To clarify the effect of oxygen, pure selenium was doped with SeO₂ in the range of oxygen content between 3.5ppm to 1750ppm and the effect of oxygen was studied by the electrophotographic technique and by the time of flight technique. It was found that oxygen has a strong effect on changing the residual potential. The phenomenon can be explained by the change of structural defect density which takes place because of the change of the electrical neutral condition due to the doping of oxygen. From the analysis of the dark decay curve of the residual potential, it was also concluded that oxygen creates shallower levels. The mobilty was not affected by the addition of oxygen but the carrier lifetime was decreased with the increase of the oxygen content. This also shows that oxygen creates shallower localized carrier traps in selenium.

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Wire anode of DC corona charger used in electrophotographic process is degraded by discharging. This causes deterioration of copy quality. Then, change of tungsten wire anode and the relationship between this change of tungsten wire anode and copy quality were investigated to make these phenomena clear. Anode was analyzed by using SEM, TEM, XMA and FT-IR. Copy quality and discharging current distribution of charger were also examined.
Stable amorphous needles and film consisted of SiO₂ and WO₃ were observed to grow on anode by discharging. And, it was decided that growth of needles caused decrease of discharge current and copy density. It is discussed that the growth of products is caused by plasma oxidation of gases which contain Si in the air and chemical sputtering of tungsten wire anode which are induced by corona discharging.

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An analysis of the paper separation mechanism of electrophotographic copiers in which paper is separated from the surface of the photoconductor by means of AC corona discharge was carried out.
Separation of the paper from the surface of the photoconductor is expressed in terms of the interaction of the inherent mechanical force of paper to separate itself (moment) and the electrostatic force (moment) holding the copy paper onto the surface of the photoconductor.
The separation force, M_T, is the sum of the moment, M₁, of the copy paper itself arising from the curve of the photoconductor, and the moment arising from the weight of the paper, M₂.
Further, the electrostatic force, M_T', is expressed as a function of the electric field operating between the paper and the photoconductor.
This experiment was carried out using two photoconductors, each having a different diameter, and under conditions ensuring that M₂ and M_T', were the same for both photoconductors.
We were able, thereby, to prove that the separation efficiency is determined by M₁, the moment of the paper itself, which is dependent on the curvature of the photoconductor.

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The basic study of the effect of coordinated metal on electrical and photoconductive properties of metal phthalocyanines where metal = Cu, Fe, Co, Ni, Mn, Zn, and VO, was carried out. Absorption maximum in 650-700nm is due to charge transfer from metal to nitrogen in ligands. The charge transfer absorption bands of metal phthalocyanines are shifted to lower wavelength region as the reciprocal of ionic radius.
As the ionic radius of the coordinated metal decrease, the stability of these metal complexes increase. These results were in fair agreement with the order of the stability constant of the coordinated metal in Irving-Williams.
The SnO₂/MPc/metal cell containing sample sandwiched between transparent electrode and silver electrode have been prepared, and their photoelectrical properties studied in high vacuum. Photovoltaic effect was showed strongly in low field region. Activation energies (Ea) for electric conduction between 0.30eV and 1.04eV were measured, there being a definite correlation between log σ₀ (pre-exponential factor) and Ea. It was shown that the compensation effect arises from calculation of σ₀ and Ea. CoPc has a marked photoconduction in the red region (ca. 1300nm) where the intensity of the optical absorption is feeble.

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In general, it is difficult to get both good halftone levels and resolution on low resolution printer.
To solve this problem we selected dither threshold matrix which is small size in resolution unit and large size in gray level unit, and making same threshold data in a pair of matrices comprising in the diagonal position and using multi-level output of laser pulse width modulation, we could achieve good halftone reproduction. We call the procedure “Improved Halftone (I. H.) Method”.
Using this I H Method, we could expand to the case with screen angles, and get high quality full-color print output consist of yellow, magenta, cyan and black toners on laser beam printer.

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It is known that the value of gamma in tone reproduction of electrophotography is far larger than unity though the condition of gamma = 1 is preferable for the purpose of high fidelity in color electrophotography.
An improvement of tone reproduction in electrophotography is proposed in this paper where some of the latent image charges are discharged by the irradiation of fine dot pattern light from a LED array. The decrease in toner deposition due to the above dot erasing will give the decrease in the gamma value of tone reproduction. In the above case, however, there may exist the decrease in color purity and that in saturation value of optical density. It is expected that these decreases in color purity and saturation density may be prevented by the decrease in dot size and the increase in toner spread during the process of fixing.

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