US3905876A

US3905876A - Electrorecording sheet

Info

Publication number: US3905876A
Application number: US420601A
Authority: US
Inventors: Kimiaki Yoshino; Kinichi Adachi; Wataru Shimotsuma; Yoichi Sekine; Toshio Shimizu
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1972-11-30
Filing date: 1973-11-30
Publication date: 1975-09-16
Anticipated expiration: 1992-09-16
Also published as: NL165413C; DE2359271B2; GB1445757A; AU6299873A; FR2209330A5; DE2359271A1; NL7316317A; CA990953A; AU463673B2; NL165413B

Abstract

An electrorecording sheet comprises a heat sensitive color forming component which shows color formation or color change upon application of heat energy thereto, cuprous iodide imparting conductivity and a resistance lowering agent for lowering resistance of cuprous iodide by providing a free iodine component to cuprous iodide. When electric current flows across selected areas of the recording sheet, the color forming component in those areas forms color to mark the record.

Description

United States Patent Yoshino et al.

[4 1 Sept. 16, 1975 ELECTRORECORDING SHEET lnventors: Kimiaki Yoshino, Neyagawa; Kinichi Adachi, Takarazuka; Wataru Shimotsuma, l-lirakata; Yoichi Sekine, Katano; Toshio Shlmizu, Daito, all of Japan Assignee: Matsushita Electric Industrial Co.,

Ltd., Kodoma, Japan Filed: Nov. 30, 1973 Appl. No.: 420,601

Foreign Application Priority Data Nov. 30, 1972 Japan 47-120898 Mar. 20, 1973 Japan 43-32302 us. Cl. 204/2; 1' 17/361; 346/76 R; 346/135 Int. Cl.......' 841m 5/20 Field oi Search 346/74 CH, 74 E, 76 R,

, 346/135; 204/2, 18 PC; 340/173 CH; ll7/l.7, 36.7, 36.9

[56] References Cited UNITED STATES PATENTS 3,518,038 6/1970 3,642,475 2/1972 3,655,527 4/1972 3,789,425 1/1974 3,792,481 2/1974 Nagashima 346/135 Primary ExaminerT. M. Tufariello Attorney, Agent, or Firm-Stevens, Davis, Miller & Mosher 19 Claims, 8 Drawing Figures PATENTED SEP 1 BIQYS win 2 mg 2 FIG.3

000 a 3, 30 GB 0 94% I DO FIG.5

FIG.7

The present invention relates to an electrorecording sheetfor converting'electrical signals directly to yi's' 'ual images adapted to be used inan ii'iformation recording apparatus'suchas fa facsimile, a character printer, an analog recorderor the like? i i Prior art recording materials usable for the samepurpose as that of the present invention include asp'arking record paper,an'electrolytic recording paper or the As is well-known in the art, the sparking record paper consists of a black conductive layer of carbon and an overlying layer comprising a white semiconductive me} tallic. compound and bin der material, in whichrecofrd ing images are formed bypassing eurrent thereacrjoss to destroy portions of white layer and spatter them away to expose the conductive layer. I A

The recording sheet of thistype is cha i'ac terized'by a dry system, a high recording'speeilow cost and elimination of need of developingand fixingpr'ocesses, but has a disadvantage in that a considerable amount of smoke and odor are generated upon sparking. I

The electrolytic recording sheets are classified in two types, one in whieh metal ions of a recording electrode react with electrolyte impregnated in the recording paper and the other in the electrolyte is decomposed by current so'th'at the products therefrom form color. These types of recording sheets are advantageous in that theyhave high sensitivity and are inexpensive but have the disadvantages of electrode consumption and errosion, relatively short effective preservation period of images and those inherent to wet type rer i It is an object of the present invention to provide an electrorccor'ding sheet which overcomes the shortcomings of the prior art recording sheets, allows use in a lighted place, can providedrecordings of high gradient at high speed, hasstable image preservation propertiesv without discoloration or fading, is inexpensive and does not require head replacement or toner replacement.

The'electrorecording sheet of the present invention comprises a heat sensitive, color forming component which forms color or changes color upon application of heat energy thereto, cuprous iodide which imparts conductivity to the recording sheet and a support sheet bearing the above components. A record is marked by flowing current across a recording stylus electrode in contact with the recording sheet and a counterelectrode to cause color forming or color change of the heat sensitive color forming component in those selected areas adjacent to the recording stylus, through which areas current has been passed. t

The electrorecording sheet of thepr'esent invention uses transparent or light yellow cuprous iodide as a conductive material and the heat sensitive color forming component forms color or changes color by flowing electric current. Accordingly, neithera colored layer:

nor a masking layer is required, and substantially no bad odor, recording sludge and smoke are generated,

and the recording sheet of the present invention can be used as a copying base paper utilizin'g transmitted light.

