|Publication number||US3615482 A|
|Publication date||Oct 26, 1971|
|Filing date||Dec 17, 1969|
|Priority date||Dec 17, 1969|
|Publication number||US 3615482 A, US 3615482A, US-A-3615482, US3615482 A, US3615482A|
|Original Assignee||Itek Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (11), Classifications (11)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent Inventor Appl. No.
Filed Patented Assignee Alvin Cronig Shaker Heights, Ohio Dec. 17, 1969 Oct. 26, 1971 ltek Corporation Lexington, Mass. Continuation-impart of application Ser. No. 757,114, Sept. 3, 1968, now abandoned.
GELABLE PHOTOPROCESSING SOLUTIONS  References Cited UNITED STATES PATENTS 3,238,043 3/1966 Levy 96/63 FOREIGN PATENTS 766,182 8/l970 Canada 96/63 Primary Examiner-Norman G. Torchin Assistant Examiner-Richard E. Fichter Attorneys-Homer 0. Blair, Robert L. Nathans and David E.
Brook ABSTRACT: Gelable photoprocessing solutions are disclosed which comprise a photoprocessing solution and an amount of heat-reversible gel-forming carrageenan or furcellaran sufficient to cause gelation of the solution. These solutions are easily gelled, in which state they are useful in developing. fixing, washing, etc. exposed photographic films.
GELABLE PI'IOTOPROCESSING SOLUTIONS CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. Pat. application to Cronig, Ser.-No. 757,1 [4, which was filed on Sept. 3,
1968, now abandoned.
BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to photographic processing systems and more particularly to gelable and gelled photoprocessing solutions.
2. Prior Art The need for simplified photographic processing systems has become of great interest. The conventional wet processing including developing, rinsing, fixing, washing, and drying has ,proven to be cumbersome in many applications. Additionally,
it is often important to view results quickly, and if possible, to process without the need for involved complicated processing techniques and bulky, expensive equipment. For example, the field of aerial photography demands shorter and shorter access, or dry to dry time, with lessc'omplex hardware and simpler processing systems. I
Because of the many problems encountered in processing photographic film with liquids, many attempts have -been .made to devise improved photoprocessing systems. Some of these include, for example: viscous processing systems (see I photoprocessing solutions has long been recognized. Gelled solutions have the properties of solids and have the advantage of allowing relatively dry processing of film.
Some gelled photoprocessing solutions have been described in the patent literature. In Henn, U.S. Pat. No. 2,784,086, silver halide developer solutions are disclosed which can be gelled using up to 10 percent alginic acid or one of its'salt or ester derivatives. Canadian Pat. No. 766,182, issued Aug. 29, i967 teaches that certain viscous photoprocessing solutions which contain up to 5 percent gum mucilage can be set or gelled upon photographic film by contacting the viscous solution with borate ion. Illustrative of gum mucilages described are guar gum, locust bean gum, cherry gum, slippery elm gum, alginates, linseed gum, flaxseed gum, gum arabic, etc. Apparatus for processing film with gelled solutions is taught in Ross, U.S. Pat. No. 3,090,290 and in Baumbach, U.S. Pat. No. 3,190,205.
Gelled photoprocessing solutions heretofore available, however, have had many problems and disadvantages. One major problem has been the difficulty in obtaining good surface uniformity, which isnecessary to avoid mottling and/or nonuniformities on the processed film. I
Other major disadvantages or problems encountered with prior gelled processing systems are the difficulties in obtaining: sufficient rigidity or break strength combined with good elasticity; resistance to syneresis (weeping); W tackiness or nonadhesiveness.
Additionally, some of the gelled compositions of the prior art are not heat-reversible. Heat-reversibility is desirably to permit repeated extrusion and recycling of the photoprocessing solutions. Heat-reversible gelled solutions can also be stored and shipped as solids and thereafter heated to their melting temperature and applied in the desired shape or configuration for processing.
