US3717467A - Hardening gelatino silver halide emulsions with reaction products of halogenated triazines and hydrophilic organic colloids - Google Patents

Abstract

A METHOD OF HARDENING PHOTOGRAPHIC LAYERS USING A NEW MACROMOLECULAR TYPE HARDENER, TO PROVIDE A GOOD WATER RESISTANCE AND YET A SUFFICIENT WATER ABSORPTION AND SWELLING THEERETO, WHICH IS PREPARED BY DISSOLVING A HALOGENATED TRIAZINE COMPOUND IN A LEAST QUANTITY OF A GOOD SOLVENT FOR BOTH SAID COMPOUND AND A HYDROPHILIC ORGANIC MACROMOLECULAR COLLOID BINDER TO MAKE THEM REACT IN AN AQUEOUS MEDIUM, THE PRECIPITATING AND SEPARATING THE REACTION PRODUCT WITH A LARGE QUANTITY OF A POOR SOLVENT FOR BOTH.

Description

United States Patent US. Cl. 96111 3 Claims ABSTRACT OF THE DISCLOSURE A method of hardening photographic layers using a new macromolecular type hardener, to provide a good water resistance and yet a sufiicient water absorption and swelling thereto, which is prepared by dissolving a halogenated triazine compound in a least quantity of a good solvent for both said compound and a hydrophilic organic macromolecular colloid binder to make them react in an aqueous medium, then precipitating and separating the reaction product with a large quantity of a poor solvent for both.

BACKGROUND OF THE INVENTION Photographic materials are composed of a photosensitive emulsion layer containing silver halide, which is the main constituent for photosensitiveness, and hydrophilic organic macromolecular binders applied supplementarily thereon, for example the protective layer, intermediate layer, underlayer and backing layer whose composition is almost the same as silver halide emulsion layer. Thus photographic materials are composed of a layer or layers of hydrophilic film applied on one side or both sides of a water resistant support. It is essential for these film layers, whether or not they are photosensitive, that upon photographic treatment after exposure to light, the developing solutions for photographic treatment should be allowed to sufiiciently penetrate and diffuse inthese layers. Since upon photographic treatment not only the photosensitive layer but also these supplementary layers play an important role as well, all these film layers are also included hereinafter to photographic layers. In these photographic layers having no photosensitivity there is a hydrophilic binder layer (called positive layer of the silver complex salt difiusion transfer process or transfer layer) which contains fine heavy metallic nuclei for physical development. This layer, which is generally applied separately to the support independent of silver halide emulsion layer, plays an important role in image formation, which is the basis of the photographic action. Therefore, such a transfer layer is also worthy of being called a photographic layer.

For these photographic layers, binders whose main constituent is gelatin have been widely used. In the past, natural substances such as starch and gum arabic were mainly used. In recent years, artifiicial'substances such as polyvinyl alcohol, polyacrylic acid, polyacrylamide, and various water soluble derivatives of cellulose, polyvinyl alcohol and starch have widely come into use, solely or in mixture with gelatin. However, photographic layers comprising these water soluble binders are generally poor in water resistance, and therefore swell in excess during treatments of developing, fixing and washing. As a result, troubles such as reticulation, blister, and frilling are apt to cause. Therefore, it is usual to prevent the softening 3,717,467 Patented Feb. 20, 1973 of the film layers by adding a simple aldehyde such as formaline, acrolein and mucochloric acid or inorganic salt such as potash alum and chromium alum to the film layers, or by treating them in a bath containing these compounds. In recent years, while severe developing treatment at high temperature is required as a result of technical progress, requirements are occurring for elevating the covering power of silver image with the use of least amount of silver or increasing the developing rate. For these purposes, it is usual to mix Roentgen emulsion, etc. with a binder such as dextrin, gum arabic or a starch derivative which is less resistant to water compared with gelatin. Various other binders are also mixed as a plasticizer for the purpose of preventing the contraction of the film layer and increasing its softness. Also in this case, the water resistance generally decreases. In order to reinforce this, stronger hardeners are required. While powerful hadeners comprising dialdehyde compounds, polyfunctional epoxy compounds or active vinyl compounds such as vinyl sulfones and vinyl ketones are developed, macromolecular hardeners such as a copolymer of polyvinyl methyl ether with maleic anhydride, or of styrene with maleic anhydride, a monomaleic ester of polyvinyl alcohol or starch, or dialdehyde starch are also on the market.

