US2897090A - Heat-sensitive copying paper - Google Patents

Description

y 1959 M. VAN DAM 2,897,090

HEAFSENSITIVE COPYING PAPER Filed April 11, 1957 v SOURCE OF RADIANT ENERGY \LlGHT-TRANSMITTING BASE HEAT-SENSITIVE COATING HEAT- SENSITIVE COPY MEDIUM FIG. 2.

I BASE ORIGINAL TO BE COPIED\ HEAT-SENSITIVE COATIN INVENTOR MAX VAN DAM LIGHT-TRANSMITTING BY ATTONEY HEAT-SENSITIVE COPYING PAPER Max Van Dam, Newton, NJ., assignor to Anken Chemical & Film Corporation, Newton, NJ.

' Application April 11, 1957, Serial No. 652,103

12 Claims. (Cl. 117-36) This invention relates to an improved heat-sensitive duplicating paper useful in preparing copies of printed matter or the like.

More specifically, this invention is concerned with heat-sensitive coating and coated sheet materials designed for preparing copies of printed matter or other graphic subject matter by exposure to high intensity irradiation and without subsequent developing or fixing operations.

Heat-sensitive coatings of this type, for preparing copies by direct exposure to high intensity irradiation without further treatment, are known, and several have been described, as in Miller and Clark, US. Patents 2,663,654, issued December 22, 1953, and 2,710,263, issued June 7, 1955; also Miller, US. Patent 2,740,896, issued April 3, 1956.

Significant limitations or disadvantages exist in the coatings for this purpose heretofore described however. Perhaps the most important of these is the lack of black and white contrast in copies made with these coatings. In most instances, the white is not white and the black not black. Frequently, the copying paper shows a butt background rather than white; and by virtue of the components used, a violet or blue image results instead of a neutral black. While heat-sensitive coatings with a white background are known, these produce an image which is most often dark brownish rather than black. True black and white copies have not been achieved.

Lack of sharp outline in black and white copies is also encountered in these previously described coatings. The boundary between the light background and the image is insufiiciently distinct in the copies resulting from them; a spreading or bleeding effect occurs; the copied image thus is unsharp or blurred.

Another major limitation of prior coatings is the narrow range of exposure conditions which will produce a satisfactory readable copy. Exposure to the optimum quantity of radiant energy may give reasonably acceptable results; but minor variations in the amount of irradiation give poor or unreadable copies. Underexpo sure to a relatively small degree produces too light a copy with insufficient contrast; overexposure to the same extent produces a copy with too dark a background.

A still further drawback to previously proposed coatings is that their components are so reactive and unstable toward each other that they must be ground or mixed separately, and in many instances, even applied to the sheet material as separate multiple coatings.

Still another drawback is the sensitivity of prior coatings to impurities such as small particles of chemical mat'erials and coarse dust. Such impurities show up as dark spots on the copy.

It is, therefore, an object of my invention to provide novel and useful compositions as coatings for copying paper which can produce neutral black and white copies.

Another objectof my invention is to provide compositionsrof a heat-sensitive material which will produce 2,897,090 Patented July 28, 1959 varied quantities of radiant energy.

Another object of my invention is to provide compositions of a heat-sensitive coating which will afiord copies sharp and clear, with ditsinct boundaries between the image and the background.

Still another object of my invention is to provide compositions which can be ground and mixed in one operation, and applied to the sheet material as a single coating.

A further object is the provision of heat-sensitive copying paper which is not oversensitive to impurities.

In conventional photography, the black image and the gray tones consist of metallic silver, reduced to the metal state from silver salts by the action of light and, of course, a suitable developer. The present invention is based on the discovery that under certain conditions black and neutral gray tones can be formed of metallic bismuth, suitably reduced to the metal state from bismuth salts. The requisite conditions are similar to those for the well-known reaction in aqueous alkaline solution whereby a bismuth salt can be reduced by sodium stannite to metallic bismuth.