SUMMARY or THE INVENTION Theinvention comprises gelable photoprocessing solutions which contain an amount of a carrageenan or furcellaran gel former sufficient to gel the solution. Gelation is'tisually accomplished by heating the gelable solutions to a temperature above the gel critical temperature and subsequently cooling the solution to cause gelation of the solution.
One method for processing photosensitive media with the gelable photoprocessing solutions of this invention is as follows. The gelable solution is applied to a photosensitive medium at an elevated temperature and subsequently allowed to cool whereupon gelation occurs. The gelled solution is allowed to remain upon the medium until processing is complete, afterwhich the gelled solution is stripped from the medium.
CHARACTERISTICS OF THE INVENTION Photoprocessing solutions gelled with a carrageenan or furcellaran have many advantages over gelled photoprocessing solutions heretofore known. For example, the gelled solutions of this invention are more easily thermally reversible than those of the prior art. These solutions can be changed from the gelled state to the solution state by moderate heating and the process may be reversed with moderate cooling. In the transition, these compositions go through a sol state.
Furthermore, both the critical temperature to which -a solution must be heated to make it capable of forming a gelled solution on cooling, and the temperature at which the solution sets and at which it is thermally reversible are within the useful range for photoprocessing. Generally, gel critical temperatures for carrageenan or'furcellaran gelable"photoprocessing solutions are in'the range of about 160 to 180 F. and the setting temperatures are in the range of about to F.
,As is apparent, these temperature ranges are excellent for photoprocessing, particularly for rapid development. This is'a yast improvement over heretofore known gelable photoprocessing solutions which gelled at much lower temperatures, sometimes only slightly above their freezing points. The gelable solutions of this invention also set sharplyat their setting temperatures which adds another advantageto their use for photoprocessing. a
Additionally, the present gelled solutions are especially suited for photoprocessing since their surfaces are smooth and they exhibit low syneresis.
On contact with a film surface, the processing reagent is transferred by diffusion. Additionally, diffusion is two way since processing reagents diffuse into the photosensitive medi- .um while spent chemicals simultaneously diffuse out of the photosensitive medium and into the gelled solution.
Also the gelable compositions of the present invention are capable of forming easily strippable surfaces at or below their setting temperatures. An easily strippable surface is one which exhibits low adhesion to the photosensitive medium and which forms a layer having good internal cohesion and therefore can be readily peeled from the photosensitive medium. This feature combined with the heat-reversibility of the gelled solution allows recycling of the photoprocessing solutions until the processing chemistries are spent.
Considerable further advantages are realized with. the present new gelled solutions in that the physical characteristics and properties thereof can be altered with considerable ease by selection of the gel formers or, alternatively, by use of chemical substances to alter their properties. For example, the break strength, elasticity and gelation temperature can be varied over relatively wide ranges to provide any desired balance of physical properties. The carrageenan gels, for exar'nple, can be treated with cations such as ammonium, calciurn or potassiumions to increase the gelation temperature and break strength. Although they are usually not required for gelation, small amounts of such cations often enhance gelation. The elasticity of the gelled solutions can be increased by the addition of other gel formers, e.g., locust bean gum increases the elasticity of carrageenan gels when used in even small amounts. Due to the excellent compatibility of carageenans and furcellarans with many other gel formers and thickener-s, the desirable properties of such other agents can be incorporated into the present new gels.
A distinct advantage of the present gel formers is the high order of compatibility with photoprocessing solutions, particularly those containing high concentrations of solutes, especially inorganic salts, as fixing solutions containing alkali metal thiosulfates and/or thiocyanates. As is known, photoprocessing solutions often contain cations such as ammonium, calcium or potassium. Also, photoprocessing solutions have a wide range of pH values, and a further advantage of this invention is that gelled solutions can be formed over a wide pH range.
Particularly advantageous is the variable viscosity possible with the present gelable solutions which, coupled with moderate and adjustable setting temperatures, permits facile extrusion of the gelable photoprocessing solutions as continuous layers. By contrast, gelable photoprocessing solutions prepared with agar or similar gel formers typically have a combination of properties which make extrusion difficult or impossible. For example, agar photoprocessing gels have: (1) high melt points and low gelling points; (2) low viscosities in the sol state; and (3 are brittle and hard with low elasticity.
