US2373087A

US2373087A - Intaglio printing

Info

Publication number: US2373087A
Application number: US452036A
Authority: US
Inventors: Harley C Alger
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-07-23
Filing date: 1942-07-23
Publication date: 1945-04-10
Anticipated expiration: 1962-04-10

Description

Patented pr. 10, 1 945 UNITED STATI-:S7l larlzlv'r 'OFFICE MAGLMG y Barley C. Alger, Chicago, Ill. Y Application 23, 1942, Serial N0. 452,036 4 clams. (cl. 10i-401.1)

cally printing desired image from a diapositive onto the gelatine surface of a sheet of carbon tissue which has been sensitized with potassium bichromate, applying the tissue to the surface of a copper cylinder, developing the tissue with warm water, leaving that portion of the gelatine surface of the tissue which carries the design or image on the surface of the cylinder so that the gelatine when dry acts asa resist to the etching. The cylinder is then etched with ferric chloride to form the design or image. The` image so formed consists of recesses or'wells of varying depth, corresponding to the tone values of the image printed on the carbon tissue, surrounded or dened by lines or ridges oi! copper on the surface of the cylinder which were left due tol the action of the light when the screen was printed on the carbon tissue. These lines, ridges or elevations, serve as a support fox-.the doctor blade during the operation of printing, this'V method being well known in the art of making rotogravure printing .cylinders or plates. vSuch cylinders, however, have a number of disadvantagesv First: Thev copper surface of the cylinder soon wears appreciably due to the action of the doctor blade commonly used to remove surplus ink of the cylinder because copper is a compara-4 tively soft metal. As the surface, composed mainly of the lines or ridges supporting the doctor blade, wears, the tone values change as the lines wear down and the recesses or wells become more shallow so that the character of therprinting changes This often necessitates making a new cylinder to replace the worn cylinder causing extra expense and delay.

For making any subsequent printing "cylinder with an added layer of copper to bring its diameter up to its original size when it must `again be ground and polished before it is ready for use.

Third: As the acid etches away the copper lines or ridges of copper surrounding the recesses,

thus making these lines or walls of copper very thin and sometimes breaking them down completely by the time the etching of the remainder of the design is carried to a suitable depth. These very thin lines, walls or partitions give insuicient supportfor the doctor blade and short life for the cylinder. i

The objects of, the present invention are in general to improve such intaglio printing surfaces and to provide a new method of preparing the same which will serve to avoid manv of the objectionable features of such previous printing surfaces; to produce a plate or cylinder with an intaglio design which will be of a permanent nature while at' the same time one that will readily permit the replacing of one design with surface on the cylinder that has been used, it

is to grind on or otherwise remove considerable copper to remove theold image preparatory to making the new design on the cylinder but the cylinder is then slightly smaller than originally or reduced .in diameter, due to such v grinding. Or it may be n to replete the where both type and pictures or the like are etched at the same timeor where especially heavy or dark tones are required along with extreme high tones in the same design; and ingeneral to provide such improvements in intaglio or rotogravureprinting as will appear more fully hereinafter.

In the accompanying drawing illustrating this invention, Figure 1 is a plan view of the copper plate or surface before being acted upon;

Figure 21s a similar view showingin general v the arrangement of the wellsor-grid surface to be formed in the blade:

Figure 3 is an enlarged perspective view illustrating the ilrst steps of the operation; and

vFigure 41s 'a perspective view showing further steps in the operation in making the iinished surface of theplate ready to receive an image.

Figurev 5 is a-sectional detail 'illustrating the It win of course be understood that these ng` ures are more or less diagrammatic and enlarged as the actual screeningonsaid printing surfaces is of minute or microscopic character. As shown in the drawing, 5 represents a plat or body which may be either fiat or curved and which is made of suitable material such as copper for forming the printing surface thereon. In accordance with my improved method the surface of such plate or cylinder is polished and a carbon tissue resist on which has been produced any acceptable gravure screen without any image, is laid down thereon or applied thereto. The copper is then etched as with ferric chloride which ,will etch recesses or wells in the copper, leaving the surface of the copper in the form of lines or ridges corresponding to the clear portions of the screen. If a standard screen is used these lines will be in the form of a 'grid on the surface of the plate and there will be recesses corresponding to the dark or opaque portions of the screen. The etching is carried forward so that the depth of the recesses, which will all be substantially the same, is approximately .002 to .003 of an inch. When the plate has thus been etched it will have substantially the appearance shown in Figure 2 with cross lines or ridges I extending inone direction and other lines or ridges l extending in the other 'direction with wells or depressions 8 formed by the intersections thereof. This construction is also shown in Figure 3 on an enlarged scale.

