US2584317A

US2584317A - Method of producing bimetallic printing forms

Info

Publication number: US2584317A
Application number: US794257A
Authority: US
Inventors: Aller Claes Bphirge
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-09-09
Filing date: 1947-12-29
Publication date: 1952-02-05
Anticipated expiration: 1969-02-05
Also published as: NO76687A; FR958963A; GB663842A; IT440807A

Description

Feb. 5, 1952 2,584,317

METHOD OF PRODUCING BIMETALLIC PRINTING FORMS c. B., ALLER 7 w i MWM INVENTOR CLAES BQRGE ALLER ATTORNEY Patented Feb. 5, 1952 time on.

2,584,317 z. .i 6D'Uoi'NG-BiME'rALLIc orrice e Binge l a. e ea rk Attract-m December 29, 1947; SeiialNo. 794L257 Section- 1; Public Law 690,- Aii'gu'st 8; l946 Patent expires Septemberd), 1966 ;The presentinvention;relates to a method of producingbimetallic printing forms,.i. e printing forms in which theparts of the printing surface which areito transfer ink during printingha're madegof another metal than the, parts that are. 5 not-required to transfer;ink;.i Bimetallic printing forms; are. mostly used for :planographic printing; particularly offset, the twometals being soichosen that:;in presence or: water; one a; will retain ;the water ;andi;repel;ink whereas :the ether zone in 10 spite-of the. presenceiof water. will retain-printers ink and:thus.;transfer ink'in the printing process;

In asuch; planographic printing processes the height of the ink-retaining partsimay difierifrom; that-mi zthe' ink-repelling: parts .of:;.the :printing plate, butin most cases :there is either -no"difier= ence;in: height or the differenceisiso: small that. iUfiS. ofz'nor significancexior printing purposes;- The .;present invention; more" particularly: relates" t the production of printing plates of the latter kind; .15.; 1:.1'. 19.. J in L In the production of such; planographicllprinte; ing' platesit. is known to :deposit on the "surface of; the metal which is. totforml onerof the; surface components-in "the/printing process'ia continuous layer pf the-g'metalz. which is; .to; form; therother surface: component;;after;:which' 'a copyinglayer; isgappliedto the surface of the-metallic layer last mentioned; afterwhich copyingis carriedsout and. thegcopying layer is developed, :andxthe parts of w thergmetallic intermediate. :layer which. are. not coyered: by thelzcopying layer .afterjdevelopment are etched right through to the supporting layer." Inxprder tobetter protect the parts ofithe intermediatemeta-llic layer coveredbyxthe parts'of thev copyremaining after development the lattermay be hardened'by being burnt in. or by. melting inksuitable protecting}. agents. After etching said protecting, agents and the parts of the.copy ingJayernot, removed .in development may be 4(} removed inknown manner; l V

This known method suffers from several draw backs; Thus it has been found thattherecan"-'f not be obtained in this manneratruerecording'f and a -s'uflicient protection of 'the' finer printing" 5 elements during etching. This'is due*'to* the* etchingagent being to some extent capableof penetrating "to the back of' 'the' protecting lay'e'r fro'm the borders ofthe areas'prote'cted and thus s alter the: size or shape ofiithe sprinting: elements. o1t:,caus.e;them;to:adhereinsufiiciently to. the sup- D 1122 11dipth syd achv themselves-.11.; a a .11; Itgisalso known to deposit the ink-retaining. metahcomponent through the openings 01 2, copy produced directly on the surface of the other 2 Claims. (Cl. 204-17) metal component. -In this process it has, how'- ever,- been difficult to obtain adeposit of equal thickness vin smaller and greater printing areas.- Consequently in many-cases a correct recording ofthe values oflhalftones cannot be obtained and=the printing=elements will in some places wean/too fast ordetachr 1;: r 1

