US2677651A

US2677651A - Sheet for electrical inscription

Info

Publication number: US2677651A
Application number: US189282A
Authority: US
Inventors: Homer J Dana; Raymond L Albrook
Original assignee: STATE COLLEGE OF WASHINGTON
Current assignee: STATE COLLEGE OF WASHINGTON
Priority date: 1950-10-09
Filing date: 1950-10-09
Publication date: 1954-05-04
Anticipated expiration: 1971-05-04

Description

Patented May 4, 1954 2,677,651 SHEET FOR ELECTRICAL INSCRIPTI-ON Homer J. Dana. and Raymond L. Albrook, Pullman, Wash., assignors to State College of Washington, Pullman, Wash.

No Drawing. Application October 9, 1950, Serial No. 189,282

11 Claims. 1

Th present invention relates to inscription of information upon sheets by electric current. In particular the invention relates to facsimile sheets upon which inscription is made by the receivin and recording unit of a facsimile transmission system. In the field of facsimile transmission in particular, the requirements to be met in the inscription of a received message are quite varied and severe. It is necessary that the affected parts of the record sheet show adequate color contrast, when compared with the unaffected parts, for legibility. Preferably the contrast should be suffioient to permit use of the sheet for retransmission of the message thereon.

There are several different kinds of sheets in present day use for facsimile reception. To the best of our knowledge, however, these sheets do not meet the several requirements in a satisfactory manner. It is desirable that the record receiving sheets be of such a nature that they may be stored dry and remain relatively unaffected by humidity changes. The sheets should be usable in the dry state and should not require processing beyond actual reception of the electrical impulses. It is highly desirable to avoid any sparking in the electrical inscription as this limits the use of the sheets to exclude any particular area where there may be xplosive fumes such as exist in an aircraft when there is a gasoline leak. The record sheet must be capable of withstanding wide variations in altitude and must be usable in a temperature range from about 60 degrees F. to 130 degrees F. The sheet must be non-toxic and should be stable for a period of at least three or four months.

It is th purpose of the present invention to provide a record sheet which is stable in the temperature range and for the period set forth above, capable of being inscribed by passing electric current through. it, wherein the sheet embodies a compound which reacts chemically with another material toproduce change in color, and, an electrically conductive impregnation which is changed by the passage of current, to produce, at the point of current passage, the other material necessary to effect a color change in the sheet, the color producing compound and the electrically conductive impregnating material being of such a nature that prior to the activation by the electriocurrent, they can both be intimately mixed through the body of the sheet and remain stable under the conditions set forth in the preceding paragraph.

More particularly the present invention consists of combining, in a reception sheet for electrical inscription, a solution of a substantially colorless basic salt of nitric or nitrous acid in a solvent which will not freeze within the temperature limitations hereinbefore set forth and which evaporates very slowly; and a Beta naphthyl amine compound which will react chemically with the electrolytic decomposition products of the aforesaid salt to form a visible color contrast to the sheet. The Beta naphthyl amine compounds, which react chemically in the aforcgoing fashion, are best described as electro-chromotropic compounds to distinguish them from compounds which may be eleotro-sensitive but do not produce a visible inscription in the sheet.

It is evident that the sheet, in order to be useful in the present electrical transcription of messages must respond quickly to the passage of electrical imp-ulses through it. The customary methods of electrical inscription in facsimile reproduction pass the current through the sheet at spaced spots to create dots which when completed show the inscription. These dots are currently formed at a rate as high as one dot at millisecond. The time is short in which to effect the necessary electrolytic decomposition and the reaction of the decomposition products with the electro-chromotropic compound.

The electro-chromotropic compounds are not necessarily conductive, but, if sparking is to be prevented the sheet must have relatively high conductivity. Accordingly we prefer to employ a relatively thin and smooth sheet so that the stylus or other contacting element may ride closely upon the sheet without bouncing. Also the very thinness of the sheet itself, reduces the resistance to current flow and lessens the pos 'sibility of sparking. Various sheets have been found to he sufiiciently smooth and thin. Linen cloth used for making tracing cloth has been used satisfactorily. A very fine weave cotton cloth has also been used satisfactorily. Various papers may also be used. The color of the sheet is not too critical although white is preferable because a white back ground fits in so Well with the various photographic reproduction processes and gives maximum contrast to the colors produced by passing electrical current through the sheet.