In place of sodium stannite or other tin salt and an alkali hydroxide, which are unstable and impractical (sodium stannite forms stannate in air, and the hydroxide changes into carbonate), this invention makes primary use of derivatives of tin and organic alkaline compounds.

Bismuth is the key ingredient in this process, as silver is the key ingredient in photographic processes. The starting point is a bismuth salt and the process reduces it to metallic bismuth. Reduction takes place only in the presence of heat.

The required ingredients for a coating composition made in accordance with this invention are the follow- (l) A bismuth salt.

(2) A reducing agent. (3) A suitable medium. (4) A reaction regulator. (5) A binder (optional).

organic reducing agents may also be used, such as so-' dium hydrosulfite. Suitable organic tin derivatives are piperidine-tin chloride, semicarbaZide-tin sulfate, diphenylamine-tin chloride, methylamine-tin sulfate, aniline-tin sulfate, tin oxalate, tin tartrate, tin citrate, tin glycolate, and tin formate. These organic tin derivatives are illustrative of the various derivatives of this nature which have beenmade from semicarbazide, hydrazine, pyridine, aniline, methylamine, trie'thylarnine, triethanolamine, triisopropanolamine, piperidine, di phenylamine.

(3) A suitable medium: An alkaline medium, preferably organic, is preferred and suitable compounds are: semicarbazide, heterocyclic base and their derivatives such as amino-pyridine amines and amino derivatives, e.g. ethanolamines. Liquid alkaline substances can be used, preferably by converting them into new solid compounds through addition or condensation with weakly acid-reacting compounds. As liquid compounds may be used: Methylamine, dimethylamine, aniline, pyridine,

3 quinoline, hydrazine, triethylamine, triethanolamine, piperidine. They may be combined with: Ox-alic acid, tartaric acid, salicylic acid, benzoic acid.

.(4) Reaction'regulator: Regulators may be used to control the spread of the reaction and hence the sensitiyity or range of the coating to difierent amounts of radiant energy. As regulators, low-melting materials are used, preferably but not necessarily organic alkaline compounds. Suitable compounds for this purpose have been found to be benzylthiocyanate, chlorophenol, cinnamyl alcohol, o-cresol, diphenylamine, hexadecanol, exad y m p-t luidine, riph nyl P o p -vani lin, amino diphenylamine, p-hydroxy diphenylamine and phenyl diethanolamine. The dry ingredients of the mixture do not react quickly and these last listed materials are used to lower the melting point.

(5) Binder: A suitable binder in solution, and coating modifiers such as plasticizers, softeners, etc., may be used, Typical binders suitable for the purposes of this invention are the following: cellulose acetate, cellulose acetobutyrate, cellulose nitrate, ethyl cellulose, rubber nd h na ub e and hyl hvr roxy thyl lulose.

As has above been indicated, the key element in the entire process is bismuth but since we start with-a bismuth compound, it is necessary to utilize a reducing agent. Since the reaction will take place best in a suitable medium, the medium is also provided. Nonetheless, since the reaction may also take place without such medium, the latter is employed solely to expedite and facilitate the reaction. By the same token, a regulator is also used to control the reaction in order to provide sharply defined results but in the absence offsuch regulater, the reaction would still take place and with good results, falling short,-however, of the excellent results attained with the use of a regulator. The use of a binder is not essential and when used a small amount suflices. The binder helps to prevent setting of the materials during the coating process and keeps them in suspension. It also provides better adhesion to the paper.

It will be apparent from the foregoing, that the two key ingredients of the present invention are a bismuth compound and a reducing agent. But the other three ingredients are used to improve the process and for improved results. Aside from the fact that these three ingredients are not absolutely essential in the reaction, there may also be overlapping which would reduce their number without loss of their respective functions. For example, the alkaline medium and the regulator may overlap in that the regulator is preferably an organic alkaline compound. Consequently, it would not only perform the function of controlling the reaction but it would also supply the alkaline medium in which the reaction would take place.

