The effect of chemical sensitization on the silver chlorobromide emulsion has been studied. The emulsion containing the 30 mole percent of silver bromide was prepared with inert gelatin. The sensitizers used were thiosulfate for sulfur sensitization, chlorauric acid (Au
+++) and aurothiocyanate (Au
+) for gold sensitization.
The experiments showed;
1. Little increase in sensitivity was obtained by gold sensitization, considerable increase by sulfur sensitization, large increase by sulfur-gold sensitization.
Sulfur sensitization gave the maximum sensitivity in the 2nd ripening process. No difference between Au
+++ and Au
+ was observed.
2. The rate of development of a sulfur sensitized or of a sulfur-gold sensitized emulsion was greatly increased by hydroquinone and glycin, a little by metol, none by N-diethyl-p-phenylenediamine. The presence of silver sulfide and silver-gold-sulfide seemed to make the grain surface positive after exposure.
3. p-Benzoquinone and bichromate were used as oxidizing agents for latent images and sensitivity centers. The latent image obtained by gold or gold-sulfur sensitization was more resistant to oxidation than that obtained by sulfur or non-sensitization. The sensitivity centers were more stable than the corresponding latent images. The sensitivity centers on gold or non-sensitisation were more easily oxidized than that on sulfur sensitization.
From these results we discuss that silver sulfide, gold sulfide and silver-gold-sulfide act as a positive hole trap, gold ion acts as a photoelectron trap.
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