US3476578A

US3476578A - Thermographic method for producing thermostable prints

Info

Publication number: US3476578A
Application number: US559487A
Authority: US
Inventors: Eric Maria Brinckman
Original assignee: Agfa Gevaert NV
Current assignee: Agfa Gevaert NV
Priority date: 1965-06-22
Filing date: 1966-06-22
Publication date: 1969-11-04
Anticipated expiration: 1986-11-04
Also published as: FR1496154A; NL6608615A; BE682768A; CH511722A; GB1160223A; DE1571819A1

Description

9 E. M. BRINCKMAN 3,476,578

THERMOGRAPHIC METHOD FOR PRODUCING THERNOSTABLE FRINIS Filed June 22. 1966 FIG; 2

INVENTOR ERIC MAR/A BRINCKMAIN WATSON, COLE, GR/NDLE & WA TSON ATTORNEYS United States Patent THERMOGRAPHIC METHOD FOR PRODIKIING THERMOSTABLE PRINTS Eric Maria Brinckman, Mortsel-Antwerp, Belgium, as-

signor to Gevaert-Agfa N.V., Mortsel, Belgium, a Belgian company Filed June 22, 1966, Ser. No. 559,487 Claims priority, application Great Britain, June 22, 1965, 26,468/65 Int. Cl. B41m /18; B44d 1/22; C08d 13/24 US. Cl. 117-36.2 Claims ABSTRACT OF THE DISCLOSURE A thermographic reproduction method in which a heatlabile reactant of a two-reactant color-forming system carried in a heat-sensitive layer of a heat-sensitive recording material is rendered non-reactive by exposure to a heat image of the information to be reproduced and unaifected reactant remaining in the unexposed areas of the layer are transferred to a copy material brought in contact therewith for reaction with the second reactant of the color-forming system provided on the copy material, producing on the copy material a colored image corresponding to the unexposed areas of the recording material. The heat-sensitive material preferably includes heat-absorptive material uniformly distributed in heatconductive relation to the heat-sensitive layer, most preferably within the same layer, and the heat-absorptive material preferably converts electromagnetic radiation, especially infra-red radiation, to heat.

A recording material useful in the method is also disclosed which includes a heat-sensitive layer uniformly containing a heat-labile reactant of a color-forming system as well as a finely divided material adapted to absorb infra-red radiation and convert the same to heat.

The present invention relates to a method of recording and reproducing information by means of heat. More particularly the present invention relates to a thermographic method for producing thermostable prints.

It is known to reproduce graphic originals by means of a heat-sensitive material containing chemical reagents, which on heating form a coloured product. However, the prints produced with such materials have the drawback of not being thermostable.

In the process according to the present invention for recording information a recording element is used containing a reactive compound or composition which is destroyed, blocked or reduced in reactivity or removed from the said element by the action of the image-wise or record-wise applied or induced heat. On the non-heated areas the said compound or composition remains at disposal for reacting with a compound applied thereto or can be transferred to a receiving element eg by diffusion, tearing out, or vaporization so as to produce in the receiving material a change in physical or chemical character, e.g. a change in light absorption, a change in colour or colour density. A change in colour can be produced by a colour coupling reaction, a change in colour density by a bleaching out reaction.

The way wherein the heat is applied or induced imagewise or record-wise supplied is of no importance. For various embodiments of image-wise heating, which embodiments may also be applied in the present invention, there We refer to Belgian patent specification 656,713 which should be read in conjunction herewith. According to the embodiments particularly described therein an infra-red radiation source is used for supplying the necessary heat energy. However, the recording of information supplied in the form of visible light is not ex- 3,476,578 Patented Nov. 4, 1969 eluded since this light can be e.g. in the recording element itself converted into heat.

The heat to be supplied during the recording step can be supplied by conduction of thermal motion, e.g. from infra-red absorbing image-markings on an original to the heat-sensitive element, but is preferably produced in the heat-sensitive element itself by the conversion of electromagnetic radiation into heat in substances that are distributed in the heat-sensitive material and that are in heat-conductive contact with the compound or composition which has to be destroyed, blocked in reactivity or removed from the heat-sensitive element by heating.

For recording techniques wherein use is made of such substances we more particularly refer to Belgian patent specification 657,502.

