US967875A - Process for producing printing-plates. - Google Patents

Description

' E. ALBERT.

PROCESS FOR PRODUCING PRINTING PLATES.

APPLICATION FILED 1330.4, 1908.

967,875. Patented Aug. 23, 1910.

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Be it'known that I, EUGEN AIlBER'r, a subject of the-Emperor of Germany, residingatMuni'ch, in the Kingdom of Bavaria and Empire of Germany, .have inventedcertain new and useful Improvements ina Process for Producing Printing-Plates, of-Which-the followingis a specification.-

This invention relates plates byetching.

V lhe objectsof thelinvehtion are to sim-. plify :the etchingprocess to" render it less -,-olependent upon the personal skill of the Re -worker, and to economize time.

'Ehe copies required in thezpreparation of {photo-mechanical printing blocks have here- ,tofore been made almost exclusively bymeans --::fofbichromate films; if thebichromate film wsis' on;eopper,'-it-is burned-in to form anenamel :and itself: constitutes the resistant etching film. As the high temperatures re- 'Zquiredr for this nprocess aprejudically affect ;m'et'als other than copper, such for example as :zinc,: the filrn' of bichromate (generally albuminbichromate) is only-utilized indirectly. as support for another etching ground, 'by coating .1t,;after' the copying, with van etching ground, generallyv by rolling-in an 4, appropriate ink, whereuponthe unexposed parts w1th the etching ground deposited ythereonrarei developed with waterrand rubbing with cotton :wool, 1 and-then, after drying, the-covered parts ofthe 1 plates are 1,:dusted with powdered resin and 'melted-on. -i-This latter process doeshnot give as good results as when the 'bi'chrornate film 3 itself is used as the etching ground, as the'rolling- :in r of the ink, thezmanual development with 40: cotton ,wool,-the dusting with resinaand' the melting-on, .impairzthe smoothness and fine-',

-ness of the tone, especially in the case of delicate autotypes. Attempts havethere- "fore been made to'applythe'etehingground to the subsequent printing 'surface imthe "first place, then prepare this etchin ground with a'bichromate film, to copy an develop/as usual, and thento utilize'vthe bichromate film as a protecting film a'gainst the: solvents for the et'ching'i'ground. The

' processamost nearly resembling thi's heretm forecemployed is idescribed by 'Husnick as consisting :of: pouringoven ia metal plate a loittlmen .soluti'on prepared in turpentlneand henziniepor in 'someother etheric oih and then: treatingrthe bichromate topy w'ith a Specification oi. Letters late nt. Application filed ne ember'e, 199s Serial no. 466,005. 3

PatentedAug. 23; 1251c.

flmixture of two parts'of olive 'oilxand one .part of turpentine oil by rubbing the metal rrnn erm ne ieA'rEN'r onrrono v plate until thebaredgbitumenis washed 0E i and the metal appears clean. The plate then'lwashed with soap and'waterwind 1t 1s endeavoredto rub the bichromate coating Jaway socarefullythat'the bitumen beneath r ;it-is 'not: injured. The bitumenis sufficient to an improved Wprocess for the preparation of printing the defects ofthat process and attain a satisfactory result, 'it is first of all necessary to prevent the solvent from soaking through the bichromate :film, which is of course very thin, as otherwise the etchingrgrou'nd would also be dissolved-at. places where itrshould .-.be protected from the solvent by the bichromate skin. This-condition can only be fulfilled.-by atsolvent of considerable consistency viscosity, so, that it will not penetrate the ,lunremoved portions of the bichromate skin before theetching ground has been-dissolved :tat theexposed placesyetheric oils will not .give thisi'result as -theyfare "of .el'ow con-f sistencyi On the other hand the-capacity of 'a mixtureuof-turpentine' oil andoolive o1l v to vact asaa solvent is so small: that. the dissolving 'prooesstmustfl-be .,assisted by. rubbing with cotton wool, which-'lmanual operation requires personal skill and entailasouroes ot .error, like the :bichrornateralbuminz recess,

the avoidance of: which islzthejvery ab feet-35f:

the process. :Itl=is=also;mecessary that 'when the etching ground has dissolved. :on the placesv not protected: :by the bichromate skin,- it should beiz-possible toswash the-dissolving liquid or-dissolving mixture "from rthefplate speedily and thoroughly, as of scoursegin spite of the consistency of the solvent, in thecourselof: a considerable period 0f; time the solvent would: penetrate the remaining portions of bichromate skin; The cleaning-off ofithefl-olive oil mixture with soapr'and: water, which isadvocated by Hus'nick 'forl the purpose of cleansing the a metal pl'atesti from the fatsbis of course not well'adapted tm interrupt suddenly the dis.-

solving 'iprocess, if only 01? thereasonthat the soap. -do'e'sainotqexert its' action imrnediatelyihpon the fatty substances, apart f-rorn' the interruptiOn-of -the dissolving ac- ;ti'Qn short 1 actwn of ike 1 soap and water does not even pr'oduce :a thforou'gh cleansing i 0fiatll6riplate,' while if; the soap and water selected, all

