US3315598A - Copying of graphic originals - Google Patents

Description

April 25, 1967 R. OWEN 3,315,598

COPYING OF GRAPHIC ORIGINALS Filed July 28, 1960 /C/Ci.

MMQLW Yrnographic copy-paper.

United States Patent O 3,315,598 COPYING oF GRAPHIC ORIGINALS Richard Owen, North St. Paul, Minn., assignor to Minne- This invention relates to the thermographic reproduction of hand-written, typed, printed or other graphic originals. An important aspect of the invention involves the preparation of heat-stable, right-reading reproductions employing conventional visibly heat-sensitive opaque ther- The invention is directed both .to novel processes and to novel compositions and sheet materials.

Thermographic processes for the reproduction of differentially radiation-absorptive graphic originals, as described, for example, in Miller U.S. Patent No. 2,740,896, involve the application to a visibly heat-sensitive copysheet of a heat-pattern originating from the brief irradiation of the original with intense radiant energy. The heat-sensitive layer is preferably held in close contact with the printed surface, so as to obtain maximum utilization of the heat-pattern and to provide maximum sharpness and definition of the image-forming areas. One form of copy-sheet accordingly consists of a visibly heat-sensitive coating on a thin flexible transparent backing. Irradiation through the copy-sheet, i.e. by front-printing, and with the sensitive coating in contact With the printed surface, -then produces a copy which is viewed through the transparent backing as a right-reading reproduction of the original.

Translucent or opaque backings are available which are adequately transmissive of the radiant energy employed and which are easiervto handle than are the thin transparent webs just described. Copy-sheets prepared with such backings may similarly be thennographically front-printed7 but the resulting copy is visib'le only from the coated surface and therefore as a mirror image of the original. Where possible, such copy-papers are therefore ordinarily used for back-printing, which however is limited to use with thin heat-conductive originals printed on one side only.

The present invention in one aspect provides for the preparation, by thermographic front-printing techniques, of right-reading reproductions on opaque, sturdy, easily handled backings.

The visibly heat-sensitive copy-sheets employed in thermographic reproduction remain visibly heat-sensitive in background areas. Subsequent application of heat may therefore distort or obliterate the copy. The present invention makes possible the stabilization of the initial reproduction against subsequent heating, and provides for.

a permanent copy.

The invention also makes possible the reproduction of graphic originals by lithographie printing techniques using a lithographie master prepared by a process involving thermographic duplication. These yand other objects and advantages of the invention are attained by means of an image transfer procedure as hereinafter described and particularly in connection with the accompanying drawings;

-FIGURE 1 illustrates conventional thermocopying techn1 ue:

IFIGURES 2 and 3 illustrate a thermocopying technique in accordance with one embodiment of the present invention;

FIGURES 4 and 5 illustrate a thermocopying technique in accordance with a second embodiment of the present 70 invention wherein the transfer sheet may be used as a lithographie master; and

3,3 15,5 98"y Patented Apr. 25, 1967 ICC FIGURE 6 illustrates a thermocopying technique in accordance with a third embodiment of the present invention.

FIGURE 1 illustrates conventional thermocopying technique, for example as described in the Miller patent above referred to, in which a graphic original 10 is irradiate with intense radiation from a source 11 through a visibly heat-sensitive copy-sheet 12 having a heat-sensitive layer 13 on a visibly transparent, radiation-transmissive backing 14. The radiation is preferentially absorbed in the inked areas 15, providing a localized heating eiect which causes a visible change in corresponding areas 16 of the heat-sensitive layer 13 to produce a right-reading reproduction of the graphic original as viewed through the backing 14.

In FIGURE 2, in accordance with the principles of the present invention, the thus treated copy-sheet 12 is next pressed against a heat-activatible sheet 17, having a normally non-tacky, heat-activatible adhesive layer 18 0n a backing 19. Heat and pressure are conveniently provided by means of rollers 20, 21 or by other means as desired. The adhesive layer 1S is activated and is adhered to the sensitive coating 13. The composite is next cooled to room temperature, and the lbacking 14 is stirpped away from the sensitive layer 13 which remains adherently bonded to the transfer sheet 17, as shown in FIG- URE 3. As viewed from the exposed surface, the sensitive layer 13 provides a direct-reading reproduction of the printed original 10.

When the copy-image is itself radiation-absorptive, a source 11 of radiant energy may alternatively be employed in providing a localized heating effect at the image areas. The adhesive layer 18 is thereby locally activated at those areas in contact with the image areas of the sensitive layer 13 in the composite of FIGURE 2. Pressure may simultaneously lbe applied by any convenient means, for example through a transparent cover plate or lm, or by holding the composite under tension over a convex supporting surface. The image areas are thereby selectively adhered to the adhesive layer. Removal of the ybacking 14 by stripping then removes the unchanged portions `22 of the sensitive layer '13, leaving the imageforming areas 16 adherently retained by the adhesive layer 18 of the receptor sheet 17, as illustrated in FIGURE 4. Such a copy is no longer visibly changed on further heating.