After the surface has been formed into a grid in this manner, or in any other suitable manner, the recesses or wells 8 are filled with an inert material, such as beeswax, or asphaltum of the type having a high temperature melting point, such as indicated at 9 in one of the recesses only of Figure 3, and the surface is wiped clean, leaving only the copper lines or topsof the ridges 'B and 1 exposed. The surface is then plated with a suitable resistant metal such as chromium to the desired thickness of approxi-l mately .0002 of an inch to .001 of an inch as shown in Figures 3, 4 and 5. The chromium adheres firmly to the exposed copper lines or ridges and I find in practice that if the plating is carried out a suilicient length of time, the chromium will extend 'over the edges of the lines or ridges and plate a portion of the vertical walls of the lines or ridges as shown at Il -while of course not plating the 'bottoms of the cells which are' covered with the wax or asphaltum. The tops of the lines or ridges are then polished smooth, the wax or asphaltum is then removed, 'the wax by heat, or the asphaltum by dissolving with benzol, leaving the recesses empty of even depth, .002 to .003 of an inch, surrounded by copper walls capped over with-chromium as shown in Figure 5. y

The plate or cylinder in this condition forms a base or surface lfor subquent operations which may be repeated manytimes. My invention contemplates different methods of utilizing such grid surfaces in order to make a complete plate or cylinder ready to print.

In accordance with one of such methods, the outer surface of' the plate or cylinder, which comprises thechromium plated portions'. coated with wax vor photo-engravers cold enamel Il which covers or protects the chromium lines and the recesses .or depressions l are plated full of asvacsv will etch satisfactorily as'shown at I2, Figure 4. The whole surface of the plate or cylinder is then polished and leaves a smooth surface composed of hard chromium portions in the form of lines or grids with copper or zinc squares enclosed or surrounded thereby.

Or I may dispense with the photo-engravers enamel and merely platethe recesses until full of copper as the copper will adhere to the copper at the bottom of the recesses but will not adhere very well to the chromium on the ridges. The whole surface may then be ground and polished, the copper being easily removed from the chromiumed surfaces, and filling the recesses full level with the tops of the chromed ridges.

The image is then printed on a sheet of carbon tissue without screen lines and laid down on the surface of the plate or cylinder, developed and etched with any suitable etching reagent in the usual way. Ferrie chloride will ordinarily be used when the recesses are filled with copper. The etching acid will not etch or attack the chromium so that there need be no fear of breaking down these chromium-lines and more attention can 'be given to obtaining the required depth of etch throughout the design. Thus the metal in the recesses will be etched away in proportion to the tone Values of tire image printed on the carbon tissue. This leaves the recesses which had been completely filled, now partially filled with metal so that the unfilled or etchedaway portions of the recesses when supplied with ink will hold varied amounts throughout the entire surface in proportion to the tone value of the image.

Instead of filling the recesses in the surface ci' the cylinder by plating them with metals such as zinc or copper, they may be filled with a suitable amalgam such as one made of 30% mercury and 70% finely divided copper. After filling the recesses with the amalgam the surface is rubbed clear and smooth, allowed to harden and dry and is then ready to receive the image which may be etched thereon as above described. Other methods or suitable materials may also be used without departing from the scope of the invention.

From this description it will be seen that I have eliminated many of the disadvantages of prior processes and have produced an intaglio printing surface plate or the like which may be used over and over again as the chromium covered ridges or elevations will remain substantially fixed, being resistant to acids or the like which may be appliedtothe plate. Furthermore these chromium covered lines or areas will not be readily worn by the doctor blade but will last almost indefinitely when in actual use. After the plate has been used for one impression the de- Y pressions or recesses 8 may again be filled with copper or the like preparatory for using the plate again and such process may be repeated moreA o r less indefinitely.