Furthermore, since cuprous iodide is hardly influenced by environmental temperature and humidity, no storage container as required as is necessary in wet type recording sheets and recording can'always be carried out under a constant condition,

In theelectrorecording sheetof this'type, it is desirable thatthe resistivity of the conductive material be less than several-(Lem, and when this-material is applied on or mixed with a support sheet the surface resistivity of a finished recording sheet be less than several KS)..- This is because; by reducing the surface resistivity a high speed recording of about 3.5 m/ sec. can be effectedwith the applied voltageof'200 300 V. In order to'reduce the'surface resistivity of the recording sheet down to'lessthan several KQ, as stated above, with cuprous iodide having the resistivity of 10 (Item which is produced by the reaction of potassium iodide and copper sulfate,' suchcuprous iodide must be applied or contained in an amount of about 30 g/m?. However, with such a substantial amount of conductive material,

the finished recording sheet does not exhibit the nature of a plain paper, makes it difficult to be used in trans rriitting light recording sheet increases. t

It is an object'of the present invention to overcome the above-difficulties by lowering the resistance of cuprous iodide itself and provide an electroi'ecording sheet exhibiting plain paper properties.

Briefly, the present invention is based on and'the costof the recording the discov :ery of the fact that a material which imparts a free iodine component to cuprous iodide is effectively used as resistance lowering agent for lowering the resistance of cuprous iodide. i As the resistance lowering agent, those materials may be used, which by themselves can impart'an c omponentsuch as iodine or compound of iodine such as iodoform,tetraiodomethane, and an oxidizing agent .which serves to oxidize cuprous iodide to liberate an iodine component thereof such as potassium permanm It has been known that in an ion crystalhavin'g a composition which deviates from a stoichiometric one, a p-type semiconductivityis obseryedwhenf metal ions are short (or anions are excessive). As an example, it

has been known that the conductivity oficu ohas "a close connection with the content of oxygenand the conductivity increases as the content of oxygen becomes excessive; Chemical analysis shows that in cuprous iodide Cul'the content of' iodine I is excessive compared to the stoichiometric ratio derived from molecular formula, that 'is, one iodine atom to one copper atom. According to the investigation by Negel et al.,

' there exists aclose connection between the conductivity of Cu] and the iodine pressure and'the conductivity increases with the iodine pressure. It is considered that semiconductor which in turn increases the conductivity. Therefore, the resistance value of cuprous iodide is influenced by the amount of free iodine.

It has become possible to increase the amount of free iodine by addingthe resistance lowering agent to' commercially available cuprous iodide to thereby reduce the resistance value of cuprous iodide.

After a number of experiments it has been found that a remarkable result is observed when the amount of excess iodine of cuprous iodide is .in the range of 0.05 0.2 by weight, which cuprous iodide is used as the conductive material for the electrorecording sheet. When more iodine is included, the appearance after application of the conductive material is dirty and the excess iodine may fade out during the storage of the recorded sheet. Thus, it is inconvenient for practical use.

Many materials have been used in experiments for the resistance lowering agent for cuprous iodide and those materials which are listed hereinbelow have been found to be advantageous. Particularly. iodine, iodoform. tetraiodomethane and potassium permanganate showed remarkable effect. For iodoform and tetraiodomethane, it is considered that iodine atoms are liberated and absorbed in cuprous iodine so that the resistance value is reduced. For potassium permanganate, it is considered that it serves as an oxidizing agent for cuprous iodide and removes copper ions from cuprous iodide to produce vacant lattice points of Cu in order to enhance the properties of a p-type semiconductor. In any case, a suitable conductive material for the electrorecording sheet was obtained when the amount of excess'iodine of cuprous iodide was in the range of 0.05 0.2 by weight. The cuprous iodide with said resistance lowering agent did not show any change after a test at an environmental temperature of 60C and undenreduced pressure conditions (I mI-Ig) for 8 hours.

For the other materials listed later, they are advantageous for the resistance lowering agent for cuprous iodide but .changes of resistance value were observed afteran extended time of storage. No difficulty was encountered, however, in recording at room temperature.

. T he present invention will now be described in more detailwith reference to the accompanying drawings, in which;

FIG". lshows a construction of a form of recording sheet in accordance with the present invention;

FIG. 2 illustrates a recording method, and FIG. 3 8 show various forms of construction of recording sheets, in accordance with the present invenof cuproiis iodide having the resistance lowering agent therewith and an overlying color forming layer 3 including a color forming component which, in response to electric signals, forrris color upon application of heat energy thereto. Recording is effected by flowing electric current from an A.C. or DC. power supply 7, by

closing a switch 6, across a recording stylus electrode 4 and a counterelectrode or plane electrode 5 through the color forming layer 3 and the conductive layer 2 so that colored record 8 may be produced on the conductive layer 2 adjacent to the recording stylus electrode The recording sheet shown in FIG. 1 is a typical example of the construction. Various modifications may be constructed. Examples thereof are shown in FIGS. 3 8.

