Fundamental aspects of optical dot gain are described. Taking into account multiple internal reflections, we first derive a general, mathematical expression for optical dot gain in the same method as that of F. R. Clapper and A. C. Yule. Among the four parameters used, i.e., ink transmittance T_d, paper transmittance T_p, and reflectances of the front and back surfaces of paper R_f and R_b, T_d and R_f have dominant effects on optical dot gain. The derivation also leads to a conclusion that the famous Yule-Nielsen index n may, under practical conditions, easily exceed 2, which cases have often been attributed to the non-ideality of dot patterns. Then, there is shown that density measurements on photographically produced, ideally hard and perfectly noiseless halftone tints support the above conclusion. Finally, researches on optical dot gain in the past are briefly reviewed.

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The Murray-Davies and Yule-Nielsen equations are not mechanistically accurate for multilayer color proofing but can have utility if used with their limitations in mind. The model herein is based on phenomenological behavior and is consistent with the known effects of dot size, dot shape, screen resolution, and separation from the paper base in a multilayer color proof. The model suggests a phenomenon of hypergain occurs in highlight dots, which further enhances optical dot gain. Hypergain seems to be greatest between 20% to 30% dot areas, even though gain is greatest between 45% and 50% dot areas. By describing optical gain as a difference in reflectance vs. √A*, use of the model throughout the tone scale can allow computerized scanners to accurately determine dot areas to achieve subtle color changes or balance in color prepress proofs.

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This paper concentrates on the trends of color proofing technology and how to use the technology in graphic arts system. Image characteristics of on-press and off-press prof sheets differ from each other. It is caused by the difference of optical dot gain and physical shape of half tone dot in each color proof. How to use off-press color proofing technology as the quality controol tool is discussed.

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Intaglio printing plates are electroplated with chromium to increase their durability. But it is not sufficient for new materials which are recently used for intaglio ink, wiping roller and so on. In order to increase the durability of plates, the increment of chromium layer was tried. However, as the layer thickness of chromium increases, the intaglio lines, especially the fine lines, become dull. In order to make the film harder than the chromium plating plate without environmental pollution, a new method has been suggested. As a result of the preliminary study of this subject, ion plating, one of the physical vapor depositions (PVD) seemed to be promising. We have started the study of the application of this method to the platemaking process. The RF (Radio Frequency) type ion plating apparatus has been introduced. A sample of 100×100mm² size was fixed just above the evaporation source. Five kinds of films, which were TiN, TiC, Cr, CrN and CrC, were deposited on the substrates and their physical properties were examined to determine the best condition for each kind of film. Some abrasion tests were made to estimate printing durability without on-press test and intaglio line fidelity were measured and compared to a new method. We used the nickel electroformed intaglio plates which were coated with TiN film by ion plating and electroplated with chromium as test samples.

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Infra-red spectroscopy, Karl Fisher coulometric titration, and electric impedance measurements have been used for the determination of the amounts of water in emulsified inks. Another new method using ¹H-nuclear magnetic resonance (NMR) has been proposed by the authors for the purpose of water determination. It was found in the NMR spectrum, that the water peak does not overlap the peaks dus to ink materials commonly used in the practice of lithographic printing. Thus, by choosing an adequate solvent, for example, deuterated pyridine which dissolves both ink and water and yet the peaks of which do not interfere the water and ink peaks in the spectrum, the amounts of water in inks have been determined. In this NMR method, samples from the ink rollers or from the image areas on the lithographic plate can be simply inserted into measuring tubes without any pretreatments. This would certainly eliminate such errors as caused by the loss of water during the processes of water extraction from ink by heating or by using solvents prior to the Karl Fisher coulometric titration. However, since the amount of ink in sampling is less than 30mg, inhomogeneity in dispersion of water in inks might causes errors in the determination of water contents.

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There are three kinds of basic block copy; hand drawing, direct type impact and clean proof. To produce an accurate and clear image in film-making using any block copy, it is necessary to accurately grasp the state of gradation on the border of the image area and the non-image area. This study was intended to analyze this gradation condition using a microreflection density curve by an optical method. In the experment, roughness of paper that has much to do with the quality of the block copy image as well as the micro-reflection density of the image on each sheet of paper were measured. The micro-reflection density curve of three kinds of the block copies are shown in Fig. 3, Fig. 4 and Fig. 5. Each curve shows clearly the characteristic of the respective block copy. The results of the optical measurement of paper surface roughness are shown in Fig. 6. The angle made by an extension of the straight line which connects the density points 0.4 and 0.8 on the rising section of the micro-reflection density curve, and the ground line is taken as θ, and its tangent as γ, and this γ value is used to evaluate the property of the image. The results of measuremet are show in Table 2 to 15. These results indicate block copy properties.

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Attempt to make the lithographic plate that is capable of printing without desensitizing treatment was carried out. Silicate treatment was adapted for the surface treatment of aluminum because it gives the strongly hydrophilic surface. Brush grained aluminum plate was anodized under different conditions and treated with solution of sodium silicate. The anodization was carried out in phosphoric acid solution, sulfuric acid solution and mixed solution of phosphoric acid and sulfuric acid. Removability of ink on these sample surfaces by fountain solution and bonding strength of photosensitive layer were examined. The removability of ink and the bonding strength of photosensitive layer were affected by the conditions of the anodizing. The surfaces anodized in 10% phosphoric acid solution and mixed solution of phosphoric acid and sulfuric acid gave good results. Experimental results proved that there is possibility of printing without desensitizing treatment.

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Design studies on a Kyser type ink jet print head were made using Newtonian mechanics and the equivalent length given by Beasley, The jet velocity, the ratio of the fluid volume driven toward the nozzle to the volume of ink which flows into the ink reservoir and the time to refill the ejected droplet mass were analyzed for several system parameters. A print head needs shorter refill time, greater jet velocity and greater volume ratio. Analysis shows that these characteristics get under next system parameters; wider ink chamber and shorter length of the nozzle.

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This paper provides informations about the field of digital image processing which has grown considerably during the past decade with the increased utilization of imagery in prepress applications coupled with improvements of digital computers and related signal processing technologies. This paper is divided into three chapters. In Chapter 2 the fundamental characterization of continuous images are described. Chapter 3 contains the explorations of image sampling and quantization techniques and the characterization of sampled images are explained. In Chapter 4 of the next issue.

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The progress in printing technology has been remarkble in recent years and many research works have been done on color tolerance problems. But these problems have not been solved satisfactorily. In the present paper, we studied color tolerances of print by the L*a*b* system, the Munsell system, and the NBS values. As a result of our experiments, it is clear that the NBS values reflect dot area ratio changes and the Munsell system can be used to measure slight color differences. Accordingly, colorimetry of prints can be used for color control and evaluation of printing.

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