• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.474-480
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• 2008

In order to make full color cholesteric displays, color filter-less R, G, B sub-pixel structured cholesteric LC cells have been studied. To make R, G, B colors, UV induced pitch variant chiral dopant was added to cholesteric LC mixtures. The concentration of the photo-sensitive chiral dopant was adjusted so that the initial state showed blue color and the color was changed from blue to green and red with increase of UV irradiation to the cholesteric cells. To prevent the mixing of R, G, B reflective sub-pixel liquid crystals, separation walls were formed using negative photo resister in boundary area between sub-pixels, Through the optimization of the material concentrations and UV irradiation condition, vivid R, G, B colors were achieved.

• Polymer(Korea)
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• v.35 no.1
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• pp.87-93
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• 2011

We developed a fluorene-containing multifunctional binder polymer for LCD color filter resist, and employing the binder polymer, carbon black based black photoresist (CBR) was prepared in order to apply it to the black matrix (BM). To obtain the multifunction of the binder polymer, we synthesized bisphenol fluorene epoxy acrylate-containing unsaturated polyester and identified the binder polymer structure with $^1H$ NMR, GPC and FTIR. The corresponding BFEA-polyester binder polymer was compared with the commercially available acryl binder toward the application to the CBR. From the BM lithography test, we found that the synthesized BFEA-polyester binder had better photocrosslinking capability and alkali solubility. In addition, the newly developed binder gave a good process margin, good resolution and adhesion property on a glass substrate.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.346.1-346.1
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• 2016

본 연구에서는 열처리(Thermal Dewetting Process)와 빗각 증착(Oblique angle deposition)을 이용하여 비주기 서브파장 구조물을 마이크로 렌즈 형태의 유리 기판 상부에 제작하였다. 먼저 $2{\times}2cm2$ 크기의 유리 기판에 기존 리소그래피 공정으로 원기둥 형태의 감광액을 형성한다. 이후 Hot-plate로 $180^{\circ}C$에서 90초간 열을 가해 지름이 $20{\mu}m$인 반구형태로 변형시킨 뒤 반응성이온식각 공정을 진행하여 마이크로 렌즈를 제작한다. 렌즈의 표면에 나방 눈 구조를 형성하기 위해 전자빔 증착으로 15nm의 은 박막을 쌓은 뒤 $500^{\circ}C$에서 1분간 열처리 공정을 진행하였다. 열이 가해졌을 때 은 박막은 표면자유에너지를 최소화하기 위해 나노 크기의 덩어리진 입자 형태로 변화한다. 여기서 형성되는 나노입자의 크기가 렌즈 표면 중심에서 가장자리로 갈수록 작아진다는 것을 주사전자현미경을 통해 확인하였다. 증착 각도가 증가할수록 열처리 공정 후의 은 나노입자의 크기가 점점 작아진다는 것을 검증하기 위해 은 박막의 증착 각도를 $0^{\circ}$, $35^{\circ}$, $55^{\circ}$, $70^{\circ}$로 증착 후 열처리 공정을 진행하여 확인하였다. 비스듬하게 증착되어 형성된 박막은 다공형태로 낮은 밀도를 가지는데 이는 박막 두께 감소를 일으킨다. 따라서 증착 각도가 증가할수록 열처리 공정 후의 은 나노입자의 크기는 점점 작아진다. 이후 은 나노입자를 마스크로 하여 다시 반응성이온식각 공정을 진행하였으며 식각 후 나머지 은 나노입자들은 HNO3용액에서 1분간 처리하여 제거하였다. 제작된 구조물의 평균 직경과 크기는 각각 ~220nm 및 ~250nm인 것으로 확인하였다. 위와 같은 공정을 통해 다양한 크기를 가진 비주기 서브파장 구조물을 제작할 수 있다. 구조물의 주기가 파장 길이보다 짧을 경우 분산이 최소화되며 넓은 파장 대역에서 무반사 효과를 얻을 수 있다. 이 공정은 마스크를 통한 리소그래피의 한계를 극복할 수 있으며 여러 곡면형 표면에 적용가능한 장점이 있다. 또한 프리즘, 렌즈, 광섬유와 같은 광소자의 광투과율을 향상시키는데 이용될 수 있다.

