US3409438A - Photosensitive heat developable copysheet - Google Patents

Description

Nov. 5, 1968 RQJ. LoKKEN 3,409,438

PHOTOSENSITIVE HEAT DEVELOPABLE COPYSHEET Filed Aug. 26, 1963 3 Sheets-Sheet l 4770,? EVS `United States. Patent 3,409,438 f -PHOTOSENSITIVE HEAT DEVELOPABLE f t. COPYSHEET 1 Robert J, Lokken, Maplewood, Minn., assignor to Minne- Sota Mining. and Manufacturing Company, St. Paul, ,e Minn., a corporation of Delaware Filed Aug. 26, 1963, Ser. No. 304,422 19 Claims. (Cl. 96--95) ABSTRACT OF'THE DISCLOSURE A'light-sensitive,copysheet, which `develops an intense silveriirnage by simple lheating after exposure, contains a water-insoluble silver soap ofay fatty acid ltogether with a light-sensitive progenitor of a reducing agent for silver lon.

in whichethe darks and lights of the subject photographed are transposed. Asecond transposal is therefore required in order toV obtain a true reproduction of` the original subject. In traditional photographic processes this involves exposure, through the negativetransparency, of a silver halide print paper which must then be subjected toa wet developing process in order to bring out the desired positive visible image. The present Vinvention provides a dry process printing paper onwhich the positive or transposed image'is obtained by a simplified process involving merely exposure Ito the negative `light-image followed by uniform mild heating of the exposed sheet. l In an alternative procedure thesensitive copysheet is iirst uniformly exposed to actinic radiation to render it visibly sensitive to heat, after whichit is used to provide ay permanent ,visible record of a heat-image impressed thereon, e.g. by means of a heated stylus or heated metal type, or by thermographic copying processes, or in other ways. p Heat-sensitive. copysheets ,having particular utility in the reproduction of graphic originals by thermographic copying processes have previously been known. As described in Owen.U.S. Patent No. 2,910,377, one useful form of heat-sensitive composition contains a silver soap and .a reducing agent. A typical formulation includes silver behenate and a polyhydroxyaromatic reducing agent such as dihydroxybenzoic acid, together with suitable stabilizers, toners, polymericlbinders and other modifiers as desired. These Copysheets are essentially stable toward light and are permanently visibly changed from white to intense blue-black on momentary heating to temperatures in the range .of about 90-150" C. In Grant U.S. Patent No. 3,904,619, the selection of certain specific types of hydroxyaromatic reducing agents permits these heat-sensitive silver soap compositions to be desensitized by exposure to ultraviolet radiation, thereby permitting the forma-- tionV of heat-stable black-on-white copies of black-on-white originals.` The introduction of photoreducible dyes, as describedlin WorkmanU. Patent No. 3,094,417, permits the same vresults -to. be attained on exposure to visible light. I

The preparation of positive or black-on-white copies bytransposal from negative or white-on-black transparency originals in accordance with the present invention likewise involves the reduction of a silver salt to yield the silver image. However, unlike those of' prior art copysheets, the sensitiv'e coating initially contains no reducing 3,409,438 Patented Nov. 5, 1968 agent for the silver ion, or at most contains no reducing agent operable by itself at the temperature and within the time employed to cause reduction of the silver ion. Instead it contains a photosensitive silver reductant progenitor, i.e., a material which on irradiation undergoes a photochemical reaction with generation of a reducing agent for silver ion. The coated sheet accordingly is heat-resistant as initially produced, but is rendered heat-sensitive by exposure to actinic radiation, particularly to radiation in the near-ultraviolet range of wavelengths. v

After exposure to a light-image and development of the visible image by heating, many of the Copysheets of this invention may be exposed to normal room light for prolonged periods without visible change and without becoming heat-sensitive at unprinted background areas. Exposure to more intense radiation, particularly in the nearultraviolet range, sensitizes these areas so that additional images may be formed by appropriate application of heat. In some instances the sheet may be desensitized by heating, eg., by the removal of unused portions of the photosensitive silver reductant progenitor either by decomposition or by volatilzation, thus stabilizing the background areas against further sensitization. and reaction. Copy prepared with these preferred Copysheets is therefore stable against both actinic radiation and heat.

