-containing composition applied onto the support was as follows. Oxidized duplex of 2,4,5-triphenylimidazole 4.8 mg/dm ² Triphenylformazane dye 1.1 mg/dm ² Binder (see table below) 21.5 mg/dm ² When such a polymer was used, the following results were obtained. [Table] Isopropylidene diphenylene
Len isofta
rate-co-
Terephthalate (50:50)
In order to subject the obtained elements to heat and humidity tests, 50
% relative humidity and a temperature of 38°C. The results obtained showed that even after 3 weeks of incubation, the loss of dye concentration was minimal and no significant loss of bleaching was observed. It was also shown that the sample that had been incubated and pre-bleached did not lose its color even after 3 weeks under the above-mentioned incubation conditions. Example 3 The procedure described in Example 2 above was repeated. The binder used was also as described in Example 2, and the concentrations of each component contained in the coating were as follows. Oxidized dimer of 2,4,5-triphenylimidazole 5.4 mg/dm ² Triphenylformazane dye 3.2 mg/dm ² Polyester binder (as described in Example 2) 21.5 mg/dm ² p-trienesulfonic acid 1.1 mg/dm dm ² The coating was dried as described in Example 2 above.
Although heated as described at a temperature of 160° C. for 10 seconds, no volatile components were observed to be released from the acid-containing coating. Example 4 A tetrahydrofuran composition similar to that described in Example 2 above was prepared. The ingredients contained in the paint film are
It was as follows. Triphenylformazane dye 1.1mg/dm ^{2Polysulfonamide} binder 21.5mg/ ^dm Molar ratio of imidazole dioxide dimer 0.5 to 2.75
mol (in both cases, the number of moles of dimer per mole of dye), and the increment of the number of moles in that case is
The amount was 0.25 mole each. The results obtained were compared with those of unbleached coatings. Comparison results showed that the optimum level in a particular composition was about 1.6 moles per mole of dye (in dimer as described above). Therefore, excellent bleaching properties were obtained for the coatings when heated at a temperature of 160° C. for 5 seconds. Excellent bleaching properties were also obtained when the coating was heated at 150°C for 10 seconds. The bleaching properties of the coating were good at a temperature of 140°C when it was heated for 10 seconds, but were less desirable when the coating was heated for 10 seconds at a temperature of 130°C. Nakatsuta. Example 5 A tetrahydrofuran composition was prepared similar to that described in Example 2 above and containing the following ingredients. Triphenylformazane dye 1.1 mg/dm Imidazole ² oxide dimer (as described in Example 2) 3.4 mg/dm ² Polysulfonamide binder and this composition
Mixing was carried out at concentrations ranging from 50 to 400 mg/ft ² (corresponding to 5.4 to 43.1 mg/ft ² ), ie varying concentrations within this range. When the resulting coatings were incubated for four weeks at a temperature of 38°C and 50% relative humidity, the researchers found that the higher the amount of pigment lost during incubation, the lower the level of polymer. It has been found. In addition, when the polymer coating amount is 37.7 mg/dm ² ,
The dye loss after 4 weeks incubation is less than 20% and the dye loss after 2 weeks incubation is about 10%.
It was also found that %. When we tried changing the composition of the composition, we were able to find various correlations regarding stability. Example 6 A tetrahydrofuran composition was prepared similar to that described in Example 5 above and containing the following ingredients. Triphenylformazane dye 1.1 mg/dm ² Oxide imidazole dimer 3.8 mg/dm ² Polysulfonamide binder (as described in Example 1) 32.3 mg/dm ² To this composition it was added as described in Example 5 above. 2.5, 5, 10 and 20 before coating on the support.