The recording sheet shown in FIG. 3 comprises a single layer 10 consisting ofa heat sensitive color forming component and cuprous iodide, formed on a surface of the support I.

The recording sheet shown in FIG. 4 comprises a conductive layer such as aluminum vapor deposition layer ll formed on the support 1 similar to that shown in FIG. I, and a conductive layer 2' of cuprous iodide and a color forming layer 3 successively formed thereon.

The recording sheet shown in FIG. 5 comprises a conductive layer 12 of carbon on a surface of the support 1 and an overlying layer 10 including a heat sensitive color forming component and cuprous iodide.

The recording sheet shown in FIG. 6 uses a carbon impregnated paper 13 in place of the support 1 shown in FIG. 3.

The recording sheet of FIG. 7 comprises a cuprous iodide impregnated paper 14 as a support and a color forming layer 3 thereon.

The recording sheet of FIG. 8 is formed by a paper in which cuprous iodide and heat sensitive color forming component are impregnated together.

Examples 1 and 2 described later are in accordance with the construction of FIG. 1 and the examples 3 through 7 are in accordance with the constructions of FIGS. 3 through 7, respectively.

Materials suitable for use in the present invention are given below:

1. Heat sensitive color forming material Those which form color in response to heat energy upon flowing current. They include a. combination of color forming dye such as crystal violet lactone and color forming agent of phenolic acidic material such as bisphenol A.

b. organic spot reagent and organic metal, and

c. redox indicator. These materials are dispersed in binder material to form color forming component.

a-l. Color-forming dye;

Generally, the color-forming dye used in a leuco body of triphenylmethane type dye represented by the below-mentioned general formula (I) or a leuco body of fluoran type dye represented by the below-mentioned general formula (II).

\ 0-o c--o Q00 (i=0 R2 R7.

wherein R,., R and R are individually a hydrogen or halogen atom, or a hydroxyl, alkyl, nitro, amino, dialkylamino, monoalkylamino or aryl group; and Z is an atom necessary to form a heterocyclic ring, and is O or S.

Concrete examples of the above-mentioned compounds are as shown below. Compounds of the formula (I):

3 ,3-Bis( p-dimethylaminophenyl )-phthalide 3,3-Bis( p-dimcthylaminophenyl )-6- climethylaminophthalidc (Crystal Violet Lactone) 3,3-Bis( p-dimcthylarninophenyl )-o-aminophthalide 3 .3-Bis( p-dimcthylamimiphenyl l-omitrophthalide 3.3-Bis( p 'dihutylamin iphcnyl Lphthalide 3 ,3-Bis( p-dimethylaminophenyl )-4,5,6,-7-tetrax chlorophthalidei v Y Compoundsfof'the formula (ll):

3-Dimethylamino-6-methoxyfluoran I 7-Acetamino-B-dimethylaminofluoran- 3-Dimethylamino-5,7 dimethylfluoran 3 -Diethylamino-5 ,7-dimethylfluoran 3 ,6-Bis-B-methoxyethoxyfluoran 3,6-Bis-,B-cyanoethoxyfluoran Other lactamcompoundsr t I ,l 9-p-Nitroani-lino-3,6-bis(diethylarnino )-9-xanthenylo-benzoic acid lactam (RhodaminB lactam) 9-p-Nitroanilino-. 3,6-bis(dimethylamino)9-thioxanthenyl-o-benzoic acid lactam The above-mentioned dye bases are effectively used.

They are scarcely soluble in water, and can be pulverized to fine particles of less than. 10 microns in size. a- 2. Color-forming agent: i I, I Preferable as the color-forming agent capable of I forming a dyeby chemical reaction with the colorforming dye mentioned in the preceding item (a-l i is a phenolic compound or an organic acid. it is desirable that thelsaid compoundor acid is solid at room temperature and can liquefy or vaporize at about70C. i

i. Examples of the phenolic compound areas follows; 3,5- r.yle nol,' thymol, I 4- t ert-butylphenol; 4- hydroxyphenoxide, me thyl-4-hydroxybenzoate, 4-

