US 3100703 A
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United States Patent 3,100,703 PHOTOGRAPHIC PROCESS UTILIZING CYANINE DYE BASES Robert H. Sprague, Chagrin Falls, Harry L. Fichter, Jr., Lakewood, and William P. Hamilton, Cleveland, Ohio, assignors to Horizons Incorporated, a corporation of New Jersey No Drawing. Filed Mar. 13, 1961, Ser. No. 95,031 15 Claims. (Cl. 96-33) This invention relates to a photographic process capable of producing colored photographic prints. The process is suitable for producing prints of a specific single color as well as full-color photographic prints involving suitable utilization of the primary colors of the visible spectrum. A further aspect of the invention is the availability of a photosystem suitable for the production of photoresists, lithographic printing surfaces, and the like.
In copending applications filed by Eugene Wainer including the following:
Serial No. 787,112, filed January 16, 1959, and issued July 3, 1962, as US. Patent 3,042,515
Serial No. 841,459, filed September 22, 1959 Serial No. 841,460, filed September 22, 1959, and issued July 3, 19.62, as US. Patent 3,042,516
Serial No. 842,569, filed September 28, 1959, and issued July 3, 1962 as US. Patent 3,042,517
Serial No. 1,161, filed January 8, 1960, and issued July 3, 1962, as US. Patent 3,042,518
Serial No. 1,162, filed January 8, 1960, and issued July 3, 1962, as US. Patent 3,042,519 r Serial No. 22,703, filed April 18, 1960, and issued October 2, 1962, as US. Patent 3,056,673, and
Serial No. 23,130, filed April 19, 1960, and issued July 24, 1962, as US. Patent 3,046,125 a variety of photosystems are described, utilizing in the main combinations of various aromatic amines, organic compounds containing halogens, and plastic bases suitably disposed on an applicable substrate. In said copending applications, exposure to light alone or, variously, exposure to light followed by heat treatment is sufi'icient to produce colored print-out image at high speeds from an originally substantially colorless product. The assumption was made that the mechanism of operation of the photochemical reaction in these photosystems involved the formation of tree radicals, based on the photolytic dissociation of the organic halogen compound as the result of light absorption by such organic halogen compounds. As a consequence, the spectral sensitivity of such previously described reactions was assumed to be dependent upon the spectral range in which this organic halogen compound would adsorb light and break up into free radicals.
In our co-pending application Serial No. 42,233 (filed July 12, 1960), issued June 25, 1963, as United States Patent 3,095,303, We described the use of styryl dye bases and higher vinylene homologs thereof in combination with certain classes of organic halogen compounds to provide a photosensitive composition which was sensitive to visible light.
We have now found that cyanine dye bases may likewise be used in combination with similar organic halogen compounds to provide a photosensitive composition sensitive to visible light. Furthermore, many of the cyanine dye bases have the advantage of imparting higher photographic speed to the photosensitive mixture, particularly in the red end of the spectrum. The greater variety of structures available in the cyanine dye base series enables selection of compounds with high sensitivity in particular narrow areas of the visible spectrum, which is of great importance in color photographic applications.
Specifically, we have found that a family of weakly 3,100,703 Patented Aug. 13, 1963 ice 1 colored dyes or dye progenitors, belonging to the class of cyanine dye bases, are capable of producing intense colors of high brilliance with narrow spectral ranges of absorption when utilized as a photosystem in combination with suitable organic halogen-containing compounds. The variety of the colored cyanine-base type compounds is sufficiently broad to blanket the visible range with respect to their light-absorption qualities and also with respect to the nature of the color which can be produced as the result of exposure to light when utilized in combination with suitable organic halogen compounds. More important, however, as distinguished from the photosystems of the aforementioned Wainer applications, is the fact that through use of such dye bases a full range of sensitivity to the visible is available. In View of the broad variety of dye bases available'from the class indicated, it is thus possible in the present photosystem to expose a blue-sensitive variety to blue light to yield an intense yellow color, a green-sensitive variety to green light to produce a magenta color, a red-sensitive variety to red light to produce a cyan color, etc. The color of the developed image is thus complementary to the color of the exposing light, which is a necessary characteristic of a color negative material. The sharp cutting absorption, both of the progenitor and the color form produced as the result of exposure to light, is such that increments of absorption throughout the visible may be produced as desired for specialized efiects.
