Markets and printing industries require functional printed products distinguished from conventional printed matter. Development of functional inks is one aspect to realize this requirement. Pearl pigment is manufactured by coating natural mica surfaces with metal oxides and this layered structure makes visible light with a certain wavelength interfere and emits rainbow color depending on the coat thickness. Pearl pigment is applied to automobile paints, cosmetics package printing, security printing for bonds, etc. As another functional ink, light-scattering pigments are expanding market shares. A certain size of pigment particles are formulated in printing inks and, for example, subjected to printing on a material with mirror-like gloss to realize color variation depending on the particle size and view angle. Problems of pearl pigment ink in application to off-set printing, characteristics of the two types of functional inks, down flop property of light-scattering pigment inks, application to metal inks, etc. are discussed.

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Crystallites of carbon black (abbreviated as BC hereafter) are aggregates of polybenzene, where numerous π electrons exist and are responsible for electrical conductivity. Hundreds of commercial CB have different electrical conductivities because the motion of π electrons is varied due to differences in the backbone structure and surface functional groups of CB. In this review, after basic structures and properties of CB are represented, generally-mentioned implications of CB conductivity will be interpreted by reference to the three major CB properties and the experimental data mainly by the author. Finally, characteristics of representative CBs will be discussed simply using a model established by the author and coworkers.

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We can immediately erase the decolorable (erasable) toner e-blue™ and the handwriting of the decolorable ink with a heat-eraser in 500 sheets of paper. E-blue™ comprises of resin, a leuco dye, a developer such as ethyl gallate, and an erasing-reagent. A leuco dye is originally colorless. An erasing-reagent works as a trap of the developer at the heat erasing. At the toner producing stage, the erasing-reagent must be inactive. When heat erasing is conducted, the eraser-reagent must be active. The erasing reaction is the same as the reverse reaction of thermal paper of leuco dye. E-blue™ can be used as usual toner for printing of electro-photography and can be erased by heating with a special heat eraser, and the paper is used repeatedly for many times, saving forest, energy for paper-reclaiming plant and the transportation. The most difficult point is to realize the high optical density from the first and the lowest optical density after erasing. Therefore, we have studied the basic equilibrium and revealed the crucial factor to control. We have optimized the toner composition and the condition of the printer and the heat eraser. We have found the effective eraser-reagents or the materials that has trap function, such as cholic acid and starch. This technology is theoretically applicable to the ordinary ink and the application of newspaper-ink is most expected one, because newspaper becomes useless in a day. Zebra Corporation Ltd., a collaborated company, has commercialized the ink for ballpoint pen and marker. And other applications are expected to avoid paper related waste in many aspect of our life.

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