In order to obtain positive, legible prints a direct or reflectographic exposure technique can be used. However, a reflectographic exposure technique is preferably applied and using a recording material containing in the recording element (e.g. layer) or in an element or coating in heat-conductive relationship therewith, a substance or substances that absorb the copying light, and convert it into heat. The transparency of the recording material used for reiiectographic exposure is preferably such that at least 20% and at most of the copying light is transmitted. Refiectographic exposure is possible when carrying out the present invention, not only when the information to be recorded is supplied as a visible light pattern but also when it is supplied as a pattern of infrared radiation if an element is used (whether forming part of the recording material or not) which transmits a certain amount of infra-red radiation but is selectively or dilferentially heated in view of the radiation reflected from the original (see Belgian patent specification 664,- 329). Whatever technique is selected it is to be understood that substances that absorb copying light (or infrared radiation) and convert it into heat may if desired be present in and/or on a layer other than the thermosensitive layer of the thermo-sensitive material, provided there is sufficient thermal contact to conduct heat generated therein to the thermo-sensitive substances. Such other layer may be another layer of the thermo-sensitive material or a layer (e.g. a self-supporting layer, or a supported layer or coating) forming or forming part of a material separate from the thermo-sensitive material, in other words a heat pattern can be firstly produced, in a separate element and conducted therefrom to the heatsensitive material. For the two last mentioned embodiments particularly in view of the use therein of a mainly infra-red emitting radiation source and copying apparatus reference is made to Belgian patent specification 664,329 which should to be read in conjunction herewith.

In its preferred form the recording process according to the present invention comprises the following features:

(a) Provision of a recording material or element containing a reactive compound e.g. a coupler, which can be destroyed, blocked in reactivity or removed from the said element by the action of thermal motion that is image-wise produced by image-wise reflected electromagnetic radiation in a substance or substances which is or are homogeneously distributed in the thermo-sensitive element and absorbs said radiation and convert it into heat, and

(b) Contact of the exposed recording element with a receiving material or element containing a reactant for the compound or composition still available, in order that transfer of said compound or composition by diifusion in dissolved, evaporated or melted state to said receiving element may take place possibly together with softened binder (if such is present) which becomes torn out when the elements are subsequently separated.

When applying a reflex exposure method the intensity of the exposure and the sensitivity of the recording element containing said radiation absorbing substances, which convert the applied radiation into heat, are chosen in such a Way that on the absorption of the light or other rays directed to the original and striking undiiferentially the light-sensitive layer, the heating resulting therefrom, causes practically no or only a slight inactivation or loss of the reactive compound or composition. The additional image-wise heat resulting from the image-Wise reflected radiation produces in the recording material the practically useful image-wise elimination of the said compound or composition.

It is to be understood that when applying a reflectographic exposure technique the original to be reproduced must be an original containing image areas or an imagebackground that reflect(s) copying radiation, e.g., light or a transparency which has copying light absorbing image areas and which during the exposure is held with its back side in contact with or near proximity to a copying light reflecting material.

Having stated in general the concepts of this invention a detailed description will now be made of the composition and structure of various heat-sensitive materials, types of radiation sources, and exposure, development and transfer techniques which can be used in the present invention.

For preparing a heat-sensitive material suitable for use according to the present invention a colour reactant or colour bleaching compound or composition, which can be destroyed, blocked in reactivity or removed from the said element by heating, is applied with or without a binder to a suitable support. The support may be permeable so that said compound or composition can be incorporated therein by impregnation. In the case a binder is used said binder can be chosen so that, in softened state, it can be transferred to a receiving material.

Suitable binders are ex. gelatin, carboxymethyl cellulose, tragacanth gum, alginic acid and the salts or esters thereof, poly(vinyl alcohol), poly(acryl amide), poly- 4 (vinyl pyrrolidone), ethylhydroxyethyl-cellulose, ethylcellulose, poly(vinyl butyral), cellulose triacetate, cellulose acetobutyrate, ethylcellulose-p-sulphonic acid benzoate, sucrose benzoate, poly(methyl methacrylate), polystyrene, polyethylene, polypropylene, poly(ethylene terephthalate), copoly(vinyl chloride/alkyl acrylate), copoly(nitrostyrene/maleic acid/monoethyl maleate), copoly(styrene/monoethyl maleate), copoly(vinyl methyl ether/maleic anhydride), copoly(maleic acid/nitrostyrene), copoly(vinyl chloride/methyl acrylate/ ethyl acrylate), partially nitrated copoly(methyl acrylate/styrene), natural resins and waxes, e.g., carnauba wax, beeswax and colophony.

