Патент USA US3056686код для вставки
ire. is rates 3,056,676 Patented Get. 2, 1952 2. 1 The objects are accomplished by a photographic ?lm comprising an oriented polyacrylonitrile ?lm, preferably 3,056,676 biaxially stretched at least 1.5 times its original dimen sions in each of two mutually perpendicular directions, impregnated with particles of a silver halide (silver bro POLYMERIQ lFlLM AND PRQCESS OF FREE’ARATEGN Robert William Hendricks, Wilmington, Del, assignor to E. I. du Pont de Nernours and Company, Wilmington, lDel., a corporation of Delaware No Drawing. Filed June 23, 1959, f‘ser. No. 822,199 5 Claims. (Cl. 96—8'7) mide, silver iodide or silver chloride) to a depth of at least 1% of the thickness of the polyacrylonitrile ?lm to a maximum depth, the maximum depth being such as to leave at least 50% of the thickness of the oriented poly This invention relates to an improved photographic ?lm. More particularly, it relates to a new strong poly \acrylonitrile ?lm free of impregnated particles. The im portance of the lower limit, 1%, is in providing adequate acrylonitrile photographic ?lm and the process for pre paring it. p‘ Films of acrylonitrile polymers have properties that adhesion between the particles and the base ?lm and to from the ?lm. The upper limit, 50%, is critical in avoid preparation and storage of photographic ?lm. However, free of impregnation. avoid the danger of abrading the photosensitive particles make them particularly desirable for use as photographic 15 ing unreasonable loss in the properties (strength, tough ess, etc.) of the base ?lm, the polyacrylonitrile ?lm, due ?lm bases. Such ?lms, particularly those of the homo to the destruction of the orientation of the ?lm. It should polymer polyacrylonitrile, are notsubstantially affected be understood that if impregnation of particles is per by changes in temperature. They have an equally low formed from both surfaces of the ?lm, then the maximum sensitivity to changes in humidity. The use of acryloni impregnation from each surface is 25% of the thickness trile polymeric ?lm as a photographic ?lm base, there of the ?lm, i.e., 50% of the ?lm’s thickness must be left fore, would eliminate two very bothersome factors in the The process of the invention comprises the steps, in the polyacrylonitrile ?lms heretofore known to the trade sequence, of treating at least one surface of an oriented Processes for eliminating this drawback such as orienta 25 ?lm of an acrylonitrile polymer with an aqueous solution of silver nitrate, preferably a solution containing a con tion of the polyacrylonitrile ?lm have been dif?cult to are much too brittle for use as a photographic ?lm base. centration of 25-50% silver nitrate in water; removing devise. excess silver nitrate solution from the surface of the ?lm; In a recent patent application, US. application Serial exposing the treated surface of the ?lm to at least one No. 739,181 ?led June 2, 1958, by M. F. Bechtold and assigned to the assignee of the present application, a 30 halogen selected from the group consisting of bromine, chlorine and iodine, said halogen in a form selected from successful process for orienting polyacrylonitrile ?lms is the group consisting of halogen acid, halogen salt and presented. The process improves the toughness and free halogen to convert the silver nitrate to silver halide strength of polyacrylonitrile ?lms by orienting the mate particles; and drying the particle~containing ?lm. rial in the usual two directions but in an unusual sequence of steps. Speci?cally, the process comprises dispersing an acrylonitrile polymer in the form of discrete particles having a size less than about 15 microns in a liquid medium comprising water and a solvent metal salt for said polymer dissolved therein, the salt being present in an amount such that the molar ratio of polymer (calcu lated as an equal weight of monomer) to solvent metal salt is at least 0.5 but less than 6, but in an amount in su?icient to form a salt solution which dissolves the poly mer; forming the resulting dispersion into the shape of a ?lm; evaporating water from the ?lm until coalescence occurs; stretching the resulting ?lm containing the salt 35 The base ?lm is preferably a biaxially-oriented ?lm of polyacrylonitrile. However, oriented copolymers of acry ionitrile with alkyl acrylates (methacrylate), alkyl alk acrylates (methylmethacrylate), styrene, butadiene meth acrylonitrile, vinyl stearate, vinyl acetate, vinyl chloride, N-vinyl pyrrolidone, Z-methyl-S-vinyl pyridine, vinyl arine sulfonic acids and salts thereof, etc., wherein acry lonitrile is the major component (at least 75% of the copolymer is acrylonitrile) are