Macromolecular hardeners have in their long molecules many bonding points, where not only the molecules are crosslinked to each other but also they are crosslinked to molecules of other binders mixed therein to form a network structure. Although a great amount of water is coordinated and absorbed in this network, the film layer does not dissolve even when heated at a high temperature. This is a characteristic of high polymer hardening agents. This offers a striking contrast with the char acteristic of low molecular hardeners which, when the more powerful they are, make the film layer the more horny, decreasing the water absorption and swelling property. In the case of high polymer hardeners, they do not ditfuse or migrate from one layer to another which are superposed upon each other. Therefore, it is a further advantage of polymer hardeners that a given film layer could be hardened to a desired extent without hardening other layers at all.

As powerful hardeners which have recently been developed, there are those that have a nitrogen containing nucleus (such as s-triazine nucleus or pyrimidine nucleus) 7 having halogen atoms introduced therein as reactive groups which react completely with binders at room temperature. A dyestuif of which molecule has such reactive groups introduced therein is a so-called reactive dyestulf, which has the most powerful dyeing power and is a compound containing a hydrophilic group for dyeing in an aqueous solution. For a hardener of this sort, it is necessary, of course, to have water solubility in order to become a hardener for hydrophilic binder. Therefore, it has been believed hitherto that the hardener should be modified to the form of an alkali salt as shown in the following Formula I (Japanese patent publication No. 17,112/

1 967), or it is necessary to introduce a carboxyl or sulfonic group as shown in the Formula I-Ia or IIb (Japanese patent publication No. 16,9Q8/ 1964). (-In fact all the reactive dyestulfs have the latter form.)

or =N N; ;C-NHCHzCOOH C-N (31 Ha o1 j s no C-NH-Q-SOaH SUMMARY OF THE INVENTION A compound of the general formula or Na; R-C O-NHNHC/ 1;

wherein X is N: or CH R is H, CH or C H preferably or N--& CH;CONHNHC% \N 2 (Racetamino) phenylamine-4,6-dlcl1loro-1,3,5triazine is made to react in water with a Water soluble organic macromolecular colloidal binder for photographic use. Said compound is dissolved with a least possible amount of a Water miscible organic solvent which is a comparatively good solvent for both said compound and, said binder. After they have reacted homogeneously a great amount of a water miscible organic solvent which is com-- paratively poor solvent for both is added to precipitate the reaction product. The reaction product is separated and added to the main protective colloidal binders to constitute the photographic layer as a hardener. Said good solvents include formamide, dimethylformamide, dimethylformarnide, dimethylsulfoxide and tetrahydrofuran, and said poor solvents include methanol, ethanol; n-propanol, iso-propanol, butanol, acetone, and methyl ethyl ketone.

DETAILED DESCRIPTION In consideration of all those facts described in Background of the Invention, the inventors have come to an idea that when a compoundwhich is easier to synthesize 4 could be achieved, even though these compounds are not dissolved in Water.

Compounds having the following general formula were proposed for this purpose.

wherein X is -N= or --C; and R is H or an alkyl group having up to about two carbon atoms, namely CH or CZH5.

