US 2725305 A
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HARDENING GELATIN EMULSIONS AND GELATIN SOLUTIONS 7 7 No Drawing. Application January 2, 1952, Serial No. 264,676
9 Claims. (Cl. 117-34) This invention relates to the hardening of gelatin, either in the form of an emulsion layer in photographic films, plates or papers, or when applied in the form of a solution, as a coating for paper or other similar material by means of a cyclic 1,2-diketone.
It is common practice in the use of photographic emulsions to incorporate something therein to overcome the tendency of the gelatin constituent to melt or to swell during its processing, particularly at high temperatures. Some of the hardening agents which have been employed for this purpose are formaldehyde, diacetyl, mucochloric acid, glyoxal and the like. None of these materials has met all the demands which have been put upon them for this purpose, especially in photographic uses.
One object of our invention is to provide a method for hardening gelatin layers. Another object of our invention is to provide a method of hardening gelatin layers which overcomes some of the difiiculties encountered in the use of known hardening agents and to provide a method whereby gelatin emulsions may be given a satisfactory degree of hardening. A further object of our invention is to provide photographic emulsions which will resist relatively elevated temperatures without melting, and which will do so without objectionable fogging or desensitizing. A still further object of our invention is to provide gelatin layers which will be less subject to the phenomenon known as after-hardening. Other objects of our invention will appear herein.
nited States Patent We have found that certain cyclic 1,2-diketones are particularly effective when incorporated in gelatin solutions in rendering the gelatin layers obtained therefrom resistant to elevated temperatures and without undue swelling. We have found that, of the cyclic 1,2-diketones, the following are particularly useful for hardening purposes: cyclohexane-LZ-dione, cyclopentane-LZ-dione and 3-chlorocyclopentane-l,2-dione. We have found that hardening can be accomplished under the proper conditions with as little as A of a gram of the diketone per liter of gelatin solution, although often in actual use larger quantities of the hardener are desirable. Although these hardeners will be employed in most cases within the range of .255%, based on the weight of the gelatin in the emulsion, these limits are merely illustrative, and the proportion of hardener may be varied within wide limits and still be effective in imparting resistance to the gelatin coating.
Our method is carried out by incorporating the cyclic diketone in an aqueous solution of the gelatin in the proportion desired, and then coating out the solution upon the support therefor, such as a photographic film base, paper, cloth or any other surface to which the gelatin layer will adhere. These diketones do not increase the viscosity of gelatin solutions on holding them liquid prior to coating; this is an advantage over hardeners such as alums which tend to change the viscosity with time, making it much more diflicult to secure a uniform coating. The hardening occurs during the drying of the coating. The effectiveness of the hardening may be increased by subr lC Example 1 To 100 milliliters of a gelatin-silver bromide photographic emulsion containing about 7 grams of gelatin, 0.05 gram of cyclopentane-1,2-dione was added, and the emulsion was applied as a coating on glass plates. The emulsion layer was dried and was then incubated at 100 F., 78% relative humidity, for about 96 hours. A plate from this group and a plate having a check coating thereon prepared like the above but without the hardener, and incubated similarly, were tested for hardening by processing with a photographic solution at F. for 5 minutes. These plates were thereupon transferred to 0.5% acetic acid and held 10 minutes, then washed in running water, all of the operations being at 85 F. It was found that the controlled coating melted badly, leaving one edge very thin, but the emulsion coating in which the diketone had been incorporated showed no visible signs of melting.
Example 2 had not been employed.
We claim: 1. A method of preparing hardened gelatin coatings which comprises incorporating in an aqueous solution of gelatin containing 0.255%, based on the weight of the gelatin, of a cyclic 1,2-diketone selected from the group consisting of cyclohexane-1,2-dione, cyclopentane-1,2- dione and 3-chlorocyclopentane-1,2-dione, applying the gelatin solution in the form of a thin layer to a surface, and then drying the gelatin layer.
2. A method of preparing a hardened gelatin coating which comprises adding to an aqueous solution of gelatin 0.255%, based on the Weight of the gelatin, of a cyclic 1,2-diketone selected from the group consisting of cyclohexane-l,2-dione, cyclopentane-l,2-dione and 3-chlorocyclopentane-1,2-dione, applying the solution in the form of a thin layer onto paper, and subsequently drying the coating thus applied.
3. A method of preparing a hardened gelatin coating which comprises adding to an aqueous solution of gelatin 0.255%, based on the weight of the gelatin, of a cyclic 1,2-diketone selected from the group consisting of cyclohexane-l,2-dione, cyclopentane-l,2-dione and 3-chlorocyclopentane-l,2-dione, applying the solution in the form of a thin layer onto photographic film base, and subsequently drying the coating thus applied.
4. A method of preparing a hardened gelatin-silver halide photographic emulsion coating which comprises adding to the emulsion while in fluid form 0.25-5 based on the weight of the gelatin, of cyclopentane-1,2-dione, applying the emulsion in the form of a thin layer onto a support therefor, and drying the emulsion layer.
5. A method of preparing a hardened gelatin coating which comprises adding to an aqueous solution of gelatin 0.25-5%, based on the weight of the gelatin, of a cyclic 1,2-diketone selected from the group consisting of cyclohexane-1,2-dione, cyclopentane-1,2-dione and 3-chloro- Cyclopentane-LZ-dione, applying the gelatin solution in g the form of a thin layer to a surface, drying the gelatin layer and subjecting that layer to a temperature of 100 F. 6. A composition comprising gelatin containing therein 0.254% based on the .weight'of the gelatin of acyclic 1,2-diketone selected from the group consisting of cyclohexane-1,2-dione, cyclopentane-1,2-dione and 3-ch1orocyc1opentane-1,2-dione.
7. Gelatin containing 0.255% dione. V
8. Gelatin containing O.255% of cyclopentane-1,2- dione. t
4 9. Gelatin containing 0.255% pentane-1,2-dione.
of 3-chlorocyc1o- 1,851,166 Kienninger Mar. 29, 1932 2,071,559 Morgan Feb. 23, 1937 2,169,513 Brunken Aug. 15, 1939 2,356,477 Staud et a1. Aug. 22, 1944 2,476,240 Famulener July 12, 1949 2,534,326 Weaver Dec. 19, 1950