US2541884A - N-substituted isoalloxazines as catalysts in the dye bleach baths for color photography - Google Patents

N-substituted isoalloxazines as catalysts in the dye bleach baths for color photography Download PDF

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US2541884A
US2541884A US794822A US79482247A US2541884A US 2541884 A US2541884 A US 2541884A US 794822 A US794822 A US 794822A US 79482247 A US79482247 A US 79482247A US 2541884 A US2541884 A US 2541884A
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isoalloxazines
substituted
dye
silver
catalysts
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Fritz W H Mueller
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GAF Chemicals Corp
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General Aniline and Film Corp
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Priority to GB32325/48A priority patent/GB651124A/en
Priority to DEP26709A priority patent/DE824884C/en
Priority to CH285165D priority patent/CH285165A/en
Priority to FR991224D priority patent/FR991224A/en
Priority to CH280857D priority patent/CH280857A/en
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C7/00—Multicolour photographic processes or agents therefor; Regeneration of such processing agents; Photosensitive materials for multicolour processes
    • G03C7/28—Silver dye bleach processes; Materials therefor; Preparing or processing such materials

Definitions

  • This invention relates to a method of processing photographic color pictures, and particularly to N-substituted iso'alloxazines as accelerators for dye bleach baths used in producing dyestuff images from dyed silver images.
  • the latter image must be treated with a bleach bath which decolorizes or bleaches the dyestuff present in the photographic layer in the areas where the metallic silver is present.
  • a bleach bath which decolorizes or bleaches the dyestuff present in the photographic layer in the areas where the metallic silver is present.
  • azo dy s the substantivezand acid-typ althou h some basic vat dyes and alizarines may also be employed.
  • the bleaching or decolorization of the dyestuff is accomplished in a bleach bath in which there occurs a simultaneous decolorization of the dye with an oxidation of the metal image at the points where silver is present, i. e., the metallic silver is converted into a silver compound which may be removed subsequently by fixation in a solution of hypo.
  • the bleach baths employed in this process, consist of an aqueous solution of a mineral acid or a mineral acid containing an alkali halide, such as potassium iodide, ammonium chloride, or both.
  • an alkali halide such as potassium iodide, ammonium chloride, or both.
  • Such baths require a relatively long treating time so as to destroy the dyestuff present in situ with the silver image.
  • Long treatment in bleaching solutions of high acidity has the tendencyto soften-the gelatin of the photographic emulsion containing a silver image and bleachable azo dye.
  • bleaching solutions of high acidity has the tendencyto soften-the gelatin of the photographic emulsion containing a silver image and bleachable azo dye.
  • celerators they are highly colored substances carriers becoming readily reduced by the action of the bleach solution with concomitant oxidation of th asilverimage and destruction ot-the y in situ therewith.
  • R represents an aliphatic group, e. g., methyl, ethyl, propyl, butyl, amyl, hexyl, etc., hydroxyalkyl, e: g hydroxyethyl, hydroxypropyl, hydroxybutyl', etc., dihydroxyalkyl, e. g., dihydroxypropyl, dihydroxybutyl, dihydroxyamyl, etc.,
  • polyhydroxyalkyl e. g d-ribityl (from d-ribose), l-arabityl (from l-al abinose), d-lyxityl (from dlyxose), d-dulcityl ffrom d-galactose), d-mannityl (from d-mannose), d-sorbityl '(from'd-glucose), etc.
  • phosphoric acid esters and the mono-, di-, and tri-acetic and succinic acid esters thereof, amino-alkyl group e.
  • phenyl, naphthyl, etc. aralkyl, e. g., benzyl, phenylethyl, menaphthyl, and the like
  • Z represents the atoms necessary to complete an aromatic or heterocyclic ring, e. g., benzene, naphtholene, anthracene, etc., piperidine, pyridine,,pyrimidine, quinoline, methylenedioxy, isopropylidenedioxy, and the. like.
  • the aromatic and heterocyclic rings maybe substituted in the various positions by alkyl, di-alkyl,
