US3505955A - Method and arrangement for producing printing forms - Google Patents

Description

'2 Sheets-Sheet 1 Fig.7

G. RITZERFELD 2 .74 m\ m m METHOD AND ARRANGEMENTFOR PRODUCING PRINTING FORMS mmmm &

April 14, 1970 Filed Jan. 10. 1967 8 m 3' 11 3 m m .H\s m W. m 7 m Inventor: -vrfardl dwl-ed April 14, 1970 G. RITZEIDQFELEY) 3,505,955

METHOD AND ARRANGEMENT FOR PRODUCING PRINTING FORMS Filed Jan. 10, 1967 1 3 Sheets-Sheet 2 Inventor-- G-arfiard fu ler-[ 1 United States Patent "ice Int. Cl. B4 1m 5/00 U.S. Cl. 101-463 13 Claims ABSTRACT OF THE DISCLOSURE By forming a pressure imprint on one face of a printing form backing sheet while the other face of the backing sheet contacts a pressure sensitive transfer layer including a heat radiation absorbing material, a portion of the transfer layer corresponding to a mirror image of the imprint will be attached to the other face of the backing sheet. The mirror image-carrying face of the backing sheet is then contacted with a transfer layer including a transferable dye. The thus formed assembly is then subjected to heat radiation directed against the imprinted face of the backing sheet so as to selectively heat the mirror image forming portions on the other face thereof and the corresponding contacting portions of the dye-containing transfer sheet to at least their softening points thereby adhering the heated mirror image-forming portions of the dyecontaining transfer sheet to the backing sheet and producing a printing form comprising the backing sheet, mirror image-forming portions of the transferable dyecontaining transfer layer, and interposed corresponding portions of the heat radiation absorbing material containing layer.

BACKGROUND OF THE INVENTION The present invention is concerned with a method and an arrangement for producing printing forms of the type comprising a mirror image of the indicia which are to be printed, which mirror image includes a transferable dye which, for instance, may be transferred to a copy sheet upon being moistened with an alcoholic liquid.

The printing form of the present invention thus is used primarily in connection with sprit duplicating devices, for instance as a hectographic master sheet Generally, sprit duplicating devices and methods utilize triphenylmethane dye stuffs which-even though they are generally embedded in a binding material-due to their high degree of solubility in alcohol or water tend to soil the hands of the operator as well as the typewriter or the like which is used to imprint the reproducible master sheet. A particularly high degree of soiling is experienced when it is necessary to carry out erasures whereby particles of the dye will become located in the typewriter and on the clothing and hands of the typist.

Even if printing devices such as high-speed printers are used, the soiling which is connected with the employment of hectographic dye sheets in the production of the printing form causes great difficulties and disadvantages.

It has been proposed to apply a protective layer to the free face of the color transfer sheet, however, these suggestions have met only with a limited success, inasmuch as such protective layers in practical operation do not absolutely guarantee complete covering of the dye-containing transfer layer and, furthermore, inasmuch as the protective layer has to be broken up during forming of the indicia on the master or printing form. It is a further disadvantage, that according to these conventional methods the color or ink transfer sheet must be separated from 3,505,955 Patented Apr. 14, 1970 the printing form while still located in the typewriter or the like, particularly if erasures are to be carried out. In such case, the protective layer will be interposed between the base sheet of the printing form and the relatively heavy layer containing the transferable dye, the latter being exposed, so that upon handling of the printing form or upon removal of the ink transfer sheet the risk of soiling is again very considerable. This is particularly so during the warm season and in the case of electric typewriters and teletypes which are warmed by the operation of the electric motor connected therewith.

It is an object of the present invention to overcome the above discussed difiiculties and disadvantages.

It has been proposed to overcome these problems by producing the printing forms by thermographic processes. However, several serious disadvanges are connected therewith which greatly reduce the practical applicability of thermographic processes for the preparation of printing forms of the type described. Thus, when it was desired to produce printing forms of conventional thickness, i.e., printing forms including a backing sheet weighing between about -100 g1"./m. it was necessary to use carbons which consisted of a transparent paper on which indicia has been formed by means of a thermographic color ribbon or a pigment dye. In order to achieve good results it was necessary to use an extraordinarily thin transparent paper, weighing for instance 60 gr./m. as compared with the conventional transparent paper weighing about 80 gr./m.

