• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.11-17
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• 2007

In this paper, we present a design, analysis, fabrication and performance test of the novel DoD metal-jet system for application to the high-density and high-temperature-melting materials. The theoretical analysis of the metal-jet nozzle system is derived by using electro-mechanical analogy. Based on the theoretical analysis results, we design the metal-jet print head system and fabricate the metal-jet system, which can eject the droplet of lead-free metal solder in high-temperature. In the experimental test, we set up the test apparatus for visualization of the droplet ejection and measure the ejected droplet volume and velocity. As a result, the diameter, volume and the velocity of the ejected droplet are about 65 $\mu$m $\sim$ 70 $\mu$m, 145p1 $\sim$ 180 pl and 4m/s, which shows quite good agreement with the theoretical analysis results of the 75 $\mu$m-diameter and 220 pl-volume of droplet. In comparison with the experimental result, the errors of diameter and volume are 7% $\sim$ 13% and 18 $\sim$ 34%, respectively.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.173-178
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• 2007

Carbon nanotube cathodes(CNT cathodes) with a trench structure similar to gated structure of triode-type cathode were fabricated by a screen printing method using multi-walled carbon nanotubes. The effects of surface treatments on CNT cathodes were investigated for high efficiency field emission displays(FEDs). A liquid method easily removed the organic residue and protruded the CNTs. Field emission properties were measured by using a diode-type mode. The liquid method produced a turn-on field of $1.4V/{\mu}m$. The emission current density was measured about $3.1mA/cm^{2}$ at the electric field of $3V/{\mu}m$. The liquid method showed a high potential applicable to the surface treatment for triode-type FEDs.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.3
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• pp.1-10
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• 2014

Offset paper printing is a promising roll-to-roll technique for color printed materials. Although it is no doubt that understanding ink transfer mechanism in offset printing process is necessary to achieve high printing quality, investing the relationship between inks and substrates at the nip is difficult experimentally due to high printing speed. In this paper, rheological behavior and splitting point of the ink at the nip is studied using package software Ployflow and Flow 3D based on Navier-Stokes equation. Polydimethylsiloxane (PDMS) ink and IGT printability tester were used for an model ink and experiment to compare with that of simulation data, respectively. As a result, higher viscosity at state flow and pressure increased ink transfer due to higher possibility of presence of cavitation at the nip and increase in covering area ratio. These results have shown good agreements with experimental data compared by measuring density of print through.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.293-298
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• 2011

The most widely used method to form an electrode in industrial solar cells are screen printing. Screen printing is characterized by a relatively simple and well-known production sequence with high throughput rates. However the method is difficult to implement a fine line width of high-efficiency solar cells can not be made. The open circuit voltage(Voc) and the short circuit current density(Jsc) and fill factor(FF) need to be further improved to increase the efficiency of silicon solar cells. In this study, gravure offset printing method using the multicrystalline-silicon solar cells were fabricated. Gravure off-set printing method which can print the fine line width of finger electrode can have the ability reduce the shaded area and increase the Jsc. Moreover it can make a high aspect ratio thereby series resistance is reduced and FF is increased. Approximately $50{\mu}m$ line width with $35{\mu}m$ height was achieved. The efficiency of gravure off set was 0.7% higher compare to that of scree printing method.

• Macromolecular Research
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• v.15 no.2
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• pp.114-128
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• 2007

Polyimides are one of the most important classes of polymers used in the microelectronics and photoelectronics industries. Because of their high thermal stability, chemical resistance, and good mechanical and electric properties, polyimides are often applied in photoresists, passivation and dielectric films, soft print circuit boards, and alignment films within displays. Recently, fully aliphatic and alicyclic polyimides have found applications as optoelectronics and inter layer dielectric materials, due to their good transparencies and low dielectric constants $(\varepsilon)$. The low molecular density, polarity and rare probability of forming inter- or intra-molecular charge transfers, resulting in lowering of the dielectric constant and high transparency, are the most striking characteristics of aliphatic polyimide. However, the ultimate end use of polyimides derived from aliphatic monomers is in their targeted applications that need less stringent thermal requirements. Much research effort has been exerted in the development of aliphatic polyimide with increased thermal and mechanical stabilities, while maintaining their transparencies and low dielectric constants, by the incorporation of rigid moieties. In this article, the recent research process in synthesizing fully aliphatic polyimides, with improved dimensional stability, high transparency and low $\delta$values, as well as the characterizations and future scope for their application in micro electric and photo-electronic industries, is reviewed.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.157-164
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• 2008