q Moreover it z-has been proposed in 'a-method t which allegedly can: be usedin-connection with both :reliet intagl-io land planographic printing to :deep-etch-the supporting metal after areas-0f another metal, :fillingdnl metah have been de-. posited thereon through :the openings of a copy asdescribed above, using for the said deepetchingan etchingagent which does-not attack thefilling-in metal. In order tc-broaden the base part of the saidfilling-in metal to make it adhere better to thesupporta layer-of resinis applied betweenwthe supporting and the copyinglayer and after-(development of the copy the resin is re=- moved within? the non-ecovered-areas the removal being-extended: slightly behind-"the covered areas too-in order to'allow-forthe said broadening of the bases .of. the: filling-in metal; This method, however; -is-not suited =forplanographic plates; since then-said base will alter the value of the half f nes g l4, v .7 The; object ofleth-iswinventiont is a method-of producing planographic printing forms in which all these drawbacks are removed; Otherobjects and purposeseof the inventionwihappear from thefollowingldescription andelaims. ,lBroadly therinvention consists a in a method: of producing planographic printing forms in which approtecting imagea-is used for protecting theparts of the printing surface oftheform which are IlOtetObe attacked by theetching agent duning'etchinge'and the-ieature characterizing theinventiQnEis-thatvthe protecting image is applied to I, the.-;surface: -of aj ga-lvanicallydeposited continuous-intermediate layer of a metal acting as one of themetalliccomponents in the plano--- graphic printing aiprocess which intermediate metal layer -iis again placed upon a base-layer' of- -a material acting as the other metallic component inethe bimetallic-planographic; printing process :andther none-protected parts of the metallic intermediate layer are-etched away right a through to the surface of the base, metalsby an:

etching=agent which does not attacl; the protecting metal. 1 l-,1. ,7; (More particularly.according to the invention thee-methodis appliedto the-production of print ingaforms in which one oi-thecomponentsentering in the bimetallic printing process is chromium or a chromium-containing alloy or stainless steel.

Between the intermediate layer and the pro tecting metal and between the intermediate layer and the base metal which layers are both of metals forming the components of a bimetallic planographic printing process there may be interposed other metals for instance silver for other purposes such as for improving adhesion or facilitating good deposition. The claims are to be understood so as to comprise methods-in which this is the case if for any purpose it should be desired.

In contradistinction to the known method in which a continuous metal layer deposited on a support of the metal which is to form one of the components in a bimetallic printing process is protected during etching by a copy, a metal is used according to the present invention for the protection of the areas which are not to beattacked during etching, which has the effect that these parts will not at all be attacked. Consequently recording will be exact and the printing elements willnot alter their size or shape or adhere insufiiciently to the support.

The method which forms the subject matter of the presentinvention moreover differs from the known method in which-the one metallic component is deposited upon the other one through the openings of a copy placed thereon in that none of the two metallic components in the bimetallic planographic printing process are according to the present invention deposited through the openings of the copy. Thereby it is avoided that the deposited metallic component of v the said process will appear in undesired unevenness of thickness.

From the known method which is also mentioned above in which the base metal is deepetched after a metal hasbeen deposited on it through the openings of a copy produced on the surface thereof the present method diifers not only in that no resin layeris interposedbetween the base metal and the copy as mentioned above but also in that the metallic intermediate layer original copy. The exactness is due to the thinness of the intermediate layer and the-capability of the protecting layer to completely protect the parts covered thereby. Such exactness will not be obtained in the known method even if etching is carried to such a depth that it reaches a further base plate supporting the firstone and being of steel. This appears from the fact that the walls of the pits produced by etching are not vertical and that the purpose of the resinous layer used in the known method is to avoid the walls being vertical in order to secure the partsremaining after etching a broader base.

The term etchable and non-etchable-used above and in the following is notto be taken in the absolute sense of the word but means that the metalin question is one that is not attacked in the etching process in question.