  • N-substituted isoalloxazines gfiavinsl although colored substances rangingijrfrom reddish-orange to yellow in color, are not substantive to gelatin, do not stain the gelatinilayer, and do not afi ect the quality of the final imagep
  • N-substituted isoalloxazines employed in accordance with the present invention:
  • N-substituted isoalloxazines 'a-re generally prepared by the condensation of an N- substituted o-aminoaniline and alloxan.
  • the N- alkyl isoalloxazines, with an alkyl group in 10- position higher than methyl (see illustration 1), can be prepared by a method analogous to the one described by Tishler et al., J. Amer. Chem. Soc. 67, p. 2165, 1945, by reacting a 2-alkyl substituted o-phenylenediamine with 5,5-dichlorobarbituric acid.
  • Isoalloxazines with an alkyl group in either '7- and S-pcsition or both higher than methyl or ethyl, can also be prepared by Tishler et al.s method by using N-alkyl substituted,phenylenediamine derivatives with the proper alkyl substituents in the 4-, 5-positions as starting materials.
  • the monophosphoric acid esters of the polyhyg droxy isoalloxazines can be prepared by the method outlined in Ber. 68, p. 383, 1935. 'The corre ponding triacetates can be'prenaredby the method outlined in Ber. 69, p. 1545, 1936.
  • the compound shown in illustration 29 is prepared by treating 4,5-methylenedioxy-o-phenylenediamine with alloxan and methylating the re-- sulting product with dimethyl sulfate in a manner analogous to the method described in Ber. 67, p. 1942, 1934..
  • the compound'shown inillustr'atioh' 30 is prepared by treating 4-chloro-5-nitroisoproylidenedioxybenzene with. methylamine, the 4-methy1- amino-5-nitro derivative is catalytically reduced and the reduced compound treated with 5,5-dlchlorobarbituric acid.
  • N-s ubstituted isoalloxazines can bereduced to form leuco derivatives which can be re-oxidized with considerable case, a factor which greatly adds to their value as accelerators in accordancewiththe present invention.
  • the reduction can be carried out by wellknown chemical means, for example, withsodium hydrosulfite (Ber. 66,319, 1933), with hydrogen in the presence of palladium oxide (ibid. p. 5'76), or with zinc dust (Ang. Chem. 47, 318, 1934); it can also be effected with the aid of enzymes which are contained in yeast, muscle, liver, heart, brain and kidney tissue (Ber. 66, 1298-1302, 1933).
  • the N-substituted isoalloxazines may be employed in any mineral acid bleach bath, such as, for example, hydrochloric, hvdrobromic, hydroiodic or phosphoric acid, with or without the presence of an alkali halide, such as sodium or pottassium bromide or, iodide,isodium chloride, ammonium chloride, and the like.
  • an alkali halide such as sodium or pottassium bromide or, iodide,isodium chloride, ammonium chloride, and the like.
  • the concen-- tration of the acid to'be employed is dependent upon the character of the gelatin constituting the photographic coolr "emulsion layer or layers.
  • the concentration of the acid ranges up to 2 N. I prefer, however, to employ a concentration up to 1 N.
  • the amount employed as catalysts is not critical. The higher the amount within practical limits the greater the catalytic activity. amount as small as 0.005 gram per liter of bleach bath showed an appreciable bleaching action in sliver bearing images.
  • I EX LE I -Three kilograms of a wet gelatino silver halide emulsion, containing about 10% gelatin, 445% of silver-brorrioicdide, 10 cc. of a 10% solution ofsaponin,and 10 grams of d-1 neny1 big'uanide hydrochloride were separated into three equal portionsof 1 kilogram each and utilized in the preparation of the final red, green, and blue sensitive emulsions.
  • EXAMPLE III A halogen silver-bearing layer colored with Diamine Pure Blue FF (Schultz Farbslofitabellen 1931, an 8d., #308) was treated with-a bleach solution of the following composition:
  • the dye was completely bleached within 10-15 minutes.
  • R represents a member selected from the class consisting of aliphatic and aryl groups
  • Z represents the. atoms necessary to: completea member selected from the class consisting of aromatic and heterocyclic ring systems.
  • R represents a member selected from the class consisting of aliphatic and aryl-groups, and Z represents the atoms necessary to complete a memberselected from the class consisting of aro-;

