In order to read an electronic document, a development of a digital paper, which has the convenience of the conventional hardcopy and a capability of access to digital information, is expected. The technology field of digital paper contains an electronic paper, rewritable paper and paper-like display. It is necessary for the development a digital paper technology to investigate the key-technology for the rewritable marking. The thermal rewritable marking has been used practically as a rewritable card. A fatty acid-polymer composite type rewritable marking, a leuco dye-polymer type rewritable marking, an electrophoresis display using micro-capsule, a twisting ball display, dichromatic dyeliquid crystal composite type paper and liquid crystal/organic photoconductor double layered e-paper are reported as rewritable technology. We had reported the principle and characteristics of toner display using the conductive toner that is a familiar to us as an image formation material for a hardcopy.

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Research on organic light emitting diodes (OLEDs) has been attracting considerable innterest since the first report on OLEDs with high luminance and low driving voltage. They fabricated multi-layer devices for the excellent OLEDs which were composed of a hole injecting and transporting layer, electron injecting and transporting layer and light emitting layer using many organic compounds. One of the goals in the research on OLEDs is to develop full-color displays. For this goal, it is important to develop blue, green and red light emitting materials, and the improvement of the hole and electron injecting materials.

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This article reviews recent progress in standalone-type rewritable media for information recording, where “standalone-type” means that the media can be separated from recording devices. Magnetic rewritable media are the first type introduced into the market. Although the image resolution is low, the cycle of image formation and elimination can be repeated 2, 000 times or more. Thermal rewritable media are the second type and now extensively studied. Typical four examples of thermal rewritable media are shown along with their recording principles and characteristics. These are liquid crystal droplet dispersed in a polymer matrix, cholesteric liquid crystal of medium molecular weight, low molecular weight compound having long alkyl group dispersed in a polymer matrix, and leuco dye in combination with color developer having long alkyl chain.

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A flatbed scanner was carefully examined to fulfill a stable performance as an input device for experimental purposes. Repetition stability of length data was found to be very stable at repeated scannings. Differences of length data at different positions of glass surface were very small both in horizontal and vertical placings. Repeated scannings of gray levels became stable in 200 times which required approximately one hour. This might be coursed by the changes in dark current on CCD cells depending on temperature. Differences of gray levels at different positions of glass surface were small but which showed significant differences. Differences in gray levels depending on the time after being turned on were a little bigger and also significant. Differences of gray levels at different exposures were significant at thinner gray levels. Exposure was found to affect comparatively little, especially for thicker optical density. The differences, however, were small as far as series of scannings were carried out at the same conditions and at the same time, therefor the scannings would be considered meaningful. Similar tendency as the descriptions mentioned above was observed at a different spatial resolution.

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Hydrophilic property of siliceous films electrodeposited on copper foil was investigated for application as nonimage areas of direct image lithographic printing plates. The siliceous films were electrodeposited on copper foil in sodium silicate solution (SiO₂/Na₂O molar ratio: 2.5, concentration: 10wt%) for 5 and 10 seconds. The applied voltages were 3-13V. The contact angle of water on the electrodeposited films and their IR and XPS spectra were measured. The plate wear test was carried out using an offset press. The samples electrodeposited at 3V caused scumming during the wear test. The siliceous films not so thick as to be powdery were presumed to be suitable for the non-image areas of lithographic printing plates.

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The principle of color reproduction by the superimposition of halftone dots in printing process being essentially subtractive mixture, the necessity of the correction of optical dot gain, and the corrective term of optical dot gain into Pollak equation concerning C, M, Y, Bk halftone dots imposed on paper were already introduced by Nonaka, et al., in 1999. This paper presents the numerical output method of the C, M, Y and Bk dot areas converted from the image singal R, G, B harvested from continuous tone color original by scanner using proportional tone compression. The dot area of black by gray component replacement (GCR) was fixed and other C, M, Y dot areas were determined so that the optical reflectance through color filter (R, G, B) was to be equalized with the optical reflectance by prepositional tone compression. The dot areas were determined by the simultaneous quadratic equations with three unknowns (c, m, y). These equations were constructed with Pollak equation containing the corrective terms of optical dot gain and solved by the succesive approximation devised or the method of Newton-Raphson. The conversion contained gray balance, optical and mechanical dot gain, GCR, masking (color correction) and the effect of paper used. The process work has been dealt with empirically. While LUT is one of the empirical methods, the proposed treatment presented in this paper is to construct the numerical model of color image made up of dot areas superimposed, and by this treatment the fractions of dot areas required are calculated numerically.

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Photochromic materials are promising candidates for photosensitive parts in photoimaging and photorecording materials. However, the monitoring light for detection of photochromic color change can lead to degradation of the chromophors at photo-writing parts because of the photochemical back reaction. There have been several methods for new mode of photoimaging and photorecording system by using fluorescence property, photoreorientation, mass transportation, liquid crystal alignment or phase control and cholesteric liquid crystal pitch control of photochromic materials. They are useful to keep the writing information during reading process. This paper describes these methods briefly.

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In each process, such as pulping, paper making, and finishing, the manufacturing method of paper has been developed while improving production speed and paper quality, and lowering production cost and environmental pollution. Progress of the afforestation technology and recycling technology including biotechnology develops further in recent years, and paper is evolving further the nature as a circulating type material of a terrestrial scale including natural environment and city environment. This paper describes the latest raw-material situation first. And each manufacturing process from the preparation of raw-materials to finished paper is intelligibly explained.

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