US2787543A - Photographic color reproduction process - Google Patents

Description

Apnl 2, 1957 A. MURRAY ET AL 2,787,543

PHOTOGRAPHIC COLOR REPRODUCTION PROCESS Filed Oct. 9, 1952 LIGHT SENSITIVE POLYMER COLOR SEPARATION NEGATIVE EXPOSURE AND SOLVENT DEVELOPMENT COLOR/N6 SUB TRACT/VELY YELLOW imam/m cm/v ALEXANDER. MURRAY EARL M. ROBERTSON INVENTOR.

ATT'Y a Aa'r 1 Claim. (CI. 96-14) This invention relates to a process in color photography and more particularly to a color process involving the superimposition of colored polymeric relief images.

In the early stages of color photography, colored reproductions were made by the subtractive method of color photography by superimposing suitably colored gelatin relief images. It was early recognized that the various superimposed images should not undergo dimensional change in the presence of heat and moisture and this led to the use of water-resistant supports for the superimposed elements as well as for the transfer sheet upon which the superimpositions were made. As early as 1891, collodion-coated paper was used for this purpose and present-day processes of this type still utilize sensitive tissues having a cellulose derivative or other similar moistureresistant support. Glass and even wire screen have also been used to prevent the distortion of the images. In recent years in an effort to obtain films for superimposing which are more resistant to distortion in the presence of moisture, dichromate-sensitized colloid material such as dichromate-sensitized viscose and regenerated cellulose sheeting have been used. Obviously, such systems are relatively insensitive to light according to modern standards, are still moisture-sensitive, and are relatively unstable among other disadvantages.

In certain other well known processes of color photography in current use, the problem of distortion and registration of colored photographic images has been met by superimposing the layers recording the separate aspects of a colored subject as in multilayer color films. However, in certain instances such as in the printing trade when it is desired to obtain proofs of colored printing plates, the superimposition of individually colored elements is still desired.

We have discovered that if there are employed for the formation of suitably subtractively colored relief images certain solvent-soluble polymeric materials having relatively high light-sensitivity and which are relatively impermeable to moisture, the long-needed process yielding more dimensionally stable images for superimposition is made available and some disadvantages of prior art methods are overcome.

One object of our invention is, therefore, to provide suitable light-sensitive polymeric materials for use in making superimposed subtractively colored relief images. Another object is to provide a method for making the relatively dimensionally stable subtractively colored images for superimposition.

In the broadest phases of our invention we utilize a light-sensitive photographic element having a support preferably transparent and having high dimensional stability to some non-aqueous liquids, such as viscose, regenerated cellulose or a substantially fully esterified cellulose. ester such as cellulose triacetate and particularly surface-hydrolyzed cellulose acetate. This support is coated with a layer of an organic solvent-soluble light-sensitive polymeric material having monomeric units containing groups of the structure wherein n is 2 or 3 and R represents a mononuclear aromatic group of the benzene seriesor a polynuclear aromatic ted States Patent U. coupled with Z-smino-5-diethylamtuotoluene.

group as of the naphthalene series. A typical polymer is a cinnamic acid ester of polyvinyl alcohol.

In the accompanying drawings are shown in greatly enlarged cross-sectional view in Figs. 1-4 the appearance of three representative sensitive elements at various stages in the process of our invention wherein are prepared cyan, magenta and yellow colored relief images on transparent supports which are superimposed to form a full colored reproduction.

Our invention will now be described with particular reference to the accompanying drawings.

EXAMPLE 1 As shown in Fig. 1 of the drawings, three sensitive elements are provided having supports 10, 20 and 30, each carrying a layer of light-sensitive polymeric material 11, 21 and 31. A support suitable for this purpose is surface-hydrolyzed cellulose triacetate about .003 inch thick. Each of the three supports can be coated with a lightsensitive layer from a composition such as the following:

Anisalacetylpolystyrene grams.. 6 Furfural .cc Tricresyl phosphate grams 0.3

The polymer in the above composition is prepared as described in the Unruh et al. U. S. patent application Serial No. 246,516, filed September 13, 1951, now U. S. Patent 2,716,097, Example 3 thereof, by the condensation of anisaldehyde with polyvinyl acetophenone in the presence of mineral acid.