The manner of making the sheet conductive to electrical current is rather critical. The conductivity should not change appreciably over the range of temperature (-60 degrees F. to 136 degrees l t). Furthermore the conductivity should remain substantially constant over a long period of time. It is essential that the conductivity be uniform throughout the used area. The electrolyte used must be impregnated into the sheet with a particular solvent in order to avoid freezing or absorption over the temperature range and for the desired life period. Satisfactory solvents are those with low vapor pressures and low freezing points such as polyhydroxy alcohols, derivatives of polyhydroxy alcohols, and polymerized polyhydroxy alcohols. These solvents should remain liquid over the temperature range limitations. Specific examplesof ,the above s01- vents are the following: Ethylene glycol (CHzOI-I) 2 glycerin CI-IOH CH2OH)2, propylene glycol' CI-IsCI-IOH CHzOI-l', diethleneglycol HOCHzCI-IzOCI-IzCI-IzOH and triethylene glycol HOC2I-I4OC2H4OC2H4OH.

Higher molecular weight polyhydroxy alcohols,

"theiresters and polymerized products are not suitable solvents. Such solvents do no permit either sufficient solubility 'or ionization of the electrolytes for the necessary conductivity. For example, the following substances are unsatisfactory as solvents :-mannitol, sorbitol, carbutoxytetraglycol, dimethoxytetraglyool, ethylene glycol monomethyl ethenpolyglycol P-400 and poly glycol -P-"750.

The solvent just described contains, in solu- .tion, and at least partially ionized, a stable ni- :trate.salt characterized by absence of, or very low color. When the sheets are impregnated with the solvent and salt they remain conductive even whendry'in the usual sense. In general the steps .of making the sheets conductive are carried out by passing them through a bath of equal parts of water and glycerine in which a stable nitrate such asammonium nitrate is dissolved. Excess liquid is removed by passing the sheet between rolls under light tension. The sheet is dried by passing it over heated rolls to remove the excess water. The paper is dry to the touch and can bestored or used. The electrical resistance is of :the order of 30 ohms to 100 ohms.

The nitrate salts which are suitable for this purpose are those which are colorless or of very low color. They are retained in solution by the polyhydroxy alcohol solvents throughout the temperature range of 60 degrees F. to 130 F. They do not of themselves change color under exposure to light. The preferred salt is ammonium nitrate, or sodium nitrite. Examples of salts that are satisfactory are the nitrates and nitrites of sodium, potassium and zinc, and nitrate. Nitrate salts of copper and chromium are not satisfactory because they are highly colored. Strontium and barium nitrates can be dis solved in the water and then the glycerine or other softener may be added. Both of the above nitrates give good results.

The essential characteristics of the salts are thatthey are soluble in the solvent. readily conductive, of very low color, and that they decompose readily when current is passed through the sheet.

The sheets are impregnated with a compound which becomes reactive with the electrolyte in solution'in the sheet, only upon the passage of current, to produce a visible color change. The compounds having this characteristic we term electro-chromotropic to distinguish them from compounds which are electro-sensitive. under like conditions, without visible change in color. These compounds do not react with the nitrate salts in the sheet in the absence of the passage of electric current. The compounds are of the Beta naphthyl amine type. B-naphthyl derivatives of n-alkyl diamines up to and including hexamethylene diamine have been found to mark. Those above the hexamethylene diamine may be disregarded as :the marking value is not sufficient for practical use. We 'flnd that all'B-naphthyl amine derivatives not capable of forming quinoid structures by oxidation may be disregarded. For example, tribetanaphthylmelamine is not satisfactory. The'following particular compounds are illustrativeofoperative B-naphthyl amine derivatives N,N di-B-naphthyl-p-phenylene diamine iPhenyleB-naphthyl amine Di-Z-naphthyl amine N,N di-B-naphthyl benzidine N,N di-B-naphthyl ethylene diamine N,N di-B-naphthylpropylene diamine This class of compounds reacts With electrolytic decomposition products of nitrates "or nitrites to form oxidized, nitro or nitros'o compounds.

