US1773887A - Method of producing printing plates - Google Patents

Description

Aug 26, 1930. L. F. STIRLING METHOD OF PRODUCING PRINTING PLATES Filed Jan. 1'7, 1929 Patented Aug, 26, 1930 LOUIS I. STIRLIITG OF BOUNDBBOOK, NEW JERSEY, ASSIGNOR TO OXFORD VABNISE 'UNITED STATES PATENT. OFFICE CORPORATION, DETROIT, MICH IGAN, A CORPORATION OF MICHIGAN METHOD OF PRODUCING IPBINTING FLATES Application filed J'anuaryl'l, 1929. 4 Serial No. 833,052.

The object of this invention is to provide a process of reproducing designs of various natures on materials capable of receiving an imprint by pressure; textiles, paper, etc.,. for ex- ,5 ample, by which process the design will be printed clearly and Without substantial loss of tonal effects. I

More specifically, an object is to provide a novel and comparativelyinexpensive rocess of producing an intaglio plate suita le for transferring designs on textile fabrics, as well as other materials.

The methods now used for producing intaglio plates for textile printing are generally divided into three classes. One class comprises the step of actually removing metal from a plate or roll as by the use of a tool similar to a chisel, smaller depressions bein I thi onto this coating by the use of a pantograph. Afterward the design is etched .mto the late by the use of a suitable etching fluid. bviously', all the above outlined processes are expensive, since each requires considerable skill I and each is inherently slow. Furthermore,

nately,

made b to. a su cient depth to carry the deslred 1nk I intensity in color all the above processes are limited, each to its individual style of reproduction'and the skill of the mechanic or artist-engraver.

It has been proposed to follow the methods employed in photogravure printing, namely, to transfer the design by means of photographic plates or films and using such photographic plates to form etching medlums, as by means of the usual acid, resist. Unfortuwhen a textile photogravure roll is such process it is impossible to etch and tone, evenwhen a very coarse screen is used. I This 1s mamly due to carry corresponding is used to get-the full tone etching depth necessary for textile use," then the acid is 0 such strength that the resist fails to function in holding back the acid in the semi-tone areas. In photogravure work, semi-tone portions of the plate have wells substantially of the same size, but of difierent depths which -y greater or smaller quantities of color materials. In producing thefact that when an acid of sufiicient strength i gfplate for textile use,'these wells, by reason excessive acid strength, run together, so that many of the semi-tones are lost and become full tones.

Part of the diificulty arises because of the fact that for printin on textiles an excess of color strength is use since a large portion'of this stren th washes out when the color is fixed. Thls wash-out carries a considerable "amount of the pigment material away with it, thus destroym fine gradations of tone.

,It'w'ould seem o vious that this difiiculty could be overcome b applying greater masses of ink or dye for al parts of the design, that I is to say, printing in full tone where half tonetis required and printin in half tone A where quarter tone is require etc. If this device could be resorted to it would still be mpossible to etch clear and definite ink wells in the photogravure plate to carry the then super-quantities of pigment.

The present 1nvent1on enables a transfer of the desired pigment material to textile fabrics, preserving all the original tonal effects. The final printing element produced, namely the plate, is characterized by the fact that it contains disconnected pockets or wells,-

all very distinct but varying in size. The

method or process of producing such a plate is in. general as follows. 7

v The pattern to be reproduced is first photographed throu h a screen in such manner that disconnecte and clearly defined transparent spots or light areas appear on the negative, the spots eing of various sizes, i. e. larger spots corresponding to the darker areas of the pattern and smaller spots corresponding to the lighter but shaded areas. The process is unique in that in taking such photographic negative, the negative is overtogravure plate, that is to say, the negative is transferred-to a positive plate or film, to bring out a positive image; then this positive plate or film is used to form the usual resist,

and the resist is used with a suitable corrosive element to etch the plate or roll.

The process has certain refinements not entirely essential, particularly in that the negative taken through the screen may be reduced in size from that of the subject to save plate cost.

The process includes the further refinement that a bromide print may be made from a reduced negative photograph of the subject or pattern, which bromide print may be readily retouched as desired, to bring out various desired contrasts in color and tone. The bromide is in such case photographed through the screen instead of the original subject.

The manner of printing from the plate or roll may be in accordance with photogravure printing; that is to say, an excess of pigment may be spread onto the plate then scraped off. except at the disconnected pockets, and then the subject may be printed either by contact with the plate or through theinterme'diacy of a take-off roll.