After drying the coated elements, they are exposed through the base separately by contact with the usual continuous tone subtractive primary color separation negatives at 4 feet from a 35-ampere carbon are. With the particular set of negatives used, the magenta negative required 10 seconds exposure, the cyan 7 seconds and the yellow 12 seconds, the exposure difference being due primarily to differences in maximum density of the separation negatives. The result of the exposure is to insolubilize the polymeric coating adjacent to the support in the region of the exposure.

The exposed elements are then developed in an organic solvent solution in order to remove the unexposed area. This development can be carried out with a mixture of 10 perecent benzaldehyde in methyl ethyl ketone for 1 /2 minutes followed by rinsing in a fresh solution of the mixed solvents. The result is to obtain three elements as shown in Fig. 2 of the drawings, each carrying a relief.

Solvents (cc.) and dyes (gm.)

Magenta Bath Yellow Cyan A Bath 33 Bath C Xylene Furiural Benzaldehyde" Dye A Dye B Dye O Azomethlne dye from Z-cyanoacetylcoumarone coupled with 2-amino-fi-dlethylaminotoluene.

*Azomethine dye from wbenzoylacetani1ide coupled with N,N'diethyl-p-phenylenedlamine.

Azomethiue dye from l-hydroxy-Z-[B-(4'-acetamido)phenethyllnaphthamlde (Example 2, 8. Patent 2,589,004)

As is apparent; baths A, B- and C are used for dyeing the images 22, 12 and 32 respectively and following this step each element is rinsed in a suitable solvent in which the dye has little if any soltiliility, for example, mnexaasr following the magenta bath A, isopropanol following bath B. and one of the Xylenes followingbath" C;

The d'y'e'delements new appear as shown in- Fig; 3 of the drawings wherein the elements having supports 10'; 2t and 30 are shown; as carrying the yellow, magenta and cyan dyed reliefs 1 3, 23 and 33 respectively.

ease the three relief images" on their separate supports are to be utilized as proofs for color printing plates or for simply" viewing as full color reproductions, they are superimposed as sndwnin Fig. 4'- of the drawings,- and viewed by transmitted light. If desirable, the elements may instead be superimposed on a White background for viewing byreflection; It Will be apparent that since the coloringmaterial ine'ach' of the'relief images is locked into a moisture-impermeable resinous relief image, the dyes therein are appreciably more stable under adverse conditions of temperature and humidity known to gfadually deteriorate dyes,than;are dye images in prior moisture susceptible elements such as mentioned.

EXAMPLE- 2 In a manner similar to Example 1, subtractively colored dye images are prepared on sheets of cellophane to effect coloring of at least the exposed regions of the elemerits before superimposition. I-n doing so, if the commercial product is used usually consisting of viscose coated with various substances, it is advisable in order to obtain utmost adherence of the relief images to the support, to" remove any solvent-soluble coatings on the surface of the sheet with solvent such as a mixture of ethyl-- ene"dich1o1ide' and ethyl acetate followed by a Wash with methyl cellosolve acetate. Three such sheets are then coated with the following" compositions:

ethyl ketone for 3 minutes follqwedj by a rinse in the] same solvent for 1172; minutes and a short" rinse in riiethyl cenbs'ol've acetate. Afterthis; each sheet'i's dyed in' a: solvent solution of the appro riate subtractivly colored dye correspondingto' th'e'i c'olor separation a's'peot each represents, such as thefollovvin'gz' Suitable cyan, magenta and yellow dyes foruse' in this dye solution are'yellow dyes such a's'the a'zo' dye obtained by coupling o-nitro-p-chloroaniline with 5';5-dime'thyl- 1,3-cyclohexadione awarding": to EXainple-4 and claim 7 of MeNally-et al.- U. S; Patent 2,183,997, December 19, 1939; a magenta dye suchas the azo dye obtained by coupling 2-chlbro-4-nitroaniline with bis-(fi-hydroxy; ethyl) sniliae'asdes'cnbed in Geigy Swiss Patent 169,946, June 15, I934, and a blue or cyan colored dye such as the azo dye obtained by coupling 2-amino-3,5-dinitrobenzenesulfonethylamide with l-Bp dihydroxy propyl- 2,7" climethyltetrahydroquinoline as described in the Dickey et all U. S. Patent 2,391'-,886,'January 1, 1946.