Probably all three types of reaction take place during electro-chemical reactions at the stylus or wheel contact. Such reaction products are colored ranging from light gray to black and from light yellow or brown to dark brown depending upon the amount of current flowing-through'the paper or cloth. Introduction of a small amount of metal from the stylus:or Wheel, though not essential for color change, will catalize the reaction and will affect .the amount of andintensity of color produced, an iron stylus or wheel will produce brown colors, one of copper will produce gray or black and aluminum produces a greenish color.

B-naphthyl amine compounds in water suspension can be oxidized, nitrated or sulfonated by adding appropriate reagents. Such compounds vary from green to black depending upon concentration of oxidizing, nitrating or 'sulfonating agent. This proves that the metal of the stylus is not necessary for color formation. The color produced from such compounds asphenyb B-naphthyl amine, di-2-naphthyl amine, N,N di- IB-naphthyl ethylene diamine and 'N,N di-B- naphthyl propylene diamine is light yellow to 'light brown which results from formation of nitro-' and nitroso-reaction products at the stylus. The dark brown to black color from such compounds as N,N di-B-naphthyl-p-phenylene diamine and N ,N di-B-naphthyl benzidene results from quinoid structure formation by oxidation from reaction products at the stylus.

The above named'class of compounds are not water soluble. Solubility will vary with solvents used. .Ethyl alcohol, acetone, pyridine, picoline, xylene, morpholine, thio-diglycol and other solvents "may be used. Pyridine and the picolines have been found to be'best for making solutions of the B-naphthyl amines as the solubility is greater in these two specified solvents than in some of the others named.

Solutions of one-half of onepercent /2 of 1%) to maximum of the solubility of the B-naphthyl amine compound in the solvent have been used to impregnate paper or cloth. Excess solution is then removed by passing the treated paper or cloth between compression rubber rolls. By changing the pressure'of the rolls the amount of solution left in the paper or cloth can be varied. After the solvent is evaporated the paper or clothis treated with a solutionof-electrolyte, solvent and water to make the paper or cloth conductive. The B-naphthyl amines are insoluble in such solutions and therefore the compounds remain distributed on the fibres of the cloth or paper. Excess conductive solution is removed by passing the paper or cloth between compression rubber rolls. Quantity of the conductive solution (electrolyte, solvent and water) left in the paper may be varied by the pressure of the rolls. After drying to remove excess Water left in the paper or cloth after passing between the compression rolls the paper or cloth is ready for use.

To improve adhesion of the B-naphthyl amine compounds to paper and cloth fibres such fibre may, though it is not absolutely essential, be pretreated by saturating with a solution of Lead acetate (Pb(Ac)2), zinc acetate (Zn(Ac)z), Aluminum acetate (Al(Ac): or other mordants. Zinc acetate is preferabl: due to higher solubility than Aluminum acetate and its relatively low toxicity. Sulfonated alcohols or fatty acids may be used in small amounts to lower surface tension and obtain better adhesion and distribution of B-naphthyl amine compounds over the surface of the fibres.

Another method for applying the B-naphthyl amines to the fibre of paper or cloth is to dissolve the electro-chromotropic compound in pyridine, morpholine, thio-diglycol or other solvent which is miscible with water, saturate the paper or cloth with the solution and, Without driving 01f or evaporating the solvent, passing the paper through a water bath. Excess water will precipitate the B-naphthyl amine from the solvent upon the fibres of the paper or cloth.

Example A.Four and onehalf (4 grams of bLN di-B-naphthyl-p-phenylene diamine are dissolved in 66 ml. pyridine. Paper or cloth previously described is immersed in the solution until thoroughly saturated then passed between rolls which have very light tension. The solvent is permitted to evaporate at room temperature or may be passed over a sheet of aluminum heated by a hot plate. the paper or cloth is passed through a bath of 11 grams of ammonium nitrate, 17 grams of glyocrine and 17 grams of water. Excess liquid is removed by very light tension on the rolls. Ex-

cess water is removed by passing the paper over heated rolls. The paper is ready for inscription or may be stored for future use.

Example B.-Paper or cloth may be pretreated by soaking in a water solution of 5% zinc acetate and dried. After drying the paper is then treated in the same steps as used in Example A.

Example C.-Nine (-9) grams of phenyl-B- naphthyl amine are dissolved in 66 ml. pyridine. Unpretreated or pretreated paper is saturated with this solution and excess solution removed by rolls. After the solvent has been evaporated the paper is saturated with a solution of 9 grams of ammonium nitrate, 14 grams of glycerine and 17%; ml. of water. After removing excess water by drying the paper is ready for inscription.

