A novel coating or imaging method to deposit organic pigment particles on a glass plate is proposed. The method is based on the photocatalytic reactions, and utilizes an aqueous dispersion consisting of pigments (phthalocyanines), surfactants to disperse the pigments, photocatalyst (Ru(bpy)₃Cl₃, bpy=bipyridine) and sacrificial agent([Co(NH₃)₅Cl]Cl₂). Photoirradiation (λ=450 nm) of the dispersion through a photomask and a glass plate induced the co-deposition of pigment particles and Co(OH)₂to give pigment-Co(OH)₂ hybrid films on the glass plate depending on the pattern of the photomask employed. The effect of irradiation time, light intensity, and surfactant type on the film formation was investigated,and a model for the photodeposition mechanism was proposed. The electric conductivity measurements in the dark and under illumination using a surface-type cell revealed that the hybrid film is photoconductive.

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A new objective noise evaluation method has been already proposed and successfully applied to noise evaluation for electrophotographic digital color copying machines. It is characterized by two kinds of metrics (non-uniformity and dot structure noise) based on the responses from a cooperative human vision model. In order to clarify its performance further,this paper applies it to noise evaluation for monochrome patch images (single-colored and multi-colored images) outputted from a color ink-jet printer. Consequently, the following results were obtained: (1)it claimed that the image noise decreases with an increase of the printer's resolution; (2)the correlation coefficients between the objective and subjective evaluation scores were 0.951 - 0.989 except for the dot structure noise for single-colored images. These results suggest that the noise evaluation method is e.ective irrespective of printer.s dot-forming methods. Moreover, it predicted that the resolution required for ink-jet printers is more than 3600×3600dpi under ideal conditions.

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In recent years, the remarkable progress of imaging systems has made it possible to capture the high dynamic range images, while the current display devices still have the low dynamic range. This paper proposes a novel method for dynamic range compression in captured images with keeping the input/output visual contrast by taking the ratio of a pixel to its local surround average based on Center/Surround Retinex model. The proposed method has the following features: [1] A novel spatially-variant LCRT (Local Contrast Range Transform) operator preserves local visual contrast of output image as much as that of input image, [2] The gradation and luminance in range transformed regions are reproduced smoothly and naturally after compression, and [3] LCRT is designed using a SS (Single-Scale) Gaussian surround but works in very stable without banding artifacts even near the boundaries of heavy changes in shadow and highlight. The paper discusses how the LCRT works stable different from Retinex though using the same SS surround from a theoretical point of view and demonstrates the features and the performances based on the comparative experiments with Center/Surround Retinex model.

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Since the first report of ultra-thin and double-layered organic light emitting devices (OLEDs) in 1987, considerable efforts have been made to improve the device characteristics for applications in flat panel displays. In general, the improvements of OLEDs have been achieved by the use of highly fluorescent materials and by the use of new device structures. Here we present a novel structure,multiphoton emission OLEDs,which can improve the device characteristics dramatically. Multiphoton emission OLEDs provide high luminance and long operational lifetime. We also introduce the multi-functional OLEDs with a new device structure.

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Fundamentals and research trend of organic thin-.lm transistors (OTFTs) are presented. Basic characteristics of a typical TFT are determined by how the carrier accumulates in the semiconducting material of gate/insulator/semiconductor-layered structure. Output current increases as the channel width and carrier mobility increase and channel length decreases. Accordingly, investigation of higher mobility materials and study of simple fabrication technique to obtain higher channel width/length ratio are the major research trends. For the quest of high mobility materials, the progress is currently being saturated and a thorough break-through is desired. When organic semiconductor is used as a TFT under the present circumstances,its performance is about the same as that of amorphous silicon. For the fabrication process, a study in our group is introduced as an example of vertical-type transistors having short channel length.

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In case that a organic EL display is driven by organic thin .lm transistors (TFTs), the characteristics (mobility, contact resistance, parasitic capacitance, ON/OFF ratio, and so on) of an organic TFT are discussed in the most basic pixel circuit or 2TFT circuit which is composed of switching and driving TFTs. Each TFT needs a mobility as high as that of amorphous silicon TFT, but the other characteristics are requested di.erently for each TFT. Attention must be paid on the other characteristics of the mobility although developments of the organic TFTs tends to be focused only on improving the mobility.

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π conjugated polymers have attracted considerable attention as a promising material for large-area flat displays because polymer-based EL devices can be fabricated without costly vapor processes. However, optical and electrical properties of π conjugated polymers in film are strongly dependent on an arrangement of molecules, and it is essential to control the arrangement to obtain desirable properties.

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In organic light-emitting diodes (OLEDs), realization of highly efficient electron injection is a key issue for achieving high energy conversion efficiency. In this paper, we elucidated mechanism of the efficient electron injection using a cathode layer composed of an ultra-thin layer of Cs, Rb, K, Na, Li and Ca capped with an aluminum back electrode. In particular, we focused on the electron injection mechanism at the interface between an organic layer and the cathode layer by changing the thickness of the low work function metal layer. Further, we demonstrate efficient electron injection and transport using a novel electron transport layer composed of Cs and phenyldipyrenylphosphine oxide (POPy₂) co-deposited layer.

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Organic light-emitting diodes (OLEDs) using phosphorescent dyes as emitting materials are expected to be applied to efficient full-color flat-panel displays and efficient solid state lightings because their emission efficiencies are much higher than those of conventional fluorescent OLEDs. Extensive research and development efforts have been devoted to OLEDs using phosphorescent materials ever since bright emission was obtained from an OLED using a porphyrin derivative in 1998 and from an OLED using an iridium complex in 1999. There are lots of reports on the development of phosphorescent materials which emit blue, green, or red and the performance of OLEDs using these materials. In this article, we review the research and development of the phosphorescent materials for the OLEDs.

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