After dyeing the reliefimages with the respective dye solutions they can be rinsed with n-he'X-yl alcohol} dried and superimposed in the desired mannerto yield full color: repraduetionsfef' viwiiig for the desired purposes m'e'ntionellpreviously.-

4 Other transparent supports upon which the light-sensitive compositions may be coated and upon which the colored relief images may be formed are, for example, films of polyvinyl chloride; polyacrylonitrile, polyamides, phenolic resins and the like as will occur to those skilled in the art. r

EXAMPLE 3 The dyed paiymeric' relief images can more advantageously be formed froiii predyed light-sensitive polymeric compositions 's'iicl'ias the fonawing:

The dyes particularly suitable for use is thldye sannan s' above for" yein the" palymerie a r nals are the Swanson-ale dyesf as opifised to oil-soluble sr' watersoluble d es, dr' mixtures" of dyes, such as The first three dyes enumerated are respectiyely substantially identical to tanni ri lakes of Victoria Blue B, Auramine 0 c. I. 655 Victoria GrenlC, I. 657 Rotalin Redcortes'pondsto a riiixture of Rhodamine 6 SDN I. 752) and-Ant nna O (C. I. 6 55), the remaining- (lyes also jbeihg tannin lake s: 7

It is" thefefore apparent that basic dyes per se and par'ticularlyt'afinln and similar lakes thereof are especially useful for dyeing the light-sensitive coating compositions.

Another group of spirit s'olub le" d yes of equal value in this process are salts of acid dyes such as the following? v I q Linn Fast Black PS; Luxol- Fast Blue MBS Lllilbl East Red BB Liner Fast Yellow T These dyes are arylguanidine' salts of acid dyes.

These dys pai tieula'rly Ro't'zilindyes are" prefe'i'ie since" they arenetappreciably semenin the solvent develop'ensnlsedfor developing: the polynicrier'elief images such as t'r ichl-oroethylene' 01*" 20% methyl Cellosolvc acetate -in JiyleneI The dye compositions are coated for exain'plc 'orl' sheets of surface-hydrolyzed celluloseacetate, gelatin, subbed cellulose esters or on polyvinyl chloride. The sheets are then exposed to continuous toned negatives as above mentiefieebyeapesurerareagu thest'lppo'lft, for example, tne magm'a-celbredsheet re'eeiving' l irmint'lt'es exposure,

the cyan 1% minutes and the yellow 2. minutes at 4 feet from a 35,-ampere carbon arc,.when empl'oyingf theiLuxol dyes. Diiferent exposure times up to minutesare required depending upon the'dyes'used; The exposedfilms are then developed with solvent vapor such as .trichloroethylene for about 20 seconds or ina tray of solvent such as 20% methyl Cellosolve acetate in xylene for up to 5 minutes to remove the dyed polymer'in the areas not insolubilized by exposure to the continuous, tone negative. When the three single colored transparencies are superimposed, a full color transparency of good quality is obtained.

EXAMPLE 4 When it is desired to;obtain a black-and-White monochrome relief image or to add a. fourth color to a 3- color print or'transparency inthe form of a black resin image, suitable images are prepared by coating a black light-sensitive composition such as the following. onto a suitable support such as surface hydrolyzed cellulose acetate.

