United States Patent COLOR PHOTOGRAPHIC SILVER DYE BLEACH MATERIAL CONTAINING AZO DYES WITH ACYL BLOCKED AUXOCHROMIC GROUPS Willibald Pelz, Opladen, Karlheinz Kabitzke, Cologne- Buchheim, Karl-Heinz Freytag, Leverkusen, Hans Vetter and Justus Danhauser, Cologne-Stammheim, and Erich Bockly, Leverkusen-Steinbuchel, Germany, assignors to Agfa-Gevaert Aktieugesellschaft, Leverkusen, Germany No Drawing. Filed Feb. 25, 1969, Ser. No. 802,244 Claims priority, application Germany, Mar. 16, 1968,
P 16 22 916.6 Int. Cl. G03c 1/10 US. Cl. 96--99 2 Claims ABSTRACT on THE DISCLOSURE A silver dye bleach photographic emulsion sensitive to a primary color is dyed with a diffusion-resistant azo dye that has an auxochromic group which gives the dye an absorption maximum in that primary color but which group is blocked by substitution with a blocking substituent that shifts that maximum away from said color and is readily saponified during silver dye bleach processing.
The invention relates to a multicolor photographic material for use in the silver dye bleaching process, which photographic material contains azo dyes which do not absorb in the range of the spectrum to which the light-sensitive silver halide emulsion layers containing said azo dyes are sensitive.
The production of color images by the silver dye bleaching process is known. Photographic materials which are used for this purpose generally contain red-sensitive silver halide emulsion layers having a cyan azo dye, a green-sensitive silver halide emulsion layer having a magenta azo dye and a blue-sensitive silver halide emulsion layer having a yellow azo dye.
'One special advantage of the silver dye bleaching process is that images which are very fast to light are obtained. Since the light-sensitive materials contain dyes which absorb in the range of the spectrum to which the silver halide emulsion which contain them are sensitive, the photographic materials for the silver dye bleaching process have only a comparatively low sensitivity. Hence, their application for use as copying materials is limited.
Various processes have already been described to overcome this disadvantage. According to one known method, colorless hydrazo compounds are used, these compounds being converted into an azo dye of the desired color after exposure and during photographic processing. According to another known method, azo dyes, the color of which depends on the pH, are used. Layers which contain such dyes can be adjusted, for example, to acid pH values, the absorption of the azo dyes then being shifted reversibly into a region which lies outside the sensitivity range of the particular silver halide emulsion layer. After processing, the desired colors of the different partial images are obtained by the changes of pH in the layer.
The principle of having in the light-sensitive layers, dyes which do not absorb in the region of the spectrum to which the silver halide emulsion layers are sensitive and after exposure converting them into the final image dyes during the photographic processing is suitable for solving this problem since the sensitivity of the layers can then be made several times greater. The known methods have, however, many disadvantages, so that it has not previously been possible to put them into practice. These disadvantages include, for example, the fact that conversion of the original dye into the final image ice dye during photographic processing proceeds too slowly. In the case of hydrazo compounds, the photographic properties of the materials are impaired. The above method in which the reaction involves a change in pH can hardly be used in practice because the color images remain dependent on the pH because the conversion reaction is reversible. If pH changes occur in the atmosphere, the final picture may deteriorate in quality.
It is the object of the invention to develop a lightsensitive photographic material for use in silver dye bleaching process which contains azo dyes which do not absorb in the sensitive range of the spectrum of the silver halide emulsions in which they are contained and which can be converted into the image dyes during photographic processing, which conversion must proceed sufliciently rapidly and be irreversible.
A highly sensitive photographic material for the silver dye bleaching process has now been found which contains at least one silver halide emulsion layer which is sensitive to one of the three primary colors of the visible spectrum and which contains an azo dye, the absorption maximum of which does not lie in that range of the spectrum to which the emulsion is sensitive but which can nevertheless be converted into one of the three image dyes during photographic processing. These dyes characteristically have auxochromic hydroxyl or amino groups which are blocked in such a way that they can be liberated by saponification during the photographic process.
The present invention is based on the principle that the absorption properties can be substantially altered by blocking of the auxochromic groups. If the blocking group is split off again, the dye with the original properties is obtained again. To this is added the fact that the blocked dyes have a much lower color intensity.
Any of the azo dyes known to be suitable for the silver dye bleaching process may be used for the photographic materials used according to the invention for this process, provided they contain one or more auxochromic groups blocked with saponifiable groups.
The blocking group should be stable enough that the blocked azo dyes are not saponified by the usual method of preparation of the photographic materials using aqueous casting solution, but are saponified only after exposure and during photographic processing. The saponification may be effected in the required treatment baths, e.g. in the alkaline developer, or by means of special baths introduced into the process for this purpose. The final image dyes are obtained after saponification of the blocking groups.
