Localization of Latent Image in Heterophase AgBr(I) Tabular Microcrystals

Transcription

1 Interntionl ymposium on ilver Hlide Technology Locliztion of Ltent Imge in Heterophse AgBr(I) Tulr Microcrystls Elen V. Prosvirkin, Aigul B. Aishev, Timothy A. Lrichev, Boris A. echkrev Kemerovo tte University, Kemerovo, Russi Astrct Processes of the formtion of heterophse microcrystls with AgBr/AgBr(I) structure nd the correltion of their structure with photogrphic properties of emulsion lyers prepred on their sis hve een investigted. In the course of the experiment, pbr of the synthesis of initil emulsions, the temperture of physicl ripening of emulsion microcrystls nd the lgorithm of incorportion of iodide vried. The reserch hs llowed us to determine the prmeters of the crystlliztion resulting in the formtion of microcrystls with improved photogrphic chrcteristics. When creting the locl zones sturted with iodide, the sensitivity centers nd the ltent imge re in the susurfce re. The nlysis of our experimentl dt enles us to compre the efficiency of these methods s to their photogrphic chrcteristics nd to evlute the prospect of comining these methods. Experiment The study of the processes occurring when introducing iodide in tulr grins is complicted y very smll sizes of these grins. In order to model these processes in more convenient conditions we crried out n experiment on the influence of silver iodide on lrge crystls of silver romide, minly of hexgonl hit (5 microns). Opticl microphotos of initil crystls (а) nd the crystls ttcked y the potssium iodide solution with vrious concentrtion (, c, d, e) re presented in Fig.. Introduction One of the importnt prolems in modern photogrphic prctice is to increse photogrphic speed of silver hlide microcrystls. The increse in the efficiency of photoprocess is known to e prole when prepring photogrphic lyers on the sis of AgBr/AgBr(I) heterophse tulr microcrystls with lterl shell which llow one to concentrte photolytic silver in the microcrystl core. However, the preprtion of these crystls is rther difficult due to the chnge of optimum vlues of crystlliztion prmeters depending on the hlide structure of the lterl shell. According to the ptent literture, perspective opportunity of increse in photogrphic speed is to crete extended defects of crystlline lttice in susurfce re of AgBr microcrystls y incorporting the solution of potssium iodide during the growth of microcrystl efore the totl quntity of silver romide is dded. The formtion of disloctions is cused y the formtion of structurl defects on the oundry when cocrystllizing silver romide nd silver iodide. Crystls with similr defects demonstrte the increse in the efficiency of photoprocess. However, the mechnism nd the kinetics of the process of the growth of similr microcrystls nd techniques for chieving high sensitivity of emulsions remin unknown.