These compounds were attempted to be dissolved in such a solvent as mentioned above which is well miscible with water, and to be added directly to the solution for a photographic layer-of silver halide emulsion containing a binder solution or binder. These compounds, however, when used actually, dissolve at most to an extent of only 0.1% in an ordinary water miscible solvent such as alcohol or acetone. And when a fairly large amount of these compounds are added to the solution of hydrophilic organic high polymer such as gelatin or polyvinyl alcohol, which is to form the binder of the photographic layer, the hydrophilic binder is preciiptated and coagulated by these compounds, which act as a sort of precipitating agent. In general, necessary amount of a hardener to be added to gelatin is at least about 0.5 to 1% based on the weight of the dry weight of gelatin. On the other hand, the hardener dissolves in alcohol only to an extent of 0.1%. Accordingly, if silver halide emulsion, whose binder is for example gelatin, is desired to be hardened by this method, necessary amount of the hardener is 0.05 to 0.1 g. for ml. of the emulsion containing 10% of gelatin. This necessitates to add 50 to 100 ml. of alcohol, thus allowing to precipitate and separate out the emulsion at once. Therefore, it is required to added a more concentrrated solution of the hardener dissolved in an especially powderful solvent such as formamide, dimethylformamide, or tetrahydrofuran. When a 2% solution of the hardener dissolved in such a solvent is used in the'above example, necessary amount of thesolvent is only 2.5 to 5 ml. Further, these solvents are good solvents for high polymers in general and also for gelatin, starch and polyvinyl alcohol, and naturally do not precipitate them. Thus, there is no problem in this point. 0n the contrary, however, even a small amount of them causes the physical properties (setting point, melting point, tenacity of the film, viscosity of the liquid, etc.) or hydrophilic binders such'as gelatin to be markedly injured, thus leading to troubles in the applying and drying operation of the solution. Accordingly, it would be better, if'possible, to avoid direct iapplying of these powerful solvents to the photographic ayer.

Now the inventors, after repeating many experiments, have succeeded in: making it possible to add to the photographic layer the hardener that is made soluble in water to a desired extent using a proper combination of two orgarn'c solvents miscible with water, avoiding their unfavorable eifects. If these powerful solvents are used, it is easy to add a necessary amount of hardener to the binder. Thus, the hardener is added to the solution'of a hydrophilic' binder such as gelatin, polyvinyl alcohol, starch, etc. together with such a solvent. In an appro priate step of 'the reaction. (Theoretically, it is obvious that the degree in which one of the two halogen atoms of triazineor pyrimidine nucleus has reacted issuitable.) A great amount of a solvent such as methanol, ethanol, n-propanol, i'sopr'opanol," acetone, or methyl ethyl ketone which is miscible with water but is 'a poor solvent for the binderlis added to precipitate the binder which has been made to react. The mother li uid is removed, the

precipitate is washed with alcohol, the precipitate is dissolved in water and the dissolved precipitate is precipitated again. By these operations, the powerful solvent such as formamide, unreacted hardener, hydrogen halide produced as a by-product is washed away. Thus, the desired binder combined with the hardener is separated in a purified form as a hardener of the macromolecular type. Even if about 0.5 to 10% of the above-mentioned hardener based on the dry weight of the binder are made to react and combined, the reaction product does not usually lose the characteristic water solubility of the binder. Therefore, the reaction product precipitated with alcohol or acetone and dried may be dissolved in water again to use. But usually this is dissolved again in water without being dried in this step, and is used for hardening of photographic layer as an aqueous solution containing neither alcohol nor the powerful solvent such as formamide which is unfavorable to the physical properties of the coated layers. Thus this hardener of the high polymer type can be used as a part of the binder which forms the photographic layer. If, for example gelatin containing 5% of hardener is obtained, and is substituted for to 20% of the whole binder, the percentage of the hardener in the whole binder is equivalent to 0.5 to 1% of the hardener added to the whole binder. Thus a photographic layer having a sufiicient hardening property and yet having excellent water absorption is obtained. As a result of overall consideration of the difficulty of synthesis, yield, cost, stability of the resulting substance, solubility in alcohol, and reactivity in these cases, it has been confirmed that 2(pacetamine)-phenylamine-4,6-dichloro-1,3,5-triazine having the following formula is the most suitable for this purpose.

