US2459521A

US2459521A - Electrolytic recording

Info

Publication number: US2459521A
Application number: US558717A
Authority: US
Inventors: Harold G Greig
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1944-10-14
Filing date: 1944-10-14
Publication date: 1949-01-18
Anticipated expiration: 1966-01-18

Description

Jan. 18, 1949.

H. G. GREIG ELECTROLYTIC RECORDING Filed Oct. 14, L944 INVEN TOR. fmpam 6; 6/954;

ATTORNEY Patented Jan. 18, 1949 ELECTROLYTIC RECORDING Harold G. Greig, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 14, 1944, Serial No. 558,717

12 Claims.

The present invention relates to the electrolytic production of azo dyes in the form of images on a traveling web or band and particularly to the production of such dyestuff images in facsimile recording while employing as a component for the production of the dyestufi images, a stabilized diazo amino compound.

It has been proposed in the past to produce images or records on a receiver by means of an electromagnetically controlled printer bar specifically in connection with facsimile recording. By the term facsimile recording as used herein is meant not only the reproduction on the receiver of'a pie-existing subject but also the reception of subject-matter in the process of creation or formation. This method has been found to give satisfactory records. However, the method is not entirely free from objection, particularly from the standpoint of the speed at which the records are made and the wear on the printer bar.

In an effort to improve upon this method, experimentation was conducted with recording involving the utilization of an electrolytic current designed to produce on the receiver, azo dyestufi images or records. Three methods were devised for the purpose of effecting this result, one comprising the electrolytic diazotization of a primary aromatic amine and an electrolytic coupling of the so-formed diazonium compound with a coupling component, another comprising the electrolytic coupling of a preformed diazonium salt with a coupling compound, and the third comprising the electrolytic oxidation of an oxidizable dye. These three methods, as compared to the electromagnetically controlled printer bar method have the advantages of speed and avoidance of wear. on the recording parts of the mechanism. Of these three methods, the first was found to be the most efficacious. The second method, involving the electrolytic coupling of a diazonium salt, has the disadvantage that the diazonium salt is light-sensitive and hence of little stability. The third method, involving electrolytic oxidation, employs compounds which are oxidizable by the oxygen in the air. The receiver impregnated with these compounds is therefore not storage stable. .Furthermo're, since the compounds are oxidizable in the air, the records obtained do not have background permanence due to air oxidavtion of the compounds on the receiver at the good records, the records do not represent the optimum in these two important aspects: (1) :shade and depth of color of the images and (2) background permanence,

The azo dyeswhich give the best records are dark blue, green and black dyes. While there are many components employed in the manufacture of azo dyestuffs which yield yellow, orange and red dyes, there are not so many components which give dyes simulating a black shade. The monoazo dyes which possess such shades are metal complexes of the dyestufi, usually with a metal such as chromium. The other dyes having such shade are trisazo dyes. The difficulties of introducing a metal into a preformed dye serving as an image record with the production of a modified record, are self-evident. Attempts to produce satisfactory records in this way met with little or no success.

It is of course possible to produce a record of a trisazo dye by starting with a receiver which is dyed with a monoazo dye and by effecting the formation of the 'trisazo dye under the printer bar. This, however, means that the receiver is originall dyed, making it difficult and complex to handle the receiver prior to its use.

There are certain primary amines which upon diazotization and coupling yield deep blue dyes. Primary amines of this character are benzidine, dianisidine and the like. These compounds, however, are insoluble in water and hence cannot be used in the electrolytic diazotization and coupling method.

It has been found thatwith the electrolytic diazotization and coupling method, the impermanence of the background is attributable to three possible factors. The first of these involves the spontaneous formation of the dyestuff of which the record is composed. The coloring produced in this way, however, is dischargeable by alkaline sodium hydrosuifite solution. Another possibility involves oxidation of the coupler. The color thus produced also appears to be dischargeable. The third factor involves oxidation and polymerization and the color produced in this Way is not dischargeable.

It has been found that coloring produced by the last of these methods is enhanced by primary aromatic amino groups, particularly when these are present in the coupling component. Attempts to modify these groups Or to modif the structure of the various couplers used in the electrolytic diazotization and coupling method so as to avoid this latter type of coloration have given some improvement but have not completely alleviated the condition.

It has now been discovered that the disadvantages inherent in the utilization of the electrolytic diazotization and coupling method can be nicely avoided by producing the image records by reacting undcr the influence of an electrolytic current, a coupling compound with a diazonium compound stabilized by means of an organic amine. These compounds are known in the dyestufi art as diazoamino compounds. Such comof an electrolytic current, a diazoamino com pound and a coupling compound.

It is a further object of this invention to produce color images by reacting under the influence of an electrolytic current a diazoamin'o compoundand a coupling compound.