Obviously a combination of two or more of the enumerated binders is also suitable, e.g., a mixture of gelatin and carboxymethylcellulose, gelatin and polyethylene in emulsified state, ethylcellulose and carnauba wax.

The binder and the thermo-sensitive compound or composition are preferably dissolved in a common solvent. Binders insoluble in water may be dissolved in an appropriate organic solvent, but they may be used as an aqueous emulsion (latex) as well. Solvents, which can be utilised in preparing the heat-sensitive layer, are i.a. water, methanol, ethanol, ethylene glycol monomethyl) ether, methylene chloride, acetone, cyclohexanone, diethylene glycol, amyl acetate, dioxan, diethylene glycol monoethyl ether, trichloroethylene, toluene, or a mixture of at least two of the foregoing solvents.

The flexibility of the heat-sensitive layer can be secured by the use of plasticizers such as glycerol, sorbitol, polyglycols, polyethylene glycols, stearic acid and the esters thereof, esters of adipic acid and sebacic acid, polyethylene sebacate, polyethylene adipate, dimethylglycol phthalate, alkylaryl sulphonates, chlorinated diphenyl compounds, castor oil, pine oil, triphenyl phosphate, tricresyl phosphate, and dibutyl phthalate.

In the following table appropriate combinations of colour reactants that are suitable for use in the recording material (column A) and colour reactants that are suitable for use in a receiving material (column B) are grouped.

(1) Compounds splitting off sulphur such as dithiooxamide, thioacetamide and p-phenylenedithiourea.

(2) Acids such as oxalic acid, and malonic acid.

(3) Oxidising agents such as benzoyl peroxide,

and tetrachloroquinone.

(4) Couplers for diazotype such as 2,3-dihydroxy-iiaphthalene, phloroglucinol and resorcino (5) i-phenyl-B-pyrazolidinone and derivatives such as l-phenyl-4-methyl-3-pyrazolidinone, and 1-(p-tolyl)-5-phenyl-3-pyrazolidinone.

(6) 8-hydroxy-l,2,3,4-tetrahydroquinoline and derivatives.

(7) Phenols and naphthols e.g. pyrocatechol, tert.-butyl-pyrocatech0l, pyrogallol, tort.- butyl-pyrogallol, 4-amino-1-naphthol, methoxy-I-naphthol, resorcinol, 2,3-dihydroxynaphthalene and 1,4-dlhydroxynaphthaone.

(8) Compounds containing an active methylene group such as N,N-dimethylbenzamide and N -methylacetamide.

Inorganic and organic salts or soaps of iron, copper, silver, mercury, lead, nickel, cobalt and cadmium such as copper stearate, silver nitrate, silver stearate, silver behenate, silver palmitate, mercury stearate, lead acetate, lead stearate, lead myristate, nickel acetate, nickel stearate, cobalt stearate, cadmium stearate and lead benzyl mercaptide.

Compounds that are sensitive to changes in the pH-value, e.g. leucomalachite green, leucomethyl green, leucofuchsine and leucolissamine green.

All compounds changing colour on oxidation e.g. p-chloroaniline, methyl-p-amino, phenol sulphate, N,N-d1methyl-p-phenylenediamine, antipyrine, pyrogallolpyrocatechol and 4methoxy-l-naphthol.

Aromatic diazo compounds e.g. the 4-(N,N-diethylamino)-benzene diazonium double salt with zinc chloride, p-nitrobenzene diazonium fluoroborate, and pdiethylaminobenzene-diazonium tetrafiuoroborate.

Silver salts such as silver nitrate and silver behenate, gold salts such as gold chloride and gold stearate, triazolium compounds such as 2,3-diphenylnaphtho-[1,2]- triazolium chloride and 2-pheriyl-3-(o-carboxy-phenyl)-naphtho-[1,2]-triazolium chloride, tetrazolium compounds such as 2,5-diphenyl-3-(o-carboxyphenyD- 2,l, 3,4 tetrazo lium chloride and 2,5-diphenyl-3-(p-rnethoxy-phenyl)-2,1,3,4-tetra- Z0lll. 1m chloride, leucophthalocyanines such as Phthalogene Blue IB (Farbenfabrikcn Bayer AG, Leverkusen. W. Germany).

