• Journal of Information Display
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• v.12 no.4
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• pp.213-217
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• 2011

Printing technologies were applied to fabricate a flexible organic thin-film transistor (OTFT) backplane for electrophoretic displays (EPDs). Various printing processes were adopted to maximize the figures of each layer of OTFT: screen printing combined with reverse offset printing for the gate electrodes and scan bus lines with Ag ink, inkjet for the source/drain electrodes with glycerol-doped Poly (3,4-ethylenedioxythiophene): Poly (styrenesulfonate) (PEDOT:PSS), inkjet for the semiconductor layer with Triisopropylsilylethynyl (TIPS)-pentacene, and screen printing for the pixel electrodes with Ag paste. A mobility of $0.44cm^2/V$ s was obtained, with an average standard deviation of 20%, from the 36 OTFTs taken from different backplane locations, which indicates high uniformity. An EPD laminated on an OTFT backplane with $190{\times}152$ pixels on an 8-in panel was successfully operated by displaying some patterns.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.5
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• pp.89-96
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• 2007

Inkjet printing has become one of the most attractive manufacturing techniques in industry. Especially inkjet printing technology will soon be part of the PCB (Printed Circuit Board) fabrication processes. Traditional printing on PCB includes screen printing and photolithography. These technologies involve high costs, time-consuming procedures and several process steps. However, by inkjet technology manufacturing time and production costs can be reduced, and procedures can be more efficient. PCB manufacturers therefore willingly accept this inkjet technology to the PCB industry, and are quickly shifting from conventional to inkjet printing. To produce the printed circuit board by the inkjet technology, it must be harmonized with conductive nano ink, printing process, system, and inkjet printhead. In this study, micro patterning of conductive line has been investigated using the piezoelectric printhead driven by a bipolar voltage signal is used to dispense 20-40 ${\mu}m$ diameter droplets and silver nano ink which consists of 1 to 50 nm silver particles that are homogeneously suspended in an organic carrier. To fabricate a conductive line used in PCB with high precision, a printed line width was calculated and compared with printing results.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.11.1-11.1
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• 2009

Bulk-heterojunction type organic photovoltaic cells have been remarkably improved due to the development of efficient donors and post treatment process. However, most of researchers have studied on the OPVs using spin-coating method during the past decade. To commercialize the OPVs, much cheaper printing process should be developed such as inkjet, screen, gravure, and so on. In this study, we have focused on the development of printing technology using Inkjet and Aerosol-Jet printing, which can offer reliable device performance. Finally, 4.5% power conversion efficiency can be achieved under AM 1.5 1sun light illumination, which is the highest value in printed OPVs. We reveal that substantial improvement can be realized by highly efficient bulk heterojunction after printing. Also, we can confirm these two printing methods are promising fabrication methods for large area OPVs. Also, flexible and large area (18 cm2) printed OPVs have been fabricated and device performance will be discussed in detail.

• Journal of Information Display
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• v.10 no.3
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• pp.131-136
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• 2009

This is a report on the fabrication of a flexible OTFT backplane for electrophoretic display (EPD) using a printing technology. A practical printing technology for a polycarbonate substrate was developed by combining the conventional screen and inkjet printing technologies with the wet etching and oxygen plasma processes. For the gate electrode, the screen printing technology with Ag ink was developed to define the minimum line width of ${\sim}5{\mu}m$ and the thickness of ${\sim}70nm$ with the resistivity of ${\sim}10^{-6}{\Omega}{\cdot}cm$, which are suitable for displays with SVGA resolution. For the source and drain (S/D) electrodes, PEDOT:PSS, whose conductivity was drastically enhanced to 450 S/cm by adding 10 wt% glycerol, was adopted. In addition, the modified PEDOT:PSS could be neatly confined in the specific S/D electrode area that had been pretreated with oxygen. The OTFTs that made use of the developed printing technology produced a mobility of ${\sim}0.13cm^2/Vs.ec$ and an on/off current ratio of ${\sim}10^6$, which are comparable to those using thermally evaporated Au for the S/D electrode.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.4.1-4.1
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• 2011

