US 3243312 A
Description (OCR text may contain errors)
March 29, 1966 w. sci-'IUTZNER ETAL 3,
DIRECT-TRANSFER COPY SHEET Filed 001;. 8, 1962 COLORACCEPTOR LAYERS (WAX+ METAL SOAP) COLOR-TRANSFER LAYERS FRA/va Mock MLTER ScHJTzA/EP.
BY 5 ml TD AGENTI Patented Mar. 29, 19%6 3,243,312 DIRECT-TRANSFER COPY SHEET Walter Schiitzner and Franz Mock, Vienna, Austria, as-
signors to W. Koreska, Vienna, Austria, a corporation of Austria Filed Oct. 8, 1962, Ser. No. 229,235 Claims priority, application Austria, Oct. 11, 1961, A 7,624/61; Oct. 12, 1961, A 7,693/61; Jan. 31, 1952, A 809/62; Feb. 1, 1962, A 850/62 2 Claims. (Cl. 1l7--36.3)
The present invention relates to direct-transfer copying material and, more particularly, to copying paper whereby single or multiple copies may be made without interposition of separate sheets of color-transfer paper between the original and the copy sheets.
Heretofore, to produce handor machine-written copies of an original, one had to dispose between the original and the copy a sheet or sheets of carbon or colortransfer paper of Well-known types. Upon completion of the original, the carbon or color-transfer papers were removed in a time-consuming and inconvenient manner. Furthermore, the use of such copying materials resulted in soiling of the hands and, especially if care was not taken, in a smudging of the copy-receiving sheets. This method was unsatisfactory for use with preprinted forms and other sheets which were to be filled in at a later date. Such forms have been provided, hitherto, with a colortransfer layer on their rear side and were preprinted on their front side with any required text. On juxtaposition of a form carrying a carbon layer upon the printed surface of an underlying preprinted face, the coloring matter was frequently transferred to the latter face to soil same.
It has been proposed, in order to avoid the aforementioned disadvantages, to provide the color-transfer layer with a colorless protective coating. Such efforts were not highly successful since the color layer was, in any case, designed to reproduce any pressures applied to its carrier sheet so that underlying sheets received color to a noticeable degree even in the absence of such pressures while the mere writing by pencil upon the sheet immediately produced a copy even if such was not desired.
To avoid these disadvantages it has been suggested that one provide the reverse side of a substrate with a colortransfer layer in which the coloring material is held so tenaciously that transfer to normal paper is impossible. However, when this layer is disposed in contact with a wax layer provided upon a copy-receiving sheet, color transfer takes place readily upon the application of writing pressure. Color-transfer layers of this kind invariably impart copy to underlying sheets even if the same have not been specifically designed to accept the copy. The color-transfer layer frequently contains some wax so that simultaneous transfer of wax and coloring matter to an underlying sheet was also possible. In other modifications of this technique the color-transfer layer of the upper sheet was substantially wax-free while the juxtaposed surface of the copy-receiving sheet contained a color-acceptor wax layer. In this case the color-transfer layer generally contained alcohol-base or benzene-base coloring materials or size colors with insoluble coloring material.
All of these prior-art copying materials were commercially unsuccessful since non-uniformity and inconsistency in their manufacture rendered them unsuitable for general purposes.
It is an object of the present invention to provide directtransfer copying materials adapted to obviate the aforementioned disadvantages and to yield sharp uniform copy without the use of a carbon paper interposed between the original and the copy-receiving sheets.
This object is achieved, in accordance with the invention, by providing a direct-transfer copying sheet whose rear side is formed with a color-transfer layer wherein the coloring material is held so tightly that transfer to ordinary (i.e. non-wax-coated) sheets is avoided but which readily gives up such coloring material to a coloracceptor layer carried upon the upper surface of an underlying copy-receiving sheet. The color-acceptor layer generally comprises a wax or waxy material to which the coloring agent can be transferred to produce a sharp copy which is of a color contrasting with that of the copyreceiving sheet and which is smudge-resistant.