The copysheet may be illustratively represented by the following symbolic cross-sectional diagram:

Paper-like backing Silver behenate is a preferred silver salt and its preparation in the form of an intimate blend of equal molar proportions of coprecipitated salt and behenic acid has been decribed, e.g., in the Owen patent. The salt may be prepared essentially free of the acid by proper proportioning of the reactants, and in this form is found to produce.y a somewhat more intense image in the copysheet; on the other hand, the presence of the added acid improves the water-resistance of the coating. Normally solid silver salts of other fatty acids, and particularly of the higher fatty acids, are also useful; silver stearate is a good example. Other fatty acids, e.g., stearic acid, and other waterresistant or waxy materials may analogously replace the behenic acid. However these components are not essential and may be omitted. Other normally solid silver salts may be used, as well as salts of other noble metals, for example gold stearate; but the silver soaps of long chain fatty acids are easily prepared, conveniently handled, relatively inexpensive, impart a high order of stability, and are preferred. In particular the silver soaps have been found to be stable against exposure to light, so that they may be prepared and processed under normal illumination.

With the silver salts it is desirable to use images toning materials so that maximum image density and color contrast may be attained. Phthalic anhydride is one such material; another and much preferred toner is phthalazinone. However a visible image may be obtained in the absence of these or analogous additives,

Polyhydroxyaromatic compounds, such for example as dihydroxybenzoic acid, methyl gallate, catechol, or 2,3- naphthalenediol, are known to be effective reducing agents for silver ion in heat-sensitive copysheet structures, cf.

the Owen patent. The structure of certain photosensitive aromatic diazo compounds is such as to make their conversion to analogous polyhydroxy compounds, by hydrolytic photodecomposition, appear feasible. It has now been found that many such diazo compounds are indeed effective as photosensitive progenitors of reductants for silver ion",l whilen remaining unreactive with the intheabsenceof actinic radiationr Other materials which have been found useful to at least a limited extent as photosensitive progenitors of reductants for-silver ion'include certain Aunsaturated carbonyl compounds, quinones, aryl esters ofl carboxylic acids,-and styryl dye bases-In all instances the compound has anunsaturated aliphatic or ^cycloaliphatic) structure, preferably containingl at least Ione conjugate double bond system, or an aromatic ring havingat least onesubstituent group with one or more double bonds'o'r other unsaturation, and is absorptiveV of, and altered by, =ac`tinic radiationin the ultraviolet or visible region of the spectrum. At the same time, many closely similar compounds are found-to be completely ineffective as reductant progenitors," or'to vbe effective to such 'a limited extent that copysheetsprepared therewith are `not practical; Itfhas therefore =been foundimpossible fully'to define' theuseful classes of reactantsby chemical structure. However,

silver salt ithas been found possible-todistinguish the commercially useful=materials from the inoperable or impractical prod@ ucts by means' vof a simplel test'iprocedure involving'the irradiation of a dilute solution containing reactable quantities of both the proposed reagent and silver nitrate.

