US2183143A - Method of preparing color-printing plates - Google Patents

Description

Dec. 12, 1939. w. s. MARX, JR 2,183,143v

METHOD OF PREPARING COLOR-PRINTING PLATES Filed Sept. 27, 1934 2 Sheets-Sheet 1 F .1 9 .5 Mn m....m '"m'"' m'" "m" Dec. 12, 1939. w. s. MARX, JR 2,183,143

METHOD OF PREPARING COLOR-PRINTING PLATES Filed Sept. 27, 1934 2 Sheets-Sheet 2 INVENTOR.

Patented Dec. 12, 1939 2,183,143 METHOD or meme coma-r rm'rss Walter s. Marx, In, Port Washington, N. 1., as-

signor to Printing Arts Research Laboratories,

Inc., a corporation oi Delaware Application September 2'1, 1934, Serial No. 745.682

2Ciaims.

My invention relates to anew and improved method of preparing color-printing plates. While the invention relates particularly to the preparation of multi-color printing plates, certain aspects of the ihvention apply to plates for lineprinting in black, and for color printing in halftone.

One of the objects of my invention is to provide a new and improved method of preparing plates for printing cartoons or color comic suppl'ements-in multi-coior, so as to provide a sim-' ple and eflicient method for newspaper work.

.Another object of my invention is to provide a new and improved method of preparing plates for printing in 'multi-color, so as to eliminate the necessity of using \skilled operators for securing correct color rendering and blending.

Other objects 01' my inventionwill be set forth in the following description and drawings which illustrate certain preferred embodiments, it being understood that the above statement of the objects of my invention is intended to generally l explain the same without limiting it in any Fig. 1 represents the master black-and-white drawing which is made originally by the artist, a

or a line positive'thereof, and having outline areas S. FIhe line positive may be made on transparentjCelluloid, or other transparent material,iI desired. 1

Fig. 2 represents a photographic or other reproduction. of the subject matter to be reproduced, on a sheet of light-permeable or translucent' or transparent material. The reproduction represented in Fig. 2 has shaded by hand; so as to reproduce all the colors to be printed with the exception of black.

Fig. 3 isa positive corresponding to one or the colors in the colored cartoon or .the like, which fill is to be reproduced. This figure has been made by preparing a plate which prints one of said colors, (such as red, iorexample). and printing with said plate and with a .black ink. ,Hence as yellow.

55 printing, together with a key plate for printing oithe car maining color of the cartoon or the like, such When the plates corresponding to Figs. 3, 4and 5 are inked with suitable colored inks, andfsuch; plates are used in-multi-color the black lines or areas shown in Fig. 1, the sub- 1 :Iect matter is reproduced in full color.

Fig. 6 illustrates certain apparatus which is used in carrying out the improved method.

Fig.7 illustrates the finished printed result, 5

- printed with the color plates, and with the key plates for printing black lines or black areas.

Fig. 8 isan enlargement of a portion of Fig.

6, showing the arrangement of the halftone screen and the other associated apparatus. 10- Fig. 9 illustrates the apparatus used for preparing a transparent color scheme, and which .is also used for opaquing certain portions of the negatives which it is not desired to printl In ordinary multi-color printing, printing plates are prepared, each said plate corresponding to its respective color. In ordinary color printing the printing plates are all half-tone plates, and each of said plates is photographically printed from a suitable negative or the like.

In preparing said negatives, reflected light has been used, and said light has been caused to pass through a halt-tone screen located in the ordinary type of photo-engraving camera, between the lens and the sensitized plate. 5

In preparing colored cartoons or comic supplements,-a variation of this method has been used. In this variation a plate is used for printing the black areas and said plate is a line plate, instead of being a half-tone plate. 30 The usual method of preparing color plates for printing colored cartoons or comic supplements is- -by means of the sd-called Benday I process.

' According to the Benday" process, line prints 35 are made upon the metal pr nting plates, by using the line negative which has been used in preparing the plate for printing the black-and-white tones. (Such plates are then stippled by the operator with the use of a Benda'y screen, in Q40 order to produce half-tone areas which correspond to the colors or to the color combinations which aretobeused.

In carrying out'this process, the operator works from a color sketch, and the correctness of the rendition and the blending of the colors depends upon the individual skill oi the bperator.

