Effects Of Toners And Photocalysts On Photothermographic Imaging Material System Based On Silver Benzotriazole

In recent year, significant advances were made in technology of photothermographic imaging materials (PTG), and wide application was realized in medical films fields. However, there were still some problems need to be improved, such as low sensitivity of PTG materials and so on. In order to solve the problem of low sensitivity of PTG materials, another kind of silver salt differed from long chain silver carboxylates, silver benzotriazoles, was used as silver sources to construct the hydrophilic PTG materials with polyvinyl alcohol (PVA) as binder. We studied the influence factors, such as toners/development promoters and light capturing photocatalysts, in the photothermographic imaging materials based on silver benzotriazole as silver sources. The main results were summarized as follows:1. Effects of phthalic acid(H2PA) as toners on silver benzotriazole photothermographic imaging materials. Phthalic acid (H2PA) promoted the development of photothermographic imaging system based on silver benzotriazole as silver source. The results indicated that the positive ion (H+) of H2PA decreased the value of pH in the system, imaging activity of developer and the capability of H2PA combined with silver ions; the negative ion (PA2-) of H2PA created the intermediate with silver benzotriazole and the intermediate carried silver ions during the thermo-imaging process.2. Effects of phthalazine(PHZ) as toners on silver benzotriazole photothermographic systems. The results indicated that the development of silver benzotriazole materials was promoted by the introduction of phthalazine (PHZ), and the promotion was strengthened with increasing the amounts of PHZ. The cooperative promotion of PHZ and H2PA was better than that of single PHZ. The promotion of PHZ increased with increasing the pH of the silver benzotriazole emulsion constructed from phthalazine/phthalic acid (PHZ/H2PA) toner system. The analysis data implied that a silver complex, which was supposed to be easy to transmit silver ions to development center, produced by PHZ and silver benzotriazole. The above silver complex was non-fixed structure crystal and did not affect the thermal performance of silver benzotriazole.3. Influences of nicotinic acid as a new toner on silver benzotriazole systems. The results indicated that the development of silver benzotriazole materials promoted by the introduction of nicotinic acid as a new toner. The promotion of nicotinic acid increased with increasing the pH of the silver benzotriazole emulsion. The results showed that the best promotion of nicotinic acid could be obtained in the case of the mol ratio of nicotinic acid to silver benzotriazole 0.1 and value of pH in emulsion about eight. The analysis data implied that the silver complex produced by nicotinic acid and silver benzotriazole. 4. Effects of thioureas compounds as auxiliary ligands improving the solubility of silver benzotriazole. The results indicated that the thioureas that added into system all promoted the silver benzotriazole development and the promotion increased with the amount of thioureas. The thiourea substituted by electron donor groups as development promoters was more favorable. Tetrachlorophthalic acid(H2PACl4) and tetrachlorophthalic anhydride(TCPA) as antifoggants all decreased the minimum or fog density of silver benzotriazole system including tetramethylthiourea.5. Effects of AgX as photocatalysts on silver benzotriazole photothermographic imaging system. The results revealed that the in situ AgBr grains were formed in condition that NH4Br ball-milled with silver benzotriazole. According to KX series, Sensitivity of PTG films were improved in the descending order: KI>KBr>KCl. Ex suit formed AgX emulsion grains introduced into PTG construction was more favorable for improving the sensitivity of PTG films than in suit made AgX particles introduced by halogenating agent NH4Br. The improvement depended on emulsion grains sharps and sizes, and the influence improved in that descending order: tabular grain > octahedral grain > cubic grain.