also contemplated for ‘use in the present invention. The polymeric material when treated in this invention is usually in the form of a self-supporting ?lm. How ever, it may be in the form of any shaped article. The term “shaped article,” as used herein, is meant to include and water in a gaseous atmosphere to elongate at least one dimension of the ?lm while maintaining the molar ?lms, sheets, ?bers, fabrics, rods, tubes and the like. ratio of polymer to salt in the ?lm within the range of The ?rst step of the process must be critically con at least 0.5 and less than 6 and maintaining the mole 50 trolled to provide the requisite amount of impregnation percent water between about 30 and 80; and thereafter of the silver nitrate solution into the polyacrylonitrile ar washing salt from the resulting stretched ?lm and drying ticle, i.e., impregnation to an extent of at least 1%, but the stretched ?lm while maintaining said ?lm under ten no more than 50% of the article’s thickness. To achieve sion to restrict dimensional change of the ?lm during washing and drying. The “mole percent water” is ex 55 this requires no special pretreatment. Silver nitrate solu tion induces ‘swelling of the polyacrylonitrile article. By pressed as part of the sum of the mole percentages of causing the polymeric material to swell, the silver nitrate water, salt and polymer, the total equaling 100%. The tends to impregnate the polymeric material so that upon solvent metal salts should be sufficiently soluble in water conversion to insoluble silver halide particles the resulting to yield 10% solutions, and preferably at least 30% solu tions. Furthermore, concentrated aqueous solutions of 60 particles are ?rmly adhered to the acrylonitrile polymeric material. However, the extent of impregnation depends the salts must be capable of dissolving the acrylonitrile on many factors. The concentration of silver nitrate in its polymers at some temperature up to the boiling point of solution, the duration of the impregnating treatment, the the salt solution, e.g., from 0°—l75° C. and generally at temperature of the treatment, etc., all have their effect. 25°-90° C. The primary object of the present invention is to pro 65 Determining a suitable combination of conditions to pro vide the required l—50% impregnation is not di?icult for vide a photographic ?lm utilizing an oriented acryloni one skilled in the art after a minimum of experience. trile polymeric ?lm as the base ?lm. Another object is Usually, a treatment time of 10 seconds-2 minutes is a process for preparing such a photographic ?lm in which adequate at a temperature slightly above room tempera the toughness and strength of the base ?lm are not sacri ?ced. A further object is to provide a photographic ?hn 70 ture with the preferred concentrations of silver nitrate from which ?aking or scratching o? of the photographic salt is prevented. Other objects will appear hereinafter. solution to attain the required impregnation. If desired, an organic compound such as dimethylsulfoxide, dimethyl 3,056,676 3 4 formamide, butyrolaotone, dimethylacetamide, N-methyl pyrrolidone and the like may be used along with the silver nitrate solution to increase the rate of swelling of the acrylonitrile polymeric material by providing better wetting of the polymer and, thus, to increase the extent of impregnation. Although treatments involving immersion of the poly machine stretcher. While in the stretcher, the ?lm was placed in a pan to which was added water at 15° C. After about 16 hours of soaking in the cold water, the ?lm was washed for one hour with water at 65° C. and then dried under tension for one hour at 120° C. A sample of the two-way stretched polyacrylonitrile ?lm, 2 mils thick, was immersed in a solution prepared meric material in a bath of silver nitrate are described from equal parts by weight of silver nitrate, water and in the subsequent examples, it should be understood that dimethylsulfoxide for approximately 30 seconds. The other modes are also useful. Brushing, spraying or paint 10 ?lm was next blotted dry with a paper towel and hydro ing of the polymeric material in any manner with the silver nitrate solution may be used successfully to im ( pregnate one or both surfaces of the ?lm. The polyacrylonitrile ?lms impregnated with silver ni~ gen chloride gas was passed over the surface on one side of the ?lm for approximately 30 seconds. The initially clear surface became nearly opaque and white upon this treatment with hydrogen chloride. The ?lm was then trate are ?rst wiped gently to remove eXcess solution from 15 placed under a transparent sample of ?lm which had the the surface and then converted to