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Mechanical Modeling of Rollable OLED Display Apparatus Considering Spring Component
마부수,조우성,김완선,김택수 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.2
Flexible displays have been evolved into curved, foldable, and rollable as the degree of bending increases. Due to the presence of brittle electrodes (e.g. indium-tin oxide (ITO)) that easily cracked and delaminated under severe bending deformation, lowering mechanical stress of the electrodes has been critical issue. Because of this, mechanical stress of brittle electrode in flexible displays has been analyzed mostly in terms of bending radius. On the other hand, in order to make rollable display, various mechanical components such as roller and spring are needed to roll-up or extend the screen for the rollable display apparatus. By these mechanical components, brittle electrode in the rollable display is subjected to the excessive tensile stress due to the retracting force as well as the bending stress by the roller. In this study, mechanical deformation of rollable OLED display was modeled considering boundary conditions of the apparatus. An analytical modeling based on the classical beam theory was introduced in order to investigate the mechanical behavior of the rollable display. In addition, finite element analysis (FEA) was used to analyze the effect of mechanical components in the apparatus on the brittle electrode. Furthermore, a strategy for improving the mechanical reliability of the rollable display was suggested through controlling the stiffness of adhesives in the display panel.
유기 나노 보강층을 활용한 유연 디스플레이용 절연막의 기계적 물성 평가
오승진,마부수,양찬희,송명,김택수,Oh, Seung Jin,Ma, Boo Soo,Yang, Chanhee,Song, Myoung,Kim, Taek-Soo 한국마이크로전자및패키징학회 2021 마이크로전자 및 패키징학회지 Vol.28 No.3
최근 유연 디스플레이에 관한 대중의 관심이 증대됨에 따라 롤러블(rollable), 폴더블(foldable) 디스플레이와 같은 우수한 폼 팩터(form factor)를 지닌 차세대 유연(flexible) 디스플레이가 주목받고 있다. 유연 디스플레이의 기계적 신뢰성 확보 측면에서, 내부 절연막으로 활용되는 실리콘 질화물(SiN<sub>x</sub>) 박막은 구동 중 발생하는 응력에 매우 취약하므로 기계적 물성을 정확히 파악하여 파손을 예측하고 패널의 전기적 단락을 방지하는 것이 중요하다. 본 논문에서는, ~130 nm, ~320 nm 두께의 SiN<sub>x</sub> 박막 박막 상부에 ~190 nm 두께의 유기 나노 보강층(PMMA, PS, P3HT)을 코팅하여 이중층 구조로 인장함으로써 매우 취성한 SiN<sub>x</sub> 박막의 탄성 계수와 인장 강도 및 연신율을 측정하는 데 성공하였다. 챔버 압력 및 증착 파워를 조절한 공정 조건(A: 1250 mTorr, 450 W/B: 1000 mTorr, 600 W/C: 750 mTorr, 700 W)을 통해 제작된 ~130 nm SiN<sub>x</sub> 의 탄성계수는 A: 76.6±3.5, B: 85.8±4.6, C: 117.4±6.5 GPa로, ~320 nm SiN<sub>x</sub>는 A: 100.1±12.9, B: 117.9±9.7, C: 159.6 GPa로 측정되었다. 결과적으로, 동일 공정 조건 하에서 SiN<sub>x</sub> 박막의 두께가 증가할수록 탄성 계수가 증가하는 경향을 확인하였으며, 유기 나노 보강층을 활용한 인장 시험법은 파손되기 쉬운 취성 박막의 기계적 물성을 높은 정밀도로 측정하는 데 효과적이었다. 본 연구에서 개발된 방법은, 취약한 디스플레이용 박막의 정량적인 기계적 물성 파악을 가능케하여 강건한 롤러블, 폴더블 디스플레이의 설계에 이바지할 수 있을 것으로 기대한다. Recently, rollable and foldable displays are attracting great attention in the flexible display market due to their excellent form factor. To predict and prevent the mechanical failure of the display panels, it is essential to accurately understand the mechanical properties of brittle SiN<sub>x</sub> thin films, which have been used as an insulating film in flexible displays. In this study, tensile properties of the ~130 nm- and ~320 nm-thick SiN<sub>x</sub> thin films were successfully measured by coating a ~190 nm-thick organic nano-support-layer (PMMA, PS, P3HT) on the fragile SiN<sub>x</sub> thin films and stretching the films as a bilayer state. Young's modulus values of the ~130 nm and ~320 nm SiN<sub>x</sub> thin films fabricated through the controlled chamber pressure and deposition power (A: 1250 mTorr, 450 W/B: 1000 mTorr, 600 W/C: 750 mTorr, 700 W) were calculated as A: 76.6±3.5, B: 85.8±4.6, C: 117.4±6.5 GPa and A: 100.1±12.9, B: 117.9±9.7, C: 159.6 GPa, respectively. As a result, Young's modulus of ~320 nm SiN<sub>x</sub> thin films fabricated through the same deposition condition increased compared to the ~130 nm SiN<sub>x</sub> thin films. The tensile testing method using the organic nano-support-layer was effective in the precise measurement of the mechanical properties of the brittle thin films. The method developed in this study can contribute to the robust design of the rollable and foldable displays by enabling quantitative measurement of mechanical properties of fragile thin films for flexible displays.