Furthermore,'a complicated process is required in order to render the stippli g resistant to acid,

" so that the processes heretofore known require considerable time and many errors canoccur.

Even ifia skilled operator uses the Benday process, many color values cannot be secured properly. Forexample, areas such as the representation' of the sky are usually reproduced by means of the Benday process, with half-tone dots of the same size, thus producing a fiat and unnatural color effect.

My invention utilizes the advantages of color separation by filtration, which is an improvement over the manual separation necessary with the Benday" process.

The ordinary multi-color printing process is not used for printing colored comic supplements or colored cartoons on high-speed newspaper presses, because it is desired to have a solid black line for outlining the objects, the lettered matter and the like.

While my invention relates particularly to the printing of colored cartoons, colored supplements and the like, by means of high speed rotary newspaper presses, it is also applicable to the well known color printing processes, using two colors,

screen reproduction. I

In the preparation of colored comic supple- .ments according to my invention, a black and white line positive (not half-tone) may be prepared by suitable photographic printing of the.

First method A sheet of light-permeable material, such as translucent tracing cloth or paper or the like, is now stretched in contact with and over the drawing or positive which is represented in Fig. 1. This tracing paper is sufiiciently light-permeable so as to render the underneath drawing visible in full detail, when the sheet of tracing paper is in actual contact with the original drawings or the like. If desired, said tracing paper may be relatively light-impermeable, so that it requires actual contact with the drawing, in order to render the black lines visible. However, the tracing material may be of any desired degree of transparency.

The operator then applies coloring material to this tracing paper or the like, so as to reproduce the desired color scheme, in all the colors thereof. If desired, the artist can paint the colors upon the tracing cloth or paper, using any suitable paints or coloring matter. These paints are preferably opaque.

The colored sheet of tracing material which is thus secured, is represented in Fig. 2. This tracing paper does not carry the black lines or black areas and it merely has patches of color which are located in areas corresponding to the color areas between the black lines or black areas of the original drawing.

If the colored sheet of tracingmaterial which has been thus secured is viewed by reflected light, the colored areas are clearly visible.

A series of light-permeable and continuoustone separation negatives (not half-tone negatives) are prepared from the colored positive which is shown in Fig. 2. Each said negative is prepared by illuminating the colored positive which is shown in Fig. 2 by means of reflected light, and successively interposing the usual color separation filters between said colored positive and the respective sheets of sensitized material. Each said separation negative can be made on transparent Celluloid or transparent glass, and it corresponds to one of the primary colors of said hand-colored positive.

three colors, and four or more colors, and fine parent, instead of being opaque.

A half-tone or screen positive is prepared from each said negative. Each half-tone positive can be produced by means of transmitted light, by means of the apparatus shown in Fig. 6 and Fig. 8. The sheet of sensitized paper, transparent glass, film, etc. on which the half-tone positive is made, can be located at the place occupied by member I, a half-tone screen 4 is supported above the sensitized material by bars 5, and the negative is located at the place occupied by member 3. Light is sent through the negative by lamp L. This method of preparing a half-tone positive from a continuous tone negative is explained in my U. S. Patent No. 2,048,876, dated July 28, 1936.

In preparing the respective half-tone positives from the respective continuous-tone negatives, the screen is turned in a horizontal plane so that the lines are at different angles at each exposure, as it is customary in half-tone multicolor work.

The half-tone positives which are thus produced, can be used in preparing corresponding half-tone negatives, by contact printing or by photographic copying and said negatives are used in preparing half-tone printing plates for printing the various colors. These half-tone printing plates, made of metal or the like, together with a black line key plate for printing the black areas or black lines, will reproduce the cartoons or supplements in color, and with the black lines or black areas of the original.

autochrome transparency on transparent glass or transparent Celluloid film, is made from the member shown in Fig. 2, which is prepared as in the first method as above described. In said autochrome transparency, the colors are trans- This transparency is subjected to three exposures, each exposure being made with a different filter of a three-color filter set. The filters of this set ordinarily consist of an orange filter, a gree filter and a blue filter.

The autochrome which is utilized is a positive, and half-tone or screen negatives are made therefrom.