In those forms of heat-sensitive copy-paper in which the 'heat-images formed are not lpreferentially radiationabsorptive, the energy source `11 of FIGURE 1 may still be employed, in conjunction with suitable pressure-applying means, in activating the adhesive layer of the sheet 17 of FIGURE 2. For this purpose, the sheet 17 is itself made radiation-absorptive, e.g. 'by employing a suitably colored backing l19 or by incorporating small amounts of carbon black or the like in the adhesive layer 18. Since irradiation then causes activation of the entire adhesive layer, the resulting separation occurs as illustrated in FIGURE 3.

In `some instances the image-'carrying transfer sheet of FIGURE 4 may subsequently be employed as a -master sheet in the lithographie duplication of the image. As illustrated in 'FIGURE 5 there is rst applied a coating of a fountain solution 423 which is preferentially accepted -by the exposed surfaces of the heat activatible adhesive coating 18, followed by application of a coating of an ink composition 24 which is preferentially accepted by the exposed surfaces of the image areas 16. The ink is then transferred to a receptor sheet as in conventional lithographie duplicating. A negative print is produced where the preferential receptivity of the image and Ibackground areas is reversed.

I at room temperature.

1 Twenty parts by weight Example 1 A heat-sensitive copy-sheet is first prepared by applying .a thin uniform layer of a iuid mixture of reagents and binder to thin transparent paper (Ecusta -condenser tissue) by knife coating at -an orifice 4of 3 mils, and drying The coating mixture contains the following in parts by weight as indicated:

Mixture -of equal molar parts of silver behenate and behenic acid dispersed in ethyl acetate at con- The white copy-sheet is placed over a graphic Voriginal printed in black ink onV White paper, and the composite is momentarily exposed to intense radiation from an incandescent filament in the thermographic copying process hereinbefore noted, producing a copy of the original image in brownish black dense letters on a white background. The exposure is accomplished in a thermocopying machine as described in Kuhrmeyer et al. Patent No.v 2,891,165. i

A heat-activatible receptor sheet is prepared by applying a thin uniform layer of amixture of 33 parts by weight of polyvinyl butyral resin, 33 parts of waxy hydrogenated castor oil, 22 partsV of Vliquid chlorinated diphenyl, and 1l Yparts of Z-biphenyly-l diphenylphosphate, to 45'pound book paper.- The coating is applied at a rate of 18 grams per square foot and at an elevated temperature at which the mixture is uid. The coating is VVnon-tacky at norma-l room temperatures but softens and becomes sticky at temperatures o-f the order of 65"Y C. The copy is placed with the imaged coated surface in Ycontact with the coated surface of the receptor sheetrand the composite is again passed through 'the thermocopying machine and briefly intensely irradiated, with the copy toward the source of radiation. The exposure is controlled to provide suicient heating at the image areas to soften and activate the adhesive coating while avoiding any-'visible change at the background areas. The

Parts centration 10 Y Ten-percent solution of polystyrene reisn 1n acetone,

containing added 2% of protocatechuic acid 30 composite Vis then cooled and the paper backing of the Y copy-sheet isV stripped away, taking with it the unchanged and still heat-sensitive coating at the background areas. The visibly darkened -image areas of theheat-sensitive coating remain adherently bonded to thereceptor sheet; w The heat-sensitive background areasof the copysheet may Vnow be-visibly changed to a brown-black color by heating, e.g. on a heated plate or inran oven, to produce vaV negative transparencyof the graphic original.

Example 2 Y 'The heat-sensitive coating of Example 1Y is applied to map overlay tracing paper 'in-place of the condenser tissue there employed. A thermographic copy of a graphic original is prepared and the copy placed in contact with the adhesive receptor sheet of Example 1. The

composite is subjected toheat and pressure by pressing Vwith a atironat a temperature just below that required to cause .a visible change inthe background areas of the heat-sensitive.copy-sheet. After cooling, the'tracing paper is stripped away.V The entire heat-sensitive layer is found to remain adherently-bonded to the receptor sheet;

Y i Example 3 Y. In this example anormally non-tacky heat-activatible adhesive composition initially included Vin Ythe composition of the visibly heat-sensitive Vcoating Yis transferred to an uncoated paper backing simultaneously with the image-'forming components. v

of mercurio behenate isY rst dispersed in a'mixture of 48 parts commercialheptane and 32 parts acetone by milling on a ball mill.' Separately, one-half part of s-diphenyl carbazide is dissolved in a mixture of 45 parts toluene and 45 parts acetone.