Description

Patented Feb. 13, 1951 N -SUBSTITUTED ISOALLOXAZINES AS CATALYSTS IN THE DYE BLEACH BATHS FOR COLOR PHOTOGRAPHY Eritz H. Mueller, Biiighamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware N'c Drawing Application December 30-, 194 7,
, Serial 794,822
12 Claims. (01. 9588) This invention relates to a method of processing photographic color pictures, and particularly to N-substituted iso'alloxazines as accelerators for dye bleach baths used in producing dyestuff images from dyed silver images.
It is known that in the production of photographic dyestuff images from difiusely dyed photographic emulsions containing a silver image,
the latter image must be treated with a bleach bath which decolorizes or bleaches the dyestuff present in the photographic layer in the areas where the metallic silver is present. The dyes,
which are employed in the difiuse dyeing of the silver-halide emulsion layer, are primarily azo dy s 'the substantivezand acid-typ althou h some basic vat dyes and alizarines may also be employed. The bleaching or decolorization of the dyestuff is accomplished in a bleach bath in which there occurs a simultaneous decolorization of the dye with an oxidation of the metal image at the points where silver is present, i. e., the metallic silver is converted into a silver compound which may be removed subsequently by fixation in a solution of hypo.
The bleach baths, employed in this process, consist of an aqueous solution of a mineral acid or a mineral acid containing an alkali halide, such as potassium iodide, ammonium chloride, or both. Such baths require a relatively long treating time so as to destroy the dyestuff present in situ with the silver image. Long treatment in bleaching solutions of high acidity has the tendencyto soften-the gelatin of the photographic emulsion containing a silver image and bleachable azo dye. Moreover, by the use of such baths,
celerators, they are highly colored substances carriers becoming readily reduced by the action of the bleach solution with concomitant oxidation of th asilverimage and destruction ot-the y in situ therewith.
The N-substituted isoa-lloxazines are characterized by the following formula:
x NH N/ 0 wherein R represents an aliphatic group, e. g., methyl, ethyl, propyl, butyl, amyl, hexyl, etc., hydroxyalkyl, e: g hydroxyethyl, hydroxypropyl, hydroxybutyl', etc., dihydroxyalkyl, e. g., dihydroxypropyl, dihydroxybutyl, dihydroxyamyl, etc.,
polyhydroxyalkyl, e. g d-ribityl (from d-ribose), l-arabityl (from l-al abinose), d-lyxityl (from dlyxose), d-dulcityl ffrom d-galactose), d-mannityl (from d-mannose), d-sorbityl '(from'd-glucose), etc., and the phosphoric acid esters and the mono-, di-, and tri-acetic and succinic acid esters thereof, amino-alkyl group, e. g., aminomethyl, aminoethyl, aminopropyl, ethylaminobutyl, diethylaminobutyl, N-heteroamino alkyl, i. e., piperidinobutyl, morpholinopropyl, and the like, aminohydroxyalkyl, e. g., dimethylaminohydroxypropyl, diethylami nohydroxypropyl, etc., and their hydrochlorides, carboxyalkyl, e. g., carboxymethyl, carboxyethyl, carboxypropyl, carboxybutyl, etc.,, aryl, e. g., phenyl, naphthyl, etc., aralkyl, e. g., benzyl, phenylethyl, menaphthyl, and the like, and Z represents the atoms necessary to complete an aromatic or heterocyclic ring, e. g., benzene, naphtholene, anthracene, etc., piperidine, pyridine,,pyrimidine, quinoline, methylenedioxy, isopropylidenedioxy, and the. like. The aromatic and heterocyclic rings maybe substituted in the various positions by alkyl, di-alkyl,
value as represented by R, amino, halogen, e. g.
and-are lsubstantive-to-gelatin, i. e., leave a stain in the gelatin layer which is difficult to remove, and, which seriously" affects the quality of the final image.
I have; discovered that N-substituted isoalloxazines gfiavinsl, although colored substances rangingijrfrom reddish-orange to yellow in color, are not substantive to gelatin, do not stain the gelatinilayer, and do not afi ect the quality of the final imagep The N=substi tuted isoalloxazines presumably act as very efi'ective hydrogen chlorine or bromine, hydroxy, sulfo,
nitro, and the like. 7
The following are examples of N-substituted isoalloxazines employed in accordance with the present invention:
1,8,10-trii'defimliaaallokazlfle .5 Ber. 67, p. 1932, 1934.
carboiiy,
6,7-dimethyl-10-d-ribitylisoalloxazine 7 Proc. Soc. Exp. Brol. Med. 55, p. 184, 1944.
6,8-dimethyl-lo-d-ribitylisoalloxazine' Ber. 683, p. 172, 1935.
9- f Hon HO-J'J-H 7,9-dimethyl-10-d-ribitylisoal1oxazine Ibid.
( CHzOH EiO- l-H HO -H $11, I N 11: N O=O it Lill 9-aca-10-propylflavin Ber. 71, p. 1243, 1938.
7.8-is0propylidenedioxy-lO-methylisoalloxazine The foregoing N-substituted isoalloxazines 'a-re generally prepared by the condensation of an N- substituted o-aminoaniline and alloxan. The N- alkyl isoalloxazines, with an alkyl group in 10- position higher than methyl (see illustration 1), can be prepared by a method analogous to the one described by Tishler et al., J. Amer. Chem. Soc. 67, p. 2165, 1945, by reacting a 2-alkyl substituted o-phenylenediamine with 5,5-dichlorobarbituric acid. Isoalloxazines, with an alkyl group in either '7- and S-pcsition or both higher than methyl or ethyl, can also be prepared by Tishler et al.s method by using N-alkyl substituted,phenylenediamine derivatives with the proper alkyl substituents in the 4-, 5-positions as starting materials.
