US3210188A

US3210188A - Method of producing printing forms for intaglio printing

Info

Publication number: US3210188A
Application number: US171459A
Authority: US
Inventors: Gorig Josef
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-02-08
Filing date: 1962-02-06
Publication date: 1965-10-05
Anticipated expiration: 1982-10-05
Also published as: GB993694A; NL274574A; CH398314A; BE613553A; DE1242098B; DE1295370B

Description

Oct. 5, 1965 J. GGRlG 3,210,188

METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING Filed Feb. 6, 1962 7 Sheets-Sheet 1 Fig.7

Fig.3

/NVEN r04 Fig, 4

JOSEF e'c'ame ATTORN EYS Get. 5, 1965 J. GCRIG 3,210,188

METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING Filed Feb. 6, 1962 7 Sheets-Sheet 2 INVENro/ JOSEF G6RIG ATTORNEYS Oct. 5, 1965 J. GORIG 3,210,188

METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING Filed Feb. 6, 1962 7 Sheets-Sheet 3 III INVENrOP JOSEF eRle ATTORNEYS Oct. 5, 1965 J. GORIG 3,21

METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING Filed Feb. 6, 1962 7 Sheets-Sheet 4 Fly 10 Fig 7 INVENTOQ JOSEF ems ATTORNEYS J. GGRIG Oct. 5, 1965 METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING '7 Sheets-Sheet 5 Filed Feb. 6, 1962 JOSEF G6RIG ATTORNEYS Oct. 5, 1965 J. GORIG 3,210,188

METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING '7 Sheets-Sheet 6 Fig, 78

Filed Feb. 6, 1962 mmvro/e JOSEF edRle wwwqw ATTORNEYS Oct. 5, 1965 J. GORIG 3,21

METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING Filed Feb. 6, 1962 7 Sheets-Sheet '7 lNVE/VTUP JOSEF sms Mara ATTORNEYS United States Patent 3,210,188 METHOD OF PRODUCING PRINTING FORMS FOR INTAGLIO PRINTING Josef Giirig, Schillerstrasse 26, Ditzingen,

near Stuttgart, Germany Filed Feb. 6, 1962, Ser. No. 171,459

Claims priority, application Germany, Feb. 8, 1961, G 31,550 14 Claims. (Cl. 9638) The present invention relates to a process of producing printing forms for intaglio printing and more particularly to further improvements in the process as described and claimed in my copending application, Serial No. 72,410, filed on November 29, 1960, and entitled Intaglio Printing Screen for superimposing With Autotypy Screen Positives in the Production of Etchings for Autotypical Intaglio Printing.

In printing forms for intaglio printing, the image to be printed is generally etched or engraved into the printing form so as to be recessed therein. The tone values which are etched into the printing form are permeated during the etching by the intaglio screen network. The intaglio screen is required in the printing forms in order to produce the so-called doctor bars or webs which are necessary for guiding the doctor. In etching according to originals, the image to be printed consists of cells of an equal size forming ink wells which are etched into the copper to different depths in accordance with the tone values of the diapositive and are separated from each other by the raised doctor Webs.

The production of etchings according to originals, especially for multicolor printing, can be carried out only under considerable difficulties which are caused first by the fact that it is not possible to print proofs of the partial colors as simply and correctly as it is possible, for example, in offset printing, in order to check them for the accuracy of their tone values, and, second, by the fact that during the etching process the tone values of the originals may become considerably displaced and falsified.

The effect of these two instability factors is that usually more or less extensive so-called cylinder corrections have to be carried out on the printing forms for printing the edition which are quite expensive at least because of the necessary interruption of the operation of the machine.

Screen positives for variable-surface intaglio printing appear very flat and poor in contrast because of the intaglio screen lines which are copied in, and it is therefore hardly possible to judge the correctness of their tone value. Because of this lack in contrast, it is also not possible to prepare offset copies on zinc plates of these screen positives and to make a proof thereof by the offset process. The offset proof would be just as flat and poor in contrast as the screen positive and it would not in the least correspond with the print attained from the intaglio etching.