A preferred process for carrying out the invention is to lay down on the polished copper surface a screen image of clear lines and areas provtected by a resist. 'This may be done by laying down on the copper cylinder the usual carbon tissue printed from a reverse screen having black lines and clear squares, then etching out the gravure screen lines to form grooves having a; depth of approximately .003 of anin'ch .with ferric chloride. then rolling up or coating the with a resist such as asphaltum or the like.

7 polishing the mince tneimagewbeened l "2,svs,o s7 Or the cylinder may be coated with sensitizedl albumen and the reverse screen printed on the n albumen which may then be developed, leaving the resist on the squares and the remaining resist may be -baked on so as to form a permanent resist, and the lines then etched out to form grooves or channels.

' The cylinder with the squares protected bythe resist is then placedin a chromium plating bath and subjected to the plating action until the etched lines or grooves are plated full of chromium to a level slightly above the surface of the copper. The whole cylinder is then ground and polished smooth, leaving chromium lines extending an appreciable depth into the copperv surface with copper squares surrounded by or defined by the lines.

The continuous tone image may now be laid down on the surface and etched without fear of damaging the lines. This utilizes the original couper of the cylinder to form the image and thereafter the recesses may be filled and renlled s as above set forth.

.sun another method is to muri the ebpper cylinder over its surface with a lfriurling tool having either one set of knurling ridges which will de press the copper forming a set of'parallel grooves running diagonally around the cylinder; or with a tool having two sets of ,parallel ridges, one set being at an angle to the other set in which 'case there will be formed two sets of parallel grooves formed in the cylinder. with islandV squares or diamonds of surface-.high copper surroundedby the grooves. Next. the cylinder is chromium plated until the grooves are nlled with chromium to a. height level with the original copper surface. Then the whole surface is ground in a grinder whichwill grind true and concentric down to the original coppersurface, removingall chromium ,from the copper Squares surrounded by a grid of chromium lines all surface high.

. .While I have thus described my improved plate or intaglio printing surface and method of makingthesame.Idonotwis htobelimitedto-the exact disclosure except as specifiedin the following claims. in which I claim: l

1. The herein described method off making a printing cylinder which consists in forming receases inthe-surface of a copper cylinder, then nilingtherecesseswitharesistantsuchaswax. then plating the unrecessed portions with chromium, thenremovingthe waxandfiliiugthereceases with copper. and finally smoothing and continued a vsuflicientlength of time so that the j 2. The process of forming a printing surface on a copper cylinder which comprises forming a screen image on the surface with intersecting lines defining a plurality of spaces, protecting said lines with a suitable resist, then etching out the spaces to form wells. then filling the wells with resistant material and chromium plating the lines with a plating of substantial thickness, and finally iiing the wells with copper and grinding and polishing the surface preparatory to receiving the images to be etched thereon, the arrangement beingsuch that the cylinder may be used repeatedly andthe chromium protected lines will serve to' resist the wear 'of the doctor blade.

v3. The method of' making a printing member of copper which consists in forming recesses in the surface of the member which are denned by a plurality of intersecting walls, then filling the recesses with a resistant such as wax, then plat.

ing the unrecessed portions with chromium and continuing' the plating until the chromium extends down onto the sides of the walls of the r, then removing the wax and lling the recesses with copper and finally preparing the surface for receiving the matter to be etched thereon.

4. The process of preparing a copper cylinder i for use inintaglio "printing, which consists in applying a carbon tissue resist produced by means of a gravure screen, to the surface of the cylinchromium will extend overthe' edges and on to u the vertical sides of the walls, thereby providing preparatory to receiving thereon i substantial caps for the outer portions of the walls, then removing the resist in the wells, then A coating the chromium plating with a resist to protect the walls. then lining the wells with a suitable metal such as copper which is adapted tobeetchcdintheusualmannenthenpolishing the surface of the cylinder leaving the surface smooth with lines of chromium enclosing squares ofcopperortheiike.

HARLEYGALGIR.