In this paper, we compare electrophotographic printing and ink jet printing, observing the shape of printed dots or clusters of dots, and consider the factors which affect the uniformity of dot size. It is important to discuss the shape of printed dots because dispersed dots and clustered dots add different tastes to the mid-tone images. As the results of our experiment, it is clear that in the case of dots printed by electrophotographic method, the uniformity of the shape increases in proportion to the cluster size. On the other hand, in the ink jet printing method, the increase of uniformity is comparatively less obvious.

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This paper proposes a simple color image coding method using Principal Component Analysis (PCA) in the segmented color areas. A color image is segmented into different object areas with clustered color distributions. The chrominance a^* and b^* values in CIELAB space are observed to be strongly correlated with luminance L^* value in the object areas. After the segmentation, each object area is characterized by PCA. The segmented object areas are indexed by the class number which is greatly compressed by the conventional loss-less coding. The coded class number is transmitted with L^* image and the PCA parameters. PCA parameters are also compressed, because they are transmitted not by every pixel but by one set for each object area. The (a^*, b^*) values of each pixel are predicted by the projection of L* onto chromatic plane along to the first PC axis given by eigen vectors and are approximately restored from L^* value. L^* image can be compressed by the conventional lossive coding method such as JPEG or Wavelet. Finally, the full color image is reproduced by combining the luminance L^* with (a^*, b^*). The paper discusses the coding efficiency and the image quality changing with the class number.

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The general profile of cleaning performance (lifetime of cleaning blades and cleaning ability) of a leading-type blade cleaning system is examined from the viewpoint of rebound resilience (R). The cleaning blade edge is worn out by fatigue caused by stick-slip behavior against the photoreceptor surface. The prediction from the wear equation which takes into account viscoelastic behavior of stick-slip motion agrees well with the results of laboratory tests for fatigue fracture of polyurethane rubber. This causes the blade life to decrease as R increases. On the other hand, one of the reasons that lowers the cleaning ability is the residual toner particles being pushed back against the rotating direction of photoconductive drum, and going through blade during the slip process. Consequently, the cleaning ability is inversely proportional to the slip distance and hence, increases as R increases. For R below 50%, the cleaning ability is insufficient from the beginning in our PPC products. Combining the two factors-blade life and cleaning ability, the cleaning performance is found to peak at about R=50% and to decline as R increases.

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We have previously reported in a keynote speech at NIP13 that in Japanese analogue PPC market, the average monthly copy volume (AMCV) is proportional to the square of the speed (copies per minute) of PPCs, and the mean copies between service visits (MCBV) is proportional to the half power of the AMCV. In this paper, the analyses is extended to include European market data and to consider the average number of original documents per month, the average number of pages per original document and the installation rate of automatic document feeders. The background for the validity of the above-mentioned empirical laws in copy-and-distribute offices is elucidated, and the average number of pages per original document is determined to be 2.2. For the distribute-and-print offices, the average monthly print volume (AMPV) and the mean prints between service visits (MPBV) are investigated from the view points of the mission of the office, the principle of office structures and the information media used in the offices. We predict new relationships that the AMPV is linearly proportional to the print speed and the MPBV is constant independent of the AMPV. This suggests a more severe challenge for the hardcopy business.

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A novel simple printing method using conductive toner and a photoreceptor have been developed. In this method, the photoreceptor has an insulative grid with an electrode layer on the surface, and printed images can be formed with three procedures, although six procedures are necessary in the conventional (electro-photography) method.
First, an electrode which supplies and carries toner is placed on the photoreceptor through an air gap, and then an electric field is formed between the gap. Toner is then charged inductively, oscillated between the gap, and then fills the grid holes. The toner layer in the holes holds electric potential equal to that of the electrode on the grid, and the layer applies an intense electric field within the photoreceptor layer. In the next procedure, the toner in the holes is charged to reversed polarity by an electric field at the time that the photoreceptor is exposed, and jumps to the paper.
Though an excessive supply of toner can cause clogging, toner can be delivered from approximately 100% of the holes by optimizing the quantity of toner supply, and thus image density (ID) of as high as 1.3 was achieved. Furthermore, it was found that gradation printing can easily perform with our process, because ID is in proportion to the amount of exposure when ID is 1 or less. Moreover, electric field simulation showed that the electric field's condition can be utilized were available to provide the toner with a driving force toward the center axis of the hole, therefore the dot size is restrained by the optimum condition. The printing principle of this method has been demonstrated with an experimental apparatus and printed 4-point characters.

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Studies on electron transport material (ETM) applied for a single-layer organic photoconductor (OPC) for a positive charging xerography is summarized. Improving the xerographic properties of the single-layer OPC requires the high electron transport ability of the photoconductive layer, therefore, it is necessary to develop ETM which has a high electron transport ability, off course. In addition, a good solubility into organic solvent, a good compatibility into binder resin, and a high melting point are required for the purpose of improving productivity of device and the improvement of the thermal property of the photoconductive layer, too.
In this paper, we report the history and the subjects of the development of ETM are described in detail. Then, a molecular design of bisnaphtylquinone derivative based on being derived from diphenoquinone and naphthioquinone are introduced as an example of the latest ETM development.

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