The objects, features, and advantages of the present invention will become apparent from the following detailed description which is to be read with reference to the accompanying drawings.

In these drawings, FIGURE 1 shows a full tone, that is, a surface which is uniformly colored and has a tone value of 100.

FIGURE 2 shows the reproduction of such a full tone in an intaglio printing form in which the full-tone surface is permeated by the lines of an intaglio screen which has a linear ratio between white and black of 1:2.5. Seen as a surface, the lineation amounts to 49% of the entire surface area of the screen.

See

FIGURE 3 shows a screen diapositive forming the reproduction of a so-called neutral or greywedge, that is, of a tone value extending from light-grey to black of an autotypy screen. The tone value therefore ranges in this case from 1 in the upper part of this drawing to in the lower part.

FIGURE 4 shows the same tone value ranging from light-grey to black, but changed by an intaglio screen according to FIGURE 2 to form a screen positive for the variable-surface method. For producing the screen, an intaglio contact screen is used with a ratio between white and black of 1 to 2.5. A comparison of FIGURE 4 With the autotypy screen according to FIGURE 3 shows that the surface area of the printing elements of the screen positive according to FIGURE 4 amounts to slightly more than 50%, so that the' range of the tone values extends from about 1 to 50.

FIGURE 5 is a similar illustration of the gradually changing tone values but with the use of a finer intaglio contact screen with a linear ratio between black and white of 1:3. The range of the tone value of the screen positive then amounts to slightly more than 1 to 50.

FIGURE 6 shows the reproduction of the same gradually changing tone value in an autotypy screen positive according to the so-called Dultgen method, in which the range of the tone value only extends to a checkerboard pattern and also amounts only to 1 to 50.

Summarizing the above, it will therefore be found that according to the conventional manner of breaking up the image, the strongest tone value in screen positives for intaglio printing amounted only to 50% of the full tone according to FIGURE 1.

If in the process of producing intaglio etchings the image is to be broken up by means of screens in order to permit an offset proof to be made from the screen diapositive for judging the tone values, the screen diapositive should have a full tone value range from 1 to 100. This range is necessary since the screen elements are reproduced in the offset plate only in two dimensions, whereas in the intaglio etching the same screen elements have three dimensions so that the amount of ink in the ink wells of each screen element is proportionally greater, and a proof of the tone values Would be much too strong if the screen diapositive, possibly after having been retouched, would be transferred to the intaglio printing cylinder without change with a tone-value range of 1 to 100. Because of the additional depth of the screen elements, the tone value would in this case not need to have a range of more than 1 to 50. Screen diapositives with such a low range of tone value are, however, inadequate for proofs in the offset process for the reasons as previously mentioned. Theoretically, it would seem to be possible to transfer screen diapositives to the intaglio cylinder which have a range of tone value of 1 to 100 and may be used for proofs by reducing the third dimension of the screen elements, that is, by not etching so deeply. However, the etching must have a certain depth in order to attain a print of a sufficient color strength.

It is an object of the present invention to produce intaglio etchings by means of screen diapositives in such a manner that the latter permit the production of proofs with correct tone values by the ofiset method, while preventing the range of the tone value of the intaglio printing forms which are made therefrom from being too large. For attaining this object, the present invention provides that the screen diapositives are prepared in a manner so as to have a range of tone values which suffices for attaining proofs of correct tone values by the offset method and that, While the screen diapositives are transferred to the intaglio printing form, a screen is superimposed thereon which has a transparent component amounting to no more than two thirds of the screen surface and preferably amounting to about 30 to 60% thereof.

Further details of different modifications of the invention as well as additional advantages thereof will be apparent from the following description which is likewise to be read with reference to the drawings.

According to one embodiment of the invention, line screens are employed for being superimposed upon the diapositive. Thus, for example, FIGURE 7 shows the autotypy'screen diapositive according to FIGURE 3 on which a one-line screen is superimposed which has a ratio between white and black of 1:1. The image elements which are etched into the printing form are shown in black in the drawing which also shows at the outer edges thereof the structure of the one-line screen.