While we do not wish to be bound to any specific theory as to the reason for the ability to blanket the visible with respect to sensitivity and development of color, it appears that, either as a result of exposure to light or possibly simply as the result of mixture of the organic halogen-containing compound and the weakly colored dye, a complex is formed which requires less energy to raise it to an excited state to permit the desired photolytic reaction to take place than when such complexes do not form.
It has been pointed out that the dye progenitor is weakly colored and, as a result of exposure to light in the presence of the organic halogen compound, a brilliant, intense, sharp cutting color is obtained. Equally important as the foregoing is our finding that, 'as a result of exposure to light with or without subsequent development by heat, a sharp difference in solubility in certain solvents exists between unexposed and exposed areas. This finding is of exceptional importance in order to eliminate any residual color which may exist from the progenitor itself and which might mask the desired printout effects. More important than the elimination of such color-masking effects is the fact that such differences in solubility may be utilized for fixing and stabilization of the printed image. Equallyimportant is our finding that,
appears that the developed-out dye image .is ionic in character, exhibits hydrophilic properties, and tends to be insoluble in non-polar solvents; whereas the unexposed dye progenitor, even in the presence of the organic halogen-containing compound, is a covalent non-ionic compound, soluble in a variety of organic solvents, and tends to be hydrophobic in character. Such hydrophobic properties may be enhanced by placing the photosystem in a hydrophobic base. As a consequence, the system can be utilized as a foundation of photoetch purposes and as a means for producing a lithographic plate.
Solvents which may be utilized for the above described fixing and developing include ethers, esters, chlorinated solvents, benzene, toluene, \and the like. A diiierentiation is obtained even with water-compatible solvents such as acetone.
In general terms, therefore, our novel photosensitive system is utilized ina variety of ways. 'If it is desired to produce a single color of permanent nature as a result of a print-out reaction in the visible, a weakly colored cyanine dye base is chosen having absorption characteristics compatible with the source of light available in the visible. By virtue of its inherent color, the choice is simplified. This is combined with a suitable organic halogen-containing compound and placed on a suitable substrate. After exposure to light, a print-out image of intense brilliance is obtained, the unexposed portions remaining the original color. The development of color may be enhanced by a brief heating for between 1 and 10 seconds at approximately 85400" C. and preferably.
about 100* C. prior to solvent fixing. The developed print is then treated with a solvent, such as ether or benzene, which removes the undecomposed dye base, leaving only the developed image fixed to the substrate.
By utilizing multipacks, with an appropriate selection of color formers and exposure to the full spectral range of visible light, full-color prints may be obtained. Thus when utilizing multipacks, exposure of the film to a colored subject produces a negative image in colors complementary to the exposing light. After removal of the unexposed light-sensitive material by solvent extraction, a contact print through the negative on a second sheet of thesame sensitive film results in a positive image in the same colors as the original exposure. Removal of unexposed light-sensitive material by solvent extraction of the positive print gives a stable product.
Similarly, our color-sensitive material may be used to make positive prints from commercially available color-negative materials, either by'contact printing or by projection printing with an enlarger.
Full color prints may also be obtained by printing registered dot patterns of the combination of cyanine base and suitable organic halogen compounds on a white or transparent backing. By utilizing known printing techniques of high resolution, the various color progenitors may be placed sufficiently close to each other so that, as a result of exposure and fixing, a fullcolor rendition is obtained. Conversely, color separation negatives may be obtained by standard techniques utilizing simultaneous exposures in one-shot three-color cameras available commercially.
