US3851584A - Chemical reproduction systems - Google Patents

Abstract

Methods for chemical reproduction of images are provided comprising distributing iodate crystals in conformance with the image on a master sheet, transferring a portion of the iodate crystals in image configuration to a copy sheet which has been sensitized with reagents capable of reacting with the iodate crystals to form colored complexes, and contacting the latent image so formed on the copy sheet with moisture to develop a colored image on the copy sheet conforming to the latent image.

Description

Iliteel @tates atent Palermiti et al. Dec. 3, 1974 [54] CHEMICAL REPRODUCTION SYSTEMS 3.246.148 4/l966 DeTroeyer et al 101/469 UX 3,386,379 6 1968 G dl h l. 101 469 751 Inventors: Frank M. Palermiti, Pittsford; a

Eugene P. Goldberg, Rochester, OTHER PUBLICATIONS Welcher, F. 1., 6a. Standard Methods of Chemical Analysis, om Ed., Vol. II, Part A, 1963, Van Nostrand [73] Assignees: Xerox Corporation, Rochester, NY. 276 & 277 only i [22] Filed: July 10, 1970 Primary Examiner-David Klein [21] Appl. No.: 54,023 ABSTRACT Methods for chemical reproduction of images are pro- [52] Cl 101/470 101/473 63 vided comprising distributing iodate crystals in confor mance with the image on a master sheet, transferring [51] Int. Cl 341m 5/00 a portion of the iodate crystals in image configuration [58] Field of Search 101/469 to a copy sheet which has been sensitized with tea. gents capable of reacting with the iodate crystals to form colored complexes, and contacting the latent [56] References Cited image so formed on the copy sheet with moisture to UNITED STATES PATENTS develop a colored image on the copy sheet conforml,642,774 9/1927 Grange lOl/DlG. 1 ing to the latent image. 2,254,483 9/1941 Hess et al. l0l/472 X D 2,398,779 4/1946 Dalton et a]. 101/469 UX 2 Clams, N0 Drawings 2,873,668 2/1959 Klimkowski et al. 101/469 CHEMICAL REPRODUCTION SYSTEMS This invention relates to multicopy reproduction systems. More particularly, this invention relates to a chemical reproduction system which gives rise to a chromogenic chemical reaction to yield legible copy.

The ability to conveniently and rapidly make multiple copies has become a sine qua non in all fields of business, education, government and science. Existing methods of producing multiple duplicates of original copy such as xerography, photo-copying, thermal and diazo processes generally require the use of complex and expensive equipment. Less sophisticated duplicating processes, such as spirit or stencil-duplicating are rather messy to operate and usually provide copies with poor image definition. Moreover, these latter processes suffer the additional disadvantage of requiring the preparation and use of a master or stencil which usually can only be conveniently used for one copying run. A significant effort has been expended to simplify existing copying systems and to reduce the cost per copy. It is desirable to have simple copying systems which can be operated by unskilled labor at high speeds with good reliability and copy quality to produce a large number of copies without destruction of the original or master.

Accordingly, it is an object of this invention to provide a simple copying system which meets the requirements set forth hereinabove and overcomes the abovenoted deficiencies.

It is another object to provide a chemical copying system which yields multiple copies adapted to become legible through a chromogenic chemical reaction.

It is still another object to provide a multicopying system based upon the transfer of iodate crystals in image configuration from a master sheet to a copy sheet containing a chromogenic co-reactant whereby the iodate is converted to a complex of intense color.

These as well as other objects are accomplished by the present invention, which provides a method for chemical reproduction of an image comprising the steps of distributing finely divided iodate crystals in conformance with the image on a master sheet, transferring the iodate crystals in image configuration to the surface of a copy sheet, said surface containing a chromogenic coreactant, forming a latent image; and contacting said surface with an aqueous fluid thereby developing color on said copy sheet in conformance with the latent image.

