US2440526A - Fibrous sheet material for the electrolytic formation of an azo dyestuff thereon - Google Patents

Description

Patented Apr. 27, 1948 FIBROUS SHEET MATERIAL FOR THE ELEC- TROLYTIC FORMATION OF AN AZO DYE- STUFF THEREON Myer Solomon, deceased,'late of Westmont, N. J

by Nellie W. Solomon, administratrix, Princeton, N. J., assignor to Radio Corporation of J America, a corporation of Delaware No Drawing.

8 Claims.

This invention relates to the art of electrolytic dye production and more particularly, to an article of manufacture involving a fibrous sheet material for the electrolytic formation of azo dyestuffs thereon. In a preferred adaptation, it includes the production of dyes of the aforementioned type in connection with the art of facsimile recording. The fundamentals of the present disclosure are set forth in the copending application Serial No. 178,743, now U. S. 1?. 2,306,471, of which earlier application the present application is a continuation-impart.

Various types of facsimile receivers are used at the present time, and in substantially all of them pictures, printed matter, or other characters are produced on a recording sheet of paper in response to variations in electrical current which are received from the transmitter station. In one type the reproduction of the character or indicia is through the use of carbon paper and the transfer of the carbon to the record paper is accomplished by means of an electromagnetically controlled printer bar. In such a device the recording paper and carbon paper are placed in the facsimile receiver and are moved forward at rates which are necessarily slow Joecause of mechanical inertia limitations, while line increments of the material being received are reproduced through the application of varying degrees of pressure to the printer bar, in order that varying amounts of the carbon will be transferred from the carbon paper to the recordin paper. Such a device for facsimile recording is shown in the patent to Charles J. Young, Reissue #20,152, October 27, 1936.

In another type, a light sensitive recording paper is used and the amount of light permitted to strike the paper is controlled in accordance with the electrical variations transmitted by the facsimile transmitting device. In this type some developing or fixing process generally follows.

In still another type a stream of hot air is directed against a heat responsive recording paper, the intensity of the heat or the amount of hot air being controlled in response to the energy transmitted by the facsimile transmitting device. Another type uses a jet of ink or some colored Application December 23, 1942, Serial No. 469,958

pictures, is somewhat difiicult, since, for instance,

in the carbon paper method, the transfer-of the carbon to the recording paper is somewhat critical in response to the pressure applied to the printer bar. Furthermore, the use of hotair or ink jets is not entirely satisfactory since such systems are diflicult to control and to maintain in proper operation.

The present invention may be generally characterized as directed to dye formation, in which electrolytic action plays an essential part, and is particularly applicable to electrolytic diazotization and coupling.

It is an object of the invention to overcome the difficulties and limitations of the prior art procedures noted hereinabove.

It is an additional object of the invention to electrolytically produce azo dyes, involving elements of novelty as to composition of matter, article of manufacture, and details of procedure.

It is another object of the present invention to obtain diazonium compounds by the action of an electric current on mixtures or solutions containing diazotizable amines and nitrites.

It is a further object to provide mixtures or solutions containing diazotizable amines and nitrites which are adapted to electrolytically react for the purpose of producing diazonium com-'- pounds.

Another object of the invention is to provide solutions or, where feasible, mixtures, of appropriate reagents comprising a diazotizable amine and an ionizable nitrite which are adapted for electrolytic reaction to produce a diazonium compound, and to form azo dyes from such cliazonium compound by reaction with a coupling reagent present in said mixture or solution.

Another object of the invention is a novel supporting material or carrier containing dye forming chemical reagents which will react suitably when subjected to electrolytic treatment.

An added object of the invention is a supporting material or carrier treated with azo dye forming chemical reagents which will react suitably when subjected to electrolytic treatment, said carrier as a result of its chemical treatment being electrolytically conductive.

A further object is a supporting material or carrier impregnated with reagents adapted for azo dye formation when subjected to an electric current, and substantially inert to dye formation in the absence of the eiiectengendered by the electrolytic action.

A still further object of the invention is to provide a supporting surface or carrier which is sat urated or impregnated with a diazotizable amine and an ionizable nitrite, which is advantageously adapted for production in situ of -a rliazoniurn compound when subjected to an electric current.

An important object of the invention 1811;'1910- vide articles of manufacture adapted for facsimile recording in the form of a carrier or supporting material treated with appropriate chemical reagents for forming a dye electrolytically when subjected to an electric current, said dye formation corresponding with electric impulses emanating from .a transmitting source, for example, irorn a scanning station.

An additional object of the invention is to provide .a supporting surface saturatecl or impregnated with .a diazctizable amine, an ionizable nitrite, a coupling reagent, an electrolyte, and other predetermined perfecting ingredients, s supporting surface being thereby .adapted for electrolytic facsimile recording through .azo dye formation;

Other objects, features and advantages of the invention. willbe apparent from the followin detailed description.

the :plesenfi invention, it is proposed to produce the picture of printed :matter on the recording paper in the form of an azo dye, the amount of such dye deposited being a function of the amount of current caused to ilow through the recording paper. When the image :is thus formed, .ior example, by .applican-ts electrolytic azo dye formation, ithe pressure of the printer bar can be maintained constant and the amount of current which is passed through increments of the :paper simply varied in accordance with the light and dark portions present on the picture or printed matter being scanned at the facsimile transmitter. When dyes are so formed by electrolytic action, the varying :half tone shades may be produced by merely regulating :the amount :of the current which is caused to ifiow through the recording paper. 1

The electrolytic diazotization method conte plated herein can .be viewed as deriving from a general concept that mixtures of .a diazotizable amine, for example, .a suitable primary aromatic amine, and an ionizable nitrite, such as a metal nitrite or the like, are stable in mild aikaline solu tion, the amino group being un-ionized and .the nitrite ion "having .a negative electric charge, "whereby diazotization is substantially precluded and no formation .of diazoniumsalt takes place. Diazotization of these compounds may be efiected in't he presence of a suitable concentration of hydrogen ions, usually accomplished by supply- :ing an appropriate quantity .of .acid. "In the present invention, the provision of a suitable hydrogen ion concentration is brought about by the action of the electric current at the anode in an electrolytic cell, thus causing practically immediate diazotization or diazonium-ion formation in the region of the anode, but not before the reagents are subjected to the electrolytic action in the effective zone of the anode. Stated in another fashion, any premature electrolytic diazotization to produce diazonium compounds in accordance with the present invention, is precluded by maintaining such conditions in the solutions of the .amino compound and nitrite reagent that there is no material interreaction until such time as the current is passed through it; as above indieated, this control depends upon the fact that the diazotization reaction will only take place in an acid medium, and this acid medium is made available only 'in proximity to the anode. The main body of the-solution remains fundamentally alkaline or non-acid in character.