In making these half-tone negatives, I can use the apparatus shown in Fig. 6 and Fig. 8. If the autochrome is of the same size as the desired matter to be printed, it can be located between the screen 4 and the sensitized glass or other material upon which the negatives are to be made. Under such circumstances the colored surface 6e of the autochrome 6 may be in contact with the emulsion or sensitized surface Ie of the transparent plate 1 on which each negative is to be made, and the screen is supported a short distance above the autochrome by bars 5. However, said autochrome 6 may be reversed in position, if desired, since the autochrome is thin.

lens upon the sheets of sensitized material 1, v

upon which the negatives are to be made. The

filter can be located at any suitable place between the lightand the material on which the Third method I Instead of using opaque colors upon the lightpermeable tracing member which is placed above the drawing or positive to' be reproduced, I can 'use transparent colors, which are applied by hand on a member made of transparent material, such as glass or Celluloid or the like, which is placed over the drawing or positive which is depicted in Fig. 1. That is,.instead of of using the relatively translucent tracing paper previously mentioned, I use a transparent material such as glass or Celluloid, and I use transparent colors instead of opaque paints. The apparatus for performing this operation is shown in Fig. 9. This shows a sheet of white paper 30, which is illuminated so as to reflect white light. An easel having triangular vertical walls 3| and a bar 32, may be used for supporting the original drawing or positive, and the superposed and contacting transparent sheet.

The result is to produce a hand colored transparency 6 which is/shown in Fig. 6 andFig. 8 of the drawings herein. This transparency is of the type shown in Fig. 2, in that there are no blacks represented thereon.

As shown in Fig. 6 and Fig. 8 of the drawings herein, the transparency 6 may be placed in contact with its colored side Ge contacting with the, emulsion surface is of a transparent member I made of glass, Celluloid, etc. As previously stated, the transparency 6 may be reversed in position.

I The half-tone screen 4 is held suitably spaced from the member 6, by means of bars 5. The projector is provided with the usual lamp L and with the lens holder 2.

A filter 3 is interposed between the lamp L and the lens of the projector, or in any position in front of the sensitized emulsion. A suitable set of these colored filters is used for producing the required color separation negatives.

In order to secure a negative which corresponds to the blue color, an orange light is used,

by using a filter having an orange color. In

order to secure a negative corresponding to the I red color, a green light is used, by using a filter having a green color. In order to secure a negative corresponding to they yellow color, I use a filter having a purple color or a blue-violet color.

These colors are selected as being complementary tothe colors of the primary colors of the printing inks used in the final reproduction of the work.-

The projector is provided .with a suitable adjustable aperture stop, in order to control the sizes'bf the half-tone dots, which are formedupon the screen or half-tone negatives. of course individual sheets of sensitized material I areused for producingthe individual negatives corresponding to the primary colors. The halftone negatives thus secured are utilized for print.- ing upon the sensitized surfaces of metal plates which are used for making the printing plates. When'these printing plates are inked with colors having the necessary relationship to the colors used in the filtering of their respective negatives,

. of the like.

- said plates will reproduce the original color pattern. Of course an additional key plate is used for reproducing the black lines of the original drawing. This finished result is shown-in Fig. 7.

It will be noted that if Fig. 1 represents a line positive of the original drawing, said line positive is made from a negative of said original drawing, which negative has been made according to the scale to be reproduced. Hence there is no enlargement iii doing the screen work illustrated in Figs. 6 nd a.

In order to prepare the key plate', which is to be used for printing .in black over printings of the three previously described half-tone plates, said negative of the original-drawing is used for photographically printing upon the sensitized surface of the sheet offmetal from which the from improper registration and focusing, are

absolutely eliminated. 1

' Fourth method This method differs from the third method as follows:

A black-and-white positive is printed lightly upon the transparent sheet of film or glass upon which the color scheme is to be prepared. For this purpose, the sheet of film or sheet of glass '6, is provided with a sensitized emulsion Ge in the usual manner. The opaque portions of the black and white positive which are printed upon this transparency have a silver density 01' about forty per cent of the total possible deposit, although'this proportion can be varied. In the other methods, the black lines have not been reproduced, either upon the sheet of. tracing paper or upon the transparency, but in this method I do reproduce said black lines, preferably fainter than in the original. Th s black-and-white posl tive which has been thus directly applied to the transparent sheet of film, glass, or the like which is to be colored, is used as a guide for applying I the color or colors.