The present new gel compositions also have a high stability even when used in the form of very thin films.
In view of the foregoing advantages, the present gelable compositions are more suitable for photoprocessing of exposed photosensitive media than prior art photoprocessing gels. In the said advantages, the carrageenans are more pronounced than the furcellarans, particularly as to overall versatility and ease of handling and forming of the gelled photoprocessing solutions prepared therewith, for which reason, the carrageenan gel formers are particularly preferred.
It is important to recognize that the gelled solutions of the present invention are significantly different from photoprocessing solutions of the prior art variously categorized as viscous, jellylike, rubbery, pastes, gellike etc. The new gelled solutions are true gels which have a rigidity common to solids.
Viscosity is a meaningless term in describing these gelled solutions because the threedimensional network of the gel former is broken down in attempts to measure viscosity. One method of characterizing these gelled solutions is in terms of their break strengths and elasticities. Break strength is measured with a gelometer and is expressed in terms of the grams of force required to break through the surface of a unit area of the gelled solution's surface. Elasticity is the ability of the gelled solution to recover its original shape after deformation in a short time cycle and is customarily expressed as a percentage of the elongation in a plane parallel to the plane of a particular layer.
DESCRIPTION OF THE INVENTION For purposes of this invention:
1. The term photoprocessing solution" is used to mean any solution or dispersion used to process photosensitive media, before or after exposure, such as chemical or physical developers, fixers, stabilizers, washes, stop baths, etc.;
2. The term gelable solution" is used to mean a solution which can be gelled by any treatment, including but not limited to: (l) heating followed by cooling; (2) contacting with certain cations and/or anions; (3) changing the pH; and (4) combinations of these techniques;
3. The term "gelled solution is used to mean a solution in which the gel former has formed a structural network which contains the liquid components of the solutions in a rigid but elastic form.
Heat-reversible carrageenan and furcellaran gel formers of the present invention are natural polysaccharides derived from red seaweeds such as Irish moss. As is known, the carrageenan polysaccharides comprise several fractions of which the lambda and kappa are well characterized; Another fraction, iota, has beenrecently discovered and is less well characterized. Of these fractions, it is believed that lambda forms viscous solutions but does not gel liquids, whereas the kappa and iota fractions form excellent gelled solutions, but do not significantly effect the viscosity of the solutions prior to gelling. By varying the amounts of the respective fractions present, innumerable combinations of gel and viscous properties are possible. The preferred carrageenan fractions are those which contain the kappa and/or iota fraction in predominating amount with some of the lambda fraction so that before setting, the gelable solution has some added viscosity. In such form, the gelable solution can be applied to a surface, e.g. a film, before setting, but because of the viscosity it will tend to assume the geometry of the surface without running off the surface.
In more specificity, carrageenans and furcellarans are polysaccharides composed basically of D-galactose sugar units. Lambda carrageenan is principally composed of D- galactose-Z-sulfate and D-galactose-2,6-disulfate sugar units; kappa carrageenan is principally composed of D-galactose-4- sulfate and 3,6-anhydro-D-galactos sugar units; and iota carrageenan is principally composed of D-galactose-4-sulfate and 3,6-anhydro-D-galactosefZ-sulfate. Furcellaran, on the other hand, contains D-galactose, D-galactose-4-sulfate and 3,6-anhydro-D-galactose as the major sugar units in the polysaccharide. It is obvious that it is preferred to utilize the respective polysaccharides as obtained from natural sources, but to the extent that these products can be prepared in the laboratory by synthesis, the synthetic products should give the same overall results and the invention is intended to embrace the synthetic as well as the natural polysaccharides. For a more detailed discussion of red seaweed polysaccharides, see CoIloid-0-Scope, Volume l2, Nos. 1 & 2 (1966) and Volume 13, No. l (1967) published by Marine Colloids, Inc. 2 Edison Place, Springfield, New Jersey. For a more detailed discussion of carrageenans, see Whistler, Industrial Gums (Polysaccharides and Their Derivatives), Academic Press, New York I959) at pages 83-115.