Where couplin compounds are present in the reacting mixture, :or are added after diazotization occurs, azo dyes are formed under conditions appropriate to the reaction of the coupling reagent with the diazonium compound. Thus, where mixtures containing amines, nitrites, and coupling compounds are subjected to electrolytic diazotization, and the coupling compound is of the acid reacting type, coupling will occur-substantial-ly spontaneously within an extremely brief interval after passage f the current which results in .the provision of an acid zone adjacent theanode.

While an acldzone is -.created and prevails adiacent the anode, -the1zone adjacent the cathode tends itcjncrease alkalinity as aresult of the current passing through the cell existing between the electrodes. -".Ehesolution as a whole is theretore preponderantly alkaline, despite the presence of hydrogen ions produced in the anode-zone and subsequent ionic migration tends to re-establish the original conditions after the electrolysis, Accordingly, where the coupling reagent is or the type which reacts in an alkaline medium, the general alkalinity :of the solution will cause the diazoni-um salt produced adjacent to the anode to couple with the alkaline coupling reagent at any point removed from the anode to form the predetermined :dye product. Coupling compounds that react in alkaline solution frequently yield better results, where acid coupling compounds are not suificiently reactive for the coupling to be completed before the original alkalinity is restored.

Where the compound is of the type which will couple in an alkaline medium, there mayof course be a slightly longer time element involved to attain the aze-dye formation. This time interval is usually of the order of less than a minute after the paissageof the-current which causesdiazotization. Therefore, while alkaline coupling may require a somewhat longer time interval than that necessitated by reagents which couple in an acid medium, alkaline coupling may, nevertheless, be appropriately classified as spontaneous, similarly to the case :of the coupling in an acid medium.

Various regulations of the procedure obviously may be resorted to sothat both acid coupling and alkali-necoupling may occur during the course of --formation of :a given azo dye. In general, the appropriate selection can be more or less guided, without limitation thereto, by considering acid coupling as the reaction where a diazonium compound attaches itself to the ring of the coupling Lcompound, replacing the active hydrogen which becomes a hydrogen ion and alkaline coupling as the reaction where the diazonium compound attaches to the ring of the coupling compound with the displacement of hydrogen and the hydrogen unites with hydroxyl to form water.

Considering the process as applied to a paper recording sheet in facsimile recording, as will be further considered hereinbelow, when a point on the paper is between the electrodes, positive elecrate becomes very slow and alkaline couplingv accelerates, and usually all of the diazonium compound in the recorded area couples before the paper dries. In general, amino and hydroxy groups direct coupling under acid and alkaline conditions, respectively. Thus, it is possible for both acid and alkaline coupling to be manifested in a given reaction leading to azo dye formation.

Without intending to be restricted to any oi the theoretical explanations provided hereinabove or to any suggestions as to the character of the reactions involved therein, or in the azo dye formation generally, it will be noted that aneX- planation in the form of equations involvingthe production of diazonium salt electrolytically, and

the coupling of this salt, in accordance with the preferred invention embodiments, is presented in U. S. Patent 2,306,471, referred to above. v As previously stated, the preferred procedure in accordance with the present invention comprises adapting the solution for facsimile recording by electrolytically diazotizing an amine, in an alkaline solution which contains an alkaline reacting coupling reagent.

The ingredients utilized in accordance with the invention, and especially in its adaptation to facsimile recording, comprise the following:

(a) An aromatic amine, desirably a primary amine.

(b) Anitrite.

V (c) Analkali.

' (d) A coupling compound.

(e) An electrolyte.

(f) Water or other solvent in which electrolytes ionize.

Concerning the amines required for producing the diazonium compound, substantially any diazotizable amino compound will sufiice. Mainly within the purview of such class of compounds are the primary aromatic amines, and especially where the latter are soluble in mildly alkaline salt solution, and are not too readily oxidized electrolytically or by air oxidation.

Among the amines which may be utilized are monoamino benzene compounds, polyamino benzene compounds, amino-naphthalene compounds, amino polyphenyl compounds, heterocyclic amines with a nuclear attached primary amino group such as the amino quinolines, amino pyridines and amino pyrimidines. The presence of a sulphonate group in such amines tends to enhance the stability of the background of the carrier towards light although the dye may, in some cases, manifest somewhat less fastness to washing. Typical illustrative sulphonates are the sulphonic acids of amino-benzene, -naphtha- 6 le'ne, or -diphenyl compounds and various amino naphthol sulphonic acids.

The following are illustrative lists of-amines and coupling compounds which may be utilized:

Ammas Monoamino benzene compounds Sodium formanilide Aniline omega-sulphonic acid 4-aminoacetophenone .4-aminoacetophenoneoxime Anthranilic acid 4-aminobenzoic acid 3-aminobenzoic acid Metanilic acid Sulphanilic acid 2,5-dichlorosulphanilic acid Z-aminotoluene-B-sodium sulphonate 4-aminotoluene-2-su1phonic acid Orthonitroanilineparasulphonic acid Paranitroanilineorthosulphonic acid Paraaminobenzophenone f Paraaminobenzophenoneoxime Metaaminophenol s-aminosalicyclic acid hydrochlorid Orthoaminophenolparasulphonic acid 2-amino-4-chlorophenol-G-sulphonic acid Orthoaminodiphenylparasulphonic acid Acetoacetanilide oxime parasulphonic acid 2 l-metaaminophenyl-Ii-c a r b o x y -5 p y razolone 1 Hydroxylamine with No. 23 1 Acetoacetanilide hydrazone parasulphonic acid Y Polyamino benzene compounds -(1) All amino groups on the same benzene ring.

(2) At least two amino groups on difierent benzene rings.

. Benzidine Dianisidine V r Solubilized dianisidine Benzidinemonosulphonic acid Benzidine-2,2'-disulphonic acid Benzidine-3,3' -disulphonic acid Orthotolidine-2,2 or -6,6' -disulphonic acid 4,4-diaminobenzophenone 4,4-diaminobenzophenoneoxime 4,4'-diaminostilbene-2,2'-disulphonic acid 4,4:diaminodiphenylaminosulphonic acid.