mg/ft ₂ (compatible with 0.2, 0.46, 0.93 and 1.87 mg/ft ² )
The following acids were added at a coverage of . p-Toluenesulfonic acid 1-naphthoic acid The results obtained after incubation showed that lower levels of 1-naphthoic acid (5 mg/ft ² ) resulted in less loss of dye upon incubation and a slight increase in processing speed. It was also established that the staining observed after bleaching the resulting paint film was clearly unaffected. Example 7 A tetrahydrofuran composition similar to that described in Example 5 above and containing the following ingredients was prepared. Triphenylformazane dye 1.1mg/ ^dm Imidazole dioxide dimer 5.4mg/dm ² copoly(maleimido-styrene)
(50:50 parts by weight), 21.5 mg/ ^dm2 , commercially available from Monsanto Company, USA under the trade name Lytron 820. This composition was coated on a support and heated. The resulting coating film was instantly bleached and turned into a colorless substance, and no volatile components were observed with the naked eye. Example 8 This example is a comparative example. A coating containing the following ingredients was prepared using a tetrahydrofuran composition similar to that described in Example 5 above. Triphenylformazane dye 1.1 mg/ ^dm Imidazole dioxide dimer 3.2 mg/dm ² (see below) Folysulfonamide binder 21.5 mg/dm ² (as described in Example 1 above) Included in the above composition The imidazole dimer is
There are two types below. 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer The above composition was mixed with p-toluenesulfonic acid (additive ). If p-toluenesulfonic acid is used, the applied amount is 5 mg/ft ² (0.46
mg/ ^dm2 ). After coating the above composition on a suitable support, the resulting coating film was subjected to heat treatment. 30 at a temperature of 200℃
After heating for several seconds, minimal bleaching was observed in the coating. This fact indicates that even if the imidazole dimers are present in the composition, they will resist thermal decomposition (which should be maximally useful at the temperature and time used). This shows that it is too stable. Example 9 Some oxidized imidazole dimers have limited solubility in certain solvents. For example, the solubility of certain imidazole dimers is limited to methylene chloride and tetrahydrofuran compositions. In this example, an acetone composition was prepared by mixing the following ingredients and coating the resulting mixture onto a clear poly(ethylene terephthalate) film support. Triphenylformazane dye 1.1 mg/ ^dm Oxidized dimer of solubilized imidazole with quadratic formula: 4.0 mg/dm ² Polysulfonamide binder 32.3 mg/dm ² (as described in Example 1 above) After coating the above composition on a film support,
The resulting coating was dried and then heat treated by heating the element for 10 seconds at a temperature of 160°C. In this example, it was possible to achieve good bleaching of the coating film. Before bleaching, the coatings were incubated for 4 weeks at a temperature of 38° C. and a relative humidity of 50%. As a result, although a loss of 37.5% in dye density was observed,
No loss of bleaching ability was observed at 160°C. Example 10 Additional imidazole dimer was included in the heat-bleachable layer. The additional dimer used in this example was a solubilized imidazole oxidized dimer of the compound represented by the formula: [Table] Coatings were prepared using tetrahydrofuran as the coating solvent. The levels (coating amounts) of the components used were as follows. Imidazole oxide dimer 3.7 mg/dm ² Triphenylformazane dye 0.93 mg/ft ² Polymer binder 28.0 mg/dm ² The polymer binder used here was a maleic anhydride-styrene copolymer (commercially available from Monsanto Company, USA). Lytron 820) or polysulfonamide binder: poly(ethylene-co-1,4-cyclohexylene-dinatylene-1-
methyl-2,4-benzenedisulfonamide). To obtain the element according to the invention, the coating was dried. Incidentally, when the obtained composition was applied onto a poly(ethylene terephthalate) film support, the thickness of the wet coating film was 2 mils. When the resulting element was heated at a temperature of 160° C. for 10 seconds, the bleaching properties of the element were found to be good for each of the two polymeric binders and the imidazole dimer. This was confirmed. Also, the lowest contamination was observed at 400 nm absorption. When a maleic anhydride-styrene copolymer was used as the binder, better thermal stability was observed. Example 11 The procedure described in Example 10 above was repeated using compound 10B. However, in this example, acetone was used instead of tetrahydrofuran. This dimer 10B
was found to have excellent solubility in acetone compositions. The coating film containing this dimer 10B is
It showed excellent bleaching action at a temperature of 160°C when heated for 10 seconds. Example 12 In this example, the aforementioned oxidized, tris-substituted, imidazole dimer (Compound 10C in Example 10) was incorporated into a composition using a similar procedure as described in Example 10 above. The triphenylformazane dye used was 0.9 mg/dm ² and maleic anhydride.
The polymer binder is made of a styrene copolymer.
It was 28mg/ ^dm2 . Good bleaching properties were observed when the resulting coating was heated at a temperature of 160° C. for 10 seconds. Good results were also observed when the aforementioned tris-substituted dimer (compound 10C) was applied at relatively high levels (coverage). Examples 13-16 The following dyes were evaluated. Method Preparation of stock solution (A): 350 mg of 2- in 7 g of acetone
Phenyl-4,5-bis(p-isopropylphenyl)imidazole dimer was dissolved. Example 13 Coating step (a): 6 mg of dye A (see previous formula) was dissolved in 0.7 g of stock solution (A). This solution contains 1.4 g of 15% by weight in 1:1 acetone:2-methoxyethanol.
Poly(vinyl butyral) (commercially available as BUTVAR B-76 from Monsanto, USA) was added. This solution was then coated onto a primed poly(ethylene terephthalate) film support using a 4 mil doctor blade. Example 14 The above steps using 10 mg of dye B (see previous formula)
Repeat (a). Example 15 The above steps using 9 mg of dye C (see previous formula)
Repeat (a). In this example, several drops of methyl ethyl ketone were added to assist in dissolving the dye. Example 16 The above steps using 12 mg of dye D (see previous formula)
Repeat (a). The resulting element was heated by placing the surface of the support on a 150°C block and the time (in seconds) to bleaching was recorded. Diffuse light density was read before and after thermal bleaching. The results are summarized in the table below. [Table] The following oxidized triarylimidazole dimer was used for testing. In this test, all dimers were tested in hand-applied coatings of triphenylformazane dye contained in a polymeric binder.
