• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.69-74
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• 2019

The aim of this work is to investigate the effect of the microtip length in a slot-die head on coating of a fine poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) stripe. To this end, we have employed a meniscus guide with a 150-㎛-wide microtip and performed roll-to-roll slot-die coatings by varying its length between 500 ㎛ and 50 ㎛. When the microtip length is 150 ㎛ or shorter, we have observed three unexpected phenomena; 1) though the solution spreads much wider than the microtip width, yet the coated stripe width is almost the same as the microtip width, 2) the stripe width decreases, but the stripe thickness is rather increased with increasing coating speed at a fixed flow rate, 3) we obtain stripes much narrower than the microtip width at high coating speeds. It is due to the fact that 1) the meniscus is not well controlled by a short microtip, 2) the main stream of solution from the outlet is very close to the substrate and thus the distributed solution along the head lip merges with the main stream, and 3) the solution is not spread over the entire microtip end at high coating speeds, causing a tiny wobble in the meniscus. Using the 150-㎛-wide and 250-㎛-long microtip, we have fabricated 153-㎛-wide and 94-nm-thick PEDOT:PSS stripe at the maximum coating speed of 13 mm/s. To demonstrate its applicability in solution-processable organic light-emitting diodes (OLEDs), we have also fabricated an OLED device with the fine PEDOT:PSS stripe and obtained strong light emission from it.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.87-87
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• 1996

• Journal of Biosystems Engineering
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• v.42 no.1
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• pp.1-11
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• 2017

Purpose: Methods: Three-dimensional CFD modeling was conducted to analyze the flow structure and discharge flow rate corresponding to the variation in the geometry of the flow channel in a microtube. Additionally, experiments were carried out, and the discharge flow rate was measured at various inlet pressures and inclination angles of the microtube. Results: The quantitative data of velocity distribution and discharge flow rate were obtained. As the width and length of the microtip increased, the discharge flow rate decreased significantly because of the increase in the loss of pressure along the microtube. As the depth of the microtip increased, the flow rate also increased because of the reduction in the flow resistance. However, in this analysis, the variation in the angle of the microtip did not influence the flow rate. From the experimental results, it was observed that the flow rate increased linearly with the increase in the inlet pressure, and the effects of the inclination angle were not clearly observed in those test cases. The values of the flow rate obtained from the experiments were significantly lower than that obtained from the CFD analysis. This is because of the distortion of the shape of the flow path inside the microtube during the fabrication process. The distortion of the flow path might decrease the flow cross-sectional area, and it would increase the flow resistance inside the microtube. The variation in the flow rate corresponding to the variation in the inlet pressure showed similar trends. Conclusions: Therefore, the results of the numerical analysis obtained from this study can be efficiently utilized for optimizing the shape of the microtip inside a microtube.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.49-50
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• 2000

5.2" microtip field emission displays (FEDs) with high voltage applications are fabricated. Nano-structural analysis on microtips is performed for the reliable operation of FEDs. Chemical compositions on the apex of microtips are fully analyzed. A charging mechanism on spacers is simulated and experimentally confirmed with micro-images. A gas-aging mechanism is also studied with integration step of FEDs. The brightness of more than 300 $cd/m^2$ is achieved. In addition, as a new concept, 9" color carbon nanotube FEDs (CNT-FEDs) are introduced using well-aligned carbon nanotubes on glass substrates by paste squeeze and surface treatment techniques. A number of carbon nanotubes, $5-10/{\mu}m2$, are uniformly distributed over a large area. The turn-on fields of 1 $V/{\mu}m$ and field emission currents of 1.5 mA at 3 $V/{\mu}m$ are acquired. Different mechanisms between microtip FEDs and CNT-FEDs are discussed.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.789-791
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• 1998

Numerical simulation has been performed on a microtip field emitter structure produced by employing a CMP technology. The field distributions are estimated by using a Maxwell 2D vector simulator and the electron trajectories are obtained by solving the equation of ballistic motion of emitted electrons. The beam width observed at the phosphor has been characterized as a function of the applied voltages and the gate-to-tip distance. It has also been investigated how the electron trajectory is changed by adopting the anode switching as well as the focus electrode.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.771-774
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• 2003

The mechanical properties of barrier ribs in PDP require quantification in order to control the defects and to increase the yield in the process. Several different types of rib materials were tested for hardness (H) and Young's modulus (E) with a microtip indenter (Berkovich type). For the assessment of fracture toughness of the rib, a macro Vikers indenter was used. The materials with 30wt% of filler were fired at between $490^{\circ}C$ and $570^{\circ}C$. As a result, the composite became fully densified at $520^{\circ}C$, which is near the T s (Littleton softening point) of glass frit. As the filler content increased, the fracture toughness also $(K_{IC})$ increased in the range of 0.60 to 2.63 $MPa{\cdot}m^{0.5}$ after sintering at $550^{\circ}C$. The results suggest that the application of a nano-indenter would be useful for testing the mechanical properties of barrier ribs.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1218-1219
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• 2008

Thin films (< 30 nm) of titanium carbide (TiC) are coated on carbon nanotubes (CNTs), which are directly grown on nano-sized ($\sim$ 500 nm in diameter) conical-type tungsten (W) tips, by employing an inductively coupled plasma-chemical vapor deposition (ICP-CVD) technique. Any modification in structural properties (such as length to diameter ratio, crystal quality, and growth behavior) of CNTs due to TiC-coating has been monitored by using high-resolution TEM, field-emission SEM, and Raman spectroscopy. Driving voltage for obtaining the same level of emission current in CNTs-emitter is significantly reduced by TiC-coating. It is also worthy of being noted that the degradation of emission current due to prolonged operation (up to 30 h) is remarkably suppressed by TiC-coating.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.743-748
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• 2010

Boron nitride (BN) and carbon nitride (CN) films, which have relatively low work functions and commonly exhibit negative electron affinity behaviors, were coated on carbon nanotubes (CNTs) by magnetron sputtering. The CNTs were directly grown on metal-tip (tungsten, approximately 500nm in diameter at the summit part) substrates by inductively coupled plasma-chemical vapor deposition (ICP-CVD). The variations in the morphology and microstructure of CNTs due to coating of the BN and CN films were analyzed by field-emission scanning electron microscopy (FE-SEM). The energy dispersive x-ray (EDX) spectroscopy and Raman spectroscopy were used to identify the existence of the coated layers (CN and BN) on CNTs. The electron-emission properties of the BN-coated and CN-coated CNT-emitters were characterized using a high-vacuum field emission measurement system, in terms of their maximum emission currents ($I_{max}$) at 1kV and turn-on voltage ($V_{on}$) for approaching $1{\mu}A$. The results showed that the $I_{max}$ current was significantly increased and the $V_{on}$ voltage were remarkably reduced by the coating of CN or BN films. The measured values of $I_{max}-V_{on}$ were as follows; $176{\mu}A$-500V for the 5nm CN-coated emitter and $289{\mu}A$-540V for the 2nm BN-coated emitter, respectively, while the $I_{max}-V_{on}$ of the as-grown (i.e., uncoated) emitter was $134{\mu}A$-620V. In addition, the CNT emitters coated with thin CN or BN films also showed much better long-term (up to 25h) stability behaviors in electron emission, as compared with the conventional CNT emitter.