US2506164A - Method for the production of metallic printing members - Google Patents

Description

May 2, 1950 J. E. MORSE 2,506,164

METHOD FOR THE PRODUCTION OF METALLIC PRINTING MEMBERS Filed Oct. 15, 1947 INVENTOR. L/a/m f. /70/P5 Patented May 2, 1950 METHOD FOR THE PRODUCTION OF METALLIC PRINTING MEMBERS John E. Morse, Brooklyn, N. Y.

Application October 15, 1947, Serial No. 779,844

7 Claims.

This invention relates to the production of metallic printing members such as plates or cylinders.

According to this invention a convenient, economical and accurate method is afiorded for depositing in areas of predetermined outline on a printing member presenting an aluminum surface electrolytically deposited metal selected from the group consisting of copper and nickel.

The method of this invention is excellently adapted for the production of printing plates for planographic or lithographic printing. In planographic or lithographic printing a printing plate is employed having a substantially flat surface presenting portions which have different selective attraction for printing ink and for water. The portion having selective attraction for printing ink consists of areas of predetermined outline such as letters, designs, halftone prints, or the like. By first applying water to the plate, the surface areas having preferential affinity for water become moistened, and, upon subsequently applying printing ink, the ink does not adhere to the surface areas having preferential affinity for Water while it does adhere as a coating upon the printing areas of predetermined outline having a preferential aflinity for the ink. Upon application of the inked printing member to the surface of a paper sheet, for example, printing conforming to the printing areas of predetermined outline is transferred to the paper.

In the preparation of printing plates for planographic or lithographic printing, plates composed of aluminum have been'extensively used due to the fact that aluminum, especially after having been subjected to mechanical or chemical graining, has a very pronounced preferential attraction for water as compared with printing ink. This afiinity for water is further improved by etching the plate with a lithographic etch such as gum arabic solution and phosphoric acid, which leaves a deposit or film more capable of retaining water on the plate. In order to provide areas having preferential attraction for printing ink, lacquer coatings, coatings of egg albumin sensitized with dichromate and hardened by light that are covered with a greasy ink, or greasy ink images drawn or transferred directly on the plate have been employed, but such means for providing areas having preferential attraction for printing ink have the disadvantage of wearing away quite rapidly so that only relatively short runs are possible using a given printing plate. Moreover, in order to retain the water reception areas effective for thispurpose during operation of the printing press it is necessary to add etch to the damping solution in the fountain. This etch, if strong enough, will attack the greasy image or the lacquer base providing the ink receptive areas causing the image to wear or fade away. If, on the other hand, the etch is not of sufficient strength it will not prevent spreading of the image into the non-printing areas.

It has also been proposed to coat a printing plate such as an aluminum printing plate with an over-all coating of electrolytically deposited copper or other metal which has a preferential attraction for printing ink as compared with water. After the over-all copper coating has been applied, the desired image is superimposed on the coating in the form of a suitable masking that is resistant to the action of nitric acid and the non-printing areas of the copper coating are dissolved away by the action of nitric acid leaving the aluminum surface of the printing plate exposed in the non-printing areas. In this manner more durable printing plates can be produced as compared with printing plates wherein the printing areas are provided by lacquer coating, but the method of producing the plate is very wasteful of copper for both sides of the aluminum printing plate are coated over-all with copper and later the greatest part of the copper coating is removed by the action of the nitric acid. This method also has the disadvantage of not being reliable in the production of accurate printing areas for there is the danger, especially in the case of delicate half-tone work, that the delicate layer of lacquer or enamel which protects the printing areas during the dissolving of the copper with nitric acid will be undermined. Moreover, the use of nitric acid to dissolve away the copper from the non-printing areas is attended with the development of fumes which are injurious to health and which are very objectionable especially in view of the fact that when the nitric acid is used in the amount necessary to dissolve away the copper from the non-printing areas of a printing plate, very severe fuming occurs.

It is a purpose of this invention to overcome difliculties of the character aforesaid and afford a printing member such as a plate or cylinder which is capable of use in connection with extremely long printing runs. In fact according to the method of this invention the production of a printing plate suitable for planographic or lithographic printing can be controlled so that the plate will be suitable for printing runs of any desired length. Moreover, in the practice of this invention the image areas produced on the 3 printing plate consist of metal which is not affected by the etch in the damping solution and permit the maintenance of the etch in the damping solution at sufficient strength to prevent the image from spreading without any danger of the image fading or wearing away.

