DE1249891B - Hot copying process - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

B 41m

German class: 15 k -7/05

Number: 1 249 891

File number: M 46668 VI b / 15 k

Filing date: September 27, 1960

Opened on September 14, 1967

B4 1N

The invention relates to a method for reproducing a graphic original using of fumes for the purpose of producing a corresponding image pattern.

Processes for reproducing graphic originals, in which the original is treated with vaporous substances and the drawing is transferred onto a recording sheet with the creation of a latent image, are known (German Patent 287 516). It is also known to produce a "latent" image on a receiving sheet provided with a thin metal layer and pressed onto a chemically pretreated original (cf. German Patent 908 978). In these methods, however, it is necessary to make the latent images formed visible by a subsequent chemical development step.

In the known thermographic reproduction processes using chemically reactive Heat-sensitive copy paper, the copy paper is usually under pressure in thermally conductive Brought into contact with the original, which then briefly suffices with an infrared component Radiation is intensively irradiated. The heating of the radiation-absorbing parts of the image Originals has a visible chemical reaction in the appropriate places on the copy paper accompanied. This creates a positive copy immediately without any further chemical or other treatment educated.

Physically heat-sensitive copy sheets are also known. One kind of it consists of a dark colored paper or film backing with an opaque surface coating is made of a clear, fusible material in particulate form. By melting of the particles in the heated areas, the coating is persistently transparent, so that the dark Background becomes visible. Another type of these copy sheets is based on that by the action of heat causing the molten coating to flow into an absorbent carrier, whereby a visible change in the heated area corresponds to the graphic original without further chemical or other processing is caused.

In contrast, the method according to the invention is characterized in that a starting sheet, containing a normally solid, vaporizable imaging substance, onto a receiving surface places the original sheet on the image parts of a pattern that is represented by the graphic original Thermal copying process

Applicant:

Minnesota Mining and Manufacturing Company, St. Paul, Minn. (V. St. A.)

Representative:

Dr.-Ing. H. Ruschke, patent attorney,
Berlin 33, Auguste-Viktoria-Str. 65

Named as inventor:
Bryce LaForge Clark,
Carl Stinson Miller, St. Paul, Minn. (V. St. A.)

Claimed priority:
V. St. v. America September 29, 1959
(843161)

is determined so sufficiently heated that the normally persistent solid substance is in vapor form in the template is transferred to the receiving surface, and that one has the steam on it condensed.

The present invention also enables reproductions to be made, namely in a one-step simplified process that does not require any subsequent chemical or other treatment requires. The copy obtained is no further discoloration on subsequent heating subjected, so that darkening of the background is avoided. It can be simplified Process to achieve the necessary copying temperatures are used. Compared to the Method mentioned at the beginning in which a latent image of the original is transferred to a recording surface is transferred, it is not necessary in the method according to the invention, the receiving layer by gassing or immersion in a bath and subsequent drying in a time-consuming manner to develop. Further, according to the present invention, the substances to be evaporated are below normal Storage and temperature conditions are stable, and it is not necessary to do so first apply immediately before copying.

The invention is generally based on the transfer of a normally stable solid, imaging substance in vapor form from a

3 4

Starting layer on a suitable recording surface. During this process, the reactive area in a drawing created by the graphic substance originally used by the steam-delivering Original is determined. In one embodiment sheet 13 on the printed areas of the graphic of the process, the imaging substance is applied to original 10 as described in connection with FIG. 1 described Transferred recording sheet, which had a color 5, transferred, evaporated again generating reactant for the substance and transferred to the transfer sheet 19 where contains, whereupon both substances are condensed into a condenser at the locations indicated by 20 visible copy react with each other. When held or absorbed form is held, the vaporizable substance itself is strongly colored. The transfer sheet 19 is then graisted from it no respondent separated on the recording io phic original. The image parts 20 are layer required. The vaporizable substance is clearly visible when a strongly colored one can vaporize the ink (or the printing ink) with which the barer component is used and form one graphic original is printed, either in front of a visible, direct, positive (right-sided) copy of the or incorporated after printing; or they originals, if they are transmitted through transfer sheet 19 can be considered a component of the printed sheet or 15 through it, for this purpose be a separate vapor-generating layer. must be transparent.