See footnotes on following page. 7

Naphthalene compounds- Qrt'honaphchionic acid Sodiumna'phthionate Laurents acid Cleves 1.6 and 1.7acids Cleves 1.6 sulphonic acid Peri acid" Disulpho S salt Kochs acid H 4-acetylamino- 1,7-Cleves acid Tobias acid Dahls acid Broenners acid Amino F acid 66. Badische acid 67. Amino R acid Acid IV or C acid 69. 2-naphthylamine-5',7-disi lph'oni'c acid 70. Amino G acid I 71. Naphthanil Red" 73. J acid 74. M acid '75. Gamma acid 76. S acid 1 I 7'7. Chicago'or 2S acid 1 78. Monosodium H salt 1 '79. K acid .80.212 acid (oxyamino) 1 81. R" acid '(oxyaminm 1 Heterocyclic compounds COUPLING COMPOUNDS Benzene" compounds ".2 Resorcinol:

. 4-cl1lororesorcino1 Z-nitroresorcinol Salicylaldehyde Salicylaldoxime 5:-chlorosalicylald'ehyde 5-chlorosalicylaldoxime Orthohydroxybenzalacetophenone Orothydroxybenzalacetophenoneoxim Resorcylaldehyde .Resorcylaldoxime Resorcylic acid Parahydroxyacetophenone Parahydroxypropiophenone Resacetophenone Resacetophenoneoxime Phloroglucinol Metaaminophenol Acetoacetanilide Isonitroscacetoacetanilide- Isonitrosoacetoacetanilideoxime Acetoacetanilideoxime Acetoacetanilide hydrazone 2-chloroacetoacetanilide 2-chloro-isonitrosoacetoacetanilide 2,5-dichloroacetoacetanilide 4 109. 2,5-dichloro-isonitrosoacetanilide 110. Acetoacetanilide-1oarasulphonic acid These chemicals may act both as amines and as coupling compounds. Usually, when involved in diazotization and coupling reactions, some molecules of these compounds act as amines, others as coupling compounds, and the remainder in both capacities, forming mixtures of azo dyes. Many of the other. amines, particularly in the naphthalene series, w1 ll act also ascoupling c0mpounds" if. no hydroxy coupling compounds are present.

'lhis acts as an amine, although it does not contain an ammo group. i

'. Beta naphthol 1,5-dihydr0xynaphthalene 1,7-dihydroxynaphthalene-4-sulphonic acid Dioxy S acid Nigrotic acid Yellow acid Red acid A acid Chromotropic salt or acid 2,7-dihydroxynaphthalene Phenyl J acid Benzoyl J acid Di J acid urea J acid imide J acid M acidv Gamma acid Phenyl gamma acid Chicago or 2S acid Monosodium H salt Chloro H acid Phenyl H acid Acetyl I-I acid K acid 2R acid (oxyamino) R acid (oxyamino) Acetoacetanilide oxime parasulphonic.v acid l-metaaminophenyl 3= carboxytirpyrazclone Hydroxylamine with No. L12 Acetoacetanilide hydrazone parasulphonic acid Orthophenylenediamine Metaphenylenediamine Paraphenylenediamine Chloroparaphenylenediaminedihydiroc h 1- 0- ride 2,5-diaminobenzenesulphonic acid dihydrochloride Diacetoacetyl-parapheny1enediamine Diisonitrosodiacetoacetyl paraphenylenediamine Diacetoacetyl paraphenylen'ediaminediox ime 2,4-diaminotoluene 2,5-diaminoto1uenedihydrochloride 2,4-diaminoanisoledihydrochloride 2,5-diaminoaniso1edihydrochloride Triaminotoluenetrihydrochloride 4,4-dihydroxybenzophenone 4,4-dihydroxybenzophenoneoxime Metadiethylaminophenol' Metadigallic acid (tannic acid) Naphthalene compounds Alpha naphthol Alpha hydroxynaphthoic acid Schaeffers alphanaphtholsulphonic' salt Neville and Winthers acid L acid N-phenyl Peri acid RG acid I Andresens acid Schoellkopfs acid Oxy Koch acid Beta hydroxynaphthoic acid Naphthanil OA Schaeifers acid F salt Bayers or Crocein salt Disodium R. salt Disodium G salt Naphthoresorcinol Miscellaneous compounds 1'77.

Diisonitrosodiacetoacetylethylenediamine Monoisonitrosodiacetoacetylethyle n e d i a mineoxime Monoisonitrosodiacetoacetylethyl e n e di a minedioxime Diisonitrosodiacetoacetylethylenediami n e oxime Diisonitrosodiacetoacetylethylenediami n e dioxime Relative to the proportioning of the ingredients, as a general rule by way of estimate and not restriction, approximately 0.03 gram molecular weights (0.015 for diamines) of amine and of a mono-valent nitrite per liter of solution produce quite satisfactory results. Usually 0.025 gram molecular weights or mols of amine are used per liter of solution for paper that is treated at the recorder, that is, for paper which is subjected to the diazotizable solution substantially at the time that the recording is made.

A comparatively wide range of nitrites are available, the requisite being an ionizable compound, desirably a metallic nitrite. Whereas the examples herein involve the use of sodium nitrite, it should be clear that this compound is referred to merely as illustrative of a convenient material which may be utilized in the diazotization procedure. While nitrite sodium provides entirely satisfactory results, the same may be said of potassium nitrite as well as of many other metallic nitrites. In view of the fact that neutral or alkaline solutions of sodium nitrite are comparatively stable, this reagent is particularly desirable in recording solutions prepared for storage over a substantial period prior to usage.

It has been found that excess nitrite does not impair the background permanence of electrolytic diazotization recordings and is in fact beneficial because it causes a greater percentage of the amine to be diazotized, and consequently permits a decrease in the concentration of amine with no loss in color intensity. Concentrations of 0.025 and 0.05 gram molecular weights of amine and of nitrite, respectively, per 1000 cc. of solution, usually give excellent results.

Similarly, a substantial latitude in choice of alkaline reagent is available, but for purposes of illustration herein, recourse is had to sodium The usual content of sodium hyhydroxide. droxide may be characterized as that required to neutralize all strongly acid groups in the amines and coupling compounds, and to provide a slight excess (usually 20 cc. of normal NaOH per liter or recording solution).

Where the alkalinity pertains to the recording solution and is not particularly critical, simple expedients for its approximate evaluation are available in the form of the so-called Beckman l 10 instrument or other commercial devices. Similarly, a small piece of LaMotte Oleo Red B pH test paper may be immersed in the facsimile recording solution for a few seconds. The alkalinity is satisfactory if the paper turns orangebrown, insuflicient if yellow or orange-yellow, and excessive if red. It should be noted that insuflicient alkalinity is more harmful than excessive, since it impairs the background permanence; on the other hand, a stronger signal in the form of electrical impulse is required from the amplifier, and half tones are impaired, when the solution is excessively alkaline.

As a general matter, the color intensity at full electric current depends on the alkalinity and the amount of diazonium compound iormed. Ihe deepest color is usually formed at a pH of 7.5 to 9 which is not alkaline enough for good background permanence. At a pH of 6 to 7.5, hydroxy coupling is too slow in some cases, and premature non-electrolytic diazotization discolors the paper in others. At the compromise pH range of 9 to 11.5, the color intensity is not sacrificed unduly in order to gain in background permanence.

The diazotizable composition and the treated carrier, such as paper, may be stored a considerable period of time if thesolution ismodcrately strongly alkaline. A pH range of 7.5 to 12.5 is applicable, although best results are obtained Within the range of 10.0 and 11.5. As the pH drops, the stability decreases, the tendency of the background to darken on standing increases, and the sensitivity of the reaction increases.

