Printing process is rarely used for electronic devices manufacturing. Photolithography process is mostly used as fine patterning method for that, because photolithography process has higher reliability for pattern reproduction. Nevertheless some trials to replace photolithography to printing have been gone forward in order to reduce the process cost. Potentiality of printing process for electronic devices depends on resolusion, thickness and property of ink. The resolusion in planography offset and intaglio printing is higher (L⁄S=10∼20μm for instance in micro-letter of securities printing) than in screen printing (L⁄S=20μm in a champion sample). However, we often try to use screen printing for some electronic devices, because of higher ink thickness (>5μm)at printed pattern. In this paper, LCD colorfilter by intaglio offset printing and reverse-offset printing is presented. And electronic parts (resistances, capacitors and inductors)embedded in circuit board by screen printing is presented as examples now in development. One of the most advanced theme in the future is production of organic transistors and organic TFT by printing process in all layers (electrode, dielectric, semiconductor etc.). There are many challenges in fine pattern printing technology, for instance, high reliability on accuracy of pattern figure, and high properties in any ink for each electronic layers. The key in conclusion is the development of ink materials and surface control.

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The high accuracy screen printing method (HADOP)was evaluated for improved structure of a printing plate, and 25μm stripe pattern printing was achieved by preparing new photosensitive materials, basically composed of acrylic co-polymer with flexible acryroil groups. The UV Ink was prepared by conventional materials design of UV hardening. The physical properties of the prepared ink were evaluated for application of HADOP. High accuracy screen printing method was achieved by the combination of an ink constituent having viscosity characteristic and by the selection of a high resolution plate. The UV ink of high thixotropic state was used to HADOP patterning because of great importance in viscose and flat property of ink. HADOP was composed of a printing plate and negative resist materials to optimize printing materials. As a result, the superior and sharp imaging was performed by increasing the transferring ratio of ink. Thus, isolated lines of 20μm levels were completed by the improvement for HADOP method. Color filters of preferred color reproduction were obtains by the isolated lines. The color filter prepared by the UV ink shows good color balance under white illumination and desirable characteristics than conventional color filters.

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Thin, light-weighted flexible displays are eagerly awaited in the field of next generation liquid crystal (LC) technologies. We created a novel-structure flexible LC display containing polymer structures of lattice-shaped walls and aligned fiber networks, which is formed through printing technique. The polymers fasten two flexible thin plastic substrates and keep the substrate gap constant even when it is bent. A flexographic printing technique was used in coating an LC⁄monomer solution onto a plastic substrate for large-size panel fabrication, and then the monomers were polymerized and cured by UV irradiation processes. We demonstrated a flexible color display using the fabricated LC panel (A4 paper size).

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The recent R&D trends of ink-jet printing using metal nano particles to the direct circuit patterning are reported. NanoPaste® was used as a conductive ink, which shows the excellent stability and low temperature sintering property based on "quantum size effect". Optimization of stage heating, surface treatment on substrates and design of jetting algorism are very important to obtain good printing quality. We have attained the patterning resolution with 70μm line⁄space by using commercial ink-jet system. "Super Ink-Jet Technology" is also successfully applied to the fine patterning with several micrometers rule. Au NanoPaste® shows the good performance equivalent to the conventional plated layer for Au wire bonding.

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The color and⁄or tone in printed image are generally controlled by area modulation of halftone dot. In actual reproduction process, forming a specified dot area is not easy because of the error coming from the effect of light scattering in paper and the effect of printing condition. Therefore unambiguous measurement of dot area in each process is important to control of printing process or analysis of printed image. In order to measure the dot area by means of the image analyzing system, it is necessary to separate a magnified halftone image into imaging and non-imaging area by a suitable threshold level. Selecting the adequate threshold level is essential since the measured dot area is strongly affected by threshold level. In this paper, newly developed method for deciding the best threshold is proposed. This method is derived by analyzing light intensity at dot edge and leads the way of setting threshold automatically. By using the method, dot area can be measured stably without influence of change in intensity and color of light source.

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In February 2004, Fuji Photo Film launched new thermal CTP system "HN-N" for newspaper sector, which is characterized by reducing the first plate-making time, the enhanced stability in terms of exposure, processing, etc. and the environmental performance. These characteristics are attained by the following three main technologies. Highly efficient polymerization technology to eliminate pre- and post-heating process. High reactive initiator system for radical polymerization, which provides the stability against ambient humidity and the storage stability. Highly controlled technology of the oxygen content in sensitive layer, which provides a sufficient safelight tolerance under room-light condition. We report features of this system and related technologies.

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