, ferentilally radiation-absorptive graphic original, coma visible reproduction of the'printed image areas in-.the 1 heat-sensitive coating. The copy is then placed with the imaged surface against a rough surface bond paper and the composite againirradiated. The image portionsrof the copy are selectively softened and adhered lto the bond paper; on stripping the two sheets apart, a distinct copy of the image remains on the paper, althoughY a majorproportion of the image material remains on the copysheet. Repeating the same procedure'with further sheetsy of the bond paper produces a numberrof additional copies Vbefore the image material is depleted, as many 'paseiglit copies having thereby been prepared. The transferV step isillustratedpreviously imaged portions 16 of the heat-sensitive-and heat-activatible layer 13 are selectivelyV softened and adhered to the untreated paper 19., and portions thereof' remain on the paper-when the copy-sheet 12'. is stripped away. Y Multiple copies have'somewhat analogously been pre- :pared by the methods described in Examplesl V1 and-2f,V where the polystyrene resin'binderV there employed was replacedrby Va somewhat softer resinoiis material. Y

The materials transferred at` lthe image areas in Example 3 are'organophilic in nature, whereas the bond paperY receptor sheet is hydrophilic. Under these condif.

tions it becomes possible tofprepare further `copies'fby lithographie reproduction.- The background areas are' first coated Vwith an aqueous fountain solution, such as a -V dilute'solution of arabic in'water, which isY selectivey 1 ly retained by these lhydrophilic surfaces. Y Oil-based ink is next applied and is selectively retained by the oleophilric surfaces of the image areas.V The ink is then'r'transferr'edV under pressure topa paper receptor, either directly or by Y means of an intermediate blanket roller. YSuitable coated or strengthened hydrophilic sheet materials may replace the bond paper Where longer runs are desired.

-Lithographie reproduction may also beV carried outV Y Y.using heat-activatible adhesiveV receptor sheets as the f lithographie plates, particularly by incorporating inthe adhesive layer a hydrophilic component suchgas a water-V` Y soluble gum or a'hydrophilic inorganic filler-'such as silica j gel, or by the use of anV ink-repellent heat-activatible ad f hesive such as a waxy water-soluble polyethylene glycol.

V.Systems in which Ythe'adhesive-coating is oleophilicV and the transferred heat-image material'is hydrophilic are a-lso. i

contemplated, the Vcopy resulting Vin Vthis case being a negative rather than Y based inks. ,Y Y

What is-claiined is as follows:Y v Y .1. The method of preparing a reproduction ofr'ardifprising: subjecting a heat-sensitive copy-sheet'to localizedr heating at'areas corresponding'to'image-forming areas of said original by a thermographic process to provideY a visible. reproduction of said image-forming areas, saidVV i copy-sheet includingY a visibly heat-sensitive coating-on a5 flexible carrier; placing said copy-sheet with its coated surface in pressure-contact with the heat-activatible sur-V face of a normally non-tackyAadhesivereceptorsheet and heating at least the portions nof said-heat-activatible .sur-'gf face corresponding to saidv image-forming areas toi pro- Y vide adherent bondin'g'between said coating-and said's'uri face while avoiding visible change at background Vareas' j Y Y of said .copy-sheet; and removing said carrier byV stripping Y 2. The method of preparing a reproductionof a dif-Q Y.

' FIGURE 6.5 Yuit.V

a positive'copy when usingV oilferentially radiation-absorptive graphic original, comprising: subjecting a heat-sensitive copy-sheet to localized heating by a thermographic process at areas corresponding to image-forming areas of said original to provide a visible reproduction of said image-forming areas, said copy-sheet including a radiation-transmissive flexible carrier and a heat-sensitive coating which is permanently visibly changed and rendered strongly radiation-absorptive when heated in said thermographic process; placing said copy-sheet with its coated surface in pressure-contact with the heat-activatible surface of a normally non-tacky adhesive receptor sheet and briey strongly irradiating the heat-sensitive coating to cause activation and bonding of said adhesive at image areas while avoiding visible change at background areas of said copy-sheet; and removing said flexible carrier by stripping.

3. The method of making a lithographie master printing plate for multiple reproduction of a graphic original, comprising: subjecting a -heat-sensitive copy-sheet to localized heating by a thermographic process at areas corresponding to image-forming areas of said original to provide on said copy-sheet a reproduction of said imageforming areas, said copy-sheet including a exible carrier and a heat-sensitive coating thereon which is visibly changed and rendered' strongly radiation-absorptive when heated in said thermographic process; placing said copysheet with its coated surface in pressure-contact with the heat-activatible surface of a normally non-tacky adhesive receptor sheet and briefly strongly irradiating the heatsensitive coating to cause activation and bonding of said adhesive at image areas while avoiding visible change at background areas of said copy-sheet; and removing said flexible carrier, together with background areas of said heat-sensitive coating remaining attached thereto, by stripping, whereby to expose areas of said adhesive coating corresponding to said background areas; one of said adhesive coating and said heat-sensitive coating being hydrophilic, the other being organophilic.

