Photosensitive cuprous halide materials and methods for their preparation

Abstract: Photosensitive cuprous halide-type materials, particularly cuprous chloride and cuprous bromide materials, can be prepared from an anode product material produced from electrolysis of copper in an aqueous acid halide bath. Preferably, the copper electrolysis is carried out in a dilute hydrochloric acid solution. The resulting anode product materials are particularly sensitive in the presence of a polar molecule catalyst such as water or ammonia. In one highly preferred embodiment of this invention the anode product material is treated with the aqueous solution of ammonium salt of a water soluble organic acid (e.g. aqueous solution of ammonium ascorbate); one of the chief advantages of these materials is that they are highly photosensitive when dry and can be developed from a latent image prepared thereon.

Description: This invention relates to the preparation and utilization of photosensitive compositions, materials and articles whose photosensitive component is a cuprous compound which when treated to impart photosensitivity thereto as described herein darkens upon exposure to visible light. Use of such photosensitive cuprous compounds includes a host of applications including: replacement of silver in photographic emulsions; direct printing inks; touch-ups in weak printout areas of tracings; photoresists for use in the manufacture of printed circuits, for example; production of stencil transfers for glass and other carriers; manufacture of blueprints; production of papers for photoduplicators; preparation of copper images; and production of photographic emulsions which can be particularly sensitized for the detection of infrared light radiation; among others. Most prior art photographic methods requiring high sensitivity rely largely on the use of silver halide photographic emulsions. Such silver halide photographic emulsions are generally characterized not only by their high sensitivity, but by their high quality images and speedy reactions; however, these emulsions require a considerable amount of silver for the image production or, in the case of color photographic systems, for the intermediate medium for the formation of color images. Photographic methods based upon the use of silver halides usually do not provide a means for recovery or reuse of the silver component, making these methods rather expensive, especially in recent times which have been characterized by dramatic increases in silver prices. Hence, it would be highly desirable if alternative photographic methods were available wherein the use of silver is minimal or, better still, eliminated, while maintaining, or even improving upon, the image quality produced by silver based photographic methods. To this end, many substitutes for silver based photographic materials have been tried, for it is well known that many other metallic salts are photosensitive. In particular, copper has been the subject of a great deal of research aimed at replacing silver in various photographic systems. However, to date, research in this area has failed to produce copper compounds having photosensitive properties which even marginally approach those of silver. For example, most prior art copper salt systems have generally failed to provide sharp, fog free, continuous tone, stable images. Of all the copper salts which have been investigated, cuprous halide compounds probably have been the subject of the most intense study. Some representative examples of the results of this research include: 1. U.S. Patent No. 4,350,758, which is typical of a number of references, teaches the use of a mixture of silver halide and copper halide (e.g. CuCl) salts to prepare photosensitive emulsions. The copper halide is formed by conventional chemical precipitation methods which do not include the electrolytic deposition of a sensitive copper materials as described in the present invention. 2. U.S. Patent No. 4,427,762 describes a photosensitive copper (I) halide (optionally mixed with silver halide) in a binder which can be exposed and developed with an alkaline developer (e.g. a mixture of an amine and an ascorbic acid derivative). Formation of a copper (II) complex is disclosed. Here again, the cuprous halide is formed by chemical precipitation reactions which do not include copper electrolysis. 3. U.S. Patent No. 4,433,049 teaches utilization of an ascorbic acid halide derivative (similar to that disclosed in U.S. Patent 4,427,762) to reduce cupric ions in a liquid phase to form photosensitive cuprous halides. There is no disclosure of a photosensitive material obtained by electrolysis. 4. U.S. Patent No. 3,671,249 teaches a process for preparing a photosensitive cuprous nitrate composition by reacting cuprous halide (e.g. CuCl) with silver nitrate to provide a mixture of cuprous nitrate and silver halide. The material of the present invention, on the other hand, is produced by electrolysis, and is not a mixture of materials as described in this reference. 