Polyvinyl cinnarnaten g'ram 7.5 Furfural cc 78 Xylene cc 30 Black dye grams 0.75 4-,4-tetramethyldiaminodiphenyl ketonedo .75

A suitable black dye for this composition is a spiritsoluble dye such as. Spirit Nigrosine (C. I. 864). As previously mentioned, dyes ofthis type are especially suitable since they are. retained bylth'e polymeric relief images during the development step. As in the previous examples, the sensitive coating is exposed. through the base in contact with a continuous tonephotographic negative for 2 to 5 minutes at a distance of 4feet from a 3'5-arnpere carbon arc. The image is developed for 2 /2 minutes in a percent solution of furfurali in xylene or for up to 5 minutes in the tray developer of Example 3' and rinsed for 30 seconds in a fresh mixture of the same solvents. The dye is insoluble in this developing solution andtherefore does not bleed out into the solvents. There results a clean, black, continuous tone'image reproducing a density scale of approximately 1.5 in the negative. ln'an alternative method, the relief image is developed by immersing the exposed sheet in vapor of trichloroethylene. The unexposed portion of the polymer dissolves in the condensate carrying'the dye'with' it physically while the dye insoluble in the trichloroethylene is'retained by the insoluble exposed polymer to produce a neutral continuous tone transparent positive image.

EXAMPLE 5 Our process can be applied particularly to proofing color printing plates as follows: on three separate sheets of surface-hydrolyzed cellulose acetate, coatings are made with three predy ed polyvinyl cinnamate solutions of the same composition as given in Example 3 above. Each sheet is then exposed for from 1% m8 minutes (depend ing on the dye used) at 4 feet from a 35-arnpere carbon are through a 266-line (or other appropriate ruling) halftone color separation negative corresponding to the color of the coating in vacuum contact with the surface of the polymer. The exposed sheets are then developed separately in a tray of 10 percent furfural in xylene for 2 minutes or in 20% methyl Cellosolve acetate in xylene for up to 5 minutes and rinsed for about 30' seconds in fresh solvent mixture. After drying the solvents from the polymeric reliefs, they are superimposed to produce a tricolor halftone color proof; With the proper selection of dyes, dye concentration, and exposure, reproducible color proofs can be made which accurately predict the out come of the final press sheet.

From the abovedescription it'will be apparent that since the light-sensitive polymeric materials are highly stable, colorless or precoloredlight-sensitive polymeric coated sheets in different colors can be supplied t0-the trade for quickly making color proofs. Such products conveniently include stripping films-having temporary supports from which the solvent developedcoloredrelief images on thin transparent supports'can-b'e stripped for superimposing to form a full'col'o'r reproduction. Also the relatively high light-sensitivity of the polymeric materials used in our invention promises extensive commercial utility for the light-sensitiveproductsfor exposure directly in a camera for the production of continuous'a'nd halftone multicolor images. The prior art processesfor making colored reproductions by superimposing colored relief images obviously suifered'in part due-to the low speed of the polymeric materials used'as'wellas the' p'oor resistance of such materials to moisture;

In large scale production, for example, involving mechanical methods for laminating'the above" individually colored transparencies together, our process provides an intrinsically cheaper method than obtainin'g'colorr'eproductions by means of integral .tn'pack color transparencies based upon silver halides and color development methods. Thus, while the particular source of the color separation aspects used inexposing the light-sensitive polymer coatings is not critical, negatives, for example, obtained by exposure of well known three-layer stripping' 'films having differentlysensitized silver halide emulsions; or negatives exposed in three-color one-shot cameras, are well suited for use in ourprocess;

The light-sensitive polymers given for illustration-in the above examples are by no means exhaustive of those contemplated for use in our invention. Other polymers represented by that of Example 1, the preparation of which are disclosed in-the. mentioned. Unruh et al. invention and in the. Unruh. et a1. U. S. patent application Serial No. 246,517, filed September 13, 1951, now U. S. Patent 2,706,725, granted May 19, 1955, are the organic solvent-soluble light-sensitive materials containing polymeric units having the group in which R is a mononuclear or a polynuclear aromatic group particularly of the benzene and "naphthalene series in which the nuclei are substituted or not, particularly the polymers made by substantially completelyacetylating a styrene polymer and condensing with an aromatic aldehyde, or a vinyl acetophenone polymer condensed with an aromatic aldehyde. These polymers contain monomeric units having the general structure in which n isa number fro-m 1 to 4 and Q is a mononuclear or polynuclear aromatic group particularly of the benzene or naphthalene series substituted or not and D is a single bond or aryl group of the benzene or naphthalene series. Accordingly, other polymers useful in our invention contain combined polymeric units of the following:

