US809955A - Photomechanical printing. - Google Patents

Description

PATENTED JAN. 16, 1906.

J W IPPERS PHOTOMEGHANICAL PRINTING.

APPLIOATIONIILED JULY 6, 1905.

Wz'trzeawesx arrap STATES PATENT orrron JOHN W. IPPERS, OF NEW YORK, N. Y., ASSIGNOR TO ALBERT HENRY XVALKER, TRUSTEFLOF NEW YORK, N. Y.

PHOTONIECHANICAL PRINTING.

Specification of Letters Patent.

Patented Jan. 16, 1906.

Application filed July 6, 1905. Serial No. 268,344.

To all 1071mm may concern.-

Be it known that 1, JOHN W. IPPERs, a citizen of the United States, and a resident of the city of New York and State of New York, have invented a certain new and useful Improvement in Photomechanical Printing, of which the following description and claims constitute the specification.

The object of my invention is to do halftone printing with metal rollers instead of with metal plates, as formerly.

The nature of my invention consists in making a translucent half-tone photograph through a half-tone screen, and in making a sensitive gelatin plate on an elastic base, and in exposing that sensitive gelatin plate to light through that translucent half-tone photograph, and in developing that exposed gelatin plate by bathing it in water, and thereby swelling into relief those areas on its surface which are under the dark areas of the half-tone photograph, while leaving in depression those areas of its surface which are under the translucent areas of the half-tone photograph during the exposure, and in drying that developed gelatin plate in air, and in afterward using that plate in producing on the periphery of a metal roller intaglio or relief printingsurfaces with which to make graduated deposits of ink or color on cloth or paper, and thus to print a copy of whatever graduated picture, pattern, or design is represented by the half-tone photograph.

The merit of my invention includes the fact that metal rollers can be used for continuous printing on strips of cloth or paper, whereas metal plates can be used only for intermittent printing on sheets of paper or other material adapted thereto.

The prior art of half -tone phot0mechan.

ical printing at its best state is briefly as follows: A copper plate is carefully cleaned with a proper powder and water. Thereupon a sensitizing solution composed of fishglue, albumen, chromic acid, water, and biehromate of ammonia is flowed uniformly over the copper plate and dried thereon. That sensitive copper plate is then exposed to light through a translucent halftone photograph. Then that exposed plate is bathed in cold water and washed with a spray of water, which bathing and spraying result in the dissolution and removal of those areas of the sensitizing compound on the plate which were under the dark areas of the half tone photograph during the exposure, while not disturbing those areas which were under the translucent areas of that photograph at that time. The plate is then subjected to several other operations, including etching and reetching and handengraving and mounting on a wooden block. Thus mounted the plate receives printing-ink on its relief areas and transfers that ink in a printing press to whatever sheets of paper or other suitable material are intermittently pressed thereon.

Half-tone printing with metal plates is not applicable to continuous printing on strips of cloth-such as silk, linen, or cotton dress goodsnor on continuous strips of paper like wall-paper, nor on continuous strips of oilcloth for tables or for walls. Those kinds of printing require printingrollers, and such rollers have necessarily been prepared by mechanical means without any aid from photography, because the art of photomechanical printing did not include any practical way of putting a photographic picture or design on a metal roller.

Figure 1 of the drawings is a representation of a design for a five-pointed star, which is assumed to have been made by hand with a brush on white cardboard. Those surfaces which are darkly shaded in Fig. 1 are supposed to be darkly shaded in structureless gray in the original, while those surfaces which are lightly shaded in Fig. 1 are supposed to be lightly shaded in structureless gray in the original. Fig. 1 is shaded in lines with a pen instead of being shaded with a brush in structureless gray, because structureless gray could not be reproduced for the oflicial copies of the patent by the kind of photolithography which is used for reproducing original Patent Oflice drawings in such oflicial copies. Fig. 2 is a front view of a half-tone screen used in my present inven tion; but that figure represents the crossed lines of that screen several times farther apart than they are in the screen itself. Fig. 3 is a view of a half-tone negative which was made on a wet photographic plate in a camera from the design of Fig. 1 with the halftone screen of Fig. 2 interposed between the design and the wet plate and which was completed by stopping out the translucent lines left on its background by the opaque lines 0 the half-tone screen. Fig. 4 is a view of a developed gelatin plate which was made by the exposure of a sensitive gelatin plate to light through the half-tone plate of Fig. 3. Fig. 5 is a view of a copper roller which has received a deposit of ink from the depressed surfaces of the gelatin plate of Fig. 4 and which depressed surfaces are represented by the half-tone shading in that figure. Fig. 6 is a view of an indefinitely-long strip of paper or cloth which has had the star of the original design repeatedly printed thereon by the copper roller of Fig. 5. The black and white areas, which represent the half-tone shading on Figs. 8, 4, and 5, are much larger in the drawings than they are in practice, where they are so small as not to be separately recognized by the naked eye, but to have the op tical efiect of graduated and structureless gray. The lines which compose the shading in Fig. 6 are representative of shading in structureless gray, and that gray shading is represented by lines for the same reason that necessitates the same representation in respect of Fig. 1.