Separation negatives'are then made from this color transparency according to the third method. Each separation negative then carries the lightly-printed black part of the original in screen .or half-tone dot formation. This lightlyprinted key image is advantageous since definite guidelines are thus incorporated in the color separation negatives. This facilitates the block- .ing out of undesired portions of each negative, by the application of opaque color to any desired portion of each said negative; For example and in Fig. 5, there are large areas which are free Y All this work is facilitated by means of the lightly printed key image in black and white. The purpose of printing the black lines more lightly than in the original is to make it possible to form a screen or half-tone dot formationof these lines in the screen negative, instead of transparent or clear lines, in said negative;

' Since these guide lines are screen or halftone lines, instead of being continuous-tone and heavy lines, the effect of these lines upon the final color proof is negligible, since said guide lines are printed in dots of the same color as the respective color plate.

When the four plates print in accurate registration, the key plate prints in black color directly over the screen or half-tone dotlines printed by the color plates, so that said screen lines are entirely eliminated.

The relatively light printing of the black lines of the original image is secured by suitable short exposure and by a suitably short period of development. I

For reasons above mentioned, I consider that.

thefourth method is the preferred embodiment, particularly where colored supplements to newspapers are to be printed.

It will benoted that the fourth method differs from the third method in that a light black or grey image is retained in the color transparency. It is obvious that this same variat on may be applied to the photographing of the color scheme of the first and second methods ifdesired, in order to achieve similar results.

According to the second, third and fourth meth-' ods I secure three color separation negatives, each of which is full size and half-tone. These negatives together with the black-and-white key negative are used for preparing the four printing plates in the usual manner.

According to the first method, the screen 0 half-tone separations and the black and white key plate are positives, and contact negatives or reversals are made from these positives and such negatives are used in the usual manner to make the printing plates.

In order to eliminate undes red color relations or color combinations, due to the fact that even the most efflcient color-separation filters are not sufiiciently monochromatic, it is desirable to opaque those portions of; the negatives which are not desired, before the printing plates are made. This opaquing Operation may be performed by the use of the apparatus shown in Fig. 9, by mounting a.sheet of ground glass 33 upon -the easel, and placing the transparency 6 upon said sheet of ground glass.

According to my invention, the artist can work on a single sheet with media which can be handled easily. Likewise and by using the thrd and fourth methods, I can use transmitted light for color separation having nearly pure color characteristics, which passes through the colored transparency. I can thus obtain a longer scale of tone rendition than if the image is projected through a photographic negative whch has silver grains in its emulsion, and thus, according to my improvedv method, I can utilize the entire color spectrum for color gradation. This is not possible when separation negatives are made by the use of reflected light.

In newspaper work, a coarse screen is used, but fine screens may be utilized and the invention can be utilized for any kind of reproduction in colors.

While I have described the use of three color plates,.I can use color plates corresponding to any desired range or separation of the colors.

Generally speaking, I produce the desired color scheme upon a sheet of light permeable material, which is preferably in contact with the representation of the black and white matter which is to be reproduced in color. This sheet of lightpermeable material may be translucent or transparent and the color scheme may be made with the use of opaque coloring matter, or-with the use of transparent coloring matter.

- Said sheet of light-permeable material may have the black and white lines, or said black and white lines may be omitted, according to the respective embodiment which is utilized. This sheet of colored and light-permeable material is now used for making what may be designated as separations.

superior to the first method because the first method requires photographic reversal or an additional photographic printing.

According to the third and fourth methods, a transparency is directly produced so that the preparation of the autochrome transparency is unnecessary. According to the third and fourth methods half-tone negative separations can be made directly from the original color transparency.

Where in the claims I have specified that the transparency which bears the color scheme, is maintained in substantial contact with the sheet of material on which the half-tone separation is produced, I do not wish to lim t myself to actual contact, as it is suflicient for the purposes of my invention if focussing through lenses is rendered unnecessary.

I have shown preferred embodiments of my invention, but it is clear that numerous changes and omissions can be made without depart ng from its spirit. For example, the invention is not limited to the use of a solid unscreened black key plate, but may utilize a series of half-tone plates alone, or combination line and half-tone plates,

of any desired color range prepared in accordance with the principles here disclosed.

