• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.63-69
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• 2011

In this study, we report on the novel lithographic patterning method to fabricate organic thin film field effect transistors (OTFTs) based on photo and e-beam lithography with well-known silicon technology. The method is applied to fabricate pentacene-based organic field effect transistors. Owing to their solubility, sub-micron sized patterning of P3HT and PEDOT has been well established via micromolding in capillaries and inkjet printing techniques. Since the thermally deposited pentacene cannot be dissolved in solvents, other approach was done to fabricate pentacene FETs with a very short channel length (~30 nm), or in-plane orientation of pentacene molecules by using nanometer-scale periodic groove patterns as an alignment layer for high-performance pentacene devices. Here, we introduce $Al_2O_3$ film grown via atomic layer deposition method onto pentacene as a passivation layer. $Al_2O_3$ passivation layer on OTFTs has some advantages in preventing the penetration of water and oxygen and obtaining the long-term stability of electrical properties. AZ5214 and ma N-2402 were used as a photo and e-beam resist, respectively. A few micrometer sized lithography patterns were transferred by wet and dry etching processes. Finally, we fabricated micron sized pentacene FETs and measured their electrical characteristics.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.357-360
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• 2005

A novel wide viewing angle flexible liquid crystal display will be demonstrated. The crossed matrix-type micro-cell structure was adopted in this design. The LC domains were divided into four different tilted directions by the combination effect of pixel fringe field and crossed matrix type micro-cell. It can create four domains without rubbing process and form the cell gap without spacer. For flexible color fabrication, a novel inkjet printing technology is adopted. This cost effective wide viewing angle color flexible LCD technology can be a good solution for high performance flexible LCD.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.64.2-64.2
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• 2012

전자산업에서 소자를 제작하는 핵심공정으로써, 패턴을 형성하는 방식은 식각 마스크를 통해 이루어진다. 공정 순서는 원하는 물질을 증착한 후 사진공정 (photolithograpy)을 통하여 원하는 패턴의 감광제 식각마스크 (etch mask)를 형성하게 된다. 이후, 습식식각이나 건식식각을 통하여 물질의 불필요한 부분을 제거한 후 최종적으로 감광제 식각마스크를 제거하여 원하는 물질의 패턴을 얻게 된다. 최근에 소개된 잉크젯 프린팅 기술 (inkjet printing technology)은 나노 잉크를 이용하여 사진공정과 식각공정을 이용하지 않고, 직접 나노잉크를 분사하여 패턴을 형성하는 방법으로, 패터닝 공정을 단순화 시킬 수 있을 뿐만 아니라 각종 전자 산업의 환경오염물을 획기적으로 줄일 수 있는 친환경기술이다. 특히, OLED, O-TFT, RF-ID, PCB 분야 등 다양한 전자산업분야의 제조기술로서 응용하고자, 전도성 폴리머나 실버 (silver) 나노파티클 잉크를 이용한 전도성 라인 패터닝 (line patterning)에 관한 연구가 활발히 진행되고 있다. 본 강연에서는 친환경 생산공정기술 측면에서의 잉크젯기술을 분석하고, 기술의 구성요소, 응용분야, 기술 동향에 관해서 소개하고, 또한 현재 한국생산기술연구원에 진행하고 있는 잉크젯 프린팅 기술 기반의 인쇄전자 분야에 관한 내용을 소개한다.

• Clean Technology
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• v.7 no.3
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• pp.169-178
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• 2001

Textile printing prints around twenty bilion linear meters of textile each year. Rotary and flat bed screen printing requires pre and post treatments, leading to the loss of dyes and the environmental problems due to effluents. Digital ink jet printing can offer a solution to the existing problems, especially the environmental problems, in addition to its flexibility. Pigments are used as a dispersion inks in the digital inkjet textile printing. Molecular dynamic simulation like Stokesian dynamic simulation was employed to simulate the behavior of pigments and velocity distribution under the pressure driven flow in the printer nozzle. The simulation shows that the particle distribution in the flow are uniform if particle volume fraction is low, the ratio of nozzle and particle diameter is large, and the dimensionless average suspension velocity is low.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.57-62
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• 2014

Using flexible bismaleimide-triazine co-polymer as a substrate, inkjet-printed Cu films were also investigated for low-cost and process feasibility of flexible electronics. After annealing at $200^{\circ}C$ for 1 h under various reducing ambient, surface color was changed to red and electrical resistivity was decreased to the level of conductor under formic acid ambient. However, its resistivity was much higher than conventional copper films due to surface crack. In order to reduce the residual film stress after annealing, additional isothermal treatment was inserted before anneal hiring the stress relaxation applied in processes of amorphous materials. As a result, no surface crack was observed and electrical resistivity of $3.4{\mu}{\Omega}cm$ was measured after annealing at $230^{\circ}C$ with stress relaxation while electrical resistivity of $7.4{\mu}{\Omega}cm$ was observed after normal annealing without relaxation. The effect of stress relaxation was also confirmed by observing surface crack after decreasing the relaxation time to 0 min.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.20-26
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• 2015

