US1901468A - Method of producing photogravure plates - Google Patents

Description

Patented Mar. 14, 1933 PATENT OFFICE AXEL A. PEARSON, OF KANSAS CITY, MISSOURI METHOD OF PRODUCING PHOTQGRAVUBE PLATES No Drawing. Application filed July 13,

This invention relates to the process of producing photogravure plates to be used in making photogravure prints, and the invention contemplates processes which are dirooted to two distinct methods, each of which is used to produce a particular type of plate.

The primary object of the instant invention is to provide a series of steps in a process of producing photogravure printing plates which obviates the necessity of using the commonly known gravure tissue, which process includes the employment of two distinct transparent positives applied in the process in a manner to create on the metallic printing plate, two superposed coatings,-the

' first layer performing its acid-resistingfunction and, combining this function with the other coating, which is fluid-penetrable,

in a unique manner to produce an especially high grade gravure plate which requires a minimum amount of re-touching.

A yet further object of the instant invention is to provide a new process of producing photogravure printing plates which may be practiced by those less skilled in the art, and which allows for the production of a more perfect printing plate within a time much less than that now required for the making of plates of this character.

' One of the objects of the invention is the provision of a process for producing a duotype photogravure printing plate, .wherein is an area having no middle or half tones,

but which is present for the production only of lettering or similar areas of deepshadows formed upon a white or high-light background. This specific phase of the invention is particularly novel in that the high- 40 light or white ground around the lettering or deep shadows is always true, the outline is clean cut, and there are no ragged edges present. This particular area of the plate is for the purpose of what might be called typographical printing, which printing is to be done simultaneously with the production ofthe printing of the photogravure, ,and the invention here contemplated applies to this area to a further extent in that there are permitted no foul bites.

1931. Serial N0. 550,622.

Since the ordinary process of producing photogravure printing plates is well known in the art, and since, also, the steps in well known processes are clearly and definitely set down in many existing patents and publications, it will be necessary herein to illustrate only the conventional lnstrumentalities utilized in the process.

The steps in the well known and common process of producing photogravure plates consist in brief of the following:

1. Photographing the image to be reproduced in photogravure to make a'continuous tone negative.

2. Make a transparent positive from this negative.

- 3. Apply by printing upon the well known sensitized gravure tissue an ordinary cross line gravure screen (contact printing).

4. Contact print the positive made in step 2 upon the gravure t ssue upon the cross line just printed thereon.

5.' Transfer the emulsion or coating from the gravure tissue to a copper base or plate and peel off the'tissue sheet.

, 6. A copper base with emulsion adhering ghereto is developed and washed until ready or use.

7. After drying, the copper plate having the developed emulsion thereon carrying -a reproduction of the image to be reproduced is submerged in etching fluid and made ready for the application of ink.

These steps'are understood and are set down merely to make clear'the improvement and advantage inherent in the process contemplated by this invention. Explanation of the process of producing photogravure border whereby no etching is ever allowed at the opaqued area and a bearer is'formed.

The next and third step is to produce a transparent positive from each of the negatives made as in steps one and two. These positives may be on film or glass and the same'are developed and dried in ordinary photographic fashion.

The fourth step in this process of producing 'photogravure printing plates is to produce a pre-coated copper plate which is to be the actual printing plate. The coating is a sensitized film of solution, against which the screened positive is placed and light passed therethrough to the sensitizing of the copper plate as the ordinary contact exposure is made.

After such printing, the exposed copper plate is developed, which action produces a printing plate having an acid-resisting ground, which ground has the image to be reproduced formed as a part thereof, and, in addition, a well defined screen over all areas in opaque which actually performs the duty of masking to set off, upon the copper plate, well defined areas which confine the etching action and serve as a wiping bearer during printing.

After this particular step just mentioned has been completed, the invention requires that another sensitizing coat be flowed upon the coating now on the copper plate. This superimposed sensitized coating is allowed to dry, after which the continuous tone positive is contact printed thereupon. That is to say, light is passed through the continuous tone positive to act upon the second sensitized coating, after which developing of the second coating must take place to produce a coating of varying thickness which directly overlies the first coating, and which is devoid of screen markings of any nature. When this step of printing the continuous tone positive takes place, it is absolutely necessary that the lines of the image to be reproduced be caused to register exactly. It is notable at this point that the last mentioned superimposed sensitized coating is used in lieu of gravure tissue, 'the use of which so often creates trouble in the rapid production of photogravure plates.