The following, inter alia, are suitable blocking groups which are saponifiable:
in which R denotes a saturated or unsaturated aliphatic group preferably containing up to 5 carbon atoms, or an aromatic group which may be substituted, preferably phenyl.
Compounds of the following general formulae are X is an auxochromic hydroxyl or amino group which is blocked in the manner described above;
R is an aromatic carbocyclic or aromatic heterocyclic radical of a diazo component, which radical may contain additional azo groups and auxochrome groups; preferably R represents a radical of the phenyl series in which the phenyl ring may be substituted, for example, with alkyl, alkoxy or sulfo;
R is an aliphatic group or an aryl group, especially phenyl, which groups may contain further substituents,
e.g. water-solubilizing groups; and R is hydrogen or is the same as R Yellow dyes which ar suitable for blocking in accordance with the present invention have been described, for example, in British patent specifications 918,087, 924,535 and 955,892 and in German patent specification 740,708.
Blocked azo dyes which are suitable for the production of the magenta part of the image comprise those of the following formula in which R is hydrogen, hydroxyl or amino which may be acylated, sulfo or sulfamyl which may be substituted with alkyl groups; and R is the same as R Magenta dyes suitable for blocking in accordance with the present invention have been described, for example, in British patent specifications 1,077,628 and 1,099,335, German patent specifications 1,039,839; 1,039,840 and Belgian patent specification 664,755. 7
V vL N=N vIr vm in which:
10 It" X SOQH R is an arylene group which may be substituted, e.g. phenylene, naphthylene, diphenylene or a group' of the following formula:
X is a blocked hydroxyl group; and RVIII is the same as R but at least one of the two substituents represents a naphthalene sulfonic acid group.
Cyan dyes which are suitable for blocking in accordance with the present invention have been described, for example, in British patent specifications 551,501; 711,232; 939,906; 1,028,562; 1,042,300; 1,045,705; 1,101,215; in German patent specifications 740,708; 1,041,335; in French patent specifications 956,677; 1,007,209 and in US. patent specification 2,286,714. The yellow dyes in their blocked form are colorless to very pale yellow.
The magenta image dyes when blocked are orange and the cyan image dyes when blocked are red to violet. ,The following are examples of suitable dyes:
I moo y C, H3U-H-- ---N- N-- ;UUHN NH o0 i nnoo scan 4 1,097,270 and in Swiss patent specification 418,128 and Dyes of the following formula are suitable for ing the cyan image dye during processing:
CH3 CH3 OCH;
in known manner. One possible method of blocking is de- 60 scribed in detail below: Dye 13 90 parts by weight of the dye of the following formula:
011 mm H SOaH NH Along with 180 parts by weight of benzoyl chloride and 360 parts by volume of pyridine are stirred together for 3 hours at a bath temperature of 110 C. When the 75 reaction is finished, most of the pyridine is evaporated off and the residue is taken up in 1000 parts by volume of potassium bicarbonate solution. The solution is adjusted to pH 5 with hydrochloric acid and stirred for some hours; a product which can be isolated by suction filtration is formed in this way. This product is dissolved in 1300 parts of water and precipitated with 270 parts by volume of potassium bicarbonate solution at C. The reaction mixture is then vigorously stirred together with 900 parts of 3% sodium chloride solution at 25 C., filtered using suction, washed and dried. Yield about parts by weight.
The blocked azo dyes may be used in known manner. They are, of course, as fast to dififusion as the unblocked dyes from which they are derived. Other necessary prop erties such as the fastuess to light and ability to be bleached are determined by the properties of the unblocked dyes which represent the final image dyes.
The photographic materials according to the present invention are about 5 to 10 times more sensitive in the sensitive region of the spectrum of the silver halide emulsion layers, than similar layers which instead of containing the blocked dyes contain the unblocked dyes from which they are derived. The photographic materials according to the invention can therefore be used for taking photographs.
The photographic materials according to the invention may be subjected to a simple black-and-white negative development after exposure and may then be worked up in the usual manner to produce direct positive dye images.
Alternatively, black-and-white reversal development may be carried out, in which case, dye images which are opposite in gradation to the original are obtained after passing the photographic materials through the treatment baths of the silver dye bleaching process. In such way images are obtained which are positive color-prints or colored transparencies when starting from color negatives.
The blocked dyes are substantially inert to the usual quantities of emulsion additives such as stabilizers, plasticizers, wetting agents and other materials, e.g. added sensitizers.