Ceramic ink-jet printing technology in art tiles, decorated tablewares and other porcelain products has many advantages of fast and precision printing of various images with high efficiency and low cost. For the application to ink-jet printing, ceramic ink requires a stable dispersibility with nano-sized pigments. In this paper, characteristics of pink-red aqueous ceramic ink for ink-jet printing was demonstrated. $CaCr_{0.1}Sn_{0.8}SiO_5$ pigment was synthesized using solid state reaction and deagglomerated using attrition milling. The aqueous ceramic ink contains 10 wt% of the obtained $CaCr_{0.1}Sn_{0.8}SiO_5$ nanopigment with 0.4 wt% of sodium dodecyl sulfate (SDS) as a dispersion agent. Viscosity of $CaCr_{0.1}Sn_{0.8}SiO_5$ aqueous ceramic ink was adjusted using 0.18 wt% of polyvinyl alcohol (PVA) for a suitable jetting from the nozzle. The prepared pink-red ceramic ink showed a good jetting property with formation of a single sphere-shaped droplet after $180{\mu}s$ without a tail and satellite droplet.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.930_931
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• 2009

본 논문에서는 잉크젯 프린팅 기술을 이용하여 FPCB의 미세패턴 전극회로를 구현하였다. 이를 위하여 압전 잉크젯헤드에 의한 잉크드롭제어에 의해 전도성 잉크의 프린팅이 가능하도록 구현하였다. 그 동안 PCB 제작은 포토리소그라픽 공정에 의해 13단계 공정을 통하여 제작함으로써 폐수에 의한 환경오염, 비경제적인 비용, 긴 공정시간을 요구하였지만, 잉크젯 프린팅 기술을 적용함으로써 3단계로 공정간소화, 공정시간 단축, 비용절감의 효과를 얻을 수 있었다. 잉크젯 헤드는 당사에서 제작한 128노즐을 적용하였으며 이러한 결과 다음사양을 얻을 수 있었다. 인쇄 전극의 선폭 50um, 선폭 균일도 <15%, 패턴, 패턴 건조 큐어링 온도는 $150^{\circ}C$ 15분, 인쇄 속도 250mm/s, 720 dpi 분해능의 결과를 얻을 수 있었다.

• Particle and aerosol research
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• v.6 no.3
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• pp.131-138
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• 2010

Flexible electronics are the electronics on flexible substrates such as a plastic, fabric or paper, so that they can be folded or attached on any curved surfaces. They are currently recognized as one of the most innovating future technologies especially in the area of portable electronics. The conventional vacuum deposition and photolithographic patterning methods are well developed for inorganic microelectronics. However, flexible polymer substrates are generally chemically incompatible with resists, etchants and developers and high temperature processes used in conventional integrated circuit processing. Additionally, conventional processes are time consuming, very expensive and not environmentally friendly. Therefore, there are strong needs for new materials and a novel processing scheme to realize flexible electronics. This paper introduces current research trends for flexible electronics based on (a) nanoparticles, and (b) novel processing schemes: nanomaterial based direct patterning methods to remove any conventional vacuum deposition and photolithography processes. Among the several unique nanomaterial characteristics, dramatic melting temperature depression (Tm, 3nm particle~$150^{\circ}C$) and strong light absorption can be exploited to reduce the processing temperature and to enhance the resolution. This opens a possibility of developing a cost effective, low temperature, high resolution and environmentally friendly approach in the high performance flexible electronics fabrication area.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.2
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• pp.46-56
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• 2014

The aim of this reviews is to introduce the information concerning design of the UV-curable jet ink composition in order to provide a good adhesive property on non-porous surface. In order to clarify the viscosity dependence of flying speed for the UV curable jet ink, rheological analysis and observation of the flying state of the ink were carried out. The relationship between ink formulas and adhesive property on non-porous surface was investigated. It was examined the adhesive property of radical polymerization type UV curable jet ink included hydrogen abstraction type photo-initiator, it was expected that the strong adhesive strength can be obtained between the ink and non-porous surface in this study. UV curable jet ink with a slight amount of water was prepared. Optimum ratio of the cationic polymerization type UV curable jet ink shows an adequate adhesive strength towards two kinds of non-porous surface such as glass, poly(vinyl chloride) when tests were conducted on the ink jet-printing test machine.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.118-122
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• 2009

Organic thin film transistors with a pentacene active layer and various polymer gate insulators were fabricated and their performances were investigated. Characteristics of pentacene thin film transistors on different polymer substrates were investigated using an atomic force microscope (AFM) and x-ray diffraction (XRD). The pentacene thin films were deposited by thermal evaporation on the gate insulators of various polymers. Hexamethyldisilazane (HMDS), polyvinyl acetate (PVA) and polymethyl methacrylate (PMMA) were fabricated as the gate insulator where a pentacene layer was deposited at 40, 55, 70, 85, 100 oC. Pentacene thin films on PMMA showed the largest grain size and least trap concentration. In addition, pentacene TFTs of top-contact geometry are compared with PMMA and $SiO_2$ as gate insulators, respectively. We also fabricated pentacene TFT with Poly (3, 4-ethylenedioxythiophene)-Polysturene Sulfonate (PEDOT:PSS) electrode by inkjet printing method. The physical and electrical characteristics of each gate insulator were tested and analyzed by AFM and I-V measurement. It was found that the performance of TFT was mainly determined by morphology of pentacene rather than the physical or chemical structure of the polymer gate insulator