For producing the screen diapositive, either the corn ventional autotypy screens or contact screens with checkerboardlike screen elements may be employed. Contact screens of the type as illustrated in FIGURE 8 have also proved very satisfactory. Contrary to autotypy contact screens with square screen elements the screen elements are in this case of an elongated or rodlike shape. The screen positives which are made with such screen elements have a shape as shown in FIGURE 9. This screen shape when applied for producing intaglio printing forms has the advantage over the autotypy screen that the rodlike screen elements are broken up into dots by the superimposed screen according to FIGURE 7. If, for example, each rod-shaped screen element has a length of 1 mm. and if a screen with 120 lines per cm. is superimposed thereon, three screen dots will be attained per each rod-shaped screen element.

According to another embodiment of the invention, a line screen is employed for breaking up the image, that is, for reproducing the tone value of the original when producing the diapositive, and the diapositives which then contains the tone values in the form of the line screen is, preferably after being retouched, transferred in a conventional manner upon a light-sensitive material in which it is crossed by a line screen. Thus, for example, a picture is taken of the original by means of a line screen, the lines of which extend at an angle of 45, and this screen diapositive is then superimposed during the transfer upon the printing form by a second line screen, the lines of which extend at an angle of 135. This may be done, for example, by retouching the diapositive with the 45 screen lines in an offset process in accordance with the offset proof so that the individual line screen diapositives of the difierent partial colors will be retouched so as. to have the correct tone values, whereupon the second line screen with the lines extending at an angle of 135 is superimposed, for example, in the so-called carbon tissue, upon the respective line screen diapositive during the transfer of the latter to the printing cylinder.

It is a known fact that the tone values of an original can be reproduced not only in the form of dots of different sizes, that is, by means of a dot screen, but also in the form of lines which are wider or a narrower in ac cordance with the tone value of the original. Such originals will hereafter be called line screen reproductions or line screen positives. Generally speaking, line screen reproductions or positives have previously not attained any importance in any printing method, probably because they did not offer any advantages over the conventional dot screen reproductions as were generally applied. For carrying out intaglio printing, the line screen reproduction according to the inventon may, however, be utilized to great advantage.

Line screen reproductions may be produced in the following manner:

(1) The tone values of an original may be reproduced by line screens by means of a clich engraving machine of a known design. This machine also permits the If line screen reproductions are produced by means of clich automats, it is advisable to cut the engraving into a photographic layer which is blackened by development either before or after the engraving is made. After a proof is made of the line screen reproduction, it is thus possible to carry out in the conventional manner any corrections of the tone values as may be necessary in the original engravings by means of Farmers reducer.

For the purposes of the present invention, the use of a line contact screen appears to be of special advantage for reproducing the correct tone values. Contact screens as such consist of a film with black lines on a transparent base and a tint which gradually diminishes from these lines toward the transparent center. They are called contact screens because they are applied directly upon the light-sensitive layer, for example, between the negative made from the original and the photographic material. Such contact screens are commonly employed for autotypy screen reproductions, for book printing, and for oifset printing, as well as for intaglio printing for carrying out the so-called variable surface method. Line contact screens have so far not been known and prior to this invention there was also no need for them for carrying out book printing, offset printing, and intaglio printing according to the known methods. However, for making reproductions for the purpose of producing intaglio etchings according to the present invention, the possibility of employing line contact screens constitutes an important improvement in the art.

A further embodiment of the invention for producing printing forms for intaglio printing consists in taking two line screen photographs of each partial color image in such a manner that, when the two photographs are superimposed upon each other, the lines thereof cross each other. One photograph is taken, for example, so that the screen lines extend at an angle of 45, while the other photograph is taken with the screen lines extending at an angle of While the photograph with the 45 lines is retouched and used for producing the offset proof, the photograph with the 135 lines may remain unretouched since it is only required for forming the doctor bars or webs which are necessary in the printing form. For producing the printing form, the line screen positives with the angles of, for example, 45 and 135 are successively copied upon the carbon tissue. A printing form which is made in this manner is similar to a printing form for which the screen positive has been made by means of a cross screen for the variable-surface method. The two kinds of printing forms differ, however, by the fact that in the variable-surface method the screen points have straight sides, while those in the above-mentioned example are curved or bent in accordance with the course of the lines of the two line screen positives which are copied upon each other.