For obvious reasons, the use of such very thin transparent paper was disliked and accepted only by a small number of consumers. Furthermore, the last discussed method is connected with the disadvantage that the mirror image masters formed thereby did not contain a legible right side right image of the indicia on their non-printing face, so that mix-ups of the printing forms frequently could not be avoided.

For producing the printing form by reflex, the backing sheets of the printing forms had to be very thin, so as to have a maximum weight of between about 30-35 gr./m. since the printing forms had to be placed opposite the source of radiation, and the radiation had to pass through the printing form and the color or ink transfer sheet to the heat reflecting original. Printing forms with such very thin backing sheets are impractical in most cases because of their low resistance to creasing in the duplicating device and because of the difficulties involved in filing and storing the same.

Another method has been proposed according to which an original was imprinted or written on at its front face by means of a thermographic color ribbon. In this case, the printing form had to carry at its rear face a latently adhesive layer which could be activated by exposure to heat. This layer consisted of waxes and resins and was free of pigment constituents. In order to thermographically convert this form into a hectographic mirror image-carrying printing form, radiation had to be applied in such a manner as to impinge first at the front face of the printing form and consequently it was necessary to use printing forms having a relatively thin backing sheet weighing about 4050 gr./m so that the selective heating produced at the front face could pass through the backing sheet into the contacting hectographic ink transfer sheet.

Furthermore, due to the necessity of heating through the backing sheet of the printing form, this method frequently has been found unreliable. In addition, generally printing forms including such thin backing sheets are disliked particularly because erasures are practically impossible thereon. The dye stuff transferred from the thermographic color ribbon onto the backing sheet had to be completely removed by erasing and in the case of such thin backing sheets this frequently led to the forming of holes either during erasing or during subsequent imprinting.

Furthermore, very thin backing sheets tend to cause the formation of a relief image which again gives rise to difiiculties in the formation of the reproducible mirror image.

SUMMARY OF THE INVENTION The present invention proposes a method of preparing printing forms adapted for use in a sprit duplicator and the like by forming a multi-layer structure including, in the indicated sequence, a first backing sheet, a first transfer layer adhering to the first backing sheet and consisting essentially of a transfer material having a predetermined relatively low softening point, being free of transferable dye stuffs and having incorporated therein and substantially evenly distributed therethrough a heat radiation absorbing material, and a second backing sheet having a free face and another face, the latter contacting the first transfer layer, exerting pressure against the free face of the second backing sheet so as to adhere corresponding portions of the first transfer layer to the other face of the second backing sheet, the transferred portions forming on the other face of the second backing sheet a mirror image of the pressure-exposed portions of the free face of the second backing sheet, separating the second backing sheet with the mirror image-forming portions of the first transfer layer thereon from the multi-layer structure, contacting the separated second backing sheet with a second transfer layer consisting essentially of a transfer material having a predetermined relatively low softening point and having a transferable dye distributed therethrough, so that the mirror imageforming portions of the first transfer layer are in contact with the second transfer layer, exposing the free face of the second backing sheet to heat radiation so as to heat the heat radiation absorbing material of the mirror image-forming portions of the first transfer layer and thereby to selectively heat corresponding contacting portions of the second transfer layer to at least the temperature of the predetermined relatively low softening points of the transfer layers so as to soften the contacting portions of the first and second transfer layers and to adhere to contacting portions of the second transfer layer to the first transfer layer and thus to the second backing sheet, and separating the second backing sheet from the residual portion of the second transfer sheet, thereby forming a printing form consisting essentially of the second backing sheet, the mirror image-forming portions of the second, transferable dye-containing second transfer layer, and the mirror image-forming portions of the first transfer layer interposed between and adhering to the second backing sheet and the transferable dye-containing mirror image-forming portions of the second transfer sheet.

The present invention also encompasses arrangements and transfer sheets as described above.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The eight figures of the drawing schematically illustrate various multi-layer arrangements which are utilized in accordance with the present invention.

