• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.5
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• pp.60-69
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• 2008

The principal reasons for applying a pigment coating to paper are to improve appearance and printability. The pigment coating provides a surface that is more uniform and more receptive to printing ink than are the uncoated fibers and, in turn, both facilitates the printing process and enhances the graphic reproduction. The improvement in print quality is readily apparent, especially in image areas or when multiple colors are involved. Although pigment coating of paper is to improve the printability, coated paper is not completely free from printing defects. Actually there are a number printing defects that are observed only with the coated papers. Among the printing defects that are commonly observed for coated papers, print mottle during multi-color offset printing is one of the most concerned defects, and it appears not only on solid tone area but also half dot print area. There are four main causes of print mottle ranging from printing inks, dampening solution, paper, and printing press or its operation. These indicates that almost every factors associated with lithographic printing can cause print mottle. Among these variation of paper quality influences most significantly on print mottle problems in multicolor offset printing, and this indicates that paper is most often to be blamed for its product deficiency as far as print mottle problems are concerned. Furthermore, most of the print mottle problems associated with paper is observed when coated papers are printed. Uncoated papers rarely show mottling problems. This indicates that print mottle is the most serious quality problems of coated paper products. Overcoming the print mottle is becoming more difficult because the operating speeds of coating and printing machines are increasing, coating weights are decreasing, and the demands on high-quality printing are increasing. Print mottle in offset printing is caused by (a) nonuniform back trap of ink caused by a nonuniform rate of ink drying, referred as "back trap mottle, and (b) nonuniform absorption of the dampening solution. Furthermore, both forms of print mottle have some relationship to the structure of the coated layer. The surest way of eliminating ink mottling is to eliminate unevenness in the base paper. Coating solutions, often easier to put into practice, should, however, be considered. In this paper the principal factors influencing print mottle of coated papers will be discussed. Especially the importance of base paper roughness, binder migration, even consolidation of coating layers, control of the drying rate, types of binders, etc. will be described.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.123-128
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• 2018

Effect of activators in flux on the printability and wettability of a solder paste was evaluated in this study. The activators in this study were dicarboxylic acids, which were oxalic acid (n = 0), malonic acid (n = 1), succinic acid (n = 2), glutaric acid (n = 3), adipic acid (n = 4), and pimelic acid (n = 5). When the solder pastes were observed with a SMT scope, solder with glutaric acid showed clean and shiny surface when it was melted. Slump ratio of the solder pastes was low when the carbon numbers of the dicarboxylic acid were 1-3. Spreadability was high when the carbon number was over 2. Zero cross time of wetting balance test was under 1 sec when the carbon number was over 3. When activator was oxalic acid or malonic acid, zero cross time was over 1 sec and maximum wetting force was low. Fluxes with the oxalic acid and malonic acid showed decomposition at the temperature close to melting point. Among the dicarboxylic acids, glutaric acid provided excellent slump, spreadability, and wettability.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.1
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• pp.52-60
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• 2009

A printing defect known as fluting (or waviness) of the web printed by heatset web offset printing process is one of the chronically serious problems deteriorating print quality. In this paper, fluting occurrence on uncoated papers was explored in terms of many printing conditions including drying temperature, fountain solution amount, ink supply, and press configurations. For this purpose, fluting on prints from real press runs was appraised in a quantitative manner. As results, ink supply was a distinctive factor for fluting such that the lower ink amount, the milder fluting. However increase in fountain solution seemed to make fluting severer while the effect of drying temperature was inconsistent for each paper. This result might indicate variable drying requirements for each paper. Thereby it was suggested that the optimum drying conditions related to the printabilities of each paper need to be established to minimize fluting potential. A press with short dryer and drastic cooling unit produced higher fluting. Suggestions for future work were given along with interpretation for the results.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04a
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• pp.1-6
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• 1999

A study was made to determine the effect of plastic pigment on the coating structure and printability of coated paper. Three basic plastic pigments were investigated such as solid-bead type of plastic pigment, binder type of plastic pigment and hollow type of plastic pigment. In the systems investigated, it was observed that particle shape and structure of plastic pigment had influenced on the rheology of coating color, the state of packing, and the properties of coated paper. The materials investigated were restricted to plastic pigments commonly uesd in paper coating formualtion. Inorganic pigments used in this research were kaolin clay which is platelets and calcium carbonate which is rhombic. Three kinds of plastic pigments were blended in the color made up with two inorganic pigments, respectively. The combination of pigments were carried out (1) to determined the effect of paticle structure of plastic pigment on the state of dispersion of coating color, (2) to observe the effect of temperature of calender on the property of coated paper prepared with plastic pigment. The data indicated that binder and hollow type of plastic pigment had the best results on improving the properties of coated paper such as paper gloss, opacity and air permeability ect. and solid-bead type of plastic pigment in the next place.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04a
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• pp.7-16
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• 1999

The aim of this research was to evaluate the influences of coating components and structures on ink absorbency. The ink absorbency was measured as porosity, K&N ink absorption, gloss and ink set-off. In order to obtain the relationship between the coating structure and the ink absorbency, the binder level was adjusted and two types of pigments were examined. One of the pigments was known to make the porous coating structure and the other one had strong ink affinity. The effects of coating components were studied by applying six different types of latex and various additives . In this research, CLC(cylindrical laboratory coater) and Prufbau printability tester were used. It was found that the decreasing latex dosage and introducing porous pigment were effective solutions to increase ink absorbency. However, the ink absorbency could not be improved by applying the fine pigment even though it had strong ink affinity. Among the characters of the latex, particle size and surface tension were found to have the strong effect on ink absorbency. The ink absorbency increased with large particle size and low surface tension latex. The additives were varied and it was found that applying to the top coating was effective.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.128-128
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• 2001