This embodiment of the invention is illustrated in the drawings. FIGURE 10 shows a section of a line screen positive which has been produced according to the invention, FIGURE 11 shows the carbon tissue copy of this line screen positive, FIGURE 12 shows this carbon tissue copy after the second line screen has been copied thereon at an angle of 135, FIGURE 13 shows the carbon tissue copy according to FIGURE 12 after being transferred to the printing cylinder, while FIGURE 14 shows the etched image according to FIGURE 13 on the printing cylinder.

Thus, by means of a line screen which is set at an angle of, for example, 45 and has a ratio of white to black of 1:3 a line screen diapositive of a partial color image according to FIGURE is first made of the original to be reproduced. A proof may then be made, for example, by the offset method, of this diapositive as well as of the line screen diapositives of the other partial color images. This proof may be used as a basis for retouching the diapositives. Thereafter, a copy of each line screen positive is made in the usual manner on carbon tissue, as shown in FIGURE 11, in which the black lines indicate exposed gelatine and the white lines indicate unexposed gelatine. The line screen is then copied over this carbon tissue copy so that the image structure according to FIGURE 12 is attained. This carbon tissue copy which is provided with the two line screens is then transferred to the printing cylinder and the unexposed gelatine is washed out so that the copy then has the appearance as shown in FIGURE 13, in which the black lines indicate hardened gelatine and the white areas the unexposed parts of the surface of the intaglio printing cylinder. After etching and removing the hardened gelatine, the printing cylinder shows the image in accordance with FIGURE 14 which illustrates that the size of the color values is determined by the lines which are of an irregular width and extend at an angle of 135, while the webs of an equal width which extend at an angle of 45 serve as doctor guides and limit the intermediate ink wells in their position.

According to another embodiment of the invention as previously mentioned, aline contact screen according to FIGURE 15 is employed in place of a normal line screen for breaking up the image or for reproducing the tone values. In this line contact screen, the line-shaped areas between the black lines have a shading which gradually decreases in strength from these lines toward the center Where only a narrow transparent line remains.

The above-mentioned order of succession of copying the line screen dispositive and the line screen upon each other in the carbon tissue is not compulsory. It is also possible first to copy a line screen of 45 into the carbon tissue and then to copy over it the retouched line screen positive. Also in this case the same structure as shown in FIGURE 12 will be attained. It is, however, impossible to copy both line screens simultaneously with one exposure since the lines of the screen positive and of the intaglio screen would then cover each other at the points of intersection and no blackening or hardening of the chromate gelatine would then occur with the result that the doctor webs would not run through in the printing form.

For the further embodiment of the invention as illustrated in FIGURES 16 to 19, two photographs are taken for each printing form by means of a line screen with an angular osition of 45 and a line screen with an angular position of 135. As previously mentioned, only one diapositive, for example, according to FIGURE 16, is then retouched and used for making proofs. The two positives are then copied upon each other in the carbon tissue in the manner as illustrated in FIGURE 18. The black line-s again indicate exposed areas and the white areas unexposed gelatine. This carbon tissue copy according to FIGURE 18 then results in the etching on the printing cylinder as shown in FIGURE 19.

This last-mentioned embodiment of the invention has the advantage over the other embodiments that, because of the employment of line screens in place of cross screens for taking the photographs and for copying-over, only one angular position together with its complement which is 90 larger, that is, in the particular examples as described the angles of 45 and 135, are required, whereas when employing cross screens for splitting up the image as well as for superimposing the screens which form the doctor webs, each two angular positions are required which differ, for example, by 90 from each other so that in superimposing, an angular displacement of at least 15 must be carried out. This necessity is avoided in the present embodiment of the invention so that the danger of a moir formation is still further reduced or prevented entirely.

