US2451331A - Electrolytic recording - Google Patents

Description

Oct. 12, 1948. H. G. GREIG ELECTROLYTIC RECGRDING Filed Deo. 3, 1945 l, IN

' Patented Oct. 12, 1948 ELECTROLYTIC RECORDING Harold Grey Greig, Princeton, J assignor to Radio Corporation of America, a corporation of Delaware Application December 3, 1945, Serial'No. 632,547-

12 Claims.

The present invention relates to the electrolytic production of colored records and particularly to the use in such a method of compositions which are designed to give on a light background dark blue gray color images which simulate black in color. l

Solomon in his U. S. P. 2,306,471 discloses various methods of producing colored records by the electrolytic method. lIlhe bes-t of the methods disclosed by Solomon from a practical standpoint is that which may be termed the electrolytic diazotization 'and -coupling method. In .this procedure, a traveling web or band of lbrous material which has lbeen impregnated with a diazotizable amine, an ionizable nitrite, an electrolyte and a coupling component is subjected to electrolysis with the formation of a diazonium compound yat the anode which subsequently couples with the coupling component to produce what is probably an azo dyestui. While this method :has many advan- .tages over the previously known method involving the utilization of an electromagnetically controlled printer bar, particularly from the standpoint of the speed at which the records are made and the wear on the printer bar, it nevertheless presents the diiculty of selecting diazotizable amines and coupling `components which when chemically united give color images approaching black on a light Ibackground. Many of the diazotizable amines vand azo dye Icoupling components which have been proposed in the past give dark ycolor images but these are eithertoo lblue, purple or red in color. On the other hand, others which have been selected yield dark -colors but with a -colored background so that there is insuicient contrast from a practical standpoint in transmission of the record. While many attempts have been made tov select componentsy which when diazotizedand coupled produce black records on a light background, -to the best of my knowledge such attempts have to the present time met with consistent failure.

I have now found that it is possible by the electrolytic diazotization and coupling method to produce dark images on a stabilized light background if there be employed as the diazotizable paper staining reaction products.

group and which serves in part as the coupling component also has a decided stabilizing. veilect upon the background of the records obtained.

It is accordingly an object of thepresentzginj Vention to provide ya composition; for theprodum tion of colored records .by electrolytic diazotization and coupling which insures the formation of colored images simulating vblack in color on a light background.

It is a further object of the .present invention to provide a method for producing electrolytic records in which the color images formed simulate black in color and are produ-cedlonFalight background. f l

It is a further object of the present invention to provide for the production 'of coloredrecords by electrolytic -diazotization and coupling lwhile using a specific diazotizableamineland 1Vspecific coupling -components and to vary the shade-of lthe recorded color image `from blue to yellow while adjusting the. proportions of the diazot'izable amine and of the coupling components.

It isla. Afurther object of the present invention to employ a nitrogen containing organic compound for increasing the darkness of the image of the records.

Other and further important objects of the invention will be apparent as the descriptionproceeds. 'Y

The particular diazotizable amine? contem# plated by the presentinvention isb'enzidine'- disulfonic acid. YNo other diazotizaiblle amine has been found which will Ifunction in the desired relationship to yield 4the lblack appearing records on -a light background required herein. As a matter of fact, ii benzidine monosulfonic acid appears in the composition even as -an impurity, it aiect's the stability of the 1solution by forming Furthermore, such compound if present shifts the shade of t-he recorded c-olor towards purple. Even the isomeric amine a particular aryl diamine disulfonic `acid tant observation which I have made is thatfv the compoundwhich contains a. reactive methylene blue to brightl yellow. Another and very imporfV benzidine`2.2'disulfonic acid when present as an yimpurity causes a shift in the shade of therecord towards purple. The employmentof benzidin'e- 3.3disulfonic acid as the diazgoti'zable'v'aminefis accordinglycritical-to the invention.` A l The naphthol sulfonic acid couplingcomponent which is employed is a benZoylIfI-acid haviling the following' constitution:

in which X is hydrogen, an acylamino groupl such as acetylarnino,y propionylamino, benzoylamino, lfuroylamino 'and the like,-alkyl I.such as methyl, ethyl, propyl, butyLoctyl and the like,

alkoxy ysuch as methoxy, ethoxy, propoxy, butoxy and the like, halogen such as chlorinebromine and the like, and aryloxysuch as phenoxy and the like.