' hydroxyacetophenone, a-naphthol, fi-naphthol, catechol, hydroquinone, J rsorcinol, 4-ter toctylcatechol, 4,4-sec-butylidenediphenol, 2,2

dihydroxydiphenyl, 2,2-methylenebis(4-methyl-6- tert-butylphenol ),2,2 "-bis( 4-liydroirypheriyl)- propane, 4,4-isopropylidenebis-( Z-ter'tbutylphenol), 4,4sec-butylidenedphen'ol, pyrogallol and 4,4'-isopropylidenediphenol. i a ii. Examples of the organic aci d are as follows: Ste aric, gallic, benzoic, salicylic,' succinic, l-hydroxy- "2' naphthoic, 2-hydrox'y p-toluic, A ohydroliiybe nzoic, rn-hydroxybenzoic, phydroii'ybenzoic and 4-hydroxypl1'thalicacids b. Organic spot reagent and-organic metal salt: The organic spot'rea'gent referred toherein is' a com; pou'nd capable of being colored or discoloredby reaction with metalions. At'present, a large number of such compounds are'known. Inthe present invention, however, there is utilized the phenome non that at least' one of the organic spot reagent and the metal used in combination therewith is melted due to the heat energy generated at the time of application of electric currentand the tworeact with each other to'form a color. It is'therefore dc- 'sirable that one of the two which is lower in melting point is solid at below 70C. and has a melting point of l5()C. or less. In this respect, metallic 'soap is most preferable as the organic metal salt. Combinations of the organic spot reagent and the metal areas follows; I i 1. Organic spot reagent: Metal: Diphenylthiocarbazidc: Cu, Fe, Mg or Hg Dime thylglyoxime: Cu, Fe or Ni Benzoinoxime: Cu 8-Hydroxyquinoline: Cd, Cu, Fe, Pb, Mn, Ni or Zn Dinitrophenylcarbazide: Cd Rhodanine: Cu or Hg Diphenylthiocarbazone: Cu Ba, Co, Fe, Pb, Hg'orv'Zn Diphenylcarbazone: Co, Cu, Pb, Mn, Hg,'Ni or Triphenyl thiophosphate: =Ni

4 of developed color) Dimethylglyoxime: Nickel-stearate (Pink) p,p'-Tetramethyl-diaminodiphenylmethane:

Mn I T. Anthranilic acid: Zn

Pb or Diphenylbenzine: Zn

Catechol: Fe

Gallic acid: Fe

-DihydroXynaphthalene: Fe

Alizarine: Cu Quinalizarin: Cu

- ii. Organic metal salt:

As the organic metal salt, a metallic soap having the aforesaidmetal ions is effective. Typical examples of the combinations of organic spotreagents with organic metal salt s,-and color tones of colors developed by use *of said combinations, are shownbelow. Organic spot reagent:- Organic metal salt Color tone Benzoinoxime: Copper myristate (Yellowish green) I Dithiooxamide: Nickel stearate (Purple) 8l-lydroxyquinoline: Iron oleate"'(Black) Gallic acid: Ferric stearate (Black-)3 5 Alizarin: Copper oleate (Purplish red)- Quinalizarin: Copper oleate (Purplish/red)" Diphenylcarbazone: Copper stejarate Red) 'Diphenylcarbazone: Cadmium stearate (Red)- c. It has been found thata substance, which has heretofore been 'known as redox indicator, forms a color..in the vicinity of recording stylus at the time of application of electric current, and it has-been confirmed that said substance is effective as a color-forming material'for use in'electrorecording paperqThe redox indicator referred to herein is a substance which is colored or discolored due to oxidation with the heat generated at the time of application of electric current, and is a leuco body ispreferable in-view of the whiteness of the background. Examples of the redox indicators used in the present invention, and color tones of colors developed by said'indicators, are shown below. i Leucoethyl Nile Blue (Blue) Leucomethyl Capryl Blue (Blue) Leucotoluidine Blue (Purple) Leucodiphenylamine (Purple) Leuco-N-methyldiphenylamine-p-sulfonic acid (Reddish purple) Leucophen-ylanthranilic acid (Reddish purple) Triph'enyltetrazolium chloride (Red) *M ethylviologen (Purple) LeucosafranineT (Red) Leucoindigosul-fonic acid (Blue) Leucophenosafranine (Red) Leucomethylene Blue (Blue) Leucodiphenylbenzidine (Purple) Leucoerioglucine A (Yellowish green to Red) Leuco-p-nitrodiphenylamine (Purple) Leuco-malachite Green (Green) 2. Resistance lowering agent for cuprous iodide a. Iodine b. Iodine compound iodoform, tetraiodomethane, iodine salt, periodate, iodate, hypoiodate c. Peroxide hydrogen peroxide, sodium peroxide, barium=peroxide d. Oxyaeid salt hypochlorite, chlorate, perchlorate, bromate e. Peroxo acid peroxo-disulate, peroxo-sulfuric acid, peroxophosphoric acid f. Permanganate permanganic acid, poteassium permanganate, sodium permanganate, calcium permanganate, etc.