Carrageenan and furcellaran gel formers are readily available in commercial quantities under a variety of commercial names. The commercial products usually include all fractions of the carrageenans, the relative amounts of each being determined by the seaweed source and/or the manner of commercial processing which can be tailored to produce mixtures of definite proportions of the respective kappa, lambda and iota fractions. Examples of commercially available carrageenans are those products sold, by Marine Colloids under the trademarks Gelcarin HWG" and Gelcarin GM." An example of a commercially available furcellaran is the product sold under the trade name Furcellaran A44" by Burtonite Corporation.
The gelable solutions of this invention contain an amount of gel former sufficient to cause gelation of photoprocessing solutions. Usually, it is desirable to have as low a ratio of gel former weight to solution weight as is possible. Preferably the gel former will comprise less than about 10 percent and more preferably less than about 5 percent by weight of the total photoprocessing solution. Normally, at least I percent gel former is required to obtain a gelled photoprocessing solution having good gel characteristics.
A very low amount of the liquid photoprocessing reagent is used by the gel former in gelation. The reminder is available for use in photoprocessing.
Gelled photoprocessing compositions can be conveniently formed by heating a mixture of the heat-reversible carrageenan or furcellaran gel former with the processing solution at or above a gel critical temperature followed by cooling below the setting temperature. The heat-reversible gel formers apparently will not form the three-dimensional network unless they are heated to a gel critical temperature which depends on the particular gel former. Of course, the photoprocessing solution can be heated to the gel critical temperature and the gel 523! I j A former added, or the two can be mixed at a lower temperature and subsequently heated together to the gel critical temperature. The desired photoprocessing material can be present in the solution before the heating process, or added during or after the heating step, Also, the set gelled solution may comprise only the solvent and gel former, in which case the photoprocessing material can be added to the gelled solvent by imbibing a solution thereof, e.g. by immersing the gelled solvent in a suitable solution, or alternatively, by merely liquefying the gelled solvent and adding the photoprocessing material to the liquid and subsequently resetting the solution by cooling.
The temperature of heating in formulating the gelled solution should be sufficient to effect solution of the gel former in the selected solvent and, further, sufficient to provide the critical temperature required for the particular gel former selected. The gel critical temperature is the temperature at which the gel former effects the change required to obtain the gelled structure upon cooling below the setting temperature, i.e., the formation of the network required for gelation to occur. The critical temperature is usually above the setting temperature of the gel for which reason the determination of the critical temperature for any given composition can be easily accomplished by removing small samples from the heated mixture and cooling the sample. The critical temperature thus is readily determinable by simple experimentation. Usually prolonged heating is preferably avoided to minimize loss of the solvent, most commonly water, in view of which it is preferred to limit the heating temperature to just at or slightly above the critical temperature.
The gelled photoprocessing solutions of this invention customarily have break strengths of from about 30 to about 600 grams and preferably from about 50 to about 150 grams measured with a gelometer having a quarter-inch diameter plunger. The elasticities, measured as a percentage of the elongation that a gelled solution can undergo before it exceeds its elastic limit are usually in the range of from about 1 percent to about 50 percent.
The solvent for the gel formers of this invention is commonly water but can include other solvents, especially those commonly used in photoprocessing, such as the lower alkanols, e.g. methanol and ethanol, which can be mixed with water to form a suitable solvent system. For best results, the gel former is usually admixed with a small volume of the solvent to form a paste which is then added to the main volume of the solvent maintained at the selected temperature.
While the pH of the gelable processing solutions does not appear to be critical, it has been found that the best gelled solutions form when the Ph is between about 4 and about 12.