It should further be pointed out that the ratio between the transparent part to the opaque part of the line screens as applied may be varied considerably in accordance with the requirement-s in each particular case. Thus, for example, the ratio between white and black of the line screen in which the copy is traversed by the line screen positive may also amount to 1:1 or 1:4, rather than 1:3 as previously mentioned. It is also not necessary that the line screen positive and the line screen crossing the same have the same number of lines. For example, the line screen positive may have 60 lines per cm., while the intaglio line screen has lines per cm., or vice versa. Finally, the lines of the line screen also do not have to be straight but they may be wavy or in some cases even be broken but not interrupted entirely but so as to extend through the entire length thereof.

If after a line screen, reproduction has been retouched and a proof been made thereof, so-called multiple dias are required thereof, the line screen which crosses the line screen positive may already be copied into the negative during the recopying.

In the manner as illustrated in the drawings, it is possible for producing the intaglio printing form according to the invention to employ screen positives which are attained by means of autotypy screens, one-line screens according to FIGURE 15, or rod-shaped screen elements according to FIGURE 8. Naturally, screens of other design-s may also be used.

The above description relates to the manner of carrying out the basic concept of the invention and to the different embodiments thereof While applying the usual processes of reproduction, that is, the production of the partial color images by means of a photographic camera, the production by photographic means of the screen di-apositive of the negative as attained by the photograph, the transfer of the screen diapositive, possibly after retouching for the correction of the tone values, to the light-sensitive mate-rial of the so-called carbon tissue and the superimposition thereon of the sec-0nd screen which reduces the transparent component in this carbon tissue or in the transfer to the printing cylinder, and the production of the screen image in the printing form, that is, for example, on the copper intaglio printing cylinder by chemical etching.

Printing forms for intaglio printing may, however, also be produced by clich engraving machines by electromagnetic means by scanning an original photoelectrically. Such methods are described, for example, in the published German patent applications of Hell, DAS 1,004,923 and DAS 1,004,877.

It has now been found that the known electromagnetic engraving process may also be advantageously applied for carrying out the method according to the different embodiments of the present invention for producing printing forms for intaglio printing by the employment of screen di-apositives and a second screen superimposed thereon. For this purpose, a screen positive is first prepared either by photolithographic means or electrornagnetically by a clich engraving machine. After a proof is made and possibly also a correction of the tone value is carried out, this screen positive is transferred to the printing form by the electromagnetic or electronic means of one of the known apparatus, whereby the range of the tone values is reduced to the desired extent. This is preferably done by photoelectrically scanning only a certain part of the existing screen elements in the screen positive and by engraving the same electromagnetically into the printing form. During the transfer to the printing form, the screen elements are then superimposed according to the invention by a screen which has a transparent component amounting to no more than about twothirds of the area of the screen surface and preferably to about 30 to 60% thereof. In the end result, the printing form which are thus attained therefore correspond to those previously proposed by the inventor and especially those according to the present invention.

The reduction of the range of the tone value in the electromagnetic transfer of the screen diapositive to the printing form may be carried out with considerable advantages and in a relatively simple manner if the screen diapositive is provided with a line screen design. This phase of the invention will now be described with reference to the drawings.

For transferring the screen positive according to FIG- URE to the printing form, the same is inserted, for example, into an electromechanic intaglio engraving machine as described in the mentioned German published patent application DAS 1,004,923, but at such an angular position that the direction of operation of the photoelectric scanning head extends to the screen lines of the positive at an angle, preferably of 90, as indicated in FIGURE 21 by the hatched stripes. Whereas the manner of operation as described in the mentioned German application DAS 1,004,923 requires that a screen frequency is superimposed upon the control voltages of the engraving system, this is not required in the method according to the invention since the scanning head which has a width equal to that of one of the hatched stripes as shown in FIGURE 21 meets the transparent stripes, which are indicated in white in FIGURES 20 and 21, either before or after crossing a screen line so that the engraving tool will then be automatically lifted. On the other hand, when the engraving of each row of screen dots is completed, the transverse feed of the scanning and engraving system should be shifted by a multiple of the width of the scanning head and engraving tool so that the system will not again be switched on until a certain distance has been left free which corresponds to the white stripe in FIGURE 21 which extends at an angle of 135, whereupon the width of the next hatched stripe is scanned. This transverse feed of the scanning and engraving system should be adjusted so that the unscanned white stripes extending in FIGURE 21 at an angle of 135 practically produce a reduction of the range of the tone value to no more than about two thirds, preferably to 60% of the full value. The black areas indicate the intersecting of the scanning head with the opaque lines of the screen positive, and these black areas form those parts of the original which are engraved into the printing form, as indicated in FIGURE 22.