Inorganieand organic salts or soaps of iron, copper, silver, gold, cobalt and cadmium such as iron (III) chloride, iron (III) stearate, iron (II) chloride, iron (II) sulphate, 11011 (II) stearate, copper (II) chloride, copper (II) stearate, silver nitrate, silver behenate and cobalt (II) chloride. 7

Oxidising agents such as potassium dichromate and ammonium molybdate 5-bi omo-2-amino-thiazoles e.g. 2-ethylamin0-4-phenyl-5-bromothiazole and 2- diphenylaminoi-phenyl-fi-bromothiazole.

(9) Amines such as p-phenylenediamine, Aromatic aldehydes and ketones eg; tetrachloroquinone, 1,4-naphthoquinone,

m-phenylenediamiue and d t anolainine.

z-chloronaphthoquinoiie, s-chlorovanillin -dimeth lamino-benzal eh do 2,4-dinitro-benzaldehyde. p y d y and (10) Nitroso derivatives e.g. N-nitrosodiphenylamine, p-nitrosodimethylaniline and l-nitroso-2-naphthol.

(11)1riazene compounds such as 1,3di-

phenyl triazenez (12) Aromatic amines and aromatic aminohydroxy compounds eg l-amino-Z-naphthol, S-hydroxy-quinolme, pphenylenediamine, and m-phenylenediamine.

Aromatic hydroxy compounds e.g. pyrogallol, galllc acid, methylaminophenosulphate, and 4-methoxy-1-naphthol. -Metal salts e.g. iron (II sulphate and cobalt acetate. Amines, e.g. 2,5-diamino-toluene and benzylaniline.

Coupling agents for diazotype printing e.g. 3-hydroxy-2-naphthanilide and 3- hydroxy-N-2-naphthyl-2-naphthamide.

Sulphur-containing compounds e.g. sodium sulphide, sodium trithionate, thioacetamide and thiourea.

Silver salts ag. silver nitrate, silver behenate, silver stearate, gold salts e.g. gold (III) chloride and gold stearate.

Mercury salts e.g. mercury behenate.

(13) Nitro compounds e.g. 2-nitro-4 chloroaniline, 1-chloro-2-nitro-4-diethyl sulphamoyl-benzene and dinitroresorcinol.

(14) Compounds that, on heating, set free alkali e.g. those described inBelgian patent specification 612,963 and alkaline compounds eg. diethanolamine, tetramethylguanidine, p-phenylenediamine, and triethylamine.

Metal salts eg. iron(III) chloride, iron(II) sulphate and cobalt acetate.

Oxidisable compounds such as 4-amlno-diphenylamine-2-sulphonic acid.

Compounds that change in colour when the pH changes, e.g. the leucoforrn of pnitrophenol, phanol-phthaleine, bromothymol blue chlorophenol red, bromo cresol purple, oxonol dyes and 1,2,3,4-tetrahydro-4-[2-(3-methyl-2-henzothiazolinylidene)ethy1idene1-xanthylium-tetrachloroferrate (III).

Mixtures of a diazonium salt and a coupler e.g. the combination of p-diethylamino-benzene diazonium tetrafluoroborate and phloroglucinol.

As radiation absorbing substances which can be in heat-conductive relationship with the thermo-sensitive reactive compounds or composition, present in the recording element, are used e.g. infra-red and/or visible light absorbing pigments e. g. dispersable dyes. As pigments are more particularly mentioned: carbon black, graphite, oxides or sulphides of heavy metals having an atomic weight between 45 and 210, such as manganese, nickel and lead sulphide, or these heavy metals themselves in finely divided state such as silver, bismuth, lead, iron, cobalt and nickel. s

According to a special embodiment the thermosensi tive recording layer, during the exposure with visible light, is in uniform heat-conductive relationship with coloured substances that absorb light of a determined part ofthe visible spectrum and convert it into heat; A thermosensitive recording layer optically sensitised in this way can be used for recording coloured light patterns.