The monophosphoric acid esters of the polyhyg droxy isoalloxazines (as'shown in illustrat ons 4 'to 14) can be prepared by the method outlined in Ber. 68, p. 383, 1935. 'The corre ponding triacetates can be'prenaredby the method outlined in Ber. 69, p. 1545, 1936.
The compound shown in illustration 29 is prepared by treating 4,5-methylenedioxy-o-phenylenediamine with alloxan and methylating the re-- sulting product with dimethyl sulfate in a manner analogous to the method described in Ber. 67, p. 1942, 1934..
The compound'shown inillustr'atioh' 30 is prepared by treating 4-chloro-5-nitroisoproylidenedioxybenzene with. methylamine, the 4-methy1- amino-5-nitro derivative is catalytically reduced and the reduced compound treated with 5,5-dlchlorobarbituric acid.
The process of preparing isoalloxazines, having a polyhydroxyalkyl group in lo-pos tion, is described in United States Patents 2,238,874 and 2,350,376. 51'
All of the foregoing N-s ubstituted isoalloxazines can bereduced to form leuco derivatives which can be re-oxidized with considerable case, a factor Which greatly adds to their value as accelerators in accordancewiththe present invention. The reduction can be carried out by wellknown chemical means, for example, withsodium hydrosulfite (Ber. 66,319, 1933), with hydrogen in the presence of palladium oxide (ibid. p. 5'76), or with zinc dust (Ang. Chem. 47, 318, 1934); it can also be effected with the aid of enzymes which are contained in yeast, muscle, liver, heart, brain and kidney tissue (Ber. 66, 1298-1302, 1933).
The N-substituted isoalloxazines may be employed in any mineral acid bleach bath, such as, for example, hydrochloric, hvdrobromic, hydroiodic or phosphoric acid, with or without the presence of an alkali halide, such as sodium or pottassium bromide or, iodide,isodium chloride, ammonium chloride, and the like. The concen-- tration of the acid to'be employed is dependent upon the character of the gelatin constituting the photographic coolr "emulsion layer or layers.
Usually, the concentration of the acid ranges up to 2 N. I prefer, however, to employ a concentration up to 1 N.
Inasmuch as the N-substituted isoalloxazines are water-soluble yellow to orange dyestuffs, which do not stain the gelatin, the amount employed as catalysts is not critical. The higher the amount within practical limits the greater the catalytic activity. amount as small as 0.005 gram per liter of bleach bath showed an appreciable bleaching action in sliver bearing images. For practical purposesfamounts ranging from 0.005 to 2.5 grains peri-literiofbleach stlb's'tituted' isoallOXaZihS disclosed and contemplated herein maybe employed in any mineral acid bleach bath, I prefer, however, to employ the polyhydroxyisoalloxazines shown in illustrations 4' to I i-and the acid esters thereof shown rimstrations 15 to 19 because of their general avaiia bility and ease of preparation. The following examples will illustrate the preparation of a multi-layer color film, in which after exposure, the dye images are obtained by the.
silver dye bleach process, and'the bleach baths containing the N-substituted isoalloxazines as accelerators. I
. I EX LE I -Three kilograms of a wet gelatino silver halide emulsion, containing about 10% gelatin, 445% of silver-brorrioicdide, 10 cc. of a 10% solution ofsaponin,and 10 grams of d-1 neny1 big'uanide hydrochloride were separated into three equal portionsof 1 kilogram each and utilized in the preparation of the final red, green, and blue sensitive emulsions.
Red sensitive To thefirst portion of a red sensitized wet gelatino silver-halide emulsion there wereadded grams of a bleachable cyan dye, Direct Sky Blue (0. I. #520).
;; Green sensitive To the second portion of a green sensitized wetf'gelatino silver-halide emulsion there were added 1.25 grams of a bleachable magenta dye, Fast-Acid Magenta B (C. I. #30).
' I Blue sensitive =..To the third portion of a blue sensitive wet gelatino silver-halide emulsion there were added an additional 5 grams of d-iphenyl biguanide hydrochloride as a dye precipitant and 6.8 grams of a "bl'eachable yellow dye, Dianil Yellow o .;'1. #650 w Coating Processing The finished film, prepared in accordance with the foregoing, was exposed and developed for 15 minutes in a black and white developer of the following composition:
Water cc 750 Metol grams 1.5 Sodium sulfite (anhydrous) do 80 Hydroquinone do 3 Potassium bromide..- do 0.5 Water to make "liter-.. 1
t tained-for 3 "minutes in a tamer; his; following com o t V sodium "acetate; grams= 20 jc c Water to makerer i r r r liter 1 Fixed-for 3 minutes in a -solution of the following composition: water I time, Hy o I l i245... Sodium sulfit'e (anhydrous) d Acetic acid (28%a'queous solution) -cc I Potassium alum -grarns' I Water to make. ..liter.