In this embodiment of the invention the tone values of the screen positive according to FIGURE 20 are made lighter in the printing form according to FIGURE 22 by about 50% and this printing form therefore equals one as produced photochemically according to the invention. The degree of lightening up the tone values may, of course, also be varied in this case by varying the distance between the individual lines to be scanned. The fineness of the screen lines extending in the transverse direction as produced electromechanically or electronically as compared with the lines of the screen negative is determined by the width of the engraving tool.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. In the method of producing an intaglio printing surface from an original having a range of tone values, the steps comprising (a) making a screened diapositive from said original reproduction, said diapositive having the full range of tone values present in the original sufiicierrffor making a proof print by the offset process,

(b) printing by offset a proof of said diapositive,

(c) retouching the diapositive to correct the tone value thereof as indicated by the offset proof,

(d) then transferring the configuration of the screened diapositive onto a printing surface to be relieved in the image areas for intaglio print-ing,

(e) forming on said printing surface a doctor bar forming second screen configuration, in which the doctor bar forming screen configuration has a doctor bar forming area amounting to no more than twothirds of the total printing surface area, and

(f) relieving the printing surfaces to form ink receptive Wells therein according to the combined configurations produced in steps (d) and (e).

2. In the method of producing a set of printing surfaces for multi-color intaglio printing from a set of color separations, the steps comprising (a) making a separate screened diapositive from each separation, each diapositive having the full range of tone values present in the original for making an offset proof from that diapositive,

(b) retouching said diapositives to correct the tone value thereof,

(c) printing by offset proofs of each of said diapositives,

(d) again retouching said diapositives as indicated by the tone value exhibited in ofifset proofs,

(e) transferring each said diapositive to a separate printing surface to be prepared for intaglio printing,

(f) superimposing on each said printing surface an intaglio screen configuration in which the doctor bar forming transparent component occupies no more than two-thirds of the area of the surface, and

(g) relieving each said printing surface to form ink receptive wel-ls therein according to the combined configurations produced in steps (e) and (f).

3. A method as defined in claim 1, in which said screened diapositive and said second doctor bar forming screen are combined by copying them in separate stages into a light-sensitive carbon tissue, and in which, after these two exposures are made, said carbon tissue is transferred to the printing surface.

4. A method as defined in claim 1, in which two photographs are taken of the original by means of line screens each having screen lines extending at an angle to those of the other screen, retouching one of said photographs to form a screen diapositive, and then copying the retouched screened diapositive and the other unretouched photograph over each other into a light-sensitive material such as carbon tissue.

5. A method as defined in claim 1, in which the print ing surface is relieved by means of a conventional etching process from the superimposed screened diapositive and doctor bar forming screen configuration transferred to the printing surface.

6. The method of producing an intaglio printing surface as defined in claim 1, in which step (e) comprises forming on the printing surface a doctor bar forming screen configuration in which the doctor bar forming area amounts to between 30 and 60% of the surface area of the doctor bar forming screen used to produce this configuration.

7. The method of producing an intaglio printing surface as defined in claim 1, wherein step (e) embodies the formation of a doctor bar forming line screen configuration having a ratio of doctor bar forming area to printing area which is between the range of lz l and 1:2.

8. A method of producing an intaglio printing surface as defined in claim 1, in which step (a) includes the making of a screen diapositive from the original through a contact vignette screen having a screen formation of rod-shaped opaque screen elements arranged in a checkerboard pattern.