It is a further object of thisinvention to electrolytically produce azo dyestufi records which are of a dark shade simulating black and which have improved background stability.

It is a further object of thisz invention to pro duce dyestuffl image. records by' submitting to electrolysis a. diazoamino compound and a coupling': compound while insuring regeneration of thevdiazonium compound forcoupling withth'e.

coupling compound;

Itiisla'nfurther objectofthiszinvention to produce dyestufiszimagerrecords whileutilizing as one i of? the components: water-insoluble: primary aromatic'uamines;

It is; a further: object of. this: invention 7 to" stasbilize the coupling compound used inxtherformation: of azo dyestuffr images. byv electrolysis;

It is a further object of this invention to deepen the shades ofelectrolyticallyproduced dyestufi imagerecords byincreasingtheconcentration of the dyestuffs: insaid images;

Other and further" objects: willbecome apparent as :the description proceeds.

It has beenrpointed out that' the diazoamino compounds. with 4 which the; present invention is concernedhave been utilized in theadyestufi; art. These diazoamino compoundsrare obtained by reacting inian' alkaline solution a.- diazonium compound with an organic amine. which doescnot .eas-

ily, couple to form an azotdye. The'product which. isthus obtained: is: capable. of regenerating the diazom'um compound upon treatment with. hot steam;.acid vapors; strong-acids and'the like. If this; regenerationzberaefie'cted in the: presenceof a coupling compound, coupling,v ensues: with: the formation of a dyestufi image.

lnitherdyestuff art; these. compoundssare used in one of. two methods; In the first method; fabricsandthe likearei uniformly dyed by; ime pregnating, the fabric: with: the: stabilized diae zonium compound and; regenerating: the;diazoni;- um compound .inthe presence ofra. couplingcomepound; The second method involves printing a design-,ona. fabric with a paste containing," the diazoamino compound and .a coupling. compound and regenerating: the diazonium compound by an aiterdevelopment procedure. It will become apparent-fromv whatv will besubsequently stated; that the presentmethod. in its. contemplation of the use of the diazoamino compounds isvclearly distinguished from the utilization of such diazo+ aminocompounds 'in the dyestufi art.

,The diazoamino compounds may beformulistically represented as follows:

wherein A isan arylradical, and X is a radical of an organic amine, the amino nitrogen atom of which is linked totheazo group; When these compounds are treated with-steam, an acid or the hot vapors' of an acid, the'compounds are split along the dotted line-indicated in the for mula. The diazonium compound whicli has thus Til been sprung is now capable of reacting with a coupling compound of the type usual in the formation" of azoidye's to give a dyestuff;

The diazoamino compounds falling within the above general classification and which have been found suitable for use in my process may be more specifically classified under the following formulae:

, R1 A'[N=NN/ Ra In these formulae',,R1- andRlarehydrogen; an aliphatic, araliphatic; cy'c'loaliphaticoraromati'c radical, R2 an'd'Rl are'an' aliphatic; aralipliatic; cycloaliphatic oraromatic." radical, A and: A" are.

' aromatic radicals, Z"represents theatoms' neces sary to complete: a" nitrogenous heterocyclic" ring system; and :ris l'or 25 Suitable aliphatic radicals as represented by; R1,.R2, R3. and R4 are alkyl. radicals, such? as ethyl, methyLpropyLbutyl, isopropyll isobutyl, amylj, octyl andthe like; hydi'oxyalkyl radicals such as: ethanol; propano-l, butanol, hexanohand the. like, carboxyalkyl radicals; such as carboxy ethyl; carboxy methyl, carboxy propyl, carboxy, butyl and the" like, sulfo alkyl radicals; such as sulfo' methyl, .sulfo ethyl; sulfo propyl, .sulfo: butyl and" the like; Suitable? araliphatic values? forRi; R2, Ri andRii are benyl and the like; The cycle? aliphatic radicals may be cyclopentyl; cyifloliexyl',- hydroxycyclohexyl, sulfo'cyclo'liexyl; carb'oxycy, c'lohexyl and the like: The" aromatic" radicals contemplatedby' Bi and R2" may' be mon'osulfo benzoic acid," disulfobenzoic acid and the like;