Example D.Picoline is substituted for pyridine in Example A.

Example E.-Glycol or diethylene glycol is substituted for glycerine in Example A.

The beta naphthyl amine compounds are insoluble in Water and quite stable. They can be incorporated into the sheet in different ways. They may be dissolved in pyridine, morpholine, or thio-diglycol and applied to the sheet. The sheet is then immediately passed through water.

After the solvent is evaporated 6 l The beta naphthyl amine compounds are precipitated on the sheet fibers and the solvents, being themselves soluble in water, are drained out.

A. solution of the Beta naphthyl amine group in pyridine can be added to the paper pulp beater to precipitate the group on the pulp fibers. When the paper is formed the beta naphthyl precipitate will be in the matrix of the paper.

Sheets treated in accordance with the foregoing disclosure may be inscribed by the usual facsimil equipment with voltages as low as volts. Higher voltages up to 280 volts have been used without sparking. Either alternating or direct current may be used but an anodic stylus will effect the greatest density of color. The color change is most pronounced at the anode surface of the sheet. When alternating current is used alternate dots on the stylus side of the sheet will be missing or less visible because of current reversal. Direct current is therefore preferable. I The preferred electro-chromotropic compound is N,N di-B-naphthyl-p-phenylene. Our experiments have shown it to give the greatest color contrast between the inscription and the surrounding sheet surface. If a sheet is impregnated with this compound and the electrolyte ammonium nitrate, the sheet is slightly gray. The contrast between the inscription and the surrounding area is great enough for blue-printing or retransmission. The sheets are stable.

It is believed that the nature and advantages of our invention will be apparent from the foregoing description. i-Iaving thus described our invention, we claim:

1. A substantially dry sheet adapted for visible inscription by passage of electric current therethrough comprising a non-conducting base ma-- terial impregnated with a solution of substantially colorless nitrate in a polyhydroxy alcohol and with a water insoluble organic compound having a Beta naphthyl amine radical and capable of forming quinoid structures by oxidation, said organic compound being capable of being oxidized in situ upon decomposition of said nitrate by passage of current through the sheet.

2. A substantially dry sheet adapted for visible inscription by passage of electric current therethrough comprising a non-conducting base material impregnated with a water insoluble organic compound having a Beta naphthyl amine radical and. capable of forming quinoid structures by oxidation and with a solution of a substantially colorless basic, an inorganic salt from the group consisting of nitrates and nitrites in a polyhydroxy alcohol of the group consisting of ethylene glycol, glycerine, propolene glycol, diethylene glycol and triethylene glycol, said organic compound being capable of being oxidized in situ upon decomposition of said inorganic salt by passage of current through the sheet.

3. A substantially dry sheet adapted for visible inscription by passage of electric current therethrough comprising a non-conducting base material impregnated with a water insoluble organic compound having a Beta naphthyl amine radical and capable of forming quinoid structures by oxidation and with a solution of ammonium nitrate in a polyhydroxy alcohol of the group consisting of ethylene glycol, glycerine, propolene glycol, diethylene glycol and triethylene glycol, said organic compound being capable of being oxidized in situ upon decomposition of said nitrate by passage of current through the sheet.

4. A substantially dry sheet adapted for visible inscription why passage of electric current 'LthEI'G- through "comprising a non-conducting 'sheet of fibrous material impregnated with a water in- :solube'organic compound having a Beta naphthyl amine "radical and capable of forming quinoid structures by oxidaticn-and with asolu- :tion of a substantially colorless basic, an inorganic salt from thegroup-consisting'of nitrates and ,nitrites in .a polyhydroxy alcohol of the group consisting of ethylene glycol, glycerine,

;propolene glycol, 'diethylene glycol "and triethyl- :ene glycol, said:organic'compound being-capable of being oxidized in situaupon decomposition of saidinorganic :salt by;passage ,of currentithrough the sheet.

5. A substantially dry sheetadapted for visible inscriptionby passage of-electric current therethrough comprising anon-conducting paper impregnated with a Waterinsoluble organic compound having a Betatnaphthyl amine radical and capable of 'formingquinoid structures by oxidation and Wl'ChTasolution of ammonium nitrate in aypolyhydroxy alcohol oithe group consisting of ethylene glycol, -.glycerine, propolene glycol, diethylene glycol and triethylene glycol, said organic compoundbeing capable of being oxidized in'situ upon decomposition of said nitrate by passage of current through the sheet.