In order that the process may be more clearly understood, I have illustrated the various steps, as preferably practiced, in the accompanying drawing. I

In the drawings, Fig. 1 shows in plan, a small section of a suitable pattern to be reproduced; Fig. 2 shows a reduced negative made from the pattern; Fig. 3 shows an en'- larged print made from the reduced negative, which enlargement may be retouched or colored as desired to form a refined subject; Fig. 4 shows, in plan, a small section of a suitable screen; Fig: 5 is a plan view showing the appearance of a screen such as shown in Fig. 4 when properly focused onto a plate or film to bring out the desired light and dark effects on the negative; Fig. 6 is a diagram illustrating'a full range of tone, such as used in half- \tone or lithographic printing; Fig. 7 may illustrate either the properly exposed negative or the appearance of a suitable carbon resist made from such negative through the inter mediate step of making a positive plate or -fi1m, and Fig. 8 is a sectional perspective view of a small portion of the etched intaglio printing plate.

Fig. 1 illustrates a pattern to be produced on the plate. The pattern may have, for example. an entirely light zone 1, a shaded zone 2, a more deeply shaded zone 3 and a nearly black zone 4.

Assuming that this pattern does not show the desiredcolor or shade contrasts, I may now take a photograph ofthe design on a reduced negative, such as N in Fig. 2, which, of course, has opaque, shaded and practically transparent portions corresponding to the zones 1, 2, 3 and 4 respectively. This negative is reduced in size m'ainiy to efi'ect saving in plate cost. A bromide print for retouching purposes, may now be made in any suitable size, for example. the size of the original pattern. The bromide prmt is designated B in Fig. 3, and the light, shaded and in Fig. 4. This is the usual cross-line screen commonly used to make half-tone plates for type or lithographic printing. In using such a screen, the proper distance from the film or plate is obtained as follows: First, the camera is focused to clear the image on the ground glass so that it appears as does Fig. 4; next. the screen is moved slowly away from the ground glass until dark squares appear on a white back groun somewhat the reverse of Fig. 4; then the screen is moved still further away untilv a checker-board effect of light and dark squares results. This is the most suitable screen distance.

The size of screen selected when making the negative in reduced size, is according to the final screen effect desired on the resist or plate. For example, if a fifty line screen effect he desired on the finished plate and the negative is reduced to about one-ninth the size of the subject, a 150 line per inch screen is used in taking the negative.

The screen is positioned with relation to v and small black dots where the subject is lightest. Now, by virtue of the over-exposure substantially half of the full range of tones are eliminated. In other words, the resulting negative has only those screen effects shown at the left side of the diagram of Fig.

6, designated by the dimension line D, that. is to say, for the darkest tones'of the orig-- transparent dots where the subject is blackest I iual, rounded, square transparent openings is loaded with starch, as previously explained, appear (see 4". in Fig. 7 and for the next so as to allow for somer'emoval of the pigdarkest portion 3 of the subject smaller and meat durmg the dye fixmg process. Dur ng v mbstantially round transparent spotsappear this etching, naturallythe pocketsbecome (asat 3); for the still lighter zone, such as larger in dlameter to some extent, but st1l l 2 in Fig. 1, very smallround transparent not sufiiciently largetorun together and spoil spots appear (as at 2). In the zone of the 'thetonal eflects.

ne'gativecorresponding to the zone 1 of the It will be easily seen that because the reorigin'al subject, theover-ex osure results sist will be substantially entirely dark and m in practically eliminating all 0t effects, that etch resisting, except for the dotted portions, isto say, this zone 1" wherethe original su'ba very clean and even scraping sur ace will ject was entirely white is now for all prac beobtained on the plate orroll. p tical purposes entirely opaque. This is the l Theinvention is obviously suitable for natural, result of over-exposing the entire work'other thanftextile printing; for examnegative. ple, the intaglio plate produced by the method Now, by reason of the fact'of size difierdescribed may be used forwood, marble and ences in the dots, the design, ismaintained like rainin' processes' without substantial (in negative i. e. reverse, light and shade), modi cation. irrespective of the fact that all of the back- I claim: ground on the film or plate of the negative 1. The process of producing an intaglio is opaque; It is important that the intensiprinting plate, comprising taklng a phototying step be governed according to the sub"- graphof the subject to be reproduced through ject, so that all the transparent dots be clear a screen, over-exposing the photo raph to and sharp. cause the design of the. subject to e mam- From the light intensified negative, I protained on the photograph as variable sized duce another plate or film photographically disconnected transparent dots or patches, the

to bring out te design as a positive image. largest dots or patches corresponding to the This is not illu rated, but it is simply the darkest zones of the subject, andthereafter reverse of the gfiect of- Fig. 7. In other using this photograph in a known manner to words, for the la/ ge rounded squares 4, large formthe intaglio plate. I a