The fixed-film was then cut into 6 equalistripsand the strips treated for 10-15 minutes in dyebleach baths or the "following compositionsr. i
i I (a; Hydrochloric acid, conc cc .I 250 Water to make liter 1 N0 satisfactory bleaching action on-the dyes was observed within 15-30 minutes.
To I no '5 cc. of a 0.1% aqueous solution'of I ribo'fiav'inwas added. Appreciable bleaching'of. the dyes in all silver bearing areas "took place.
Hill) Hydrochloricacid, 'c'onc cc 1100 Potassium iodide -.gr-arms 100:- Water to make ...-liter;.. '1
Slight bleaching action was obtained in the cyan, magenta and yellow layers.
To II (a) 10 cc. of a 0.1% aqueous solution of riboflavin was added. Complete bleaching in the cyan layer and considerably accelerated "bleachings were obtained in the magenta and yellow layers "with satisfactory color balance.
' III (a) Hydrocmonc and, cone 'co mo Potassium "iodide "game ron A mmonimn chloride "do 100 Water to make li ter- "-",',1
Slight action in cyan and appreciable action in magenta and yellow layers.
To 111 (a) 10 cc. of a 0.1% aqueous solution of 6 riboflavin was added. I I I Complete bleach in the cyan layer within 10-15 minutes and considerably accelerated bleachings were obtained in the magenta and yellow layers with satisfactory color balance.
EXAMPLE n The bleaching treatment of Example I was repeated on the same fixed color film strips, with the exception that 7,8,IO-trimethylisoalloxazine "was substituted for riboflavin with similar results.
EXAMPLE III A halogen silver-bearing layer colored with Diamine Pure Blue FF (Schultz Farbslofitabellen 1931, an 8d., #308) was treated with-a bleach solution of the following composition:
Hydrobromic acid cc 250; Phosphoric acid ester of riboflavin gram 005 Water to make liter .1
The dye was completely bleached within 10-15 minutes.
While the present invention has been described in considerable detail with reference to certain preferred procedures, materials, and uses, it is understood that the invention is .not"l imited thereto, that numerous variations maybe made in the procedures herein described, and that,
equivalent materials may be substitued. Thus, for example, azo dyes other than those specifically mentioned and utilized in the foregoing ex-.;
image'in a photographic emulsion layer con-W tainin'g a bleachable azo dye and a silver image consisting of an aqueous solution of hydrochloric acid, ammonium chloride, potassium iodide and an accelerating amount of an agent selected from .the group consisting of N-substituted.iso-" alloxazines corresponding. to the following-:gen-
eral formula:
f I N N g I /i[1:\O 0.. Z 1
NH N where R represents a member selected from the class consisting of aliphatic and aryl groups, and
Z represents the. atoms necessary to: completea member selected from the class consisting of aromatic and heterocyclic ring systems.
2. A dye bleach bath according to claim 1 in which'the accelerating'agent is riboflavin.
isoalloxazine.
4. A dye bleach bath according to claim 1 in which the acceleratingagentis the phosphoric acid ester of riboflavin.
5. The process of producing a colored image in an exposed and developed photographic layer Several hundreds of such dyes 3. Adye bleach bath according to claim 1 in" K Y which the accelerating agent is 7,8,10-trimethyl Number containing a silver image and a bleachable and.
dye which comprises bleaching said layer in a bath comprising an aqueous solution of a min-- 'eralacid and an accelerating amount of an agent selected from the group consisting of N- substituted isoallcx-azines corresponding to the following general formula:
where R represents a member selected from the class consisting of aliphatic and aryl-groups, and Z represents the atoms necessary to complete a memberselected from the class consisting of aro-;
matic and heterocycllc ring systems.
6. The process according to claim 5 in which the accelerating agent is riboflavin.
7. The process according to claim 5 in which the accelerating agent is 7,8,10-trimethylisoalloxazine.
8. The process according to claim 5 in which the accelerating agent is the phosphoric acid ester of riboflavin. 1
9. A dye bleach bath according to claim 1 in which the accelerating agent is araboflavin.
' 10. A dye bleach bath according to claim 1 in which the accelerating agent is 8-ethyl-10-dribitylisoalloxazine.
11. The process according to claim 5 in which the accelerating agent is araboflavin.
12. The process according to claim 5 in which the accelerating agent is 8-ethyl-10-d-ribitylisoalloxazine. 1
FRITZ W. H. MUELLER.
REFERENCES CITED Thefollowing references are of record in the file of this patent:
UNITED STATES PATENTS Name Date 2,221,793 Gaspar Nov. 19, 1940 2,270,118 Gaspar Jan. 13, 1942 2,341,034 Gaspar Feb. 8, 1944 2,410,025 Gaspar Oct. 29, 1946 OTHER REFERENCES Handbook of Chemistry, Lange, 6th edition, Handbook Publishing Co., Sandusky, Ohio. Sept. 1946; page 738 particularly cited.
Journal of the American Chemical Society, 67;
page 2165.
Berichte der deutschen Chemischen Gesellschaft, 67, p. 1932, 1934.