More specifically, a preferred test procedure involves dissolving about one-tenth gram of the proposed progenitor material in ten grams of a mixture of equal weights of ethanol and water, adding thereto about three grams of a saturated solution of silver nitrate in 95% ethanol', adjusting the acidity of theA mixture to pH 5 to 6 by means of dilute nitric acid or ammonium hydroxideas required, and irradiating a two ml. portion in a Pyrex test tube for three minutes with the radiation from a B-H 6 high pressure mercury arc lamp at a distance of nine inches. In the event a precipitate forms during addition of the silver nitrate solution, it is removed by filtration and sufcient additional silver nitrate is added to insure the presence of unreacted silver nitrate prior to irradiation. Formation of a black silver precipitate in the solution or of a silver mirror on the glassv tube, either during irradiation or after heatingthe irradiated solution for onehalf hour'at 60 C., indicates the compound tested to be an'effective silver reductant progenitor. A control sample of the silver nitrate solution is similarly irradiated, heated, and examined; any change in the test sample must be appreciably greater than any appearing in the control sample inorder to indicate an effective reactant. The test as just described has provided strong positive results, in the `form of an unmistakable silver precipitate or mirror deposit, `with all reductant progenitor com,-` pounds which have been found to produce commercially acceptable intense images in copysheets prepared from such 'compounds in conjunction with silver behenate. Compounds which are less effective in the copysheet, producing faint or low-density images under optimum exposure to light and heat, may or may not give positive results in the solution test. A few compounds which are not visibly reactive under test conditions have produced faint or inadequate images when tested in copysheet formulations, although in most instances such compounds are entirelyv ineffective in the copysheet. In at least one specritic instance, a compound giving positive test results has produced no visible image in the sheet form; the sheet product therefore failing to meet the requirements for the copysheets of this invention, namely the ability :to be made visibly heat-sensitive by exposure to actinic radiatin. l v

The preparation of the dry process printing sheet ordinai'ily involves the application of4 one or more coatings of the silver salt and reducing-agent progenitor to a thin paper or film substrate or backing. Various binder materials are employed to retain the reactants in position and condition for reaction on the surface of the substrate. In larger proportions, a film-forming polymeric binder may itself serve as the carrier film; or the reactants may backing, in the sub- "stantial absencev ofbinderfTransparent paper oi"A filr backings permit the copy td'be seen from either surface and are particularly useful in reflex copying procedures and for making copies ,which are to be used as projection transparencies; .but opaque backings such as heavy paper or metal foil are also useful, providing the materzia'lA4 vused ,is;adequately resistant to vthetemperatures requiredV in *ther developrnelratof the lvisible imageffhe silver salt and reducing agentI progenitor may' if'desired be applied to'separate'subst'rates'j exposure of the progenitor coating to 'a suitable lightlimage, and heating the thus exposed sheet withthe coated'surface in contact with the silver-coated surface, then produces a.visible reproduction of`the exposed image areas on the latter. For this'niodification'the reductantshould be volatilizable and adequately stable so that it'may be transferred in reactive condition "to the silver-containing receptor sheet. Various other combinations and modifications are possible, as will be further indicated hereinafter.

The practice of the inventionwill now be further illustrated in terms of specific but nonlimiting examples, in which 'all proportions are givenin parts by weight unless otherwise noted. In many of these examples there will be `employed certain preferred coating compositions and coated sheet materials now to be described'. Y

. COMPOSITION I Parts Equimolar blend of silver behenate and behenic '.acid f f f 2.88 Zinc oxide 11.5 Powdered terpene resin (Piccolyte S-l35) 2.30 Silver image toner (phthalazinone) 1.15 Stabilizer (tetrachlorophthalic anhydride) 1 0.05 Polyvinyl acetate 1.75 Cellulose-acetate 2.88 Volatile vehicle (acetone) 1 77.5

The composition is applied to a heavy white-.paper backing with a coating knife or bar Aat an orifice of 3 mils to provide, after removal ofk volatile vehicle, a smooth uniform white coating weighing 1.2y grams per square foot, the coated sheet being here identified :as Sheet'I. Another composition is producedy by adding, to the formulation of Composition I, 0.5 part of a light-stable tertiary-alkyl phenol mild reducing agent, more specifically 2,6-ditertiarybutyl 4-methylphenol, also known, as Ionolf The. modified mixture is identified as Composition II and the corresponding coated sheet material as Sheet II. Where SheetI remains white under prolonged exposure to moderately elevated temperatures of the order of C., Sheet II-under the same conditions will be found to darken slowly, becoming a dull brownish gray after several hours at that temperature or more rapidly at higher temperatures. However the reaction is not suffi'ciently rapid and the amount ofthe mild-reductant is not sufficiently large to permit the copying of graphic originals on papers such as Sheet II on any practical basis by the thermographic process using commercially avail able thermographic copying machines.` f l Example l A lirst 'mixture consists of 48l parts of the equimolar blend ofpsilver behenate and behenic acid dispersedfin very smallv particles by prolonged ball milling in a solution of .'12 parts of polystyrene (Dow 700)y in a mixture of 152 parts of toluene, .102 parts of acetone and 84 parts of commercial heptane. To ten parts of the mixture thus prepared is added a solution of 0.25 part of phthalazinone in two parts of dioxane. The resulting composition is appliedat a coating bar spacing of three mils to mapY overlay tracing paper, and the sheet is dried. v f