The test compound was an oxidized dimer represented by the following formula. In the above formula, R ² and R ³ are each as defined in the table below. All substituents in the formula, except those specifically shown in the table,
It is attached at the para position. Table: Lopil Metal chelates of the formazan compounds were also useful for the aforementioned purposes. Example 32 Bleaching of a complexed formazan dye: 2 mg of cupric acetate hydrate and 6 mg of triphenylformazan were dissolved in 0.4 g of warm 2-methoxyethanol to obtain a dark purple solution. To this solution, add 1.4 g of poly(vinyl butyral) to 1:1 parts by weight of acetone/2-methoxyethanol.
(BUTVAR B-76) and 50% by weight solution in 0.3 g of 1,2-dichloroethane.
mg of oxidized dimer (bisisopropyl-substituted triphenylimidazole oxidized dimer, the above compound)
A solution obtained by dissolving 10B) was added. The resulting solution was coated onto a poly(ethylene terephthalate) film support (with subbing layer) at a wet film thickness of 4 mils. The obtained film had a grayish-purple color. A sample of this film, having a neutral diffuse optical density of 0.36, was heated on a hot metal block at 140°C for 5 seconds. The neutral diffusion concentration of the film after heating was 0.09. Example 33 A coating containing the following materials was prepared using a 2 mil doctor blade. BUTVAR B-76 300 mg/ft ² (Polyvinyl Butyral) Dye 33A (see below) 10 mg/ft ² Bisisopropyl-substituted triphenylimidazole oxidized dimer (see above) 100 mg/ft ² Acetone was used as the solvent. Dye 33A had a structure as represented by the following formula: Apply heat to this coating (160°C for 10 seconds)
As a result, the dye was bleached and its concentration (λ _nax
) changed from 0.360 to 0.105 (after bleaching). In other words, this shows that 71% has changed. Example 34 Although the procedure described in Example 33 above was repeated,
In this example, dye 34B was used in place of dye 33A. Dye 34B can be represented by the following structural formula. Apply heat to this coating (160°C for 10 seconds)
As a result, the dye was bleached and its concentration (λ _nax =
at 540 nm) changed from 0.42 to 0.165 (after bleaching).
That is, the decrease in concentration was 61%. Example 35 Use of Melt Formers: A series of low melting point solids (ie, melt formers) were added to the following compositions. The amount of these melt formers was 100 mg/ft ² (approximately 11 mg/dm ² ). TABLE The resulting composition was coated from an acetone solution onto a poly(ethylene terephthalate) film support to a wet film thickness of 2 mils. Note that the melt former was added to the above composition prior to coating. After drying the coating film, it was heated at a temperature of 130°C for 5 seconds. The results obtained are as follows. [Table] Even when coatings containing methylurea and N-methylbenzamide were treated at a temperature of 120° C. for 15 seconds, it was possible to bleach the pigments mentioned above. Example 36 A coating was prepared by repeating the procedure described in Example 35 above (using the same amounts of each component). However, in this example, BUTVAR B-76 is used instead of LYTRON820.
(Poly(vinyl butyral)) was used. Bleaching of the dye could be achieved when the treatment was carried out on a hot block applying the times and temperatures described below. Temperature (°C) Time (sec) 150 3 140 3 130 5 120 10 Examples 37-47 A series of polymers were tested in compositions as described below. [Table] Rifuenylimidazole dimer (above compound 10B)
For each example, the coating was heated for 10 seconds at a temperature of 130°C. The results obtained are as listed in the following table. [Table] [Table] Product name of Ntoto Co., Ltd.)
Examples 48-50 (Comparative Examples) The following dyes (in place of Dye 33A) were tested in compositions similar to those described in Example 33 above. In each case, bleaching of the dye was unsatisfactory. Example 48 (comparative example) Example 49 (comparative example) Example 50 (comparative example)

Claims (1)

[Claims] 1 (i) Hexaarylbiimidazole compound represented by the following formula: (In the above formula, R and R' are each hydrogen or an alkyl group having 1 to 4 carbon atoms) and (ii) formed when the hexaarylbiimidazole compound is heated. A thermally bleachable composition comprising a dye selected from the group consisting of formazan, azo, polymethine and oxanol dyes, which is reactive with the product. 2 (i) Hexaarylbiimidazole compound represented by the following formula: (In the above formula, R and R' are each hydrogen or an alkyl group having 1 to 4 carbon atoms) and (ii) formed when the hexaarylbiimidazole compound is heated. A photographic element comprising a layer comprising a dye selected from the group consisting of formazan, azo, polymethine and oxanol dyes, which is reactive with a product.