Where X is a substituent group, it may be at-y V tache'd at any position ortho, meta-,vA orfrparato the amide linkage in the 8-position of the naphthol ring. 'Examples of suitablecompoundsare benzoyl H acid,'benzoylpamino benzoyi H acid,

acetyl-pamino benzoyl H acid, benzoyl maminobenzoyl H acid, toluoyl H acid; rrr-methoXy-benf Y zoyl H acid, p-phenoXy-benzoyl H acid, Vp-ethyl-V benzoyl H acid, m-butyl-benzoyl H acid, `11a-'chloro- Y benzoyl H acid, and the like.

' The other 'couplingV cornpoi'u'rd` containing 'the reactive methylene group is a diac'etoacetyl. alkylenepolyamine in which the alkylene. chain may tie-interrupted by irnino.` Such compounds: have the following n stru ctural` formula Qin-which Y isan alkyicnc rcdicarcr such-radica t interrupted by an imino group. Examples ,ofV

such. 4compounds are diacetoacetyll ethylene diaminec-'dacetoacetyla propylene diamine, diacetoacetyl butylene diamine, diacetoacetyldiethylene triamine, diaoetoacetyl. triethylene tetraminefand the like".

Compounds other than those' vin the aboveclass and i which containa .reactive methylene .group have been tested but for .the most part the results V*obtained therefrom arernegative in character.

Theoretically, .mono-aceto-acetylfp-phenylene di-Y .amine should vgive a morepronounced change in shade towards black than .the diacetoacetyl alkytc 1Y gram m01 cf the nner) tc produce a black record, such record shows ajgreater tendency tor darken in the VbackgroundY upon file storage.

' The hue or color of the records is dependent to Y a large extentV upon the ,proportions of thecomponents "formingfthe dyestuf of the'iinags there-y of and thisV is particularly true V'as regards the lcoupling components. The benzidine-3.3disul Afcnic acid is used in the ratio cf about .02 1:0.'036 5 I vgram mol perliter with the proportions ,ofV the coupling components as subsequently stated has relatively llittle 'eecton the color of Vthe image records. If th'eaymount be decreased below .02. gram mol perA liter, the recordedcolor has a` .strengtnwhich is belowthat required for prac- Nevertheless, legiblel tical recording solutions. recordings can still bemade at concentrations below said limit of .02flgram rnol per liter. If the quantity Iof .the benzidine 35'-disulfonic' acid be increased above ithe upper limit of".036 gram mol, the'stability of the background suffers,l ali-` A though here again, legible Vvrecord-ings :can be Iliade.

My investigations have 'e'stabl-i-slfie'ditliai-,-l with an amount of the diabotizable amineY in thefratio stated, Ythe desired lblack 'images on a lightfback.- ground'can beobtainedwhile usiiifgth,benz'oyl H .022 Vglam mcljpcr liter aud 'che' di'acetcacctyriaikylene polyamine in ,an amount of .029210,05 gram mol'per'liter. I l

If therecording'solution'be Inadefup ith u,the

Y ,beminnen-3.3-disuifcuic. acid Wil-,1uicuiifgga(bcn,-v zoyl Hacidaslthe 4ciouplirngn component, thejirodlV uct L. which willV be obtained, Aassuming the;couplerv to be bcnzcyi Hfacid, will navctnclfcilcwin c eb,- able formula;V

