US2146938A

US2146938A - Production of photographic emulsions

Info

Publication number: US2146938A
Application number: US69520A
Authority: US
Inventors: Claus Bruno
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-04-05
Filing date: 1936-03-18
Publication date: 1939-02-14
Anticipated expiration: 1956-02-14
Also published as: FR803585A; GB472639A; BE414540A

Description

Patented Feb.14,1939 I 2,146,938

PRODUCTION OF PHOTOGRAPHIO EMULSIQNS Bruno Claus, Halle-on-the-Saale,

No Drawing. Application March 18, 1936, Serial No. 69,520. In Germany April 5, 1935 8 Claims. (01. 95-

My invention relates to photographic emulsions bromide of a, finer grain preformed in the form and o e especially t means whereby emulsions of a sediment and which may or may not have possessing particularly favorable properties can been emulsified in an emulsion substratum such be produced in a particularly simple and effective as for instance gelatine, the mixture thus obmanner. V tained being subjected to a suitable aging tem- As is well known to those skilled in the art, perature under the action of chemical substances the Production of Photographic emulsions by first favoring the aging process, such as for instance causing the silver halide and more especially silsolutions of ammonia. ver bromide to be preformed separately and to In the carrying out of the new process, I may settle as a sediment and to thereafter emulsifyfor instance proceed as follows:-- 4 10 mg the silver salt in a binder such as for instance Eaample 1 gelatine, offers the advantage, as compared with o other modes of preparation of such emulsions, A 10% solution of potassium bromide containthat it avoids the circumstantial, unreliable and me a ut 4% p tas u iodide d w i-may time-consuming subsequent. washing, whereby further contain some. gelatine is mixed With a 15 the preparation of photographic mixtures of 11- solution of nitrate of silver, which solution may ver halides and gelatine or the like are greatly also contain some gelatine, the two solutions besimplified. Hitherto this mode of proceeding 8 mixed in Such pr p that in the merely allowed producing fine-grained phototure a ht excess of bromide, for instance graphic emulsions, which were little sensitive to amounting to is Present The Silver hallde the action of light and to produce similar emulformed in the solution is allowed to settle down sions, which are known under the name of as a Sediment, whi h i w Washed A P peptisation emul i it v di r. or .oflthis sediment, say one lfifth is then emulsified coarse grain size appeared impossible, in an aqueous gelatine solution contalmng am- I have now found that the solution of this monia (about 3% gelatine and 2% ammonia) r problem is of paramount importance since my and the mixture 15 HOW heated p to 50 t0 experiments hav shown th t pepfisation emu]- varying in accordance with the degree of sensisions of the kind aforesaid and more particularly tivity of the gelatine used- To the shghtly heated such emulsions of this kind which have been mixture is 110w gradually added some of the caused t age by adding ammonia, are not only washed silver halide sediment. and, if necessary, 30

to distinguished by t simplicity, t n t there 18 also gradually added some ammonia be produced but also by their high Sensi such an extentthat the ammonia which evaptivlty to the action or light, which as a rule surorates during P' period is replaced. to passes the sensitivity of emulsions of the same stantially maintain the initial concentration, unorder of grain size which were produced accordtn the remainder of the sflver halide is i mg to some customary mode of production Now gelatine is added the mixture of silver 0 AS I have already mentioned above t was halide and gelatine until the emulsion contains hitherto om sslble to mduce 'tisation suflicientgelatine (about 9%). After the missemulsions fi f a fine and apssnsitivity ing gelatine has thus been added, the emulsion a till be kept some time at an elevated temup to about 14 Din. According to the present may 8 inventionnowx am enabledtopmduce peptisafion perature without adding ammonia, and then the 40 ammonia still present in the emulsion is cautious- 3:5 2;; g gf figfi g ggg :gz' i gg g g f ly neutralized, for instance by adding citric acid.

tivity to light, being in certain cases finer grained The emulsion now ready for pourmg" than corresponding emulsions of similar sensi- Example 3 I i 45 "uvity which were fimduced according to A 10% potassium bromide solution containing about 0.4% potassium iodide and which may also v The new process for. the production of peptisacontain a small proportion of elatine, is mixed tion emulsions possessing these desirable DI D- with a solution of nitrate of silver, which may erties Substantially -fi therein, that to 8 also contain some gelatine." The silver halide 50 silver halide e u more especially to a Silver formed in the mixture is allowed to settle as a b d Sediment which y. y "not yet sediment, which is washed out and emulsified in have been emulsified in a binder, for instance an aqueous 3% solution of gelatine, for instance gelatine, is gradually added during the aging by adding some ammonia. The emulsion is now perloda silver halide and more silver divided; to one or the two portions is added some proceeding is continued until the whole of the emulsion has been added. 'I now add so much gelatine, that the emulsion contains about 9% gelatine. The mixture may be kept at an elevated temperature for some time without adding ammonia, until the greater part of the ammonia still present in the gelatine has evaporated; The remaining emulsion may be neutralized by adding citric acid and may then be poured.