The invention will be explained in more detail with reference to the when the vaporizable substance as reaction associated The drawing described in which the participant is used is the one with the picture Figures partial cross-sections through different sheet-provided surface then onto the treated one arrangements are. 20 surface of a recording sheet 15, as shown in FIG. 4th

F i g. Figure 1 shows a graphic original 10 shown in Figure 1 laid out with the vaporized substance a carrier 11 is able to react to the image parts 12, and the whole is heated, printed or otherwise recorded with the evaporated reactant again are (e.g. a book page). Another example is from the transfer sheet 19 to the receiving unit lithographic printing plate with oil-absorbing 25 sheets 15 is transferred and through the implementation Image parts and water-absorbing background visible image parts 21 are formed, the image parts on a treated aluminum sheet. The parts of the graphic original 10 correspond directly. Parts of the image can be a hardened gelatin base. 1 and a resinous or oily oil receptive and the vapor-delivering sheet is pyro-surface coating contain. 30 gallol, transfer sheet 19 can be used

Against the printed surface of the original 10 a waxed or paraffinized paper is placed a vapor-forming sheet 13, which can consist of and the receiving sheet 15 a permanent layer of a thin, porous paper containing iron (III) stearate,
with a vaporizable phenolic compound, In the case of the in FIG. 5 specified embodiment z. B. pyrogallol, is impregnated. Heat is applied to 35, instead of direct heating, the structure is allowed to act, as indicated by the wave radiation with light rays of high intensity in lines 14, expediently by taking in, which are rich in infrared components, and sending the composite structure through the graphic original 10, the printed image a hot roller or ironing machine. The vapors parts 12 contains, is with its unprinted upperfrom the vapor-supplying sheet 13 - surface placed against the vapor-supplying sheet 13, which is presumably through absorption - condensed on the printed image parts of the original in contact with the reactive layer 17. That is in this of the recording sheet 15. The original treated image and background manner is shown in Figs. 2 and 3 basic parts of the surface of the original 10 have been referred to as the treated original 10a and serve different absorption capacities for the strahnun as a vapor-forming sheet during the subsequent 45 ment 23. Brief intensive irradiation calls for further processing. a preferred heating to the printed

The vapor-shedding sheet 13 is then produced by dividing the image (wavy lines 22). The transfer Receiving sheet 15 replaced, as shown in FIG. 2 shows, and the vaporized reactant from the the new assembled structure in turn sheet 13 is heated to the treated upper which can be converted with it, z. B. by passing through a hot roller. 50 surface layer 17 of the receiving sheet 15 leaves around-The Receiving sheet 15 consists of a carrier 16 set image parts 21 arise, which are directly the gemit a reactive layer 17 corresponding to printed image parts 12 of the original.

When the recording sheet 15 from the surface A device intended for short-term intense

of the treated original 10a is separated, it has irradiation of the composite sheet

Obtaining a visual graphical drawing suitable 55 may be a line light source consisting of

corresponds to that of the graphic original and in a tubular lamp with a linear

F i g. 2 are designated as converted image parts 18. Filament is made and surrounded by a reflector

The reproduction appears as a mirror image when it is. Such devices are in the U.S.

from the treated side of sheet 15, d. H. of patents 2,740,895 and 2,891,165 (German

the surface is considered, which was previously mentioned with 60 patent application M 27865 IXa / 57 c; German Aus

the image parts of the original in contact with legeschrift 1 151177).

Has. The image can be viewed as a right-sided image of the In a simplified embodiment of the above

The back of the receiving sheet 15 is considered to be the mode of operation described above

when the carrier 16 is transparent. Sheet and the graphic original into one

In Fig. 3, the treated original 10a is combined like 65 sheets, e.g. B. by surface treatment

at F i g. 1, with an intermediate of the rear or unprinted surface of the

Transfer layer 19 brought into contact and originals with pyrogallol or another

the assembled leaf structure is heated again. steamable connection or by graphical

5 6

Signs of a previously steam-impregnated den. The quantitative ratio of binder to

Sheet printed or otherwise applied. Respondents can be very different; in

will. In some cases the binder can fall off and

F i g. 6 shows a further embodiment in which reactants are distributed within the copy sheet of the image portions 12b of the graphic original 106 5, in which case it is then produced by the paper from a printing ink which is fiber-bound and protected. In the case of larger amounts of vaporizable image-forming binder that are susceptible to conversion, it is advisable to contain a combination substance. The sheet is printed with the tions of volatile solvents to be used, placed on the reactive surface 17 of a surface that forms a porous binder film and thereby receiving sheet 15. By the action of io a slight admission of the evaporated reaction part heat, the reactive substance in taker to the iron (III) vapor form to be reacted with these will allow from the printed areas on the same reactive surface of the copier with stearate or another reactant.