제지기술의 변화속도가 빨라지고 제품의 고품질화가 요구가 많아지면서 finishing 공정 에 대한 관심과 중요성이 점점 더 높아지고 있다. 소비자의 요구에 부합되는 제품의 품 질을 얻기 위해서 여러 가지 방법들이 개발되고 있으며, 그 중에서 calender 설비 및 처리 기술이 계속적으로 발전하고 있는 추세이다. 특히 coated paper 제조 공정에서의 s supercalender 처 리 기 술은 매 우 중요하다. F Finishing 공정은 종이의 품질을 결정하는 제지 공정의 마지막 단계로서 calendering 처리 방법에 따라 제품의 품질을 크게 변화시킬 수 있다. 따라서 본 연구에서는 기존의 s supercalendering 처리 조건을 변경시켜 도공지의 품질 특성을 관찰하였으며 실험실용 s supercalender와 현장 적용을 통하여 supercalender 처리 조건이 도공지 품질에 미치는 영향에 대하여 검토하고 이를 이용하여 제품 품질을 개선시키기 위해서 수행하였다. 안료 배합비를 달리하여 다양한 온도와 압력 조건을 적용하여 보았으며 동일한 백지광 택을 갖는 여러 조건들에 대해서 각각의 품질 특성을 살펴보았다. 동일 백지광택에서 온도가 높을수록 macro-roughness, micro-roughness는 더 우수하게 나타났으며 이는 printability의 차이로 이어 졌다. 실험실용 supercalender를 이용한 실험에서 경도가 다른 두 가지 탄성롤로 cotton roll 과 polymer roll을 사용하였으며 통일한 온도와 압력 조건에서 calendering 특성은 서 로 다르게 나타났다. Calendering 조건이 가혹할수록 두 roll간의 특성은 더욱 두드러지 게 나타났으며 macro-roughness 보다는 micro-roughness에서 차이가 더 큰 것으로 확인되었다. 이러한 두 roll간의 특성 차이로 인하여 실제 인쇄 결과는 다르게 나타날 것으로 예상된다.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.1
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• pp.26-34
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• 2010

Effects of drying condition (IR radiation) on the optical properties and the printability of coated paper were elucidated at various latex sizes and low and high coating color concentrations. It was found that the smaller latex provided better rheology and higher dry and wet pick strength than the larger one. The high solids coating resulted in higher paper gloss and smaller roughness than the low solids coating, even though the clay addition was reduced by 20 parts in the high solids coating. Increasing IR radiation prohibited binder migration into the base paper. Thus it improved binder distribution and decreased pores in the coated layer, resulting in the increased dry and wet pick strength and the improved printing gloss. On the other hand, the color trapping and ink set-off was impaired with increasing IR radiation. Print mottle index passed through a maximum with increasing IR radiation.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.1
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• pp.59-66
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• 2013

Fillers have been used for printing paper to improve printability, sheet formation and optical properties and to reduce production costs by replacing expensive wood pulps. However, an increased filler content will decrease paper strength because filler particles interfere with fiber-fiber bonding. In order to increase filler content without sacrificing too much paper strength in high filler content papers, the surface of precipitated calcium carbonate (PCC) has been modified by adsorbing anionic polyacrylamide and cationic starch in series. The adsorbed polymer layers would enhance interactions between the filler surface and the fiber surface, improving internal bonding. It was found that the modified PCC increased paper strength at a given filler content compared to the coventional method. Negligible differences in optical properties and formation of paper, filler and fines retention and drainage on the wire section were observed between the modified and the conventional PCC. However, the decreased bulk of paper was observed when the modified PCC was used.

• Journal of the Korean Graphic Arts Communication Society
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• v.25 no.1
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• pp.109-120
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• 2007

In gravure printing, the amount of ink fill into the cells has a great effect on the qualities of final printed products. And printability of final products is determined by every kinds of variables. Ink transfer process is not verified scientifically because gravure cell is small and printing speed is rapid. In order to understand the ink transfer mechanism of conventional gravure, this study is performed using the Computational Fluid Dynamics Evaluation. Flow-3D simulation software is used for considering of Newtonian flow. Among the various factors, this study have dealt with gravure cell types used computer simulation in order to define distinctive features in ink flow in the cell. The results of simulation, it defined the distribution of pressure, speed, stream function, viscosity, shear rate, surface tension during the gravure printing. It is founded out the difficulties and characteristics according to the printing speed and viscosity of Gravure ink.

• Journal of the Korean Graphic Arts Communication Society
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• v.26 no.1
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• pp.87-96
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• 2008

Paper stock could be situated in a cooled environment seasonally and/or regionally otherwise it is stored in a controlled warehouse. In this paper, printing problems on a cooled paper are investigated and characterized in terms of paper properties. For this purpose, various kinds of sample are cooled down under a specially designed freezing device and printed for observing their printability. Causes for poor ink transfer on a cooled paper are suggested due to condensation, surface inactivity, and rheological change in ink film. Paperboards with higher amount of binder, thick and/or multi-coated layers are more vulnerable to poor ink trap. Severe drying of wet coating could cause a similar result as that of the coatings with higher binder formulation. It is shown that more absorptive porous structure is desirable for better ink receptivity in a cooled status. Printing on a dampened surface may be an indicator for ink transferability on a cooled paper. Finally, desirable directions for papermaker and printshop are suggested.