`A second mixture is prepared by mixing together 0.2 part of Apotassium o-hydroxybenzenediazosulfonate, 0.2 part'of sodium-1,3,6-naphthalenetrisulfonate, 0.2 part of glycerine, 0.4 part of Ikethyl cellulose, six, parts .of acetone and one of water.y yThe second and third Vnamed ingredientsva're,optional and Vmay be omitted. The composition is coated at an orifice of three milsfoverfthe previous-coat, nd. dried, .these operations, being conducted under subdued light. l f lTghe. coated shee'tgis white in color. Itfis .covered with a photographic negative transparency placedpin. contact with the coated` surface andisexposed toylight from. a B-H 6 high pressure mercury ar'c-'ultravioletlamp for ten seconds Iat adistance'of `eight inches. The exposed sheet remains visibly unchanged. It is then` heated 'for' one minute at 100 C. A visible .transposed imageis produced, having dense black image areas. corresponding tothe transparent portions of the negative, and a somewhat yellowish ap.- pearance at the remaining background areas,` y j ,Thetsameleompositiong applied; tojtransparent Mylar film butin reverse order, producearODySheet :which when irradiated t.through the'transparent `film and heated as described results ina transposed copy shoywingsifgnificantly less discoloration at background areas Example 2 To the mixture identified as Composition Ithere is added 0.20 part of p-diethylaminobenzerlediazonium hexauorophosphate'. The composition is,v coated on white paper and dried. The sheet is exposed throughi'a transparency to light at 4about-8400 foot-candles as obtained from a light-box ftted'with a number oftungsten'filament lamps, exposure being for seconds. The exposed sheet is then heated for eight secondsv at 120 C. A sharp dense transposed copy of the transparency isobtained.'

*-Equallyeffective'results are obtained Vby substituting p-diethylaminobenzenediazonium tetrauoroborate as lthe reductant progenitor. n Y V E A The singleucoating is most conveniently applied` but suitable precautions must lbey taken to avoid exposure to light. Applicationv of .thereductant progenitorin a1 separate layer, as in Example 1, requires an additional process step but the silver coating may be compounded and applied in the light. An effective procedure involves the application of the diazoniur'n fluophosphate or' fluoborate from'solu'tion fby lightly uniformly swabbing the solution over the' surface of the coating'of Sheet I' hereinbefore described.' 1A utypical solution for Ithisk purpose contains one p art of the diazonium compound in five parts of ethanolA and 94 parts of water.

" Example '3 ,Mylarlpolyester film is coated ata 3 mil orifice with acomposition consisting-of two -parts of methyl cellulose,- 60 parts of methanol, 40 parts of water, and 1.25 parts of potassium o-.hydroxybenzenediazosulfonate. The dry coating isexposed througha transparency to light at about 10,000 foot-candles from incandescent tungsten filament lamps for 15 seconds. The exposed film is then placed in face-to-fa'ce contact with a portion of Sheet II- as hereinbefore. describedv andthe composite is heated between glass plates forabout six seconds at 120 C. to provide on the 1Sheet II a transposed copy of the imaged transparency'The copyis removed Yand replaced with a second portion of Sheet'II, and a second copy is producedby againfheatingthe composite. A total of four copies is made, the time of `heating beingv increased for each successive' copy sufficiently to provide a corresponding image density in each instance andup to a final time of about 1'3seconds, with reductant.

