US2039195A - Printing member - Google Patents

Description

PRINT ING MEMBER Original Filed Nov. 9, 1931 Hq'. 3 Hq. A!

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Patented Apr. 28, 1936 UNITED STATES PATENT 'GFFICE PRlNTlNG- IMEMBEB Charles P. Stirling, Wilmington, Mass., assigner to Oxford Varnish Corporation, Detroit, Mich.,' a corporation of Michigan 3 Claims. (Cl. lol-401.1)

This invention relates to printing members and more specically to a printing plate or roll particularly adapted for printing on textiles and other fabrics, and this application comprises a division of my application, Serial No. 573,769, med November 9th, 1931, on the method of deriving the printing medium herein described and claimed.

The general object of the invention is to provide a novel printing plate or roll suitable for printing on textile fabrics and other materials.

The diiliculties in connection with the reproduction of designs on textile fabrics are largely due to the fact that printing on textiles an aniline or other dye is used in which the color is not as intense as in the case'of an ordinary printing-ink employedl in printing on paper, for example( Furthermore, in fixing the dye, a large part of the color is washed out of the fabric. Accordingly, it is necessary to employ a superabundance of pigment or dye in making the impression on the textile fabric. The chief difilculty heretofore in such printing was the lack of a printing plate capable of carrying sufficient pigment or dye and which would still preserve the iine gradations in tone when in use.

Attempts have heretofore been made to employ ordinary photogravure plates for this purpose. Unfortunately, when such a plate is etched to a suilicient depth to carry the desired ink intensity in color and tone, the etching fluid must be of such strength that the usual resist fails to function in holding back the iluid in the semi-tone' areas. In photogravure work, all printing portions of the plate have wells substantially of the same size, but of diierent depths, to carry correspondingly greater or smaller quantities of color material. In producing a plate for use on textiles, the etching fluid, because of its excessive strength, penetrates the resist too soon in the semi-tone areas, thus producing pockets almost as deep as those in the full-tone areas with the result that many of the semi-tones are lost and become full tones.

It has also been proposed to employ half-tone plates for textile printing, the plates being etched in the reverse of the ordinary half-tones,-that is, intaglio rather than relief plates are produced. In plates produced by the half-tone process, the amount of ink carried by the plates is varied by variations in the area of the small pockets or wells which carry the ink. When such plates are etched for textile printing, the small pockets or wells run Atogether in the full-tone areas and the dividing walls are lost. Thus, when the plate is printed from, there is no support for the doctor blade, which tends to dip into the relatively large ink retaining areas and to remove the ink, particularly in the full-tone printing areas. Furthermore, such a plate cannot be topped with a coating of acid-resisting etching varnish and re-etched to produce pockets of greater depth, for the etching varnish is apt to run into the inkretaining pockets in various parts of the plate or roll.

Because of the unsatisfactory results obtained by both photogravure and half-tone processes, as applied to textile printing, the methods now largely used for producing intaglio plates for textile printing, are mechanical, rather than photographic., the metal being removed from the plate or roll by use of an engravers hand tool or by means of die engraving or by a handetch ing process, all of which are expensive and require highly skilled labor.

My present invention contemplates the derivation of a novel printing plate or roll by the use of a combination of the ordinary photogravure and half-tone processes, whereby a plate can be produced which will carry the necessary large quantities of pigment material and which will also preserve all of the ne gradations in tone, thereby enabling accurate reproductions of natural or other objects or designs to be made on textile fabrics.

According to the present invention, a plate is produced embodying the advantages of both the photogravure plateand the usual reversed halftone.plate,that is, a plate made according to the process disclosed herein will have distinct inkretaining wells separated by continuous Walls, which will provide a surface for supporting the doctor blade, and will also embody the large ink capacity of a deeply etched intaglio half-tone plate. Furthermore, the plate may b'e locally topped with a coating of etching varnish, after the original etching has been completed, and then locally etched to a greater degree without destroying the tonal variations or the pocket dividing walls, and the ink wells of the plate are of less area than the area of a regular photogravure ink well of predetermined size.

In carrying out the process, the photographic reproduction made from the original subject to be reproduced is first exposed througha half-tone screen and in making the carbon resist from this reproduction a photogravure screen is employed. Various steps of the process are illustrated in the accompanying drawing, in which Fig. 1 is a greatly enlarged view of an irregular grain half-tone screen; Fig. 2 is a similarly enlarged view of a photogravure screen; Fig. 3 is a diagrammatic representation of a portion of the subject to be reproduced embodying light, intermediate and dark portions; Fig` 4 is a greatly enlarged plan view oi' the printing plate; Fig. 51s a section along the lines 5--5 on Fig. 5.

The ilrst steps in the production of the plate are very similar to the ilrst steps in the production of an ordinary half-tone plate, a photographic camera being employed to obtain the continuous tone negative from the subject to be reproduced. From this continuous tone negative a half-tone positive is made by means of a screen. The apparatus is focused in the usual manner so that images of the subject, as reproduced on the negative and of the stop, are both formed in the proper position on the plate which is to become the positive, thescreen being spaced away from the negative such a distance that the minute openings therein produce minute images of the stop on the plate or nlm. The dots vary in size in accordance with the light, with the result that where the subject is brightest the dark dots are largest.