5. Kosar, Light-Sensitive Systems: Chemistry and Application of Non-Silver Halide Photographic Processes, J. Wiley and Sons (NY) - 1965, pp. 14-41, teaches the photosensitive nature of CuCl and how this material can be made into photosensitive films through the use of various binders and the like. The use of CuCl obtained by copper electrolysis is not taught or suggested by this reference. US-A-1 602 595 relates to the formation of silver halides from metallic silver. US-A-4 582 579 discloses a method for producing ultrapure cuprous chloride for use in electro optic and integrated optic systems. To obtain an ultrapure product, the powder obtained in a reactor is subjected to a zone refining for purification. The "Gmelins Handbuch der anorganischen Chemie"-reference describes cuprous chloride products. In all of the aforementioned documents, the products obtained do not produce the results obtainable with the present invention; that is, sharp, fog free, continuous tone, stable images in silver-free systems. It is an object of the present invention to provide a novel imaging system based on photosensitive copper compounds. It is a further object of the invention to provide a novel process for the manufacture of photosensitive copper materials. A still further object is to provide a photosensitive copper element which can be sensitized and developed from a latent image placed thereon. These and still further objects are achieved by providing a photosensitive element comprising: a support; said support having coated thereon at least one layer comprising a photosensitive material being the anodic reaction product of a copper electrolysis process in which a copper anode is placed in an aqueous hydro halide acid bath; and means for photosensitizing said layer comprising a polar substance selected from the group water, ammonia, and hydrofluoric acid or comprising an aqueous solution of an ammonium salt of a water soluble organic acid in contact with said layer. More particularly, the present invention relates to a method of producing the above photosensitive element as described above, comprising: collecting the anodic reaction product of a copper containing material produced by the electrolysis of copper in an aqueous hydro halide acid bath; applying said anodic reaction product in a thin coating to a substrate; imaging said coating after photosensitizing the anodic reaction product; developing the image carried by said coating; and fixing the image. The photosensitive material is produced as the anode product of a copper electrolysis process in which a copper anode is placed in an aqueous hydro halide acid bath. When this cuprous halide anode product is in contact with a polar substance such as water, ammonia, or the fumes of hydrofluoric acid, it is highly sensitive to light, and will rapidly change color upon exposure to light of any color in the visible spectrum. The anode product may be coated on a substrate, such as paper, and while in contact with a polar substance, it will remain sensitive to light. When dry, the coating loses its sensitivity, but this can be restored by again contacting the surface of the coating with a polar substance. The sensitized coating paper provides a photosensitive element which can be exposed to a light pattern to produce a latent image, i.e. an image which, if not developed and fixed, will dissipate as the element dries. The cuprous halide anode product can be sensitized and stabilized so that it retains its photosensitivity even when it is dry. In particular, the dried anode product coating can be sensitized and the sensitivity made permanent or the sensitivity of a wet coating can be made permanent by treatment with an aqueous solution of an ammonium salt of a water soluble organic acid such as citric or ascorbic acid and then drying. When thus stabilized, the element can be exposed to a light pattern to produce a permanent latent image which will remain even when the element is dry. The latent image produced on the photosensitive element can be developed to make it visible by placing the element in a bath of developing fluid, such as a solution of citric or tartaric acid and sodium bicarbonate, balanced to an optimum pH. In the development reaction, those image areas which have been exposed to light turn gray to black, depending on the light intensity. Unexposed areas turn from white to various tones of yellow. After removal of the element from the development solution, the image will fade unless it is quickly dried. This can be accomplished by immersing the element in denatured alcohol and drying it in warm air. Alternatively, the image can be fixed by immersing it in a very dilute acid, such as very dilute hydrochloric acid or in very dilute sodium thiosulfate, followed by rinsing in water and drying in denatured alcohol. In its simplest form, the objects of the present invention can be achieved through a process of copper electrolysis employing a pair of electrodes including a copper anode in an aqueous hydro halide acid electrolyte solution or bath, applying a current through the electrodes, and collecting the anode product therefrom. Among the various cuprous halide materials which can be employed in the practice of this invention cuprous chloride and cuprous bromide materials are highly preferred. The resulting anode product alone, when coated on a conventional support and contacted with a polar substance selected from the group water, ammonia or hydrofluoric acid, is highly light sensitive and will produce an excellent image when exposed to light. This is, in and of itself, surprising since the anode product appears to be mainly cuprous