6..A substantially dry sheet adapted for visible inscription by passage'of electriccurrent there-- through comprising :a non-conducting sheet of fibrous material, having-a water insoluble organic compound having a Beta naphthyl amine radical and capable of forming quinoid structures by oxidationdistributedthereon, said sheet containing a substantially-colorless solution of: an inorganic salt from .the group consisting of nitrates and nitrites in glycerine, said organiccompound being capable of being oxidized. insitu upon decomposition of saidinorganic salt by passage of current throughthe sheet.

7. A substantiallydry sheet adapted for visible inscription by passage of electric current there- 'through comprising a non-conducting sheet of fibrous material, having N,N di-beta-naphthylp-phenylene .diamine distributed thereon, said sheet containing a substantially colorless solutionof an inorganic salt of nitrogen. in glycerine, said diamine being capable of being oxidized in eitu upon decomposition of said inorganic salt bypassageof current through the sheet.

8. A substantially dry sheetadapted for visible inscription by passageof electric current there- .through comprising a non-conducting sheet of fibrous niaterial,.having N,N -di-beta-naphthylpephenylene diamine distributed thereon, said sheet containing a solution of ammonium nitrate .in glycerine, said diamine being-capable of being oxidized in situ upondec-omposition of said nitrate by passage-of current through the sheet.

-9. A substantiallydrysheet adapted for visible inscription by passage of electric currenttherethrough comprising a non-conducting sheet 'of fibrous material, having N,N di-beta-naphthyl-rp-phenylenevdiamine uniformly distributed therein,-said sheet containing asolution of ammonium nitrate in glycerine, said diamine being capable of being'oxidized in situ upon decomposition of said nitrate by passage of current through the sheet.

10. A substantially dry sheet adapted for visible inscription by passage of electric current .tlierethroughcomprising a non-conducting sheet of fibrous-materiaLhaving a Water. insoluble organic compound having a Beta naphthyl amine radical and capableotforming quinoid structures .by oxidation distributed thereon, said sheet conpound having aBetanaphthyl amineradical and capable of forming .quinoid structures by oxidation distributed thereon, said sheet containing a substantially colorless solution of an in organic salt from the group consisting of nitrates and-nitrites .in apolyhydroxy alcohol-of the group consisting of ethylene glycol, glycerine, propylene glycol, vdiethylene glycol and triethylene glycol; said organic compound being capable of being oxidizedin situ upon decomposition of said inorganic salt by. passage of current through the sheet.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 168,466 Edison Oct. 5, 1875 670,510 Friese-Greene Mar. 26, 1901 2,229,091 Kline Jan. 21, 1941 2,281,013 Talmey Apr. 23, 1942 2,346,670 Engler et al Apr. 18, 1944 2,459,521 Greig Jan. 18, 1949 2,513,238 Greig June 27, 1950 OTHER REFERENCES Electrolytic Oxidation and Reduction, Glassstone and Hickling, 1936, pages 318-328.

Electra-Organic Chemistry, 1926, pages 11 121, by Brockman.

I-Iackhs Chemical Dictionary, 3d edition, 1944, page 259.

Websters New. Int. Dictionar', 2nd edition, 1940. page 704.

Claims

1. A SUBSTANTIALLY DRY SHEET ADAPTED FOR VISIBLE INSCRIPTION BY PASSAGE OF ELECTRIC CURRENT THERETHROUGH COMPRISING A NON-CONDUCTING BASE MATERIAL IMPREGNATED WITH A SOLUTION OF A SUBSTANTIALLY COLORLESS NITRATE IN A POLYHYDROXY ALCOHOL AND WITH A WATER INSOLUBLE ORGANIC COMPOUND HAVING A BETA NAPHTHYL AMINE RADICAL AND CAPABLE OF FORMING QUINOID STRUCTURES BY OXIATION, SAID ORGANIC COMPOUND BEING CAPABLE OF BEING OXIDIZED IN SITU UPON DECOMPOSITION OF SAID NITRATE BY PASSAGE OF CURRENT THROUGH THE SHEET.