In lieu of sodium hydroxide, other strong bases may be used, such as potassium hydroxide, barium hydroxide, or-a quaternary ammonium. hydroxide. On a weight basis, the amount of alkali used may vary from 0.01 to 0.12 gram molecular weights per liter of solution, depending upon the original acidity or alkalinity of the other ingredients, and is adjusted to the predetermined pH of the finished solution, which, as above suggested, may desirably be within the range of 10.0 to 11.5.

The coupling compounds are desirably soluble in a mildly alkaline salt solution and preferably subject to the same oxidation limitations asdiscussed above in connection with the amines. Aromatic compounds with hydroxy, amino or active methylene groups, ortho or para, to unsubstituted positions in the ring will usually couple. sulphonic groups have the same effect as in amines. Resorcinol, phloroglucinol, the naphthols and their sulphonic acids, 8-hydroxy quinoline, and some amino naphthol sulphonic acids have given good results. Some amino naphthol sulphonic acids (for example, gamma, H, J, S and 2S acids) may either diazotize or couple. Good recordings may thus be obtained, using the same chemical for both diazotization and coupling. However, most amino naphthol sulphonic acids give recordings that require washing in order to prevent the backgrounds from darkening during storage.

Chromotropic salt is considered the best allround coupling compound, giving darker colors than any of the others having reasonably permanent white backgrounds. The aceto-acetylamino compounds, their oximes and hydrazones, and the isoxazolones and pyrazolones derived from them, give yellow or orange colors, the oximes and hydrazones being most effective. When added to facsimile recording solutions conexample hereinbelow.

The amount of coupling compound utilized may vary between 0.01 to 0.02 gram molecular weights, although 'more'may be utilized without harm. Usually approximately 0.015 gram molecularweights of coupling compound per liter of solution provides excellent results, and a greater amount rarely shows any-improvement in recorded color intensity.

As above indicated, the coupling compound may be-o'f the type which reactsjin alkalinema dium or in acid medium, although the "former is preferable. It is'interesting to note that some amino compounds may function as coupling agents regardless of the pI-I, and many diazotizable primary amines serve-in'the dual function of amine and coupling compound. Underalkaline conditions, the hydroxy-coupling rate of reaction is generally so much greater than the amino coupling rate that substantially little or no amino coupling takes place in alkaline solution when both amino and hydroxygroups are present.

As for the electrolyte, NaCl is quite satisfactory, but there is no intent to be limited to the use of this salt. Other strong neutral electrolytes such as NaBr, KiBr, KCl, LiCl, BaClz, CaClz, MgClz, K2304, Na2SO4, MgSO4, etc., "may besubstituted for sodium chloride. Some dye intermediates are more soluble in potassiumchloride solutions, in which cases the substitution is made. Lithiumzchloride has been found to retard the time of paper drying, but .the same result is cheaper and more effectively obtained by 'the'use of wetting agents. An additional electrolyte'which has provided excellent recordings, while at the same time obviating the corrosive efiect of nascent chlorine, is sodium sulphamate,

naosomnz The amount of electrolyte required is not critical. Low concentrations require more electric current, while excessively high concentrations may cause partial precipitation of the dyeintermediates; About two-thirds of a -mol (a mol equals one gram molecular weight) of total electrolyte per liter of solution is fully adequate. For convenience in making the sodium ion correction to the Beckman pH meter readings, a total sodium ion concentration of 0.64. mol is used. The total 'sodiumpresent in all the other ingredients is subtracted from 0.64,-.theremainder representing the amount of sodium chloride to be added.

"Where NaCl is utilized, itfhas been-found'that the total concentration'of s'odiumions equal to 1.0 gram molecular weight perzliter istquite effective, although good recordings have been obtained in some cases withaslow as 0.1 1andashigh'as 3.0 gram molecular weights of sodium'per'liter.

Substitution of sodium oxalate f'or'part of the sodium chloride retards =thebackground darkening of damp pretreated papenalthough the elec- 1 2 tric current requirements areincreased, and t e halftone response is somewhat'impaired. Oxalates have little effect on the background permanence of recordings exposed .to light -.after drying, and their use is advisable .primarily with damp treated paper.

It is, of course, apparent that water functions as a very desirable and effective solvent within which the diazotization and azo dye formation are carried out. However, various non-aqueous neutral solvents that .permitelectrolyt-es toionize may be substituted forall or a part of the water. If approximately half the water is replaced by alcohols or glycols, the freezing point-of :thersolution is lowered to such an extentthat recorders may be operated outdoors in winter.

Ethyl, methyl and isopropyl alcohols evaporate more rapidly than water, so that the paperidries too quickly in summer but in winter the added speed is desirable. Normal propyl alcoholdries at approximately the same rate as water, and may be used both summer and winter. The tendency of the propanol-water-saltmixture to separate into two liquid phases is-eliminatedby replacing ten per cent of the propanol with ethylene glycol. Larger amounts of the .glycols are unsatisfactory, as their low volatility causes the recordings to be permanently limp andmoist.

Some solvents, notably Cellos'olve,methylicellosolve, andmost denatured ethyl alcohols, gradually react with'the alkali in the recording solution, which eventually becomes acid (unless more alkali is occasionally added), whereupon diazotization and coupling begin, causing paper treated with the solution to become discolored. jNormal propyl alcohol and ethylene glycol do not reduce the alkalinity.

It will be noted that auxiliary chemicalsare of substantial usage, and contribute materially to the control of the diazotization, dye formation, and recording generally. .Such substances as oxalates, antifreeze solvents, hydroxylamine and hydrazine maybe considered either as auxiliary chemicals or as replacements for ,part of the essential chemicals.

An important role may be attachedlto theuse of auxiliary chemicals in connection withthedye formation, and particularly where facsimile recording is .concerned. These substances contribute materiallyto the control of .the diazotization, dye formation, and recording generally.

Urea, thiouera, and, .toa'still greater extent, dicyandiamidinehave been found to improvelthe color intensity. About 1 ml mols of either-of these compounds per .mol of amine are used. Thiseifect is more apparent whencombined with that .due to excess nitrite. .If .a sulphate -.or hydrochloride of these bases is used, sufficient caustic soda or other alkali :must be added to liberate the free base, in ordertomaintain'the proper pH range.

Wettingagents maybe utilized in the treatment of the carrier, such as paper. :Many of such wetting agents and their general ifield'of usage as well as chemical characteristics arerset .forth in the Journal of Industrial and Engineering Chemistrywolume 31,J.une-1939, pages-6439.

Wetting agents which have been found :quite effective aresulfonated ether (see pageo9, vol

ume 31 of Journal of Industrial andsEngineerin'g Chemistry,.January, 1939) as well :asthe sodium salts of aryl'alkyl'poly ether .sulfonate "(p 130, volume .35, J ournal of Industrial. and Engineering Chemistry) and 'dioctyl ester sodium sulfosu'c- 13 ci-nic acid (page 126, volume 35, Journal of Industrial and Engineering Chemistry).