halide, and these halides had previously been considered to be not particularly photosensitive alone. Moreover, it has been discovered that even better properties may be achieved by following preferred processes as taught below. Thus, not only is a photosensitive copper material produced but methods for sensitizing the material and making the sensitivity permanent for producing permanent high resolution image from a latent image applied to a photosensitive layer of the material of this invention have been discovered. Hence, the anode product materials produced and treated as disclosed herein can be used in various compositions which may be employed in a wide variety of photoresponsive processes such us those listed above. Furthermore, photographic films or emulsions produced from cuprous halide anode product materials produced and treated as disclosed herein are capable of producing clear, fog free images of black copper based materials on a wide variety of substrates used in the photographic arts; e.g., photographic papers, polyvinyl chloride films and the like. The production of the photosensitive cuprous halide materials of this invention begins with the collection of the anode product of an electrolysis of copper. As is well known, electrolysis can be carried out over a wide range of electrical potentials and currents. For example, a 12 volt, 6 ampere bath system produces a material which is virtually the same as that produced by an otherwise analogous 36 volt, 18 ampere system. The copper source comprises the copper anode used in the electrolysis bath cell system. The halide source preferably is a halide ion source such as that provided by acids capable of producing halide ions. The electrolysis is most preferably carried out in a hydro halide bath system provided by a dilute solution of hydrochloric or hydrobromic acid. The anode product material produced by this electrolysis includes cuprous chloride in the case of a copper electrolysis conducted in a hydrochloric acid bath system, cuprous bromide in the case of a copper electrolysis conducted in a hydrobromic acid bath, and so forth. If desired, the photosensitive anode products of the present invention can be co-prepared from combined halide ion sources such as hydrochloric acid and hydrobromic acid. The anode product material need not be, and preferably will not be "pure" cuprous chloride, "pure" cuprous bromide etc., but rather should be a mixture of cuprous halide and other materials and/or a more complex molecule, having other attributes such as those associated with cuprous oxyhalides. The same is also true of any other cuprous halide products which can be employed, e.g., cuprous chlorobromide, cuprous iodobromide, cuprous chloroiodobromide, etc. anode product materials. For example, a typical cuprous chloride material prepared by the electrolysis of copper is not "pure" cuprous chloride, but rather contains, by weight, 60.18% copper, 33.81% chlorine, 4.88% oxygen, and 1.13% hydrogen. The resulting cuprous chloride anode product material is formed as particles having a maximum dimension which is only about 1/20 of the maximum dimension of cuprous chloride crystals produced by conventional precipitation methods. Accordingly, the maximum dimension of cuprous chloride anode product material as well as other cuprous halide anode product materials produced by an electrolysis of copper in accordance with the present invention typically will have a maximum dimension of about one micron. The cuprous halide anode product materials produced as as described above are photosensitive, i.e., they react to light by changing color in the presence of water, or other polar substances, but are not photosensitive when they are dry. When wet, they turn from pure white to shades of gray, to deep black, in direct relation to light intensity and time of exposure, but as they dry, they revert back to the original white; thus, the anode product materials are unstable. However, it has been found that they can be treated to be stable, as described in detail hereafter. The photosensitive copper anode products of this invention; i.e., cuprous halide materials produced as the anode product of copper electrolysis, have superior photoresponsive qualities compared to those cuprous halides produced by other chemical formulation or precipitation methods. In some respects, such as contrast properties, the photosensitive qualities of the materials of this invention are even superior to those of silver halide systems. For example, they sharply turn from white to gray to black depending on light intensity, while silver chloride, for example, responds in shades of blue and purple under similar conditions. The superior photosensitive qualities of the disclosed copper electrolysis anode product materials over copper halides produced by other chemical methods can be maintained and/or enhanced by certain hereinafter disclosed additional processes (e.g. permanent sensitization and development/fixing of the image) which form other aspects of this invention. As previously indicated, it has been found that the photosensitivity of the anode product materials requires the presence of certain polar materials selected from water, ammonia and hydrofluoric acid. Thus, the anode product material is initially photosensitive when it is manufactured in the electrolysis