2 Interntionl ymposium on ilver Hlide Technology c d Experimentlly we determined the optimum concentrtion of iodide ions, responsile for concentrting silver iodide on silver romide without sustrte tulr grins eing dissolved (Fig. ()). An importnt fctor to e tken into ccount is the durtion of the interction of silver iodide nd silver romide. This interction should lst min. to ensure the concentrting of silver iodide without microcrystl eing destructed. Thus, the stte of grin surfce depends on the concentrtion of the dded potssium iodide solution nd the durtion of its effect on sustrte crystl. Model experiments llowed us to develop the technique of the synthesis of emulsions with heterophse tulr grins with zones of the incresed content of iodide. ifferent wys of dding silver iodide into the structure of tulr grins were tested. To e le to compre vrious techniques of the introduction of iodide, we crried out the initil stge of the synthesis in ll the cses in the sme wy. The weight rtio of silver romide nd silver iodide for ll the types of emulsions ws the sme. At the first stge fine AgBr emulsion ws prepred y the method of doule-jet crystlliztion. To otin core tulr grins, physicl ripening of fine emulsion t high temperture nd in the presence of solvent ws crried out efore initil microcrystls disppered. An verge equivlent dimeter of the resulting tulr microcrystls is,78 microns, the vrition fctor - 8 %. Emulsion A To crete the zone with the incresed content of silver iodide, M potssium iodide ws dded into the emulsion contining AgBr core tulr grins with pulse method. Then the microcrystls were uilt up. The microphoto of col replics of the resulting tulr grins re presented in Fig. (). As seen, tulr grins re, minly, of hexgonl hitus. Emulsion B To synthesize emulsion B, the technique of creting the zone enriched in iodide, consisting in lternting pulse introduction of potssium iodide nd potssium thiocynte ws used. Then the microcrystls were uilt up. The microphoto of the resulting tulr microcrystls is presented in Fig. (). As seen, the introduction of KCN during the growth of AgBr tulr microcrystls results in prtil dissolution of crystls. Figure. A microphoto of modeled tulr grins: - C (KI) = mol/l, - (KI) = 5* -5 mol/l, c - (KI) = 5* - mol/l, d - (KI) = 5* - mol/l, e - (KI) = * - mol/l. As seen from Fig. (e), the increse in the concentrtion of silver iodide in the system results in the dissolution of silver romide tulr grins, while hour contct (or more) of silver iodide with lrge tulr grins results in the destruction of these crystls (Fig. (d)). e Emulsion C To synthesize emulsion C, the technique of creting the zone enriched in iodide, y stepwise formtion of the AgBr(I) % lterl shell nd pulse introduction of iodide ws used. Then the microcrystls were uilt up. The microphoto of the resulting tulr microcrystls is presented in Fig. (c). The comprison of Fig. () nd (c) enles us to see tht simultneous uilt-up of the AgBr(I) lterl shell nd pulse introduction of iodide results in the verge grin size decrese nd the coefficient of vrition of projected grin sizes increse. Therefore, it ws necessry to investigte the

3 Interntionl ymposium on ilver Hlide Technology influence of the wy of introducing KI on crystllogrphic nd grnulometric chrcteristics of AgBr/AgBr(I) grins. Emulsion To synthesize emulsion, the technique of creting the zone enriched in iodide y the formtion of lterl shell AgBr(I) % ws used. Then the microcrystls were uilt up. The microphoto of the resulting tulr microcrystls is presented in Fig. (d). As seen, tulr grins of the emulsion hve hexgonl nd tringulr hit. c d Figure. Microphotos of AgBr/AgBr(I) tulr grins of emulsions with zones of the incresed content of iodide: emulsion A, - emulsion B, c - emulsion C, d - emulsion. Thus, the techniques of the synthesis of photogrphic emulsions with different wys of introducing iodide developed y the present uthors llowed us to otin heterophse tulr grins with similr crystllogrphic chrcteristics which mke it possile to estimte photogrphic chrcteristics of emulsion lyers prepred on their sis t the next stge. For this purpose photogrphic emulsions of ll types undergo sulfur-plus-gold sensitiztion nd the sulfur-plusgold sensitiztion in the presence of potssium thiocynte. The introduction of potssium thiocynte ws found out to differently influence photogrphic chrcteristics of these emulsions. For A nd B emulsions, chemicl sensitiztion in the presence of potssium thiocynte results in the chnge of the shpe of chrcteristic curve (Fig. ( ) nd ()).