In the photoprocessing of exposed photographic media, the present new compositions can be utilized in either the gelable or gelled state. Conveniently, the solutions can be brought directly into contact with the photographic medium in the set state or can be applied in the liquid or sol state preferably at a viscosity between about 5002,000 centipoise at 160-1 80 F. For convenience, the gelable compositions can be produced in liquid form by heating the gel former and the selected solvent containing the photoprocessing material by the method described hereinbefore and, before setting, the liquid mixture can be applied to the photographic medium. After application, the solution is cooled by the ambient air or with cooling apparatus causing the solution to become gelled, or set by other techniques, which means that the used gelled solution can be removed from the processed medium by simple stripping.
Gelled photoprocessing solutions can also be applied to photosensitive media by using gel rollers, gel tapes or gel pads.
The gelable solutions can be utilized in a multilayered arrangement on the photosensitive medium to provide different photoprocessing materials in each layer.
As noted above, physical developers and other solutions useful in processing physically developable media can be gelled with carrageenans or furcellarans. Physical developers according to this invention are intended to included those image-forming systems such as described in US. Pat. No. 3,152,903, in British Pat. No. 1,043,250 and British Pat. No. 1,064,725. These image-forming materials include preferably an oxidizing agent and a reducing agent. Such image-forming materials are also often referred to in the art as electroless plating baths. Electrolytic development such as taught in U.S. Pat. No. 3,152,969 can also be used. The oxidizing agent is generally the image-forming component of the image-forming material. Either organic or inorganic oxidizing agents may be employed as the oxidizing component of the image-forming material The oxidizing and reducing agent may be combined in a single processing solution or may also be in separate solutions. Preferred oxidizing agents comprise the reducible metal ions having at least the oxidizing power of cupric ion and include such metal ions as Ag Hg Pb Au Au", Pt Pt Ni Sn Pb Cu and Cu The reducing agent component of the image-forming materials of this invention are inorganic compounds such as the oxalates, formates, and ethylenediaminetetraacetate complexes of metals having variable valence; and organic compounds such as dihydroxybenzenes, aminophenols, and aminoanilines. Also, polyvinylpyrrolidone, hydrazine, and absorbic acid may be used as reducing agents in this invention. Suitable specific reducing compounds include hydroquinone or derivatives thereof, 0- and p-aminophenol, pmethylaminophenol sulfate, p-hydroxyphenyl glycine, oand p-phenylenediamine, l-phenyl-3-pyrazolidone, alkali and alkaline earth metal oxalates and formates.
The invention is further illustrated by the following examples. All parts and percentages are by weight unless otherwise specified.
EXAMPLE 1 A carrageenan gel former (Gelcarin HWG produced by Marine Colloids. lnc.) is employed to form a gelable photoprocessing solution comprising an alkaline developer solution of the following composition:
Antifog 02 (Eastman Kodak) 0.50 g. Sodium Sulfite 75.00 g. Ethylenediaminctetruacetic 2.00 g acid (EDTA) PhenidoneA 1.00 g. Hydroquinone l0.00 g. Sodium Hydroxide 5.00 g. Water to make l.0 liter The pH of the solution is 10.5. About 2.5 percent by weight of the total solution (25 grams per liter) of the carrageenan is used to form the gelable developer solution.
The gel-forming powder is added to the developer solution at room temperature (6585 F.) and then the entire mixture is heated to F. While stirring by hand or preferably with some type of mechanical mixer. The solution is cooled to a temperature between l25-130 F. to form a gelled solution having a high break strength and low syneresis. The gelled developer is heat-reversible with a melting or solution tem perature of l45-l60 F. and a setting temperature of l25l 3 0 F. After extrusion onto a photosensitive member, it forms an easily strippable surface upon cooling.