According to this invention a printing member such as a plate or cylinder which presents an aluminum surface is first covered with a suitable masking material except for areas of prede-. termined outline which are left exposed. The areas of predetermined outline, as stated above, may be in the form of letters, a design, a halftone print or the like, depending on the subject-matter to be printed. A suitable etching solution is next applied to the surface which etches theexa. posed areas of predetermined outline. masking material is then removed from all of the surface, leaving both the unetched aluminum surface and the etched areas exposed. The printing member is then placed in an electroplating bath adapted to deposit a metal selected from the group consisting of copper and nickel and issubjected to electroplating. I havediscoveredthat upon receiving the electroplating treatment, the. metal from the. electroplating bath becomes selectively adherent only to the etched .areas'of the aluminum surface, leavingv the unetchedportion of the aluminum surface exposed and, as a result of the electroplating treatment, the metal becomes deposited as an integral coating firmly adherent on the etched. areas of the aluminum plate, the thickness of the coating being dependent upon the duration of the electroplating treatment.

As a result of the foregoing process steps, plates suitablefor planographic or lithographic printing can be. prepared, for the metals copper and nickel exhibit afllnity for printing ink as compared with water and provide printing areas while the uncoated aluminum exhibits selective method of this invention that the metal can readily be deposited so as to provide printing plates or the like that have extremely long liftl' In fact, the method of this invention not-only may be employed in the productiohbfplatee, cylinders or the like, suitable for planographic printing, but, also, by building up the thickness of the depositedmetal may be employed to provide printing plates or other printing members appropriate for use in type printing, Alternatively, by deep etching followed by electroplating to deposit copper or nickel in the etched areas below the level of the surface of theunetched areas,a printing membersuitable for intaglio printing can be produced.

In order to afford a better understanding of the practice of this invention it will now be described in connection with a specific example of the practice thereof in the production of an aluminum plate suitable for the planographic or. lithographic printing of a photographic image.

The image to be reproduced may be originally...

produced in the usual .wayby firstpreparing a.

The

4 photographic negative and then producing a halftone positive through a halftone screen. An aluminum plate of the type that is conventionally employed on a printing cylinder is first treated to produce a grained surface. A pure grade of aluminum is desirable, that of 2S purity being preferable. The graining is preferably accomplished by a chemical graining treatment, that treatment disclosed in my application $erial No. 757,718, filed June 23, 1947 for 'Graining plates being especially suitable. The purpose of the graining of the aluminum is to provide a surface which in the finished plate will be highly receptiveto water as compared with printing ink. "The graining of aluminum plate is not essential,.however, to the process of this invention, Alternatively the aluminum plate may merely be cleansed as by treating it with alkali followedby nitric acid so as to remove surface contaminations and provide a uniform surface. Mechanical grainingordinarily is not employed inasmuchas the mechanical "grainingi's likely to contaminate the aluminum surface, which is un desirable unless the plate is thereafter chemically treated to remove the contamination.

The surface of the aluminum plate to be usedfor printing is coated with a layer of dichrorn-,,

ated gum arabic sensitive. to light. Asuitable formula .for this purpose,. which is extensively used, is as follows:

Water c. c 1000 Theforegoingformula is typical of what is commonly known as, a deep. etch sensitizerv coating, due to the fact that it stands up under.

intact For this purpose, there maybe used a.

developer solution of alkaline earth salt, such as calcium chloride, and. an organic acid such as lactic acid, e. g., a solution consisting of 1000 c. c. of 37 Be. calcium chloride and 40 c. c. of.

lactic acid is suitable for the purpose. calcium chloride acts as a carrier which prevents The.

solution. of the light exposed areas of the coating while. the lactic acid. dissolves away the image areas that were unexposed to light.