process, since the electrolyte bath normally includes a polar substance such as water. In use, however, any one or more of the anode product materials is typically spread in a thin layer on a support such as a sheet of paper, a film, or other conventional substrate, and is dried, at which point the anode product material loses its sensitivity to light. Thereafter, the anode product layer can be sensitized to light by contact with any of the aforementioned polar substances, and the layer will respond to light, i.e., will be photosensitive, and will remain so until it dries again. Sensitization by ammonia is most conveniently provided by contact of the cuprous halide anode product materials to ammonium hydroxide fumes at ambient temperatures. Sensitization with water is readily carried out, for example, by contacting in any convenient way, for example, spraying or dipping. Sensitization with hydrofluoric acid is readily carried out by exposure to fumes thereof. An image produced by exposing a layer of anode product material to light in the presence of one of the polar substances particularly described above fades when the polar material dissipates, for when the layer dries, the halide materials revert to their original white color. In accordance with a further feature of the present invention, photographic images produced by light reactions of cuprous halide materials in contact with polar substances such as those described above can be stabilized; i.e., made permanent, by treatment of the halide material before exposure, with aqueous solutions of ammonium salts of water soluble organic acids (e.g., citric, ascorbic acids). In one highly preferred embodiment of this invention, the cuprous halide anode product material is stabilized by contact with an aqueous ammonia ascorbic acid solution, is spread in a thin layer on a support, and then dried. The resulting photosensitive element is both light sensitive and stable, so that it is capable of retaining a developed image or a latent (undeveloped) image indefinitely. Print-out images have been produced which employ the anode product material of this invention along with the sensitizing processes described, through exposure to direct sunlight for less than three seconds. High resolution images have been obtained with maximum contrast images being produced in less than about ten seconds. The resulting images are gray to black on a white background. Another highly desirable attribute of the sensitized cuprous halide anode product material herein is that a latent image can be directly and fully developed by placement of the exposed material in solutions of citric or tartaric acid and sodium bicarbonate which have been balanced to an optimum pH of between about 8.4 and 7.6 and most preferably at a pH of about 8. In the development reaction, the areas exposed to light turn gray to black depending on light intensity. The unexposed areas turn from white to various tones of yellow. The development reaction is fast; complete development, without fog, is obtained in about 15 seconds. However, after removal from the developing solution, the image will fade unless it is quickly dried. This quick drying can be accomplished, for example, by immersing the element in denatured alcohol and then drying in warm (e.g. 52°C/125°F) air. Any yellow tones of the developed image are corrected to pure white-gray-black by immersing in a very dilute acid such as very dilute hydrochloric acid, followed by rinsing in plain water and drying in denatured alcohol. A preferred method for fixing or stabilizing this image is immersing the exposed and developed image in very dilute sodium thiosulfate (e.g. a 5-10%) solution. A particularly preferred photosensitive element is prepared by the unique processes of this invention, and incorporates a support having a photosensitive layer coated thereon, the photosensitive layer comprising the anode product of a copper containing material produced by the electrolysis of copper in an aqueous hydro halide acid bath, the layer being sensitized and stabilized with a sensitizing amount of ammonium ascorbate solution which is applied together with a polyvinyl alcohol binder and dried. This element remains photosensitive indefinitely, and can be exposed to light to prepare a latent image. The latent image is developed by contacting the image with a sodium citrate solution, and this is followed by fixing the image by immersing the element in dilute sodium thiosulfate. The photosensitive element is formed by coating the foregoing materials on any of the conventional supports used by the prior art such as glass, paper, or polyethylene terephthalate, among many others. Although polyvinyl alcohol is a preferred binder, others, well known to those of reasonable skill in the art, can be employed within this invention. For example, the polyvinyl alcohol can be replaced with gum arabic. Ammonium ascorbate is particularly preferred as the sensitizing solution, although ammonium citrate and other water soluble salts of organic acids can also be employed. The invention herein is illustrated by the following specific examples: EXAMPLE I PREPARATION OF CUPROUS HALIDE ANODE PRODUCT Cuprous halide material in an optimum grain size for photographic applications was prepared in this invention by electrolysis. A 5 percent solution of hydrochloric