It is a more specific feature of the invention to render the color-acceptor layer of the color-receiving sheet compatible with ink (e.g. printing inks, fountain-pen inks and ballpoint-pen inks) so that ordinary writing is possible upon the upper surface of these sheets.
It is important that the color-transfer layer be nonsoiling to the hands and capable of producing sharply defined, high-contrast copy and, to this end, the colortransfer layer according to the invention may be provided with a binder consisting of one or more synthetic resins and one or more waxes or wax-like substances. In contrast to prior-art techniques in which the coloring agent and the wax substance are provided upon separate surfaces, the present invention derives from the discovery that the color-transfer layer is bonded more securely and is more capable of producing clear copy when the coloring agent is bound by a synthetic resin containing significant quantities of wax or wax-like substances. A color-transfer layer wherein the coloring agent is bonded by a synthetic resin has been found to be too hard for the purposes described since it does not permit transfer of the color even to prepared underlying sheets. By compounding the wax or wax-like substances, which hereinafter are generally referred to as a wax but should be considered to include one or more waxes and waxlike substances or mixtures thereof, one obtains ready transfer of the coloring agent to wax-treated underlying surfaces and sharply defined images. Synthetic resins of this type include polystyrenes and polyvinyl compounds (e.g. polyvinyl acetates) while the wax may be a stearin or montan wax compounded therewith.
According to another aspect of the invention the colortransfer layer is provided with a binder (eg. a cellulosic derivative such as ethylcellulose) to which the coloring agent is added. The binder and the admixed coloring agent are then combined with a mixture of a solvent for the synthetic resin and a liquid medium, advantageously compatible with the solvent, in which the synthetic resin is insoluble. The solvent for the cellulosic derivative is, according to the invention, substantially more volatile than the liquid medium (i.e. has a lower boiling point). Such a mixture is, for example, a blend of acetone and water wherein the alcetone acts as a volatile solvent for, say, ethylcellulose while the water serves 'as the higherboiling liquid medium. Upon deposition of the color mass on the paper strip from the solvent and liquid deposition medium therefor, the color layer is dried. Since the solvent for the cellulosic derivative is more volatile than the liquid vehicle, it evaporates earlier so that, upon drying, an increase in the concentration of the liquid vehicle results. This effects an at least partial precipitation of the synthetic resin and results in a substantially white deposition which constitutes the color layer. This white appearance or blush coat is believed to be a consequence of the fineness of the precipitated particles constituting the color layer. It is also possible to acco plish the same effect without the addition of a liquid medium to the original mixture if such liquid medium is provided from the drying environment. Thus, for example, one may dissolve the ethylcellulose in acetone and deposit the resulting solution, admixed with a suitable quantity of pigment, upon the substrate, thereby precipitating fine particles of the synthetic resin with the aid of humid air. The air, when necessary, has added thereto, in the form of steam, the necessary water content.
This method of preparing copying material has two advantages:
(1) The precipitation of the synthetic resin results in a loosening of the binder to render the color agent more readily transferable to the copy-receiving sheet, and
(2) The normally dark-colored layer is lightened as a consequence of the gene-rally white-appearing precipitation of the synthetic resin. The resulting paper is substantially more aesthetic since the color-transfer layer is hardly noticeable, because the clean and uniform colortransfer layer does not impart to the upper surface of the sheet the dirty grey color characterizing earlier-known copying materials having dark-black color-transfer layers.
The color-transfer layer is transferred, upon the application of writing pressure, to the copy-receiving sheet and produces copy as direct as that resulting from earlier techniques. The basis for this surprising effect is found in the fact that the cellulosic derivative is in the form of small finely divided particles in a somewhat dispersed state which, upon application of writing pressure, are densified and transferred to the copy-receiving sheet in the form of large transparent particles in which the dark color of the coloring agent stands out clearly. In addition vto the cellulosic synthetic resins, we have found that other synthetic resins such as chlorinated polyvinyl chlorides can 'be deposited in the manner set forth. Thus, trichloroethylene and gasoline may serve as the solvent and liquid vehicle previously described. The resulting copying material has a color-transfer layer which is sufliciently hard that undesired transfer of color does not take place and paper and hands are unsoiled while color transfer to prepared surfaces results in clear sharply defined copy.