The aromatic radicals represented by A and A" are members'of the-benzene, naphthalene; an thracene; diph'enyl; and" diphenyl" ether: series; The and rings of these radicals may contain substituents such as alkyl, such as ethyl} methyl, propyl and the' lilde; alkoxy, such as -m'ethoxy, ethoxy and the like, halogen, such as chlorine and bromine, nitro; amino; ac-ylamino; sucli as acetylamino, benzoylamin'o; naphthoylami'n'o; and the like, carboxy-a-ndsulfonic-acidfigroupss car bamyl such as benzene carb'amyl; 8 hyd'r'oxy-3-6' disulfo naphthalene carbamylland tlie likee may be a pyridine, such as amino-alpha-carboxy pyridine, amino-pyridine sulfonic acid, aminopyridine, dicarboxy pyridine, and the like, pyrroles, such as alpha-carboxy pyrrolidine, alphai-alpha- -carboxy pyrrolidine, pyrrolidine alpha sulfonic acid and the like, piperidines such as piperidine, beta-carboxy piperidine, alpha-carboxy piperidine, piperidine-gamma-sulfomc acid, morpholine, carbazole, tetrahydraquinoline, tetrahydracarbazole, hexahydrocarbazole and the like. Many of these compounds and their methods of preparation are known in the dyestufi art, as may be seen from a reference to U. S. P. 1,882,- 556; 1,882,561; 2,005,347; 2,051,148; 2,078,387 and 2,099,091.

Specific primary aromatic amines which after diazotization may be converted to diazoamino compounds by treatment with an organic amine, and specific organic amines suitable for such conversion are listed below:

AMINES TO BE DIAZOTIZED Benzidine Dianisidine Naphthionic acid Alpha naphthylamine-4.8-disulfonic acid Alpha naphthylamine--sulfonic acid Beta naphthylamine-5-sulfonic acid 1-amino-naphthalene-3.6-disulfonic acid Anthranilic acid Benzidine-3.3-disulfonic acid 4-diethanolamine4-amino azo benzene l-amino diphenylene oxide l-amino diphenylene sulfide 1-amino-2-meth0xy-5-chloro benzene 1-amino anthracene 4-amino diphenyl 6-amino-3-benzoylamino-1.4-diethoxy benzene tolidine and the like.

STABILIZING AMINES Ethanolamine Diethanolamine Sarcosine Diisopropanolamine Morpholine Cyclohexylamine 2-5-dihydroxy dicyclohexylamine -3'- carboxylic acid p-hydroxy cyclohexenyl glycine Methyl glucamine Alpha-carboxy pyrrolidine Alpha-1-a1pha-2-dicarboxy pyrrolidine Carboxy-piperidine Loiponic acid Beta-carboxy-piperidine Tetrahydroquinoline Piperidine Carbazole Diglycolamino acid Benzyl-xylamine 4-sulfo-2-amino benzoic acid Dibenzylamine-disulfonic acid Taurine Cyclohexylamino-acetic acid 2-methylamino-4-sulfo benzoic acid Methyl mannamine Dimethylamine Diethylamine 'Dibutylamine Examples of stable diazoami'no compounds i1'- lustrative of those which I have employed in carrying out the invention are the following:

1 mol of diazotized 4'-diethanolamino-4-aminoazobenzene 1 mol of diethanolamine 1 mol of tetrazotized dianisidine 2 moles of diethanolamine 1 mol of tetrazotized benzidine-3.3-disulfonic acid 2 moles of diethanolamine 1 mol of tetrazotized benzidine 2 moles of diethanolamine 1 mol of diazotized naphthionic acid 1 mol of diethanolamine 1 mol of diazotized naphthionic acid 2 moles of diethanolamine 1 mol of diazotized naphthionic acid 1 mol of diiso propanolamine 1 mol of diazotized naphthionic acid 1 mol of monoethanolamine 1 mol of diazotized naphthionic acid 1 mol of morpholine 1 mol of diazotized alpha naphthylamine-4.8- disulfonic acid 1 mol of diethanolamine 1 mol of diazotized alpha naphthylamine-4.8- disulfonic acid 2 moles of diethanolamine 1 mol of diazotized alpha naphthylamine-5- sulfonic acid 1 mol of diethanolamine 1 mol of diazotized beta naphthylamine-B-sulionic acid 1 mol of diethanolamine 1 mol of diazotized naphthy1amine-3.6-disulfonic acid 1 mol of diethanolamine 1 mol of diazotized anthranilic acid 1 mol of diethanolamine 1 mol of tetrazotized dianisidine 2 mols of sarcosine 1 mol of diazotized naphthionic acid 1 mol of cyclohexylamine 1 mol of diazotized naphthionic acid 1 molof 2.5-dihydroxy dicyclohexylamine -3'- carboxylic acid 1 mol of diazotized naphthionic acid 1 mol of p-hydroxy cyclohexenyl glycine 1 mol of diazotized naphthionic acid 1 mol of dibutylamine 1 mol of diazotized naphthionic acid 1 mol of di-Z-ethylhexylamine 1 mol of diazotized naphthionic acid 1 mol of 4-sulfo-2-amino benzoic acid 1 mol of tetrazotized dianisidine 2 mols of 4-sulfo-2-amino benzoic acid 1 mol of diazotized naphthionic acid 1 mol of alpha-hydroxy pyrrolidine 1 mol of diazotized naphthionic acid 1 mol of gamma-hydroxy piperidine 1 mol of diazotized naphthionic acid 1 mol of carbazole-Z-sulfonic acid 1 mol of diazotized naphthionic acid 1 mol of alpha carboxy pyrrolidine 1 mol of diazotized naphthionic acid 2 mols of morpholine The diazoamino compounds are employed with any of the couplers usual in the manufacture of azo dyestuffs. A list of couplers which ma be employed are, for instance, disclosed in Solomon U. S. P. 2,306,471. It is to be borne in mind,