The design of Fig. 1 and the half-tone screen of Fig. 2 and the half-tone negative photograph of Fig. 3 are respectively made in ways already well known in the art of photomechanical printing.

The developed gelatin plate of Fig. 4 is made by the following means, in describing which I specify quantities by Troy weights: I dissolve one ounce of hard German gelatin in six ounces of water in a vessel of its own. I also dissolve one hundred and twenty grains of bichromate of ammonia in six ounces of water in a vessel of its own. There upon I add the solution containing bichromate of ammonia to the gelatin solution, and then I add four ounces of alcohol thereto, and then I filter the compound solution two or three times. The resulting composition of matter is a sensitized gelatin emulsion the ingredients of which I mix together and filter and keep in a dark room or in a room dimly lighted with red light. I make a stock solution by mixing twenty-eight ounces of Water and one hundred and eighty grains of citric acid and five hundred and twenty grains of nitrate of potassium and seventy grains of chrome-alum and half an ounce of liquid ammonia in a vessel of its own. I then take two ounces of that stock solution and mix it with twelve ounces of glycerin and six ounces of water in a vessel of its own, and thus produce a glycerin solution. I next take a sheet of celluloid about onefiftieth of an inch thick and provide it, by means of a sand-blast or "otherwise, with a uniform finely-grained surface on each of its sides, unless it is already so grained. I thoroughly clean this celluloid sheet with alcohol, and then I glue it down upon a perfectly fiat bright steel plate about a quarter of an inch thick by the following means: I take ordinary fish-glue and apply it to the upper surface of the steel plate by means of an inking-roller, and then I apply soft paper to that surface of the steel plate and press it down with a plain roller and leave it a few minutes to dry. Thereupon I apply more fish-glue to the upper surface of the paper, and then I press the celluloid sheet down upon that paper by means of a plain roller, taking care to exclude all air from between the celluloid and the steel. To confirm the union of the celluloid sheet with the steel plate through the intervention of the paper and the fish-glue, I pile the plate thus composed with other like plates with sheets of felt interposed between them, and then I put a heavy weight upon the top of the pile and leave it there until each celluloid sheet is firmly and' smoothly adherent to its steel plate or I accomplish the same result by pressing the pile together in a powerful press. I next clean the celluloid side of the composite plate with alcohol, and I then pour my gelatin emulsion over that side of the plate, and then I place that plate with that gelatin emulsion thereon exactly horizontal in a drying-oven and I leave it there until the gelatin emulsion is coherently dried and baked upon the celluloid surface. Thereupon I take the plate out of the oven and pour a second coat .of the same gelatin emulsion on the first coat,

and then I bake the plate, as before. This production of a sensitive baked gelatin plate must be made in a dark room or in a room dimly lighted with red light, which light may come from an incandescent electric lamp having a red bulb or may be admitted to a dark room through a pane of red glass. The sensitive baked gelatin plate when finished must be kept dark and dry until it is used.