In connection with using chromium, chromium-containing alloysor stainless steel as the water-retaining component which'is the most important kind of planographic process with which the present invention can be used and particular great advantage can be obtained there may be used as is well known copper, brass or bronze as the ink-retaining component. These components will act in the printing process in the said capacities irrespectively whether one or the other is placed in the uppermost position and the present invention can be employed in connection with both possibilities. If chromium or a chromium-containing alloy is placed on a surface of an ink-retaining metal such as copper,

brass or bronze it is on the surface of the chromium etc. that the protecting metal is to be placed and the chromium etc. must then be etched through at the same time leaving the protecting metal as a non-etchable metal. An example of an etching agent by means of which this can be carried into efiect is hydrochloric acid provided that the protecting metal is one not attacked by this acid for instance lead. If on the other hand an ink-retaining metal such as copper, brass or bronze is placed on the surface of the ink repelling metal, chromium, chromium-containing alloy or stainless steel the inkretaining metal must now be etchable and an etching agent capable of etching the exposed parts thereof away must be used. Examples of such etching agents are given in the following. Also in this case, however, the protecting metal must be non-etchable to the etching agent used.

According to an embodiment of the invention iron, lead or tin or alloys thereof are used for the protecting metal. These metals. are easy to apply in the electrolytical way and they ofier an excelent protection for the parts of the metallic interlayer which are not to be removed. Also in this case there may be used an acid etching and if the metallic interlayer is an ink-retaining component such as copper, brass or bronze, chromic acid is very suitable since it removes such metals very readily and does not attack the protecting metals even iron.

According to another embodiment of the invention not only iron, lead or tin but also many other metals may be used for the protecting metal such as zinc or cadmium if for the etching agent there is used a sulphidizing agent such as a solution of an alkali metal sulphide or alkali metal polysulphide, which converts the intermediate metal layer into an easily removable sulphide if this consists of copper, brass or bronze. If it consists of chromium etc. evidently this etching cannot be used.

In case of extremely delicate printing elements this embodiment may be even preferable to the acid-etching method mentioned above since it is practically undamaging to such elements.

If a sulphidizing etching agent is used it is preferable to support the etching process by using an electric current, which is passed through the etching agent using the printing form as one of the electrodes in the circuit. To remove the sulphide formed by the etching process it may.

be necessary to employ a powerful rinsing or a slight rubbing. action.

Generally the protecting metal is to be removed from the surface of the intermediate layer of metal before printing. This can be done'by means of an acid etching agent which does not' attack either of the two metals entering into the planographic printing process. In most cases diluted sulphuricacid will be found suitable.

The deposition of the protecting metal is preferably carried out by means of the electric current.

Two embodiments of the invention will be described in the following with reference to the drawing in which Figs. 1-4 show schematically the various layers of a printing form in section on four stages of its production.

Example 1 A plate S of stainless steel or of copper or nickel coated on one side with chromium or any other plate of which at least one surface is a surface of chromium or chromium-containing alloys, for instance, stainless steel is covered on the surface consisting of chromium, chromiumcontaining alloy or stainless steel with a continuous layer of copper C. To the layer of copper there is applied a light sensitive film, for example, a chromate-gelatine layer which is then exposed to the influence of light through a transparent positive and developed in the ordinary manner. The parts of the copying layer remaining after development on the surface of the continuous layer of copper is designated by L in Fig. 1.

The printing form appears now as a chromatecolloid image on a base of copper. This image is negative when considered as an image of colloid and positive if it is considered as an image of uncovered copper surfaces.

In order to protect the copper surface elements during the removal of the areas now covered by colloid a protecting metal F is applied to the said areas. The protecting consists in iron which is deposited in the electrolytical way.

For this purpose an aqueous solution of an iron salt is applied to the surface of the plate placed on a table by means of a brush in the bottom of which at the roots of the bristles an iron electrode connected through the handle to the positive pole of a source of electricity is placed. At the same time the printing form is connected to the negative pole. By working on the plate with such a brush a layer of iron is in all parts of sufiicient thickness can be deposited in all openings of the layer of colloid even the tiniest.

Then the colloid image is removed by hot water and the plate is now composed as shown in Fig. 2.

Now the copper is removed by etching from the areas which are not covered with iron. The etching agent consists of chromic acid made by dissolving chromic, acid anhydride in water. The plate is now composed as shown in Fig. 3.