Compositions prepared in accordance with this invention may be applied as a coating to paper, film and other light-transmitting material, either transparent or translucent, and other sheet materials may be used providing that they are transparent to heat. The result is a heatsensitive copy-medium. The invention is illustrated in the accompanying drawing, in which:

Fig. 1 shows the manner of use of a heat-sensitive copy-medium made in accordance with this invention, sald copy-medium and the original to be copied being shown in section and the radiations from the heat source bemg represented by means of interrupted lines.

Fig. 2 1s a plan View of said heat-sensitive copymediurn superimposed upon the original to be copied, said v ew following the exposure of said copy-medium and said original to radiant energy, one corner of said copy-medium being folded over to show the result of such exposure.

Referring now to Fig, 1 of the drawing, it will be observed that in the use of a heatfsensitive copysmedium 1n accordance with this invention, said copy-medium is superimposed upon and in contact with the original which is to be copied. In the drawing, the heat-sensitive copy-medium is shown to consist of a light-transmitting I base, such as a sheet of light-transmitting paper, covered with a heat-sensitive coating prepared in accordance with this invention.

The heat-sensitive copy-medium is superimposed upon and in contact with the original to be copied, said original being shown in the drawing as a sheet of paper or the like having printed, typewritten or written material applied thereto and indicated by the interrupted lines thereon.

Radiant energy is then applied through said heat-sensitive copy-medium to the original to be copied. This is done by the use of any suitable source of radiant energy, as for example an infra-red lamp as shown in Fig. l of the drawing. The interrupted lines between said infrared lamp and said heat-sensitive copy-medium are intended to represent the radiations which emanate from said infra-red lamp.

More heat is generated by said radiant energy in the printed or other written matter on the original to be copied than in the blank spaces surrounding said printed or written matter, such heat being .suflicient to cause the chemical reaction in the heat-sensitive coating herein described. The bismuth compound is reduced .to metallic bismuth in the precise areas on the heat-sensitive copymedium which correspond to the graphic material on the original to be copied, and the result is that an identical copy of said graphic material is formed on the heatsensitive copy-medium and indicated in the drawing by the interrupted lines on the heat-sensitive Opyrmedium shown in Fig. 2.

The following coating compositions are given as specific examples illustrative of the invention and they are. not to be considered restrictive or limitative of its scope:

After mixing, the mixture was uniformly spread bymeans of a doctor-blade onto a thin transparent paper and dried at room temperature.

The resulting sheet is suitable for use as a heat-sensitive copying paper.

The following mixture was ball milled and coated on light transmitting paper;

h following mi ture s ba -milled and sea e 1. light transmitting paper:

G am Bismuth subsalicylate 36 Tin hydroxide v 20 Tri-isopropanolamine 19 Polyvinylbutyral V 25 Semicarbazide 2-5 Toluene a 30 The following mixture was ball-milled and coated on translucent paper:

Bismuth lactate g 36 Semicarbazide-tin chloride ..g 34 Semicarbazide g 15 Hydrazine salicylate g 20 Ethyl hydroxyethyl cellulose g.. 1 Toluene 7 l 50 Ligroine ml. 400

The following mixture was ball-milled and coated on transparent paper:

Grams Bismuth subnitrate 2930 Triethylamine-tin chloride 2910 Semicarbazide 2500 Ethyl paratoluene sulfonate 1000 Cellulose nitrate 200 Acetone 2300 It will be noted that organic tin derivatives are used in the foregoing examples. The following procedures may be used in producing these derivatives:

A. Preparation of piperia'ine-tin chloride To a solution of 190 g. of anhydrous tin chloride in 500 ml. of water was added 85 g. of piperidine.

The white precipitate which formed was immediately filtered olf, washed with water, methanol and dried.

Yield: 81 g. of piperidine-tin chloride.

B. Preparation of semicarbazide-tin sulfate 150 g. of semicarbazide dissolved in 230 ml. of water was added to a solution of 215 g. of anhydrous tin sulfate in 230 ml. of water.