Claims (1)

  1. 5. THE PROCESS OF PRODUCING A COLORED IMAGE IN AN EXPOSED AND DEVELOPED PHOTOGRAPHIC LAYER CONTAINING A SILVER IMAGE AND A BLEACHABLE AZO DYE WHICH COMPRISES BLEACHING SAID LAYER IN A BATH COMPRISING AN AQUEOUS SOLUTION OF A MINERAL ACID AND AN ACCELERATING AMOUNT OF AN AGENT SELECTED FROM THE GROUP CONSISTING OF NSUBSTITUTED ISOALLOXAZINES CORRESPONDING TO THE FOLLOWING GENREAL FORMULA:
US794822A 1947-12-30 1947-12-30 N-substituted isoalloxazines as catalysts in the dye bleach baths for color photography Expired - Lifetime US2541884A (en)

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BE486550D BE486550A (en) 1947-12-30
US794822A US2541884A (en) 1947-12-30 1947-12-30 N-substituted isoalloxazines as catalysts in the dye bleach baths for color photography
GB32325/48A GB651124A (en) 1947-12-30 1948-12-14 N-substituted isoalloxazines as catalysts in the dye bleach baths for color photography
DEP26709A DE824884C (en) 1947-12-30 1948-12-24 Dye bleach bath for the production of a color image in a photographic emulsion layer with a bleachable azo dye and a silver image
CH285165D CH285165A (en) 1947-12-30 1948-12-29 Process for the production of colored images from tinted silver images.
FR991224D FR991224A (en) 1947-12-30 1948-12-29 Improvements in the production of color photographic images
CH280857D CH280857A (en) 1947-12-30 1948-12-29 Dye bleach bath intended for the production of a colored image.

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2221793A (en) * 1938-05-17 1940-11-19 Gaspar Bela Method of producing photograph dyestuff pictures
US2270118A (en) * 1936-12-14 1942-01-13 Chromogen Inc Production of colored photographic pictures
US2410025A (en) * 1936-12-14 1946-10-29 Chromogen Inc Production of colored photographic pictures

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2270118A (en) * 1936-12-14 1942-01-13 Chromogen Inc Production of colored photographic pictures
US2341034A (en) * 1936-12-14 1944-02-08 Chromogen Inc Production of colored photographic pictures
US2410025A (en) * 1936-12-14 1946-10-29 Chromogen Inc Production of colored photographic pictures
US2221793A (en) * 1938-05-17 1940-11-19 Gaspar Bela Method of producing photograph dyestuff pictures

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DE824884C (en) 1951-12-13
FR991224A (en) 1951-10-03
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CH285165A (en) 1952-08-31
GB651124A (en) 1951-03-14

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