Papiers transferred and a visible conversion pyrogallol and iron (III) stearate leave intense

image 21 formed. The resulting reproduction can have 15 colored, high-contrast images on one practically

also as a direct copy on an opaque white background with high reaction speed

Recording sheet according to the in connection with F i g. 2 speed and at easily achievable temperatures in

The two-stage working method described above is generated in the range from about 80 to 150 ° C, iron (III) -

the. Are non-reactive, vaporizable imaging soaps of other long-chain fatty acids

According to the same methods, substances can also be effective. These sub-

driving used and transmitted. punch to be insoluble in water and usually one

The use according to the invention of a conversion melting point in the range from about 70 to 120.degree

vaporizable constituent and one. Instead of pyrogallol, others can

correspondingly reactive recording sheet, normally stable, vaporizable solid pheno-

allows you to choose from a large number of respondents, e.g. B.

of vaporizable substances that are either colorless catechol.

or they can be intensely colored so that they can be intensively The phenol-iron combinations provide a deeply colored and permanent copies. A large black or blue-black image and therefore number of copies can with very little very effective for copying machine print amounts of vaporizable reactants from 30 _o j _he printed originals with black image on white a single treated original advertising produced underground. It can be beneficial for certain purposes. The coating for the receiver sheet can be liable to produce variously colored images. Paper, film, fabric, wood or various others. For example, nickel salts (such as nickel acetate) can be applied to surfaces in order to produce copy paper on the image areas with steams from any graphic originals from a steam-producing sheet, the dimethyl. contains glyoxime or thiourea, to red resp.

Iron (III) stearate is used as the compound that is used for the black parting of images. Cobalt-reactive recording sheet or copy sheet in acetate copy paper that is compound with fumes from ammo Treated with vaporizable phenolic bild- nium thiocyanate produces a blue one generating substances, such as pyrogallol, applicable 40 Fig. Ammonium molybdate and 8-hydroxyquinoline is preferred. A suitable form of iron (III) - provide a yellow image; Methyl orange and fumes stearate is produced as follows: to an aqueous solution of heated oxalic acid gives an orange-red image, Solution of 3 moles of sodium soap from hand-ice and a copy paper, which is a colorless reaction Triple-pressed stearic acid obtained from the unproduct of malachite green and octadecylamine Melting point 53 ° C, which probably holds a 45, gives a green picture when it comes to fumes smaller proportion of other higher fatty acids are treated by oxalic acid. Particularly good ones contains an aqueous solution of 1 mole of iron (III) - results are also obtained when protocatechu sulfate given. The precipitated water-insoluble acid in the steam-supplying layer and silver-iron (III) stearate is filtered off, successively with behenate or a mixture of silver behenate and Washed with water and alcohol and used in the receiving layer in the case of space 50 behenic acid, temperature dried. The solid product softens When pyrogallol and iron (III) are combined - or melts within the range of 70 to stearate e.g. B. the vaporizable reaction part -95 ° C. In a solution, the connection is transferred unchanged when heated and Nitrocellulose in a mixture of toluene and reacts at least at a sufficiently elevated temperature Acetone dispersed (being the amount of nitro-55 directly with the reactant in the copier cellulose a quarter of the weight of ferric paper. In other cases, e.g. B. in the Kombistearats is) by the mixture in a spherical ion with oxalic acid or thiourea, can Mill is ground until a uniform application- the vaporizable constituent due to thermal disintegration Dispersion arises. The dispersion will settle in the originally in the printing ink suitably applied to the surface of the paper 60 or sub contained in the steam providing sheet, z. B. with the squeegee, and dried. punch arise. In all cases, however, a The coated sheet is at least in the same reactant in vapor form to the copy level like the untreated paper transferred to heat sheet, where then the visible copy through and light steady. Condensation and conversion occurs as indicated. Nitrocellulose is the preferred inert heat- 65 Another decomposable substance that is resistant to heat Binders, but also other binders deliver a transferable vapor, is gallic agent, z. B. Äthylceüulose, polyvinyl acetate, poly acid, especially in the form of a liquid ink, styrene and polyvinyl butyral, can be used. As an example, a small amount of gallic acid

dissolved in normal fountain pen ink and this solution treated or coated, e.g. B. with Pig-

for making records, such as in cement, fillers, binders or others

binding with F i g. 6 is used. The desired substances or mixtures to create a

Original was obtained under direct contact with the ink background with increased contrast,

with the iron (III) stearate treated surface 5 to the adhesion of the colored image-forming

of the copy paper is heated. Here, an off-substance, z. B. with small amounts of solvents