As the next step, the copper base now having two coats of resisting material thereon is etched in a solution of copper dissolvent which attacks and eats out the copper plate to different depths for the purpose of forming ink pockets to receive the ink when the plate is in actual use. i

The advantages of the process just set down here becomes apparent when an understanding is had of the action upon the copper plate by the dissolvent. In practice it is found that the dissolvent acts upon the plate to different depths, depending upon the thickness of the last coating of resisting material which was produced. The thinner portions of this last resist allows the copper dissolvent to reach the lowermost coating first, where it is confined to areas set off by the well defined screen above described.

When the dissolvent reaches an area confined by said screen it is definitely masked or separated into zones, and the copper plate intensely attacked over this set off area. This action is carried out throughout the entire face of the printing plate, all commensurate with the thickness of the top coating and confining qualities of the first or lowermost coating;

After etching as above, the second or top coating is washed off, leaving the first or lower coating present which may be utilized for procuring a proof which in turn may disclose any need of local reetching with brush or the like. This lower coating is then removed.

Obviously, ink pockets are effectively controlled through the process just set forth and it is to be seen that a finer graduation of tone is possible. The expense of producing such plates is less than the ordinary well known method or process now in use and spoilage is reduced to practically nothing. Handling and retouching the plate in preparation for actual use is obviated and in all, the process produces a result not attained in any known manner.

Where a print is to have thereon a typographical area or an area limited to high lights and deep shadows, and where it is desirable to print the entire plate including both this area and the area including all tones from high lights down to shadows, it is appropriate to use the process just defined and to supplement the steps of this process by a treatment as follows: I

Step 1 in this process is the same as step 1 next above, but the lettering or typographical area is blocked out with black paper having a screen marked thereon so that the negative which reproduces the image will have a substantially clear area marked throughout by a well defined screen. Step 2 likewise includes photographing the image to be reproduced with a screen in front of the plate to make a screened negative. At this point this screened negative is acted upon to the extent of removing therefrom all of the coating or emulsion lying within the typographical'area. Here an additional step is to be followed which consists of making a regular line negative of the lettering which is to appear in the typographical area, said negative being large enough to include all of the area in question. In any desired manner this line negative of the typographical area' is placed in position at the proper point, or exactly where the emulsion of the screened negative was removed for this purpose. Thus a built-up negative is produced.

, Step 3 includes, as hereinbefore set down, the production of a transparent positive from each negative. It is to be remembered at this point that one of these positives will have the typographical area without lettering of any character but with the screen thereon, the other positive which is made from the built-up negative will have the typographical area with the desired lettering and with an overlying screen. From this point on the relation between the two positives and the metal printing plate is the same. When the plate is finally produced the white ground around the lettering in the typographical area will be true, there will be no ragged edges around the letters, and the letters will have a clean cut outline the same as though they had been separately printed.

This last method is unique in that the face of the letters in the typographical area will not have screen markings extending as high as the area around the letters. The application of ink to the depressedlor eaten out part of the printing plate which is to form the letter itself is, however, provided with a screen tooth extending upwardly from the bottom of the pockets just sufficient to create gripping members so that regardless of the size of the face of the letters, the ink will be positively and uninterruptedly applied and no voids will be left when the offset takes place.

For obtaining plates engraved in relief, for typographic printing, the process is the same as just described for making printing plates, engraved in intaglio, but in that case negative originals are used.

While the precise technique of making photogravure printing plates has not been set 'down in detail, it is to be understood that the process has been made clear beyond a doubt through the foregoing description.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. The process of producing photogravure printing plates which comprises twice photographing the image to be reproduced to make a continuous tone negative and a screened negative; producing a transparent positive from each negative; exposing the presensitized printing plate to light passing through the screened positive; developing said plate to establish an acid-resisting coating; sensitizing said printing plate directly over the coating; exposing said last sensitizing coating to light passing through the continuous tone positive, with the images on.

the plate and'continuous tone ositivein register; and then etching sai printing plate in a solution of co per dissolvent.