-It is to be understood that mixtures of said coloured substances can be used too, so that light of the whole visible spectrum is absorbed. Further the said substances need not absorb in the range of the visible spectrum alone; they may, absorb in the infra-red region although for. the recording'of red coloured image-markings ,the latter absorption is preferably as. low as possible.

The coloured substances or mixture of said substances when-usedfor optical sensitization of the thermo-sensitive layer absorb preferably light corresponding to at least one of the primary colours (red, green, blue or subtractive colours (cyan, magenta, yellow).

Substances that absorb visible lightof a part of the visible spectrum and wherein absorbed lightenergy is converted into heat are e.g. dyes belonging to the classes of the azo dyes, the triarylmethane dyes, the xanthene dyes, the acridine dyes, the methine dyes, the azine dyes, the phthalocyanine dyes, the allied dyes.

In order toobtain a locally sufiiciently high heating efiect for the image dilferentiation according ,to the present invention these dyes are preferably used in finely; dispersed state. The grain size of the dyes is preferably lower than 0.1

Therecording material normally has an optical density of between :05 and 1.50; in the case of reflectographic exposure it preferably has an optical density for the light to be absorbed of between 0.20 and 0.80.

The reaction compounds in the heat-sensitive layer are preferably used in an amount of 10'- to mol per sq.m.

anthraquinone dyes and The support (if any) for the heat-sensitive element is selected dependent upon the exposure technique applied, for example, according to whether contact printing, in which the radiation is transmitted through the original to the heat-sensitive layer or reflex printing, in which the radiation is transmitted through the heat-sensitive layer to the original, is used. In the latter case the support should absorb as little copying light as possible. If the heat-sensitive element is a self-supporting layer, it is of course not necessary for the recording: material to comprise a support from such layer.

In the direct contact printing method there are several variations possible. For instance, the original, which is a transparency, is placed in contact with the heat-sensitive layer taking care that there is created no heat-conductive relationship of the image-markings with the heat-sensitive layer or such heat-conductive relationship is only created to a minor extent (e.g. by applying no pressure). The heat-sensitive layer contains a substance absorbing the copying light and converting it into heat. According to another embodiment the transparent document possessing light-absorbing characters, which are heated by the absorbed light, is placed with itscharacters in thermal contact with the heat-sensitive layer, which, in that case, is sufliciently transparent for the copying light.

In the normal reflex printing method, the original e.g. a line copy is placed with the image bearing surface in thermal contact with the heat-sensitive layer and exposure takes place through the latter.

According to a special reflex printing method, which is more particularly described in the examples and illustrated by the accompanying drawing and is also described in Belgian patent specification 664,329, the heat-sensitive layer during reflectographic exposure does not stand in real thermal contact with the original, which is chosen in such a way that it image-wise reflects the copying light or contains a back-ground reflecting that light. In this case the heat-sensitive layer is in uniform thermal contact with a substance or substances that absorb(s) the copying light and convert(s) it into heat and that is or are present on and/ or in either an element of the heatsensitive material or a separate element that e.g. forms partof the copying apparatus. For more details about such an apparatusv and separate element: reference is made to Belgian patent specification 664,329.

The heat-sensitive compound or composition which remained intact i.e. which is still present, after the imagewise exposure to heat, can be developed on the recording material itself or transferred to a receiving material containing a reactant for said compound or composition-The transfer can be carried out by means of a liquid or by non-differentially supplying an amount of non-destructive heat in order to vaporize or melt the thermosensitive image-forming compound or composition so that it can diffuse in that state to the receiving material.

The non-destructive heat preferably effects in the heatsensitive element an increase of temperature comprised between 50 and 250 C.

The effectiveness of the recording with electromagnetic radiation, which yields the necessary energy for heating the recording element, substantially depends on the intensity of the radiant energy. For example, a recording layer that does not provide a sufficient differentiation in concentration of thermo-sensitive reactive compound or composition with a particular source of electromagnetic radiation energy may be fully effective if the energy level is substantially increased.

Radiant energy of a brief duration and of high intensity is preferably used.

Lamp structures and systems capable of providing high-intensity radiation in a very small lapse of time are well known per se.