The gelatin plate of Fig. 4. may be made with only one coat of gelatin emulsion in stead of two coats. In that case I make the gelatin emulsion with one ounce more of alcohol and two ounces less of water than I specify when two coats of gelatin emulsion are to be applied to the base of my gelatin late. p I treat my sensitive baked gelatin plate as follows, so as to produce therefrom the developed gelatin plate of Fig. 4: I put that sensitive baked gelatin plate in a photo graphic contactframe with the half-tone negative of Fig. 3 between it and the transparent front of the frame and with its face upon the gelatin plate. I then expose the baked gelatin plate to light passing through the half-tone negative for spaces of time varying from four to ten minutes. The result of this exposure is to harden the difi'erent areas of the gelatin coating on the plate in proportion to the number of rays of light reaching those areas, respectively, through the different areas of the half-tone negative. As no rays of light will pass through the IIO opaque areas of the half-tone negative, the corresponding areas of the gelatin plate are not hardened; but as many rays of light will pass through the translucent areas of the half-tone negative the corresponding areas on the surface of the gelatin will be hardened by the exposure. The sensitive baked gelais removed from the frame in a dark room tin plate having been thus exposed to light and is immersed and bathed in that room, first in slightly-warm water and then in cool water. That bathing causes the absorption of water by the unhardened areas of the gela tin coating, and the absorbed water causes those areas of the gelatin coating to swell upward, and that swelling brings them into relief on the gelatin surface of Fig. 4, while leaving in depression the other areas of the surface of the gelatin plate. If I am working in a temperature above Fahrenheit, I next bathe the gelatin plate for from three to five minutes in a solution of five drams of chrome-alum in twenty-four ounces of water; but this bathing is not necessary when I am working in a temperature as low as 60 Fahrenheit. The bathing 0f the gelatin plate in the solution of chrome-alum tends to prevent the swollen areas of the gelatin from recedin entirely down to the original horizontal leve of the plate when the water is expelled from those swollen areas by the drying of the plate by means of a current of air produced by an electric fan or otherwise, and which drying is the next operation to which the plate is subjected. Still that drying causes the swollen areas of the gelatin plate to somewhat recede, but the gelatin coating under those areas remain comparatively soft and porous, while the gelatin coating under the depressed area of the plate continues to be comparatively hard and dense. I now strip the celluloid base of the developed gelatin plate of Fig. 4, together with its gelatin coating, away from the steel plate to which the celluloid base was glued before the gelatin emulsion was applied thereto, for the steel plate has now performed its function of keeping the celluloid sheet perfectly flat and perfectly level while the gelatin emulsion was being baked thereon.

I prepare the copper roller of Fig. 5 in the following manner: I first apply the above described glycerin solution to the flexible developed gelatin plate of Fig. 4. That solution adheres to and is absorbed by the relief areas on that plate, because they are porous, but is repelled by its depressed areas, because they are hard. I then remove the surplus glyc erin from that flexible developed gelatin plate by means of tissue-paper applied thereto and removed therefrom, and I repeat this operation, if necessary, until no free glycerin solution remains upon the surface of the plate. I next apply printing-ink to the flexible developed gelatin plate of Fig. 4 by a soft and elastic inking-roller or by a succession of such rollers, which ink is taken by the depressed areas of that plate; but it is not taken by its relief areas, because it is repelled therefrom by the glycerin solution therein. The ink which is thus applied to the plate is composed by melting together one pound of asphaltum, one pound of rosin, half a pound of beeswax, one pound of mastic, and three ounces of mutton tallow and then mixing that composition with double its quantity of the crayon ink of commerce, which crayon ink is made of cooked linseed-oil and lampblack without any fat. Thereupon I roll a plain copper roller having a finely-roughened periphery over the inked plate of Fig. 4 with pressure enough to cause sufficient ink to be transferred from the inked areas on the plate to the corresponding areas of the periphery of the roller. Thereupon I change that ink into an enamel by means of the application thereto of an enameling-powder and by means of heat. That enameling-powder is composed of two parts of resin, one part of shellac, and two parts of alcohol melted together and then cooled and finely pulverized. I apply that powder with a cotton ball to the surface of the copper roller, so as to make the powder adhere to the inked areas of that surface without adhering to the naked areas thereof. Then I heat the-copper to a temperature high enough to melt the enamelingpowder into the ink to which it has adhered. This heating results in changing the ink on the surface of the copper roller into an enamel, and that enamel will protect those areas of the copper roller covered thereby from the eating of the etching liquid, which is subsequently applied to the copper roller. I next protect the interior of theroller, if it is hollow, and also its ends with asphalt varnish from the action of the etching liquid,which I next apply to the periphery of the roller. I make that application by simply causing the roller to rotate above a pan containing the etching liquid and with all portions of the periphery of the roller successively passing through the etching liquid in the pan as the roller is rotated. That etching liquid, which may be chlorid of iron, eats into the naked portions of the periphery of the copper roller,

while not affecting those portions of that periphery which are covered by the enamel. I cause the etching liquid to do its etching work for a greater or less length of time, according as I intend to etch more or less deeply into the periphery of the copper roller, and thus give more or less depression to its etched areas. After the periphery of the copper roller has been etched Iwash it with water to remove the etching solution, and then I remove the enamel from its relief areas with turpentine. The periphery of the copper roller having been thus provided with ele vated or relief printing-surfaces composed of the relief areas shown in black in Fig. 5, the

roller is used in a printing-machine as if it had received those surfaces from the hands of an engraver. That use consists in applying ink or color to the periphery of the roller and in drawing a strip of paper or cloth between it and aplain roller opposite thereto and in transferring ink or color from the relief areas of the roller to that strip of cloth or paper.