EXAMPLE 2 The procedure of example 1 is followed except that the car rageenan gel former, Gelcarin HWG, is used to form a gelable monobath solution of the following composition:
Potassium Metabisulfite Sodium Hydroxide to pH Water to 1.0 liter 6.00 g. l0.-t :0.05
EXAMPLE 1 3 A carrageenan gel former (Gelcarin HWG) is used to form a gelable photographic fixing solution of the following composition:
Sodium Thiosulfate 50.00 g. Ammonium Chloride 4.00 g. Potassium Fluoride l.00 g.
Water to 300 milliliters About 2.5 percent by weight of total solution of the carrageenan is used in this gelable fixer solution. The gel-forming powder is added to the fixer solution at room temperature (6585 F.) and then the entire mixture is heated to 195 F. while stirring by hand. or preferably with some type of mechanical mixer. This solution is cooled to a temperature of 160 F. or below to form a gelled fixer having a high break strength, good elasticity, and low syneresis. This gelled fixer is heat reversible with a melting or solution temperature of 180 F. and a setting temperature of 160 F.
EXAMPLE 4 The procedure of example 1 is used except that the gel former, Gelcarin HWG, is used to form a gelable color developer solution of the following composition:
Upon heating and cooling the gelable solution as in example I, there is provided a gelled color developer which has excellent gel characteristics.
EXAMPLE 5 The procedure of example 4 is followed except that a carrageenan gel former, Gelcarin GM (Marine Colloids, Inc.), is
used to form the gelable color developer using 3.0 percent of the total solution weight of the carrageenan. Also the color developer formulation is modified by substituting g. of potassium hydroxide for the 7.5 g. of sodium hydroxide, with no appreciable changes in the characteristics of the gelled solution.
EXAMPLE 6 Gelcarin HWG is used to form a gelled silver nitrate sensitizing solution for use with physical development systems.
A water gel in the form of a pad is prepared using 2.0 percent of the gel former and using the mixing, heating and cooling techniques described in example i. A separate aqueous solution of silver nitrate is prepared and the water gel pads are allowed to soak in the silver nitrate solution until an equilibrium concentration is reached (about 6 hours). The prepared liquid silver nitrate bath is of higher normality than the final desired silver nitrate normality needed in the gel pads to allow for the dilution by the water used to make the gel pads initially. Specifically a 300 ml. volume of gel pad with a final silver nitrate normality of 1.5 is prepared by using a 500 ml. liquid bath of 2.4 N silver nitrate. The gelled silver nitrate pad has excellent gel properties.
EXAMPLE 7 The procedure of example 6 is used except that carrageenan gel former Gelcarin GM is used to form the gelled silver nitrate sensitizer which has properties similar to those of the product of example 6.
EXAMPLE 8 The procedure of example I is followed except that the gelforming carrageenan, Gelcarin HWG, is used to form a gelable photographic film stabilizing solution of the following composition:
Formalin I000 ml. EDTA tetrasodium salt l0.00 g. Water to L0 liter pH l0.0
Upon heating and cooling, there is provided a gelled stabilizer which has excellent gel characteristics.
EXAMPLE 9 The procedure of example l is followed except that a furcellaran gel former, Furcellaran 44-A, produced and sold by the Burtonite Company, is used to form a gelable alkaline developer solution with comparable results before and after gelation to the products of example 1.
EXAMPLE 10 The procedure of example 1 is followed except that a carrageenan gel former, Gelcarin GM, produced by Marine Colloids Inc., is used to form the gelable alkaline developer solution with similar results before and after gelation.
EXAMPLE ll A carrageenan gel former (Gelcarin GM produced by Marine Colloids, Inc.) is employed to form a gelable photoprocessing solution comprising an alkaline developer solution of the following composition:
Phenidone L5 5 Hydroquinone l0.0 g Sodium Sulfite 20.0 g Sodium Metaborate 25.0 g Potassium Bromide l.5 g pH .0
Development Time: 30 sec. 60 sec. Gamma L 2.64 D min. 0.10 0J6 D max. 2.38 2.55
Sensitometric curves plotted for the gel pad development correspond closely to those for liquid development of the same film.
i. EXAMPLE 12 The procedure of example 1 is used except that the carrageenan gel former Gelcarin l-lWG is used to form a gelable physical developer solution of the following composition:
diethylaminoethanethiol hydrochloride (DEAT) l.l g. metol 38.80 g. citric acid 2.84 g. sodium hydroxide to pH 4.5
distilled water to L0 L.