The invention may be utilized as a foundation for a lithographic plate by minor modifications of the foregoing procedure.
The process may be modified by placing the photosensitive system on a hydrophilic substrate, such as paper, and then washing out the developed dye image with water so as to expose the paper backing in these areas. In this case, the unexposed, undecomposedsystem is hydrophobic and the exposed portions are hydrophilic, even though no developed dye color remains in the hydrophilic areas. Washing out the developed image with water in this way does not remove either the unexposed cyanine dye base or the unreacted organic halogen compound or the complex which mayhave formed by combination of the two. It is therefore possible, after drying the washed sheet, to re-expose with a blanket exposure to light and cause development of the remaining lightsensitive material, giving a positive image which requires no fixing. Our new process is thus applicable to direct positive photocopy, capable of copying colored as well as black-and-white materials.
Thus, in general, the photosensitive systems of this invention comprise a light-sensitive coating composed of a mixture of a cyanine dye base with a halogen-containing source of photolytically producible free radicals, either coated on a substrate or suitably dispersed in a solution of a binder such as nitrocellulose, polystyrene, ethyl cellulose, poly-vinyl chloride, Saran, or the like, and subsequently coated on a substrate either as an adherent coating or as a non-adhering or strippable self-sustaining film.
The cyanine d=ye bases useful for the purposes of our invention are of several types, including those used commercially as supersensitizers in conventional silver halide photography. Although not themselves strong sensitizers, such bases impart increased sensitizing action to cyanine dyes when such combinations are employed in silver halide emulsions. In general cyanine dye bases are known corresponding to all the diiferent classes of cyanine dyes,'including symmetrical and unsymmetrical monomethine cyanines, carbocyanines, dicarbocyanines, tricarbocyanines, hemicyanines, pyrrolocy'anines and azacyanines. The cyanine dye bases may be regarded as de-quaternized cyanine dyes, as illustrated below for diethylthiacarbocyanin iodide (A) and the base (B) derived from it.
3,3'-diethy1thiacarb0cyanine iodide CzH5 2- (3-ethyl-2 3H) -beuzothiaz01y1idene propenylbenzothiazole Alternatively, cyanine dye bases are derived from heterocyclic. bases by a wide variety of reactions wellknown to those skilled in the ant. Typical heterocyclic bases useful in. such reactions are the following:
2-methylbenzothiazole 2-methylbenzoxazole Z-methylbenzimidazole Z-methylthiazoline Quinaildine Lepidine I-methylisoquinoline 2-methyl-ot-naphthothiazole Z-methyl-fi-naphthothiazole Alpha-picoline Gamma-picoline 3-meth'ylisoquinoline 2,4-dimethylthiazole 2-methyl-4-phenylthiazole Z-methylthiazole. 2.,3,3-trimethylindolenine 2,4.-dimethylselenazole 2-methylbenzoselenazole 2,4-dimethyloxazole 2-methyl-a-naphthoxazole Z-methyl-B-naphthoxazole 2-methyl-4,5,6,7-tetrahydrobenzothiazole 2-methy l-4,5,6,7-tetrahydrobenzoxazole Z-methyl-S,6,7,8-tetrahydro-4-cycloheptathiiazole Z-methyl-S,6-dihydro-4-cyclopentathiazole 2-methyi-6,7-dihydro-4-H-pyrano 4, 3D) thiazole Z-methyl-6,7-dihydro-4-H-th:iopyrano(4,3D)rthiazole 2metl1yl-5 6-dihydro-4-H-pyrano 3 ,2D thiazole Z-cyanomethylquinoline Z-cyanomethylbenzothiazole 4-cyanomethylquinolinc 2-cyanomethylbenzimidazole Z-cyanomethylpyridine 4-cyanomethyl-pyn'dine Cyanine bases useful in our novel photo process are characterized by the following general formulas:
' a member selected from the group consisting of hydrogen,
3,100,703 p i 5 s 4 6 wherein d and e each represents a positive integer of (G) from 1 to 2; n represents a positive integer of from 1 to s Q 4; R represents an organic radical selected from the group V consisting of talkyl, ar-alkyl and aryl groups; R represents /o=cH-H=oH cH= N ON -CN and a radical characterized by the general for mula, CH
' 1- -1 '4-[1-cyano-5- (3-methyl-2 3H -benzothiazo1ylidene) 1,3-pentadienyl] quinollne c= en-on), i=1 r D) I g is a positive integer of from 1 to 2 and Q, Z, and Z' s Q each represents the non-metallic atoms (C, S, Se, O and I N) necessary to complete a heter-ocyclic organic nucleus H I N containing from 5 to 6 atoms in the ring.