Light sources with high radiation intensity and relatively short exposure time are the' so-called flash lamps and more particularly the discharge lamps containing an inert gas.

In the present invention good results are obtained with a xenon gas discharge lamp, which can supply an energy of 300-3000 watt. sec. in a time interval of to 10* seconds. More details about a copying apparatus containing such a discharge lamp can be found in Belgian patent specification 664,868. The intensity of emitted light is high in the infra-red and particularly high in the regions of the visible spectrum. Temperatures up to 400 C. can be easily obtained in the radiation absorbing substances by applying high intensity flash exposure.

It is possible to employ a number of flash tubes operating simultaneously or, in order to obtain a suitable imagedifferentiation, by flashing a single tube at suitable intervals. Reflectors and other optical components may be included to provide irradiation of maximum uniformity.

As illustrated by one of the examples hereinafter, which examples illustrate the present invention without limiting it thereto, it is also possible to produce according to the invention, more particularly according to the transfer technique set forth herein, multiple prints from one master only, which master has been formed by imagewise heating a recording material as defined herein.

While emphasis has been placed on the recording of electromagnetic radiation patterns it is to be understood that the invention includes the recording of heat patterns heat of which is absorbed in the thermo-sensitive element or layer, and that it is possible to form a heatabsorbing image in the recording material itself eg if this material is provided with a light-sensitive silver halide layer or a layer in which a silver-containing image can be formed by diffusion transfer.

The following examples illustrate the present invention Example 1 To a cellulose triacetate support a heat-sensitive coating is applied, which coating is prepared as follows:

10 g. of powdered cellulose acetobutyrate (D.S. acetate 2.04, butyrate 0.71) is mixed for 1 h. in a ball-mill with 0.5 g. of carbon black. To the mixed composition 300 ccs. of acetone are added and thereafter milling is continued for another /2 h. To the suspension obtained a solution of 1 g. of thioacetamide in 99 ccs. of acetone is added. The whole composition is coated in such a way that after drying the coating possesses an optical density, measured in transmission, of 0.44.

As diagrammatically illustrated in the accompanying FIG. 1 the heat-sensitive material 39 is laid with its v heat-sensitive layer 41 on a graphic opaque original 42,

which possesses light-absorbing image markings and lightrefiecting back-ground. No intense pressure is applied so that there is no real thermal contact of the light-absorbing image markings with the heat-sensitive coating. The transparent cellulose triacetate support 40 is directed towards a flash-exposure lamp 43 containing xenon gas. The electronic flash produces a light-intensity of 1600 watt. sec.

After flash-exposure the heat-sensitive material is brought into contact with a receiving paper and led between a pair of rollers as illustrated in FIG. 2. The exposed heat-sensitive material 39, and the receiving material 36 are pressed together between the

rollers

37 and 38, the former roller being heated to a temperature of 130 C.

After separating both elements a legible, pink positive print of the original is obtained on the receiving material. The latter material is prepared as follows:

To a paper support weighing g. per sq. m. the following composition is applied pro rata of 12.5 sq. in. per kg.:

Ethylcellulose having a substitution degree of 2.45 I

of ethyl groups g 30 Nickel stearate g 10 Amyl acetate ccs 970 Once the coating is dry, the receiving paper is ready for use.

Example 2 Example 1 is repeated with the difference, however, that in the heat-sensitive layer the amount of thioacetamide is replaced by a same amount of oxalic acid.

As receiving material a paper sheet is used, which has imbibed the following solution and subsequently dried:

Sodium sulphite g 20 Fuchsine g 50 Water ccs 580 A legible, positive, pink print of the original is obtained on the receiving paper.

Example 3 Example 4 Example 1 is repeated with the difference, however, that in the heat-sensitive layer the amount of thioacetamide is replaced by a same amount of p-phenylenediamine.

As receiving material is used a paper support of 90 g. per sq. m. onto which the following suspension is coated pro rata of 12.5 sq. m. per kg.:

Ethylcellulose having a substitution degree of 2.45

of ethyl groups g 20 Silver stearate g 10 Acetone ccs 970 A legible, positive, brown print of the original is obtained on the receiving material.