Recently, circuit printing technology has been considered as a promising alternative to conventional PCB fabrication, for it can greatly reduce the manufacturing costs. Even though printed circuit has many advantages over typical subtractive technology such as fewer processes, it has some disadvantages. The major problems are low adhesion and poor resolution. Efforts to overcome these problems have been mainly focused on ink developments with a limited success. And surface treatments showed some improvements. Therefore, various plasma treatments and primer coatings on plastic substrates have been tested. Plasma treatments using hydrocarbon gases including methane and propane improved the pattern quality of the inkjet printed circuit, which are further improved upon heating of substrate. On the other hand, there is little effect on the adhesion, which is improved only by a special primer coating. The adhesion of inkjet printed circuit has been increased more than 10 times upon treatment. As for the screen printed circuits, the overall effects are less significant since there is some organic binder in the ink. Nonetheless, the treatment has strong positive effects on pattern quality and adhesion. The adhesion of 1 kgf/cm2, which is comparable with those of the conventional PCB circuits, is possible through primer coating for both screen and inkjet printed circuits. The resulting circuit also showed good thermal, mechanical and electrical properties.

• Transactions on Electrical and Electronic Materials
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• v.12 no.6
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• pp.271-274
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• 2011

Screen-printed source and drain electrodes were used for a spin-coated and inkjet-processed zinc-tin oxide (ZTO) TFTs for the first time. Source and drain were silver nanoparticles. Channel length was patterned using screen printing technology. Different silver nanoinks and process parameters were tested to find optimal source and drain contacts Relatively good electrical properties of a screen-printed inkjet-processed oxide TFT were obtained as follows; a mobility of 1.20 $cm^2$/Vs, an on-off current ratio of $10^6$, a Vth of 5.4 V and a subthreshold swing of 1.5 V/dec.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.20.2-20.2
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• 2010

Recently inkjet printing technology has been developed in the areas of low cost fabrication in environmentally friendly manufacturing processes. Although inkjet printing requires the interdisciplinary researches including development of materials, manufacturing processes and printing equipment and peripherals, manufacturing a printhead is still core of inkjet technology. In this study, a piezoelectric driven DOD (drop on demand) inkjet printhead has been fabricated on three layers of the silicon wafer in MEMS Technology because of its chemical resistance to industrial inks, strong mechanical properties and dimensional accuracy to meet the drop volume uniformity in printed electronics and display industries. The flow passage, filter and nozzles are precisely etched on the layers of the silicon wafers and assembled through silicon fusion bonding without additional adhesives. The piezoelectric is screen-printed on the top the pressure chamber and the nozzle plate surface is treated with non-wetting coating for jetting fluids. Printheads with nozzle number of 16 to 256 have been developed to get the drop volume range from 5 pL to 80 pL in various industrial applications. Currently our printheads are successfully utilized to fabricating color-filters and PI alignment layers in LCD Flat Panel Display and legend marking for PCB in Samsung Electronics.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1806-1809
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• 2008

Study that form micro pattern by direct ink jet printing method is getting attention recently. Direct ink jet printing spout fine droplet including nano metal particle by force or air pressure. There is reason which ink jet printing method is profitable especially in a various micro-patterning technology. It can embody patterns directly without complex process such as mask manufacture or screen-printing for existent lithography. In this study, research of a technology that ejects fine droplet form of Pico liter and forms metal micro pattern was carried with inkjet head of piezoelectricity drive system. Droplet established pattern while ejecting consecutively and move on the surface at the fixed speed. Patterns formed in ink are mixed with organic solvent and polymer that act as binder. So added thermal hardening process after evaporate organic solvent at isothermal after printing. I executed high frequency special quality estimation of CPW transmission line to confirm electrical property of manufactured circuit board. We tried a large area printing to confirm application possibility of an ink jet technology.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1087-1090
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• 2008

This paper presents the electro-luminescence (EL) display lamp which is patterned on a curved surface by the pad printing method. The printing methods, including the gravure, screen, flexo, inkjet, and pad printing, have an advantage of one-step direct patterning. However, in general, the printing and semi-conductor process, except pad printing method, cannot be applied for patterning on a curved surface. Thus, in this paper, we used pad printing method for patterning an EL display lamp on a curved surface. The EL display lamp consists of 5 layers: Bottom electrode; Dielectric layer; Phosphor; Transparent electrode; Bus electrode. Finally, we printed EL display lamp on a dish, which has a radius of curvature 80mm. The EL display lamp was driven at AC 200V of 1kHz.

• 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].