US1978784A - Method of producing multicolor prints and printing plates therefor - Google Patents

Description

f Oct. 30, 1934. D- T MANN 1,978,784

METHOD OF PRODUCING MULTICOLOR PRINTS AND PRINTING PLATES THEREFOR Filed June 9. 1932 Fi Poly. 2. 125 .3. Fa

. INVENTOR T /EODORD/ TTM/M/N 12:: 4 A-ITORNEY atented ct. 3Q, 1934 'llheodor Dittmann, Neumunster, Germany, as-

signor, by mesne assignments, to The llleinecke Company, Inc., New York, N. Y., a corporation of New York Application in... a, 1932, Serial No. 616,246

In Germany June 12, 1931 4 Claims. (Cl. 95-5-1) This invention refers to a method of producing multi-color prints and relates more particularly to a method of producing color-printing plates or blocks for such prints.

In my co-pending application, Serial Number 374,950, filed June 29, 1929, I have described a method of producing toned plates for multi-color printing blocks which comprises the use of one or, still better, several masks for each colorprinting plate. Such masks are usually made of suitable, transparent material and certain parts of each mask, which correspond to those parts of the picture, which are colored in one particular tone, are covered with ink or some other suitable opaque substance. Each mask corresponds to a certain tone value of one particular color, so that, for instance, three masks can be used to produce one color-printing plate, which comprises three-quarter tones, half-tints and quarter tints; one of said three masks comprises an opaque portion corresponding to three-quarter tones of a color-printing plate, the other mask has an opaque portion corresponding to halftints of the same plate, and so forth. The method described in the said co-pending application also comprises the exposure of a sensitized plate througha diapositive, made from a negative of the picture, some or all of the masks, and/or a colored screen. An important feature of this process is the variation of the times of exposure and of the number of articles used in each of the individual exposures. Obviously, the number of possible and actual combinations used while exposing increases as the number of masks employed increases. The negative produced by these exposures is used in the making of a color-printing plate according to well known methods.

An object of the present invention is to im-' prove and simplify the above process and to improve the artistic eflect of the colored prints produced thereby. I

Another object is to provide a simple and inexpensive method of making color-printing plates for multi-colored prints.

I have found that color-printing plates and the prints produced thereby are considerably improved when they are made from negatives which have not been exposed through a diapositive of the picture, but only through masks and/or screens. According to the present invention I dispense entirely with the use of diapositives during exposures, i. e. I do not expose the sensitized plate either through the diapositivel alone, or through the diapositive in combination with one or more masks and/or a screen. I produce one negative for each color-printing plate by exposingsaid negative through one or more masks and/or a screen either once or several times, and I then proceed to make a color-printing plate from said negative in the usual manner. In this way I make three color-printing plates for the three basic colors, i. e. red, blue and yellow. The black-and-white or halftone plate, which is used to produce a print of the image in black, can be made in the usual manner from a black-andwhite negative of the image.

The mask carriers or masks used for the purposes of my invention are usually made of transparent or translucent material and contain portions which are opaque to light. In each mask these opaque portions preferably correspond to a certain tone value of one particular color. The number of masks used in the making of a colorprinting negative of one particular color must depend necessarily upon the variety of tones or tints required for that negative.

After the desired number of masks for each color has been made, these masks are projected through a screen onto a sensitized member, which may be a photographic plate or film or a sensitized metal plate. Thus so-called color separation negatives are made for the final purpose of producing prints upon the sensitized metal plates as used for letterpress printing, or upon the sensitized metal plate as used in photo-lithographic production. The metal plate is then etched and further treated in order to produce a printing plate. The exposures for producing color-selection negatives can take place in either a camera or a contact printing frame.

The number of exposures, the time for each exposure, and the strength of light used for the exposure may be determined by the operator from experience, and may vary in each individual case. Should three masks be required to produce one color-selection negative, said negative may be exposed once through all three masks simultaneously, then through two masks and finally through one mask only. The time of one exposure may be different from the time of another exposure. A screen may be used during all or some of the exposures and an additional exposure may be made through said screen alone. Obviously, pictures having a great variety of shades and tones will require a larger number of masks, more exposures and a greater variety of said exposures than pictures with a few simple shades.

For very simple pictures I may use one positive mask for each color-selection plate, said mask having a uniformly opaque portion corresponduniform printing impression and in a uniformly distributed color throughout the picture. A col ored picture made by using one single mask for each of the basic colors will have uniform color tones without any variations. According to my new method, a black-andwhite or halftone printing plateshould be used together with the color-printing plates in order:

to produce a colored picture. This. black-andwhite plate can be prepared from a diapositive, a negative, or a drawingmade on glass or other translucent medium. I prefer to prepare this plate from a negative made from a positive photograph of the picture. i The outlines of the drawing can be strengthened and/or weakened before the drawing is reproduced on the printing plate. I prefer to use lithographic chalk for strengthening theoutlines o the picture, the other parts of which can after ards be weakened in varying degrees by washing them off either completely or to a certain extent. The selection of a suitable method for making the black-andwhite printing plate depends on the nature of the picture and should be made by the operator according to his practical experience.

Due to the great variety of multi-color prints, a method of making such prints must necessarily comprise several modifications or variations suitable for each individual case. In the case of posters and advertisements, for instance, I may use, during the exposure of a color-selection negative, a translucent plate provided with some or all of the outlines of the picture for the purpose of making them more striking in the final print. This plate may also be a niask, i. e. it may also comprise opaque portions corresponding to a tone value of one particularcolor. The outlines drawn on this plate may be strengthened and/or weakenecl in the same manner as the outlines of the negative used for making the black-and-white printing plate.

