In a layered photoreceptor with metal-free phthalocyanine (H₂·Pc) as the carrier generation layer (CGL), addition of electron acceptors to CGL was found to improve electrophotographic properties. The effect was clearly exhibited when aceptors whose electron affinities were between L1-L4eV were added to a H₂·Pc/acceptor dispersion-coated CGL in a concentration of about 10 weight percent. The charge acceptance did not affected, but the photo-carrier generation efficiency increassed as a result of the interaction probably between excited H₂·Pc and acceptor molecules and it raised the photosensitivity as much as 50%. Acceptors of affinity more than L5eV, however, increased the conductivity of CGL and consequently reduced the charge acceptance to an impractical level.
In order to assure a closer interaction between H₂·Pc and acceptor molecules, co-sublimated CGL films of H₂ Pc and 2,4,5,7-tetranitro-fluorenone (TeNF) were prepared in a vacuum chamber by the flash evaporation technique. The photosensitivity was further improved. The optimum concentration of TeNF in CGL was between 1 to 10 mol.%. The electrophotographic property was excellent. The initial surface voltage of 1000V was decayed to 500V by an exposure of 1.2 μJ/ cm². It was found that the addition of TeNF to CGL improved not only the initial discharge rate but also the electric field dependence of the decay process.

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In a negatively charged multi-layered photoreceptor, Al/metal-free phthalocyanine/hydrazone derivative in polyester, it was found that exposure to the carrier generation layer (CGL) from the AI electrode side gave an improved photo-induced discharge characteristics compared with exposure through the carrier tranport layer (CTL). The difference in photosensitivity was more pronounced when a thicker CGL was used, or when light of a less penetrating wavelength was employed. These results clearly indicate that the carrier generation at the very neighborhood of electrode is favored for higher sesitivity. This fact was interpreted based on an assumption that negative space charges were accumulated in CGL to enhance the electric field for carrier generation to a bigger extent at the electrode side than the other side. Those space charges were produced as a result of scavenging free holes in phthalocyanine, by the corona field.

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Recently, printing techniques using laser beam scanning have been developed actively. In Canon, we have developed many types of Laser Beam Printer. The quality of these Laser Beam Printers shows a yearly inprovement.
The significant factors for good color halftone reproduction based on electrophotography are as follows:
1. Optical spot distribution of semiconducter diode lasers.
2. Electrophotographic parameters of printer.
3. The type of threshold matrix of dither or dot pattern.
In this paper, we explain about optical spot distribution of diode lasers.
It is important for halftone reproduction to get optimum spot of optical system using semiconducter diode lasers. Therfore we have analyzed the relations between the characteristics of diode lasers and the parameters of optical system, and got analytical soultion of laser spot distribution by expansion of Hermite-Gaussian function.
Moreover, we have obtained simple solution in the case of only Oth-order expansion term, and using this solution, we could get simple representation of optical parameters, such as depth of focus, ratio of effective energy and condition of optimum optical system.

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Metal-free phthalocyanine thin films were prepared by the vacuum deposition technique on the glass substrate. Effects of the preparation condition such as the deposition rate and the substrate temperature on the dark resistivity and the crystallization of this film are reported. The specific resistivity of this film is increased with the decrease of deposition rate in the range less than 300 Å/min and the increase of substrate temperature in the range heigher than 100°C. Measurements of Xray diffraction and transmission electron micrograph disclose the facts that the crystals of phthalocyanine are grown from the substrate with the monoclinic structure and increased in the grain size with the increase of the substrate temperature. It is concluded that this crystal growing is corresponding to the increase of resistivity of this film.

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Properties of hydrophobic layer formation based on photoelectrochemical oxidation of aromatic compounds were studied.
Hydrophobic organic layers were formed on surfaces of semiconductor electrodes by photoelectrolysis in an electolyte containing water soluble aromatic compounds. This reaction brought about a hydrophilic and hydrophobic pattern on the electrode and could be used for a new type of printing system. In this work, the reactions of TiO₂/phenol derivatives were examined in detail as an a typical system.
The change of the hydrophilic and hydrophobic properties (wettability) was evaluated by measuring contact angles of a drop of water on the surface. The rate of change of the wettability depended on the irradiation wavelength, concentration of phenols and the PH value of the electrolytic solutions. These results were explained on the basis of the photoelectrochemical characteristics of the TiO₂ photoanode.
The effect of introducing the hydrophobic substituent groups, methyl- or ethyl- groups, to the phenol on the hydrophobicity of the deposited layers was also discussed.

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