The rate of penetration of the dye forming solution into the carrier or supporting material, such as paper, is most rapid, at high alkalinity and low surface tension of the solution, as well as at high atmospheric humidity. It is in this connection that wetting agents have been found highly efiective in reducing the surface tension sufiiciently for adequate wetting to occur in a brief interval of paper submersion time, desirably approximately six seconds, regardless of the humidity and alkalinity prevailing. As an ex-. ample of the quantity of wetting agent, 0.8 of wetting agent solids per liter of solution has been found to aiford adequate wetting when the paper is immersed. Where the paper is supplied with the dye forming solution by contacting only one side of the paper with a wet roller approximately 1.5 grams of wetting agent per literof solution may be essential.

The desirability of resorting to wetting agents in the recording solutions is emphasized by the fact that without the same it has been necessary to .submerge the paper for at least two minutes to insure adequate wetting on dry days. The use of pretreated paper, i. e., paper treated with recording solution prior to its utilization in the recording apparatus, has heretofore proven impractical for the electrolytic treatment when subjected to moistening by water in the absence of a wetting agent. Differenttly stated, the wetting agent causes the water to penetrate pretreated paper more rapidlythan the solution penetrates untreated paper. Moreover, an additional function of the wetting agent is to cause the recording solution on the surface of the paper to continue penetration until saturation occurs, where excess liquid is available on the paper surface. Any remaining excess Olf liquid is removed by any conventional expedient, such as by a doctor blade or a preheater.

An undue amount of liquid on the paper may function to cause blurring at the instant of printing. Where the interval between paper wetting and facsimile printing is comparatively long, the tendency is for the paper to become partially dry, causing streaking and paper scufiing when the printing is applied. The wetting agents serve to retard the rate of drying at this stage of the operation.

Glycols and other high boiling solvents also retard drying at room temperature andimprove wetting, but they are not as eifective as wetting agents, thereby necessitating much greater concentrations. If the damp paper, after being subjected to recording, is passed overa hot roller for the purpose of drying and ironing it, the glycols require a greater extent of heating, since at higher temperatures they are more efiective than wetting agents as drying retardants. Wetting agents similarly are advantageous in the case of pretreated damp paper which is stored in a moisture-proof container, to be later positioned in a slotted container at the point of unrolling at the recorder.

An element which materially affects color intensity is, the amount of diazonium compound formed electrolytically. It will be appreciated,

"in this respect, that the halftones of photographs except at very low currents where the color intensity drops sharply due to the so-called'threshold value effect. In view thereof, reducing agents as well as high alkalinity serve to detract from the light tones. This threshold eiiect maybe compensated for by resort to color-deepening chemicals, illustrated by urea, thiourea, and dicyandiamidine, which improve the halftone characteristics by accentuating the light tones.

Other substances which tend to deepen the color or improve background permanency are barium and calcium chlorides which may be substituted in part, or'entirely, for sodium chloride as the electrolyte. Such substitution may, however, not bewithout its shortcomings in view of the possibility that the solubility of the dye chemicals may be lowered and on occasion objectionable sludges may be cformed.

extent of diazonium compound formation, and

Through the choice of primary amines and coupling compounds used agreat variety of colors may be'obtained, although orange, red and purple shades predominate. ,In general, the orange dyes give recordings whose backgrounds are more permanent without washing than the reds, purples or blues. Furthermore. it has been found that alpha-naphthalene compounds generally give darker colors, but with less permanent backgrounds, than the corresponding beta compounds.

On the question of background permanence. some amines and coupling compounds, in some cases those having two or more amino or hydroxy groups onthe same benzene or naphthalene ring, may manifest an unduetendency to air oxida tion and it may be desirable as a general expedient to wash recordings made through the use of such reagentswithin a few hours after such recordings in order to prevent excessive background darkening. on storage. Taken as a whole, the remaining amines and coupling compounds .give satisfactory recordings which retain their white backgrounds, or at least do not darken suificiently to impair their legibility and utility when stored several years in a fillelor holder.

' As previously suggested, various chemicals function to retard background'darkening, among which are glycols. These substances are used in the proportion of approximately 100., cc. per liter of solution. In some cases, they reduce darkening due to the slow reaction during storage, but are not as effective with respect to darkening which results fromlight exposure. V

Reducing agents, such as sodium hydrosulphite (Na2S2O4-2H2Ol and acetaldehyde sodium bisulphite (NaOSOz-CHOHCE) tend to retard the darkening action of light, but may not pre clude slow darkening. Quantities varying from 0.002 to 0.01 mol per liter have been utilized with effective results within the scope indicated. The reducing agents specified are merely illus trative, since other reducing agents have a similar efiectp Such other reagents are tartrates, formates, sulphites, thiosulphites, other hydrosulphites than sodium, mentioned above, etc.

The effect of alkalinity upon background darkening has already been recited, and the same applies to the optimum range of pH between 9.5 and 11.0, especially where sodium chloride is used as the electrolyte. Higher pH may cause weakeningand decomposition of the paper, while lower pH may result in partial oxidation and partial self-'diazotization of the amines. The pH of the paper before treatment with the solution is known to effect the final alkalinity of-the treated paer; therefore, if an acid paper is used, the alkalinity of the solution should be increased to com.- pensate therefor. 7

Complex cyanides of iron, chromium, or other metals, in some instances improve the iastness of thedye records to Washing and deepen the shade, or even alter the dye color. Noteworthy is the fact that the dyes are on the whole distinctly faster to washing than the intermediates from which they are formed. As a result of this, washing may be resorted to for removing unused chemicals from the unrecorded areas, thereby leaving intact the dyes corresponding to the subject of transmittal. As a general rule, recordings intended to be washed should preferably be made at a pH range of 8.0 to 10.0 within the broader range of -9 to 11.5; in this way advantage is taken of the greater color strength and increased fastness during such pH range. Urea, thiourea, and dicyandiamidine increase the fastness to washing. Thus these compounds serve thedual function of improving color strength as well as color fastness.

The minimum current which is required to produce a faint-color is referred to as the threshold value. Before diazotization can take place, the initial alkalinity of the wet paper must be overcome. If reducing agents are present they are oxidized by part of the current, leaving less foracidi-ficationand diazotization. Thus the reducing agents referred to hereinabove show this threshold value efiect. With neutral solutions or in the absence-of reducing agents, small stray currents cause streaks and spots of color on unrecorded areas, thereby detracting from the appearance of the recordings and in some cases seriously interfering with the legibility of the small type.

The application of a constant negative potential to the printing mechanism has an eiiect anal- .Ogous to that of high alkalinity in preventing streaks due to stray currents, since the positive facsimile signals must overcome this negative voltage before color appears. This expedient is, however, not without some difficulties in the way of an increased rate of corrosion of the negative electrode, and in the case of certain metals produces a pale negative recording on the back of the paper. It may also tend to eliminate the lighter shades in reproduction of photographs.