The particular program illustrated in the drawings has thus far been the subject of this description. That program is confined to relief printing of graduated surfaces in one color 011 strips of paper or cloth. Intaglio printin according to my present invention difiers from relief printing in that the translucent photograph used in the process is a positive half-tone photograph, instead of being a half-tone negative like that of Fig. 3, and in that the copper roller is etched less deeply for intaglio printing than for relief printing, and in that the copper roller should be well polished for intaglio printing, instead of being finely roughened for relief printing before the ink is applied thereto from the gelatin plate. Intaglio printing on my present plan is applicable to silk or cotton dress goods and also to Velvets, satins, and other fabrics where the designs to be printed are graduated, and relief printing on this plan is applicable to printing copies of graduated designs on oil-cloth or on paper; but my present invention is not applicable to any ungraduated printing, because the half-tone screen of Fig. 2 will divide whatever flat masses or unbroken lines may exist in an original drawing or other picture and will thus destroy the continuity of those masses and lines.

A copper roller is said in the description to be the printing instrumentality which is made and used in my process; but such a roller may be made of aluminium, zinc, or other metal and may be prepared and used as set forth in this specification, except that different metals are best etched with different etching liquids.

My flexible celluloid sheet is said in the de scription to be temporarily glued down upon a flat and horizontal steel plate while the gel atin coat is being coherently dried and baked thereon. This flat and horizontal condition and position of the celluloid base causes the gelatin coat to set and dry upon the celluloid base with uniform thickness throughout all parts of its surface.

The flat plate upon which the flexible celluloid sheet is glued down while the gelatin coat is setting and drying thereon may be of some other metal than steel or it may be glass. The flexible celluloid sheet with its gelatin coat may be stripped from that flat plate before it is exposed to light or after it is exposed to light and before it is bathed in water, instead of being kept upon the flat plate until after it is bathed in Water. If the flat plate is metal, the gelatin plate'with the flexible celluloid base should be stripped from the flat plate before the glycerin solution is applied to the gelatin coat in order to avoid any chemical reaction between the metal of the flat plate and any of the chemicals in the glycerin solution; but if the flat plate is glass the gelatin plate with its flexible celluloid base may be left on the flat plate until after the glycerin solution is applied to the gelatin plate and, indeed, until after the gelatin plate is inked.

Before ink is transferred from the inked gelatin plate to a metal roller the inked gelatin plate should be stripped from any flat plate to which it may have been glued, because the gelatin plate must be elastic at that time. That elasticity is necessitated by the fact that the inked gelatin plate must be pressed very hard against the metal roller in order to transfer ink enough from the depressions in the gelatin plate to the metal roller and by the fact that that hard pressure would crush or distort the relief areas of the surface of the gelatin plate if the base of that plate were rigid at that time and by the fact that good ink-impressions cannot be made between two unyielding surfaces. The elasticity of that base at that time is made avail able to prevent such crushing or distortion and to produce good ink impression by means of the presence below that base of some cushioning material, such as felt or soft rubber.

The base of the gelatin plate of Fig. 4 may be a flat and rigid plateinstead ofbeing a flexi ble celluloid sheet, provided such a flat and rigid plate is furnished on its upper surface with an elastic layer of rubber or other elastic material, on the upper side of which layer the gelatin emulsion is spread and upon which it is dried or baked. The rigid foundation of such a gelatin plate may be glass and may be a quarter of an inch thick or more. A layer of elastic material such as soft vulcanized rubber may be spread over with a rubber solution and then fastened down upon such a rigid foundation by drying that adhesive substance. Thereupon the elastic side of the plate thus composed may be coated with a solution of water glass and albumen, and that solution may be dried on that surface, so as to give to the elastic side of the plate an insoluble and porous surface for the reception of the gelatin emulsion and the firm retention of the gelatin film.

When a rigid plate is used instead of a flexible celluloid sheet as the foundation of a gelatin plate, that gelatin plate will retain that foundation through all the stages of its manufacture and use, including the transference of ink from its developed gelatin surface to the metal roller, which is applied to it for the reception of that ink. When that application ICC occurs, the elastic layer between the gelatin surface and the rigid foundation of the plate will yield enough to enable the metal roller to take ink from all the depressions in that gelatin surface without crushing or distorting the relief portions thereof.

I claim as my invention The following process in photomechanical printing: making a half-tone photograph of a graduated picture or design, through a halftone screen: making a sensitive gelatin plate on an elastic base: exposing that sensitive gelatin plate to li ht, through that half-tone photograph: developing that exposed elatin plate, by bathing it in water, and thereby swelling into relief those areas of the gelatin plate which were under the dark areas of the half-tone photograph, while leaving in depression those areas of the gelatin plate which JOHN W. IPPERS.

\Vitnesses ALBERT I-I. WVALKER, HENRY L. REOKARD.

Images