Isopropylbenzal acetylstyrene p-Hydroxybenzal acetylstyrene p-Dimethylamino acetylstyrene o-Chlorobenzal acetylstyrene p-Acetamidobenzal acetylstyrene p-Sulfobenzal acetylstyrene Anisal acetylstyrene Veratral acetylstryrene Anisal acetyl-o-methoxystyrene p-Hydroxybenzal acetyl-o-methoxystyrene o-Chlorobenzal acetyl-o-chlorostyrene p-Chlorobenzal acetyl-Z,S-dimethylstyrene 7 Anisal acetyl-p-phenoxystyrene Anisal acetyl-p-bromostyrene Tolual acetyl-3,4-dimethoxystyrene Anisal acetyl-o-fluorostyrene ot-naphthal acetylstyrene Anisal benzal-acetylstyrene Anisalvinylmethyl ketone Benzal acetylestyrene Benzal acetyl-o-methoxystyrene Benzal acetyl-o-, m-, p-chlorostyrenes Benzal acetyl-o-, rn-, p-bromostyrenes Benzal acetyl-p-beuzylstyrene Benzal acetyl-p-phenoxystyrene Benzal acetyl-3,4-dichlorostyrene Benzal acetyl-2,S-dimethylstyrene Benzal acetyl-m-methylstyrene Benzal acetyl-m-tert. butylstyrene Benzal acetyl-3,4-dihydroxystyrene The preferred light-sensitive materials are polymers of vinylacetophenones condensed with a suitable aromatic aldehyde such as anisaldehyde.

Other suitable light-sensitive polymers are the cinnamal viuylacetophenone polymers disclosed by the Unruh et a1. application Serial No. 246,515, filed September 13, 1951, now U. S. Patent 2,716,102. These polymers contain monomeric units having the general formula wherein D represents a single bond or a mononuclear arylene group, Q represents a mononuclear aryl group, n represents a whole number from 1 to 4, and R is alkyl, preferably of 1 to 4 carbon atoms, and are obtained by condensing a cinnamic aldehyde with, for example, a polymer of a vinyl acetophenone compound; for example:

Polycinnamalacetylstyrene Poly-a-n-amylcinnamalacetylstyrene Poly-p-chlorocinnamalacetylstyrene Poly-m-nitrocinnamalacetylstyrene Poly-o-chlorocinnamalacetylstyrene Poly-p-methoxycinnamalacetylstyrene Poly-p-methylcinnamalacetylstyrene Poly-p-chlorocinnamalacetyl-o-methoxystyrene Poly-p-methylcinnamalacetyl-o-chlorostyrene Polybenzalcinnamalacetylstyrene Polycinnamalmethylvinylketone The polymeric material polyvinyl cinnamate used in Example 4 was prepared by the methods of the Minsk et al. U. S. patent application Serial No. 207,052, filed January 20, 1951, and is the substantially fully acylated cinnamic acid ester of polyvinyl alcohol. While the substantially fully esterified cinnamic acid esters of polyvinyl alcohol defined in the Minsk et a1. invention are preferred for use in our invention since they are least moisture-susceptible, those cinnamic acid esters containing at least 60 mole percent of any cinuamoyl ester groups are useful in our invention in the predyed or colorless light-sensitive elements of the foregoing examples. Cinnamic acid esters of other materials such as of starch and hydroxy alkylated cellulose (Minsk et a1. U. S. patent application Serial No. 308,284, filed September 6, 1952, now abandoned) can also be used to good advantage. It will also be apparent that wecan use in the light-sensitive elements, mixtures of two or more of the light-sensitive polymers and each of the three or more elements used in making full-color reproductions may comprise a different light-sensitive polymer. As will also be apparent to'those skilled in the art, useful results can be obtained when the three light-sensitive polymeric elements are suitably sensitized and are exposed through suitable filters directly to the colored scene or subject to be reproduced, for example, by use of tricolor filter exposures in a camera to obtain line, halftone or continuous tone reproductions. Optical sensitization of the compositions is aided by use of the thiazole sensitizers disclosed in the West and Robertson U. S. patent application Serial No. 314,806, filed October 15, 1952 now U. S. Patent 2,732,301.