FIG.1 illustrates the imprinting of the prospective printing form, i.e., of the backing sheet thereof with an underposed carbon paper;

FIG. 2 illustrates the arrangement of FIG. 1 after imprinting;

FIG. 3 illustrates the arrangement of a backing sheet processed as illustrated in FIGS. 1 and 2 and superposed upon a color transfer sheet;

FIG. 4 illustrates the printing form and the color transfer sheet as they appear after transfer of selected portions of the color transfer sheet to the printing form in accordance with FIG. 3;

FIG. 5 substantially corresponds to FIG. 1, however, illustrates the imprinting with the interposition of a color ribbon between the indicia-forming, pressure-exerting member and the backing sheet of the prospective printing form.

FIG. 6 corresponds to FIG. 5 in the same manner as FIG. 2 corresponds to FIG. 1;

FIG. 7 illustrates the forming of reproducible mirror image indicia under utilization of a color transfer sheet, the color transfer layer of which is protected by a protective layer; and

FIG. 8 illustrates the printing form and the color transfer sheet after adhering selected portions of the protective layer and of the color transfer layer to the printing form as illustrated in FIG. 7.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawing, and particularly to FIG. 1, it will be seen that a backing sheet 3 of the printing form is used for producing a latent printing form to which the printing ink or the like is not applied during imprinting of the printing form but subsequent thereto, for instance shortly prior to making copies of the printing form in a sprit duplicator or the like.

Element 1 represents a typewriter key, but might also be replaced by a pencil, stylus or the like for imprinting one face of the backing sheet 3 of the printing form with indicia 2, the transferable mirror image of which is to be formed at the opposite face of backing sheet 3. Backing sheet 3 preferably will be a casein coated high gloss paper. Imprinting, for instance with a typewriter, may be carried out with or without interposition of a color ribbon.

During the imprinting, backing sheet 3 is superposed and in contact with carbon paper 11 comprising transferable carbon dye layer 5 and paper backing 12. Upon imprinting, portions of carbon layer 5 which correspond to the indicia formed at the upper free face of backing sheet 3 will be attached to the opposite, lower face of the backing sheet 3.

Carbon paper 11 may be replaced with another transfer sheet including a transfer layer 5, provided that the transfer layer includes heat radiation absorbing material, preferably a particulate material such as pigments evenly distributed throughout layer 5, so that upon exposure to heat radiation the pigments or the like will be heated to a relatively high temperature.

FIG. 2 illustrates the backing sheet 3 of the printing form and carbon or the like paper 11 after imprinting and separation. It will be seen that due to the pressure exerted by typewriter key 1 during formation of indicia 2 at the upper face of backing sheet 3, corresponding portions 4 of transferable carbon black or pigment-containing layer 5 will have been separated from transfer sheet 11 and attached to the lower face of backing sheet 3 forming thereon a mirror image of indicia 2. The residual portions of transfer layer 5, i.e., the portions thereof which were not exposed to pressure, are retained in contact with backing sheet 12 of transfer sheet 11.

As shown in FIG 3, the thus formed latent printing form including backing sheet 3 and mirror image forming, heat radiation abosrbing portions 4 is then superposed upon an ink transfer sheet 13 comprising a backing sheet 6 and an ink or dye transfer layer 7, the latter being in contact with the face of backing sheet 3 which carries mirror image portions 4.

It is frequently desirable in connection with the method of the present invention, that the ink transfer layer 7 includes an aniline dye.

By applying heat radiation, for instance from a source 8 so that the heat radiation impinges on the free face of backing sheet 6 of the ink transfer sheet, the mirror image-forming portions on the lower face of the printing form backing sheet, which portions include the heat radiation absorbing material, will be sufficiently heated to at least soften or even melt corresponding portions of ink transfer layer 7 so that these corresponding portions will be adhered to the mirror image forming portions 4 and, upon separation of the ink transfer sheet from the printing form, Will adhere to the printing form, as illustrated in FIG. 4, forming thereon a transferable mirror image of indicia 2.