4 Interntionl ymposium on ilver Hlide Technology,, -, -,,,5, -, ,,5, -,5 -, -,5,8,6,,, -, -, Figure. Chrcteristic curves of emulsion lyers on the sis of emulsion A (), emulsions B (): - n unsensitized emulsion; 8, 6 - chemicl sensitiztion in the presence of potssium thiocynte;, 8 - chemicl sensitiztion without potssium thiocynte. When creting the locl zones sturted with iodide, in the structure of grins, the sensitivity nd the ltent imge centers re supposed to e locted under the surfce. The introduction of potssium thiocynte efore the incorportion of chemicl sensitizers llows these centers to pper on the surfce, thus incresing the efficiency of photoprocess. For C nd emulsions inverse dependence (Fig. () nd ()) is oserved. Chemicl sensitiztion in the presence of potssium thiocynte results in the decrese of the vlue of opticl density of drkening. Chemicl sensitiztion in the presence of potssium thiocynte results in the decrese of the vlue of opticl density of drkening. The concentrtion of sodium thiosulfte ws vried for the optimiztion of the chemicl sensitiztion process in the course of further experiments. Figure. Chrcteristic curves of emulsion lyers on the sis of emulsion C (), emulsions (): - n unsensitized emulsion; 5, 6 - chemicl sensitiztion in the presence of potssium thiocynte; 55, 6 - chemicl sensitiztion without potssium thiocynte. The increse in the concentrtion of sensitizer for A nd B emulsions cn e sid to result in n essentil increse in photogrphic speed (criterion,85). Further increse of thiosulfte concentrtion results in the growth of fog opticl density. C nd emulsions underwent sulfur-plus-gold chemicl sensitiztion in the presence of potssium thiocynte. A significnt growth of the fog ws oserved with increse in the concentrtion of sodium thiosulfte. ulfur-plus-gold chemicl sensitiztion without potssium thiocynte with increse in the concentrtion of sodium thiosulfte results in n insignificnt chnge of photogrphic speed, nd the fog opticl density increses considerly. The est sensitometric chrcteristics for photolyers on the sis of emulsion A otined y the present uthors re given in Fig.5.

5 Interntionl ymposium on ilver Hlide Technology 8 6 When incresing the concentrtion of ye, the photogrphic speed of emulsion C considerly grows (criteri, nd,85). The fog opticl density decreses from,6 up to,5. The further increse in the concentrtion of the dye is ccompnied y photogrphic speed decrese nd fog opticl density increse (Fig. 7.). A B C 5 (,85) (,) C[ye ], x, mol/mol Ag (,85) g(,) A B C mx γ Figure 5. Optimum photogrphic chrcteristics of the emulsions under investigtion. pectrl sensitiztion with ye which hs mximum sorption t λ=57 nnometer ws crried out for three types of photogrphic emulsions (A, C, ). The structurl formul of the dye H CO N + ( CH ) O CH - C H 5 C HC N - ( CH ) O OC H + HN C 5 H 5 The fog opticl density ws found out to decrese from, up to, nd photogrphic speed to increse from 5 up to due to the dsorption of the dye on the emulsion A grins (Fig. 6.). 5 5,,6 C [ye], x,m ol/ m ol Ag (,85)= (,)= γ Figure 6. Photogrphic speed nd fog opticl density vs. the concentrtion of ye (for the emulsion ).,,,,, Figure 7. Photogrphic speed nd fog opticl density vs. the concentrtion of ye (for the emulsion ). The photogrphic speed for emulsion fter the dye is dded increses lmost times s much. The fog opticl density increses too. When incresing the concentrtion of the dye, the fog level is reduced up to certin vlue (Fig.8). 5 6 C [ye ], x, mol/mol Ag (,85) g (,) 5 Figure 8. Photogrphic speed nd fog opticl density vs. the concentrtion of ye (for the emulsion ). Thus, grins with the zones of the incresed contents of silver iodide possess numer of similr properties: they esily fog ) when ttcked y potssium thiocynte, ) t higher concentrtions of sodium thiosulfte, they possessing higher photogrphic speed. The nlysis of our experimentl dt llows us to compre the efficiency of these techniques from the point of view of photogrphic chrcteristics, nd in ddition to it, to estimte the prospect of comining these techniques. Biogrphy Aigul B. Aishev ws orn in Pvlodr (Kskhstn) on July 9, 98. In he grduted from Kemerovo tte University, the Chemistry fculty. Now he is post-grdute of Kemerovo tte University, the Physics fculty. His field of reserch is mss crystlliztion processes of silver hlides, the uthor of scientific pulictions..