오승진,마부수,김형준,양찬희,김택수,Oh, Seung Jin,Ma, Boo Soo,Kim, Hyeong Jun,Yang, Chanhee,Kim, Taek-Soo 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.3
차세대 디스플레이 시장을 선도하기 위해서는 롤러블(rollable), 폴더블(foldable) 디스플레이와 같은 플렉서블(flexible) OLED 디스플레이의 상용화 및 양산화가 필수적이나, 실제 공정 및 굽힘 과정에서 발생하는 극심한 박막 내부 응력 변화로 인한 기계적 파손 문제가 심각한 상황이다. 따라서, 플렉서블 디스플레이 구조에 사용되는 박막 재료의 기계적 물성을 파악하는 것은 제품의 강건한 설계 및 구조 최적화에 필수적이다. 본 논문에서는 물 표면 플랫폼을 이용한 나노 박막 인장 시험법을 적용하여 플렉서블 디스플레이 패널에 적용되는 금속 및 세라믹 박막 소재들의 인장 물성을 정량적으로 측정하였다. 스퍼터링(Sputtering)으로 증착된 Mo, MoTi 나노 박막과, 플라즈마 강화 화학 기상 증착법(Plasma Enhanced Chemical Vapor Deposition, PECVD)으로 증착된 SiN<sub>x</sub> 나노 박막의 탄성 계수와 인장 강도 및 연신율을 측정하는 데 성공하였다. 결과적으로 박막의 증착 조건 및 두께에 따라 기계적 물성이 크게 변화할 수 있음을 확인하였으며, 측정된 인장 물성은 기계적으로 강건한 롤러블, 폴더블 디스플레이의 설계를 위한 응력 해석 모델링 데이터로 활용될 수 있을 것으로 기대한다. Commercialization of flexible OLED displays, such as rollable and foldable displays, has attracted tremendous interest in next-generation display markets. However, during bending deformation, cracking and delamination of thin films in the flexible display panels are the critical bottleneck for the commercialization. Therefore, measuring mechanical properties of the fragile thin films in the flexible display panels is essential to prevent mechanical failures of the devices. In this study, tensile properties of the metal and ceramic nano-thin films were quantitatively measured by using a direct tensile testing method on the water surface. Elastic modulus, tensile strength, and elongation of the sputtered Mo, MoTi thin films, and PECVD deposited SiN<sub>x</sub> thin films were successfully measured. As a result, the tensile properties were varied depending on the deposition conditions and the film thickness. The measured tensile property values can be applied to stress analysis modeling for mechanically robust flexible displays.
김건우,이영웅,마부수,김진석,박진수,이승진,송명,김택수,우한영,김범준 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
In this study, a novel acceptor-donor-acceptor (A-D-A) triad type molecule, 5TRh-PCBM, which has an oligothiophene segment as the central core and fullerene-derivatives as the end groups, is designed as a compatibilizer for enhancing the thermal stabilities and mechanical properties of efficient organic solar cells while increasing their power conversion efficiencies (PCEs). To examine the effectiveness of this molecular compatibilizer, OSCs with different donors (PTB7-Th, PBDB-T, and P3HT) have been fabricated and tested, with addition of various amounts of 5TRh-PCBM. The addition of 5 and 10 wt% of 5TRh-PCBM significantly enhance the thermal and mechanical stabilities of all tested PSCs. Our comprehensive investigations have revealed the effects of 5TRh-PCBM on the optical, morphological, photovoltaic, and mechanical properties of molecularly engineered OSCs.
유호선,Austin L. Jones,마부수,김택수,John R. Reynolds,김범준 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
In this study, two wide-bandgap PM7 derivatives are developed via simple structural modification of the fused-accepting unit (i.e., two ester groups on the outer thiophenes (PM7 D1) and on the central thiophene (PM7 D2)). This simple modification creates a higher-energy light absorption window, providing better complementary light harvesting with P(NDI2HD-Se). As a result, PM7 D1-based all-polymer solar cells (all-PSCs) exhibit a high power conversion efficiency (PCE) of 9.13%, which outperforms that of the PM7-based all-PSC (PCE = 6.93%). Importantly, the ester modification has significant impact on the thin-film mechanical ductility and robustness. For example, elongation properties of PM7 D1 and PM7 D2 pristine films are significantly improved by ca. 2.5 times compared to that of PM7. The improved ductile properties of PM7 D1 and PM7 D2 also affect the mechanical ductility of the blend films, leading to 1.5-fold increase in crack onset strain compared with that of PM7 blend film.