The present invention utilizes the intense color generated upon formation of a chromogenic complex such as the starch/ iodine complex to develop latent images which have been transferred from a master sheet to a copy sheet. Surprisingly, it has been found that iodate crystals or mixtures containing said crystals can be selectively adsorbed in image configuration upon images exhibiting some residual tack. Generally, such images are formed with non-drying inks or with wax or polymer based inks which can be rendered slightly tacky by heating. Because of the stoichiometry of the chromogenic reactions involved, a uniquely high multiplication factor is provided permitting an extremely large number of copies to be obtained from one master sheet. Moreover, because of the leverage obtained by the stoichiometry, very little iodate need be adsorbed or transferred in order to successfully reproduce multiple copres.

PREPARATION OF MASTER SHEET Several convenient methods can be employed to distribute iodate crystals in image configuration with the image sought to be reproduced. It has been found'that non-drying or slightly drying inks exhibit sufficient residual tack to cause iodate crystals to adhere thereto. Also, it has been found that images formed with wax or polymer based inks can exhibit such tack upon slight heating or warming. In one embodiment, an iodate image can be obtained simply by dusting the original to be reproduced with an alkali metal iodate, for example, sodium iodate, potassium iodate, lithium iodate and the like, such as by cascading finely divided iodate crystals over the image surface and thereafter removing the excess iodate from the non-image areas by vibrating the original as by flicking the sheet with the fingers or the like. If desired, a mixture containing an iodate salt and one or more solid chromogenic co-reactants or precursors thereof can be employed in lieu of the iodate salt alone. For example, a binary mixture of sodium iodate and potassium iodate or a ternary mixture such as sodium iodate, potassium iodate and a solid organic acid such as citric acid can be employed. When such mixtures are employed, the components are preferably present in amounts ranging from about 50 percent to about percent in excess of the stoichiometric requirements to insure sufficient'transfer of all components. Most preferably, an iodate salt alone is used. Because of the leverage obtained in the chromogenic reaction, very little iodate need be adhered to the image to provide successful duplication. Alternatively, the iodate crystals can be coated on or impregnated in a ribbon to form a typewriter ribbon and the iodate image produced directly on the master sheet by typing. In either of these embodiments, offset lithographic techniques can be employed to transfer a negative impression to an offset blanket from the original image impression on the master. The offset negative impression can then be employed to produce positive copies on copy sheets brought into pressure contact with the offset blanket.

If it is desired to employ direct lithographic techniques, a master sheet can be prepared containing a negative 'or mirror reverse image of the image to be duplicated. This can be conveniently accomplished by placing a sheet of paper or plastic such as a polycarbonate, polyolefin, vinyl polymer or the like against the iodate coated surface of a suitably prepared carbon-type paper and then typing or writing on the side of the sheet of paper or plastic which is not in contact with the carbon-type paper. Since carbon paper is normally oleaginous, it can be dusted with an iodate salt to prepare a carbon-type paper suitable for use in the present invention. The typing can be carried out with an ordinary ribbon in the typewriter. The pressure of the type as the writing takes place causes a mirror reverse or negative impression image containing the iodate salt to be formed on the surface of the sheet in contact with the carbon paper coated with said iodate salt. This sheet, called the master sheet, can be placed with the iodate reverse image face up on the drum of a-direct process duplicating machine and copies made in the manner hereinafter described.

Alternatively, a back-up sheethaving a waxy or oily surface such as on oil skin or wax paper can be substituted for the iodate coated carbon-type paper. In this embodiment, a mirror reverse or negative impression image is formed on the surface of the sheet in contact with the waxy or oily surface of the back-up sheet. Thereafter, the waxy or oily reverse image can be dusted with an iodate salt to form a reverse iodate image master sheet which can be employed on a direct process duplicating machine.