Example To a poly(ethylene terephthalate) support the following heat-sensitive coating is applied:

Cellulose acetobutyrate (DS acetate:2.1, butyrate:

0.75) g Carbon black g 0.5 N-nitroso-diphenylamine g 1 Acetone ccs 489 This heat-sensitive coating has an optical density, measured in transmission, of 0.61.

The receiving material is prepared by coating a paper of 90 g. per sq. m., pro rata of 13.5 sq. to. per kg., with the following composition:

Ethylcellulose having a substitution degree of 2.45

of ethyl groups g 20 Gallic acid g 10 Acetone ccs.. 970

When proceeding as described in Example 1, a legible, positive, brown-grey print of the original is obtained on the receiving material.

Example 6 Example 5 is repeated with the difference, however, that the amount of N-nitroso-diphenylamine is replaced by a same amount of tert. butyl-pyrogallol and that the amount of gallic acid in the receiving material is replaced by a same amount of iron(II) stearate.

A legible, positive, purple-grey print of the original is obtained.

Example 7 Example 5 is repeated with the ditference, however, that the amount of N-nitroso-diphenylamine is replaced by a same amount of phloroglucinol and that the amount of gallic acid in the receiving material is replaced by a same amount of pdiethylaminobenzene diazonium tetra fiuoroborate.

A legible, positive, brown-grey print of the original is obtained.

Example 8 Example 5 is repeated with the difierence, however, that the amount of N-nitroso-diphenylamine is replaced by ,a same amount of 4-methoxy-l-naphthol and that the material described as such in Example 4 is used as receiving material.

A legible, positive, green print of the original is obtained.

If the carbon black is excluded from the recording material, no image-differentiation is obtained on the receiving material. The receiving material becomes uniformly green coloured. If the carbon black in the recording material is replaced by 0.5 cc. of a 10% ethanolic solution of erythrosine, a known optical sensitizing dye, no imagedifferentiation can be obtained also, even not by increasing the added amount of sensitizing solution to 5 cos.

Example 10 Example 5 is repeated with the difierence, however, that the amount of N-nitroso-diphenylamine is replaced by a same amount of p-phenylenedithiourea and that a paper as described in Example 4 is used as receiving material. After having been dried, the recording material possesses an optical density, measured in transmission, of 0.29.

A legible, positive, brown print of the original is obtained.

Example 11 Example 5 is repeated with the ditference, however, that the amount of N-nitroso-diphenylamine is replaced by a same amount of 1,3-diphenyl-triazene and that the amount of gallic acid in the receiving paper is replaced by a same amount of 3-hydroxy-N-2naphthyl-2-naphthamide.

A legible, positive, orange-red print of the original is obtained.

A glassine-type paper weighing 60 g. per sq. m. is coated with a heat-sensitive layer from the following composition:

Cellulose acetobutyrate (DS acetatezll, butyrate:

0.75 g 10 Carbon black g 0.5 Tetrachloroquinone g 1 Acetone cs..- 489 Ethylcellulose having a substitution degree of 2.45

of ethyl groups g 20 4-metl1oxy-1-naphthol g 10 Acetone 970 A legible, positive, blue print of the original is obtained when proceeding as described in Example 1.

Example 13 To a poly(ethy1ene terephthalate) support a heat-sensitive coating is applied from the following composition:

Cellulose acetobutyrate (DS acetate:2. 04, butyrate:

0.71) g 10 Carbon black g 0.5 Dithiooxamide g 0.5 Acetone ccs 489 After having been dried the heat-sensitive material possesses an optical density, measured in transmission, of 0.54.

As receiving material a paper of g. per sq. m. is used onto which the following suspension is coated:

Ethyl-cellulose having a substitution degree of 2.45

of ethyl groups 2 20 Silver behenate v g 10 Amyl acetate ccs... 970

The suspension is coated in such a Way that an amount of silver behenate corresponding to 0.15 of silver is present per sq. m.

A legible, positive, brown print of the original is obtained when proceeding as described in Example 1.-

Example 14 Example 13 is repeated with the difference, however; that the amount of carbon black in the heat-sensitive ma: terial is replaced by a same amount of finely divided nickel sulphide.

A legible, positive, brown print of the original is obtained.

Example 15 Example 13 is repeated with the difference, however, that the amount of carbon black in the heat-sensitive material is replaced by a same amount of Indigo Blue (0.1. 73,000).