Cyanine dye bases characterized by the above general N formula may be symmetrical or unsymmetrical, of varyl fi g gg gg 223 i g g g gg z ggi figf gf gg 3;: 4-[(3-ethyl-2(3H)-beuzothiazo1yl1dene)methyl]quinoline depicted below. Azacyanine bases useful in our photoprocess may be (1) Symmetrical compounds: regarded as related to the cyanine dye bases by replace- (A) ment by nitrogenof one or more methine groups in the chain joining the two heterocyclic nuclei. They may be characterized by the following general formula:
2-[3-(1-ethy1-2(1H)-quino1ylidene)propenyllquinoline wherein d, e, n R, Q and Z each has the Same meaning S I as genenal Formula 1 above, and each L represents p a member selected from the groupconsisting of CH and O=CHC=OHC V N and may be the same or different, at least one L being H a nitrogen atom.
I Typical azacyanine bases are listed below: C2115 2- [2methyl-3- (3-ethyl-2 3H) -benzothiazoly1idene) -propenyl] s benzothiazole l orr 1 f H 4- [2- 3-ethy1-2 (3H) -benzothiazolylideneamino) vinyl] 4- (1-ethyl-2 (1H) -quin0ly1idene) methyl] quinoline quhmune @=OH-CH=CHOH=E@ =NU CIEHS N EQHS 2-[1-cyauo-5- (l-ethyl-Z lggiggiinnogylidene) -1,3-pentadienyl] 4- (1-etl1yl2(1H)-quin01ylideneamino)qulnoline (E) t (C) s s oeorr-oreon-oH=oH-oH orr-o t T E f v If N C 2H5 V V (3-ethy1-2 3H) -benzothiazolylidene) 2-quinoly1methylidene) 2-[7-(3-ethyl-2(3H)-benzothiaz0ly1idene)-1,3,5-heptatrieny1] zine benzothiazole CzHn (3-ethyl-2 3H) -benzothiazo1ylldene) 2-benzothiazolylimino) I v hydrazine hy ra Unsymmetrical bases: 60 S\ (A) 0 t C=NN=NG l /o=on-cn=on \N/ l I? t C2115 2- [3- 3-ethyl-2 (3H) -benz0xazolylidene) propenyl] quinoline C2 5 CzHs t 4- [2-methy1-3- l-ethyl-Z 1H) -quinolylide11e) -propenyl] 4-[ (3-ethy1-2 (3H) -be11zoxazolylideue) -2-butenylldene] quinoline aminoquinoline aminoquiuoline A further class of bases useful in our photoprocess are those containing nitrogen in the chain, related :to the styryl dye bases and their vinylene homologs, and corresponding to the following general formula:
and N: and may be the same or diflerent, at least one L or L being a nitrogen atom, and Q represents the nonmetallic atoms necessary to complete a heterocyclic nucleus containing from 5 to 6 atoms in the ring;
Bases typical of thisclass include the following:
2- (p-dimethylaminobenzylidene) aminoquinoline N 2-[ (3-p-dimethylaminophelgl) -2- propenylideue] aminobenzozo e 4- (pdihrethylamlnophenylimlno) cyanomethylquinollue 4- (p-dimethylaminophenylazo) quinoline 4.- (5-p-dlmethylamino-2A-pentadlnylidene) aminopyridine ORGANIC HALOGEN COMPOUND ing of Cl, Br and I. Organic compounds we have found useful include:
Carbon tetrabromide Hexachloroethane Carb on tetrachloride Hexabromoethane Chloroform Benzotrichloride Bromoform Benzothibromide Pentabromoethane p-Nitrobenzotr-ibromide It is preferred'that the combination of cylanine dye base and organic halogen-containing compound be dispersed. in a film-forming binder such as any of those disclosed in the aforementioned Wainer applications.