IODATE IMAGE TRANSFER Once the iodate image is formed, by any of the various embodiments described above, it can be transferred either to an offset blanket, such as a metal roll, and then from the offset blanket directly to copy sheets as in conventional offset lithography or, using the techniques described above to obtain a negative iodate impression, the impression can be transferred directly to copy sheets. In all instances, however, transfer either to the offset blanket or to the copy sheets can be obtained simply by pressure. Generally, a pressure between about 75 and about 150 pounds per linear inch is sufficient. Preferably, pressures of 100 to 125 pounds per linear inch are employed. The master sheet can be,

clamped to a master roll or fed into the nip formed by two abutting rolls in pressure contact, one of said rolls acting as an offset blanket. The offset roll, in turn, can be abutted by a copy roll in pressure contact. Copy paper can be fed into the nip between the offset roll and the copy roll to receive the transferred image.

Because of the stoichiometry of the chromogenic reaction, only a small amount of the iodate salt need be transferred either to the offset blanket or directly to the copy paper to obtain duplication. Consequently, one pass of the master sheet across the offset roll is usually sufficient to transfer enough iodate for several copies to be obtained. The master can be reused in this manner several times. As a result, one dustihg of the master conveniently provides a multiplicity of copies, generally from about 50 to about 100 copies can be obtained in this manner.

SENSITIZATION OF COPY SHEETS In order to foster the chromogenic reaction, the copy sheets are sensitized by treatment with the other coreactants or precursors thereof needed to generate a chromogenic complex. Since all of the reactants are or by proper selection can be solid in nature, the present invention offers a great deal of flexibility with respect to selection of the actual mode of operation.

For example, the starch-iodine complex is usually formed by in situ generation of iodine in the presence of starch. Generally, this is accomplished as follows:

XIg yStarch Complex (II) Since the reactants can all be selected to exist in the solid state, the iodate can be admixed with either or both of the iodide and acid to form the dusting composition as described hereinabove for use in preparation of the master sheet. Thus, for example, the dusting composition can be a mixture of an alkali metal iodate and an alkali metal iodide and/or an organic acid such as citric acid, tartaric acid, gluconic acid, malic acid, oxalic acid, formic acid, lactic acid, gallic acid and the like. Similarly, the typewriter ribbons or carbon-type papers can be prepared from such mixtures. In many instances, use of such mixtures in preparation of master sheets has been found to reduce background deposits.

Precursors of such reactants can similarly be employed. Alkali metal sulfites, for example, can be admixed and transferred with the iodate salt. Upon contact with an acid, the sulfite forms a bisulfite which reacts with the iodate generating iodide as follows:

Thus, depending upon the selection of the components of the dusting composition, the remaining components can be employed in conjunction with starch to sensitize the copy sheets to the reaction. Most conveniently, starch sized paper impregnated with the other co-reactants or precursors thereof can be employed. For example, in a preferred embodiment wherein the image to be developed is formed solely of an iodate salt, a starch sized paper impregnated with an organic acid, such as citric acid, and an inorganic iodide, such as potassium iodide, can be convenientlyemployed. The copy paper can be prepared by immersing starch sized paper in an alcohol, water or alcohol/water solution of citric acid and potassium iodide and thereafter drying the paper.

Similarly, the copy sheets can be sensitized with other chromogenic co-reactants which form colored complexes with iodate salts. For example, gallic acid or a mixture of gallic acid and a water or alcohol soluble manganese salt such as manganous chloride form colored complexes with iodates:

10;, gallic'acid brown complex (IV) 10;, gallic acid MnCl brownish-black complex v Also, poly(vinyl pyrrolidone) (PVP) is a strong complexing agent for iodine and is capable of complexing iodine from inorganic iodine-containing salts such as iodates forming complexes which range in color from light yellow to dark reddish-brown depending on the concentration of iodine in the complex:

10; PVP yellow-reddish-brown complex (Vl) Thus, copy sheets can be conveniently sensitized by impregnation with aqueous and/or alcoholic solution of such chromogenic co-reactants as gallic acid, gallic acid and manganous chloride, PVP or the iodide, acid and starch combination described hereinabove.