The masks through which the color-selection negatives are exposed may be made entirely of an opaque substance and have a light-transmitting portion. A maskmay comprise portions provided with a covering or coverings having different degrees of transparency, and also comprise parts which transmit light. It is more common, however, to use 'a transparent material, such as glass or cellulose, for the masks. The covered portions of the mask need not be entirely opaque, but may consist of a material which transmits less light than the remaining portions of the mask. I prefer, however, to make a mask by covering certain portions of a transparent plate with opaque ink, or by cutting out of paper a silhouette corresponding to saidportions and pasting it on said plate.

The invention will appearmore clearly from the following description, when taken in connection with'the accompanying drawing, which illustrates a preferred embodimentv of the inventive idea.

In the drawing:

Figure -1 shows a colored picture composed for having a dark portion and a; light portion.

the color printing plates.

Figure 2 shows the yellow color component of the picture shown in Figure 1.

Figures 3 and 4 show corresponding blue and red components, respectively.

. Figures 5, 6, 7 and 8 show four positive masks used for producing a yellow color-selection negative.

Figure 9 shows a color-selection negative for the yellow color.

Figures ,10' and 11 show color-selection negatives for the blue and red colors, respectively.

Figure 12 is a negative of the picture shown in Figure 1 which may be used for making a black-and-white printing plate.

Figures 13a to 13c show diagrammatically the process of producing a yellow color-selection negative.

In the drawing, p is a sentized plate, m1, m2,

stead. Then the operator covers with ink those parts of the mask m2 which correspond to a darker yellow shade in the picture, leaving the portion I) uncovered, since the portion b is oi a dark green color in the picture,'and, as is well known, the dark green color has many more blue shades than yellow ones. The masks mg and 1114 are made in a similar manner. comprisesuncovered portions b and c which correspond to the green color in the picture, while the maskmi also comprises an uncovered portion d which corre'spondsto the light yellow color in the picture. 1

After the positive masks m1 to 1114 have been The mask ma prepared, I proceed to make a color selection negp is illuminated through a screen s and the masks m1, m2, ma and 111.4. Then the plate p is exposed through the screen s and the masks 1m, 1m and m4, as shown in Fig. 131). The-third step, shown in Fig. 130 is an exposure of the plate p through the masks msand m4 and the screen s. Then the plate 10 is exposed through the screen s and the mask 1114, as shown in Fig. 13d. The sensitized plate 1) may also be exposed through the screen s alone, as shown in Fig. 13c.

After the several exposures have been completed, the sensitized plate 12 is developed and fixed, and it is then transferred into a color-separation negative for. the yellow color, shown in Fig. 9. The color-separation negatives for the blue and red colors, shown in Figs. 10 and 11 are made in a similar manner. Each one of these color-separation negatives is projected onto a separate sensitized member in order to produce The black-and-white negative of the picture, shown in Fig. 12, may be used directlyior producing a black-and-white printing plate.

It will be noted from the above description that throughout my process I eliminate the use of black-and-white positives or negatives for producing color-separation negatives or color printing plates. I use a block-and-white negative merely for making a separate black-and-white printing plate. I

What is claimed is:

1. The method of producing multi-color printing plates, comprising making firstly a negative of the print to be reproduced in colors, then making from said negative a transparent positive, and thereupon producing a certain number of color separation negatives by applying to a portion of a transparent member, while held in contact with said positive, corresponding to a certain color of the multi-color print to be made an opaque substance and repeating this operation with other transparent members for each color of the multicolor print to be made, exposing a corresponding series of sensitized photomechanical transparent plates successively through said members thereby producing a series of color separation negatives representing the various colors of the reproduction of the original print in colors, and exposing through said color separation negatives sensitized-press printing plates corresponding to each color, and finally exposing said sensitized press printing plates through the above said positive.

2. The method of producing muti-color printing plates, comprising making firstly a negative of the print to be reproduced in color, then making from said negative a transparent positive, and thereupon producing a certain number of color separation negatives by applying to a portion of a transparent member, while held in contact with said positive, corresponding to a certain color of the multi-color print to be made an opaque substance and repeating this operation with other transparent members for each color Value of the multi-color print to be made, exposing a corresponding series of sensitized photomechanical transparent plates successively through said members and through a screen thereby producing a series of color separation negatives representing the various color values of the reproduction of the original print in colors, and exposing through said color separation negatives sensitized press printing plates corresponding to each color, and finally exposing said sensitized press printing plates through the above said positive.

3. The method of producing multi-color printing plates, comprising making firstly a negative of the print to be reproduced in colors, then making from said negative a transparent positive and thereupon producing a certain number of color separation negatives by applying to a portion of a transparent member, while held in contact with said positive, corresponding to a certain color of the multi-oolor print to be made an opaque substance and repeating this operation with other transparent members for each color of the multi-color print to be made, exposing once or oftener a corresponding series of sensitized photomechanical transparent plates successively through said members and through a screen thereby producing a series of color separation negatives representing the various colors of the reproduction of the original print in colors, and exposing through said color separation negatives sensitized press printing plates corresponding to each color, and finally exposing said sensitized press printing plates through the above said positive.

4. The method of producing multi-color printing plates, comprising making firstly a negative of the print to be reproduced in colors, then making from said negative a transparent positive and thereupon producing a certain number of color separation negatives by applying to a portion of a transparent member, while held in contact with said positive, corresponding to a certain color of the multi-color print to be made an opaque substance and repeating this operation with other transparent members for each color of the multi-color print to be made, exposing for each color a sensitized photomechanical transparent plate through a screen and through one or more of said members depending on the color value to be obtained thereby producing a series of color separation negatives representing the various color values of the reproduction of the original print in colors, exposing through said color separation negatives sensitized press printing plates corresponding to each color, and finally exposing said sensitized press printing plates through the above said positive.

THEODOR DITTNIANN.

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