This `dyestu Vgives ja brightV 'blue recordgon `a yellow tinted background;l Ifv, onth'e'otherlhand, the recording isoluti'o'niis Amaclu'jga with thefbY nfzidine3,3"disulfonic acid and with, Vfor example. diacetoacetyl ethylene diamine `as ,theV ,only coupling component; the '.dyestu whichfisfobtained k has the following I'Ji'fobableV formul'a Jene polyamines. Unfortunately, ,howeveij, the

solubility of this .compound doesnot .a sufcient quantitvoftheY-s'ame to remain .in soluf non to produce the dcsircdblack shade. while;

it may be employedV in .aclmxture `with thev diace- Ytoacetyl alkylene polyamine '(say, inan1ounts ranging from ,10 to .'25 grain/mol oftheforrner the ben'zoyl H'aid and the4 diacetoacetylgethylene Y diamine, particularlyin the. proportions statemla ,product will be obtained which. Willcontain a dye-1 stuff` having .either the following formula;v

Nk 0H SOaNa It appears that when the two coupling components are employed, a mixture of dyestuffs ensues n in which, however, there is probably present the product of 'Formula III or IV. Where the proportions are selected as indicated, such product is the major ingredient in Which case the desired blue-gray records are formed. For instance, the recorded color obtained when using a mixture of coupling components in said ratio is a gray on white on washed copy and such color under ultraviolet light appears as a bright red on white. The recorded color on unwashed copy, however, is more nearly black on a light yellow background and under ultraviolet light appears to' be aA strong black on a yellow background. This difference in color between the washed and the unwashed records Aindicates that two or more colors are formed during the electrolytic step. It is to be pointed out, however, that there is no indication of the presence o-f a product of Formula I or of II as these appear blue and bright yellow respectively When viewed under ultravi-olet light. Despite the fact thatv a mixture of dyes appears to v'be formed, it is surprising that the mixture does not show up a-s a two-tone effect in' recording a picture where a gradation in the density of the color is necessary.

It is apparent from what has been'said abo-ye about the proportions of the coupling components that by having present an excess of the benzoyl H acid or its derivative over the ratios given, the recorded color will be shifted towards the blue end of the spectrum. Conversely, if there bean excess of the diacetoacetyl ethylene diamine present, the recorded color will be shifted towards the yellow region Of the spectrum. By a modification of the expressed ratios, it is as a matter of fact possible to obtain recorded colors ranging from bright blue through dark blue, blue-gray (almost black), brown, orange brown and bright yellow. While themain purpose of the present invention is to utilize the aforementioned diazotizable amine and mixture of the coupling components in a ratio assuring the formation of a record simulating black in color, nevertheless it' is to be understood that the invention in its broadest aspects also contemplates the utilization of mixtures of the aforesaid coupling components in ratios which will lead toa recorded colorother than black.

An indication of the results which ensue when departing from the aforesaid ratio of coupling components may be gathered from the following information. v If, for instance, there be employed .0231 gram mol per liter of the benzidinef disulfonic acid with .008 gram mol `per liter of the benzoyl I-I acid compound and .073 gram mol per literv of thediaeetoacetyl alkylene polyamine,

the record obtained is bright yellow. `Onthe other hand, if there be employed .0303 gram mol per liter of the benzoyl H acid compound, .025. gram mol per liter of diacetoacetyl alkylene polyt' amine with .0214 gram mol per liter of the'benzifv dine-3.3disulfonic acid, the recordobtainedisy a pleasing blue in color.r These proportionsthr'efore give a general indication of the variations'in color which may be obtained Within the range of hues previously mentioned. i

The importance of the observation that Athe invention contemplates other proportions of .coupling components than thosel stated is more forcibly brought home by the fact that the di-r d acetoacetyl alkylene polyamine kexerts al dual function in the composition. Thus not only does this component react with the diazotized benzidine-3.3disulfonic acid in forming thecolored record but it also has the surprising capability of exerting a very strong stabilizing effect'which retards the background darkening attributable to the benzoyl H acid. This effectis produced even' when the diacetoacetyl alkylene polyamine is' employed in quantities outside of the ranges serv' ing to produce the blue-gray, simulating black colors. v i