The mixture warmed spontaneously and precip tate was formed. After standing for 2 hours the precipitate was filtered 'ofi, washed with water, then with methanol and dried. I

Yield: g. of semicarbazide-tin sulfate in the form of a white powder.

C. Preparation of diphenylamine-tin chloride A solution of 338 g. of diphenylamine in 50 ml. of methanol was added to a solution of 190 g. of anhydrous tin chloride in 500 ml. of water; immediately a precipitate was formed. One liter of methanol was added to the slurry. The precipitate was filtered, washed with water and methanol.

Yield: 500 g. of diphenylamine-tin chloride in the form of a white. powder. 7

D. Preparation of methylamine-tin sulfate To a solution of 215 g. of anhydrous tin sulfate in 500 ml. of water was added 120 g. of a 25% solution of methylamine in water. The white precipitation which formed was immediately filtered oif, washed with water, then with methanol and dried.

Yield: 60 g. of methylamine-tin sulfate in the form of a white powder.

E. Preparation of aniline-tin sulfate To a solution of 107 g. of anhydrous tin sulfate in 250 F. Preparation of hydrazine tarzrate To a solution of 1 50 g. of tartaric acid in 500 ml. of

methanol was added 50 g. of hydrazine monohydrate.

The white precipitate which was formed immediately,

was filtered, washed with methanol and dried.

Yield: g. of hydrazine tartrate.

G. Preparation of hydrazine salicylate To a slurry of 151 g. of salicylic acid in 200 m1. of .methanol was added: 67 g. of hydrazine monohydrate.

The mixture warmed spontaneously and the salicylic acid.

went into solution. The methanol was evaporated on a steambath. After cooling the residue solidified:

Yield: g. of hydrazine salicylate.

The foregoing is illustrative of the basic principles of this invention and it will be understood that all of the examples above set forth are merely illustrative of the invention and not limitative thereof and that modifications and variations of these examples, as well as other examples involving other procedures and formulae producing the same or similar results may also be employed within the broad spirit of the invention and the broad scope of the claims.

I claim:

1. A heat-sensitive copying sheet for producing copies of printed or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a tin derivative reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth.

2. A heat-sensitive copying sheet for producing copies of printed or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth, said bismuth compound being a bismuth salt which is combined with a tin derivative reducing agent in an organic alkaline medium.

3. A heat-sensitive copying sheet for producing copies of printed or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and -a reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth, said bismuth compound being a bismuth salt which is 'combined with a tin derivative reducing agent in an alkaline medium and held together by a binder.

4. A heat-sensitive copying sheet for producing copies of printed or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth, said bismuth compound being a bismuth salt selected from the group consisting of the bismuth salts of inorganic and organic acids and being combined with a reducing agent selected from the group consisting of inorganic and organic tin derivatives.

5. A heat-sensitive copying sheet for producing copies of printed or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said bismuth compound in the presrubber and ethyl hydroxyethyl cellulose.

6. A heat-sensitive copyingsheet for producing copies of printed or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combinationof abismuth compound and-a reducing agent capable of reacting with said bismuth compound in the presence of heat :to produce metallic bismuth, the hismuth compound being a bismuth salt which is combined with a tin derivative reducing agent and a reaction regulator'in an alkaline medium and ;-held togetherzby a binder, said reaction regulator being a low melting material selected from the @group consisting of henzylthiocyanate, chlorophenol, cinnamyl alcohol, -o-cresol, diphenylarnine, hexadecanol, hexade'cylamine, .p-toluidine, triphenyl phosphate, o-vanillin, .arnino diethanolamine.

7. A heat-sensitive copying sheet for producing copies of printedor graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth, said bismuth compound consisting of approximately 2690 parts by weight of bismuth borate, which 'is combined with the following ingredients in the following approximate parts by weight for applying to said copying sheet: 2500 parts semicarbazide, 2150 :parts stannous sulfate anhydrous, 1200 parts diethano'lamine, 200 parts cellulose acetate, 300 parts methanol, 1200 parts acetone and 500 parts dichlorethane.