The dyes which are used according to the invention are added in the usual manner to the silver halide emulsions which may contain silver chloride, silver bromide or mixtures thereof, if desired together with silver iodide. Color photographic materials produced with the use of these dyes can be cast on any supports made of paper, baryta paper, polyethylene-coated paper, polypropylenecoated paper or paper which has been rendered hydrophobic in some other manner, glass, metallized foils of all tyes, cellulose acetates in transparent or pigmented form and on transparent or pigmented substrated foils of polyester, etc.
The blocking group which alters the absorption properties of the azo dyes is in most cases easily saponifiable in the alkaline developer bath. There is generally no need to alter the composition of the developer bath. Slight alterations in both the development and the saponification of the blocking group can easily be detected by a few simple tests.
In a few cases, it may be advisable to insert a separate saponification bath into the process. This may be inserted before or after the first development. Aqueous alkaline baths having a pH of between 9 and 14 are suitable for saponifying acyl groups. If the blocking group is attached to the dye molecule by an ether bond, it is preferable to use acid saponification baths, i.e. aqueous baths having a pH of between and 4. The saponification baths optionally contain wetting agents.
The rest of the process, in particular the bleaching of the dye, is carried out in the usual manner, e.g. with baths based on quinoline and iodide or on thiourea and different bleaching catalysts such as quinoline, quinoxaline derivatives, etc.
EXAMPLE 1 6.5 g. of a dye of Formula No. 13 are dissolved in 400 ml. ofwater and added to 800 ml. of a melted redsensitized silver bromide gelatine emulsion. After the addition of 20 ml. of a 1% aqueous solution of N,N,N"- trisacryloylhexahydrol,3,5-triazine as hardener, the emulsion is cast on a layer support of pigmented cellulose triacetate in a layer thickness of about which corresponds to a silver application of 0.8 to 1.3 grams Ag/m One strip of the unexposed material is fixed in and acid fixing bath. Another strip is exposed with red light in a conventional sensitometer behind a step wedge and worked up as follows:
(1) Development, 5 minutes in:
G. p-Methylaminophenol 1 Hydroquinone 3 Sodium sulfite 13 NaBr l Soda 26 Water up to 1000 ml.
(2) Wash, 5 minutes.
(3) Harden, 5 minutes in:
Formalin (30%) ml Soda g v20 Water up to 1000 ml.
(4) Wash, 5 minutes.
(5) Dye-bleach, 15 minutes in:
Potassium iodide g 10 Sodium hypophosphite g 5 Sulfuric acid conc. ml 75 Quinoline ml 50 Water up to 1000 ml.
(6) Wash, 5 minutes.
(7) Bleach-fix, 10 minutes in:
Tetrasodium ethylene diamino-tetra-acetate 26 Soda sicc. 24 Ferric chloride 15 Sodium sulfite anhydrous 13 Sodium thiosulfate 200 Water up to 1000 ml.
(8) Wash, 15 minutes.
A cyan dye wedge of high brilliance and which has good whites is obtained after drying.
The absorption properties of the sample which has been completely processed and of the comparison sample which has only been fixed are compared in the following table:
As the table shows, before processing, the density of the blocked dye in the region of 640 to 700 m (in which the emulsion is sensitized) is only a fraction of the density after processing, so that a considerable increase in sensitivity is achieved.
EXAMPLE 2 5.5 g. of the dye of Formula No. 19 are dissolved in 400 ml. of water and added to 800 m1. of a red-sensitized silver bromide emulsion. After the addition of 20 ml. of a 1% aqueous solution of N,N',N"-trisacryloyl-hexahydro-l,3,5-triazine, the emulsion is poured on a layer support of cellulose triacetate with a layer thickness corre sponding to a silver application of 0.8 to 1.3 g. Ag/m.
The same procedure as given in Example 1 is used, but the processed step wedge is subsequently treated with 0.5 N NaOH for 5 minutes and then thoroughly washed. A cyan dye wedge with good whites is obtained. The absorption properties before and after processing are shown in the table below:
Density Processed sample Comparison Wavelength, m
13 EXAMPLE 3 Density Comparison Processed Wave length, m sample sample We claim:
1 A light sensitive photographic silver dye bleach silver halide emulsion, sensitive to a primary color of the spectrum and containing as the bleachable: dye a diffusionfast azo dye that has several water-solubilizing groups per molecule, has an absorption maximum in a region of the spectrum difierent from that to which the emulsion is sensitive, and contains an auxochromic hydroxyl group, or an auxochromic amino group on a pyrazole ring, said SOsH O HsCO 14 auxochromic group being blocked by a readily saponifiable acyl substituent which is unblocked during the silver dye bleach processing to produce a diffusion-fast azo dye that has several water-solubilizing groups per molecule and dyes the layer a color complementary to that of the light to which the emulsion was sensitive.
2. The combination of claim 1 in which the bleachable dye is selected from the group:
HOaS- SOaH SOaH