抄録
Light decay characteristics of negative charge on the film of polyvinylcarbazole and polystyrene with several heterocyclic photoconductive compounds have been studied. The heterocyclic compounds used are I-VIe (see the formulae).
The experimental arrangement and the preparation of photoconductive films are shown in Fig. 1. Decay curves like those in Fig. 2 (a) did not give any linear relation when the logarithm of the surface potential (V) was plotted versus time (t) (Fig. 2 (b)); Iog V versus t1/2 plot however, gave a linear relation (Fig. 3). The value a in the equation V=V0e-αt1/2 was therefore used as the decay constant. The value α was found to be proportional to the light intensity I (Fig. 5) .
The increase of decay constant when illuminated with light IA (Fig. 4) was given by is αA (α with filter D 25) minus αd (dark decay constant). The decay constant αA0 inherent to the light of this wave-length region was therefore αA0=(αA-αd)/IA. The increase of decay constant when illuminated with light IB (Fig. 4) was given as αB= (αIII-αd) - (αIV-αd), where αIII and αIV were α values when filters VY 39 and VY 50 were used, respectively (Fig. 4) The decay constant αB0 inherent to the light of this wave-length region was therefore αB0=(αB-αd)/IB. Values of αA0 and αB0 are listed in Table 1 and 2. As we are interrested only in the relative values of αA0 and αB0 in calculation, the value of IA is assumed as I, the value of IB being then 3.
As is evident from Table 1, polystyrene itself was not sensitive to light, When total light was used, pyrazoline derivatives and tetrahydroimidazole derivatives in polystyrene showed higher α values than others.
αA0/αB0 values are higher in compounds II, IV and III, being 22, 8 and 4 respectively. As is shown in Figs. 6 and 7, the light absorption by these compounds is small in the wave-length region of IB, values of αB0 being consequently small, increasing the values of αA0/αB0.
As is shown in Fig. 8, decay constant α decreased with increasing film thickness.
αA0/αB0 was 7.7 for polyvinylcarbazole, decreasing down to 2. 3 with increasing amount of pyrazoline VIb. As is shown in Fig. 10, the light absorption of the film increased in the longer wave-length region when pyrazoline was added to polyvinylcarbazole, increasing αB0 and decreasing αA0/αB0.
When pyrazoline was added in various amount to polyvinylcarbazole and illuminated with the total light, α values increased first a little then decreased to a minimum and again increased up to a fairly high value (Fig. 9). (View PDF for the rest of the abstract.)
