US2040247A - Gravure printing process - Google Patents

Description

, to be reproduced.

Patented May 12, 1936 UNITED STATES PATENT OFFICE I Application February 9, 1933, Serial No. 655,930 Renewed October 2, 1935 1 Claim. (Cl. 95-531) The present invention relates to the art of intaglio printing and embodies, more particularly, an imprcvedintaglio printing plate and process of manufacture, by means of which reproductions produced by gravure printing may resemble the original more accurately in both tone and color value than has been possible heretofore with known printing processes.

Half tone reproduction is effected by exposing a negative through a screen to the subject to be reproduced thus forming a contrast negative wherein all dark spots are of uniform density and all light spots of uniform transparency. The varying tones of the subject matter are reproduced by the formation of varying sized dots upon the negative. From this negative, a print is made directly upon the surface of the printing plate, the etching of the plate resulting in the formation of dots the sizes of which vary in accordance with the tone values of the subject. Printing from the surface of these dots, as is done in half tone printing, reproduces the subject with tone values varying in accordance with the sizes of the dots produced by the screen formation and of uniform tone density. Regions of high light will be represented by a series of needle point dots which, because of the negligible surface area thereof and wide spacing therebetween will receive but little ink during the inking operation. The depth of the area on the plate between dots is of no consequence as long as it is sufficient to prevent the inking rollers from depositing ink upon the bottom of the etching. The limitations of half tone reproduction are too well known to dwell upon herein. I

Intaglio printing is accomplished by producing a continuous tone negative from the subject This negative has no absolute opaque areas nor does it have absolute transparent areas, but rather comprises a plurality of flowing tones without screen formation. From these negatives positives are exposed, either through a camera or by contact exposure in a printing frame. In like manner, of course, the positives are continuous tone positives of the same nature as the negatives and contain no screen formation. These positives are with sensitized carbon tissue in a printing frame and are exposed to light. The resulting carbon print is placed in contact with a gravure screen having opaque squares and transparent cross lines and the print transferred to the metal and etched. The resulting printing surface is formed of a plurality of etched portions of equal area, the

placed in contact depth of the areas varying in accordance with the tone value of the subject to be reproduced. The top or original unetched areas of the metal are wiped clean of ink by the doctor blade after ink has been applied to the metal, thus leaving the etched depressions of varying depth filled with ink.

In practicing the above described intaglio process, it is found that the printing surface is not as durable as desired and that the varying tone values in the subject matter to be reproduced photographically are not accurately defined. Moreover, the existing intaglio processes produce patterns or moires in the reproductions due to the screen formation present, and the speed of the doctor blade cannot be increased above a definite limiting value without destroying, partially, the component tone values of the plate or roller. Furthermore, the viscosity and density of the ink must be carefully controlled to prevent the action of the doctor blade from affecting the component tone values of the etched plate or roller. The foregoing limitations are particularly felt in accurately reproducing high light tones in as much as at high speeds, the doctor blade has a tendency to wipe out entirely the ink from the etched portions of the plate.

With the foregoing in view, an object of the present invention is to produce an improved intaglio plate or roller which reproduces tone values accurately and positively.

A further object of the invention is to provide an intaglio printing surface which will accurately preserve the tone definitions of the subject matter.

A further object of the invention is'to provide an intaglio printing surface which is of highly durable character.

A further object of the invention is to provide an intaglio printing surface which will not form patterns or moires in the reproductions.

A further object of the invention is to provide anintaglio printing surface which will function accurately under all speeds of the doctor blade and printing press.

A further object of the invention is to provide an intaglio printing surface which will function accurately with inks of varying viscosity and density.

A further object of the invention is to provide an intaglio printing surface which will reproduce, accurately, the high lights and shadow detail of the subject matter. 1

A further object of the invention is to provide an improved method for producing a printing surface embodying any or all of the character-.

istics above noted.

A further object of the invention is the provision of an improved positive plate for use in intaglio printing, said plate being formed with either a mechanical or grain screen formation.

A further object of the invention is to provide an improved method for producing a screened positive print for use in the method above referred to.

Further objects, not specifically enumerated above, will be apparent as the invention is described in greater detail in connection with the accompanying drawing, wherein:

Figure 1 is an enlarged view in section through a printing plate for use in half tone printing.

Figure 2 is an enlarged view in section through a printing plate for use in intaglio printing, as now practiced.

Figure 3 is an enlarged view in section through a printing plate constructed in accordance with the present invention.

In accordance with the present invention, a continuous tone negative is produced and from this negative a positive is exposed through a screen. The photographic plate used should be of such nature as to impart a continuous tone effect to the dot formation on this positive. In other words, the darkest tones of the subject matter should comprise the largest and densest dots and the varying tones of the subject matter should be represented by dots of corresponding size and density. The absolute high lights will be represented as clear transparent areas containing no dot formation and the shadow or solid areas will contain a sufficient sized white dot to insure an ink carrying cell in the finished etching.

The positive so produced is printed upon a sensitized carbon tissue and transferred to the printing plate or roller and etched, thus not requiring an additional exposure to an engraved screen.

The etching action of a print from this positive is similar to that of a usual gravure print in that the deepest shadows would etch first and the etching would gradually progress until the lightest and finest dots in the high light detail had etched. The shadow dots or darkest part of the subject matter will retain the individual dot formation so necessary to the proper retaining of the ink and the proper wiping of the doctor blade. The absolute high lights which contain no screen dots will print as a pure high light.

It will thus be seen that, by the provision of a screened positive with dots of varying sizes and densities, a more accurate definition of tone values is obtained. The high lights of the positive are represented as small dots and, upon exposing to sensitized carbon tissue, the varying tones of the positive print harden with varying thicknesses or layers of the tissue. The etched plate holds high lights effectively at all speeds of the doctor blade because the high light dot is of smaller area and deeper, thus effectively holding the ink. Moreover, all tones will be maintained With sharper definition and without a moire effect such as obtained in gravure printing.

The accompanying drawing illustrates the character of the printing surface formed by the present invention as compared with the half tone and present gravure plates. A half tone plate is shown in Figure 1 at H) as being formed with a series of printing surfaces H, spaced by recesses l2. As previously described, these surfaces vary in area and spacing to give variations in tone effect.

Figure 2 illustrates a gravure plate, as now made, comprising a plate I 3 having a plurality of recesses M in which ink is received. The recesses are spaced by surfaces [5 which are wiped clean by the doctor blade and the areas of all of the recesses are equal, the depths varying to accommodate more or less ink in accordance with the tone value to be printed.

In Figure 3 a printing plate 16 is shown as constructed in accordance with the present invention. This plate is formed with a plurality of recesses I! which vary in depth and size to accommodate quantities of ink in accordance with the tone values of the subject, the high light tones being reproduced by recesses of small area and depth, in accordance with the process as outlined hereinbefore. While the distance from center to center of the dots remains the same, the effective spacing between the sides of the recesses of the plate will vary in a manner which will be readily apparent. The greater white areas afford an effective support for the doctor blade and thus results in a better wearing printing plate. The process permits the use of screen angles to prevent the formation of patterns or moires.

While the invention has been described with specific reference to the accompanying drawing, it is not to be limited, save as defined in the appended claim.

I claim as my invention:

The method of producing intaglio printing surfaces comprising exposing a soft Working or continuous tone positive plate to a continuous tone negative of a desired image through a half tone screen formation to produce varying sized dots of varying tone densities in accordance with the corresponding tone values of the image to be reproduced, exposing the screened positive on sensitized carbon tissue, applying the tissue to a printing surface, and etching.

ARTHUR DULTGEN.

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