The addition to the coating composition vof 0.1 part oferythrosin produces apink-colored coated film which when similarly exposed through the transparency and heated against a succession of portions of Sheet IIis found! to yield aA total of six copies before the reductant is'e'xhausted, indicating that the presence of the photoreducibl'e dye initiates the conversion of increased amounts ofthe ,diazonium salt to a silverreducing agent..

essentiallyY complete exhaustion of the TUI Similar results are obtained .using benzoquinone as the silver reductant progenitor and hematoporphyrin as the sensitizing photoreducible dye. The presence of the dye reduces the required exposure time and extends the spectral sensitivity toward' the regioriof longer wavelength.

- Example 4 Aportion fof Sheet II isl lfurther coated 'with a 'thin applica-tion of a one-half percentsolutionin methyle'thylketone of vp-diethylaminobenzeuediazoium 'hexafluorof phosphate, asl previously describedin connection with Example 2. VIhe dried sheetisexposed through'a contacting photographic negative transparency to radiation'from'a 'carbon'arc source; e.g., for about one-half minute, and is then heated at 130 C. for 7 seconds' to produce'a trnsposed copy having sharp and intense black image areas on a white background. In'the absence;ofgthediazonium compound the-sheet yields no Vcompa'rableirriage under the exposure and heating conditionsfspecified, even though moderate irregular darkeningoccurs on-"`ex`tended lieating', e.g., in"one"minute-at 130 C. Q l Example A one percent solution of thymoquinone in acetone is applied to aI portion of Sheet I by means of a cotton swab. The sheet is dried, exposed to a light-image, and heated briefly at C. to provide a transposed copy. Further heating at 100 C. removes the unreacted thymoquinone to stabilize the background areas against changes caused by further light-exposure without affecting the.darkened vimage areas. Replacing the thymoquinone with 1,9-bis(2 furyl)-1,3,6,8nonatetraene5-one is equally effective. The compound phenanthrene quinone is similarly useful but a somewhat higher temperature of C. is required. With 4,4-bisdimethylaminobenzophenone a temperature of C. is desirable. These silver reductant progenitor compounds are volatile at the'temperatures indicated.

Example 6 A portion of Sheet II is lightly coated with a solution of l0 parts of phenyl chloroacetate and 15v-parts of a copolymer of vinyl acetate and vinyl chloride (Vinylite VYHH) in parts of acetone and 135 parts of toluene. The dried sheet is exposed through a negative for onehalf minute to radiation from an AH-4 ultraviolet lamp. A 'positive print having dense black image areas is obtained on the coated sheet. During the exposure the temperature of the sheetdoes not exceed approximately 35- 40 C. The images are not intensified by subsequent heat ing at higher temperatures. Where phenyl chloroacetate produces strong intense images, those produced by phenyl acetate are of medium intensity and by o-tolyl acetate are weak and indistinct. No image is produced on portions of the sheet coated with ethyl chloroacetate.

. xaniple 7 A dilute solution of l,9-bis(2furyl)-1,3,6,8nonatetra ene-5-one in acetone is swabbed lightly and uniformly over the coated surface of a portion of Sheet I and dried. The yellowish coating is exposed through a transparency for l0 seconds to radiation from a B-H 6 lamp. The light image reaches the coating directly over one area, andl at another area through a Corning CS 3-70 filter which limits the incident radiation to wavelengths greater than 4660 Angstroms.v Brief heating of the sample produces a visible transposed image at the directly irradiated area but no visible change at `the area irradiated through the filter.

The experiment is repeated but with the addition to the silver reductant progenitor Vsolution of small amounts of each of the dyes eosin, and Setoavine T. The dried' sheet has the color of burnt umber. The directly irradiated area produces a strong transposed image; the area irradiated through the filter yields va less-dense but fully visible transposed image.