3. Binder In order to disperse in the state of fine particles the olor forming dye, color-forming agent, organic pot reagent and organic metal salt used in the col- .or-developing layer, and/or cuprous iodide and resi s tance lowering agent, and to impart bonding ability thereto, there is used a binder. Since most of the above-mentioned color-forming dyes, colorforming agents, organic spot reagents and cuprous iodide are "water-insoluble, the use of a watersoluble binder is effective. Further, the water ,soluble'substance has such characteristics that it is easily handled and treated at the time or production of recording paper.

i. Water-soluble binder:

Examples of the water-soluble binder' include hydroxyethyl-cellulose, carboxymethyl cellulose, methoxy cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, gelatin, starch, and gum arabic.

ii. Water-insoluble binder:

Asthe binder, an organic solvent-soluble binder may 1, also be used. In case a binary system comprising,

for example, a color-forming dye and a colorforming agent, is u'sjedas the thermorecording Irinaterial of the color-developing layer, the two components should individually be dispersed in the form'of fine particles into the binder. If either one of the.- two components is dissolved in a solvent used to dissolve the binder, a color formation reaction to deprive its function as a recording medium takes place at the time of mixing of the two. Accordingly, solvents for the binder mentioned herein are necessarily limited depending on the kind of color-forming components.

Concrete examples of the water-insoluble binder are natural rubber, synthetic rubbers, chlorinated rubbers, alkyd resins, styrene-butadiene copolymers, polybutyl methacrylate, low molecular weight ethylene polymers, low molecular weight styrene polymers, polyvinyl butyral, phenolic resins and nitrocellulose.

EXAMPLE 1 Mixed with 200 parts by weight of aqueous solution containing 1 by weight of polyvinyl alcohol (PVA 124 prepared by KURARE Co., Ltd.) was 200 parts by weight of cuprous iodide (prepared by KANTO CHEMICAL Co, Ltd.), and they were milled and mi-xed b y a mixer for two hours. During this process, 1 ml of aqueous solution containing 2 by weight o f-potassium permanganate was added. The dispersion solution thus formed is referred to as solution A. The dispersion solution A was applied on an artificial paper by a wire bar conditioned to form a coating layer of 8 microns in thickness (15 g/m in application quantity). The surface resistivity thereof was 3.5 4.5 X 10 Q. When KMnO was removed from the solution A, the surface resistivity was 2 5 X 10 0. Thus, it is clear that the surface resistivity was considerably reduced by the addition of KMnO as the resistance lowering agent to CuI. With a given amount of application, it is possible to use lower recording voltage since the surface resistivity is lower, or with less amount of application it is possible to obtain a desired surface resistivity, saving the cost and giving a more plain paper like property.

Next, mixed with 200 parts by weight of aqueous solution containing 1 by weight of polyvinyl alcohol was 35 parts by weight of 3,3-bis(pdimethylaminophenyl)-6-dimethylaminophthalide as color forming dye, and they were milled and mixed for 48 hours in a vessel of 500 ml inner volume. The dispersion solution thus formed is referred to as solution B. In the solution B, the color forming material scarcely dissolved but dispersed in the form of fine particles of no greater than 5 microns. In addition to the solution B, added to 200 parts by weight of aqueous solution containing 10 by weight of polyvinyl alcohol was 35 parts by weight of 4,4'-isopropylidenediphenol as color forming agent, and they were milled and mixed in a ballmill for 48 hours to prepare a dispersion solution hereinafter referred to as solution C. The color forming agent in the solution C also dispersed in the form of fine particles of no greater than 5 microns. Since the particles are surrounded by polyvinyl alcohol there is no direct contact between the particles. 15 parts by weight of the solution B and parts by weight of the solution C were measured and mixed together while agitating. The resulting solution is referred to as solution D. Thenthe solution D was applied to the artificial paper on which the solution A had previously been applied, by a iivire bar conditioned to provide a coating layer of aboutS microns in Zthickness. The paper was then dried to form a electrorecording sheet. The surface resistivity of the recording sheet thus formed was 4.2 K0 and could provide a sharp record having a reflective optical density of 0.88 by using recording voltage of 300 V. Furthermore, it was possible with this recording sheet to carry out transmitted light copying.

The relationship between the amount of KMnO added when the solution A was applied and the surface resistivity under the above conditions is listed below.

Whenthe amount of addition exceeded 1/10 the solution became reddish and the conductivity reduced because the amount of. cuprous oxide increased;

EXAMPLE 2 Added to 200 parts by weight of hydroxyethylcellulose (Cellosise WP-300I-I prepared by Union Carbide International Co.) was 200 parts by weight of cuprous iodide and 0.5 parts by weight of iodine (prepared by KANTO CHEMICAL Co., Ltd.), and they were milled and mixed by a mixer for 2 hours. The dispersion solution thus prepared is referred to solution E. The dispersion solution E was then applied on an artificial paper by a wire bar conditioned to provide a coating layer of 10 microns in thickness, and the paper was dried. The surface resistivity after application was 2 3 X 10 Q. When the iodine was not added as the resistance lowering agent, the surface resistivity was 2 5 X 0.. Thus, it is clear that the surface resistivity was considerably reduced by the addition of iodine. Recordingunder a lower recording voltage can thus be at- 1 tained.

