• 한국전기전자재료학회논문지
• /
• 제26권10호
• /
• pp.745-753
• /
• 2013

Performance of organic light-emitting diodes incorporating microlens array was simulated using a Light Tools software. Use of microlens array can help the light to escape out of the device. We simulated a reference device that is consisted of reflection layer, emissive layer, and flat transparent substrate. And in this reference device, outcoupled efficiency of 22% was obtained. Several shapes of microlens were applied such as hemisphere, trapezoid, cone, and rectangular parallelepiped. The results showed the improvement of outcoupled efficiency of the device with microlens compared to that of the reference one. And from the analyses of the simulated data, the obtained appropriate shape of microlens is hemisphere, and the improvement of the device with hemispherical lens is 57% higher than that of the reference one.

• 대한기계학회논문집A
• /
• 제26권9호
• /
• pp.1923-1930
• /
• 2002

In this paper, we present modeling and simulation of microlens formation by means of a deep X-ray lithography followed by a thermal treatment of a PMMA (Polymethylmethacrylate) sheet. According to this modeling, X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. In this modeling, the free volume theory including the relaxation process during the cooling process was considered. The simulation results indicate that the modeling in this study is able to predict the fabricated microlens shapes and the variation pattern of the maximum heights of microlens which depends on the conditions of the thermal treatment. The prediction model could be applied to optimization of microlens fabrication process and to designing a micro mold insert for micromolding processes.

• 한국전기전자재료학회논문지
• /
• 제27권5호
• /
• pp.307-311
• /
• 2014

Because of a waveguiding effect and total internal reflection caused by a difference in refractive indices, only 20% of generated light is emitted to the air and the rest is trapped or absorbed in the device. An improvement of outcoupled efficiency of organic light-emitting diodes was studied using a microlens array. Mold of microlens array was fabricated by using photo-lithography with the AZ9260 photoresist, and the microlens array was formed onto the glass substrate using the UV curing agent named ZPU13-440. Device structure consists of microlens/glass/ITO/TPD/$Alq_3$/LiF/Al. It was found that there is an improvement of external quantum efficiency by about 20% at the same current density for the device with the microlens array compared to that of the reference one. Simulated outcoupled efficiency shows the improvement by about 20% for the device with the microlens array compared to that of the reference one. These results are consistent with the experimental ones.

• 마이크로전자및패키징학회지
• /
• 제20권2호
• /
• pp.23-28
• /
• 2013

마이크로렌즈 어레이는 광학 시스템의 기본 부품으로, 사용 목적에 따라 초점거리가 다르게 제작되며, 대체로 긴 초점거리의 렌즈들이 많이 제작되고 있다. 본 논문에서는 졸겔(sol-gel) 내부에 들어있는 형광으로 염색된 물질을 관찰하기 위하여 마이크로렌즈 어레이를 제작하였다. 일반적으로 형광 현미경에서 관찰되는 형광 빛은 그 강도가 약하지만 마이크로렌즈를 이용할 경우 빛을 집중시켜 선명한 관찰이 가능하게 한다. 이를 실현시키기 위해 photoresist thermal reflow법을 사용하여 초점 거리가 짧은 마이크로렌즈를 제작하였으며, 렌즈의 형상 관련 오차를 측정하였다. 측정 오차에 기반을 둔 포토마스크 보정 및 스핀 코팅 조건을 조정하여 적합한 마이크로렌즈의 직경과 형상을 구현하였다.