FIG. 4 shows the completed printing form after cooling and separation from ink transfer sheet 13. It will be seen that layer portions 7a of ink transfer layer 7 are now attached to the mirror image forming carbon or pigment containing portions at the printing face of backing sheet 3 of the printing form, whereas ink transfer layer portions 7b, which had not been heated due to the fact that they were not juxtaposed to heat radiation absorbing material, remain adhered to backing sheet 6 of ink transfer sheet 13.

According to the embodiment illustrated in FIG. 5, a color ribbon is interposed between typewriter key 1 and backing sheet 3 so that the indicia 2 are formed by pressure transfer from the typewriter ribbon 10 to the face of backing sheet 3.

Simultaneously a mirror image of indicia 2 is formed on the opposite face of backing sheet 3 by pressure transfer of corresponding portions of the pigment or carbon black-containing transfer layer of transfer sheet 11. Backing sheet 12 of transfer sheet 11 as well as the other backing sheets described herein, may consist for instance of paper or of a synthetic material.

FIG. 6 illustrates the latent printing form produced according to FIG. 5, after separation from transfer sheet 11.

As illustrated in FIG. 7, the latent printing form shown in FIG. 6, which on its upper face carries legible indicia 2 and on its lower face mirror images 4 of indicia 2, which mirror images consist of transfer layer material which has incorporated therein heat radiation absorbing material, is placed on an ink transfer sheet 13 which comprises an ink transfer layer 7 adhering to a backing sheet 6 and being protected at its free face by a protective layer 9. The protective layer '9 contacts the mirror image portions carrying face of backing sheet 3.

By applying heat radiation as schematically illustrated at 8, the heat radiation absorbing material of mirror image portions 4 will be sufiiciently heated to soften or melt corresponding portions of adjacent protective and ink transfer layers 9 and 7 so that, upon cooling and separation of the thus produced printing form from the ink transfer sheet, the mirror image forming portions of the ink transfer sheet will adhere, with interposition of corresponding portions of the protective layer, to the mirror image-forming portions of the heat radiation absorbing material, and thus to backing sheet 3. In contrast thereto, the portions 911 and 7b of the protective layer and of the ink transfer layer which were not juxtaposed to the mirror image portions 4 andthus were not heated to their softening point will remain attached to backing sheet 6 of ink transfer sheet 13.

Preferably, according to the present invention, backing sheet 3 of the printing form will consist of paper, synthetic material or the like and will have a thickness corresponding to a weight of at least about 60 gr./m.

Transfer layer 5 which includes the heat radiation a-bsorbing material such as carbon black or pigments will act as a binder material and preferably will melt or at least substantially soften at a temperature below- C.

' Layer 5 does not contain transferabledye stuffs.

After imprinting the backing sheet 3 while in contact with transfer sheet 11 as illustrated in FIGS. 1 and 5, in conventional manner by means of a pencil, stylus, typewriter, high-speed printer, or the like, and after subsequent separation of the imprinted backing sheet 3 from transfer sheet 11, a latent printing form is obtained which carries legible indicia on one face and a mirror image of these indicia consisting of a transfer material of relatively low softening point, being substantially free of transferable dye stuffs and having incorporated therein and substantially evenly distributed therethrough a heat radiation absorbing material, on its other face. A second transfer sheet which is an ink transfer sheet including a transfer layer containing transferable ink or the like is then placed against the mirror image-carrying face of backing sheet 3. The ink transfer layer of transfer sheet 13 consists essentially of a transferable binder material having a melting point which is also below about 100 C. and having incorporated therein a dye stuff which, for instance, is soluble in alcoholic liquids. As described in connection with the drawing, a protective transferable layer which also has a melting point of below 100 C. or the like may be superposed upon the transferable ink layer.

Upon applying heat radiation in per se conventional manner against the free face of the backing sheet of ink transfer layer 13, the printing form may be formed as illustrated in FIGS. 3 and 4 and 7 and 8 respectively. It is sometimes preferred to interpose between the free face of ink transfer sheet 13 and the source 8 of heat radiation a radiation diffusing material, for instance a polyester gauze, in order to obtain substantially uniform distribution of the heat radiation, for instance infrared radiation.

