In order to elucidate the difference of ionization potential (lp) in various sample forms, the novel atmospheric photoelectron emission analysis has been applied to phthalocyanines, which are widely used as a charge generation material of OPC photoreceptor for electrophotography. The Ip of metal-free phthalocyanine was found to be classified as (1) 5.00-5.10 eV in thin evaporated films, (2) 5.20 eV in powder, (3) 5.38 eV in evaporated films after annealing as well as in dispersion films. As increasing the film thickness or being homogenized the thin film surface by annealing, the Ip value becomes larger approaching to that of dispersion films. Such variation of Ip seems to reflect the surface characteristics of each sample, and is discussed in terms of the degree of structural disorder.

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The drift mobility and the carrier generation efficiency were determined by the analysis of the transient response of photoinduced discharge and the value of the surface potential drop when the photoreceptor was exposed to a flash lamp, respectively.
The dependence of drift mobility on the concentration of CTM and the electric field dependence of the carrier generation effciency for x-type metal-free phthalocyanine/Hydrazone derivattive photoreceptor were investigated using XTOF technique. The carrier transport in the molecular doped polymer layer and the carrier genration in x-type metal-free phthalocyanine pigment were fitted to hopping model and onsager theory, respectively. This measuring method was valuable for understanding the electrophotographic properties of organic photoreceptors.

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Electrolytic printing ink has been developed based on a polymeric gel. This polymeric gel ink consists of poly(vinyl alcoho1)(PVA)partially crosslinked with borax, carbon black as a pigment, and water. It has the nature of gel to sol transition with pH variation. During to the transition its viscosity decreased.
There are several techniques to change pH such as the addition of acidic or alkali and the application of electric voltage. However, adding chemical substances changes the composition of the gel ink. Consequently, electric voltage was chosen to vary pH. When the electric voltage was applied to the gel ink, an electrochemical reaction occured on the gel ink so that pH became acidic at the anode and viscosity of the gel ink was reduced enough to adhere to a paper. Application of rectangular pulse voltage caused the same phenomenon as a constant voltage.
A Printing apparatus was also designed. Polymeric gel ink with electric conductivity 4.0 × 10^-3 Ω^-1cm^-1 was used. The gel ink was coated on the surface of a metal roller. Then an electric voltage was applied to it by electrodes corresponding to picture elements. Image pattern was formed on the surface of the gel ink and then it was definitively transferred to a paper. When electric voltage was not applied to it, the surface did not show any change.
Polymeric gel ink could offer resolution of at least 200 dots per inch (dpi). Image density was fully controllable from 0.05 to 1.5 as optical density by application of an electric voltage of 3-12 V. Printing speed was 22mm/sec.. An advantage of this printing system is that the polymeric gel ink not only acts as an ink but also as the support and the carrier of the ink itself.

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In the reversal development process, the fundamental characteristics of insulating magnetic toners were investigated for a diode laser printer with a organic photoreceptor.
In the application of the contact development, the method of carrying the toners towards the photoreceptor is an important factor to obtain good image quality. And the toners have essentially positive and/or negative charge from inter particle triboelectric charging. In the development process, however, the toners vary in electrostatic charge from induction charging to triboelectric charging due to the existence of charge control agent of toners. These results were confirmed by the experiments with ferrite carriers being added to the toners.
We found that the similar two-components development process using the triboelectric magnetic toners and the ferrite carriers could realize good image quality and high print durability. It was applied practically to the diode laser printer and has succeeded as a new two-components developing method.

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Amorphous silicon (a-Si) photoreceptors have been fabricated by the conventional glow-discharge method without deteriorateng their electrophotographic properties at the deposition rate (R_D) of 3-17 μm/hr with increasing density of active species in SiH₄-Ar glow-discharge plasma under controlling decomposition efficiency of SiH₄ (η_SiH4) and secondary reactions of the active species with SiH₄ molecules. The decomposition efficiency of SiH₄(η_SiH4) has been measured by mass spectrometry, and the relations have experimentally been derived between η_SiH4, and deposition parameters such as electric power (R_f) gas pressure (P) , distance between R_felectrode and Al substrate (l) and average residence-time (τ_r) of SiH₄-Ar gas in the glow-discharge volme (V) . Furthermore, semiempirical formulas which relate R_D with η_SiH4, SiH₄ flow rate (F _SiH4), Ar flow rate (F_Ar) and a ratio (r/<>il) (r: radius of a cylindrical substrate) have been derived from a consideration of diffusion process of active species produced by dissociation reactions of SiH₄ in the plasma, and successfully applied to a case of η_SiH4=0.63 in the range of 3 ≤ R_D ≤ 17 μm/hr, the formulas being
R_D=0.51·η_SiH4F_SiH4√[(1+2r/l)/{FRr+(1+0.83η_SiH4)F_SiH4}]
at R_f= 1.15 × F_SiH4^1.00 and Pl= 2.0 Torr·cm.

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