In ordinary half-tone work a ruled screen, con` sisting of opaque lines on a transparent plate, is employed, the lines being straight and intersecting each other substantially at right angles. However, in producing the present plate, I prefer to employ a stippled or grained or wavy lined screen in producing the half-tone positive, in order to avoid the possibility of confusion or approximate register oi' the half-tone screen with the photogravure screen and the production of unpleasant moire eiects. Such a screen is illustrated in Fig. 1 of the drawing, in which dark portions i0 are curved in an irregular manner and intersect in such a way as to provide transparent or light portions I l of irregular shape and slightly varying sizes.

In producing a carbon resist from the positive nlm or plate, the procedure is substantially the same as that employed in ordinary photogravure work, the resist being first exposed to light shining through the usual photogravure screen, illustrated in Fig.l 2, which consists of transparent intersecting lines I3, with dark opaque squares I4 at the intersections of the lines. In order to avoid any possibility of unpleasant moire effects in connection with either the texture of the fabric or with the grain of the half-tone plate, a wavy line screen may also be employed in this step, although a screen of, the type illustrated will give satisfactory results. 'I'he usual method of exposing the carbon resist is followed, the photogravure screen being placed in contact with the carbon resist, so that the effect of the screen will be to expose a series ot criss-cross lines on the resist to the action of light, thereby hardening the gelatin which has been exposed. The portions of the resist adjacent the dark spots on the screen are unaffected by any light.

The next step is to expose the carbon resist to light passing through the positive. The effect of such exposure is to photograph the design of the half-tone positive onto the carbon resist, the resist being hardened in the light areas and being unaiected in the dark portions.

The resist is then applied to a copper plate or roll in the usual manner and etched with a solution of, for example, ferrie chloride,'thus producing the plateillustrated in Figs. 5 and 6. If further etching is required, it is only necessary to apply a coating of etching varnish. with a roll. to

the tops-'of the dividing walls between the pockets and re-etch the plate so that itwill carrymore pigment.

It will be noted that the plate is a reverse of the original subject; that is, in the subject as shown diagrammatically in Fig. 3, the dark portion I5 is at the left, the intermediate portion i6 in the center, and the light portion Il at the right,

and in the plate the position of the corresponding portions are reversed, the deeply etched portion I5a being at the right, the intermediate portion ISa in the center, and the lightly etched portion Haat the left. This is done to secure a proper reproduction by direct printing and may be accomplished by proper position of the negative in making the positive to secure a reversal of the positive with relation to the original.

The distinction between the plate just described and the ordinary photogravureplates and halftone plates may readily be seen by an examination of Figs. 4 and 5 of the drawing. As shown in the drawing, the dividing walls 20 are of the same height throughout the surface or the plate as is lthe case with the ordinary photogravure plates.

However,4 in the photogravure process the etched away portions of the plates between the dividing walls are of substantially the same area and of varying depth, whereas in the present plate the etched away portions 2| vary in area because of the effect of the half-tone screen and vary slightly in depth. Thus, in the full-tone or darkened printing zone of the plate the portions 2Ia occupy substantially the entire area between the dividing walls. In the middle tone portions the recesses 2lb are slightly smaller in area and in the light portions the areaof the recesses 2 Ic'is still smaller. similar to that in a half-tone plate etched for intaglio printing, but in an ordinary half-tone plate the dividing walls between the recesses in the full-tone areas of the plate would be lost, whereas the walls are present even in the deeply etched portions of a plate made by my process.

Thus, by means of the present process the advantage of the half-tone plate of the ability to hold a suillcient amount of ink is obtained, and the doctor blade supporting surface of the walls is maintained, as in the case of the photogravure plate. As the area of the recesses varies, in accordance with the tones of the plates, the amount of ink carried by the plate is always proportional to the amount of light passing through the negative, and thus the gradation of tone is preserved so long as the etching is not carried far enough to destroy the dividing walls. It is therefore possible to make a. strong etching which will carry a large amount of ink and which will still preserve the fine gradatlons in tone. Also, even in the blacked parts or solid tone regions of the plate, the dividing walls are maintained and a surface for supporting the doctor blade is provided, thus preventing the doctor blade from wiping out the ink in the deep portions. and also providing a wearing surface, insuring long lite of the plate.

I claim:

1. An intaglio printing member comprising a surface provided with ink retaining pockets, the areas and depths of the pockets in certain tone areas varying from other pockets in the same tone area and from the pockets in other tone areas, all of said ink retaining pockets being less in area than a predetermined size of full screen pocket area. whereby a bearing surface is maintained for The variation in the area of the recesses is supporting a doctor blade during the printing operation.

2. An intaglio printing member having ink receiving photogravure wells in a. given tone area, the walls of the wells being non-uniform in shape, and al1 of said wells being disconnected from each other.

3. An intaglio .printing plate having ink retaining pockets, each of said pockets being separated from all other pockets, the pockets being formed by intersecting bands of uniform base width and having protuberances extending into the pockets 5 in the plane of the top surface of the plate.

CHARLES P. STIRLING.

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