. dark or opaque-spots will ap car on the posi-- 2. The process of producin an intaglio *tive image plate or film. Likewise, the spots printing plate, comprising ta ing a negacorresponding to 3 and 2 will be opaque, tive photograph of the subject to be reproand the remainder of the film or plate will duced through a screen, over-exposing'the be substantially transparent. This positive negative to cause the design of the subject to image late or film is enlarged to the desired. be maintained on the negative as disconnectdimenslons assuining that the first negative ed transparent dots or patches for the darkwas reduced, as mentioned' If the plate to est zones ofthe subject, and thereafter using be maideiis' to have the same area as the origthis negative through the medium of a posinal pattern, then the area of the enlarged itive plate or film, a resist and an etching positive image plate'o'r film'will be. equal in fluid to form the intaglio plate.

area to such pattern. Properly exposed, the 3. The rocess according to claim 1, where enlarged positive shows no shaded zones, exin the sub ect photographed as aforesaid comcept the disconnected opaque dots, which prises a retouched positive print made 45 should be brought out clear and sharp. 'throu h the intermediac of a reduced nega- The enlarged positive is now used to protive p otograph of the original subject. duce, as by contact print, the usual carbon 4. The process according to claim 2, whereresist, and the resist is applied to the plate, in "the over-exposed negative is materially and thereafter the plate is etched. reduced in size from the photographed subcopper roll, after this has beencleaned of all lines per inch than the screen efi'ect desired grease and tarnish and the roll is then etched on the finished plate, whereby the desired I through the resist with a suitable agent. such screen effect may be produced on the printin as perchloride of iron in a 40 (Baum) bath. plate from a resist made as enlargement 'The etching usually requires from 10 to 15 the negative. I 7 minutes. In, the finished plate, Fig. 8, there 5. The process of producing an intaglio will result shallow pockets, such as 2 of very printing plate, comprising taking a photosmall diameter, corresponding to the zone 2 graph of the subject through a line screen in of the subject,-larger pockets 3, corresponda camera focused to bring out the screen ing to the darker shaded zone 3, and deeply image in substantially checkerboard efiect on 1.1.3 etched and still larger pockets 4 correspondthe ground glass of the camera-, over-exposin to the very dark zone 4 on the subject. in the photograph to cause the design of the t w1ll be seen that the pockets may be subject to be maintained on the photograph etched to any suitable depth to retain the entirely as variable sized disconnected transas proper amount of pigment, even though this parent dots or patches, and thereafter using 1;;0

Preferably,I apply the carbon resist to the ject, and the screen has a larger number of 3;;

this photograph in'accordance with the usual etching methods to form the intaglio plate,

- whereby the plate has disconnected pockets of varying size reproducing the design of the subject.

6. The process of producing an intaglio plate, comprising photographing the subject in negative through a line screen with the camera focused to obtain a checker-board effeet on the ground glass thereof, over-exposing the negative 'to cause the shaded and dark portions of the design of the subject to appear on the negatives as variable sized entirely disconnected transparent dots or patches, the largest dots or patches corre-- spending in position to the darkest zones of the subject and causing the negative, except for the dots or patches to be substantially opaque, and thereafter using this negative through the medium of a positive plate or or film, an etch resist and an etching fluid to form the intaglio plate.

7. As a new article of manufacture, a printing plate made photographically and by etching, said plate having a non-printing main surface of even height with a large number of depressed entirely disconnected pockets formed therein of varying size, the largest pockets corresponding in position to the darkest parts of the original subject photographed.

8. The process of producing an intaglio printing plate for design printing, comprising, taking a photograph of the subject to be reproduced, using a screen to break up the image on the photograph, light treating the photograph to cause the entire design of the subject to be confined on the photograph to substantially half of a complete screen tone range, and then using the photograph in a known manner, including the use of an etching liquid, to produce the intaglio plate, whereby substantially all the full tone areas of the subject will be represented on the plate by disconnected substantially uniformly shaped pockets and the lighter areas by smaller butpdisconnected pockets varying in size with the intensity of the shade of the latter areas.

In testimony whereof, I hereunto aflix my signature.

LOUIS F. STIRLING,

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