Another feature of the present invention resides in the fact that the pigment proportion of the color transfer layer can be raised above that characterizing earlier copying materials. Nevertheless, a clean-looking colortransfer layer results.
When the pigment content of the color-transfer layer is increased, however, it occasionally becomes too dark and is no longer smudge-free.
It is another feature of the present invention to provide means for improving the appearance of the layer. Such means may take the form of non-coloring pigments or fillers which have an appearance contrasting with that of the eolor-transfer pigment but do not impart any color to the copy-receiving sheets. Thus optimal clear layers can result. When black pigments are employed, whitecolored additives may be provided which either strongly or weakly mask the color-transfer pigment. Among the strongly masking pigments are titanium dioxide and zinc oxide while kaolin or chalk may serve for weakly masking the color-transfer pigment. In each case the quantity of the different pigments is so chosen that the (total quantity of coloring pigment and contrasting pigment provides the optimal number of seed particles for the most effective precipitation of the cellulosic derivative. It is indeed surprising that, unexpectedly, the addition of, say, a white pigment to the color-transfer layer nevertheless permits high-intensity dark copy. In spite of the fact that one might believe that the addition of such white pigment would result in a reduction in the coloring power of the coloring pigment to produce grey and faded copies, this has been found not to betrue.
According to one embodiment of the invention, sufficient color pigment is provided to yield clean copies with high color intensity and to this is added a lesser quantity of a weak masking pigment (e.g. kaolin) to provide the required number of seed particles.
Another possibility resides in an admixture of the color pigment and a strong masking pigment (e.g. titanium white) in which case the quantity of color pigment is somewhat higher than in the ab-ove mentioned case, since the masking pigment does, to a limited extent, reduce the effectiveness of the color pigment.
The upper surface of the copying sheet is, according to prior-art techniques, provided with a fine coating of wax, stearin, parafiin or the like. Earlier-known copying materials had, however, the disadvantage that ordinary writing (e.g. with ballpoint or fountain pens) upon them was impossible and printing inks were likewise incompatible with this layer. We have discovered that the primary reason why printing of these wax-coated sheets was impossible was that the wax-layer prevented penetration of the printing ink into the paper. When, however, according to the invention, metal soaps are added to the wax layer, which serve as drying agents, they facilitate printing upon such copy papers. It has also been found that metal soaps likewise serve to facilitate the writing upon the sheets with the aid of ballpoint pens.
The effect of the metal soaps, which render the copyreceiving layer receptive to ballpoint-pen inks, is not only difiicult to explain but also completely unexpected. One would normally expect that a long-chain aliphatic or wax soap-containing layer cannot be written on with ballpoint pens since the inks thereof are oil-containing. In fact, Austrian Patent No. 181,600 points out the oleophobic character of such metal soaps. In spite of the oleophobic nature of these soaps we have discovered that addition thereof to the color-receiving layer enables them to accept ballpoint-pen inks. It is also possible to increase the ballpoint-pen writability on such sheets through the use of various pigments (e.g. silicic pigments).
To render the copy-receiving layer receptive to other types of inks, which heretofore have merely formed a slow-drying chain of droplets on wax-treated surfaces, we provide the wax layer with means for increasing the adhesion forces between such inks and the wax-treated surface. To this end we add to the waxy layer surfaceactive agents for altering the surface tensions of writing inks deposited thereon to increase the adhesion to the extent that the adhesion force between the writing ink and the layer is greater than the surface tension of the ink. This makes it possible for the ink to wet the layer and to exist in continuous strips of substantially constant width, as is usually desired.
Among the surface-active agents found suitable for this purpose are the water-soluble metal soaps (cg. sodium stearates), alkyl-aryl sulfonates, fatty-alcohol sulfonates and nonionic surfactants such as polyglycols, their ethers and their esters.
The above and other objects, features and advantages of the present invention will become more readily apparent from the following specific description and examples, reference being made to the accompanying drawing in which:
FIG. 1 is a cross-sectional view of a sheet of copy paper according to the invention disproptionately enlarged to illustrate the coatings thereon; and
FIG. 2 is a diagrammatic view showing apparatus for applying the coatings.