acid was employed with a copper anode and copper cathode. The anode was a copper bar, 0.075 m (3 inches) wide by 0.013 m (1/2 inch) thick. The cell used contained 4 liters of solution and employed a 12 volt direct current source. When the voltage was applied, the current very gradually increased from near zero to 6 to 8 amperes. The period of time to reach maximum current flow was about 30 minutes. A deposit of white cuprous compound began forming on the anode as a result of chlorine ions changing to chlorine atoms and reacting with the metallic copper of the anode. As the deposit on the anode grew, it flaked off, and dropped into a container placed below the anode, and was saved. As the process continued, copper ions formed in the solution and some metallic copper was deposited at the cathode as sponge. This sponge can be made to sink to the bottom of the cell and thereby prevent contamination of the anode product by the addition of about 1 gram of gelatin to the 4 liter electrolyte solution. The product of the anode was preserved and protected from oxidation by adding water of about 3 times its volume and adding HCl to make a 1 percent solution. This was mixed to form a slurry prior to applying to a support and/or applying the sensitizing compositions as described below. EXAMPLE II COMPARATIVE ANALYSIS Comparison of the electrolysis anode product cuprous halide material of Example I with analogous products formed by conventional preciptation methods as represented by reagent grade cuprous chloride (Fisher Chemicals) produced the following results: A) Elemental Analysis - Weight % Element Fisher CuCl Applicant's Material Cu 64.13 60.18 Cl 35.86 33.81 O 4.88 Other 1.13 The Cu/Cl ratio of applicant's material was determined to be 1.780 vs. 1.788 theoretical, i.e., it was copper-poor by about 0.4%. A good portion of the material designated as "Other" was hydrogen; carbon was barely detected. B) Trace Elements - ppm - (atomic flame absorption) Cu Si Mn Fe Na Fisher CuCl major 87 1 15 94 Applicant major 150 2 350 110 C) Thermogravimetric Analysis A thermogravimetric analysis was run on applicant's sample. The sample lost 1.89% of its weight between room temperature and 150°C. and was then stable up to 550°C. when weight loss occurred amounting to 75% by weight by the time 620°C. was reached. An additional 0.2% weight loss occurred when air was introduced. D) Surface Area Nitrogen absorption using the BET technique gave a surface area of 0.57 m²/g (0.57 sq m/g) for the Fisher CuCl, and 4.00 m²/g (4.00 sq m/g) for applicant's material. Micrographs show applicant's material to be thin plates typically a micron or so in maximum dimension. E) X-Ray Powder Diffraction The Fisher CuCl showed 3 lines. Applicant's material had the same three major lines showing it is mostly CuCl, but additional lines also appeared which might be indicative of small amounts of polycrystalline occlusions or other copper species, e.g., oxide, oxychloride, cupric, iron impurities etc. F) IR Spectra - in pressed KBr Wafer Two peaks occur in the Fisher CuCl sample. The Fisher CuCl crystal structure has two types of chlorine bonds: These two peaks also occur in applicant's sample, but many additional peaks appear that could be attributed to additional metal-halogen stretching frequencies, or possibly metal-oxygen. Applicant's materials also appear non-stoichiometric, polyphase and with many different components. EXAMPLE III LIGHT SENSITIZING THE CUPROUS CHLORIDE ANODE PRODUCT WITH AMMONIA To render the cuprous halides highly light sensitive, the following procedure was carried out: Cuprous chloride anode product slurry as formed in EXAMPLE I was applied as a thin coating (about 20 to 30 microns) to a paper surface (unsized 3x5 index cards), dried in warm air (about 52°C/125°F, from a hair dryer) and then exposed to the fumes of 14 percent ammonium hydroxide (ammonia gas) for 5-10 seconds. EXAMPLE IV LIGHT SENSITIZING THE CUPROUS CHLORIDE ANODE PRODUCT WITH AMMONIUM CITRATE A sensitizing solution was prepared by bringing anhydrous citric acid into solution with 14 percent ammonium hydroxide to a pH of approximately 3.5. This was mixed at a ratio of about 1:1 with cuprous chloride anode product slurry formed as in EXAMPLE I and applied as a thin coating (20-30 microns) to a paper surface and quickly dried. The solution was prepared, applied, and drying was carried out in a nitrogen (oxygen-free) atmosphere. EXAMPLE V LIGHT SENSITIZING THE CUPROUS CHLORIDE ANODE PRODUCT WITH AMMONIUM ASCORBATE A sensitizing solution was prepared by bringing ascorbic acid into solution with 7 percent ammonium hydroxide to a pH of 4 to 5.5. This was mixed at a ratio of about 1:1 with cuprous chloride anode product slurry formed as in EXAMPLE I and applied as a thin (20-30µm/20-30 micron) coating to a paper surface and dried. Mixing, application and drying was carried out under nitrogen. EXAMPLE VI LIGHT SENSITIZING THE CUPROUS CHLORIDE ANODE PRODUCT WITH WATER Cuprous chloride anode product slurry formed as in EXAMPLE I was applied as a thin (20-30 micron) coating to a paper surface, quickly dried in warm air using a hair dryer to supply drying air at about 52°C/125°F, light sensitivity was imparted by wetting with water. EXAMPLE VII LIGHT SENSITIZING THE CUPROUS CHLORIDE ANODE PRODUCT WITH HYDROFLUORIC ACID Cuprous chloride anode