US3491364A - Method and apparatus for information storage - Google Patents

Description

Jan. 20, 1970 W. S. M EWAN ET AL METHOD AND APPARATUS FOR INFORMATION STORAGE Filed Jan. 31, 1968 INVENTORS. WILLIAM S. MCEWAN PETER R. HAMMOND BY v ROY MILLER ATTORNEYS.

United States Patent Ofilce 3,491,364 Patented Jan. 20, 1970 3,491,364 METHOD AND APPARATUS FOR INFORMATION STORAGE William S. McEwan and Peter R. Hammond, China Lake,

Califi, assignors to the United States of America asrepresented by the Secretary of the Navy Filed Jan. 31, 1968, Ser. No. 702,092 Int. Cl. G01d 9/12 U.S. Cl. 34621 8 Claims ABSTRACT OF THE DISCLOSURE A system for information storage which comprises a film having a recording surface coated or impregnated with a heat sensitive mixture consisting of a pair of compounds, one an electron acceptor and the other an electron donor, which may be dispersed in an immiscible matrix, and a hot stylus in contact therewith and movable there to. As the stylus is moved over the treated film surface a color appears due to the action of heat on the mixture leaving a record on the film of the movement of the stylus.

BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for information storage by utilizing a mixture composed of two mutual compounds which becomes colored when heated and fades on cooling.

The prior art discloses color forming chemical reaction recorders using paper treated with phenolphthalein and a stylus material composed of sodium lead or sodium amalgam which reacts with the chemical in the paper to produce a color change. Memories have also been stored on special photographic plates which can be located by beam deflectors. Transparent liquid or jelly-like compositions which when subjected to electric impulses of a certain magnitude provide visual displays under either visible or ultraviolet light. The chemical recorders are sensitive and depend upon the quality and manner of handling the reactants in order to produce color recordings. The photographic and various electronic devices available are expensive and generally require special training to operate. The present invention provides a simple and practical memory storage system by use of a mixture of pairs of preselected compounds which is heat sensitive, changing color according to temperature with no chemical reaction occurring between the pairs of compounds.

SUMMARY In accordance with the present invention paper film was thinly coated on one surface with a heat sensitive mixture composed of preselected acceptor-donor compounds in compatible matrixes and a hot stylus was moved over the coated surface. As the stylus moved along the heat caused the coating to change color leaving a record on the film of the movement of the stylus.

The colors of the acceptor-donor systems used on at least one surface of the film herein vanish on cooling. The early work of Charles K. Tinkler who described the disappearance of color on freezing some mixtures of nitrocompounds with amines in his paper entitled A Series of Mixtures of Nitro-Compounds and Amines Which Are Colored in the Liquid State Only, Chem. Soc. (London) J. 1913, pp. 2171-79, provided the first examples of the color systems developed and used herein. The color system developed by the present inventors considerably extends the class of materials and provides a rationale for selecting further systems. For each acceptordonor chemical examined, the disappearance in one system was often accompanied by disappearance in others. The basis of the color change, namely, a donor to acceptor change-transfer transition even when no bond is formed between these molecules, is not new to the study of molecular complexes. The following table is a list of mixtures of the pairs of compounds which formed stable complexes giving the colors of the melts and of the solids.

TABLE I.COLOR CHANGES OF SOME ACGEPTOR-DONOR MIXTURES Solution or Mlxture melt color Color of solid Diphenylarnine-palinitrobenzene Red White.

Diphenylamme-p-chloronitroben- Orange Do.

zene.

Tetranitromethane-hexamethyl- Red-orange Do.

benzene.

Tetranitrometheme-naphthalene Yellow-orange. Do.

Tr n tromesitylene-dimethylaniline do D0.

Trimtromesitylene-anthracene Yellow Do.

Hexanltrodiphenyl-pyrene Red Pale cream.

Hexamtrodiphenyl-anthracene Magenta White.

p-Dinltrobenzene-triphenylamine l Red Do.

1,3,5-tr1mtrobenzene-triphenyl- Red Very pale pink.

amine.

p-Chloranil-triphenylamine Blue-green Pale cream.

Tetraeyanoethylene-tetra-i-propyl- V'olet White.

benzene.

Tetraeyanoethylene-p-di-i-butyl- Red-orange. Do.

benzene.

p-Dinitrobenzene-tetramethyl-2- Orange Do.

tetrazene.

p-Nitroanisole-tetrakis(dirnethyl- Red D0.

amino) ethylene.