Illustrative of desirable embodiments of the invention, the following examples are presented:

Example 1 1 Mols per .Gramsper Name and Liter 250 Liters FEE-MIXED INGREDIENTS B enz,idin e-3-3-.disulphouic Acid (amine) .015 1634. 5 Aetoacetanilide (coupler). 002 .88. 5 ,Schaeifers Salt (couplcr).. .003 231.0 Ohromotropic Salt (coupler)- .010 I 1248.7 Sodium Hydrosnlphite (auxil .003 157..5 Urea (auxiliary) .010 150. 2 Sodium Chloride (electrolyte) .450 6576. 1

SEPARATE MIXTURE Sodium Hydroxide (alkali) .061 620 or 6.10 1 ms. :SodiumJNitritc (nitrite) 060 l0-l3 .=.2 ,or 3:00

I ers. Sodium salt of aryl alkyl polycther .08% 750cc. suliouate (wettingogentlt Example 2 Mols per Grams per Name Liter Liter PRE-MIXE-D INGREDIENTS Benzidine is disulphonlc Acid 015 .6. 538 Chrometropw Salt .015 6. 000 Barbituric Acid 004 .0. 512 Sodium Hydrosulphite 0028 0. 588 Dicyandiamidine' Sulphate 0010 0. 316 Thionrea 0010 0. 070 Sodium Carbonata 030 3. 721 Sodium Chloride .300 17. 536

SEPARATE MIXTURE Sodium Hydroxide, 2.5 Normal. .050 20.0 00 Sodium Nitrite, 5.0 Molal .074 14. 8 cc It will be noted in the above examples that while the ingredients in each instance are separated into two groups, this is primarily indicative of a desirable expedient for packaging or storing the reagents prior to usage. However, considering the compositions from the standpoint of their substantive content, they comprise the reagents specified in both groups.

As illustrative of the preparation of the compo sition of Example 1, the proper amounts of .each of the pre-mixed ingredients are weighed, and all are thoroughly mixed mechanically. A conveni, ent method utilizes an inclined rotating drum containing pebbles or metal balls tobreak upany lumps in the chemicals. The mixture may be stored in bulk or packed in small packages each containing the required quantity.

Since measuring liquids is much more convenient than weighing solids, it is advisable to use concentrated stock solutions of sodium hydroxide and sodium nitrite instead of the corresponding solids. Approximately 2.5 normal sodium hydroxide (102 grams per liter) and 5.0 normal sodium nitrite (345 grams per liter) are adequate. The wetting agent is already in liquid form.

The composition adapted for electrolytic .diazotizing and coupling is prepared by dissolving the pre-m-ixed chemicals and sodium hydroxide in approximately three-fourths the required water, adding sodium nitrite and the remaining water, and filtering or decanting to remove sediment. The wetting agent may be added at any time during or after the preparation, and varies in amount with operating conditions, although it is not critical.

The following table is indicative of expedient amounts of each component utilizable in a recording solution, based upon the two different unit volumes, namely, the quart and the liter:

Pro-mixed Sodium Sodium Total Volume of Ingredlents Hydroxide Nitrite Recording Solution (2.50 Normal) (5.0 Normal) grams cc.

'1 quart 38.181 32.50 23.091 11.356 1 liter 40. 346 34. 34 24. 400 12.000

wow

v 13 propriate proportion. A desirable pH for the The solution is prepared' similarly to Example mp n W n th p ive portions have 3, except that it is clear' and does not require been admixed 15 between 10-75 and filtration. The same recording procedure gives Additional examples are as follows: orange-Brown'recordings on a white background, Example 3 5 Y which turn pale yellow on exposure to light, and

INGREDIENTS Amount used No. Name Chemical Formula Use per liter oi solution I Orthotolidlne 22' disulphonic l0l d.-- I 8011i CH; Amine ..V-.I 5.054 grams.

II Ohromotroplc Salt 0H 0H Coupling Compound 3.640 grams.

more 7 more To dissolve (I) and make the 52 co.

III Sodium Hydroxide (Normal solution)-.-

solution alkaline.

IV Sodium Nitrite (twloe normal solution). To dluotize (I).. 15 on.

V Sodium Chloride (Common sal Elgctrolyte to permit current to 52.5 grams.

,ow. r To totalrvol me ol1000 on.

VI Water In the preparation or th ev s olution, (1), (11 behayelikelExample 3 recordings when washed. (III) and (V) are dissolved inalgout 800 cc. water. The dye is amono azo dyeaus follows. Since the commercial product (I) contains am- 1 monia and some insoluble matter, the solution is HO OH filtered, and (1V) and the remaining water are 85 then added. x a t 1 The formula of the dis-.azodye formed is as V A follows: 1 H

011 on on, f 50.1! V t on on our Hi Hols SOaH r Hols son! Example 4 I V mu my I Amountused No. Name Chemical Formula l Use ,per liter oi solution 1 Sodium Naphthionateune N'rr, mama.-.".-.;-,Q;,.;-, 7.3l52grams.

om; a I I l H Phl luoinol COB Com nd. 1.260 nms.

orog no on D P0 7B1 111 SodiumHydroxlde (normal solution).... mom..- a,some.mid ummer 4000. IV Sodium Nitrite (twioonormalsolutlon)... NBNO)--. Todiozotize m 15m. V Sodium Chloride NnCl Electrolyte to permiteurrent to flow 58.5 grams. VI Water 'HQO To total volume oi 1000 cc, 3 i

ga ta-52c 7 Em t? I .L j "if'r'zii' IINGREDIENTS 2*- Amountused No. Name Chemical Formula Use per liter of solution I 4-Acetylamino-1-7-Cleves Acid NH: Amine 9.228 grams.

. Hos

V NHCOCH:

II Gamma Acid on Coupling com oundandiimiiiewhll;-2390 m.

L I i OaS III Sodium Hydroxide (Normal so111tion).-. NaOH .i To dissolve (I) and (II) and make the 70 cc.

. solution alkaline. IV Sodium Nitrite (twice normal solution).-. NaNOz Same as Example3 cc.