7 Example 8 Mylar transparent polyester film is coated on one surface with a thin uniform layer of a mixture of 0.2 part of 4-meth0xy-1-naphthol, 0.088 part of erythrosin, and l parts of ethyl cellulose, to provide a reddish lighttransmissive sensitized intermediate film member as described in Workman U.S. Patent No. 3,094,417. The uncoated surface of the film is then coated with a mixture of benzoquinone and hematoporphyrin as described under Example 3. The doubly coated film is placed with the first coating in contact with a photographic negative backed up with a sheet of white light-reflective paper. Light at 8400 foot-candles from the light-box of Example 2 is directed through the film at the negative original for about one-half minute. The exposed film is then sandwiched between two. portions of Sheet II and the composite is briefly heated in the range of about U-130 .C. by passing under moderate pressure around a heated roller. A copy of the transparency having the same light and dark areas is obtained on the sheet adjacent the first coating; a transposed copy is obtained on the sheet adjacent the second coating. The moderate darkening obtained at background areas of the transposed copy is eliminated by exposing through the negative rather than in the reflex position as described.

Example 9 v"A transparent silver soap coating is provided on transparent Mylar polyester film using a composition containing 12 parts of silver behenate, '12 parts of polyethyl rnethacrylate, 1.8 parts of phthalazinone, 1.8 parts of 2,6-ditertiarybutyl-4-methylphenol, and 0.06 part of tetrachlorophthalic anhydride, applied in 44 parts of toluene and 132 parts of methylethylketone. The dry coating weighs 0.7 gram/sq. ft. Clarity is improved and the sheet is rendered light-sensitive by application of a further coating of 0.15 gram/sq. ft. of a mixture of 0.2 part of p-diethylaminobenzenediazonium tetraliuoroborate and 5 parts of cellulose acetate propionate applied as a 5% solution in methylethylketone. The sheet is exposed from the film side to light from the light-box of Example 2 for seconds through a photographic negative. A portion of Sheet II is then placed in face-to-face contact with the exposed sheet and the composite is heated for seven seconds at 130 C. A transposed or positive copy of the negative original is produced on the Sheet Il and also on the transparent film. In the latter, the areas corresponding to the opaque areas of the negative original remain clear and transparent, so that the product serves as an excellent projection transparency. At the same time the Sheet II positive copy is useful for inspection by the operator while the transparency is in the projector.

A list of photosensitive silver-ion-reductant progenitors which in conjunction with silver soaps have been found to provide light-activated heat-sensitivity in copysheets as herein described is here provided in tabular form, the corresponding structural formulas being indicated in the accompanying drawing.

Name

p-dimethylaminobenzenediazonium tetrafiuoroborate 4-diazo-N,N-diethyl-m-toluidine tetrafluoroborate p-N,N diethylaminobenzene diazonium hexafluorophosphate v r stannous chloridev salt of N-benzyl-N-ethylaniline-p diazonium chloride zinc chloride salt of 2-methyl-4-diethylaminobenzenediazonium chloride zinc chloride salt of N-ethyl-N-betahydroxyethylaniline-p-diazonium chloride zinc chloride salt of 3chloro-4-diethylaminobenzene diazonium chloride 4,4'-bis-dimethylaminobenzophenone 4,4-bis-dimethylaminothiobeniophenone pdimethylaminobenzalacetophenonev 1,9-bis(2-furyl)1,3,6,8-nonatetraene-5-0ne 1,5-bis(p-dimethylaniinobenzal) 3 cinnanial 2,4-

peritanedione p-benzoquinone chloranil thymoquinone acenaphthenequinone phenanthrene quinone 9-methyl-l,9-dihydro-2,6naphthoquinone l-chloroanthraquinone phenyl chloroaceta'te 4-pdimethylaminostyryl quinoline 2-p-dimethylaminostyryl quinoline 4,4'-dihydroxydiphenyltriazene y By way of comparison, the following structurally analogous compounds have been found ineffective as reductant progenitors in copysheets as here defined.