product slurry formed as in EXAMPLE I is applied as a thin (20-30 µm/20-30 micron) coating to a paper surface, dried in warm air and then exposed to fumes of hydrofluoric acid under a hood. EXAMPLE VIII SENSITIZING RESULTS The sensitized products of Examples IV (ammonium citrate treated) and V (ammonium ascorbate treated) retain light sensitivity permanently. The sensitized products of Examples III (ammonia treated), VI (water treated), VII (hydrofluoric acid treated) retain light sensitivity for 1-2 hours; i.e., until "dry". EXAMPLE IX DEVELOPING AND FIXING THE SENSITIZED CUPROUS CHLORIDE ANODE PRODUCT Samples of the elements produced in Examples III-VI were exposed to light to form a latent image on each element. Sodium citrate was used to develop the latent images. It was prepared by mixing 8 grams of anhydrous citric acid with 24 grams of sodium bicarbonate and bringing into solution with one liter of water. Development of a latent image was complete in less than 30 seconds with good contrast properties. At this point, the images were black with tones of yellow. The images were fixed by immersing in a 2 percent solution of sodium thiosulfate for a few seconds until the yellow tones changed to gray-white. The images were then dried and became stable. Developed images were also fixed by immersing the elements in a very dilute (1%) solution of hydrochloric acid until the yellow tones changed to gray-white and then immersing in denatured alcohol to absorb water and then drying with warm forced air. This also provided stable images in each case. EXAMPLE X An electrolyte solution comprising 4.5 l. of 1 M HBr with 0.6 g. of gelatin/liter, 64 ml. of 98% H₂SO₄ and 8 drops of trinitrobutyl phosphate was prepared. Some of this electrolyte was placed in a large, ca. 2,000 ml, bath along with two copper rod electrodes. These rods were first burnished with #624 grit emory cloth and rinsed with water prior to insertion in the aforementioned bath. A power supply was connected to both copper rods and a small beaker was positioned beneath the anode. All room lights were turned off and the power supply was set at 8 amp and the current then applied. The initial voltage was 3.2 V which slowly rose to 4 V after about 1 hour. White material formed on the anode and flaked off into the beaker positioned below. After about 3 hours the current was turned off, the collecting beaker removed and the solids filtered, washed several times with 0.1N HBr and water to yield 38.6 g. of anode product. This material was transferred to a light resistant bottle and covered with about 36 g. of 0.1N HBr. A sample of this solid was mixed with 10% aqueous polyvinyl alcohol, coated on a white unsized 3x5 index card using a small sponge. The coating was dried, contacted for 5-10 seconds with the fumes of a 20% aqueous NH₄OH solution and then given an image-wise exposure through a contact glass image to bright sunlight for 10 seconds. The latent image was then developed in the following developer: Citric acid (anhydr) 8 gm Sodium Bicarbonate 24 gm Distilled water to 1,000 ml. pH = 8.0 (adjusted) A good, readable image soon appeared (ca. 30 seconds to 1 min.). The image was then fixed in ca. 10% aqueous sodium thiosulfate solution whereupon the yellow background disappeared leaving a black, negative image of the original. EXAMPLE XI Cuprous chloride anode product was prepared according to the method described above in Example I. A small amount of this cuprous chloride anode product (ca. 0.3 g) was mixed in a beaker along with 0.2 g. of aqueous polyvinyl alcohol (ca. 10% 71-30 Elvanol ®, E.I. du Pont de Nemours & Co.). Ammonium ascorbate sensitizer (ascorbic acid added to a 7% NH₄OH solution to achieve pH 4-5) was then added (0.5 g.) to achieve a 50 sensitizer/30 anode product/20 polyvinyl alcohol mixture. This mixture was stirred and then some was coated on a 3x5 white card using a sponge. The coating was dried under hot air and exposed 5 seconds through a test image to a 150 W flood light at ca. 12 inches. The imaged element was then developed 3 min. in 2% trisodium citrate solution. After several seconds, a faint negative image began to appear and by the end of the developing period a high quality black image on a yellow background appeared. This image was then fixed in 2% aqueous sodium thiosulfate for 3 minutes whereupon the yellow background disappeared. The black image after rinsing in water and drying, was of archival quality. In a like manner, coatings were applied to a variety of supports (glass, polyethylene tereththalate ceramics) with equivalent results. When the supports were glass or ceramics, the non-exposed images were completely fixed indicating total removal of the coating. The terms "aqueous solution of ammonium salt of water soluble organic acid" and "aqueous ammonia solution of water soluble organic acid" are used interchangeably herein to mean aqueous solutions containing ammonium ion and organic acid in ionized or unionized form whether formed by dissolving ammonium salts of organic acids or admixing organic acid with aqueous ammonium hydroxide solution or by any other means that would occur to a chemist. These terms include treatment in one step as well as treatment in a succession of steps, e.g., first with aqueous ammonium solution followed by treatment with aqueous organic acid solution.