allowed to act for any length of time it readily penetrates the bichromate-skin and attacks the bitumen beneath it, as is clearly apparent from Husnicks statement that 15 bodies, as they readily dissolve in alcoholic liquids; for the greater parts tliese liquids mix readily with water in all proportions, and, for reasons of economy, water alone is i also used for removing the solvent from the plate as speedily aspossible. .Alcoholic liquids can also be very readily thickened with bodies which are soluble both in alcohol and in water, and which, such as tannic acid for example, even tend to harden the 2 5 bichromate skin; llijlSfllSO possible to in- ;crease the dissolving power of the'a'lcoholic of acids or bases, on the one hand by the formation of the so-called esters and on the other hand. by the formation'of resinates.

' Alcohol also mixes in all proportions with glycerin,'which is the most consistent liquid in existence, and which again is soluble in water in allproportions'; if'etheric oils be these favorable factors are excluded completely. i t Broadly this invention consists in using alcoholic solutions of considerable consistenc'y and highsolvent capacity so that the etching ground readily dissolves if the are merely poured over the plate, or if, it be immersed therein, before the solvent has fil tered through the unremoved portions of the bichromate skin, and in quickly interrupt- 45- .ing the dissolving process by bringing the plate at the proper moment beneath a water pipe, preferably provided with a distributing rose.

For a more exact exposition of the inven tion a drawing is made a part of this specification and init there is graphically re resented sections of a plate indicating di erent stages in its preparation. i

Figure 1 represents the plate with first coating applied; Fig. 2 represents it with the second coating applied to the first coatg; Fig. 3 shows the prepared plate with portion of the second coating removed;-and Fig. 4 shows it with corres ,onding portions 6 of the first coating removed The particular steps of the process and the materials preferred areas follows Fir st,-' the base plate Z is covered with resin to form. an etching ground E, next a bichromate film B is deposited over the whole,

dissolving liquid by adding small quantities subjecting and the copy formed by exposing to light the plate thus prepared and then dissolving in water the soluble-portions of the gelatin or bichromate film .,from between the dots, leaving the insoluble portions or dots as in Fig. 3; -the plate is then immersed in a liquid consisting of alcohol which has been thickened by the addition of tannic acid or glycerin, or both, to strengthen its dissolving power., This readily dissolves the exposed parts of the resin from the plate Z, Fig. 4,1theother parts being protected by the bichromate film, and as soon as that is accomplished the dissolving process is instantaneously stopped and the plate cleansed 30 by bringing it at the pro or moment beneath a water pipe provide with a distributing spray, the plate being then ready for the etching bath. By this means it is ossible to' make an impression from the p ate 35 after the preliminary etching, to free the plate from the residue of ink adherin to it by means of benzin or turpentine an drying it with sawdust, and then for the re touching final etching undergone without rolling-in, fresh ink, dusting with resin powder. and to heat as has been necessary in processes employed hitherto which frequently gave use to error and loss of tlme. Besides economizing time the results are more certain since the positive printing elements are still covered with the original etching film when the plate is operated on by the retoucher who is therefore certain that the desired effects will be obtained in the final etching.v These advantages apply equally when the plate, instead .of being .etched, is gummed and treated as a lithographic plate. 1

' An important advantage obtained by using1 alcoholic substances for the etching groun is found in the fact that there are a number of alcoholic resins to choose from which do not dissolve in etheric oils. sandarac is insoluble in benzin, or turpentine.

A plate on cheap metal can be obtained bythis. process giving results equal in quality to those of a copper plate.

What I claim as my invention and desire to secure by'Letters Patent is':-

1. The herein described process of treating printing plates, which consistsjin covering the plate with an etching ground which is insoluble in the substance used for cleansing the plate after preliminary etching, over laying the etching ground with a sensitized film, then photographically transferring the copy thereto and washing away the unaffected portions of the film with water, dissolving the etching groundwhere not covered by the copy by means of a liquid or considerable consistency or viscosity, andquickly interrupting the dissolving process process to be carried out and the 90 For instance 1 0 t 7 when complete by removing the solvent with a liquid Which will not dissolve theetching I printing plates, which consists in covering the plate with an etching ground of a resinone substance; coating this with a bichromate film, photographically transferring the copy thereto and washing with water, and then subjecting the plate to the action of an alcoholic liquid readily miscible'with water, substantially as and for the purpose'set forth. A

3. The herein described process of producing printing plates, which consists in covering the plate with an etching ground of a resinous substance, coating this with a bichrolnate film, photographically transferring the copy thereto and washing with Water to remove the soluble film, then subjecting the plate to the action of a solution of alcohol to which have been added glycerin and tannic acid, quickly stopping the dissolving process when complete by holding the plate beneath a Water spray -and finally etching the-plate thus prepared; substantially as described herein.

In testimony whereofI a'flix my signature in presence of two witnesses.

' EU GEN ALBERT. Witnesses: I

LOUIS L'MU'ELLER, MATHILDE K. HELD.

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