Sufficient amount of non-volatile gallic acid disintegrating or fixing agents or the like. To promote or to

sets (presumably for vaporizable pyrogallol) and other purposes.

the product transferred to the ferric stearate Besides quinalizarin green, the following have been found

and reacted with this, with a clear, distinct io dyes being particularly suitable for production

Mirror image of the original on the surface of copies of typescript originals

Copy paper is created. untreated paper receiving sheets according to FIG. 7th

Instead of being in a liquid ink, the decomposable one can be: Alizarin Irisole N, Chrysoidine R, du Pont

or vaporizable reactants also in Oil Blue A, Rhodamine B Extra, Ethyl Violet AX,

15 Auramine Base, du Pont Oil Orange, du Pont Oil

be brought, e.g. B. with pencil, carbon paper Yellow, du Pont Oil Brown N, du Pont Oil Red,

or an impregnated typewriter tape. Latyl Violet BN Crude, Acetamine Scarlet B, Methyl

It can e.g. B. Pyrogallol in a colored wax Violet 2B Base Cone, National Indigo Nacco Pdr.,

mass distributed and shaped into a pencil lead Azosol Brilliant Yellow 8 GF, Sudan Red BBA,

or as a thin coating on an image-providing 20 Sudan Green 4B and Victoria Green Base.

Carriers made of paper or fabric can be applied. Various mixtures and combinations of these

The by means of such structures on paper and other suitable dyes can be used

Images produced by decomposition are copied by being. Responsive and unreactive

they may come into contact with a suitable, decomposable constituent, if appropriate

capable recording sheet as shown in FIG. 6 described, 25 can also be used in a mixture,

be heated. The dye can be transferred to a paper carrier

According to a further embodiment, one can simply rub the dry powder onto an emulsion of ferric stearate in a solution, whereby either an intermediate layer of gelatin in water is produced, which is applied as a coating carrier sheet or a coated original is applied to an aluminum plate and dried is provided. The surface of a suitable paper will. A print side, on which the printed areas can also consist of the solution of the dye in a normal printing ink, was coated with a volatile solvent, because by heating it in contact with a vapor, this enables better penetration and a larger supplying sheet, reactive with pyrogallol vapor Uniformity is guaranteed. So you can do it and then against the dry gelatine top- 35 z. B. du Pont Oil Orange held in acetone to a 10 ° / ₀ igen area and heated again. The pyro-solution dissolve and evenly on the soft, non-gallol vapor from the picture parts got into the gel-glossy surface of thin "Yankee finish" - tine coating and reacted with the iron (III) stearate paper, which then either as steam formation of water-soluble substances, which can be used as an interleaf or as a steam-delivering then with the gelatin to a relatively 40 base for the graphic original. water-insoluble reaction product reacted further. The remaining areas of the gelatin coating were Example 1
then removed by washing with water, whereby

the insoluble parts that make up the image parts of the A used lithographic plate with colored

printed graphic originals, back 45 oleophilic parts of the image on a hydrophilic treated

stayed. The plate could be used as a lithographic plate with a dry aluminum support

for direct printing on untreated paper sheets of paper brought into contact that are evenly

be prepared. and has been thinly coated with pyrogallol.

According to FIG. 7 is made by irradiating the graphi- The composite structure is made by a

see Originals 10 sent a strongly colored vaporizable 50 hot iron. The sheet of paper is removed

Substance from the steam-delivering sheet 13 on the separates and through a receiving sheet of paper

untreated receiving sheet 24, which replaces a thin surface coating of

It is advisable to use a white bound paper, with iron (III) stearate bearing, whereupon the whole thing again

copied image parts 20 from transferred condensate is sent through the mangle. A reflection

resulting in a right-sided reproduction of 55 of the printed image parts of the lithographic plate

Originals form. Quinalizarin green dye is a is visible on the coated surface and

Example of a strongly colored, vaporizable, nor- can from the other surface of the half-way

painstakingly stable, solid image-forming substance visible on the receiving sheet as a direct or

for this purpose. the right-sided image can be viewed.