I Suitable film-forming binder solutions inolude the following:
Ethyl cellulose in methyl alcohol Nitrocellulose in methyl alcohol or acetone Polystyrene in benzene Polyvinyl chloride in tetrahydrofuran Polyvinylidene copolymer in methyl ethyl ketone Cellulose acetate in acetone- Polyvinyl acetate in toluene plus acetone In addition, conventional plasticizers may be incorporated into the above solutions or, if desired, hydrocarbons I may be added as a diluent in the composition. Suitable hydrocarbon diluents, which appear to play no part in the photochemical reaction, include paraflinand isoparaflin-hydrocarbons, having the general formula, C H wherein n ranges from about 10 up to '70. When added to the system, it ispreferred that they be added in solution.
In the compositions of the present invention it is preferred to provide about 10 to parts by weight of the organic halogen-containing compound for each part by weight of cyanine d ye base, dispersed or dissolved in about 200 parts by weight" of a 10% solution of a filmforming plastic.
Having described our invention in general terms, the following examples are indicative of specific methods of practice and are to be construed as illustrative rather than as limitative of the invention.
Example 1 Fifty milligrams of 4 [5 (3 ethyl-2(3H)'-benzothiazolylidene)-l,3-pentadienyl] quinoline a color. Fixing was accomplished by extracting. the unreacted starting material with a brief wash in a solvent system consisting of three parts of ethyl acetate in seventeen parts toluene (3:17).
Example 2 Fifty milligrams of 4-[3-(3-ethyl-2(3H) -benzothiazolylidene) propenyl] quinoline and 2.8 grams of carbon tetrabromide were dissolved in l0 cc. of acetone and 6 cc.. ethyl acetate, then coated on clear transparent cellulose acetate film. Two-seconds exposure through a negative to a sunlamp or a photofiood lamp gave an excellent print-out image. The image color was blue. Fixing was achieved with the technique described in Example 1. When this mixture was coated on white opaque cellulose acetate and exposed on a Bausch and Lomb ZSO-Inillimeter grating monochromator, the time required to give a reflection density, of 1.0 was recorded. This mix showed 1.0 density in the time range of twenty to ninety seconds over the spectral range of 3900 A. and 6300 A. Peak sensitivity was noted at 4700 A., requiring only twenty seconds to given density 1.0.
Example 3 Twenty-five milligrams of 2-[3-(3-ethyl-2(3H)-benzoxazolylidene) propenyl] quinoline can were dissolved in 16 cc. of a 1% solution of ethyl cellulose in toluene and containing 1.4 g. of carbon tetrabromide. The mixture was coated on white opaque polyvinyl chloride sheets. The color of the coating was pink. A two-second exposure through a negative to a sunlamp' gave excellent print-out images. When a microfilm negative was projected onto the coating, using a standard 35- millimeter slide projector with a SOD-watt lamp and a distance sufficient to give a ten-diameter projection, an excellent print-out rendition of the negative was observed with a thirtysecond exposure. Fixing was accomplished in the manner described in Example 1.