Example 3 300 grams silver nitrate are dissolved in 3000 ccms. distilled water.- n the other hand, 210 grams potassium bromide, 7.5 grams potassium iodide and grams gelatine are dissolved in another 3 litres distilled water. The silver salt solution is now entered under continuous stirring in the alkali halide solution. After the silver halide has formed and settled down as a sediment, the supernatant liquid is removed by decantation and the silver'bromide is washed once with distilled water and divided in two parts. The first part is added under continuous stirring to a solution containing 400 grams gelatine and 100 ccms. of a 25% ammonia solution in 4500 ccms. distilled water. This mixture is kept minutes at 50 C. and there is now added to it the other half of the silver halide-sediment together with another 100 ccms.-of a ammonia solution. The mixture is kept further minutes at 50 C. under continuous stirring and the ammonia still present therein is neutralized with citric acid, until the emulsion shows only a very slight alkaline or a od remain unchanged. This general idea consists therein, that while the emulsion is being prepared, and more especially while it is being diadding to the em ulsions containing'substancessuch as ammonia, which further the aging progested, there is slowly fed to the growing silver halide grain fresh, if possible chemically pure silver halide. This can he realized by gradually cess, during this process further quantities of washed-out silver halide having a finer grain and eventually of further substances which further the aging process, such as ammonia. Inthis process the finer grained silver bromide'is dissolved by the ammonia present in the emulsion and now recrystallizes on the larger grains of silver halide already present in the emulsion, whereby the size of these grains is gradually increased.

By proceeding in the manner described, I am enabled to prepare peptisation emulsions of a relatively high order of grain size which are more sensitive to the action of light than the emulsions of ,a similar order of grain size produced according to customary methods, and further to simplify considerably the manufacture.

' substances Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

'1. The method of aging photographic peptisation emulsions which comprises mixing sedimented silver halide, which has been freed from adhering substances and emulsified in a liquid binder, with another portion of sedimented silver halide also freed from adhering substances, which has a finer grain than the aforesaid emulsified silver halide and causing the mixture to get at a suitable temperature in the presence of a substance adapted to promote the aging process.

2. The method of aging photographic peptisation emulsions which comprises mixing sedimented silver halide, which has been freed from adhering substances and emulsified in a liquid binder, with another portion of sedimented silver halide also freed from adhering substances and emulsified in a liquid binder which portion has a finer grain than the aforesaid emulsified silver halide and causing the mixture to age at a suitable temperature'in the presence of a substance adapted to promote the aging process.

3. The method of aging photographic peptisa: tion emulsions which comprises mixing sedimented silver halide, which has been freed from adhering substances and emulsified in a liquid binder and aged therein, with another portion of sedimented silver halide also freed from adhering substances, which has a finer grain than the aforesaid emulsified silver halide and causing the mixture to age at a suitable temperature in the presence of a substance adapted to promote the aging process.

4. The method of aging photographic peptisation emulsions which comprises mixing sedimented silver halide, which has been freed from adhering substances and emulsified in a liquid binder and aged therein, with another portion of sedimented silver halide also freed from adhering and emulsified in a'liquid binder which portion has a finer grain than the aforesaid emulsified silver halide and causing the mixture to age at a'suitable temperature in the presence of a substance adapted to promote the aging process.

5. The method of aging photographic peptisation emulsions which comprises mixing .sedimented silver halide, which has been freed from adhering substances and emulsified in a liquid binder, with another portion of sedimented silver halide also freed from adhering substances, which 35 has a finer grain than the aforesaid emulsified silver halide and causing the mixture to age at a suitable temperature in the presence of ammonia.

6. The method of aging photographic peptisation emulsions which comprises mixing sedimented silver halide, which has been freed from adhering substances and emulsified in a liquid binder, with another portion of sedimented silver halide also freed from adhering substances, and emulsified in a liquid binder which portion has a finer grain than the aforesaid emulsified silver halide and causing the mixture to age at a suitable temperature in the presence of ammonia.

7. The method of aging photographic peptisation emulsions which comprises slowly and gradually mixing sedimented silver halide, which has been freed from adhering substances and emulsified in a liquid binder, with another portion of sedimented silver halide also freed from adhersubstances, which has a finer grain than the aforesaid emulsified silver halide and causing the mixture .toiage at a suitable temperature in the presence of a substance adapted to promote the aging process.

8. The method of aging photographic peptlsation emulsions which comprises slowly and gradually mixing sedimented silver halide, which has been freed from adhering substances and emulsifled in a liquid binder, with another portion of