After this the layer of iron is removed by means of an etching agent consisting of a solution of diluted sulphuric acid or nitric acid after which the plate composed as shown in Fig. 4 is ready of use.

In the drawing the layer of copper and the layer of protecting metal is shown in exaggerated thickness. In fact the layer of copper must be as thin as possible. Theoretically it needs only be of molecular thickness, but to increase its resistance to wear its thickness may practically be increased to, for example, a few hundredths of a millimeter. The protecting metal may be used in similar thickness.

Example 2 .The plate S is of copper or steel coated on at least one side with a layer of copper. This plate is now covered on the copper surface with a con- 6 tinuous layer of chromium C, for instance, by electrodeposition. As to the thickness of the layer or chromium the same considerations apply as in the case of copper in Example 1. copying layer is applied in the same manner as in Example 1 and exposed through a negative.

The printing form snows now a colloid image on a base of chromium. The image is positive when considered as a colloid image and negative if considered as an image of uncovered chromium surface elements.

In order to protect the chromium surface areas to be maintained during etching of the areas to be removed a protecting metal F consisting of lead is deposited on the surface areas not covered by the colloid image. The lead is deposited by electrolysis in the manner described in Example l. The colloid image is removed and the plate will be of the construction shown in Fig. 2.

Then the chromium is removed from the areas not covered by lead 101' which purpose the etching agent consists of hydrochloric acid which will not attack the lead and copper. The plate is now constructed as shown in Fig. 3.

Finally the layer of lead is removed by means of nitric acid arter which the plate shown in Fig. 4 will be ready for use.

I claim:

1. lvletllod of producing a planographic printing form with bhnetallicsuriace comprising the steps of: depositing gaivanically on to a base of stainless steel a thin continuous layer of copper, applying to this galvamcally deposited layer an image forming coating covering such parts of the layer subsequently to be removed, galvanically depositing on uncovered parts of the copper layer a thin layer or iron, removing the image Iorming coating, removing uncovered copper down to the base layer by means of cnromic acid and removing the iron layer by dilute sulphuric acid.

2. Method of produclng a planographic printing form with bimetallic surface comprising applying to the copper layer of a bimetallic printing form consisting of a stainless steel base carrymg a thin continuous layer of copper. an image forming coating covering such parts of the copper layer which are subsequently to be removed, depositing galvanically on the uncovered parts of the copper layer a thin layer of iron, removing the image forming coating, removing uncovered copper down to the base layer by means of chromic acid, and then removing the iron resist.

CLAES BQRGE ALLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 444,951 Goodwin Jan. 20, 1891 758,599 Sachers Apr. 26, 1904 797,668 De ey Aug. 22, 1905 1,376,365 Wertheimer Apr. 26, 1921 1,783,664 McFarland Dec. 2, 1930 1,871,734 Trist June 23, 1931 1,886,817 Johnston Nov. 8, 1932 2,214,950 Aller Sept. 17, 1940 2,241,585 Day May 13, 1941 2,408,220 Lum Sept. 24, 1946 The

Claims

1. METHOD OF PRODUCING A PLANOGRAPHIC PRINTING FORM WITH BIMETALLIC SURFACE COMPRISING THE STEPS OF: DEPOSITING GALVANICALLY ON TO A BASE OF STAINLESS STEEL A THIN CONTINUOUS LAYER OF COPPER, APPLYING TO THIS GALVANICALLY DEPOSITED LAYER AN IMAGE FORMING COATING COVERING SUCH PARTS OF THE LAYER SUBSEQUENTLY TO BE REMOVED, GALVANICALLY DEPOSITING ON UNCOVERED PARTS OF THE COPPER LAYER A THIN LAYER OF IRON, REMOVING THE IMAGE FORMING COATING, REMOVING UNCOVERED COPPER DOWN TO THE BASE LAYER BY MEANS OF CHROMIC ACID AND REMOVING THE IRON LAYER BY DILUTE SULPHURIC ACID.