In Examples 3 and 4 are illustrated the use of sensitizing agents for the polymeric materials, for example, 4,4-tetramethyldiaminodiphenyl ketone. Other sensitizing agents useful in conjunction with any of the above enumerated sensitive polymers are the nitro, triphenylmethane, anthrone, quinone, diphenylketone and thiazole sensitizers respectively of the Minsk et a]. U. S. patent application Serial No. 148,684, filed March 9, 1950, now U. S. Patent 2,610,120, granted November 7, 1950, the Minsk et al. U. S. patent application Serial Nos. 207,048-51, filed January 20, 1951, now U. S. Patents 2,690,966, 2,670,285-7, and the above West et al. invention. Typical sensitizing agents of those inventions are 2,4,6-trinitroaniline, Crystal Violet dye, 2-keto-3-methyl- 1,3-diazabenzanthrone and 1,2-benzanthraquinone. The preferred sensitizer for all of the above uses where sensitizers are desired is 2-benzoylmethylene-l-methyl-flnaphthothiazoline because of its superior sensitizer activity and stability in combination with the polymer coatmgs.

From the above description it will be apparent that we have provided means for preparing colored relief images on transparent supports for superimposing. Our invention is further adapted to preparing such colored polymeric relief or resist images upon metallic supports such as are useful in the printing trade. That is, in the preparation of resists upon metal plates in photoengraving and photolithography it is desirable to provide a means for visual examination of the resist image before etching or proofing the plate. Consequently, when using the lightsensitive organic solvent soluble polymers such as indicated above for forming resist images, it is desirable to either bathe the resist in dye solution or to incorporate coloring material into the light-sensitive polymer composition before formation of the resist image. The latter procedure is preferred partly since the after-dyeing step can be dispensed with. However, prior to our invention dyes have not been found which would not bleed from the resist images during the course of the solvent development step such as employed in Example 3. Now by use of the dyes, such as given above, in the initial light-sensitive polymer compositions a variety of solvents such as those given in Example 3 can be utilized for solvent development of a resist image on various metal plates. Accordingly, in the preparation of a zinc lithographic plate a composition such as set forth in Example 3 can be coated on a freshly counter-etched zinc plate, exposed to a suitable line or half-tone subject and developed in a solvent such as trichloroethylene in liquid or vapor form to obtain a well defined colored resist on the zinc surface. In a similar manner the other light-sensitive polymers can be sensitized with the indicated sensitizing agents, and resists formed on zinc, magnesium or other metal plates. In a similar manner colored polymeric images can be formed on other surfaces such as ceramic ware, glass, paper, plastic, etc. for purely decorative purposes.

, What we claim is:

A method for preparing a colored photographic reproduction which comprises exposing to separate color aspects of a subject at least two photographic elements each carrying on a transparent support a layer of a lightsensitive organic solvent-soluble polyvinyl cinnamate subtractively colored with a spirit soluble dye, to insolubilize 10 the exposed areas of the layer, removing only the soluble References Cited in the file of this patent areas of the exposed layers with an organic solvent in UNITED STATES PATENTS which said dye is insoluble to obtain subtractively colored relief images of insoluble polymer on each support corg z i responding to said color aspects, and superimposing the 5 p .amec e resultinn elements 2,610,120 Minsk et a1 Sept. 9, 1952 FOREIGN PATENTS 384,364 Great Britain Dec. 8, 1932

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