Another feature of the invention, which is of prime significance, is the finding that ,the darkfl r ness of the color may be considerably improved if there be present in the recording solution a quantityfof an aliphatic compound containing-a thio amide group in which the nitrogen atom of the amide is disubstituted by hydrogen.- Suitable examples of Compounds within this category are thiourea, thiosinamine, thiocarbamic acid and the like. These compounds due to the presence ot the NH2 group therein have the ability to formsalts with the sulfonic acid groups in the diazetizable amine and the coupling components. vOn the other hand, it is an accepted fact that the grouping =C=S present in the aforestatedcom# pounds is a very strong chromophoric group. It has not beenascertained whether the darkening of the color resulting from the utilization of these compounds is attributable either to salt rformation orto the presence of the chromophoric group or both. However, despite the theory involved, the fact remains that the use of these compounds definitely effects darkening of color and hence they are desirable adjuncts in the recordingfcomposition. The quantity of the 4compounds which are to'be used should range from 'about .02 to .0526 gram mol per liter of solution. The other essential components of the composition are an electrolyte to facilitate the. passage of the electrolyzing current, and a water-soluble: metal nitriteto furnish the ions necessary for.

v; tralinorganicsalt such as sodium chloride, so-;

f'stable. Y

*'color is beingrecorded.

'Ifhe currentdensity under theserconditions'may "also vary` considerably although' itihas a mini- Yalllffrfant Color'j'formalf'Ellis millir"rnuirris termed'gthe threshold value and varies with the composition of* thefsolution used, High alkalinity; or re'ac'iily.,:oxidized` vorganic I'inter- ,mediates yand the like increase` this threshold ""v'alue or'minimum current necessari/'jor faint color formation. The primary're'quisiteis that the current produce a highl enough concentration of hydrogen ions at the surface of the positive electrode to overcome the initial alkalinity of the wet carrier andallow for nitrousacid formation and -diazotization of the benzidine-3.3disulfonic acid. Thev upper limitjof` the current density is determined by either that density at which the conditions.

Theinvention is. further illustrated' bythe following examples but it is to beunderstood that l the inventionis not 'restricted thereto.

, A recording solution is prepared by the method *previously indicated from .03 gram mol of benzi- "dine-disulfonic acid, .0104 gram mol of ben-4 -Zoyl Hjacid, .88, gramlmol'of sodium hydroxide (2.5 Ns'oluti'on) .39 gram mol of sodium chloride, .035 gram molofgdiacetoacetyl ethylene diamine, .0526 gram ymol'of thi'oure'a,.l'39 gram mol of sodium nitrite 'and a literA of'water.. Paper is impregnated with this solutionland the so impregnated paper is passed through the apparatus describedA above. There is thus obtained a dark recordlon a light background which isstorage Example II The composition is the same as in Example I except that there is added to the composition .5 gram per liter of the wetting agent obtained b-y condensing benzene sulfonic acid with chlorinated kerosene.

Example III The procedure is the same as in Example I excepting that there is employed .0273 gram mol of benzidine-3-3'-disulfonic acid, .0094 gram mol of benzoyl H acid and .05 gram mol of diacetoacetyl ethylene diamine.

Example IV The procedure is the same as in Example I excepting that there is employed .025 gram mol of benzidine-3-3-disulfonic acid, .022 gram mol of benzoyl H acid and .0292 gram mol of `diacetoacetyl ethylene diamine.

In each of the above examples, the recorded color is a sufliciently dark one to give good contrast on a yellow tinted background.

Example V The procedure is the same as in Example I excepting that the benzoyl H acid is replaced by an equivalent amount of benZoyl-p-amino-benzoylI-Iacid.

The procedure is the sameas in Example excepting vthat the diacetoacetyl ethylene diamine is replaced by auf-equivale t amount of diacetoacetyl iefopylerdiemmQ-f i ffexgmpzevrr Y Thelprocedure is: the same asin Example I ex- Lceptin'g' that the vdiacetoacetyl ethylene diamine 'lig repla'ce'drby an equivalent amountv of diacetovacetyl .diethylene triamine. VMTI claim: f v