however, that certain couplers give better results than others, and this is particularly true with regard to chromotropic acid. Other couplers by which very satisfactory records can be obtained are:

p-Sulfo-phenyl methyl pyrazolone H acid Phenyl I acid Chloro H acid 1-naphthol-4.8-disulfonic acid Acetyl H acid Naphthol AS "Beta naphthol Naphthol RF Ethylated beta naphthol A mixture of chromotropic acid and diacetoacetyl ethlyene diamine.

Of these various couplers, chromotropic acid. has been found to give records which excel from the standpoint of darkness of shade and background permanence and the chromotr'opic acid is therefore preferred.

It has been previously stated that the diazoamino compounds are prepared according'to the prior art by diazotizin-g a primary aromatic amine and reacting therewith in an alkaline solution, an organic amine that does not easily couple to form azo dyes. It has been found that the relative proportions of the amine acting as a stabilizer to the diazonium compound is of marked significance In any case, it is necessary to use an excess of the stabilizing amine over the quantity theoretically required to produce stabilized diazonium compounds. If the diazo'amino compound is insoluble, there should be used in itspreparation an amount of the stabilizing amine ranging up to 0.5 per cent excess of theory. On the other hand, if it is desired to produce a soluble diazoamino compound, a greater excess of the stabilizing amine is required, ranging up to 2.62 mols to 1 mol of the diazonium compound. If the amounts of the stabilizing amine exceed the proportions given, the sensitivity of the recording solution is thereby substantially depressed. It is therefore advisable to bear these ratios in mind in compounding the stabilized diazonium compound.

One of the particular advantages in the utilization of the diazoam-ino compounds is that they may be: utilized either in the form of water-i nsoluble compounds or in the form of water-soluble compounds. Previously, stress has been placed upon the fact that compounds such as benzidine, dianisidine, and the like are primary aromatic amines which upon diazotization and coupling yield dyest'ufis simulating shades of black. By employing the diazoamin'o compounds rather than by proceeding according to the el'ec-- trolytic' diazotization and coupling method, it is possible to use such amines in the preparation of the records. The utilization of the d-iazoami-no compounds, therefore, permits the electrolytic recording method to be expanded to include the utilization of those normally water-insoluble primary aromatic amines which have been found to yield the darkest shades of dyestuffs.

In the dyestufi art, it is normally not desired to utilize water-soluble d-iazoamino compounds which have the solubilizing group in the original diazonium nucleus for the reason that these cornpounds upon coupling do not give dyestuffs of the fastness required in the textile industry; However, for the preparation of records by the electrolytic method, it is desirable to use such water-soluble compounds for the reason that-during the electrolytic action dyestuffs are produced having a fastness' sufficient for the facsimile recording art.

Water solubility of the diazoamino compounds may be efiected either by including water-solubilizing groups in the primary aromatic amine which is to be diazotized, in the stabilizing amine, or in both.. For instance, diazotized naphthionic acid coupled with sarosine will give a water-soluble product in which solubilizing groups are present in both the diazoniu'm compound and in kfalinit'y can be efiected by the utilization of in-' organic hydroxides, such as sodium hydroxide, potassium hydroxide, or the like.

, Other ingredients may also be employed to fac'ilitate the operation. Thus penetration of the receiver by the recording composition is facilita'ted by the use of a wetting agent such as alkyl naphthalene sul'ion'ic acids, for example but'yl naphthalene sulfonate and the like, the condensation product of asulfonated benzene with chlorinated kerosene, sarcosines and taurines, the N- atom of which is acylated with a high molecular weight fatty acid for example oleic, palmiti c and the like.

Improved half tones are ensured by using a buffering agent in the recording composition The buiiering agent may be b'orax, sodium acetate, sodium carbonateor the like.