Example 4 Fifty milligrams of (3-ethyl-2 3H) -benzoxazolylidene) ethylidene-di-2-benzothiazolylmethane N Q CsHs N Example 5 7 Twelve and one-half milligrams of 4-[(3-ethyl-2(3H)- benzoxazolylidene) propenyl] quinoline C2115 were dissolved in 8 cc. acetone containing 1.4 g. carbon tetrabromide, then coated on clear transparent cellulose acetate sheets. When exposed through a negative to a sunlamp for two seconds, these coatings gave direct printout images of good density. The color of the image was violet. Fixing was performed in the manner described in Example 1.
Example 6 Fifty milligrams of 2-[4-(3-ethyl-2(3H)-benzoxazolylidene) -2-butenylidene] -arninobenzothiazole color was brown. Fixing was accomplished by extracting the unreacted starting materials with a toluene wash. In a similar fashion, photosensitive coatings may be prepared, utilizing the following azacyanine dye bases:
(3ethyl-2 (3H) -benzothia.z0lylidene) (2-quinolylmethylidene) hydrazine The color of the image formed by exposure to light is reddish orange.
2- [6- 1-ethyl-2 1H) -quino1ylidene) -2,4-hexadienylidene] aminobenzothiazole i The color of the image formed by exposure to light is reddish orange.
Exa mple 7 To 5 cc. of a 1% solution of the cyanine dye base, 2-[ (3 ethyl-2( 3H) benzoxazolylidene) propenyl] -quinoline, in acetone was added 0.5 gram of carbon tetrabromide. This mixture was coated on a multilith master and exposed under a negative to two General Electric 2-75- watt sunlamps for one minute. An excellent image printed out. After swabbing the print with water, the master was mounted in the duplicating machine and the machine run in the usual manner. The water swa'bbed master picked up ink on the image area and transferred it to the receiving sheet with little or no ink in the background.
Example 8 A solution of 50 mg. of the cyanine dye base, 2- (3 ethyl-2(3H) -benzoxazolylidene)-propenyl] -quinoline, 2.8 g. of CBr and mg. of eicosane in 15 ml. of acetone was coated on a casein-surfaced paper sheet. This was exposed under a positive transparency to a photoflood lamp, giving a negative photocopy.- The sheet was swabbed with a weakly acid buffer solution which washed away the negative image, leaving the weakly colored cyanine dye base unchanged in the unexposed area. Reexposure to the photoflood lamp resulted in darkening of the previously unexposed area, giving a positive copy of the original transparency.
While not necessary for the purposes of our invention, the permanence and brilliance of the color images produced may be enhanced by the formation of lakes through treatment with metal salt solutions such as salts of copper, chromium, cobalt, phosphotungs-tic acid, phosphornolybdic acid, aluminum, and the like.
Example 9 Fifty. milligrams of 2-[(3-ethy1-2\(3H)-benzothiazo1ylidene) -ethylidene] -aminob enzothiazole were dissolved in 16 cc. of a 1% solution of ethyl cellulose in toluene, containing 2.8 grams of carbon tetrabromide and 1 cc. of methanol. The light-yellow mixture was coated on a polyvinyl chloride sheet. A twentysecond exposure through a negative to the ultraviolet of a sunlamp, or a thirty-second exposure to a photofloodlamp, gave excellent print-out images. The image color was brown. Fixing was achieved by extracting the unreaoted starting materials with a toluene wash.
Having now described our invention in accordance with the patent statutes, we claim:
1. A non-silver photosensitive composition which prints out a visible image directly and solely as a result of exposure to suitable radiation, said composition consisting essentialy of: a photolytically active organic halogen containing compound selected from the group consisting of alkyl and aralykyl compounds in which at least three halogen atoms are attached to a single carbon atom, said halogens being selected from the group consisting of Cl, Br, and I; and a cyanine dye base selected from the group represented by general Formulas I, -II, and III below,
wherein d and e each represents a positive integer of from 1 to 2; n represents a positive integer of from 1 to 4; R represents an organic radical selected from the group consisting of alkyl, 'aralkyl and aryl groups; R represents a member selected from the group consisting of hydrogen, CN and a radical characterized by the general formula,
I I) r ing as in general Formula I above, and each L represents a member selected from the group consisting of CH and N and maybe the same or ditfcrent, at least one L being a nitrogen atom;
group consisting of CH=,
' and -N= and at least one of L and L being a nitrogen atom, and Q represents the nonmetallic atoms necessary to complete a heterocy-clic nucleus containing from 5 to 6 atoms in the ring said halogen containing compound being present in an amount sufiicient to sensitize said dye base.