(Ill N-O C at (This is the case wherein X is N=, R is CH in the previously mentioned general formula.) This substance is synthesized in nearly theoretical yield by a known method (for example J. Phot. Sci. 11 (1963), p. 340). The purified product is a purely white crystal having a melting point of 236 to 237 C. (decomposition) and is much more stable than the p-formyl compound. (The case where R=H in the general formula.) In the above literature, it is described that the solubility in ethanol is about 2.8% at a high temperature and about 1.2% at a low temperature, However, this would be an error. According to the inventors measurements, the solubility in ethanol or methanol was both less than O.-1%, and 2 to 3% in formamide, dimethylformamide, etc. Since this substance has dichlorotriazine group, it naturally reacts and combines in a neutral or alkaline condition with various substances having 'NH, NH or OH groups such as gelatin, polyacrylamide, polyvinyl alcohol or cellulose, etc., while liberating hydrochloric acid. Usually one chlorine atom reacts at first, and two chlorine atoms do not react in water if not in a severe condition. It is aimed in this invention when the dried film layer is cured, two chlorine atoms react to form crosslinkage between the molecules. I

Among hydrophilic binders having reactive groups such as NH, NH OH, etc., gelatin is most widely used. Besides gelatin, the following substances may be used: casein, polyacrylamide, poly-alanin, a copolymer of -a1anin with acrylamide, polyethylene iniide, polyvinylamine, polyvinyl alcohol, vinyl polymers, copolymerized with these polymers, or derivatives of these compounds, etc. Polyvinyl alcohol is well known as a substitute for gelatin, and reacts and combines with this dichloro-s-triazine compound like cellulose. But it is difficult to mix polyvinyl alcohol itself with gelatin. A derivative of this compound of which a part of OH groups is changed to monoester of a dibasic acid may be mixed with gelatin easily. A copolymer of vinyl ethyl ether with maleic anhydride, or a copolymer of styrol with maleic anhydride does not react but becomes more reactive when they are changed to half-amide with the use of ammonia or an amine group, and can be used for this purpose. Accordingly, every binder mentioned above should also be considered as a kind of a water soluble organic high polymer colloidal binder capable of reacting and combining with dichloro-s-triazine nucleus.

EXAMPLES Example 1 Five grams of 2(p acctamino) phenylamino-4,6-dichloro-l,3,5-triazine, 250 g. of dimethylformamide and N-NaOH solution were added dropwise under stirring at 40 C. to a gelatin solution comprising 100 g. of gelatin for photographic use and 1900 ml, of distilled water, the NaOH solution being added so that the pH of the gelatin solution is maintained at a value between 7 and 8. The temperature was maintained between 40 to 45 C. After the whole solution is mixed, it is maintained at the same temperature for one hour to perform a reaction thoroughly. Then, while cooling the whole solution, about 4 liters of acetone were added and the reaction product was precipitated. The supernatant was removed, and the precipitate was washed with one liter of ethanol. The mother liquid was removed, one liter of distilled water was added, and the water was warmed to dissolve the precipitate. After cooling, two liters of acetone were added to precipitate again. Then, after distilled water was added to make up to one liter and the whole solution was warmed, it was again cooled to set. The coagulum was shredded into small noodles. The resulting jelly was used without being dried. During such operation, the loss of gelatin is usually about 15 to 20%. Therefore, 120 g. of the jelly are considered to correspond to 10 g. of gelatin and 0.5 g. of the hardener. Upon adding the jelly to the emulsion etc., this Was taken into account.

Measurement of the hardening power was conducted as follows:

As shown in the following table, gradually increasing amounts of the jelly were added to 10% gelatin solution and were dissolved. The resulting solutions were applied respectively on glass plates to form an equal thickness and dried. After curing for 24 hours, the glass plates were warmed gradually in water and in an ordinary developing solution. The temperatures at which the coated layers on the plates soften and dissolve were measured and deter mined as the melting points. As shown in the table, it was found that almost complete hardening was achieved with about 1% of the hardener. Even with about 0.5%, hardening sufiicient for practical use was attained.

