خطوات صناعة الطبقة الحساسة ١-a .. كتاب الإضاءة والفلم

Steps of manufacturing the sensitive layer.

The sensitive layer is made according to the following short steps: (Fig. 35)

1- Dissolve the gelatin and add the salts:

The industrial stage begins by placing the gelatin in a double wall boiler with hot water to dissolve the gelatin, then the required amount of halogen alkali is added, then a silver nitrate solution is allowed to be added. This solution is not added at once with the gelatin and other salts, but rather each is added to the other according For a number of proportions and according to a specific timing for each salt. Then the mixture (which is then known as the broth) is left to first ripen

What is meant by the word “ripening” is the period that the mixture remains at a certain temperature until the sensitivity of the emulsion reaches the required amount. With increasing maturity, the speed of sensitivity increases. At this stage, the size of the grains of silver salts is large.

2- Solidification: It is the stage that follows the first maturation, and it takes place in flat basins in which cooling means are prepared so that the gelatin acquires a degree of hardness that guarantees the performance of the next process.

3- Shredding: In this last process, the gelatin is cut into very small pieces (such as noodles), which may be, for example, square in shape, the length of which is no more than the length of a finger, and its thickness is less than the thickness of a thin pencil. This process takes place in a large cylindrical container coated with silver or silver. The stainless steel has holes at the bottom (like a strainer), and by pressing on it from the top, the gelatin comes out. These holes, then cut into extremely small pieces.

4- Washing: In the washing stage, the potassium nitrate salt and other reaction products dissolve, and the silver halogens remain because they are not soluble in water. The degree of intensity of washing depends on the form of chopped gelatin pieces. It is not desirable that any of the aforementioned salts remain in the sensitive emulsion after washing.

E - The process of second ripening: Second Ripening: Then the gelatin is renewed by raising its temperature, and it remains like this for a specific period depending on the speed of sensitivity that we desire for the sensitive layer and on some other characteristics that distinguish the sensitive layers, such as the contrast feature and the size of the grains. At this stage, other substances known as Ripening additives, i.e. ripening additives, are added, and they do not affect the size of the granules, but they do increase the sensitivity. At this stage, a small amount of Gold Salt is added, as its effect appeared to greatly increase the speed of sensitivity, while not Increasing the size of the grains, and it would seem how small this quantity is if we know that 1 gram of gold can be obtained from Processing every 100,000 Roll film D.

The rate of sensitivity of the sensitive dough depends on several factors, which we describe as follows:
(a) The temperature of the mixture.

(b) The ratio of the amount of silver salts to the amount of gelatin.

(C) The type of silver salts and the type of gelatin.

(D) The degree of maturation of the mixture.

(e) Adding some materials that help ripening, such as adding ammonia.

Likewise, during the second curing stage, materials may be added that will prove the properties of the science, Stabilizer, so that the films have the ability to maintain their properties during their storage period. Fog. A compound of azaindolizines salts is currently added instead of potassium bromide, which was added in the past for this purpose... In the following table, we show the results of industrial experiments to increase the life of the film and store it by raising the temperature of the sample to 50 degrees Celsius for a period of ten days. The experiments were conducted by ORWO film factories (1) Fog density appears from it (2) in the fresh state and after raising the temperature.

The sensitive layer, which does not prove its characteristics, is Non-Stabilized emulsion, after rendering (and without being exposed to light at all) to a density of 205 in the darkest parts of the negative image.
(For example, white clouds). If we were to divert between this result and that which we would obtain if we used the new stabilization agent mentioned above, we would find that the increase in fog (resulting from an increase in the storage temperature) becomes a small increase to the extent that it can be almost neglected. The results that come after adding the new stabilizing salt It is superior to that obtained from the use of potassium bromide, noting that this last salt also leads to a decrease in the sensitivity of the film.

6- The second solidification:

Then the sensitive emulsion is cooled to solidify to be preserved in cold rooms, and left like this until the need for coating it on the required support.

However, until this moment, the emulsion industry has not reached its final stages, as it still requires new additions that will give it its final properties, and these additions do not take place until directly before starting the final coating.

7- The last additions prior to coating the sensitive layer on the support:

This process begins with re-melting the gelatin as soon as it is taken out of the cold chambers. After it melts, the required materials are added. Additives perform the following functions:

(a) Substances that affect the spectral sensitivity, which are mostly sensitizing dyes that control the sensitivity of the film to colors (and we will talk about it again in this section regarding the study of the spectral sensitivity of films).


(B) Materials that increase the hardness of gelatin to resist high temperature Hardeners.

(h) Materials that resist the influence of bacteria-sensitive gelatin.

(D) other materials to help the gelatin to spread more widely on the support.