Where a question of stability is involved "this can often be resolved by resorting to the use of reducing agents such as hydrazine, hydroXyl amine and the like. While the reagents enumerated above are not essential, they will in some instances lead to an improved process and the formation of improved images, and their use in general is recommended. 7

The receiver may be prepared for the electrolytic treatment in various ways. It may, for instance, be impregnated with a solution of the aforementioned essential ingredients and subjected to the action of an electrolytic current. On the other hand, the receiver may impregnated with an organic solvent solution of a watch-in soluble diazoamino compound, such as analcoholsolution, and the receiver subjected to an electric current in an electrolyte solution containing the coupler. Furthermore, a paste may be made of the components, the paste applied to the receiver, and the receiver subjected to electrolysis in an electrolyte solution. The invention contemplates the utilization of any method for bringing a receiver under the influence of an electrolytic current in the presence of a stabilized diazonium compound, an electrolyte and a coupling compound so as to effect a springing of the diazonium compound from the 'di'azoamino compound and a coupling of the same with the coupling compound to produce dye images in consonance with the impulses imposed upon the electrolytic cell. However, it has been established that the most practical method of carrying out the invention is to employ anelectrolyte solution containing a soluble diazoamino compound and a soluble coupler. Such as electrolytic solu- An apparatus by which the invention-may be effected is diagrammatically disclosed in the accompanying drawing.

ON rm: DRAWING Referring to the drawing, it will be seen that the apparatus comprises a drum A mounted on a drive shaft 0. The drum is provided with a helix B which is made of a conducting material and is connected in any appropriate manner, such as through the drive shaft C to ground D.

The signals representative of the image to be recorded are applied on the grid of an output amplifier tube E, the anode Y of which is connected to a positive source of voltage F and the cathode G of which is connected to the printer bar H. By this arrangement, output signals from the tube are taken across the cathode output resistor J, one end of which is connected to the cathode G and the other to ground D. The carrier K which is a traveling web or band of paper or fabric, moves intermediate the printer bar H and the drum A. The carrier K is impregnated with an electrolytic solution comprising a stabilized diazoamino compound, an electrolyte and a coupler.

When current flows through the printer bar to the ground through the paper K and the helix B, the diazoamino compound is decomposed with the formation of a diazonium compound, and coupling ensues between the coupling component and the diazonium compound, with the formation of a dye. The dye will appear in a concentration dependent upon the impulses to which the printer bar is responsive.

The helix is the cathode or negative element of the cell and is usually formed of berylliumcopper alloy, stainless steel or platinum. The printer bar, on the other hand, constitutes the anode element and is usually formed of platinum, platinum-iridium or stellite. The quantity of dye which is produced by the current passing between these elements is in proportion to the current flow and the time it is flowing and is determined by coulombs per square inch. The current flow is generally so set that a maximum depth of recording is represented by full current from the tube. Lower values of current give half tones. While the color formed is proportional to the current flowing, this proportionality is not necessarily linear.

I have previously referred to the fact that it was known in the dyestuff art to decompose diazoamino compounds to regenerate the diazo nium compound for coupling by resorting to the utilization of steam, acid vapors, strong acids and the like. There is, however, a very marked distinction between the procedure adopted for use in the dyestufi' art and the course of the reaction in my present electrolytic recording method. In the dyestufi art the whole fabric is permeated with the decomposing agent and should this be acid the entire fabric becomes acidic and remains so until the acidity is neutralized by the utilization of an alkali. In other words, the acidity is permanent rather than fugitive. The degree of acidity is uniform throughout. Consequently, if the fabric is uniformly impregnated with the diazonium compound, upon treatment of the fabric with a coupler and the decomposing agent the fabric will be uniformly dyed throughout.

It the electrolytic method, on the other hand, the color is developed only on one surface of the receiver. the electrolyzing current flows through the fabric between the electrodes, only a very small Thus if the receiver is a fabric when,

part of the receiver, 1. e., that which is in direct contact with the surface of the printer bar (anode) and which is backed by the helix (cathode) becomes acidic. The reverse side of the fabric becomes more alkaline. This condition, however, is only transitory for as soon as the current flow ceases the acidity is lost completely and alkalinity is automatically restored. The time of the current flow for any one particular spot is exceedingly small, being less than $1 of a second for normal recording speeds. The degree of acidity is variable being dependent on the current and the time of flow, and this mechanism thus permits a gradation in the amount of color formed, whereby the production of half tones is made possible. Such procedure is impossible in the dyestuff art since a gradation in the amount of color can only be effected in that method by limiting the amount of the diazoamino compound or coupler in the fabric and cannot be effected by control of acid development of the color.

There are other factors existing which also serve to distinguish the electrolytic method, on the one hand, from the prior art dyestuff method, on the other hand. The degree and permanence of acidity in the electrolytic method, as previously pointed out, is not comparable to the degree and permanence of acidity in the prior art method. Whether it is the acidity which prevails at the anode in the electrolytic method by which decomposition of the diazoamino compound results is not known and has not been ascertained. It is known, however, that during electrolysis a strong oxidizing action is present. This oxidizing action probably plays some part in the breaking of the diazoamino compound since the art recognizes the fact that many organic linkages are broken by the action of strong oxidizing agents.