Next, added to 100 parts by weight of aqueous solution containing 5 by weight of hydroxyethylcellulose (Cellosise WP-09L) was 20 parts by weight of 3,3 bis(- p-dimethylaminophenyl)-6-dimethylaminophthalide as color forming material, and they were milled and mixed in a ballmill for 48 hours. The solution thus prepared is referred to as solution F. In addition, added to 100 parts by weight of aqueous solution containing 5 by weight of hydroxyethylcellulose (Cellosise WP-09L) was 35 parts by weight of 4,4'-isopropylidenediphenol as color forming agent, and they were milled and mixed in a ballmill for 48 hours. The solution thus prepared was referred to as solution G.

parts by weight of the solution F and 100 parts by weight of the solution G were mixed and the mixture was applied onto the artificial paper on which the solution E had previously been applied, by a wire bar conditioned to provide a coating layer of about 5 microns in thickness. The paper was then dried to form an electrorecording sheet. The surface resistivity of the electrorecording sheet thus formed was 3.8 K O. and could provide recording h'aving reflective optical density of 0.91 using the recording voltage of 300 volts.

EXAMPLE 3 weight of both mixture were mixed to prepare solution I. I00 parts by weight of the solution H and 30 parts by weight of the solution I were mixed by a mixer and applied onto a paper with the thickness of 15 microns. It was then dried to form a light yellow recording sheet. The surface resistivity of the recording sheet was 1.45 X 10 .Q and a sharp, dark gray record having reflective optical density of 0.80 was obtained at the recording voltage of 300 volts. The structure'of the recording sheet is shown in FIG. 3. A color forming conductive layer 10 is provided on the paper 1.

The recording sheets were prepared with varying amounts of iodoforrnv addition tocuprous iodide in the solution H to determine the value of the recording voltage at which the reflective optical density of the record trane showed 0.80. The result is given below.

As seen from the above table, the surface resistivity of the recording sheet could be reduced by adding iodoform to cuprous iodide to provide a record having a sufficient density at a relatively low recording voltage.

EXAMPLE 4 Added to I00 cc of toluene solution containing 10 by weight of copolymer of styrene and butadiene at .the ratio of 15 were grams of cuprous iodide and 0.5 grams of,tetraiodomethane,and they were milled and mixed in a ballmill for 48 hours. The dispersion solution thus prepared was applied onto an aluminum de posited paper by a wire bar conditioned to provide a coating layer of 15 microns, and the paper was dried. The surface resistivity of the applied paper was 4.3 X

Next, added to 200 parts by weight of aqueous solution containing I0 by weight of polyvinyl alcohol was 35 parts by weight of 3-dimethylamino-6- methoxyfulorane as color forming material, and they were milled and mixed in a ballmill for48 hours, 10 parts by weight of this mixture, 10 parts by weight of the solution C defined in the ExampIe l and 5 parts of the dispersion solution of cuprous iodide including tetraiodomethane were mixed together and then applied onto said conductive layer by a wire bar conditioned to provide a coating layer, of l0irnicrons in thickness. The structure of the recording sheet thus formed is shown in FIG. 4. Aluminum deposited layer 11 is formed on the paper 1, and a conductive. layer 2 and a color forming layer 3 are formed thereon. The surface resistivity was 8.3 X 10 .Q and sharp, red record having the reflective optical density of 0.85 was obtained at the recording voltageof 350 V. When tetraiodomethane was not added, the recording sheet prepared otherwise under the same conditions showedthe surface'resistivity of 6 X l0 Q and provided the record having reflective optical density of 0.35 at the recording voltage of 600 V.

EXAMPLE 5 Amorphous carbon Styrene low polymer Toluene qPpe-r. I

, 1 Next, 10 parts by weight of leuco Malaeliite G reen,

100 parts by weight ofj eiiprous iodide; 0.2"parts by weight of sodium peroxide, 5 parts by weightbfpoiystyrene sodium sulfonate and 130 parts by weight of water were milled and'mixe'd for 24 hours'and then the mixture was applied onto said conductive layer to form a coating layer of micron'thickness when dried. .A light yellow recordingshe' et was obtained. When a recording stylus was scanned with a DC. voltage of 40 volts being applied, a green recording trace was produced. When sodium peroxide was not added as the oxidizing agent, recording was not attained unless a recording voltage higher than 70 volts was applied. FIG. 5 shows the structure of the recording sheet. Carbon layer 12 and color forming conductive layer 10 are 'formed on the paper 1.