2. The process of pro ucing photogravure printing plates which comprises twice photographing the image to be reproduced to make a. continuous tone negatlve and a screened negative; producing a transparent positive from each negative; exposing the pie-sensitized printing plate to light passing through the screened positive; developing said plate to establish an acid-resisting coating having areas set off by well defined screen markings; again sensitizing said printing plate directly over the said coating; exposing said last sensitizing coating to light passing through the continuous tone positive, with the image of the plate and continuous tone positive in register; developing the last coating to produce an acid-resisting coating of varying thlckness superimposed upon said first coating; and etching said printing plate in a solution of dissolvent, said etching solution penetrating the said plate as permitted by the last proin register; the lowermost {coating being formed through the said positive made from said screened negative, the top coating being formed through the said positivemade from the continuous tone negative, both coatings being developed before etching said plate whereby said etching action is confined to definite areas and caused to act to varying relative depths.

4. The process of producing photogravure printing plates having an area thereon limited to high lights and deep shadow tones which com rises photographing the image to be repro. uced with said area thereon covered with a sheet of black material having a screen marked thereon to make a continuous tone negative; again photographing the same image through a regular screen to make a screened negative; removing from said screened negative the area defined by said black material; making a lined negative of said area only and insert in space created by removal of the said area on said screened negative; producing a transparent positive from said continuous tone negative and said screened negative as altered; and then producing a printing plate from said transparent positives.

5. The process of producing photogravure printing plates having an area thereon limited to high lights and deep shadow tones which comprises photographing the image to be reproduced with said area thereon covered with a sheet of black material having a screen marked thereon to make a continuous tone negative; again photographing the same image through a screen to make a screened negative; removing from said screened negative the area defined by said black material; making a lined negative of said area only and insert in space created by removal of the said area on said screened negative; producing a transparent positive from said continuous tone negative and said screened negative as altered; exposing the pre-sensitized plate to light passing through said screened positive; treating by developing said plate toproduce an acid-resisting coating; re-sensitizing said plate over said coating; exposing said re-sensitized plate to light passing through said continuous toned positive; and then subjecting said plate to A the same image through a regular screen to.

etching action whereby the deep shadow tones of said area are unbroken by screen lines and said highlight portion is free of ink supporting pockets.

6. The process of producing photogravure printing plates having a area thereon limited to high lights and deep shadow tones which comprises photographing the image to be reproduced with said area thereon covered with a sheet of black material having a screen marked thereon to make a continuous tone negative; again photographing make a screened negative; removing from said screened negative the area defined by said black material; making a lined negative of said area only and insert in space created by removal of said area on said screened negative; producing a transparent positive from said continuous tone negative and said screened negative as altered; and then producing a printing plate from said transparent positives by exposing the pre-sensitized plate to light passing through the screened positive and said continuous tone positive, and then etching said plate.

7. The process of producing a photogravure printing plate which consists in applying to a screened negative ground on said plate, a sensitized coating; exposing said coating to light passing througha continuous tone positive of the same image, the images of both negative and positive being in register as exposure is made; developing the exposed sensitized coating to create a film of varying thickness over said screened negative ground; etching said plate in a solution of dissolvent, said etching solution penetrating the said plate as permitted by said film of varying thickness and the spaces between the acid resisting ground of said screened negative; and removing said film of varying thickness and said screened negative ground from the plate.

8. The process of produclng photogravure printing plates which comprises twice photographing' the image to be reproduced tizing said plate over the face of said plate over said spaces of like area; exposing said last sensitizing coating to light passing through the continuous tone positive; developing said last coating to produce a fluidpenetrable coating of varying thickness overlying said acid-resisting coating; etching said printing plate in a solution of dissolvent to produce a multiplicity of spaces of like area throughout the face. of said plate, said spaces varying in depth to re- .tain varying volumesof ink when the plate is used in printing.

In testimony whereof, I

hereunto aflix my signature.

AXEL A. PEARSON.