The plate prepared, as above described, is covered with the deep etch sensitizer coating in the non-printingarieas while the printing areas, as determinedby the positive used, are-left exposed. The next step consists in treating the surface of the plate with an etching solution, a suitable formula-for the purpose being as follows:

Calcium chloride solution 40 B- c. c i830 C uprous chloride grns Hydrochloric acid (C. Rsp. gr. 1.19) c. c

The etching solution is applied for about two minutes and attacks the-exposed printing areas of the aluminum plate. Its function. is primarily that. of removing aluminum oxide film and rendering the etched surface receptivetc the subsequent electroplating, step.- Anetching bath such as that of the foregoing formula is preferred inasmuch as the etched surface of the aluminum acquires during the etching a very slight stain of metal (copper in the case of the foregoing formula) which serves to preserve the ing can then be readily accomplished merely by V washing with water. If desired, the washing with water may be followed by citric acid in order to remove all traces of the gum arabic, the plate being scrubbed to assist in the removal of the gum arabic, which, if present, would result in deposition of copper thereon during the electroplating step and would contaminate the electroplating bath.

The plate, prepared as above described, is now ready for copper electroplating. A suitable formula for the electroplating bath consists of- Copper sulphate -gms 240 Sulphuric acid (sp. gr. 1.84) c.c 35 Water c. c 1000 Gelatin gm .02

The electroplating is accomplished using a current density of about one ampere per square decimeter. The copper deposited from the electroplating bath adheres only to the etched image areas of the aluminum plate and forms a coating the thickness of which depends upon the duration of the electroplating step. A slight scum of copper sometimes develops over the non-printing areas of the aluminum plate, but any such scum can readily be removed by rubbing it off, by reverse plating; or by etching it off with nitric acid. The resulting plate presents a bimetallic surface, namely, the areas of predetermined outline corresponding to the image on the positive are coated with copper while the balance of the plate where the aluminum is uncoated remains exposed. If desired, the electrolytically deposited copper can be buffed so as to increase its selective affinity for printing ink in comparison with water.

Printing plates produced, as above described, provide extremely true reproduction of the original positive down to the finest tones and the finest mesh halftone screens can be used. The process of this invention has been successfully employed in the production of colored reproductions employing a plurality of halftone positives of the image, each positive having been produced for the printing of those image portions corresponding to a given color. Extremely accurate colored reproductions have been produced in this way employing separate plates for each of as many different colors as may be required in making the colored reproduction.

The sequence of steps employed according to the above described example of the practice of this invention is indicated diagrammatically in afcoating ll of'light sensitive dichromated gum arabic applied thereto, the thicknesses being ex-,

aggerated for clarity in this figure aswell as in" the other figures. Fig. 2 illustrates the condition of coated plate after the layer has'been ex-" posed to lightthrough the positive and after the areas unexposed to light corresponding to the image areas on the positive have been removed,

leaving the exposed areas I2 of predetermined outline. Fig. 3 illustrates the condition of the plate after the plate has been etched in the exposed areas, leaving the etched image areas l3, while the balance of the plate is still protected by the coating H.

v Fig. 4 illustrates the condi-' 'tion of the plate after the masking coating ll has been removed, leaving the surface of the aluminum plate' entirely bare. However, the surface of the aluminum plate is characterized by' the etched areas [3 having the outline deter-- mined by the image to be reproduced, the balance 4 of the surface being unetched. Fig. 5 illustrates:

the condition of the plate after the electroplating step. It-is to be noted that a coating [4 has been integrally applied only to those areas which had previously been etched. The copper, as thus 1 deposited, exactly reproduces the image areas 1 corresponding with the image areas of the original positive and no copper becomes deposited elsewhere on the aluminum plate.

In the figures shown in the drawing the depth of the etching and the thickness of the coating [4 of copper have been exaggerated for the purpose of clarity in the drawing. Thus the coating [4 of copper, even when applied so as to be capable of extremely prolonged printing runs, can be such that the plate surface is virtually flat and suitable The tioned above, to deposit the coating 14 of copper to such thickness that the printing plate can be used for type printing or to etch the areas l3 to such depth that the coating I4 of copper will be below the level of the unetched areas, thus producing a printing member which can be used for intaglio printing.

The printing plates used for planographic or lithographic printing are ordinarily in the form of relatively thin aluminum plates or sheet-like bodies that can be secured to the surface of a printing cylinder. However, it is apparent that printing plates suitable for use in a platen printing press can be produced according to this invention. Moreover, the process of this invention also is applicable directly to the surface of a.

printing cylinder. If desired, in the practice of this invention, each side of an aluminum printing plate can be provided with a different image or other printing surface.