Claims: A photosensitive element comprising: a support; said support having coated thereon at least one layer comprising a photosensitive material being the anodic reaction product of a copper electrolysis process in which a copper anode is placed in an aqueous hydro halide acid bath; and means for photosensitizing said layer comprising a polar substance selected from the group water, ammonia, and hydrofluoric acid or comprising an aqueous solution of an ammonium salt of a water soluble organic acid in contact with said layer. The element of claim 1, wherein said hydro halide acid is hydrochloric acid. The element of claim 1, wherein said salt is selected from the group consisting of ammonium ascorbate and ammonium citrate. The element of claim 3, wherein said salt is ammonium ascorbate. The element of claim 3, wherein said salt is ammonium citrate. The element of claim 1, wherein said polar substance is water. The element of claim 1, wherein said polar substance is ammonia. The element of claim 1, wherein said anodic reaction product includes means for permanently photosensitizing said layer. The element of claim 1, wherein said means for permanently photosensitizing said layer comprises an aqueous solution of ammonium salt of water soluble organic acid. The element of claims 1 to 9, characterized in that said anodic reaction product has been contacted with an aqueous ammonia solution of a water soluble organic acid to impart photosensitivity thereto. The element of claim 10, wherein said organic acid is ascorbic acid or citric acid. The process of preparing the photosensitive element of claims 1 to 11, comprising: collecting the anodic reaction product of a copper containing material produced by the electrolysis of copper in an aqueous hydro halide acid bath; applying said anodic reaction product in a thin coating to a substrate; imaging said coating after photosensitizing the anodic reaction product; developing the image carried by said coating; and fixing the image. The process of claim 12, wherein said anodic reaction product is photosensitized by contacting the surface of said coating with a polar substance selected from the group water, ammonia, and hydrofluoric acid. The process of claim 12, wherein said anodic reaction product is photosensitized by contacting the product with a sensitizing amount of an aqueous solution of ammonium salt of water soluble organic acid. The process of claim 12, further including producing an aqueous slurry of said anodic reaction product, wherein the step of applying said anodic reaction product includes coating said aqueous slurry on said substrate. The process of claim 15, further including permanently sensitizing said anodic reaction product by adding to said slurry an aqueous solution of ammonium salt of water soluble organic acid prior to applying said coating. The process of claim 15, further including: (a) drying said coating after application to a substrate; and (b) temporarily sensitizing said coating by applying a polar substance selected from the group water, ammonia and hydrofluoric acid to the surface thereof. The process of claim 12, wherein the step of developing includes contacting said coating after imaging with a solution of sodium citrate balanced to a pH of about 8. The process of claim 12, wherein the step of fixing includes contacting said coating after development with a very dilute acid, following by rinsing in water and drying.

Inventors: CALDWELL RAY S, CALDWELL, RAY S.
Applicants: ACTION EXPLORATION SERVICES, ACTION EXPLORATION SERVICES, INC.
Application year: 1988
Main classification: G03C1
IPC codes: C25D9, G03C1