Color reproduction theory for printings has been studied based upon color density model, in past, since printing technologies nere combined with photographic processes in color separation, masking and black printer. Introduction of electronics into plate making started gradual changes of theory toward linear treatment of color information, but we are still in confusing situation between color density and linear models. Recent efforts of the author to reestablish color reproduction theory by using linear model are summerized in this paper. Discussions on Demichel relation and Neugebauer equations are presented as a start point. Compression of color gamute, determination of dot area and black printer are described including new finding on under color addition concept comparing different dot design. Use of linear model to construct color reproduction theory in prints is promissing analytical understanding and system design even in mixed media information networks.

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Input output technology for Japanese text is reviewed from the viewpoint of computer engineering. Hardwere components for this technology has already been established. The remaining problems are softwere and man-machine interface. As for input, kana to kanji conversion technology is widely available on Japanese word processors. However, blind touch method is only used for inputting kana and the operator must watch VDT screen whenever inputting kanji. Therefore, they are not suitable for inputting large amount of Japanese text. The superiority of 2-stroke methods for inputting kanji are explained in this regard. As for output, some comments are made on layout instruction.

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Droplet velocities expelled from a Kyzer type pulse on demand ink jet print head were measured from high speed motion pictures, which had been shot with the camera made for this purpose. The analysis of experiments shows that the first droplet velocities decrease and the second droplet velocities increase after pause of over one minute. However this phenomenon was not observed when distilled water was used as ink, so the velocity change after time interval is caused by solute used to control viscosity and surface tension coefficient of the ink. In order to investigate this effect, the velocity change was measured using several kinds of mixed ink of water and polyethylene glycol with molecular weight of 200, 400, and 600. The experiment shows that the velocity of the first droplet after pause decreases using the ink controlled same viscosity, as molecular weight of polyethylene glycol increases. Therefore, ink with less velocity change is obtained by small molecular weight solute as controller of the ink viscosity.

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An instrumentation for online measurement of patch density in color proof printing is presented. A non-contact density-to-voltage transducer is newly designed, in which both illuminating light and reflected light are sharply focused by two lens systems in order to suppress stray light. Three transducers are conveyed by the carriage of printing machine and scan the printed paper across three corresponding patches. During the scan they sample ink density and send the data to an industry computer, whose program extracts patch data out of stored data sequences based on the feature of data pattern, and computes patch density by averaging and adjusting zero levels to the data on white area preceding patches. It is found through online experiment that our instrumentation is practically applicable, but random float of printed paper causes some fluctuation in resultant density readings. A technique to compensate this error is presented.

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In this paper, the amount of ink transferred to paper or aluminium foil was measured by IGT printability tester and a chemincal balance. A very simplified model (a capillary model) is used to simulate the printing process and the corresponding ink transfer equation is given:
Y/X=[f+k⋅(1-f)⋅√P/ηV/X]⋅F here Y/X is ink transfer rate, f ink split coefficient, F ink covering ratio of unit area, and P, V, X, η, k are printing pressure, printing speed, ink film thickness, viscosity of ink and a constant, respectively. The effects of P, V, X, η on ink transferring were examined, and the precise forms of f and F were given experimentally. It is surprising to find that f is not a constant, although generally considered to be constant, and decreases greatly with increasing V and X. F is the function of P and X only, and increases with increasing P and X. In the case where P and X are fairly large, F attains its saturated value 1, holding up its effects on ink transferring as shown in the equation above. But when P or X is very small, F is very small and changes greatly with P and X, and becomes a critical factor in ink transferring.

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Photochemical reaction of the free radical photographic system proposed by Sprague was investigated in details. Photochemical products of diphenylamine-CBr₄ system (DPACBr₄) was studied in the solution, in bulk and in polymer matrix, It was found by the product analysis that in the solution a red dye 9-diphenylaminoacridine (DPAAc) is produced predominantly and the blue dye 4, 4′, 4″-tri (anilino) triphenylmethane bromide (TATPM) is scarcely formed, while in bulk the blue dye (TATPM) is formed in the amount comparable to that of the red dye (DPAAc). Similar result to that in bulk was obtained in polymer matrix. The results show that several photoproducts besides triphenylmethane dye identified by Sprague are formed through the addition of ·CBr₃ to ortho-position and nitrogen of DPA, and that the fractions of the photoproducts depend strongly on the reaction conditions, such as concentrations, molar ratios, and the phases.

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HP-system, direct plate-making system which is cosisted of the ultra high speed plate of composite type FNH and the automatic processing system FHP, has been developed in 1980. Recentry, in parallel with making great progress in the original making system, users' needs to use the direct plate-making system are notably increasing, such as LASER direct out-put, the proofing system and the electronic full-page make-up system and so on. Based on above mentioned needs, we have improved the HP system in following points, 1) Improvement of the image sharpness, resolution and tone-reproduction, 2) Improvement of the spectral sensitivity suitable to Ar ion laser light, 3) Simplification and stablization of the processing, 4) Development of more compact type processor. Thus, we succeeded in putting this plate system in the markets (1) LASER direct plate-making system and (2) Projection direct plate-making system.

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