While the practice of this invention has been illustrated in connection with the preparation of a printing plate from a photographic positive utilizing a light sensitive coating, it is apparent that this invention can be practiced in other ways and that all that is required is that a suitable masking coating be applied over the surface of a printing plate presenting an aluminum surface, the coating being resistant to a solution adapted to etch the aluminum and the masking Locating-having openings therethrough through bellproduced mechani cally.. If the openings arej producedmechanically', itTis o'f course the case" that the masking coating-.neednot 1ght'.sensi tiveiand. may for examplebe fa suitablellacgiiier orenamel. M

For etchingthe areas of aluminum surface any. .10 of a variety .of-knownetching solutions may be employed. Thus, the case of the etem gsq a tionv .ofjithe foregoing example, fthe proportions can be considerably varied and for 1000- c. c. of nfl ws kim'n p i es u n hefa e ai' of cuprous chloride can be varied between about 2 emia d qu ewmsw ile:t eh dra chloric acidcan be varied between about 2 c. c. dabo other t nasoli i n wh ch. may be employed are (1) 1000 c. not calcium z20 chloride solution 40 B 2 to; 100 grams of zinc chloride, 2 to 100 grams of cuprouschloride; and 2 to 20 c. c. of hydrochloric acid; (2); 10000. c. of calcium chloridesolution 40 B., to 100 grams ot-ferric chloride and 0 to c. c. of hydrochloric V acid; (3) 1000 c. c. of calcium chloride solution B. 2 to 100 grams of cuprous chloride, 2 to 100 grams of ferric chloride and 2 to 20 c. c. of hydrochloric acid; and (4) 1000 c. c. of calcium chloridesolutionwj B., c. c. of ,lactic acid, 58 grams of ferrous chloride. In etching solutions such asthose mentioned the calciumchloride acts as a carrier. to. prevent the solutionlof the light exposed gum arabic coating. Other waterg solublesalts-ofalkaline earths may, also vbe used, forthis purpose If some masking coating. other than theonehaving a gum arabic base is used. e. -g., lacquer or enamelasabove mentioned, which is not dissolved by aqueous solutions thenthefl calcium chlorideorfthe. equivalent is not required. to be present.

As mentioned above it is I preferablyto; eiilploy as.the.activeetching agent, or toincorporate with another etching agent such as hydrochloric acid,

a salt of a metalwhich during the etching is olepositedto, appreciable; extentas a stain on the i etched areas of. the aluminum surface some to. protect the etched surface from reoxidation and. so as to leave a deposit which promotes the ad herenceof an electrolytically deposited coating so of copper or nickel. In the formulaeabOve mentioned salts of-iron, copperand zinc have been mentioned. owerer,- ta LQther m talsmay also be used such as tin1(e. -,g., stanrrous-chloride), a m mierq c dmi m chloride), cobalt: (es-t a; cobalt chloride), chromium, (e. g.,. chromium chloride) ornickel. (e. g., nickelchloride), More generally salts, may be...employed. wherein theg cation is a metal that is below aluminum in the. electromotive force series for, metalsand wherein, th v anion is the anion of-a strong. mineral acid such as hydrochloricacid, The cmet' llthus def, posited has a greateriaflinity forelectrolyticde position of copper or nickelthan doesaluminum. hes ltsoi es tals tral se asthasol tchi e t. th ugh pre er b sweh dr chloric. acid or otherstrong. acidisalso present 1 to speed up the etching action... Copper nitrat in the, presence of hydrochloricacid is an ex;

cellent etching agent andleayes. a staindepositflo f pp t tis ervrec p ve to. ctro l n -z.

While: it, is preferable to employ an. etch ngs bath,- that leaves.. a stain deposit ongthe area o1 umi um r a e at .haabcen etch d. hi i neteswfihl; hus-the xposedamas can. i qdeziue indicated.