The use of a clearly visible 60 The same results are achieved if the

vaporizable substance, such as those associated with lithographic plate through a page of a book

Fig. 3 and in particular with F i g. 7 printed on thick white paper. allows the production of copies of a

graphic original on untreated recording example 2

leaves or surfaces that do not react chemically. 65

Suitable recording sheets are untreated pa- The lithographic plate of Example 1 is used

pier, fabric, non-woven nonwovens, polymers after heating in contact with the pyrotechnic

Films and metal foils. The recording sheet can touch gallol paper again in the lack

9 10

warmed with waxed paper, a strongly paraffi- the same weight as the methyl gallate dispersed

ned paper that usually yaws as waterproof so that the coating does not tear, but this is it

Wrapping paper is used. The waxed not necessary. The dry sheet is first

Paper is then typed against the ferric stearate, with movable types

coated paper held and reheated. 5 or written on by hand, with one in the infra

A right-sided reproduction of the original is used in ink or printing ink that absorbs red areas.

received on the admission sheet. is turned. The resulting original, that too

a steam! The delivering layer is turned against one with it

Example 3 held convertible recording sheet and the thermo-

lo subjected to graphic copying processes, as in the

An original is described by writing on a last paragraph of Example 4. Up to

Ordinary letterhead with a liquid ink fifty or more copies of the same original

a few percent of gallic acid can be produced in this way,

have been added. The dry leaf will. .

against a transparent recording sheet with a 15 B e 1 s ρ 1 e 1 ο

Thin coating of iron (lll) stearate, which is an original by writing or printing

is bound to a transparent paper backing, made with an aqueous ink or printing ink,

and the whole thing is sent through the hot iron, the thiourea and a water soluble dye

a true-to-page copy is obtained if contains. The original comes with a recording sheet

this brought into contact from the rear side of the receiving sheet 20, which is made by coating

is looked at. Further copies of the same original paper with a dispersion of nickel acetate in

can by repeating the process from a solution of ethyl cellulose in toluene and

be asked. Drying at room temperature has been prepared

For the 1 4 ^ls ^ ' ^ ^urcn heating the parts of the picture - either by

25 ironing or irradiation - is a reproduction

A sheet of thin polyester film, which is available under the production of the image parts on the recording sheet from the trade name "Mylar", is also called. Several copies of one with a coating weight of 0.6 g per 0.09 m ^{a can be made} with a single original,
a layer of a mixture of silver behenate. ■ \ η
and an excess of protocatechuic acid to 30 Example /
together with methyl methacrylate as a binder over- Quinalizarine green (English: Quinalizarine green, which is applied from a dispersion in acetone base) is in such an amount in a liquid solution becomes. The sheet is placed against a printed original medium that contains a strongly colored ink, which then stands for a short time with an intense radiation, which is then irradiated to produce a handwritten infrared component, 35 borrowed graphic original on white paper, a reproduction of the black image areas is turned. The dried sheet is formed with that in the heat-sensitive coating. described surface (front side) on an empty The process is known as »front printing« (English: sheet of paper and the whole thing through a lack »front printing«). sent, with the back of the original with the

The copy is then with its covered upper heated shoe in contact with the machine, surface in contact with a receiving sheet.
with silver behenate in a polymeric binder. .
has been made. Pigments such as zinc oxide, for example
fusible resins such as "Piccolyte S-135" (a poly 45 A sheet of paper is on part of its upper terpene resin), and other additives may expedient surface with a l ° / _o solution of du Pont Oil be incorporated excessively, but are not essential orange in acetone and on the rest of the same borrowed components of the coating of the receiving surface with an identical solution of du Pont layer. The copy is irradiated again to coat the Oil Blue A. A letter will be made with the thermographic copy. Sandblasted by machine on the uncoated surface under suitable conditions of time and wrote. The resulting original is created with the intensity of a "latent coated surface on an untreated sheet of image" on the recording sheet, which is then placed in a paper by heating and thermographically irradiated. An oven or visible copy of the letter over a hot plate is obtained in the colors that will; a direct reproduction of the 55 will correspond to the position of the dye coatings,
printed original. By irradiating. .
under somewhat more drastic conditions an example is immediately set
the visible image is formed on the recording sheet, thin paper is saturated and dried with a dilute solution if it is still in contact with the intermediate of du Pont Oil Orange, or the sheet provides steam. 60 The intermediate sheet obtained is between an un-. -ic-treated paper receiving sheet and the back Example 5 _e j _nes thin printed originals placed. Thieves-

Thin, porous paper is printed on both sides. Obeifliehe is brief and intense with on

irradiated very thinly with a solution of about 20 parts of infrared components rich light, whereby

Methyl gallate and 1 part polyvinyl acetate as binding 65 a copy is obtained on the recording sheet,

Medium in a mixed solvent of methyl Up to 75 to 100 copies can be made with the same

isobutyl ketone and alcohol coated. In the over- interleave by repeating the procedure

Zugslösung is expediently made in the corn starch.