Nitrobenzenetetrakis(dimethyl- Magenta D0.

amino) ethylene.

p-Chloronitrobenzene-tetrakis Violet D o.

(dimethylamino) ethylene.

Aeridinetetrakis(dimethylamino) Red Do.

ethylene.

In all cases the changes shown in the above table were distinct. All colors were produced immediately on mixing and were stable until solidified. The change from a deep violet liquid of the mixture of tetracyanoethylene and tetra-i-propylbenzene to a clean, white crystalline solid was at once distinct. Microscopic slides of the diphenylamine and p-chloronitrobenzene, trinitromesitylene and anthracene, hexanitrodiphenyl and anthracene, triphenyl amine and p-dinitrobenzene, and tetracyanoethylene and tetra-i-propylbenzene mixtures, although colored in the hot liquid state, were Colorless by both transmitted and reflected light. The colors of the solids were the colors of the original components, although a very faint pink could be obtained on rapid freezing of the deep red trinitrobenzene and triphenylamine liquid mixtures. Heating of any of the solids in the above table immediately produced the original color and the cycle without doubt could be repeated innumerable times. The condition essential for the loss of color is seen to be the separation of acceptor and donor molecules, generally into two phases in the solid, a behavior typical of systems showing simple eutectic diagrams. Diffraction patterns are clearly those of the pure materials in the mixtures and no additional lines are observed. The proportion of acceptor and donor molecules in contact, and hence capable of contributing to the absorption intensity, must be the relatively few at' crystal interfaces. Melting point diagrams and X-ray crystal studies confirm the lack of compound formation. It is the general object of this invention to provide an information storage device which is economical and practical and may be cycled an infinite number of times without wearing out. Another object is to provide a recording apparatus and method which is useful for the continuous recording of information over a wide temperature range with no chemical reaction occurring between the components. Other objects, features, and many of the attendant advantages of this invention will become readily appreciated by reference to the following description when considered in connection with the accompanying draw- 3 BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE INVENTION Referring now to FIGS. 1 and 2 there is shown a recording apparatus wherein a film is drawn from supply spool 11 over platen 12, r llers 13 to reroller 14. A stylus 15 adapted to be heated rests on the surface of film 10. Stylus 15 is carried by a recording arm 16 and is pivoted to shaft 17 at point 18. As shaft 17 moves over its predetermined range, stylus 15 moves across film 10 producing a record as indicated by 19. Stylus 15 consists of a metal and is heated by electrical means (not shown), or other suitable means, provided in shaft 17. Film 10 shown in FIG. 2 is coated on its recording surface 20 within a thin layer 21 of a mixture consisting of a preselected pair of acceptor-donor chemicals in a compatible matrix which in solution at certain temperatures is colored and which at the solidus temperature exhibits a loss of color.

A laser beam may replace the stylus since a aser acts by producing heat in a small area.

The coating was prepared by mixing together in about equal amounts the acceptor and donor compounds in a compatible solvent such as tetrahydrofuran, dichloromethane or similar solvents. The acceptor and donor compounds may also be mixed together without a solvent. At room temperature the mixtures stayed in solution and were colored when brushed onto sheets of white paper. When the solvent evaporated, the mixture solidified and the color vanished. Other materials such as plastics to which the mixture will adhere or into which the mixture can be absorbed may be used for the film, and other means of coating the material may be used such as by immersion into the mixture, by spraying, etc.

In operation, as heated stylus 15 moves along the recording surface 20 of film 10 a visible record 19 is formed on layer 21. This is due to the heat from the stylus melting the layer which in melt or solution is colored. Upon returning to the solidus temperature, the color disappeared. The apparatus of FIG. 1 has the advantage of recording information temporarily and then being resuable since return to the solid state erases the record.

A second embodiment of the invention is shown in FIGS. 3 and 4 wherein like numbers in the drawings indicate identical structures throughout the embodiments of the invention. The recording film 10a consists of uncoated, light-colored paper. The stylus has been modified, and now designated 15a consists of a housing 22 closed on one end and provided with a capillary tube 23 containing a mixture of the same preselected pairs of acceptor-donor chemicals as the coating 21 on film 10 in the embodiment shown and described in FIG. 1. In operation as stylus 15a moves over the surface of film 10a it deposits the mixture in melt form which is colored. As film 10a is moved along on reroller 14 the solvent evaporates and the color fades. Upon gentle warming of film 10a the color reappears making the information visible. The housing and capillary tube may be of any suitable material such as metal or some plastics. This embodiment provides a permanent memory storage apparatus which at solidus temperatures is invisible and on gentle warming becomes visible.