9. A method of producing an intaglio printing surface as defined in claim 1, wherein step (21) includes the making of two diapositives from the original through line screens, with the lines in the screen used to make one diapositive being arranged at an angle with respect to the lines of the screen used to make the other diapositive, and wherein said one diapositive is used for steps (-b) and (c), and wherein step \(d) includes the transferring of the configuration of both said one diapositive and said other diapositive, in superimposed relation, onto the printing surface to be relieved.

10. The method of producing a set of printing surfaces for multicolor intaglio printing as defined in claim 2, in which step (a) is performed by using a line screen having opaque lines formed as areas of gradually increasing transparency, and in which such screen is used as a contact screen in the making of each separate screened diapositive.

11. The method of producing a set of printing surfaces for multicolor in printing as defined in claim 2, in which step (a) includes the making of screened diapositives in which the opaque component of the screen is larger than the transparent component thereof.

12. The method of producing an intaglio printing surface as set forth in claim 1, in which step (d) comprises transferring the configuration of the retouched screened diapositive resulting from steps (a), (b) and (c) onto said printing surface by means of an electrical engraving device in which the range of the tone values is modified to reduce the tone values by a predetermined amount.

13. A method as defined in claim 12 in which only a certain portion of the screen elements of the screened retouched diapositive is photoelectrically screened and electromagnetically engraved into said printing form.

14. A method as defined in claim 12 in which the screened diapositive is formed by exposure through a line screen to cause the tone values thereof to appear in the form of continuous but separated lines, and wherein the transfer-ring of the configuration of the screened diapositive onto the printing surface is performed by scanning such screened diapositive at an angle of approximately 90 with respect to the lines of the screened diapositive.

References Cited by the Examiner UNITED STATES PATENTS 591,653 10/97 Levy 96-116 1,307,824 6/19 Larsen 96-116 1,375,659 4/21 Illig 96-116 1,460,744 7/23 'Boysen 96-116 1,919,481 7/32 Rowell 96-116 2,010,042 8/35 Stirling 96-38 2,039,195 4/ 36 Stirling 96-38 X 2,126,479 8/38 Landrock 96-116 2,159,588 5/39 Gorig 96-38 X 2,183,204 12/39 Reynolds 96-116 2,811,444 10/57 Wattier 96-37 3,085,878 4/63 Archer 96-118 FOREIGN PATENTS 16,447 12/03 Great Britain. 421,5 29 1/ 35 Great Britain. 770,864 3/57 Great Britain.

OTHER REFERENCES The Lithographers Manual, vol. 1, January 1958, Waltiven Publishing Co., New York, N.Y., pp. 11:1-11110.

NORMAN G. TORCHIN, Primary Examiner.

Claims

1. IN THE METHOD OF PRODUCING AN INTAGLIO PRINTING SURFACE FROM AN ORIGINAL HAVING A RANG OF TONE VALUES, THE STEPS COMPRISING (A) MAKING A SCREENED DIAPOSITIVE FROM SAID ORIGINAL REPRODUCTION, SAID DIAPOSITIVE HAVING THE FULL RANGE OF TONE VALUES PRESENT IN THE ORIGINAL SUFICIENT FOR MAKING A PROOF PRINT BY THE OFFSET PROCESS, (B) PRINTING BY OFFSET A PROOF OF SAID DIAPOSITIVE, (C) RETOUCHING THE DIAPOSITIVE TO CORRECT THE TONE VALUE THEREOF AS INDICATED BY THE OFFSTET PROOF, (D) THEN TRANSFERRING THE CONFIGURATION OF THE SCREENED DIAPOSITIVE ONTO A PRINTING SURFACE TO BE RELIEVED IN THE IMAGE AREA FOR INTAGLIO PRINTING, (E) FORMING ON SAID PRINTING SURFACE A DOCTOR BAR FORMING SECOND SCREEN CONFIGURATION HAS A DOCTOR BAR FORMING AREA AMOUNTING TO NO MORE THAN TWOTHIRDS OF THE TOTAL PRINTING SURFACE AREA, AND (F) RELIEVING THE PRINTING SURFACES TO FORM INK RECEPTIVE WELLS THEREIN ACCORDING TO THE COMBINED CONFIGURATIONS PRODUCED IN STEPS (D) AND (E).