red. be tc e only; with dm lo ia c dtin :s ilchf case flifie elctfoplatifig should be. per-Q formed? promptly a d the}. etching. before the etched. areas become excessively.coatedflvith a; filmjof aluminun'ifoxidemMoreovenin any. case "themesultihg electroplating. does not. provide as good or as firm a depositas'when the metal salt iscontainedin the etching bath- For the electroplating bath any ,cupric salt dis=. solved. in an acidic. medium. which .does not" at tackelurninum .cangbe employejd. As' in other. copper plating operations, itis ordinarily prefer-f: able to employ copper sulphate in a sulphuric acid aqueous medium. For 1000c. cfof waterit is 1151151 ally-desirable to employ from about to about. 300.,grams of cop'perf sulphate -and from-about 1 0 tofabout o c. c. of sulphuric acid. The propor tion ofyacid influences to some degree the character of the copper. coatingv that. is deposited, thje coating tending tobesomewhat softer if the pro portionof acid is cut down and tending to be a, somewhat more porousif theproportionof acid is-increased. A coating of preferred characteris-. tics is afiorded when the proportions are as above The presence of a small amount of an addition agent in the electroplating bathis preferable in afiording a smoother and brighter coating but is notessential. In addition to gelatine,. 0ther addition agents such as glue,.dextrine,.,

etc... can be employed.

During the electroplating a current density of 1 ampere'per square decimeter affords optimum 1 results when the electroplating is performed; without agitation at a temperature of about 72 F. However, the current density can be varied considerably, e. g., between about 0.25 andabout v.10

amperes per square decimeter.

In the practice of this invention the metal that. is deposited on the aluminum plate by electro- .f t-plating'j is copper. However, nickel may .be em -I ployed as well as mixtures-.ofcop'per. and nickel.- Copperis. preferred to nickel in-asmuchas copper'has a somewhat greater aflinity. for printing ant:than.does.nickel. If. nickel'is' employed any .1 conventional electroplating. bath for electrolytic deposition of .nicke1 mayjbe'employedli For exam plef. the electroplating bath .may' consist off1 2'0. gramsof nickeLsuIphate ZZ grams of ammonium-.1 chloride and 30- gramsiof boric acid dissolved 1000 .c. c. of water In th'e electrolytic deposition of nickel thesame current densities can be em;

ployed that are employed in accomplishing elec-. troplating. with copper.

It is apparent from the foregoing description .of this invention that a method isafforded whereby printing surfaces of. metal selected from the 7 group consistingotcopper and nickel are produced on. a printing member-presenting an aluiminum,.surface by selective deposition of the beielnfound to be extremely accurate readil carried out; economical, and .;capable of producing printing plates that are notablefor their very great durability in service. While thisinvention.

has been describedin connectionlwith'speciiic examples of the practice thereof thishas been done merely for illustrative purposesandthe scope of. 3- this invention is tobe governed by the languagev of the following claims.

I claim: n. the. production .ofira imetallicz, printing member presenting an aluminum surface partialfrom the group consisting of copper and nickel,

the steps comprising covering said surface with a masking coating containing openings having said predetermined outline within which areas of said aluminum surface having said predetermined outline are exposed, etching said aluminum surface of said exposed areas of predetermined outline not covered by said masking coating with an aqueous etching solution which comprises an anion of a strong mineral acid to thereby remove aluminum oxide from said areas and to render said areas receptive to electroplating with said metal selected from the group consisting of copper and nickel, removing said masking coating leaving both the etched areas and unetched portions of said aluminum surface exposed, and while said etched areas and said unetched portions of said aluminum surface are exposed subjecting said aluminum surface to electroplating for deposition of said metal selected from the group consisting of copper and nickel from an acidic aqueous solution of a salt selected from the group consisting of cupric salts and nickel salts, whereby said metal is selectively deposited as an integral firml adherent coating only on said etched areas of predetermined outline.

2. A method of producing a metallic printing member presenting an aluminum surface normally unreceptive to electroplating with a metal selected from the group consisting of copper and nickel, etching selected areas of predetermined outline of said aluminum surface by means of an aqueous etching solution which comprises an anion of a halogen acid to thereby remove aluminum oxide from said areas to render said areas receptive to electroplating with said metal selected from the group consisting of copper and nickel, and, while the etched and unetched areas of said aluminum surface are unprotected, electrolytically depositing said metal selectively only on said etched areas of predetermined outlin as an integral firmly adherent coating by electroplating from an acidic aqueous solution of a salt selected from the group consisting of cupric salts and nickel salts.