A. B C D E Composition of the solution applied (g.):

Resulting jelly 0 3. 0 6 12 24 10% gelatin solution 50 47. 5 45 40 30 W or 50 49. 5 49 48 46 Hardener/gelatin 0 0. 25 0. 5 1.0 2.0 Melting point of dried film 0.):

In water 32 32 61 100 100 In developing solution... 32 39 66 Example 2 According to the method of D. Klinke (Z. wiss. Pht. 57 (1963), p. 154), maleic monoester of polyvinyl alcohol of substitution ratio of about 50% (half of OH groups of polyvinyl alcohol being substituted by vinyl maleic groups) was easily synthesized with g. of polyvinyl alcohol and 300 g. of maleic anhydride in 200 g. of glacial acetic acid in the presence of 200 g. of sodium acetate as the catalyst. The yield was g. and a part of the carboxylic acid was found to have changed to its sodium salt. In the following there will be shown an example in which the abovementioned reaction product was used. (Similar results were obtained with reaction products of ditierent degree of substitution.)

Fifth grams of the above-mentioned maleic monoester of polyvinyl alcohol were dissolved in one liter of distilled water. To this solution 2 g. of 2(p-acetaminoJ-phenylamino-4, 6-dichloro-l,3,5-triazine and 100 ml. of formamide were added dropwise at a temperature of 40 to 50 C., while regulating the pH of the solution at a value of from 7 to 8 with N-NaOH solution. After the addition was finished, the same temperature was maintained for two further hours. Thereafter, the solution was poured into 6 liters of cold methanol to form a precipitate. The supernatant was removed and the precipitate was washed twice with a small amount of methanol. Then the precipitate was dissolved in 500 ml. of distilled water and was precipitated again with 3 liters of methanol. After being washed with methanol, the precipitate was dissolved in distilled water to make up to 500 ml., thus obtaining about a 10% solution of the hardener of this invention.

A concentrated emulsion produced by forming a precipitate from a high sensitive bromide emulsion according to an ordinary method using phthalic monoester of polyvinyl alcohol was prepared. (This method of precipitation Was filed for another Japanese patent application, and therefore a brief explanation is made here.) One liter of a 10% solution (pH 6.5) of polyvinyl monophthalate (the substitution ratio being about 53%) was added to 3.5 liters of an emulsion prepared from 100 g. of silver halide and 300 g. of gelatin, and at pH 3 a concentrated emulsion was obtained as a precipitate in the form of mass. This was washed twice with 1% acetic acid, and 1.6 kg. of a concentrated emulsion was obtained. Thus 160 g. of this concentrated emulsion contains 30 g. of gelatin and 10 g. of polyvinyl alcohol monophthalate, and this constitutes a part of the final binder.

Now color photographic paper for silver dye bleaching method was prepared as follows: At first 100 g. of the hardener solution of this invention was added to 160 g. of the above concentrated emulsion. Then, optical sensitizing dyestuffs for red and blue were added respectively to the emulsions in order to form cyan and magenta layers. Further, emulsions added with about 3 g. of Direct Blue (CI 24410), and Diamine Rose (CI 15080), and about 6 g. of Brilliant Yellow (CI 124890) were respectively prepared. To these emulsions were added the ordinary additives before applying including stabilizers for each emulsion and saponin, and the total weight of the liquid was made up to 600 g. with water.

On the other hand, as the solution for the intermediate layer and protective layer 30 g. of gelatin and 10 g. of hydroxypropyl starch were dissolved in water together with 100 g. of a 10% aqueous solution of the hardener of this invention, and additives of nearly the same composition as in the emulsion were added. The solution was made up to 600 g. On the surface of so-called RC paper which right surface and reverse surface are respectively coated with pigment-filled polyethylene added with titanium di-oxide and polyethylene resin-first 30 g./m. of the above-mentioned red sensitive cyan color emulsion was applied and 20 g./m. of an intermediate layer was applied thereon; then the green sensitive magenta color emulsion layer and other intermediate layer were applied similarly; finally the blue violet sensitive yellow color emulsion layer and the protective layer were applied, and the resulting paper was dried. Thus, photographic paper suitable for obtaining enlarged color positive images from color slides by the so-called silver dye bleaching method was prepared.