It is achieved by proceeding in accordance with the present invention that sharp edged portions of transfer layers 5 and 7, or 9 and 7, conforming to the outline of indicia 2, are. transferred from the respective transfer sheets to the backing sheet of the printing form.

Infrared radiation may also be replaced, for instance, by exposure to electric high frequency radiation.

In connection with the present invention, it is possible to use as backing sheets for the printing form paper sheets or sheets of synthetic material of considerable thickness, such as sheets having a weight of between 60- gr./m. and preferably a weight of between 80-110 gr./m.

The backing sheets of the transfer sheets may be of lesser thickness and weight. Thus, for instance, it is preferred to use a backing sheet 12 of transfer sheet 11, i.e., the transfer sheet including a transfer layer with heat radiation absorbing material, a sheet of paper or synthetic material having a weight of between about 20-40 gr./m.

It is a particular advantage of the present invention, that after producing a considerable number of copies from the printing form produced according to the present invention and thereby more or less completely exhausting the mirror image forming transferable dye-containing portions thereof, the printing form can be easily reactivated by forming thereon new mirror image portions 7a, by again proceeding as illustrated in FIGS. 3-4 and FIGS. 7-8 respectively.

Inother words, after substantial exhaustion of the transferable ink of the mirror image forming portions 70, there will still remain-on the printing form the mirror image portions 4 which, while not transferable, contain the heat radiation absorbing material, so that by proceeding as described in connection with for instance FIGS. 3 and 4, additional transferable ink-containing material may be adhered to the mirror image forming portions 4.

Transfer compositions which upon exposure to pressure or heat may be transferred from a transfer sheet to a take-up sheet are, per se, well known in the art as well as compositions thereof, which will have any desirable melting point, i.e., in accordance with the present invention, preferably will melt or at least be substantially softened at temperatures below 100 C.

The following examples of transfer layers are therefore given as illustrative only, without, however, limiting the invention to the specific details of the examples.

EXAMPLE 1 Transfer layer may be of the following composition:

Carnauba wax 1000 Petroleum jelly 1500 Mineral oil 1000 Carbon black 350 Barium sulfate 12000 EXAMPLE 2 The composition described in Example 1 may be replaced by the following composition:

Carnauba wax 1000 Petroleum jelly 1500 Mineral oil 1000 Prussian blue 15000 EXAMPLE 3 The transfer layer 7 which includes the transferable dye EXAMPLE 4- A protective transfer layer such as layer 9 may be composed as follows:

Montan wax 1000 Parafiin 500 Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A method of preparing printing forms adapted for use in a sprit duplicator and the like, comprising the steps of forming a multi-layer structure including, in the indicated sequence, a first backing sheet, a first transfer layer adhering to said first backing sheet and consisting essentially of a transfer material having a predetermined relatively low softening point, being free of transferable dyestuffs and having incorporated therein and substantially evenly distributed therethrough a heat radiation absorbing material, and a second backing sheet having a free face and another face, the latter contacting said first transfer layer; exerting pressure against said free face of said second backing sheet so as to adhere corresponding portions of said first transfer layer to said other face of said second backing sheet, said transferred portions fom'iing on said other face of said second backing sheet a mirror image of the pressure-exposed portions of said free face of said second backing sheet; separating said second backing sheet with said mirror image forming portions of said first transfer layer thereon from said multi-layer structure; contacting said separated second backing sheet with a second transfer layer consisting essentially of a transfer material having a predetermined relatively low softening point and having a transferable dye distributed therethrough, so that said mirror imageforming portions of said first transfer layer are in contact with said second transfer layer; exposing said free face of said second backing sheet to heat radiation so as to heat the heat radiation absorbing material of said mirror image-forming portions of said first transfer layer and thereby to selectively heat corresponding contacting portions of said second transfer layer to at least the temperature of said predetermined relatively low softening points of said transfer layers so as to soften said contacting portions of said first and second transfer layers and to adhere the contacting portions of said second transfer layer to said first transfer layer and thus to said second backing sheet; and separating said second backing sheet from the residual portion of said second transfer sheet, thereby forming a printing form consisting essentially of said second backing sheet, said mirror image-forming portions of said transferable dye-containing second transfer layer, and said mirror image-forming portions of said first transfer layer interposed between and adhering to said second backing sheet and said transferable dye-containing mirror image-forming portions of said second transfer layer.