3. In the production of a metallic printing member presenting an aluminum surface partially covered in areas of predetermined outline with an integrally deposited coating of metal selected from the group consisting of copper and nickel, the steps comprising covering said surface with a masking coating containing openings having said predetermined outline within which areas of said aluminum surface having said predetermined outline are exposed, etching said aluminum surface of said exposed areas of predetermined outline with an etching solution comprising a salt the cation of which is a metal below aluminum in the electromotive force series and the anion of which is an anion of a strong mineral acid to thereby remove aluminum oxide from said areas and to deposit said metal of said salt on said areas as a stain that protects said areas against oxidation and renders said areas more receptive than aluminum for electrolytic deposition on said areas of said metal selected from the group consisting of copper and nickel, removing said masking coating leaving both said etched areas and the unetched portions of said aluminum surface exposed, and while said etched areas and said unetched portions of said aluminum surface are exposed electrolytically depositing said metal selected from the group consisting of copper and nickel as an integral firmly adherent coating only on said etched areas of predetermined outline by electroplating from an acidic electroplating bath containing a salt selected from the group consisting of cupric salts and nickel salts in contact with said aluminum surface.

4. A method of producing a metallic printing member presenting an aluminum surface which comprises coating said aluminum surface with a light sensitive masking coating, producing an image thereon comprising light affected areas and areas unaffected by light, said last-named areas defining said image, removing the areas not affected by light from said coating, leaving openings in said coating defining said image wherein areas of said aluminum surface are exposed, etching said aluminum surface in said exposed areas while the portions of said aluminum surface surrounding said areas are protected by said coating utilizing an acidic etching solution containing a salt the cation of which is a metal below aluminum in the electromotive force series and the anion of which is an anion of a halogen acid and a salt of an alkaline earth for preventing dissolution of said masking coating, washing away the etching solution while said coating covering said unetched portions of said aluminum surface remains intact, removing said coating leaving both said etched areas and said unetched portions of said aluminum surface exposed, and by electroplating from an acidic electroplating bath in contact with the said etched areas and unetched portions of said aluminum surface containing a cupric salt depositing an integral firmly adherent coating of copper only on said etched areas, thereby providing a copper presenting printing surface corresponding to said image surrounded by aluminum surface uncoated with copper.

5. In the production of a metallic printing member presenting an aluminum surface partially covered in areas of predetermined outline with an integral deposit of metal selected from the group consisting of copper and nickel, the steps comprising covering said surface except for said areas with a masking coating leaving said areas exposed, etching the aluminum in said exposed areas with an aqueous etching solution which comprises an anion of a strong mineral acid to thereby remove aluminum oxide from said areas and to render said areas receptive to electroplating with said metal selected from the group consisting of copper and nickel, removing said masking coating leaving both the etched and unetched portions of said aluminum surface exposed, and then while both the etched and un etched portions of said aluminum surface are exposed depositing said metal selected from the group consisting of copper and nickel on said etched areas by electroplating from an acidic aqueous solution of a salt selected from the group consisting of cupric salts and nickel salts as an integral coating having the outline of said etched areas.

6. In the production of a metallic printing member presenting an aluminum surface partially covered in areas of predetermined outline with an integral deposit of copper, the steps comprising covering said surface except for said areas with a masking coating leaving said areas exposed, etching the aluminum in said exposed areas with an aqueous solution of a chloride to remove aluminum oxide from said areas, removing said masking coating leaving both said etched and unetched portions of said aluminum surface exp sed, and then: we bothrtheetnhed encumetch d portions:ofzsaidsaluminumsurface are::ex- II-DOSEd' subjecting said. aluminum surface to. e1 ctroplating from an,acidic;electroplatingxbath con- :taining a dissolved-,euprie salt-whereby: 0011 129115;

;- el ctrolytically: :deposited .--as= airfi-rmly adherent coating only on said-etehed=;;areas-1of-- predeter- -.:m-ined outline.

i '7; Inthe productionyzof atmetallic-iprinting member according to ,claimfi, thesteps according to-elaim 6 wherein saidetchingisolution comprises a-dissolyed'saltof a metal below aluminuminthe ,electromotive forceseries.

JOHN E. MORSE.

' REFERENCES"CIT-ED The following vreiereneesuame. ,ofreeord, in the Jile of this .patent:

- UNITED: STATES PATENTS Certificate of Correction Patent No. 2,506,164 May 2, 1950 JOHN E. MORSE It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 54:, for the Word lift read life; column 8, line 44, for ank read ink; column 9, line 38, after areas, first occurrence, insert and; column 12, line 9, list of references cited, for Aug. 25, 1915 read Aug. 24, 1.915;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 25th day of July, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Oommissioner of Patents.

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