For purposes of effective sensitization, the sensitizing solution can contain from about 1 percent by weight up to a saturated solution of the chromogenic coreactants. Generally, in solutions of gallic acid and a manganese salt, the manganese salt is present in amounts ranging from about 0.5 to about 5 percent by weight.

The copy sheets can be sensitized prior to use employing conventional techniques for applying a sensitizing composition as described above to a paper or plastic web such as roller coating, knife coating, spray coating, immersion processes causing impregnation and the like. Alternatively, a continuous process can be employed to apply a surface coating of the sensitizing composition to previously untreated conventional starch sized paper or to unsized paper depending upon the chromogenic reaction involved. A bath can be prepared of an aqueous, alcoholic or alcohol/water solution of the sensitizing component. A series of rolls can be employed to transfer a film of the solution to the starch sized or unsized paper as it passes between one of said rolls and a compression roll. The surface of the paper or plastic which has been wetted with the sensitizing solution can then be brought into pressure contact with an offset blanket or a master roll containing a reverse image as in a conventional rotary duplicating machine. The solvents in the sensitizing solution volatize rapidly permitting the production of a large number of copies and permit rapid drying thereby reducing smearing. Whether the copy sheets are presensitized or are continuously sensitized, it has been found that with respect to reactions involving the starch-iodine complex, better results can be obtained if the copy sheets, once sensitized, are top-coated with a thin layer of starch. Dusting the sensitized copy sheets with starch has been found most convenient.

IMAGE DEVELOPMENT Once a latent image has been formed on the copy sheet by transferring the iodate image of the original image to the sensitized copy paper, a visible image can be readily obtained on the copy sheet by developing the latent image upon contact with moisture conveniently provided as by water, steam and the like. Preferably, an aliphatic alcohol such as methanol, ethanol, isopropanol, tert. -butanol and the like can be admixed with the aqueous fluid to improve the volatility of the developer fluid. The alcohol/water solution can vary between a weight ratio of alcohol/ water of from about 1:10 to about :1.

If desired, the sensitization of the copy sheets can be omitted and sensitization and development can, instead, be conducted simultaneously. For example, with respect to the starch-iodine complex, the acid and/or iodide salt can be added to the developer solution. The iodate image can be transferred to starch sized paper and the image rendered visible upon contact with the developer solution containing the other co-reactants.

Preferably, however, the developer fluid comprises only water or a water/alcohol mixture. Only small amounts of moisture are required for development. In fact, development can occur by passing the latent image through a heating zone maintained at temperatures ranging from about 50C. to about 150C. and a relative humidity of from about 75 percent to about 100 percent. Although, in general, it is considered preferable to employ organic acids for sensitization, dilute solutions of mineral acids such as hydrochloric acid can be employed in the developer composition thereby obviating the presence of an acid in the sensitized copy sheets.

When sensitization of the copy paper is conducted on a continuous basis by wetting a surface of the copy paper with the sensitizer composition, development can be conveniently conducted on a continuous basis by passing the sensitized sheet containing the latent image through a curtain of steam obtained by directing a stream or plurality of streams of steam transversely to the path of movement of the copy paper. After development in this manner, the copy sheets can be continuously air dried or forced dried such as by heating. in this manner, dry, developed copies can be conveniently and rapidly obtained.

The following examples further define, describe and compare methods of preparing multiple copies in accordance with the present invention. Parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 A typewriter master prepared on a conventional typewriter was placed in a support frame. Sodium iodate powder was cascaded over the surface of said master. Thereafter, the cradled master was turned upside down and shaken to remove excess powder. The sodium iodate powder adhered to the oleaginous image areas. The master was then passed through a set of metal rollers at a pressure of 100 pounds per linear inch resulting in an imagewise transfer of the sodium iodate to the rolls in the form of a reverse image. The transfer of the sodium iodate powder was only a partial transfer enabling the master to be reused to re-image the rolls a number of times.