V Sodium Chloride (common salt) NaCldo I i 25.6 grams. VI Water H2O 'Io total volume of 1000 cc.

hea m nis r md ii .fiiisainrles 3' n 2 ears were i'eh fi f h' 4, filtration being unnecessary. Excellent dark purplish-brown recordings'on a white background are obtained. On standing, even in the dark, the background gradually becomes pale purple,

' are employed to'facilitate 'quick'penetration of "'"the solution; from ofito lzdgrams"of-wetting agentsolids per "liter' of recording solution is usually sufiicient for this purpose. Among the but if the freshly made recording is washed with eifects produced are more rapid solution penewatertl'ie' background darkensmuch-more slowly and to a far lesser extent than that of unwashed recordings. The dyeis a=-:mixture, but consists mostly of the following: R

NHCOCH: NH:

Irrespective of the predetermined coloration] to be obtained, dependent upon the reagents util-* ized, the supporting material, such as the paper, after having been appropriately treated with the,

tratfion"-i'nte paper and slower drying after bine with the amine before diazotization weakens the recorded color. If a sulphite with a fairly .1 *high initial ,wetstrengthds used, aymoderate "treatment-gives adequate strength ,w'ithout ex- 5 cessive cOI rryVeakeningM-The treatment is pref- ,erabln-iannlied to the unsized pap,er.'.

reagents, is passed through the facsimile recorder Effective results may be obtained by combinin Wet or moist condition. A desirable facsimile recorder which may be utilized is the bar-helix type, the bar servicing as the anode and the helix ing formaldehyde and urea with the recording solution which has been freshly prepared, glycols being included tostabilize the initial resins wneeareatedwith- "urea-formalde hyde resins, sulphite paper increases in wetstrength td -the- 'pointwhere itbecomes usable, although the tendency of formaldehyde to com-T providing the cathode. However, it is apparent forgned. However, such solutions are not parthat the performance of the recording is not re '50 't c ilarly stable when retained in storage for sevstricted to the-"use of anyparticulartype of ap- --era1--ci y inoe a-s tml prop i n of th paratus. V v amine content is consumed, thereby resulting uilng pbn tact ith th printing el ctrod of -in-a -decrease in recorded color-"intensity. Freshthe.recorder,.the.diazoniumcompoundisformed, ,J 11 78 1??? Qd. EQ HH HS .QifillE WP? l fi l hi 19b. h chcoupleswith.thacornlieeromreneot b fiawtaining dry Dre-treated r a e which has cut. Desirably, the treated or sensitized paper is fed continuously from a roll. Where the paper has not been sensitized, it is initially fed from the roll through the appropriate immersion :bath

'been't reated withthe reagent solution and dried preliminary to its utilization as a recording sheet) may set the resin, and the dry storage condifitions ,serve to prevent or minimize the relafor impregnation with th dye i t di t d tively' slow chemical reaction between the formalauxiliary compounds, the excess immersion solution removed, andthe paper pass'ed direotly to the recorder. 3

The reference'to paper as the supporting matedehyde resin and the amine.

=A fter subjecting thesheet to electrolytic trea menu-especially where facsimile recording is inyolved, the carrier in a dry state is desirably kept "rial or carrier has been recited solely by way of in t folder Protected from posure to light.

illustration Substantially any fibrous material capable of being dyed by an 9.20 compound is within contemplation; including materials el ul osici as fabric}. 6.10m;ana-maea types daylight? IT. with? 93 1e; -Washing' the freshly recorded sheets, regenerated or otherwise. Quite desirable- "sheets thoroughly twithnwatermat the most only results have beenobtainecl-withan all-rag-sheet;--

surface-sized with glue-formaldehyde in order to impart adequate wet strength. Similarly, good results have been obtained with partially parchmentized wood pulp paper. In the case of paslightly-weakens the eoloringof thedye which has been formed; at the same time, such washing substantially improves the permanence of the background.

Under preferred conditions of operation, the re- A 21 i cording paper, after having passed through the facsimile receiver may be subjected to a fixing bath for the purpose of rendering the dye more permanent in-nature and/or to aid in the preservation of the white or neutral characteristic of the background. The paper is then desirably washed, as above indicated, to remove any chemicals which remain in the undiazotized portions of the paper in "order to thereby minimize any tendency toward gradual fading of the color pro-. duced or darkenin of the background when. the recorded copy .is exposed to light and/or air.

In preparing the various reagent solutions for utilization to saturate or impregnate thesupporting material, certain precautions and details of procedure may be advisible, dependent upon the particular circumstances involved. Thus, where all the ingredients of a. solution are neutral or alkaline upon their being dissolved in water, they may all be dissolved together. The sodium and potassium salts of aminoor hydroxy-naphthalene sulphonic acids fall in this class. Where the amines, coupling compounds, or other ingredients are free acids as distinguished from sodium or potassium salts, it is necessary to omit the sodium nitrite from the solution until all the acidic compounds have been dissolved by the excess alkali required to give the proper final alkalinity. Failure to observe this precaution results in the formation of diazonium compounds in the acidic zone adjacent to each dissolving crystal of theacidic compounds, with subsequent coupling and dye formation when the diazonium compound hasreached the alkaline w zone. Such solutions discolor any paper that is treated with them.

On storage, the solutions may tend to darken because of auto-oxidation of some of the ingredients, especially if exposed tolight in clear bottles and to air in partly emptied bottles; sometimes this' oxidation causes the formation of sediment, even though the solution was originally filtered. Nevertheless, good recordings have been obtained with some year-old solutions, at a slight sacrifice 'in background permanence. Solutions that have become dark on standing may be restored to their original color (amber, clear brown, or red) by the addition of small amounts of sodium hydrosulphite.

Where the reagents areretained in their'solid form, all or part of them may be packed in glass bottles, waterprooffiber or tin cans, or any other suitable containers, so that the user merely dissolves the contents of one or two containers in water, mixes the two solutions if two containers are needed, and adds more water until the required volume of solution is reached. In those cases where impurities in' the water or in the chemicals cause sedimentto for the solution may either. be filtered, or allowed to stand several hours to permit the precipitate to settle, so that the clear'liquid may be decanted.

' By separating the rest of the ingredients (in the containers for. dry solids) by layers of salt (which constitutes the greater part of the volume of dry ingredients), any tendency for slow chemical reactions between the ingredients during dry storage is avoided, since salt is inert with results, and avoids the necessity for thawing the ternative procedures are available. These may be listed as involving the following three methods: (a') chemical treatment of paper at the recorder, (b) damp pre-treated paper requiring no treatment at the recorder, and (0) dry pre-treat ed paper requiring treatment with water at the recorder.

Considering the recorder-treated paper, the untreated paper is fed through an immersion bath or over wet rollers, where it becomes saturated with a solution of the recording chemicals. After removal of excess solution by doctor blades, and of excess moisture, by natural evaporation or by a heated roller, the wet paper passesthrough the facsimile recording mechanism. This method is more convenient experimentally, since both recording and paper treatment are combined in one operation. It has the advantage of lower cost for chemicals and paper due to elimination of pre-treating costs, and is excellent for use in commercial high speed recording where properly instructed operators give the recorders frequent attention. It may not be entirely suitable for home reception of facsimile broadcasting, since it involves the handling in the home of chemicals which require an element of care and precaution to avoid spilling, discoloring of furniture and clothes. 7

With respect to the damp pre-treated paper (b) ,the treating and recording operation may be separated, the paper being treated and rewound while still wet, and delivered in sealed moistureproof containers to the recorders. When required for use, the wet roll of paper is transferred to a slotted container in a recorder, from which it is fed to the printing mechanism. This method imposes less strain on the paper than any other wet electrolytic recording method, as the damp paper does not stretch or wrinkle between the slot and the printing point. Consequently much weaker paper may be used. Quick starting with intermittent operation, a desirable feature in telegraph offices, is easily accomplished by manually pulling out the paper for a distance equal to that between the container slot and the printing point. The inclusion of wetting agents in the treating solution eliminates excessive drying of the paper between the container slot and the printing point during normal operation.

