In the preceding paper, the photosensitivity of electrophotographic layer consisting of polymer and β-metal-free phthalocyanine (βH₂Pc) doped with electron acceptors was discribed to be improved. In this paper, the relation ship between the sensitivity and the electron affinity of quinone and fluorenone type dopants was discribed. The sensitivity showed a sharp maximum at the affinity of 1.19 eV and stronger acceptors caused a rapid decrease in the charge acceptance. The highest sensitivity was obtained with 2, 4, 5, 7-tetranitro-9-fluorenone, but this dopant also caused a severe fatigue of the photoreceptor by undesirable be reduced by accumulation of charges during the corona charging. This fatigue effect, however, could co-doping of a weak electron donor, pyrene.

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The relation between toner charge and toner image transfer ratio has been investigated both theoretically and experimentally. Theoretical analysis shows that a toner particle receives two forces. One is the coulomb force between toner charge and transfer corona charge, and the other is the image force of toner. The total electrostatic force which a toner particle receives is a mathematical sum of these two forces, and is expressed in a quadratic equation of toner charge, having maximum value at the optimum toner charge. It is reasonable to think that the greater electrostatic force in the direction of the transfer material caused greater transfer ratio. Thus, there exists optimum toner charge to mass ratio which gives maximum transfer ratio.
In the experiment, one component magnetic toner image was charged by precharge corotron to control its toner charge to mass ratio. The experimental results show that the toner transfer ratio greatly depends on the toner charge to mass ratio, and the maximum transfer ratio of 80% is achieved at the toner charge to mass ratio of about 14 μC/g, these proving theoretical results.

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Electron transfer at tunnel electrode/excited dye molecule interface was theoretically discussed. It was clarified that the acceptor state density of the excited dye molecule can be directly determined by analyzing the tunnel photocurrent-voltage characteristic.

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Studies have been made of spectroscopic and photophysical properties of poly (N-vinylindole) (PVI) which has been patented as a photoreceptor material in electrophotography. Spectroscopic data have proved that PVI prepared by the radical polymerization of N-vinylindole contains the indoline moiety formed during the polymerization process. Unique photophysical processes have been found for PVI which involve both singlet and triplet energy transfers that occur, respectively, to the extent of 100% between the indole and indoline chromophores. The occurrence of the 100% double energy transfers is concluded as due to the proximity effect of pendant chromophores along the polymer chain. The results indicate that PVI should be used as an elecron transport material rather than a hole transport material since the indoline group, which is more electron-donating than the indole group, will act as a deep trap of holes. It is suggested that poly (N-vinyl-2-methylindole) which does not contain the indoline group should be used for the hole transport.

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