藉由數位影像分析量測軟性基板彎曲應變

Abstract

軟性高分子基板為近年來新興科技的發展重心之一，其中最廣泛的應用為下一世代顯示器發展的主力「軟性顯示器」。由於軟性顯示器有著既輕且薄、可撓曲、耐衝擊具安全性等特性，以及能結合日常生活中的報紙、圖書，發展成電子紙和電子書，儼然成為下一世代具有代表性的顯示器。基於可彎曲性是軟性顯示器的最大特徵，因此如何量測構成軟性顯示器的軟性高分子基板，在彎曲時的應變值與應變分佈，為選用軟性顯示器構成材料時所使用的重要技術之一。有鑑於傳統的接觸量測不適用於大變形量測，因此發展非接觸式量測為首要的選擇。由於現今的非接觸式量測技術大多數須架設複雜的光路結構，且對於量測環境有嚴苛的要求，本文以發展不易受環境光源影響，且不須架設複雜量測設備的非接觸式測量為研究主軸。以雙CCD 鏡頭擷取影像，建構出電腦立體視覺系統，以此系統拍攝軟性高分子基板在受彎曲時，變形前與變形後的影像，再根據數位影像關聯法(Digital Image Correlation, DIC)，比對出材料表面任一點在變形前後移動的位移向量，藉由位移向量計算材料的變形梯度，以此獲得軟性高分子基板在受彎曲時的應變值。經由PEN高分子基板的彎曲實驗結果，發現所量測試片中心處的應變，確實如預期，隨著曲率的增大，應變也會跟著增加。

Flexible electronic is important development in modern technology. One of the most widespread applications is “flexible display”, which is mainly developed for the next generation monitor. Flexible display is thin and flexible, shock-resistant, and can serve in daily life as electronic paper and electronic books. Flexibility is one of major characteristics for flexible display. Therefore, how to measure the strain field of bending for flexible polymer substrate that constitute the flexible display is an important technique. In view of the fact that traditional devices such as strain gages and photoelasticity are not suitable for measure large deformation, this study develops noncontact measurement as the first choice. As a result of today's noncontact measurement technology is set up by complex structure of the optical path, and the environment of measurement is demanding. This study develops an imaging method less susceptible of light effect on the environment, rather than sets up complex devices of noncontact measurement. Using two CCD cameras constructs a three-dimensional computer vision system, which captures images of the sample before and after deformation in the bending test. Based on the digital image correlation, this study compares the displacement vector of any point on the display surface when deformation occurs. The deformation gradient of materials is calculated by the displacement vector, and we can obtain the strains of the bending test for flexible electronic. According to the bending test result of PEN substrate, the strain at the center of sample surface indeed increases with curvature increase.