In this case, for each layer, the ratio of polyvinyl alcohol monomaleate to the whole binder was 20% and the ratio of the monochloro-s-triazine hardener added thereto was 1% On the other hand, the hydrophilic binder except gelatin goes up to 40% based on the weight of the total binder. Therefore although this photographic layer has good water absorption and swelling property and low development inhibiting power, the whole hardening property is excellent and completely withstands the treatment of strong hydrochloric acid bleaching solution of the silver dye bleaching method. Moreover, since this hardener acts as a good mordant for acid dyes there was no necessity for further mordant treatment.

We claim:

1. A method of hardening a photographic layer comprising admixing an aqueous solution of a reaction product of (1) a compound of the formula wherein X is a moiety selected from the group consisting of ---N: and CH= and R is selected from the group consisting of hydrogen, methyl and ethyl with (2) a hydrophilic colloid binder selected from the group consisting of gelatin, starch, poly(vinyl alcohol), gum arabic, polyacrylic acid, polyacrylamide, polyvinyl methyl ether-maleic anhydride, styrene-maleic anhydride copolymers, dextrin, casein, poly-fi-alanin, a copolymer of ,B-alanin and ncrylamide and polyvinyl amine into a gelatino-silver halide emulsion constituting the photographic layer, and wherein the aqueous solution of the reaction product is prepared by (a) dissolving a hardening amount of said compound in a least amount of a water miscible good solvent for both components selected from the group consisting of formamide, dimethylformamide, dimethylsulfoxide and tetrahydrofuran,

(b) admixing the resulting solution into an aqueous solution of said hydrophilic colloid binder and causing said compound to react with said hydrophilic colloid binders in a homogeneous state,

(0) precipitating the reaction product with a large amount of a water miscible poor solvent for both components selected from the group consisting of methanol, ethanol, 11- propanol, iso-propanol, butanol, acetone, and methyl ethyl ketone,

(d) Washing with water and (e) dissolving said reaction product in an aqueous medium.

2. The method of claim 1 wherein said hardener is 2 (p-acetamino)-phenylamino-4,6-dichloro-1,3,5-triazine.

3. A photographic element comprising a support having thereon at least one gelatino-silver halide emulsion layer containing an aqueous solution of a reaction product of (l) a compound of the formula wherein X is a moiety selected from the group consisting of N: and CH= and R is selected from the group consisting of hydrogen, methyl and ethyl with (2) a hydrophilic colloid binder selected from the group consisting of gelatin, starch, poly(vinyl alcohol), gum arabic, polyacrylic acid, polyacrylamide, polyvinyl methyl ether-maleic anhydride, styrene-maleic anhydride copolymers, dextrin, casein, poly-B-alanin, a copolymer of fi-alanin and acrylamide and polyvinyl amine wherein the aqueous solution of the reaction product i prepared by (a) dissolving a hardening amount of said compound in a least amount of a water miscible good solvent for both components selected from the group consisting of formamide, dimethylformamide, dimethylsulfoxide and tetrahydrofuran,

(b) admixing the resulting solution into an aqueous solution of said hydrophilic colloid binder and causing said compound to react With said hydrophilic colloid binders in a homogeneous state,

(c) precipitating the reaction product with a large amount of a Water miscible poor solvent for both components selected from the group consisting of methanol, ethanol, n-

10 propanol, iso-propanol, butanol, acetone, methyl ethyl ketone, (d) washing with water and (e) dissolving said reaction product in an aqueous medium, and wherein said reaction product is present in an amount sufiicient to cause hardening of said gelatino-silver halide emulsion layer.

References Cited J. TRAVIS BROWN, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R.