A legible, positive, brown print of the original is obtained on the receiving material.

1 1 Example 16 Example 13 is repeated with the difference, however, that the amount of dithiooxamine in the heat-sensitive material is replaced by a same amount of tert.-butylpyrocatechol.

Example 17 Example 13 is repeated with the difference, however, that the amount of dithiooxamide in the heat-sensitive material is replaced by a same amount of 1-phenyl-3- pyrazolidinone. By repeating the transfer step five times, each time with another image receiving blank, five sharp prints of the original can be obtained.

Example 18 A cellulose triacetate support, provided with a subbing layer for a hydrophilic colloid layer, is coated with a heat-sensitive layer from the following composition:

Poly(vinyl alcohol) g 30 Dimethylolurea g 20 p-Toluenesulphonic acid g Aqueous dispersion containing per 100 ccs. 0.5 g. of

black silver and 3.4 g. of gelatin ccs 120 5% ethanolic solution of tert.-butylpyrocatechol ccs 11% aqueous solution of saponin ccs 30 Water to ccs 1000 Example 19 Example 1 is repeated with the difference, however, that the heat-sensitive layer is exposed by transmission through a silver image transparency.

What I claim is:

1. In a method of reproducing information using a color-forming reaction system comprising two reactants adapted to react to produce a colored reaction product, the improvement which comprises exposing a heat-sensitive recording material including a heat-sensitive layer uniformly containing a color-forming reactant which is affected by heat of sufiicient intensity and is selected from the group consisting of compounds which are destroyed by heat, compounds which are blocked in reactivity by heat, and compounds which are removed by heat, to a heat image of the information to be reproduced of sufficient intensity to affect said reactant in the heated areas; bringing the heat-sensitive layer of said exposed heatsensitive material into effective contact with a copy material having the other of said color-forming reactants uniformly distributed thereon; and transferring at a temperature below that at which said first reactant is affected at least a portion of said first reactant from the unexposed and unheated areas of said heat-sensitive material to said copy material, the transferred first reactant reacting with the second reactant to produce on the copy sheet a colored image corresponding to the unexposed areas of said heatsensitive material.

2. The process of claim 1 wherein said heat-sensitive material while the heat-sensitive layer thereof is in effective contact with copy material is subjected to heat below the intensity at which said first reactant is effected to facilitate transfer of said first reactant to said copy material.

3. The process of claim 1 wherein said heat-sensitive layer includes a binding agent adapted to soften upon heating a stratum of said layer containing said first reactant is bodily transferred to said copy material to produce said color-forming reaction.

4. The process of claim 1 wherein said heat-sensitive material includes in heat-conductive relation to said heatsensitive layer heat-absorptive material uniformly distributed thereover.

5. The process of claim 1 wherein said heat-absorptive material and said first reactant are contained in a common layer.

6. The process of claim 1 wherein said heat-sensitive layer includes in heat conductive relation to said heatsensitive layer a vmaterial adapted to absorb and convert electromagnetic radiation into heat and said heat-sensitive material is exposed to an image of said radiation.

7. The process of claim 6 wherein said radiation absorbing and converting material and said first reactant are contained in a common layer.

8. The process of claim 6 wherein said heat-sensitive material is exposed to a high intensity radiation source emitting infra-red and visible radiation within an interval of not more than about sec. of sufficient intensity to heat the exposed areas of said heat-sensitive layer to render the first reactant contained therein non-reactive.

9. The process according to claim 6 wherein the heatsensitive layer contains a reactive compound selected from the group consisting of 1-phenyl-3-pyrazolidinone, 1,3- diphenyltriazene, tetrachloroquinone and 4-methoxy-lnaphthol.

10. The process of claim 9 wherein said second reactant on said copy sheet is a reducible silver salt.

References Cited UNITED STATES PATENTS 2,916,395 12/1959 Owen 11736.8 2,936,247 5/1960 Francis et al. 11736.1 2,992,121 7/1961 Francis et al 11736.1 3,210,544 10/1965 Marx et al 25065.1 3,223,838 12/1965 Hoshino et a1 250-651 3,238,047 3/1966 Murray et al 1l7--36.8 3,262,386 7/1966 Gordon 11736.8

MURRAY KATZ, Primary Examiner U.S. Cl. X.R.