Sensitized copy paper was prepared by treating a commercially available starch sized paper with a solution of the following composition:

5 gms. Citric acid 100 CC. 111 ethanolzl-hO i 1 gm. Kl

After treatment, the paper was allowed to dry. The sensitized paper was passed through the rollers whereupon a partial transfer of the sodium iodate in image configuration to the paper occurred. At this point, the imaged copy was not visible, i.e., a latent image in the form of sodium iodate powder contained on the sensitized paper was formed. The latent image was subsequently developed by spraying the paper with a fine spray of water. The developed image was purple-black in appearance. Twenty imaged copy papers were prepared from the single imaging of the metal rollers by the master. In an identical manner, the master was employed a total of four times to image the rolls thereby producing a total of imaged copies made from a single dusting'of one master. Moreover, the master can be repeatedly employed in this manner, since the duplicating process is non-destructive of the master.

EXAMPLE 2 Employing the identical procedure described in Example 1, copy sheets containing a latent image were developed by spraying said sheets with steam.

EXAMPLE 3 Employing the identical procedure described in Example 1, copy sheets containing a latent image were developed by passing said sheets through a heated zone maintained at C. and at a relative humidity of 100 percent.

EXAMPLE 4 A xerographic copy of the typewritten master employed in Example 1 was prepared using a 2400 Xerox Copier. The xerographic copy was warmed to render the image thereon slightly tacky. Thereupon, potassium iodate crystals were cascaded over the surface of said copy. The xerographic copy was then turned upside down and flicked with the fingers to remove excess iodate. The potassium iodate crystals adhered to the slightly tacky image areas of the xerographic sheet. The sheet was then passed through a set of metal rollers at a pressure of about pounds per linear inch resulting in an imagewise transfer of the potassium iodate to the rolls in the form of a reverse image. The transfer of the potassium iodate powder was only a partial transfer enabling the xerographic sheet to be re-used a number of times to re-image the rollers.

Sensitized copy paper was prepared by treating a commercially available starch sized paper with a solution of the following compositions:

5 gms. citric acid 100 cc. 1:1 methanol: H

1 gram Kl After treatment, the paper was allowed to dry. The sensitized paper was passed through the rollers whereupon a partial transfer of the potassium iodate in image configuration to the paper occurred resulting in the formation of a latent image on the copy sheet. The latent image was developed by exposing the latent image to a steam spray.

EXAMPLE 5 The following example illustrates a method of obtaining a reverse iodate image which can be employed as a master sheet in a direct lithographic process such as on a conventional rotary duplicating machine.

Ari oleaginous back-up sheet containing sodium iodate was prepared as follows:

A coating composition containing:

12.5% carnauba wax 10.5% microcrystalline wax 12.0% petrolatum 15.0% mineral oil 50.0% sodium iodate was prepared by admixing the components and forming a hot melt at temperatures between about 8090C. The hot melt was roller coated onto a suitable base sheet in weights of about 20 pounds per 3,000 square feet.

The back-up sheet was placed in contact with a conventional bond paper sheet and inserted into a typewriter. Typing was conducted on the bond paper. The pressure of the typewriter keys caused transfer of the iodate coating composition to the back side of the bond paper forming an iodate reverse image of the writing.

The bond paper containing the iodate reverse image was affixed to the rotary drum of a conventional rotary duplicating machine.

Sensitized copy paper was prepared by immersing starch sized paper in a bath comprising:

1.25 grams Kl 5.0 grams gallic acid 500 ml. 90% ethanol After immersion and impregnation of said copy sheets with the above sensitizing composition, the sheets were allowed to dry.

The sensitized copy sheets were fed into pressure contact with the reverse image on the master sheet resulting in the formation of a direct latent, i.e., an invisible image, on the copy sheets. The copy sheets were subjected to a steam spray to develop legible images. In this manner, 25 copies were obtained exhibiting good image quality.