:8. A heat-sensitive copying sheet forproducing copies of printed or graphic subject matter byexposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth, the bismuth compound consisting of approximately 2610 parts byweight of bismuth oxychloride, which .is combined with the following ingredients in the following approximate parts by weight for applying to said copying sheet: 2670 parts tin tartrate, 2000 parts semicarbazide, 2000 parts diphenylamine, 1000 parts di iso propanolamine, parts ethyl cellulose and 2250 parts toluene.

9. A heat-sensitive copying sheet for producing copies of printed or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said'bismuth compound in the presence of heat to produce metallic bismuth, said bismuth compound consisting of approximately 3600 parts by weight of bismuth subsalicylate, which is com- -.8 bined with the following ingredients in the following approximate parts by weight for applying to said copying sheet: 2000 parts tin hydroxide, 1900 parts tri=isop ropanolamine, 250,,parts polyvinylbutyral, 2500 .parts semicarbazide and 2250 parts toluene.

10. A heat-sensitive copying sheet for producing copies of printed .or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant energy, said copying sheet having applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said bismuth compound in the presence of heat'to produce metallic bismuth, said bismuth compound consisting of :approximately .2930 parts by weight of bismuth subnitrate, which 'is combined with the following ingredients in the following approximate parts by weight for applyingto said copying sheet: 2910 parts triethylamine tin chloride, 2500 iparts semicarbazide, 1000 parts ethylparatoluene sulfona'te, 200 parts cellulose nitrate and 2300 'partsaceton'e.

11. A heat-sensitive copying sheet for producingicopies of printed or graphic subject matter by exposure of said sheet, in contact with saidsubject matter, to radiant energy, said copying sheet Ihaving applied thereto the combination of a bismuth compound and a reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth, said bismuth compound being bismuth lactate, which is combined with the following ingredients ;in the approximate proportions given tor-applying to said copyingjsheet: 36 g. bismuth lactate, 34 g. semicarbazide-tin chloride, 15 g. semicarbazide, 20 g. hydrazine salicylate, 1 g. -ethyl hydroxyethyl cellulose, 50 m1. toluene and 400 ml. ligroine.

.12. A heat-sensitive copying sheet 'for producing copies of printed :or graphic subject matter by exposure of said sheet, in contact with said subject matter, to radiant :energy, said copying sheet having applied thereto the combination of "a bismuth compound and :a reducing agent capable of reacting with said bismuth compound in the presence of heat to produce metallic bismuth, said bismuth compound being a bismuth .salt whichiis combined with a tin derivative reducing agent inan alkaline medium selected from the group consisting of semicarbazide, heterocyclic bases, and the aminoand ethanolamino 'deiivatives of said 'heterocyclic bas'e's.

References Cited in the file of this patent UNITED STATES PATENTS 2,092,566 Wright Sept. 7, 1937 2,663,653 Zimmerman Dec. 22, 1953 2,663,656 Miller Dec. 22, 1953 2,740,826 Miller ...Apr. 3, 1956 2,749,253 Shoemaker June 5, 1956

Claims (1)

1. A HEAT-SENSITIVE COPYING SHEET FOR PRODUCING COPIES OF PRINTED OR GRAPHIC SUBJECT MATTER BY EXPOSURE OF SAID SHEET, IN CONTACT WITH SAID SUBJECT MATTER, TO RADIANT ENERGY, SAID COPYING SHEET HAVING APPLIED THERETO THE COMBINATION OF A BISMUTH COMPOUND AND A TIN DERIVATIVE REDUCING AGENT CAPABLE OF REACTING WITH SAID BISMUTH COMPOUND IN THE PRESENCE OF HEAT TO PRODUCE METALLIC BISMUTH.

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