a photo-sensitive ?lm ' letter “B” inscribed on it in opaque ink, and the resulting by conversion of the silver nitrate to insoluble particles of silver bromide, silver iodide or silver chloride. The ?nal concentration of particles in the polymeric material laminar structure was placed in front of a bank of ?uo rescent sunlamps for approximately one minute with the silver chloride-containing ?lm behind the lettered ?lm. Upon removal from the lamps, the top ?lm was peeled may range anywhere from 0.5% to as high as 65% of the total weight of polymer plus particles without sub stantially altering the physical properties of the polymeric visible (as a semi-transparent white-unreduced portion) material. However, a range of 15—45% of particles in the polymeric material has been found to be most useful. ?lm. off and it was found that the image of the letter was on a black background of reduced silver in the bottom The resulting ?lm was then washed thoroughly in The conversion step may be accomplished by exposing 25 a bath of saturated sodium thiosulfate to remove unre the impregnated ?lm to the vapors of the free halogen duced silver chloride and silver nitrate to “?x” the image. or the halogen acid. The conversion may also be ac The excellent physical properties of the base polyacrylo complished by using an aqueous solution of a soluble nitrile ?lm were virtually unaffected by this treatment. halide such as the alkali metal (sodium or potassium) Example 2 halide or a solution of the halogen acid. This latter treat 30 A sample of the two-way stretched polyacrylonitrile ment with an aqueous solution, surprisingly, does not wash out silver salt from the ?lm. This is probably at ?lm, 2 mils thick, prepared as in Example 1, was im tributable to the unexpected ability of the acrylonitrile mersed in a saturated solution of silver nitrate for ap groups of the polymeric ?lm to hold silver ions within the proximately 30 seconds. The ?lm Was vblotted dry with structure by coordination. 35 a paper towel and a 50/50 weight percent mixture of hydrogen bromide gas and hydrogen iodide gas was passed over the surface on one side of the ?lm for ap The conversion treatments may be performed at room temperature (20° C.) or slightly above. The duration proximately 30 seconds. The initially clear surface be of the treatments should be approximately equal to the duration of the silver nitrate treatment in the previous step, came nearly opaque and pale yellow. The ?lm was then placed under a transparent sample of ?lm which had . i.e., at least 10 seconds and as high as 2 minutes, depend ing upon the thickness of the ?lm being treated. If desired, sensitizers such as allyl diethylthiourea or allylisothiocyanate may be added to the ?lm during or subsequent to the conversion treatment to increase light ' with the silver bromide/silver iodide-containing ?lm be sensitivity. These light sensitizers appear to be capable hind the lettered ?lm. Upon removal from the lamps, the letter “B” inscribed on it in opaque ink, and the re sulting laminar structure was placed in front of a bank of ?uorescent sunlamps for approximately one minute of depositing silver sul?de on the silver halide grains to the top ?lm was peeled off and it was found that the increase the sensitivity of the silver halide grains to the effect of light. image of the letter was visible (as a semi-transparent white-unreduced portion) on a black background of re duced silver in the bottom ?lm. The invention will be more clearly understood by re The resulting ?lm was ferring to the examples which follow, Example 1 repre 50 then Washed thoroughly in a bath of saturated sodium thiosulfate to remove unreduced silver halide and silver senting the best mode contemplated for performing the nitrate to “?x” the image. The excellent physical prop process of the invention. In the examples, all parts are erties of the base polyacrylonitrile ?lm were virtually un by weight unless otherwise speci?ed. affected by the treatment. Example 1 55 Example 3 Samples of two-way stretched polyacrylonitrile ?lm were prepared in the following manner by photopolym A sample of two-way stretched polyacrylonitrile ?lm, erization from the following ingredients: 32.5 mole percent distilled acrylonitrile 15.2 mole percent zinc chloride 52.3 mole percent distilled water Hydrochloric acid and benzoin, each in an amount less than 1% based on the weight of the main ingredients, 2 mils thick, was immersed in a saturated solution of 60 silver nitrate for approximately 30 seconds. The ?lm was blotted dry with a paper towel and placed on a glass plate. A 10% aqueous solution of sodium chlo ride was brushed onto the exposed surface of the poly acrylonitrile ?lm with a cotton swab. The initially clear surface become nearly opaque and white upon this treat was also used in the preparation. 