• 반도체디스플레이기술학회지
• /
• 제21권2호
• /
• pp.25-31
• /
• 2022

By an aid of needle coating, we have fabricated a spherical microlens array using poly(methyl methacrylate) for potential applications in light extraction of organic light-emitting diodes. With an attempt to achieve high-density and high-aspect-ratio microlens arrays, we have investigated the coating behaviors by varying the material parameters such as the solute concentration and wettability of the poly(methyl methacrylate) solution and process parameters such as the dwell time of needle near the substrate, retract distance of needle from the substrate, and coating gap between the needle and substrate. Under the optimized coating conditions, it is demonstrated that high-aspect-ratio microlens arrays can be obtained using a coating solution with high solute concentration and a small amount of a hydrophobic solvent. It is found that the diameter and height of microlens array are decreased with increasing poly(methyl methacrylate) concentration, yet the overall aspect ratio is rather enhanced. By the addition of 5 wt% hexylamine in 35 wt% poly(methyl methacrylate) solution, we have achieved a spherical microlens with the height of 7.7 ㎛ and the width of 94.24 ㎛ (the aspect ratio of 0.082). To estimate the capability of light extraction by the microlens array, we have performed ray tracing simulations and demonstrated that the light extraction efficiency of organic light-emitting diode is expected to be enhanced up to 24%.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2004년도 추계학술대회 논문집
• /
• pp.840-843
• /
• 2004

UV molding is a process for integrating micro/nano polymeric optical components on optoelectronic modules. In the present study, a microlens array for vertical cavity surface emitting laser(VCSEL) to fiber coupling was designed, integrated and tested. At the design stage, design variables ware optimized to maximize the coupling efficiency, and tolerance analysis was carried out. At the integration stage, the UV transparent mold was fabricated and the microlens array on VCSEL array was integrated by UV molding process. Finally the coupling efficiency of VCSEL to fiber was measured and analyzed.

• 소성∙가공
• /
• 제13권3호
• /
• pp.290-295
• /
• 2004

Mircolens and microlens V-groove are realized using a novel fabrication technology based on the exposure of a resist, usually PMMA, to deep X-rays and subsequent thermal treatment and inclined deep X-ray lithography, respectively. The fabrication technology is very simple and produces microlenses and microlens V-groove with good surface roughness of several nm. The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses were produced through the effects of volume change, surface tension, and reflow during thermal treatment of irradiated PMMA. Microlenses were produced with diameters ranging from 30 to $1500\mu\textrm{m}$. The surface X-ray mask is also fabricated to realize microlens arrays on PMMA sheet with a large area. The size of the micro V-groove is fabricated in the range of 12~$60\mu\textrm{m}$.

• 한국광학회지
• /
• 제20권2호
• /
• pp.118-122
• /
• 2009

PET 필름 위에 LCD 백라이트의 프리즘 집광시트의 역할을 대체 할 수 있는 microlens array(MLA) 시트를 설계하고 제작하였다. Photoresist thermal reflow 공정으로 두께 $100{\mu}m$ PET 필름 위에 MLA를 제작하였고, 노광 시간과 reflow의 온도, 시간 등의 변수에 따른 MLA의 형상 변화를 측정하였다.

• 정보저장시스템학회논문집
• /
• 제2권4호
• /
• pp.236-239
• /
• 2006

Glass micro molding process is the most suitable process for fabricating high precision glass microlens amy at low cost. A new glass micro molding process was proposed. Tungsten carbide mold was fabricated by imprinting and sintering process to overcome the difficulties of the conventional process. In the glass micro molding process, process conditions such as processing temperature and compression force were changed. Geometrical properties of the replicated glass microlens array were measured and compared at variety process conditions. The condition of glass micro molding process was optimized. The experimental result showed that developed process was effective to produce a glass microlens array.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 추계학술대회 논문집
• /
• pp.882-884
• /
• 2005

A new rectangular shape microlens array having high sag for solid-state lighting is presented. Proposed microlens, which has high sag, over $375{\mu}m$ and large diameter, over 3 mm can enormously enhance output optical extraction efficiency. Rectangular shape of microlens can maximize the fill factor of light-emitting-diode (LED) package and minimize the optical loss at the same time. This wafer level microlens array is fabricated on LED package. It has many advantages in optical properties, low cost, high aligning accuracy, and mass production.