In FIG. 1 is shown a first sheet of direct-transfer copy paper 10 comprising a substrate 11 of paper or other flexible material which is coated on its lower surface with a pigmentary layer 12 consisting of a binder and pigment particles 13 which are dispersed in the binder. On the upper surface of the substrate 11 there is provided a coating 14 of a release agent. The waxy color-accepting agent 24 of a sheet 20 disposed below sheet 10 is compatible with and readily receives the pigmented material of coating 12 carried on the underside of sheet 10. Application of pressure (e.g. by a typewriter or manual writing implement) to the upper surface of sheet 10 will result in a transfer of pigmentary matter from coating 1:2 to the upper surface of sheet 20. The pigmentedmaterial adheres readily to this wax-coated surface and reproduces the impression made upon sheet Sheet is provided with a pigmentary layer 22 for transferring this impression to still another wax-coated sheet. Use of a non-wax-coated sheet below the pigmentary layer will not result in any substantial transfer of pigment at ordinary pressures since the untreated surface is not receptive to the pigment.
The apparatus for applying the coatings to the substrates is illustrated in FIG. 2. Thus, the paper or other flexible substrate 31 may be unwound from a supply roll and passed through. a first station wherein the pigmentary coating is applied via a spray nozzle 32 and a doctor blade 33. A blower 34 forwardly of this blade dries the layer whereupon the substrate passes to a further coating station wherein its opposite surface is provided with a layer of a release agent. The molten colorreceiving agent is cast from the melt by a coating device 35 and distributed by a doctor blade 36 disposed rearwardly of a blower 37 which solidifies this layer. The paper then may be severed into sheets by a reciprocating blade 38 in the usual manner.
Example I A mixture consisting by weight of 4% polystyrene, 5% stearin, 10% carbon-black color-transfer pigment and 81% trichloroethylene solvent is deposited upon a fiat flexible substrate (e.g. paper) and dried to produce a deposit of about 56 grams/m. The sheet is also provided, on its upper surface, with a wax layer (5 grams/m?) of ozocerite which is deposited thereon from a melt and has a softening point of about 75 C. The resulting color-transfer layer readily deposits its color pigment upon the upper surface of an underlying sheet and produces sharp, smudge-free copy.
We have found that in addition to stearin the following waxes or wax-like substances are also suitable for incorporation alone or in admixture with one of the others in the color-transfer layer: cetyl alcohol, crude montan waxes, carnauba wax, KP wax of the type produced -by the firm Farbwerke Hochst, candelilla wax and the like. In cases in which the wax is insufiiciently soluble in the cold solvents, the latter may be heated to a temperature of, say, 6070 C. to accomplish such solutions.
Example II The rear surface of a paper substrate is treated with a mixture consisting by weight of substantially 6% polyvinyl acetate of the type manufactured under the name Mowilith by the firm Farb-we-rke Hochst, 10% crude montan wax, 15% graphite pigment and 69% toluene, the layer being then dried to a thickness of about 5-6 grams/ m. When the montan Wax is only silghtly soluble in the toluene solvent at room temperature, the mixture is heated to a temperature of about 70 C. in order to facilitate its dissolution. The front side of the sheet is provided, as before, with a ceresin-wax laye. of about 5 grams/mi Example III A color-transfer layer of relatively clear appearance but having the copying capabilities of those of Examples I and II is provided by admixing 5%, by weight, ethylcellulose (e.g. that marketed by Hercules Powder Company as N-lOO) with 15% pulverulent graphite pigment and acetone solvent for the ethylcellulose in an amount constituting 67% of the mixture. To this is added 13% water which serves as a liquid vehicle for the ethylcellulose. The mixture is deposited upon the rear surface of a paper sheet and dried to produce a layer of about 56 grams/m. which, owing to the small particle size of the synthetic resin, is light-colored but nevertheless yields sharp copy when employed in conjunction with a sheet whose front side is provided with 6 a layer of ceresin wax of about 5 grams/m Chlorinated polyvinyl chloride may be substituted for the ethylcellulose if trichloroethylene and gasoline are substituted for the acetone and water.
