خطوات صناعة الطبقة الحساسة ٢-a .. كتاب الإضاءة والفلم

evenly or to facilitate the spread of highlighting solutions and their effect on the film at once and easily with Welting agents.

(e) If we are in the process of making color films, then “color problems” should be added to them (1) Color Couplers.

(8) Filtration: After mixing the sensitive dough with all these additives, it is filtered to get rid of any possible impurities and its temperature is adjusted to the extent that suits the process of coating the support with it.

9 - Preparing the support for coating: The support requires a special preliminary treatment to ensure that the sensitive layer sticks to it when! Coating, and this is done by means of an adhesive layer that is usually a mixture of gelatin and barium sulphate and is known as Baryta. Gilanina, and to it is attributed the bright appearance acquired by the delicate leaves.

10- The coating process: It is not - as many think - just a process of pouring the sensitive gelatinous liquid onto the support. Rather, the support (film or paper) rotates around a cylinder, and in this cycle it comes into contact with a container that carries the sensitive gelatinous liquid.
(As shown in Figure 136) It may be done by contacting the stent with another cylinder with a layer of this sensitive liquid on it (as shown in Figure 36-b). The thickness of the sensitive layer depends on the fluidity of the viscosity of the sensitive gelatinous liquid, its temperature, and the speed of rotation of the support roller, all of which require initial experiments to control the accuracy of the result and its suitability for the desired purposes.

11- Cooling: The films (which are the support and the sensitive gelatin on them) were passed through long low-temperature passages until the gelatin solidified on the surface of the support. We see in (Fig. 35 p. 105) all the previous stages that finally end with cutting sensitive papers and films according to the required standards. They were packed in boxes or cans after wrapping them in a special way that prevents them from being affected by light or weather factors.

Films with two layers of different sensitivity: Double Coated Emulsions:

Some films may be covered with two layers of different sensitivity, which are placed on the film support, in order to overcome the defects that result from excessive exposure to light by mistake. The upper layer is susceptible to light, while the lower layer resists this error and is affected only to a very small extent due to its low sensitivity. Thus, the negative image is acceptable and of medium density. In this way, too, it is possible to overcome the underexposure deficiency, as the fast-sensitive upper layer is sufficient to record the latent image in case of sufficient light.


Covering sensitive gelatin with a more solid layer: Over coating:

It is a means intended to protect the thin layer of gelatin from scratches that may result from wrapping films or otherwise. It also protects it from the adhesion of any sediment likely to be attached to the presenting or fixative solution, and it prevents possible scratches on the surface of gelatin as a result of its friction with the basins during the displaying operations.

Film Backing:

When the film is placed in the solution, the gelatin layer swells to a slight degree, and then expands as a result of its saturation with it. After the roll-out operations are finished. When the film dries, the gelatin layer shrinks from what it was first, while the support remains as it is without the liquids having any effect on it, and this leads to the film support curving inward if it is made of celluloid. In order to overcome this situation, sometimes a very thin layer of gelatin is placed behind the support on the other side of the sensitive layer, and its shrinkage coefficient is equal to that of the two surfaces, and the support remains flat.

Transfer of the sensitive gelatin layer from the support:

Some negative sensitive layers are prepared in a way that facilitates their removal from the original support and transferring them to another support (Transfer materials) if the matter calls for that. In order to achieve this purpose easily and proficiently, the following steps are followed in its preparation:

1- The hardness of the sensitive layer is increased.

2- A soft layer of insensitive gelatin is placed between it and the abutment, to facilitate its removal from above the abutment.

3- The upper surface of the sensitive layer should be treated with an adhesive substance, so that it sticks easily to the second support to which it is transferred.

Anti Halation Layer:

When a light ray falls on the surface of the film, it suffers from light reflections on the different shiny surfaces that make up the film (Fig. The optical halo can be overcome by preparing a radiation-absorbing layer known as the Anti-Halo Layer, sometimes called the Anti Halation Layer, and it is placed in one of the following two places:

(A) Between the bottom of the sensitive layer and the top of the support (in the place of the plane C, Fig. 38).

(B) Behind the pillar behind the flat (M and Figure 38), as shown in Figure 37, page 110.

The occurrence of the optical halo may be prevented by means of a gray support that absorbs the rays that reach it, as is the case in some 35 mm films. The anti-glare layer dissolves easily in the washing water prior to the start of image display operations, so it does not have any harmful effect on that.