2. The composition of claim 1 dispersed in a filmforming plastic.
3. The composition of claim 2 as a self-supporting film.
4. An article consisting of the composition of claim 2 coated on a solid substrate.
5. The composition of claim 1 wherein the organic halogen-containing compound CB1 6. The composition of claim 1 wherein the proportion of the organic halogen-containing compound relative to the cyanine dye base is between about 10' and parts "by weight of organic halogen-containing compound.
7. The composition of claim 1 wherein the cyanine dye base is 4- [5-( 3-ethyl-2 3H -benzothiazolylidene) -1, 3- pen-tadienyl] quinoline.
8. A multilayer pack for producing colored photographic prints which comprises a plurality of layers each of which comprises a composition according to claim 1,
each of said layer compositions being sensitive to light of a wave-length ditterent from the wave-length to which any other of said compositions is sensitive; said layers being on a solid supporting surface.
9. A process for producing colored photographic prints which comprises preparing at least one composition according to claim 1; coating a solid supporting surface therewith, exposing the resulting article to a colored subject, thereby producing a negative image in color complementary to said colored subject.
10. The process of claim 9 wherein the image is intensified by heating for between 1 and 10 seconds after exposure.
11. The process of claim 9 wherein the developed print I is treated with a solvent to wash away the undecomposed dye base.
12. A process for producing a positive image where a negative produced by the process of claim 9 is printed onto another sheet of the same material.
13. The process of claim 9 wherein the permanence and brilliance of the color image produced is enhanced by treating the image with a metal salt solution to form a lake.
14. The process of claim 9 wherein the substrate is paper and after the colored image is produced, washing the developed image with water, drying the washed sheet, re-exposing the same with a blanket exposure, thereby producing a positive image of the subject.
15. A process for producing a litho master, comprising preparing the composition of claim 1; coating a caseinfilled paper therewith; exposing the composition to light through a suitable negative, thereby producing a positive image in color; swabbing the exposed sheet with water to render the background ink-repellent, the image area then being ink-receptive.
(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Ball at al. Jan. 3, 1950 14 Neugebauer et a1 Feb. 15, 1955 Ensink May 20, 1958 Chalk-ley Oct. 7, 1958 Chalkley Oct. 7, 1958 Wainer July 24, 1962 FOREIGN PATENTS Germany May 14, 1909 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 lOO TO3 August 13 1963 Robert H. Sprague et alt It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 4 line 14 for "diethylthiacarboeyanin" read diethylthiacarbocyanine lines 74 and "(5 the formula should appear as shown below instead of as in the patent:
l 1 I R-N-(cH:cH) -Y::(cH--cm W MA column 5 lines 8 and 9 the formula should appear as shown below instead of as in the patent:
column 7 lines 15 to 18 the formula should appear as shown below instead of as in the patent:
I- R I Q- N:(CHCH) m :C'-(I F-LI ,s N
column ll line 13 for "aralyityl" read aralkyl lines 60 and 61 the formula shoalappear as shown below instead of as in the patent:
strike out "R column 12 lines 3 same column 11 line 73,
hown below instead of as in t0 6, the formula should appear as s same column 12, line 19, after "ring" insert a comma,
Signed and sealed this 12th day of May 1964.
ERNEST W. SWIDER EDWARD J. BRENNER At'testing Officer Commissioner of Patents