EXAMPLE'6 I t v "fp altnitatc i parts by wcigh t v I Solution Aqueous solution i K containing lOf/c lOQparts by weight 'PVA.-

Diphcnylca'rbazonc '25 partsby-weight *1 .1 t s n. -Aqueous solution v L containing l0 100 parts by weight NEVA I .11 h Cuprous iodide 1000 parts by weight I 'Pcroxirsulfuri c i acid '-l part byweig'h't r Solution Aou'cous solution i M containing 5 "J. 1000 parts by weight PVA Theabove .threesolutionswere respectively milled and mixed for-24rhours, and, l.5 ,parts by weight of the solution K, 15 partsbyweightipf the solution L and. 100

parts by weightofithelsolution M weregmixedtogether f-and applied onto.;a.co.nductive paper (havingthe sur.- face conductivity-ofi250 Q.)- including 40 of carbon fiber to f orm coating layer of lO micron thicknessto complete a electrorecording sheet.

,when ReIO XOeSlJifUI'iQ acid was not added, no record was obtained at the'recording voltage of 100V, but ,whenit wasadded, red record was. obtained at the. re-

, cording voltage of V The structure of the recording sheet thus formedis shown in FlG. ,6,-Color forming conductive layer 10 is formedona carbon impregnated paper 13 l f-EXAM'PL Bleached sulfitepulpuwas beaten thoroughly by a beater. Added to the resultingpaper base solution were a sizing agent and 1000 parts by weight of cuprous iodidein' the form of,fine particles and l part by weight of iodine. The paper material was then papered by. a cylinder paper machine so that a paper thickness of 45 g/m was obtained. In this base, since a considerable amount of the conductive material together with the sizing agent flows into white water during the papering 6 of. said, cuprous iodide,

. EXAMPLE ,8

W In 'the'process of tlieExarn plej, the paper material wasp apered sothat 6.0 by weight of euprousiodide and 2.0 by weight of :leuco Methylene Blue were included. At this tinie, periodate was added ail/1 0 parts weightw'ith respect to cup'rous iodide as the resistance lowering agent for ,cuprous iodide. recording sheet prepared could provide abltie record having the reflective optical densityof' at the recording voltage of 600 V. When periodate was notadded; record was obtainable at therecording voltage 600 FIG. .8 shows the structureof the recording sheet,

wherein a conductive component and color forming component are impregnated in the paper. I I i wr a is claimed is:; Y

1. An electrorecording sheet comprising a heat sensitive'color forming componen t for forming color or changing its color. upon application of heat .energy thereto, cuprous iodide. for imparting conductivity and a support for carrying the above, components, said electrorecording sheet for providing arecorded mark when electric current is flowed therethroughin selected areas thereof, by the fact that the heat sensitive color forming component in said selected areas forms color or changes its color, said sheetadditionally comprising a resistance lowering agent for providing ,saidcuprous iodide with a freeiodine componentto lower resistance 2. An electrorecording sheet accordingto, claim 1, wherein said resistance-loweringagent is a material ca- -,pable of providing its own iodine component. 3. An electrorecording sheet according to claim 1,

nent is iodine.

5. An electrorecording sheet according to claim 2, wherein said material for providing an iodine compon'ent is a compound of iodine.-

6. An electrorecording sheet. according to claim 3, wherein said oxidizing agent includes at least'one material selected from the group consisting of peroxide, oxyacid salt and peroxo acid.

7.-.An electrorecording sheet according to claim 3, wherein said oxidizing agent ispermanganate.

8. An electrorecording sheet according to claim 1, wherein said heat sensitive color forming component is a combination of a'leucb body of tri-phenylmethane 0 dye or a leuco body of fluo'ranesdyeand organic acid or-phenolic materials 4 i 9. An electrorecording sheet according to claim '1, wherein said heat sensitive color forming component is a combination of metallic salt and an organic spot reagent which repidly reacts with metal ions of said metallic salt to provide a" reaction product having appreciabl'e visual change, one-of said two materials which has the lower melting point has a melting point of 70 10. An electrorecording sheet according to claim 1, wherein said heat sensitive color forming component is a leuco body of redox indicator.

11. An electrorecording sheet according to claim 1, wherein said cuprous iodide and said resistance lowering agent are dispersed in binder material and applied as a conductive layer on said support, and said heat sensitive color forming component is dispersed in binder material and applied as a color forming layer on said conductive layer. I

12. An electrorecording sheet according to claim 1, wherein said cuprous iodide, said resistance lowering agent and said heat sensitive color forming component are dispersed in binder material and applied on said support.

13. An electrorecording sheet according to claim 1 1, wherein said support is made of one material selected from the group consisting of paper, fabric, plastic film, glass, carbon impregnated paper, metal deposited paper and carbon applied paper.

14. An electrorecording sheet according to claim 12, wherein said support is made of one material selected from the group consisting of paper,- fabric, plastic film, glass, carbon impregnated paper, metal, deposited paper and carbon applied paper.

