• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.235-236
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• 2009

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.709-714
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• 2014

Reverse-offset printing is one of the technologies that can be used for patterning fine features of the order of a few micrometers for printed electronics. In reverse-offset printing, a coated ink film is transferred to a blanket made of elastomer-like poly-dimethylsiloxane. Then, the blanket is impressed onto a clich$\acute{e}$ that has intaglio patterns. The blanket is deformed by penetrating the intaglio of the clich$\acute{e}$ according to the printing pressure. Excessive deformation of the blanket can cause printing defects upon touching the bottom of the intaglio pattern, especially in large patterns. In this paper, we modelled the deformation of the blanket using the finite element method. Considering the actual printing parameters, a condition for fabricating a clich$\acute{e}$ is proposed to prevent defects by the deformation of the blanket.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.263-272
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• 2013

Printed electronics creates electrically functional devices by printing on variety of substrates. Printing typically uses common printing equipment or other low-cost equipment suitable for defining patterns on material, such as screen printing, flexography, gravure, offset lithography and inkjet. Compared to conventional manufacturing of microelectronics, printed electronics is characterized by simpler and more cost-effective fabrication of high and low volume products. Now there is huge effort towards printing many other more functional components, from displays to transistors to photovoltaic cells, using the full range of printing technologies - from inkjet to roll to roll analogue print techniques. The market for printed electronics will rise from $1.99 billion in 2010 to $55.10 billion in 2020. In 2030, this industry could be $300 billion - larger than the silicon semiconductor industry - from lighting to displays[8].

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.476-481
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• 2012

Among the various roll-to-roll printing technologies such as gravure, gravure-offset, and reverse offset printing, reverse offset printing has the advantage of fine patterning, with less than 5 ${\mu}m$ line width. However, it involves complex processes, consisting of 1) the coating process, 2) the off process, 3) the patterning process, and 4) the set process of the ink. Each process demands various ink properties, including viscosity, surface tension, stickiness, and adhesion with substrate or clich$\acute{e}$; these properties are critical factors for the printing quality of fine patterning. In this study, Ag nano ink was developed for reverse offset printing and the effect of polyvinylpyrrolidone(PVP), used as a capping agent of Ag nano particles, on the printing quality was investigated. Ag nano particles with a diameter of ~60 nm were synthesized using the conventional polyol synthesis process. Ethanol and ethylene glycol monopropyl ether(EGPE) were used together as the main solvent in order to control the drying and absorption of the solvents during the printing process. The rheological behavior, especially ink adhesion and stickiness, was controlled with washing processes that have an effect on the offset process and that played a critical role in the fine patterning. The electrical and thermal behaviors were analyzed according to the content of PVP in the Ag ink. Finally, an Ag mesh pattern with a line width of 10 ${\mu}m$ was printed using reverse offset printing; this printing showed an electrical resistivity of 36 ${\mu}{\Omega}{\cdot}cm$ after sintering at $200^{\circ}C$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.163-164
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• 2013

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1274-1274
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• 2008

In this report, the effect of substrate temperature on the electrical properties of ink-jet printed triisopropylsilyl (TIPS) pentacene organic thin-film transistors (OTFTs) has been investigated. The electrical properties such as mobility and on/off ratio were decreased as the substrate was heated above room temperature. The field-effect mobility of decreased from $10^{-2}cm^2/Vs$ to $10^{-5}cm^2/Vs$ and the on/off ratio decreased from $10^6$ to $10^4$ when the substrate temperature was heated from room temperature to 60$^{\circ}C$.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1144-1149
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• 2008

Converting technology has developed to print information for the decades. Recently, this technology (like gravure, gravure-offset) is rising as an alternative way for mass production of printed electronics such as RFID, solar cell. For the width of printing line is under 10 microns, registration error should be minimized less than several microns. Tension disturbance is main cause of registration error and this should be minimized before the substrate is transported into printing zone. With PI controller, it is possible to suppress the disturbance within 2% of operating tension. But register error appears more than 10 micron using PIcontroller considering noise. So LQG controller is needed as an alternative control method. In this paper, the comparision of PI and LQG controller in the converting machine including measured noise and tension disturbance is presented. It is shown that the LQG controller is more suitable for precision tension control in printed electronics.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.17.2-17.2
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• 2010

Printed electronics is an emerging technology to realize various microelectronic devices via a cost-effective method. Here we demonstrated a high performance of p-channel and n-channel top-gate/bottom contact polymer field-effect transistors (FETs), and applications to elementary organic complementary inverter and ring oscillator circuits by inkjet processing. We could obtained high field-effect mobility more than $0.4\;cm^2/Vs$ for both of p-channel and n-channel FETs, and successfully measured inkjet-printed polymer inverters. The performance of devices highly depends on the selection of dielectrics, printing condition and device architecture. Optimized CMOS ring oscillators with p-type and n-type polymer transistors showed as high as 50 kHz operation frequency. This research was financially supported by development of next generation RFID technology for item level applications (2008-F052-01) funded by the ministry of knowledge economy (MKE).

• Journal of the Korean Society for Precision Engineering
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• v.31 no.6
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• pp.491-495
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• 2014

We developed a compact high-precision slot-die coating machine for thin-film deposition on a flexible substrate. For smooth and precise coating, air-bearing and linear motor system were employed to minimize velocity ripple. The gap control mechanism is specially designed to have repeatability of gap between nozzle and substrate under 1 ${\mu}m$. Due to extremely precise gap control, the machine can coat thin-films down to 50 nm with $200mm{\times}100mm$ size. A thin film of Ag nano-particle ink is coated for demonstration.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.239-242
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• 2009

$Sr_2Si_5N_8:Eu^{2+}$, one of the most recently developed phosphors for use in white light emitting diodes, exhibits a two-peak emission. Namely, the emission band of $Sr_2Si_5N_8:Eu^{2+}$ is deconvoluted into two Gaussian peaks irrespective of the $Eu^{2+}$ concentration. We examined the two-peak emission of $Sr_2Si_5N_8:Eu^{2+}$ by analyzing the time-resolved photoluminescence spectra. We revealed that the two-peak emission was closely associated with the energy transfer taking place between $Eu^{2+}$ activators located at two different crystallographic sites in the $Sr_2Si_5N_8$ structure. The experimental results coincided well with the rate equation model involving the crystallographic information of the host.