Furthermore, during electrolysis nascent chlorine and oxygen are present so that in addition to the formation of the dye by coupling, side reactions undoubtedly ensue. These other reactions influence the course of the reaction, particularly with regard to the shade of the color formed. It is thus evident that the procedure herein contemplated cannot be considered even analogous to the prior art procedure of producing azo dyestu'lf from coupling compounds and stable diazoamino compounds.

Considerable attention has been paid above to the various types of coloring which produce background impermanence in electrolytic recording. It was stated that the coloring apparently attributable to oxidation and polymerization of the coupling compound is facilitated when there is present in the electrolyte a component having a primary aromatic amino group. Very surprisingly, however, the diazoamino compounds which are per se stable to light, exert a stabilizing action to light upon the coupler precluding to a farreaching extent the aforesaid discoloration attributable to oxidation and polymerization. This,

of course, means that after the electrolytic treatment the records obtained are much more permanent in their background on exposure to light than the records obtained by other electrolytic methods. An indication of the degree to which the diazoamino compounds affect background stability may be seen from the fact that records made with the best solutions for the electrolytic diazotization type recording showed more discoloration when exposed to light for one day'than records made according to the present method andexposed to light for one month. The diazoai-hlino ctlirnpounds,- therefore,- have some very peculiaraction onthe coupling agents which leads to high light stability of the records, a fact ii hich could never have been deduced from the nonanalagous employment of the diazoamino com-pounds in the dyestufi art in general.

The peculiar action of the diazoarnino compounds in assuring background permanence is also brought home by this further finding. In

the electrolytic diaz'otization method, attempts light and this is particularly true when the ratio between the diazoamino compound and the coupler is maintained substantially constant. The importance of this factor cannot be overemphasized; since it solves one of the very annoying problems dealing with the shade of color which is always incidental to the utilization of the other terms of electrolytic recording.

The iollowing examples will serve to illustrate my invention, although it is to be understood that the invention is not restricted thereto.

Examp I 24.4- grams of dianisidine are slurried in 40cc. of 38% hydroclhloric acid and after being thoroughly wetted out, aDprO motel? 500 grams of water and 500 grams of ice are'added thereto.

.3.8 grams o s dium n r te are ii ss vccl i a mallam unt f wat r a d e so ut on s ru in o th slurry at a temp r ur of l to 15 C- An excess of nitrous acid is maintained for half ar hour and then is removed by the addition of a small amount of sulfamic acid. This procedure 4 can be followed by spot tests on starch=i0dide paper.

grams of activated charcoal are then added the solution stirred for minutes. The solution is then filtered.

The tetra ized di ni id n hus obt i is hen added slowly to a o -fiqnl 2. ams o diethanolamine and, 36.8 grams of soda ash in 600 parts of Water while rapidly agitatin ,A reaction temp ratur of, .10 to 15 .C- s, m ntain d. T

. s olution of the diazoarnino compound is made in ethyl alcohol and the receiver treated therewith either rimmer n o by sp a i ie- A rec d n olution {o us i h th t eated pap s the madeupby d sso in =01.. ram mo e i; hromotrop c acid and 3.0 grams of salt. a liter of water. Sufli-cent sodium ht he solution to i e it ed solution is then used r01; 'wottiilglih use.

whereupon the paper is passed through an apparatus of the type above described for the'formation of dyestuff images thereon.

The dyestufi images obtained are dark blue brilliant images on a yellow background. The background is highly resistant to color changes.

Similar results were obtained when utilizing in lieu of the chromotropic acid coupler, the following couplers:

p-Suliophenylmethyl pyrazolone H @019 E eny 1 acid .Chloro 1-]: acid l =naphthol-4.8disulionic acid Ace H a i Beta naphthol N h olR Ethylatfid beta naphthol and a mixture of chromotropic acid and diacetoacetyl ethylene amin Example II 2.4' grams of Naphthol AS are mixed with 1.28 grams of sodium hydroxide (in the form of a concentrated solution) and cc. of boiling water are poured over the mixture to give a color suspension. After cooling to room temperature,

2 grams of a 40% solution of formaldehyde are added and the mixture diluted to a volume of cc.

Recording paper is treated by immersion in the above composition. The paper is then coated W th a p is lfi made by mixi the dry dia a compound of Example I with sufiicient diethanolamine to give the desired consistency.

This paper is then passed through a slightly alkaline solution of salt and water and. subjected to the action of an electrolytic current in the apparatus described above. There are formed on the paper, dyestufi images which are dark blue to purple in color on a. yellow backround. The records show a high background stability to light.

It will be appreciated that in this example both the diazoamino compound and the coupler are water-insoluble, but despite this fact, very satisfactory records are nevertheless obtained.