4. The method of preparing -a reproduction of a differentially radiation-absorptive graphic original, comprising; subjecting a heat-sensitive copy-sheet to localized heating by a thermographic process at areas corresponding to image-forming areas of said original to provide a visible reproduction of said image-forming areas, said copy-sheet consisting essentially of a flexible carrier and a heat-sensitive coating thereon which is permanently visibly changed to a strongly radiation-absorptive colored state when heated in said thermographic process and which includes a heat-activatible normally non-tacky soft polymeric binder material; placing said copy-sheet with its coated surface in pressure-contact with a receptor sheet; briey strongly irradiating the image lheatsensitive coating to cause activation and bonding of said binder material at colored image areas to said receptor sheet while avoiding visible change at background areas of said copy-sheet; and separating said receptor sheet, together with adherently bonded portions of said copysheet coating retained thereon, by stripping from said copy-sheet.

5. The method of copying comprising: briefly exposing to intense radiant energy a differentially radiationabsorptive graphic original while in heat-conductive contact with a copy-sheet having a visibly heat-sensitive coating on a exible carrier, to provide a corresponding differential heat pattern sufficient to form on said copy-sheet a visible copy of said original; placing said copy-sheet with the coated surface in contact with a receptor sheet and heating the composite at least at image areas of said copy to an adhesion-inducing temperature; and stripping from said recept-or any portion of said copy-sheet not adherently bonded thereto; at least one of said copysheet and said receptor sheet having a thermoadhesive normally non-tacky surface coating which is adhesive when heated to said temperature.

6. The method of copying comprising: -briediy subjecting a differentially radiation-absorptive graphic original to intense radiation from an incandescent filament while the original is in heat-conductive contact with a copysheet product having a heat-sensitive coating, to create at the image areas of said original la heat pattern which is conducted to `a copy-sheet and effects a permanent change in said coating at areas corresponding to said image areas; placing the copy-sheet with its said coating in pressure-conatct with the surface of a receptor sheet, at least one of said coating land said surface comprising a heat-activatible normally nontacky adhesive bonding material; heating the composite at least at image areas of said copy to an adhesion-inducing temperature for said bonding material, to effect adhesion between said coating and said surface at the heated areas; and separating the copy-sheet and receptor sheet to provide on said receptor a copy of said graphic original.

References Cited by the Examiner UNTTED STATES PATENTS 2,503,758 4/1950 Murray lOl-426 X 2,663,654 12/ 1953 Miller et al.

2,721,821 10/-1955 Hoover 156-230 2,740,896 4/ 1956 Miller 250-65J1 2,808,777 10/ 1957 Roshkind Z50-65.1 X 2,910,377 10/ 1959 Owen 250-65.1 X 2,939,009 5/ 1960 Tien 101-426 X 2,954,311 9/ 1960 Vander Weel lOl- 149.4 X y3,060,023 10/-1962 Burg et al -101-149.4 X 3,063,863 lil/1962 Holland et al. Z-65.1 X 3,109,748 11/ 1963 Newman Z50-65.1 X 3,121,650 2/'1964 Meissner lOl-426 X '3,122,997 3/ 1964 Raczynski et al. Z50-'65:1 X 3,129,661 4/1964 Newman Z50-65.1 3,147,377 9/1964 INewman Z50-65.1

FOREIGN PATENTS 722,023 1/ 1955 Great Britain.

ROBERT E. RULFREY, Primary Examiner. DAVID KLEIN, Examiner. B. A. LEIGHEY, lE. T. WRIGHT, Assistant Examiners.

Claims (1)

1. THE METHOD OF PREPARING A REPRODUCTION OF A DIFFERENTIALLY RADIATION-ABSORPTIVE GRAPHIC ORIGINAL, COMPRISING: SUBJECTING A HEAT-SENSITIVE COPY-SHEET TO LOCALIZED HEATING AT AREAS CORRESPONDING TO IMAGE-FORMING AREAS OF SAID ORIGINAL BY A THERMOGRAPHIC PROCESS TO PROVIDE A VISIBLE REPRODUCTION OF SAID IMAGE-FORMING AREAS, SAID COPY-SHEET INCLUDING A VISIBLY HEAT-SENSITIVE COATING ON A FLEXIBLE CARRIER; PLACING SAID COPY-SHEET WITH ITS COATED SURFACE IN PRESSURE-CONTACT WITH THE HEAT-ACTIVATIBLE SURFACE OF A NORMALLY NON-TACKY ADHESIVE RECEPTOR SHEET AND HEATING AT LEAST THE PORTIONS OF SAID HEAT-ACTIVATIBLE SUR-

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