Obviously many modifications and variations of the present invention are possible n t g t of the above teachings.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. An apparatus for recording information on a dry film in the form of a colored melt which on solidification fades and reappears upon gentle warming comprising:

a dry light-colored film and a stylus in contact with and movable relative to said film; said stylus containing a mixture consisting essentially of a pair of acceptor-donor chemicals which are colored in the liquid state, in contact with said film and producing a record in color on the film of the movement of the stylus relative thereto;

said pair of acceptor-donor chemicals being selected from the group consisting of diphenylamine and p-dinitrobenzene; diphenylamine and p-chloranil; diphenylamine and chloronitrobenzenc; diphenylamine and p-chloronitrobenzene; tetranitromethane and hexamethylbenzene; tetranitromethane and naphthalene; trinitromesitylene and dimethylaniline; trinitromesitylene and anthracene; hexanitrodiphenyl and pyrene; hexanitrodiphenyl and anthracene; p-dinitrobenzene and triphenylamine; 1,3,5-trinitrobenzene and triphenylamine; p-chloranil and triphenylamine; tetracyanoethylene and tetra-i-propylbcnzene; tetracyanoethylene and p-dii-buty1benzene; p-dinitrobenzene and tetramethyl-2-tetrazene; p-nitroanisole and tetrakis(dimethylamino)ethylene; nitrobenzene and tetrakis(dirnethylamino)ethylene; p-chloronitrobenzene and tetrakis(dimethylamino)ethylene and acridine and tetrakis (dimethylamino)ethylene.

2. The apparatus of claim 1 wherein said stylus contains a mixture consisting of diphenylamine and p-dinitrobenzene.

3. The apparatus of claim 1 wherein said stylus contains a mixture, of diphenylamine and p-chloranil.

4. The apparatus of claim 1 wherein said stylus contains diphenylamine and p-chloronitrobenzene.

5. The apparatus of claim 1 wherein the stylus contains a mixture of p-dinitrobenzene and triphenylamine.

6. The apparatus of claim 1 wherein the stylus contains a mixture of tetracyanoethylene and tetra-i-propylbenzene.

7. The apparatus of claim 1 wherein the stylus contains a mixture of tetracyanoethylene and p-di-t-butylbenzene.

8. An apparatus for temporarily recording information in the form of a colored melt which at its solidus temperature vanishes comprising a film having at least one surface coated with a mixture consisting of a pair of donor-acceptor chemicals;

a heated stylus adjacent and movable relative to said coated surface of said film; said stylus being heated to the temperature at which said coating melts when adjacent to said surface and producing a record in color on said coated surface of the movement of the stylus relative thereto;

said pair of acceptor-donor chemicals being selected from the group consisting of diphenylamine and p-dinitrobenzene; diphenylamine and p-chloranil; diphenylamine and chloronitrobenzenc; diphenylamine and p-chloronitrobenzene; tetranitromethane and hexamethylbenzene; tetranitromethane and naphthalene; trinitromesitylene and dimethylaniline; trinitromesitylene and anthracene; hexanitrodiphenyl and pyrene; hexanitrodiphenyl and anthracene; p-dinitrobenzene and triphenylamine; 1,3,5-trinitr0benzene and triphenylamine; p-chloranil and triphenylamine; tetracyanoethylene and and tetra-i-propylbenzene; tetracyanoethylene and p-di-i-butylbenzene; p-dinitrobenzene and tetramethyl-Z-tetrazene; p-nitroanisole and tetrakis(dimethylamin0)ethylene; nitrobenzene and tetrakis(dimethylamino)ethylene; p-chlo- 5 6 ronitrobenzene and tet1-akis(dimethylamino)ethylene 1,844,199 2/ 1932 Bicknell et a1 346-76 X and acridine and tetrakis (dimethylamino)ethy1ene. 1,939,232 12/1933 Sheppard et a1 346-76 X 2,631,918 3/1953 Kozak 346135 X References Cited UNITED STATES PATENTS 1,351,071 8/1920 Silvermanet a1. 346135X 1,402,442 1/1922 Porter 10621 21;3 6 6, 3

5 JOSEPH W. HARTARY, Primary Examiner

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