The shelf life of damp treated paper varies with the chemicals used and with the alkalinity.

Usually, the interval within which it should be utilized extends for slightly less than three months from the time that the paper has been prepared. Refrigeration, even with Dry Ice, does not harm either the chemicals or the paper and desirably functions to increase the shelf life. A temperature just above the freezing point of water has shown indications of providing the .best

paper before use.

Both metal foilwrappers and tin cans with or without internal coating have been utilized for packaging damp pretreated paper. In the case of the cans, a tendency toward rusting is manifested, and for this reason the metal foil is preferable. Tinfoil gives better results than either lead or aluminum foil, but it is believed that the moisture retention may not be as effective as in'the case of a sealed metal can. The acidity of asphalt-laminated paper causes discoloration of the outer layers of the pre-treated paper. Preferred results may be obtainable by use of a metal foil wrapper on the treated roll of paper, together with a waxed fiber can, desirably with a screw top that is waxed after being closed.

In accordance with the above description, it

25 that they should be of the type which enter into the'compositions of the" dyes formed during electrolytic diazotization. Among the contactelectrodes which havebeen utilized are stainlesssteel, tungsten, molybdenum, platinum, and platinumiridium. .In' general, the hard, inert metals such as platinu'm iridium and the stellites provide the best results as recordinganodes. Non -magnetic stainless steels similarly give good results, but the colors differ from that produced by the platinum or stellite, and maybe less attractive in appearance, possibly attributable to collateral reactions involvingthe iron. Ordinary: steels which are strongly attracted by magnets-do not permit any diazotization reaction, but, onoccasionJthey' produce a moderatelypale greenrecording which is believed to result from oxidation of the inter mediates. In the case of 1 alloy electrodes, the percentage of azo color resulting from diazotization appears to increase asthe-magnetic characteristics of the alloy decrease. By way of explanation as a plausible hypothesis, it may be that the magnetic metals create a strong magnetic field when the current passes, and this magnetic lfield orients the electrically charged ions in such-direce tions and in such mannerthat they preclude 'the possibility of diazotization.

Copper alloys and electrodes generally made from copper or nickel tend to inhibit electrolytic diazotization recording and are, therefore, as a general matter not satisfactory for use as recording anodes, although they give excellent results as cathodes. In this category is the berylliumcopper alloy.

Tungsten generally provides satisfactory recordings, but it manifests a tendency. to build up a non-conductive coating, thereby requiring more signal current for eifective recording as well as the occasional necessity for reversing the current during a brief interval in order to remove the coating.

The tendency is for the cathode to indicate substantially less electrolytic wear than the anode, since it is attacked only by nascent hydrogen and by increased alkalinity at the time of current flow; With a bar-helix type of recorder, the cathode is desirably in wire form, and the principal wear is due to abrasion which gradually renders the wire flat. The beryllium-copper cathode necessitates more frequent replacement than the anode when the latter is either platinum-iridium or stellite. A cathode helix wire of stellite may outlast several stellite or platinum-iridium anode printer bars.

It will be apparent from the foregoing that the use of compositions within the scope of the present disclosure enables the production of dyes and pigments by subjecting solutions or mixtures of chemicals to electric current. Such dyes or pigments may be obtained in the form of a paste, powder, or as a liquid solution, and subsequently adapted for use as coloring paints, inks, etc., or for dyeing various materials. It is within the contemplation of the invention to produce such dyes or pigments by intermittent or continuous reaction. Materials such as clothing, piece goods, yarn, paper, and generally any fibrous material susceptible to dyes, and particularly azo dyes, fall within the purview of the present disclosure. They may be treated by immersion in a container filled with a solution of predetermined ingredients and subsequently subjecting such solution to the flow of an electric current in order that the dye may be fixed in or on the materials immersed therein; thus, the dye application may be. in. 1211.6

26 formroi'; alsurface' coating or a' dyeingiwithi'n ithe fibrous structure. Definitely contemplated isthe formationofthe' dye insitu." I I While I have-described my invention in accord= ance"with-preferredembodiments"as to compositions, articles of manufacture, and procedure; .it is apparent that many variations and modifications 'bothf as lt'o procedural details, compositions of matter, and 'articlesof manufacturamay b'e made without departing from the scope ofequivalents withinthe purview and spirit of the in- {Us I The term "facsimile" as used herein is intended to involve not only the reproduction on the re cording material. of a pre-existing subject, for example a photograph which is scanned and reproduced in accordance with .the impulses em-' fanatin'g [from the scanning operation; but also embraces the recording of subject matter the process: of creationor formation without a 'Jphys- 'icallypre-existing subject. As illustrative of this latter oategory wouldbe the recording of simply 'rnental preconception, for example a' pattern orfdesign; either of a singlecolor and 'fshades jthereoffor 'multicolors, which is Erecorded in accordance with an: appropriate manual or automatic variation of the electric impulses delivered ito' thelectrodes. Similarly in'zthis categoryJ is intndd"the recordingof an arbitrary or haphazard design, pattern or other subject, for example one secured by haphazardly or arbitrarily varying electric impulses delivered to the electrode by punching keys on a master keyboard having suitable electrical connections, by manually or automatically varying resistance, or the like.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A fibrous sheet material for the electrolytic formation of an azo dyestuif thereon having the surface thereof uniformly treated with an aqueous solution of a dyestuff forming composition consisting substantially of a diazotizable primary amine, a suflicient quantity of an alkali metal nitrite to produce the nitrite ions necessary for diazotization of said amine under the influence oi the electrolyzing current, a water soluble neutral inorganic salt in addition to said nitrite as the electrolyte in an amount to insure passage of the electrolyzing current, a suflicient quantity of an azo dye coupling component to couple with the diazonium compound when formed to produce an azo dye, and a quantity of alkali surficient to impart to said composition a pH on the alkaline side to therebypreclude diazonium salt formation until the fibrous sheet material is subjected to the action of the electrolyzing current said fibrous sheet material being free from any azo dyestufi.

2. The article as defined in claim 1 in which the solution has a pH ranging from 9 to 11.5.

3. The article as defined in claim 1 in which the diazotizable amine is an aromatic polyamine.

4. The article as defined in claim 1 in which the composition contains a wetting agent to facilitate application of the composition to the fibrous sheet material.

5. The article as defined in claim 1 in which the composition contains a compound to improve the color intensity of the azo dyes, said compound being selected from the class consisting of urea, thiourea and dicyandiamidine.

6. The article as defined in claim 1 in which the ionizable nitrite is sodium nitrite, the elec-