Whenever I have referred to the use of an autochrome, it is to be understood that I can. use any type of transparency which is made photographically. Likewise, I can use a half-tone plate for printing black lines, black colored areas, or black tones in the picture. For example, when it is desired to dupli'cate an oil painting whichha been made on opaque material, said painting may have black areas of substantial size. I would then prepare a colored transparency of said picture to the desired scale, including (if desired) the black lines'or black areas thereof, and I would use said transparency by causing it to contact with the emulsion side of the transparent plate on which the half-tone negative is to be prepared. I have referred repeatedly to black lines or black areas and it is to be understood that whenever I refer to black lines in the claims, this term includes black areas or black sections or black portions. The white light is sent through the half-tone screen and through the transparency, a filter being suitably interposed, and the filtered light which has passed through the transparency is caused to aflect the emulsion on the plate. Color separations are thus made, and a fourth exposure through a yellow or correcting filter can be made, in order to prepare (by the fourth exposure) a half-tone plate for printing black lines or black areas in half-tone.

In some cases, the artist may supply a color transparency, made with transparent colors. This transparency can be used by contacting it with the emulsion side of the transparent plate or film on which the half-tone negative is to be made, the white light being caused first to pass through a screen and through a filter.

I do not wish to be limited to any particular positions of the filter and of the screen relative to the sensitized plate or film on which the halftone negative is to be made.

For example, the white light can first pass through the filter, then through the screen, then through the transparency, and then fall upon the emulsion of the plate. The light may be caused to pass first through the screen, then through the filter, andthen through the transparency. The light can also first pass through the screen, then through the transparency, and then through the filter. A thin filter such as a gelatine filter can be used in the last mentioned combination, and said filter can be caused to contact with the emulsion of the plate or film, and the transparency can contact with the filter.

The transparency can be located in the projector, so that it is focused upon the plate or film. In the last mentioned case, the filter can be above or below the transparency and above the lens, or the filter can be below the lens, and located between the lens and the screen, said screen being above the plate or film.

Heretofore, and in order to produce plates for multi-color printing, the original colored painting or the like was made with opaque painton opaque material, which opaque material, such as canvas, usually had a white color. Said painting was then illuminated so that light was reflected therefrom, and this reflected light was used with a series of filters and with a screen, so as to produce direct half-tone negatives by reflected light. This led to complications and errors. The color of the opaque background material and the grain of said material affected the color separation. Likewise, the operator had to adjust the various factors simultaneously in order to secure simultaneous color separation by reflected light and screen dot formation. 7

According to my invention, if I desire to reproduce a painting which is made with opaque paint, I first use reflected light to produce continuous tone separation negatives, according to the final scale of the reproduction. These continuous tone negatives are then used to make half tone positives, thus dividing the work into two stages. Likewise, the scale of the work remains uhchanged'during the half-tone work.

It is far superior to prepare a transparency of the painting, so that transmitted light can be used for making half-tone separation negatives directly from the transparency, and this is the preferred method. This transparency is made according to the desired scale, so that the halftone work and color separation are done by contact printing, without any change in scale.

This is very important in securing plates which will produce color printing in proper registration.

The function of the half-tone screen is to interrupt the beam of transmitted light, at predetermined portions of said beam of light. Said interrupted beam of light passes through the transparency and it is filtered at any suitable point in advance of the sensitized surface on which the half-tone separation is being prepared. By having the transparency either in actual contact with, or in substantial contact with said sensitized surface (as where a filter is interposed between the transparency and the sensitized surface) the half-tone separation is made without any change in scale and without the need of focusing.

I claim:

1. In the art of preparing printing plates for multi-color printing of matter, said matter containing black lines, those steps which consist in photographically printing a black and white positive of said matter on a sheet of transparent material while photographically printing the black lines on said positive more lightly than the black lines in the original matter, and representing the color scheme with the exception of black color, upon said sheet.

2. In the art of preparing printing plates for multi-color printing of matter, said matter including black lines, those steps which consistin photographically printing a black and white positive of said matter upon a sheetof transparent material while photographically printing black lines on said positive more lightly than the black lines on the original, preparing the color scheme, with the exception of black color, upon said sheet of transparent material, preparing separation half-tone negatives from said colored sheet of transparent material, blocking out undesired portions of said negatives, said negatives having the black lines which are on said sheet of transparent material represented in half-tone dot formation, and then using said negatives for preparing printing plates corresponding to the respective colors.

' WALTER 8. MARK, JR.

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