15. An electrorecording sheet according to claim 1 1, wherein said color forming layer includes cuprous iodide.

16. An electrorecording sheet according to claim l5,

wherein said color forming layer further includes a resistance lowering agent.

17. An electrorecording sheet according to claim 1, wherein said support is formed by a fiber impregnated member in which cuprous iodide and a resistance lowering agent are impregnated, said a heat sensitive color forming component is dispersed in binder material and applied as a color forming layer on said support.

18. An electrorecording sheet according to claim 1, wherein said support is formed by fiber impregnated member in which cuprous iodide, resistance lowering agent and heat sensitive color forming component are impregnated.

19. An electrorecording sheet, comprising:

a heat sensitive color forming component for forming color or changing color upon the application of heat energy thereto;

cuprous iodide for imparting electrical conductivity to said sheet;

a resistance lowering agent for providing said cuprous iodide with a free iodine component for lowering the electrical resistance of the cuprous iodide, and

a support for said component, cuprous iodide and agent; said sheet being capable of providing a recorded mark when an electric current is flowed through selected areas thereof, thereby causing said heat sensitive color forming component to form a color in said selected areas.

Claims

1. AN ELECTRORECORDING SHEET COMPRISING A HEAT SENSITIVE COLOR FORMING COMPONENT FOR FORMING COLOR OR CHANGING ITS COLOR UPON APPLICATION OF HEAT ENERGY THERETO CUPOROUS IODIDE FOR IMPARTING CONDUCTIVITY AND A SUPPORT FOR CARRYING THE ABOVE COMPONENTS, SAID ELECTRORECORDING SHEET FOR PROVIDING A RECORD MARK WHEN ELECTRIC CURRENT IS FLOWED THERETHROUGH IS SELECTED AREAS THEREOF, BY THE FACT THAT THE HEAT SENSITIVE SOLOR FORMING COMPONENT IN SAID SELECTED AREAS FORMS COLOR OR CHANGES IS COLOR, SAID SHEET ADDITIONAL COMPRISING A RESISTANCE LOWERING AGENT FOR PROVIDING SAID CUPROUS IODINE WITH A FREE IODINE COMPONENT TO LOWER RESISTANCE OF SAID CUPROUS DIDE.

2. An electrorecording sheet according to claim 1, wherein said resistance lowering agent is a material capable of providing its own iodine component.

3. An electrorecording sheet according to claim 1, wherein said resistance lowering agent is an oxidizing agent for oxidizing cuprous iodide to liberate an iodine component.

4. An electrorecording sheet according to claim 2, wherein said material for providing an iodine component is iodine.

5. An electrorecording sheet according to claim 2, wherein said material for providing an iodine component is a compound of iodine.

6. An electrorecording sheet according to claim 3, wherein said oxidizing agent includes at least one material selected from the group consisting of peroxide, oxyacid salt and peroxo acid.

7. An electrorecording sheet according to claim 3, wherein said oxidizing agent is permanganate.

8. An electrorecording sheet according to claim 1, wherein said heat sensitive color forming component is a combination of a leuco body of tri-phenylmethane dye or a leuco body of fluorane dye and organic acid or phenolic material.

9. An electrorecording sheet according to claim 1, wherein said heat sensitive color forming component is a combination of metallic salt and an organic spot reagent which repidly reacts with metal ions of said metallic salt to provide a reaction product having appreciable visual change, one of said two materials whicH has the lower melting point has a melting point of 70* - 150*C.

10. An electrorecording sheet according to claim 1, wherein said heat sensitive color forming component is a leuco body of redox indicator.

11. An electrorecording sheet according to claim 1, wherein said cuprous iodide and said resistance lowering agent are dispersed in binder material and applied as a conductive layer on said support, and said heat sensitive color forming component is dispersed in binder material and applied as a color forming layer on said conductive layer.

13. An electrorecording sheet according to claim 11, wherein said support is made of one material selected from the group consisting of paper, fabric, plastic film, glass, carbon impregnated paper, metal deposited paper and carbon applied paper.

14. An electrorecording sheet according to claim 12, wherein said support is made of one material selected from the group consisting of paper, fabric, plastic film, glass, carbon impregnated paper, metal deposited paper and carbon applied paper.

15. An electrorecording sheet according to claim 11, wherein said color forming layer includes cuprous iodide.

16. An electrorecording sheet according to claim 15, wherein said color forming layer further includes a resistance lowering agent.

19. An electrorecording sheet, comprising: a heat sensitive color forming component for forming color or changing color upon the application of heat energy thereto; cuprous iodide for imparting electrical conductivity to said sheet; a resistance lowering agent for providing said cuprous iodide with a free iodine component for lowering the electrical resistance of the cuprous iodide, and a support for said component, cuprous iodide and agent; said sheet being capable of providing a recorded mark when an electric current is flowed through selected areas thereof, thereby causing said heat sensitive color forming component to form a color in said selected areas.