38 2-diazo-l-naphthol-S-sulfonic acid 39 p-nitrobenzenediazonium tetrauoroborate 40 2,4-dinitrobenzenediazonium tetrauoroborate 4l benzenesulfonic acid pdiazonium salt Example l0 It is possible with the sheet materials of this invention to produce a double transposition of image and background, thus for example making possible the preparation of a black-on-white copy from a black-on-white original. One procedure involves making a first transposed copy eg., by the procedure described in Example 1, irradiating the copy to convert the silver reductant progenitor to the red-uctant at the previously unexposed areas, and transferring the reductant to a reactive receptor sheet by the procedure described in Example 3. Another analogous modification will now be set forth in detail.

A portion of Sheet I is first coated lightly with a 2% solution of phenanthrene quinone in acetone. The dried sheet is first exposed through a negative. transparency. For this purpose a photographic plate having transparent image areas on a black background, obtained by photographing a printed original, may be used; or a transparency as provided in Example 9 may be substituted. Exposure is to light from the tungsten filament source Of Example 2 for a period of 20 seconds, i.e., Sufficient to convert essentially all of the quinone to a reductant at the light-struck areas. The sheet is then heated for 10 seconds at C., forming a transposed copy having a brown image on a faint yellow background. The sheet is placed in face-to-face contact with a second portion of Sheet I and the composite is heated for 10 seconds at 130 C. The visibly unchanged second sheet is then exposed to the light source for 20 seconds and heated for 10 seconds at 130 C. to produce a retransposed copy having white images on a brownish background.

What is claimed is as follows:

1. A copysheet product adapted for forming a transposed copy of a graphicvoriginal on exposure to actinic radiation applied in a pattern corresponding to said original 4followed by moderate heating, said copysheet including an initially heat-resistant light-activatable layer comprising a water-insoluble light-stable silver salt and a photosensitive progenitor of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from a normally stable dilute lsolution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches forthree minutes.

2. A copysheet product adapted for forming a transposed copy of a transparency on exposure to actinic radiation applied through said transparency followed by moderate heating, said copysheet comprising a backing and an initially heat-resistant light-activatable layer Acomprising a water-insoluble light-stable silver salt anda photosensitive diazo progenitor of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes.

3. A copysheet product adapted for forming a transposed copy of a transparency on exposure to actinic radiation applied through said transparency followed by moderate heating, said copysheet comprising a visibly opaque paper-like backing having an initially heat-resistant lightactivatable layer comprising a Water-insoluble light-stable silver salt and a photosensitive diazo progenitor of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes.

4. A copysheet product adapted for forming a transposed copy of a transparency on exposure to actinic radiation applied through said transparency followed by moderate heating, said copysheet comprising a transparent backing having a transparent initially heat-resistant lightactivatable layer comprising a water-insoluble light-stable silver salt and a photosensitive diazo progenitor of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes.

5. A copysheet product comprising a backing and an initially heat-resistant light-activatable layer comprising `a water-insoluble light-stable blend of a silver soap and a fatty acid, a toner for the silver image, and a photosensitive progenitor of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on eX- posure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes and said layer including a light-stable tertiary alkykl phenol mild reducing agent for silver in an amount suicient to cause slow partial reduction of said silver soap with moderate darkening of said sheet at moderately elevated temperature.

6. A copysheet product comprising a transparent backing and a transparent initially heat-resistant light-activateble layer comprising finely divided water-insoluble silver soap of long-chain fatty acid, a toner for the silver image, and a photosensitive progenitor of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from .a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes.