l. Aprocessvof 4producing colored image rec- '.oi'dsfsimulati-ng :blackon a light background on :aA traveling carrier whichrfcomprises treating the carrier with an alkaline solutio'ricontaining as its `essential' components `benzidinea'i.3'disulionic 'f acid Tin' an amount ranging from .02 to .036 gram Amol per liter of solution, an alkali metal nitrite :ma sufficient amount to effect tetrazotization of the `benzidine-B-disulfonic acid, a neutral elec'- trolyte in a sufficient quantity to lfacilitate the Apassage of the electrolyzing current, and as coupling components .0292 to'.05 gram mol per liter of solution of adiacetoacetyl alkylene polyamine Vand '.0094 to .020 gram. mol per' liter` of solution of a compound ofl thef following formula: i

in which X is selected from the class consisting of hydrogen, acylamino, alkoxy, alkyl, halogen and aryloxy, and subjecting the treated carrier to the action of an electrolytic recording current.

2. The process as defined in claim 1 in which the solution Vincludes analiphatic thioamide for .the purpose of increasing the darkness of therecorded color. 'Y

3. ATheproess as dened in claim 1 in which thesolution includes a wetting agent for facili- -tatingjcthe applicationv ofthe solution to `the carrier.

4. The process of producing colored images on a traveling carrier, said images having a bluegray color simulating black on a light background, which comprises treating the carrier with au alkaline solution cont-aiming as its essential components and per liter of solution .020 to .036 gram mol of benzidine-3.3disulfonic acid, from .0094 to .020 gram mol of a compound of the following formula:

HOaS- SOsH 0 and subjecting the so-treated carrier to the action of an electrolytic recording current.

5. The process as defined in claim 4 in which there is present in the solution from .02 to .0526 gram mol of an aliphatic compound containing a thioamide group.

6. The process de'ned in claim 4 in which there is present thefsltien from .02 to .0526 eiaelmelfeffthouseaf r, v l.

' 7 @recess-Hof Reducing'feleredfimegeS-en Blue-'gray simulating black onyaliglitfbaclgnound which comprises treating the carrier with an aqueous solution c'ortairii'rigas its essential com- '.penentsandmer 1li-termis solution ,Y :02'lf3ig1fam mol Y :cfg gbenzidine-.Sg-disultenic acid,l 5.0095 gram Emol ethylene diamine, .39 gnamgmolof sodium ch1o/ ride, .139 gram mol Yof sodium nitrite; 5andp.0526 e,gram@nel of :th-iourea andzsucient sodium vhy- Ydioxidetoigive arPI-I of eitoqttifandsubjecting the :treated carrier 5toA tl-1e I action Iof :an electrolytic .recording current.: A 1 f8.1 (Aiflbmus @sheet -rrleterial for .the electrolytic t rmationthereon yoftzo :dye-'records simulating gl-)lack ona light background, .said sheet material fbeingv treated with-:em `aqueous alkaline solution f `containingv as =.its essential components vbenzi- .gdineg-Sdisulfonic acid in` an Y amount ranging fimmvlozfto 036-gfra1n-molper liter 'of'zsolutiom a watersoluble :metallic nitrite -in :a vsufficient p,

tamount effectYtetrazotization of said :benzidine-rSfdisulfonicyacid, -a lneutral electrolyte in an amountisucient'to acili-tatefthe passage cf the electrolytic recording current and as thecoupling components .0292 Sto E05 gram mol per liter of solution of Ld'acetoaxietyl' alkylene rpolyamine and .0094 to .020g-ram`mol per literA of solution of a compound ofthe following formula:

'ein s' s'ieete'affromthefeiasseonsiungof Mydregemecyiammo; aikoxygf-aikyi, halogen and aryloxy i aereas Lsnee',t Smart@nal fasennedenf daim eene@ Y -ing :Ltl'iereoncolorei records.'simulatingfllak nl `.aQliglfltbackgrciintltnicontairiinerlasQitsegssentizil 1 Af'nbmus sheet material treated with aqueous solution capable of letrolyticalllylyilfd] ving V,thereon colored records simulating lacklcm lalliglit` background and co1tainingV as its vessential :Name j y Solomon Dec. 20,@942

,Date Y

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