2. A method as defined in claim 1, wherein said predetermined relatively low softening points are below 100 C., said heat radiation absorbing material consists of discrete particles, and pressure is exerted against the free face of said second backing sheet by printing or writing thereon.

3. A method as defined in claim 2, wherein said second backing sheet consists of paper or synthetic material and has a thickness corresponding to a weight of between about 60 and 160 gr./m.

4. A method as defined in claim 3, wherein the thickness of said second backing sheet corresponds to a weight of between about and 110 gr./m.

5. A method as defined in claim 3, wherein said second transfer layer is covered by a protective, substantially transferable dye-free layer of transfer material having a softening point below C., so that in the completed printing form portions of said protective transfer material will be interposed between the mirror imageforming portions of said first and second transfer layers.

'6. A method as defined in claim 2, wherein said first transfer layer is interposed between said first backing sheet and a protective layer adhering to said first transfer layer, said protective layer being substantially free of transferable dye-stuffs and improving upon said extertion of pressure by its interposition adherence of portions of said first transfer layer to said second backing sheet.

7. A method as defined in claim 2, wherein said first backing sheet consists of paper or synthetic material and has a thickness corresponding to a weight of between about 20 and 40 gr./m.

8. A method as defined in claim 2, wherein said second transfer layer includes an alcohol-soluble transferable dye and is supported by a third backing sheet having a thickness corresponding to a Weight of between about 20 and 40 gr./m.

9. A method as defined in claim 8, wherein said transferable dye is a triphenylmethane dye.

10. A method as defined in claim 1, wherein a layer of diffusing material is interposed between said free face of said second backing sheet and the source of said heat radiation during exposure of said free face to said heat radiation.

11. A method as defined in claim 10, wherein said diffusing layer consists essentially of a polyester gauze.

12. A method as defined in claim 1, and including the steps of making copies of said printing form until the transferable dye containing mirror-image forming portions therethrough, so that said mirror image-forming portions of said first transfer layer are in contact with said second transfer layer; exposing said free face of said second backing sheet to heat radiation so as to heat the heat radiation absorbing material of said mirror image-form ing portions of said first transfer layer and thereby to selectively heat corresponding contacting portions of :said second transfer layer to at least the temperature of said predetermined relatively low softening points of gsaid transfer layers so as to soften said contacting portions of said first and second transfer layers and to adhere the contacting portions of said second transfer layer to said first transfer layer and thus to said second backing sheet; and separating said second backing sheet from theresidual portion of said second transfer sheet, thereby reactivating said printing form. 13. An arrangement for use in producing a printing form, said arrangement comprising a first backing sheet carrying on one face thereof a mirror image of indicia to be printed, said mirror image being formed of a transfer material having a softening point below 100 C., being free of transferable dye stuffs and having incorporated therein and substantially evently distributed therethrough discrete particles of a heat radiation absorbing material; and a transfer sheet comprising a second backing sheet and a transfer layer on one face thereof, said transfer layer consisting essentially of a material having a softening point below C. and having a transferable dye distributed therethrough, said transfer layer cfontacting the mirror image indicia carrying face of said first backing sheet.

References Cited UNITED STATES PATENTS 2,777,781 1/ 1957 Kordig et al. 11792 2,898,852 8/1959 Staehle et a1 101-472 3,031,327 4/1962 Newman 117-92 3,129,661 4/ 1964 Newman 101-472 3,151,550 10/1964 Newman 101-473 3,170,809 2/ 1965 Barbour 117-36.3 3,226,134 12/1965 Breidthardt 117 36.4 3,342,623 9/ 1967 Dulmage et al. 101-467 3,087,832 4/1963 Fogle 11736.4 3,122,997 3/1964 Racnynski et al. 101-471 3,384,015 5/1968 Newman 101-470 FOREIGN PATENTS 693,721 9/ 1964 Canada.

ROBERT E. PULFR'EY, Primary Examiner C. D. CROWDER, Assistant Examiner US. Cl. X.R.

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