Example IV 5 parts by weight of ethylcellulose are admixed with 15 parts of a graphite color pigment and 10 parts by weight of a pulverulent kaolin covering or masking pigment. To the admixture are added 60 parts by weight of acetone and 10 parts water to produce a mixture which may be deposited upon a sheet asdescribed in Example III. The kaolin substantially lightens the color of the color-transfer layer without detrimentally effecting the copying capabilities of the sheet.
Example V In a manner similar to that of Example IV, a colortransfer layer is produced from a mixture of 5 parts by weight ethylcellulose, 20 parts by weight graphite, 5 parts by weight of titanium-white masking pigment, 60 parts by weight acetone and 10 parts by weight of water.
Example VI A similar color-transfer layer is formed from 5 parts ethylcellulose, 15 parts graphite, 3 parts finely divided sillcic acid (e.g. that manufactured under the name Aerosil by the firm Degussa), 60 parts acetone and 10 parts Water, all parts by weight.
Example VII Example VIII A color-transfer layer for red copies is provided by compounding 5 parts by weight ethylcellulose with 5 parts litholred pigment (e.g. of the highly comminuted type produced by BASF under the trademark RMT), 10 parts kaolin, 60 parts acetone, 10 parts water and depositing same upon a sheet to yield a layer of about 5-6 grams/mi Example IX Another suitable color-transfer layer is formed by drying a layer composed, in parts by weight, of 5 parts chlorinated polyvinyl chloride, 15 parts graphite, 5 parts Spanish white (carbonate of lime), 5 parts kaolin, 60 parts methylene chloride and 10 parts benzine having a boiling-point range of 120 C.
Example X The upper surfaces of any of the sheets described in accordance with Examples IIX may be provided with a Wax layer consisting, substantially, of 30 parts by weight of zinc stearate, 67 parts by weight of paraffin and 3 parts by weight of Aerosil. The stearate and paraffin are melted together and deposited from the melt onto a support paper after the Aerosil is added. The resulting layer of about 3 grams/m. can be written upon by ball point pens and is a color acceptor yielding unobjectionable copy.
Example XI Another wax layer may be provided by melting 70 parts by weight of ozocerite (ceresin wax) together with 30 parts by weight of lead stearate and then coating a substrate with this melt to yield a layer of 3 grams/mi A paper thus treated can be printed in the usual manner with printing inks drying at normal rates.
Example XII A Wax surface compatible with writing inks may be provided by depositing from the melt a mixture of 65 parts by weight of parafiin and 35 parts by Weight of a mon-oethanolamide of stearic acid to yield a layer of 3 grams/m Example XIII A melt consisting of 34 parts by weight of ozocerite, 33 parts by Weight lead stearate and 33 parts by weight of the monoethanolamide of stearic acid is deposited upon a sheet as previously described. The resulting paper can be printed in a conventional process with the inks drying at normal speed and can be written upon with both ballpoint and fountain-pen inks.
What is claimed is:
1. Direct-transfer copy material comprising a plurality of superimposed sheets, each having an upper and a lower surface; a layer of color-acceptor agent having a major proportion of wax and including a metal soap in suflicient quantity to facilitate drying of ink deposited upon said layer of color-acceptor agent; and a color-transfer layer on the lower surface of said substrate adapted to preferentially impart color to a layer of color-acceptor agent on the upper surface of an identical underlying sheet.
2. Direct-transfer copy material as defined in claim 1 wherein said metal soaps are heavy-metal derivatives of fatty acids.
References Cited by the Examiner UNITED STATES PATENTS 627,229 6/1899 Foster 11736.3 XR
680,637 8/1901 Brown l1736.3 XR 1,845,568 2/1932 Strawn 117-36.3 XR 2,872,340 2/1959 Newman et a1 1l736.1 3,111,421 11/1963 Newman et al. 11736.7 XR' FOREIGN PATENTS 501,983 3/1939 Great Britain.
WILLIAM D. MARTIN, Primary Examiner.
M. KATZ, Assistant Examiner.