7. A copysheet comprising a backing and an initially heat-resistant light-activatable layer comprising a lmforming polymeric binder, a `water-insoluble silver soap of a long-chain fatty acid, a toner for the silver image, and

'LUI

' pound is a dialkylaminobenzenediazonium`tetraliuproborate. y p, l

10. A'copysheet comprising a backing having an initi ly heat-'resistant light-activatable layer comprising arwat'e'rinsoluble light-stable silver salt, a photoseri'is'itiveprdg tor of a silver reducing agent, said progenitor,beingchar-I acterized( as causing the precipitation of silver"from4 andi"- mally stable dilute solution 'containing reactablequntities of `said i progenitor and silver' ion` onpexposu're-o'f 'said solution to radiation froma B-H 6 lamp ata' distance 9 inches for three minutes,l and a photoreducible'dye."

11. The copysheet of claim 1 wherein the progenitor is v-olatilizable from said coating at about 10U-150 C.

12. A photosensitive transfer sheet capable after being exposed to actinic radiation of causing the reduction of water-insoluble silver soap on heating incontact therewith and comprising a backing and a reactant layer including as the sole chemically reactive component a photosensitive progenitor of a volatilizable silver reducing agent, said progenitor being characterized as causing the precipitation of silver from .a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes.

13. The transfer sheet of claim 12 in which the photosensitive silver reductant progenitor is a diazo compound.

14. The transfer sheet of claim 13 in which the photosensitive silver reductant progenitor is an alkali metal hydr-oxybenzenediazosulfonate.

15. The transfer sheet of claim 13 in which the photosensitive silver reductant progenitor is a dialkylaminobenzenediazonium salt.

16. The method of making a transposed print of a graphic original comprising exposing to a diiferential pattern of actinic radiation corresponding to Said yoriginal a sheet material having a photosensitive layer including a photosensitive progenitor of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from a normally stable dilute solution oontaining reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes, and then heating said layer while in inter-reactive association with a corresponding layer of a water-insoluble lightstable silver salt and a silver image toner.

17. The method of making a transposed print of a transparency comprising exposing to actinic radiation through said transparency a copysheet having an initially heat-resistant light-activatable layer including a waterinsoluble light-stable silver salt, a silver image toner, and -a photosensitive progenitor of a silver reducing agent, and heating said sheet to render visibly distinct the light-struck areas thereof; said progenitor being characterized as causing the precipitation of silver from a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes.

18. The method of making a transposed print of a transparency comprising exposing to .actinic radiation in a pattern determined by said transparency a transfer sheet having a surface layer including a photosensitive progenitor 'of a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from a normally stable dilute solution containing reactable quantities of said progenitor and silver ion on exposure of said solution to radiation from a B-H 6 lamp at a distance of 9 inches for three minutes, placing the thus exposed transfer sheetv in face-to-face contactwith a print sheet having a surface layer including a Water-insoluble lightlstable silver salt and a silver image toner, and heatingthe composite "to an extent sufficient to cause formation of silver irnge'on'said, print sheet at areas corresponding to the irradiated areas of said transfer sheet.

.19. The method comprising' exposing to a differential pattern of actinic radiation afsheet material including an initially heat-resistant light-activatable layer comprising a Water-,insoluble light-stable silver salt and pliotosensitive progenitorof a silver reducing agent, said progenitor being characterized as causing the precipitation of silver from `a n0rrnal`ly` stable dilute solution Containing reacg'table quantities of, said progenitor and silver ion on exposure of saidsoltition to radiation fromfa B-H 6,1 arnp at adistancefof 9 inches for three minutesiheating sa'id sheet to render visibly distinct the light-struck areas thereof; converting the remaining progenitor to silver reductant by further exposure to actinic radiation and in a pattern corresponding to the initially unreacted areas; and reacting said reductant in said pattern with a silver salt layer of a copysheet byheating in ,contact therewith.

References Cited UNITED STATES PATENTS 1/1937 Poser et al. 96-49 2,067,690 1/1937 Alink et a1. 96-49 2,183,447 12/1939 `nippel et a1. 96-49 3,094,619 6/1963 Grant 117-368 3,107,174 10/1963 Wartman 117-368 15 3,218,166 11/1965 Reiner 117-368 NORMAN G. TORCHIN, Primary Examiner.

E. FIGHTER, Assistant Examiner.

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