Example 10

The procedure of Example 9 is repeated, in this case with a thin piece of silk screen cloth between the receiver sheet and the intermediate dye-providing sheet. The transferred image parts show the pattern of the silk thread as uncolored or less clearly colored lines.

B e i s ρ iel 11

A page of a magazine with black letters covered with varnish inks on a glossy white paper is dipped in a dilute solution of 8-hydroxyquinoline in acetone, drained, dried, placed on a receiving sheet with iron (III) stearate and covered with a hot Iron heated. A colored reproduction of the printed areas is viewed as an inverted or mirror image received on the admission sheet. Using the same procedure, but using the 8-hydroxyquinoline is applied from a dilute solution in carbon tetrachloride or toluene, becomes a negative Reverse image obtained, the colored areas of which correspond to the unprinted background areas of the original correspond.

When a dilute solution of "Autol Brilliant Red BND" in toluene is applied to a printed original becomes a negative reversed image when ironing the treated original on a Preserved sheet of white paper.

Example 12

Thin paper comes on a surface with a thin coating of isopropyl catechol and provided with a polymeric binder. The obtained vapor-producing sheet becomes with the coated surface placed on a sheet of paper previously written on the other side with the typewriter has been, and the described surface becomes short as in thermographic reproduction processes Time intensely irradiated. The coated steam-providing sheet is then replaced with a receiver sheet, the has a surface layer of silver behenate and a polymeric binder, and the whole thing is done again irradiated from the surface described. The described sheet now serves as a steam-delivering one Sheet by removing the steam that has previously condensed on the irradiated scriptures the recording sheet transferred and there with the silver soap to corresponding visible parts of the picture is condensed.

Instead of the untreated original, an ink-absorbing paper or Another thin carrier fleece can be used, which has a thin, waxy, resin-like layer on the back or other oleophilic coating similar to the paraffin coating of the transfer sheet of Example 2 as a temporary location for phenolic or other vaporizable imaging Substance serves.

Of course, the vaporizable image-forming substances used according to the invention - both the reactive and the non-reactive - must practically not evaporate under normal room and storage conditions, which is to be expressed by the designation of these substances as "normally stable substances". At the temperatures used during the process, evaporation occurs rapidly enough that the desired effect occurs within the limited time described. Useful vaporizable substances form fast enough steam when they are not heated to an evaporation temperature of about 16O ⁰ C as. If z. For example, if a small amount of du Pont Oil Orange was covered with a piece of white filter paper in a small aluminum dish about mm deep, an orange-red stain was formed on the paper when the dish was placed on a metal block heated ^{to 100 ° C. for a moment.}

Claims (3)

Patent claims: 1. Method of reproducing a graphic original using fumes for the purpose of producing a corresponding image pattern, characterized in that a starting sheet, which is a normally contains solid, vaporizable imaging substance placed on a receiving surface, the parent sheet on the image parts of a pattern which is determined by the graphic original, so heated sufficiently that the normally persistent solid substance is in vapor form in the Original is transferred to the receiving surface, and that the steam is condensed thereon. 2. The method according to claim 1, characterized in that one is used as a vaporizable image-generating Substance uses a strongly colored organic dye. 3. The method according to claim 1, where at the yerdjunpjf bar e part of the generating substance ~ and the surface of the receiving sheet are able to react with one another in a hightable manner, characterized in that, for the production of a large number of copies of a graphic original, the to be copied graphic information in the form of preferably radiation-absorbing image areas on the surface of a significantly less radiation-absorbing base sheet, which on its entire opposite surface has a layer of a normally stable, solid, vaporizable image-forming substance, that the base sheet with this last-mentioned surface against a first The recording sheet is placed and the surface provided with the graphic information is briefly exposed to intense radiation in order to avoid a local temperature rise in the image areas and evaporation of the image-forming substance from the original sheet onto the recording sheet, for example u cause a first copy to be made, and that the irradiation process is repeated with further recording sheets in order to obtain further copies. Considered publications:
German patent specifications No. 287 516, 908 978. 1 sheet of drawings 709 647/481 9. 67 © Bundesdruckerei Berlin