Twenty grams of the gel former is used.
Upon heating and cooling the gelable solution as in example I, there is provided a gelled physical developer which has good break strength and elasticity and low syneresis. When this developer is used in conjunction with the gelled silver nitrate of examples 6 and 7 and the gelled fixer solution of example 3, a complete gelled fixer solution of example 3, a complete gelled photoprocessing system is available for processing physically developable film.
EXAMPLE 13 EXAMPLE l4 This example also contrasts prior art photoprocessing gels with those of this invention.
An agar gel former (produced by Flsher Scientific) is employed instead of the carrageenan to form a gelable photoprocessing solution comprising the alkaline developer solution of example 1. The solution is mixed as in example 1 using a 2.5 percent concentration of agar, heated to 170 F. and then cooled to 95 F. to form a gelled solution. The gelled developer is heat-reversible with a'melting or solution temperature of 176 F. and a setting temperature of 95 F. The heated solution form of the gel has an extremely low viscosity and it is not suited for extrusion onto a photosensitive medium as are the carrageenan and furcellaran gelable solutions. The low viscosity of the agar solution results in poor adhesion between the processing solution and the photosensitive medium. The higher viscosities of the carraggenan and furcellaran solution produce excellent developer-film adhesion qualities. The solid form of the agar photoprocessing gel has a high break strength but the elasticity of the gel is low resulting in a very brittle gel structure. The gel structures of the carrageenan and furcellaran gels do not exhibit such high brittle characteristics and are more elastic than corresponding agar gels.
What is claimed is:
l. A gelable composition comprising:
a. an aqueous photoprocessing solution; and,
b. a heat-reversible gel former selected from carrageenans, furcellarans and combinations of these, said gel former being present in an amount sufiicient to gel said photoprocessing solution.
2. A composition of claim 1 wherein said gel former is present carrageenan. an amount of less than about 5 percent by weight.
3. A composition of claim 2 wherein said gel former comprises a carrageenan.
4. A composition of claim 3 wherein said photoprocessing solution comprises a chemical developer.
5. A compositlon of claim 3 wherein said photoprocessing solution comprising a physical developer.
6. A composition of claim 3 wherein said photoprocessing solution comprises a monobath developer solution.
7. A photoprocess comprising:
a. heating to at least-its gel critical temperature a gelable composition comprising an aqueous photoprocessing solution and an amount of a heat-reversible gel former selected from carrageenans, furcellarans and combinations of these sufi'icient to gel said photoprocessing solution;
b. contacting a photosensitive medium with said heated gelable processing composition;
c. cooling said processing composition to a temperature below its setting temperature to form a gelled processing composition on said photosensitive medium; and
d. removing said gelled processing composition from the photosensitivemedium.
8. A photoprocess of claim 7 wherein said heated gelable processing composition is extruded onto said photosensitive medium.
9. A photoprocess of claim 8 wherein said gelled processing composition is removed from said photosensitive medium by stripping it therefrom.
10. A method of forming a heat-reversible gelled photoprocessing solution comprising:
a. contacting said photoprocessing solution with an amount of a carrageenan or furcellaran gel former sufficient to gel said solution whereby a gelable solution is formed;
b. heating the gelable solution to a temperature at least equal to the gel critical temperature of said gel former; and,
c. subsequently cooling the mixture to a temperature below the setting temperature of said gelable mixture.
11. A method of claim 10 wherein said photoprocessing solution is contacted with a carrageenan gel former.
12. A method of claim 11 wherein the mixture is heated to a temperature of at least about F.
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|U.S. Classification||430/456, 430/477, 430/466, 430/467, 430/404, 430/458, 430/928|
|Cooperative Classification||Y10S430/129, G03C5/261|