Example III .5 gram mole of sodium naphthionate is dissolved in approximately 750 cc. of water to which sufiicient sodium hydroxide is added to make the solution alkaline to brilliant yellow test paper.

.5. gram mole of sodium nitrite is then added and the solution is run under rapid agitation at a temperature of 5 to 10 G. into a solution of 141) .cc. of 38% hydrochloric acid and 750 cc. of water and ice. Diazotization is complete almost as soon as the solution is added and the diazonium compound, which is quite insoluble, precipitates out as a thick, creamy slurry. Stirring is continued for one hour to obtain the product in a form in which it is more easily ,filtered, Filter cake obtained upon filtration is reslur-ried in approximately 500 cc. of water until a smooth paste is obtained. This paste is added slowly at 10 to 15 C. over a. two-hour period with rapid; agitation to a solution of .125 cc. of diethanolamine in 250 cc. of water while mainmining, a em eratute f. 0 to 15 c. in an ice bath to nimize decomp sition- The reaction is complete when all the diazon-ium compound has been added. The resulting solution is. amber in colorand may stain diluted to 1 liter.

'and salt is used to impregnate papera 13 paper with a reddish tint. It must be alkaline when tested with brilliant yellow test solution.

2 grams of sodium hydrosulfite are added and the solution stirred for one hour at room temperature to clear away the red-staining impurities. 2 grams of activated charcoal are incorporated and the temperature raised to 50 to 55 C. for hour for the purpose of further clarifying the solution and to remove basic impurities. The solution is then filtered and the volume is adjusted to 1000 cc.

.A recording solution is then prepared by dissolving .03 mole per liter of the monosodium salt of chromotropic acid in 500 to 700 cc. of water. 8 grams of sodium carbonate are then added to render the solution alkaline to test with brilliant yellow test solution. .06 mole of the abovedescribed diazoamino compound, 30 grams of salt, and .5 gram of a sulfonated benzene which has been alkylated with a chlor paraflin and which is sold under the trade name Nacconol NR are then added and when solution is complete, the same is filtered and diluted to 1000 cc. The final solution is adjusted to a pH of 10 to 10.2 by the addition of approximately cc. of 2 N. sodium hydroxide solution. Dark blue to purple records on a white background are obtained when paper impregnated with this solution is subjected to the action of an electrolytic current.

Example IV Example In and grams of salt are then added and the solution diluted to 1 liter.

Papertreatedwith this solution and subjected to an electrolytic current in the apparatus previously described will give records of the type referred to in Example III.

Example V .03ngram mole of ethylated beta ethoxy-LG- Cleves acid is dissolved in about 300 cc. of water with the addition of suflicient concentrated sodium hydroxide solution to give a pH of approximately 10.

.03 gram mole of the diazoamino compound of Example III and 30 grams of salt are added and the solution Sufficient sodium hydroxide is added to give a pH of 10.2. The results-of using a paper impregnated with this solution approximate those of Example 111.

Example VI 4'-diethanolamino-4-amino-azobenzene is converted into a stable diazoamino compound by means of diethanolamine while operating in the manner outlined in the preceding example. A solution of this compound with chromotropic acid Dark recordings with a stable background are thus obtained.

Example VII The procedurein this example is the same as in Example I excepting that the diazonium compound which is stabilized is tetrazotize'd benzidine.

ill)

Example VIII The procedure in this example is the same as in Example I excepting that the diazonium com-- pound which is stabilized is tetrazotized dianisidine.

Example IX The procedure in this example is the same as in Example III excepting that there is used in lieu of the naphthionic acid diazotized alpha naphthylamine-4.8-disulfonic acid.

Example X One mol of dianisidine is tetrazotized and stabilized by reaction with 2.62 mols oi sarcosine while following the procedure outlined in Exampie I. The resulting diazoamino compound is utilized in connection with the coupler composition of Example II to produce electrolytic azo dyestuif images.

Example XI Anthranilic acid is diazotized and stabilized with a 5% excess of diethanolamine. The resulting compound is used in lieu of the diazoamino compound of Example III.

Example XII 1 mol of naphthionic acid is diazotized and stabilized with 2.62 mols of 2.5-dihydroxy-dicyclohexylamino-3-carboxylic acid while following the procedure disclosed in Example III. The resulting diazoamino compound is then incorporated in the solution of Example III in lieu of the diazoamino compound thereof.

Example XIII 1 mol of diazotized naphthionic acid is stabilized by means of 2.62 mols of p-hydroxycyclohexenyl glycine while utilizing the procedure described in Example I. The resulting diazoamino compound is used to substitute the diazoamino compound of Example III. The procedure is otherwise the same as in Example III.

Example XIV 1 mol of diazotized naphthionic acid is stabilized by means of 2.62 mols of gamma-hydroxy piper-idine while following the procedure of Example III. The resulting diazoamino compound is used to replace the diazoamino compound of Example III. Otherwise the procedure is as in Example III.

