What is the Production Process of Photosensitive Emulsion?

• Posted by Chao Han May 12, 2022 Filed in Business #  #Photosensitive Emulsions  68 views
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  The production process of photosensitive emulsion directly affects its performance such as sensitivity, contrast and resolution. The raw material specifications and reaction conditions (temperature and time, etc.) must be strictly controlled. Any slight changes will cause changes in the performance of the photosensitive emulsion. In the production process of photosensitive emulsion, in addition to liquid preparation, from the beginning of emulsification to the end of preparation, it must be carried out under a safety light in a dark room. The brightness of safety lights (usually red lights) must also be strictly controlled. The robot operation is realized, and the whole process can be carried out in complete darkness.

  The production of photosensitive emulsion is divided into four stages:

  ① "Preparation" The various raw materials used in the preparation of photosensitive emulsions need to be formulated into a certain concentration solution first.

  ②"Emulsification and physical maturation" First add the gelatin solution to the emulsification reactor, then add the silver nitrate solution and the alkali metal halide solution at the specified speed. Taking the silver bromide emulsion as an example, the following reaction occurs:

  

   

  Photosensitive Emulsions

  The silver bromide produced by the reaction of AgNO3+KBr─→AgBr+KNO3 is uniformly dispersed in the gelatin solution as tiny crystals. This process is called the emulsification process. The potassium bromide solution is first added to the kettle, and then the silver nitrate solution is injected, which is called the single injection emulsification process; the process of simultaneously injecting the silver nitrate solution and the potassium bromide solution into the reactor is called the double injection emulsification process.

  The silver halide crystallites generated in the emulsification process are too small, and stirring must be continued at a certain temperature to dissolve some of the crystallites. The supersaturation of the silver halide in the medium is used to make the crystallites continue to grow and reach a certain size. This process is the physical maturation process.

  ③"Sinking and precipitation washing" adopts polymer precipitator to make the photosensitive emulsion agglomerate and settle, and then wash with water to remove water-soluble salts. Frozen cut strips have been used for washing.

  ④　After the chemically mature photosensitive emulsion is washed with water, it needs to react with a small amount of chemical sensitizer for a certain time at a certain temperature, so that extremely tiny photosensitive centers are generated on the surface of the silver halide crystallites, so that the sensitivity can be greatly improved. improve. This process is called the chemical maturation process. Commonly used chemical sensitizers include sulfur compounds and precious metal salts. After the chemically matured photosensitive emulsion is condensed, it is stored in the cold storage, and then heated and melted when necessary, and some photosensitive emulsion additives are added, and then the photosensitive material can be prepared by coating.

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