EXAMPLE 6 Employing the procedure described in Example 5, a reverse image master was prepared using the coating composition therein described except said coating composition contained no iodate salt. Upon typing, the oleaginous back-up sheet formed an invisible oleaginous reverse image on the back side of the master sheet. The back side of the master sheet was then dusted with a 1:4 potassium iodatezpotassium iodide mixture. The mixture adhered to the oleaginous image areas and was easily shaken off the non-image areas. The master sheet containing the coated reverse image was fastened to the master roll of a conventional rotary duplicating machine.

Starch sized copy sheets containing no additional sensitizer were fed into pressure contact with the master sheet forming direct latent images on said copy sheets. The images were developed by application of a fine spray of an aqueous solution containing 10 percent l-lCl. Twenty-five sharply defined copies were thus obtained.

EXAMPLE 7 A conventional typewriter ribbon was thoroughly coated with sodium iodate by dredging the ribbon through a bed of the iodate salt. The ribbon was placed in a typewriter and employed in conventional manner to obtain a typed master sheet. The master sheet was fed between a set of rotating stainless steel rollers under a pressure of 100 pounds per linear inch whereupon the iodate image was partially transferred to the metal roller acting as an offset blanket.

Copy sheets were sensitized by spraying conventional starch sized paper with a sensitizing composition containing:

1.25 grams Lil 2.50 grams boric acid 500 ml. 9:1 ethanol: water, and drying said sheets.

The copy sheets were then fed between the nip formed by the offset roll and a stainless steel compression roll maintained under a pressure of 100 pounds per linear inch whereupon imagewise transfer to the copy sheets occurred. The copy sheets were developed by application of a steam spray. A total of copies were obtained.

EXAMPLE 8 Employing the procedure described in Example 1, a sodium iodate image was transferred to an offset blanket.

Sensitized copy sheets were prepared by impregnating starch sized paper with sodium sulfite. The copy sheets were then fed into pressure contact with the offset blanket whereupon a direct latent image was formed upon the copy sheets. The latent image was developed by spraying the copy sheets with an aqueous 15 percent HCl solution.

This Example illustrates the in situ formation of lodide by reaction of the iodate salt with the bisulfite generated upon development of the latent image containing both iodate and sulfite under acidic conditions. The iodide so generated reacts further with the residual iodate to form iodine and subsequently the starch-iodine complex.

EXAMPLE 9 The foregoing examples have illustrated various methods involving dry transfer of an iodate salt to copy sheets containing an iodide and acid and various alternative embodiments thereof. This example illustrates the use of wet transfer in accordance with the present invention.

The fluid tank of a typical spirit process duplicating machine was filled with the following solution:

12.5 grams K1 25.0 grams citric acid 400 ml. 1:4 ethanolzwater A master sheet prepared as described in Example 5 was clamped to the drum of the machine. In operation,

the copy sheet, wet with the above solution, was brought into pressure contact with the master sheet. Under these conditions, the master sheet was also wet by the solution and wet transfer occurred from the master sheet image areas to the copy sheet. With wet transfer, sensitization and development occurs simultaneously. Because of the rapidity of development in the technique, very little liquid was left to be evaporated from the copy sheet. Two hundred fifty copies were obtained from the master sheet.

EXAMPLE 10 The fluid tank of a typical spirit process duplicating machine was filled with a saturated solution of gallic acid in 400 milliliters of a 1:4 ethanolzwater solution containing 2.0 percent MnCl A master sheet prepared as described in Example 5 was clamped to the drum of the machine. In operation, an untreated copy sheet wet with the above solution, was brought into pressure contact with the master sheet. Under these conditions, the master sheet was also wet by the solution and wet transfer occurred from the master sheet image areas to the copy sheet. With wet transfer, sensitization and development occurs simultaneously. Because of the rapidity of the development technique, very little liquid was left to be evaporated from the copy sheet. In this manner, one hundred copies exhibiting a sharp brownish-black image on a white background were obtained from the master sheet.