65 ment with sodium chloride. The resulting viscous solution was poured between A photographic image was produced on this ?lm by two thin glass plates spaced 20 mils apart. Ultraviolet light from a bank of ?ve l5-watt ?uorescent sunlamps following the procedure described in Example 2. The ?lm was washed with saturatedv sodium thiosulfate solu tion to “?x” the image and then dried. The ?lm had was radiated upon the solution for about 20 minutes. The plates were separated to leave a salt-containing poly 70 excellent physical properties. acrylonitrile ?lm. The ?lm was stretched in two mutually perpendicular directions at room temperature (23° C.) and 50% rela tive humidity to about 3 times its original dimensions Example 4 A sample of two-way stretched polyacrylonitrile ?lm, 2 mils thick, was immersed in a saturated solution of (200% elongation) using simultaneous stretching in a 75 silver nitrate for approximately 30 seconds. The ?lm 8,056,676 6 5 treating at least one surface of an oriented polyacrylo nitrile ?lm with an aqueous solution of silver nitrate for a time sui?cient to impregnate said ?lm to at least 1%, but not more than 50%, of the thickness of said ?lm with said solution; removing excess silver nitrate solu tion from the surface of said ?lm; treating at least one surface of said ?lm with an aqueous solution containing was blotted dry with a paper towel and a 50/50 weight percent mixture of chlorine and bromine was passed over the surface on one side of the ?lm for approximately 30 seconds. The initially clear surface became nearly opaque and slightly yellow in color. A photographic image was produced on the ?lm by following the procedure described in Example 2. After at least one soluble halide selected from the group con “?xing” the image and drying, the ?lm showed the same sisting of alkali metal bromide, alkali metal iodide, a1 high level of physical properties as the original poly 10 kali metal chloride, hydrogen bromide, hydrogen iodide acrylonitrile base ?lm. and hydrogen chloride to convert said silver nitrate to Having fully disclosed the invention, what is claimed silver halide particles; and drying said particle-containing is: ?lm. 4. A photographic ?lm comprising an oriented poly treating at least one surface of an oriented polyacrylo nitrile ?lm with an aqueous solution of silver nitrate for 15 acrylonitrile ?lm impregnated with 05-65% by weight l. A process comprising the steps, in sequence, of of particles of at least one silver halide selected from a time su?icient to impregnate said ?lm to at least 1%, but not more than 50%, of the thickness of said ?lm with said solution; removing excess silver nitrate solution from the group consisting of silver bromide, silver iodide and silver chloride to a depth of 1—50% of the thickness of said oriented polyacrylonitrile ?lm. the surface of said ?lm; exposing said treated ?lm to at 5. A photographic ?lm as in claim 4 wherein said least one halogen selected from the group consisting of 20 oriented polyacrylonitrile ?lm is biaxially oriented poly bromine, chlorine and iodine, said halogen in a form acrylonitrile ?lm which has been biaxially oriented by selected from the group consisting of halogen acid, halo stretching at least 1.5 times its original dimensions in gen alkali metal salt and free halogen to convert said each of two mutually perpendicular directions. silver nitrate to silver halide particles; and drying said particle-containing ?lm. 25 2. A process comprising the steps, in sequence, of treating at least one surface of an oriented polyacryloni trile ?lm with an aqueous solution of silver nitrate for a time su?icient to impregnate said ?lm to at least 1%, but not ‘more than 50%, of the thickness of said ?lm with 30 said solution; removing excess silver nitrate solution from the surface of said ?lm; exposing said treated ?lm to at least one gas selected from the group consisting of hy drogen bromide, hydrogen iodide, hydrogen chloride, bromine, iodine and chlorine to convert said silver ni 35 trate to silver halide particles; and drying said particle containing ?lm. 3. A process comprising the steps, in sequence, of References Cited in the ?le of this patent UNITED STATES PATENTS 984,886 2,706,728 Brandenberger ________ __ Feb. 21, 1911 Coover et al. ________ __ Apr. 19, 1955 147,451 Japan _______________ __ Dec. 29, 1941 FOREIGN PATENTS OTHER REFERENCES Cyanamid’s Nitrogen Chemical Digest, The Chemistry of Acrylonitrile, pp. 51-56, American Cyanamid Com pany, New York, January 1951.