Example XV Example XVI The procedure is the same as in Example III except that the diazotized naphthionic acid is stabilized with cyclohexylamine.

Ea'ample XVII The procedure is the same as in Example III except that the diazotized naphthionic acid is stabilized with 4-sulfo-aminobenzoic acid.

It is to be understood that various modifications of my invention will be apparent to persons skilled in the art and I therefore do not 15 intend to be limited in the patent granted except as required by the appended claims.

I claim:

1, The process of producing colored images on a relatively stable background on only one side of a travelling fibrous carrier by the electrolytic facsimile recording method which comprises impregnating the carrier with an aqueous a1- kaline azo dye forming composition comprising as its essential ingredients a diazoamino compound stable to light and air oxidation in an alkaline medium and splitting under the influence of the electrolytic recording current to yield diazonium ions, said compound being selected from the class consisting of those of the following formulae R1 A N=NN\ R2 and wherein R1 andv R3 are selected from the class consisting of hydrogen, aliphatic, araliphatic, cycloaliphatic and aromatic radicals, R2 and R4 are selected from the class consisting of aliphatic, aralipha-tic, cycloaliphatic and aromatic radicals, A and A are aromatic radicals, Z represents the atoms necessary to complete a nitrogenous heterocyclic ring system, and a: is selected from the class consisting of 1 and 2, a water soluble inorganic salt as the electrolyte in an amount sufiicient to facilitate the passage of the electrolytic recording current, and a sufficient quantity of a coupling component to react with said diazonium ions when formed to produce an azo dye, and subjecting the so treated carrier to the action of an electrolytic recording current.

2-. The process as defined in claim 1 wherein the diazoamino compound is that from diazotized naphthionic acid and cyclohexylamine and the coupling component is chromotropic acid.

3. The processas defined in claim 1 wherein the diazoarnino compound is that from diazotized naphthionic acid and 4-su1fo-2 aminobenzoic acid, and wherein the coupling component is chromotropic acid.

4. The process as defined in claim 1 wherein the diazoamino compound is that from diazotized.

116 naphthionic acid and mornholine and wherein the. coupling component is chromotropic acid...

5. A process as defined in claim 1 wherein the-diazoamino compound and the coupling component are Water soluble.

6. The process as defined in claim 1 wherein the diazoamino compound and the coupling. component are water insoluble. 7. The process as defined in claim 1 wherein the diazoamino compound is prepared from 1 mol of a diazonium compound and from 1.05 to 2,62 mols of an organic amine.

8. The process as defined in claim 1 wherein the composition contains a bufiering agent.

9. The processas defined in claim 1 wherein the composition contains sodium carbonate.

10; The process as defined in claim 1 wherein the. diazoamino compound is prepared by interaction of one mole. of a diazonium compound with an excess of an organic amine overthat necessaryto react with said diazonium compound.

11. The process of producing colored images with a relatively stablebackground on only one side of a traveling fibrous carrier :by the electrolytic facsimile recording method, which com.- prises impregnating the carrier with an aqueous alkaline azo dye forming composition comprising as its essential components a diazoamino. compound stable to light and air. oxidation in an alkaline medium and splitting under the influence of the electrolytic recording current to yield diazonium ions, said compound having the following formula wherein A and R1 are aromatic radicals and. x is a positive Whole number not greater. than 2,. a water soluble inorganic salt as the electrolyte in an amount sufiicient to facilitate the passage of an electrolytic recording current, and a suificient quantity of a'coupling component to react with said diazonium ions when formed to produce an wherein Z represents the atoms necessary to complete a heterocyclic nitrogenous ring system, A is an aromatic radical, and a: is a positive whole number notgreater than 2, a water soluble inorganic salt as the electrolyte in an amount sufiicient to facilitate the passage of an electrolytic recording current, and a sufiicient quantity of. a coupling component to react with said diazonium ions when formed to produce. an azo dye, and subjecting the so treated carrier to the action of an electrolytic recording current.

HAROLD G. 'GREIG.

(References on following page) 17 18 REFERENCES CITED Number Name Date The following references are of record in the 2232406 schmelzer 1941 me of this patent: 2,306,471 Solomon Dec. 29, 1942 2,354,088 Reichel July 8, 1944 UNITED STATES PATENTS 5 2,419,296 Solomon Apr. 22, 1947 N m r Nam D t OTHER. REFERENCES 1 22 235 et a1 g? The Aromatic Diazo-Compounds and Their 1982631 Markus}; 1934 Technical Applications by K. H. Saunders, Du 26 81 C0. Pp. 2,058,419 Dahlen et a1. Oct. 25, 1936 2,232,405 Schmelzer Feb. 18, 1941