EXAMPLE 1 l Employing the procedure described in Example with a bath containing a saturated solution of gallic acid in 400 ml. of a 1:4 ethanokwater solution, seven copies exhibiting a sharp brown image on a white background were obtained.

EXAMPLE 12 The procedure described in Example 5 was employed to obtain a master sheet containing an iodate reverse image. The master sheet was affixed to the rotary drum of a conventional rotary duplicating machine.

Sensitized copy paper was prepared by immersing previously untreated, unsized bond paper in a bath comprising a saturated aqueous solution of poly(vinyl pyrrolidone). After immersion and impregnation of the copy sheets with the above sensitizing composition, the sheets were allowed to dry.

The sensitized copy sheets were fed into pressure contact with the reverse image on the master sheet resulting in the formation of a direct latent image, i.e., an invisible image on the copy sheets. The copy sheets were subjected to a steam spray to develop legible images. ln this manner, twenty-five copies exhibiting a sharp dark reddish-brown image on a white background were obtained.

Although specific materials and conditions were set forth in the above exemplary processes in making and using the various components and methods of this invention, these are merely intended as illustrations of the present invention. Various other compositions and processes such as those listed above may be substituted in the examples with similar results.

Other modifications will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

l. A method for chemical reproduction of images by a chromogenic reaction of an iodate, an iodide, an acid, and starch comprising the steps of:

distributing finely divided iodate crystals in conformance with an image on a master sheet;

at least partially transferring the iodate crystals in image configuration to the surface of a copy sheet, said copy sheet containing starch, an alkali metal iodide, and an acid therein, to form a latent image on said sheet; and,

contacting said sheet with steam to thereby develop color on said copy sheet in conformance with the latent image.

2. A method for chemical reproduction of images by a chromogenic reaction of an iodate, an iodide, an acid, and starch comprising the steps of:

distributing finely divided iodate crystals in conformance with an image on a master sheet;

at least partially transferring the iodate crystals in image configuration to the surface of a copy sheet, said copy sheet containing starch, an alkali metal iodide, and an acid therein, to form a latent image on said sheet; and,

developing color on said copy sheet in conformance with the latent image by heating said sheet at temperatures between about 50C. and about 150C. in an environment maintained at a relative humidity of between about 50 and percent.

Claims (2)

1. A METHOD FOR CHEMICAL REPRODUCTION OF IMAGES BY A CHROMOGENIC REACTION OF A IODATE, AN IODIDE, AN ACID, AND STARCH COMPRISING THE STEPS OF: DISTRIBUTING FINELY DIVIDED IODATE CRYSTALS IN CONFORMANCE WITH AN IMAGE ON A MASTER SHEET; AT LEAST PARTIALLY TRANSFERRING THE IODATE CRYSTALS IN IMAGE CONFIGURATION TO THE SURFACE OF A COPY SHEET, SAID COPY SHEET CONTAINING STARCH, AN ALKALI METAL IODIDE, AND AN ACID THEREIN, TO FORM A LATENT IMAGE ON SAID SHEET; AND, CONTACTING SAID SHEET WITH STEAM TO THEREBY DEVELOP COLOR ON SAID COPY SHEET IN CONFORMANCE WITH THE LATENT IMAGE.

2. A method for chemical reproduction of images by a chromogenic reaction of an iodate, an iodide, an acid, and starch comprising the steps of: distributing finely divided iodate crystals in conformance with an image on a master sheet; at least partially transferring the iodate crystals in image configuration to the surface of a copy sheet, said copy sheet containing starch, an alkali metal iodide, and an acid therein, to form a latent image on said sheet; and, developing color on said copy sheet in conformance with the latent image by heating said sheet at temperatures Between about 50*C. and about 150*C. in an environment maintained at a relative humidity of between about 50 and 100 percent.