Photocarrier generation, transport, and trapping in two-1ayer organic photoconductors consisting of a carrier generation layer (CGL) and a transparent carrier transport layer (CTL) were studied by photoacoustic spectroscopy, time-of-flight (TOF) photoconductivity measurements, xerographic discharge measurements, and thermally stimulated current (TSC) measurements. The injection and trapping processes of holes at the CGL/CTL interface were evaluated from photoacoustic spectroscopy and xerographic discharge measurments. The drift mobility of holes in the CTL and the activation energy for charge transport were obtained from TOF photoconductivity and TSC measurements. The trapping lifetimes of holes in the CGL and the CTL were measured by the delayed-field and the interrupted-field TOF methods, respectively. From experimental results, we systematically discuss the photoconduction dynamics in two-layer organic photoconductors; (1) the photocarrier generation in the CGL and the trapping of holes at the CGL/CTL interface and (2) the mechanism of the buildup and the decay of the residual potential.

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Substituent effects on the drift mobility of N, N, N', N'-tetraarylbenzidine derivatives have been investigated to obtain a molecular design guide to enhance drift mobility of the hole transport materials for organic photoconductors. In the case of introduction of alkyl group into N-substituted phenyl moiety, substitution at ortho or metha-position had little effect on drift mobility, while substitution at para-position doubled the drift mobility. These effects may be interpreted in terms of delocalization of electron density by σ-π conjugation and inhibition of the delocalization by steric hindrance. On the other hand, introduction of alkyl group into the central biphenyl skeleton at 3-position, which is ortho-position against nitrogen atom, caused to increase the drift mobility by a factor of two; that is contrary to expectation from the result mentioned above. The effect of alkyl substituents on drift mobility was found to be linearly related to the product of substituent constants, which are the increasing ratio of the drift mobility of the respective substitution position obtained empirically.

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In the “One Drum Color Superimposing Process”, a full color image is formed by sequential processes of charging, exposing and developing of each color component directly onto the photoconductor. In this report, the electrostatic effect of the toner layer over the latent image on the image formation is studied. There are two effects mainly. One is the toner charge which cannot be erased by light exposure, and the other is the dielectric properties of the toner which covers the latent image on the photoconductor. High toner charge causes the rise of the exposed potential of the photoconductor, which prevents superimposing development on the preceding toner image. Moreover, high toner charge causes lowering effect of the surface potential at the corona charging process. The dielectric properties of the toner affect the resolution of the succeeding development because of its shielding effect of the charge pattern. It becomes clear that the toner charge must be sma11, and the thickness of the toner layer must be thin in this color process.

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We have investigated on the photoconductivity of metal-free phthalocyanine ultrafine particles prepared by the gas evaporation method. Two kinds of phthalocyanine ultrafine particles were obtained. Electron micrographs indicate that the crystallites are acicular, typically 500 Å and 4000 Å long each other and the thickness of pigments were much the same as 150 Å thick. Crystal form of ultrafine particles were α type by the measurement of spectral absorption and X-ray diffraction spectra.
The photoreceptor composed of metal-free phthalocyanine ultrafine particles and binder resin shows the high charge acceptance under the positive corona charging. The photoreceptor containing of a large size of metal-free phthalocyanine ultrafine particles shows higher photosensitivity than that of a small size of particles.

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Determination of localized-state distributions in amorphous semicondutors is of fundamental importance from the viewpoint of practical as well as scientific interest. In this paper the construction of a simple computer controlled spectrometer is described for modulated photocurrent spectroscopy of amorphous semiconductors. The modulated photocurrent technique is based on the analysis of the phase shift between a sinusoidally modulated excitation light and its inducing photocurrent, and a broad range of the localized states can be obtained by this method. The applicability of the spectrometer has been experimentally demonstrated in a prototypical amorphous chalcogenide, amorphous As₂Se₃ thin film.

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In the dye transfer printing processes, 10wering sublimation temperatures of transfer dyes improves the sensitivities of dye transfer ink, but decreases the stabilities of recording images. To keep both the high sensitivities and the good stabilities, it is generally said that introduction of the electron-acceptable materials to recording media is effective, because the dye and the medium resin form a complex.
We investigated the relation between the stabilities of the images and the equilibrium constants of complex formation of dye and several kinds of medium resins. It is revealed that the stability of images increases with the increase of equilibrium constants. The complex formation is effective not only in suppressing resublimation of dyes from resin medium but also in preventing the diffusion of dyes in the medium.

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