| 摘要: | 可撓式有機發光二極體(OLED)元件應用時可能會長期承受固定撓曲變形，本研究目的即在探討可撓式OLED封裝薄膜和銦錫氧化物(ITO)導電薄膜在長期受固定應力或應變作用後可能出現的損傷。本研究所採用的材料為一款商用封裝薄膜、一款商用ITO/PEN導電薄膜與一款商用ITO/PET導電薄膜，對於各薄膜材料施予不同曲率半徑之張力或壓力固定撓曲變形量，分別評估固定撓曲變形對於封裝薄膜阻水氣能力的影響以及ITO導電薄膜在固定撓曲變形後的導電性能劣化程度，並比較不同塑膠基板對於ITO撓曲變形影響的差異。
實驗結果顯示，封裝薄膜試片在曲率半徑5 mm以上的壓力彎曲作用1,000小時後，阻水氣滲透能力在40 °C、90% RH恆溫恆濕環境中未明顯改變，而且未發現任何損傷產生於封裝薄膜試片上。封裝薄膜試片於曲率半徑10 mm和5 mm的張力彎曲作用下，在小於100小時的固定撓曲後，試片同樣保持完好，然而在1,000小時後，試片可能產生裂紋導致水氣滲透率上升。而在ITO導電薄膜方面，壓力彎曲對於ITO/PEN導電薄膜和ITO/PET導電薄膜在給定的曲率半徑固定撓曲作用下的影響皆不明顯，然而ITO/PEN導電薄膜在曲率半徑10 mm的張力彎曲作用下以及ITO/PET導電薄膜在曲率半徑5 mm的張力彎曲作用下，ITO表面產生明顯裂紋導致電阻上升。彎曲應力對於ITO/PEN導電薄膜的影響明顯大於對於ITO/PET導電薄膜的影響，主要可歸因於PEN基板與PET基板的硬度及厚度的不同，具有較低硬度和較小厚度的PET基板能夠使ITO薄膜有較好的能力承受固定撓曲變形的作用，產生較小程度的導電性能劣化。
;Flexible organic light emitting diode (OLED) devices may be used under long-term static bending in certain applications. The objective of this study is thus to investigate the effect of long-term static bending on the functional properties of barrier thin film and indium tin oxide (ITO) thin film in flexible OLED. In this study, a commercial barrier film, a commercial ITO/PEN sheet, and a commercial ITO/PET sheet are used. Encapsulation properties of the barrier film and electrical properties of the ITO/PEN and ITO/PET sheets are independently evaluated by conducting static bending tests at various radii of curvature. Moreover, characteristics of ITO thin film fabricated on PEN and PET substrates are also compared to assess the effect of substrate material.
For static bending of the barrier film, experimental results reveal that no significantly detrimental effect to the water vapor transmission rate (WVTR) at 40 °C and 90% RH is found for compressive bending up to 1,000 h and for tensile bending up to 100 h with a radius of curvature of 5 mm or above. However, WVTR of the barrier film is significantly increased and cracks are found in the barrier film when subject to tensile bending of a radius of 10 mm and 5 mm for 1,000 h. For mechanical testing of the ITO thin films under static bending, results indicate that no significant change in electrical resistance of the ITO/PEN and ITO/PET sheets is found for compressive bending after 1,000 h with a curvature radius of 10 mm or above. However, the ITO/PEN and ITO/PET sheets are seriously damaged under a tensile bending of 10-mm radius and 5-mm radius, respectively. The given ITO/PET sheet exhibits a greater resistance to long-term mechanical bending than ITO/PEN sheet in terms of change in electrical conductance, which is attributed to the effect of stiffness and thickness of substrate. As PET substrate has a lower stiffness and thickness than the PEN substrate, ITO thin film in the ITO/PET sheet has a smaller stress given a bending radius. Consequently, a smaller extent of change in the electrical conductance of ITO thin film is found in the ITO/PET sheet, compared to the ITO/PEN sheet. |