The temperature-entropy diagram of water or vapor displays graphically the thermophysical properties, so it is very conveniently used in various thermal systems. On general T-s chart of water, there are temperature, pressure, quality, specific volume, specific enthalpy, specific entropy. However, various state and process values besides above properties can be plotted on T-s diagram. In this study, we developed the software drawing twenty six kinds of properties, that is temperature, pressure, quality, specific volume, specific internal energy, specific enthalpy, specific entropy, specific exergy, exergy ratio, density, isobaric specific heat, isochoric specific heat, ratio of specific heat, coefficient of viscosity, kinematic coefficient of viscosity, thermal conductivity, prandtl number, ion product, static dielectric constant, isentropic exponent, velocity of sound, joule-thomson coefficient, pressure coefficient, volumetric coefficient of expansion, isentropic compressibility, and isothermal compressibility. Also, this software can analyze and print the system values of mass flow rate, volume flow rate, internal energy flow rate, enthalpy flow rate, entropy flow rate, exergy flow rate, heat flow rate, power output, power efficiency, and reversible work. Additionally, this software support the functions such as MS-Power Point.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.3
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• pp.8-12
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• 2009

According to a previous study, talc as a coating pigment can improve the viscosity and the water retention of coating color, the compressibility of coating layer, and hence gravure printability. Talc is also well known for its larger particle size than other pigments, which implies that less binder may be need due to its smaller specific surface area. This study investigated the possibility of reducing binder content for matte grade paper. Coating color was prepared with the Cotalc-2000, which showed the best properties in the previous study. The binder content was varied and the effect of binder content on the physical properties of coated paper and the gravure printability was investigated. It was shown that binder content could be reduced when talc was used as a coating pigment. The reduction in binder content did not influence gloss, roughness and the print density of coated paper but showed improvement in paper porosity, compressibility and missing dot.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.5
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• pp.1-8
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• 2014

In this study, the influence of the physical properties of ink such as ink dispersity and emulsified amount on the printability of a coated paper was investigated with seven kinds of cyan inks. In addition, two kinds of coating formulations were tested to evaluate the effect of coating structure on the coated paper printability. It was found that the cyan ink with $2{\mu}m$ pigment size had the best dispersibility and hence the ink showed a best ink density on the two kinds of coated papers. When the emulsified ink A with IPA 20 wt% had a lower viscosity than emulsified ink B with IPA 10 wt%, the emulsified ink A showed relatively high value of the ink transfer rate in comparison with emulsified ink B. Despite the high value of ink transfer rate, the coated paper did not show a good printability because those inks with low viscosity due to a strong emulsification were easy to make print mottle on the coated paper.

• Journal of the Korean Society of Costume
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• v.58 no.10
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• pp.65-77
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• 2008

The purpose of this study is to analyze the correlation between the density, the Count and the width of cross section in 2D function through comparison the difference of simulated fabrics based on the various yarns, and to compare the 3D effect by Lay Mapping of diverse fabrics. The method of research is to weave the eight fabrics composed of cotton, linen, worsted, slender yarn, loop, $m{\acute{e}}lange$, woolen, and yarn twist with Hi-Tex program, and to practice 3D mapping with Hi-Print program. As a mapping object, the flared skirt which is a basic costume item is selected. As a result, the thickness of yarn in CAD system was fixed by the width of cross section rather than Count, especially by the width of core section not including the fluff section. The type of yarn such as cotton yarn, linen yarn, and worsted had effect on the shape of texture, but had few interrelations with dimension. In the case of 3D mapping, the textural characteristic and the dimension were presented precisely, whereas there were several limitations. First, the thickness of tissue has not been represented. Secondly, the effect of texture such as fuzzy look, loop was not expressed on the skirt outline including sideline and hemline. Thirdly, the difference of silhouette was not distinct. The common point in 2D and 3D operations is that the representation of texture is relatively accurate and that is difficult to measure and manifest of thickness, the side. For more professional digitalizing in fashion industry, above all in the domain of 3D, it must be supplement the subdivided and differentiated mapping process according to the texture, deviating from the existing analog-based organization which has to designate the form and silhouette suitable for tissue.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.585-586
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• 2006

In this paper, we present a design, analysis, fabrication and performance test of the novel DoD metal-jet system for application to the high-density and high-temperature-melting materials. Based on the theoretical analysis, we design the metal-jet print head system and fabricate the metal-jet system, which can eject the droplet of lead-free metal solder in the high-temperature. In the experimental test, we set up the test apparatus for visualization of the droplet ejection and measure the Ejected droplet volume and velocity. As a result, the diameter, volume and the velocity of the ejected droplet are about $65-70{\mu}m$, 145-180 pl and 4m/sec. We also fabricate vertical and inclined 3D micro column structures using the present molten metal inkjet system. The measured geometries of the micro column structures are about height of $2,100{\mu}m$, diameter of $200{\mu}m$ and aspect ratio of 10.5 for vertical micro column and $1,400{\mu}m$ of height and $150{\mu}m$ of diameter for $65^{\circ}$-inclined micro column, respectively.