• 전자공학회논문지 IE
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• v.44 no.2
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• pp.26-31
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• 2007

A surface treatment was performed after the screen printing of a carbon nanotube paste for obtaining the carbon nanotube field emission array(CNT FEA) on the soda-lime glass substrate. In this experiment, Ar ion bombardment was applied as an effective surface treatment method. After making a cathode electrode on the glass substrate, photo sensitive CNT paste was screen-printed, and then back-side was exposure by uv light. Then, the exposed CNT paste was selectively remained by development. After post-baking, the remained CNT paste was bombarded by accelerated Ar ions for removing some binders and exposing only CNTs. As results, the field emission characteristics were strongly depended on the accelerating energy. At 100 eV, the emission was highest and as the acceleration energy increases more then 100 eV, the emission decreased. This was due to the removal of CNT itself as well as binders.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.77-84
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• 2006

With the development of micro/nano spacecraft, concepts of micro propulsion are introduced for orbit transfer and drag compensation as well as attitude control. Micro solid propellant thruster has been attention as one of possible solution for micro thruster. In this paper, micro solid propellant thruster is introduced and research on basic components of a micro solid propellant thruster is reported. Micro Pt igniter was fabricated through negative patterning and quantitative effect of geometry was estimated. The characteristic of HTPB/AP solid propellant was investigated to measure the homing velocity. A combustion chamber was fabricated by means of anisotropic etching of photosensitive glass. Finally, micro solid propellant thrusters having various geometries were fabricated and tested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.417-424
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• 2009

A micro-mixer with a quasi-active rotor was fabricated, and mixing characteristics were evaluated. The proposed micro-mixer combines an active type micro-mixer with a passive type micro-mixer. The micro-rotor, which is a moving part of an active type micro-mixer, is added in a micro-chamber of a passive type vortex micro-mixer. The rotor rotated by inflows tangent to a chamber, causing strong perturbations. The micro-mixers were fabricated using photosensitive glass. Mixing efficiency of the micro-mixers was measured using an image analysis method. Mixing efficiency and characteristics of the micro-rotor mixer were compared with the vortex micro-mixer without a rotor. Mixing efficiency was reduced as Reynolds number increased at a low Reynolds number due to decrease of residence time. Mixing efficiency at higher Reynolds number, on the other hand, was improved even though residence time decreased since the contact surface between fluids increased by twisted flow. The perturbation induced by rotating rotor at greater than Re 200 improved the efficiency of the rotor mixer.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.7
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• pp.36-42
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• 2000

Some polarization characteristics of reflection type photopolymer are investigated. Photopolymer on a Mylar substrate alters an incoming linearly polarized laser beam to an elliptical polarization. Due to the rotation of the polarization, the recording gratings show different diffraction efficiencies. The rotation angle is of order of 10-50% for the tested samples. It is found that the polymer layer does not changes the polarization direction but the Mylar substrate alone distorts the incoming polarization to a comparable degree. As align the polarization states of photopolymers to be parallel with a laser using a He-Ne laser(633nm), which is not sensitive to that material, it was possible to make high diffraction efficiency gratings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1642-1648
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• 2006

This paper describes enhancement of the mixing efficiency of a multilamination micro mixer by adding a number of recirculation zones downstream of the mixing zone. Numerical simulation was employed to estimate the mixing efficiency and the pressure drop under various conditions. Numerical results indicated that recirculation micro mixer brought about not only the increase of the mixing efficiency but also the decrease of the pressure drop. Micro mixers were fabricated using photosensitive glass by anisotropic wet etching technique. The width and height of the micro channel were $150{\mu}m$ and $500{\mu}m$, respectively. The performance of micro mixer was measured using color intensity variation of the fluid. Except for extremely low Re below 40, the recirculation micro mixer of the present study showed improved mixing. And the enhancement of the mixing increased as Re rose. When Re increased beyond 400, more than 90% of the mixing was observed in the experiment.

• Journal of the Korean Society of Visualization
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• v.9 no.2
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• pp.34-39
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• 2011

This paper presents a novel direct fabrication method of the thin metal film RTD temperature sensor array on an arbitrary curved surface by using MEMS technology to measure a distributed temperature field up to $300^{\circ}C$ without disturbing a fluid flow. In order to overcome the difficulty in the three dimensional photography of sensor patterning, the UV pre-irradiated photosensitive dry film resist technology has been developed newly. This method was applied to the fabrication of the temperature sensor array on a glass tube, which is arranged parallel and transverse to a main flow. Gold was used as a temperature sensing material. The resistance change was measured in a thermally controlled oven by increasing the environmental temperature. The linear increase in resistance change and a constant slope were obtained. Also, the sensitivity of each RTD temperature sensor was evaluated.

• Polymer(Korea)
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• v.31 no.5
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• pp.442-446
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• 2007

Alkali soluble and photo-curable polyesters were prepared from fluorene epoxy acrylate and various aromatic dianhydrides. To make a black matrix for LCD color-filter application, photo-resist solution was made by mixing synthesized polyester as binder, carbon black as pigment, initiator and multifunctional monomer in solvent. Black matrix pattern was formed on the glass substrate by lithography process. In this study, we synthesized various polyester-based binder polymers for LCD color-filter applications, and compared the analytical properties of those polymers and lithography patterns.