場發射平面顯示器真空隔板新材料開發與電特性分析

Abstract

場發射平面顯示器需要在高真空下操作，才能延長電子場發射的壽命。所以需要真空隔板在場發射源與螢光板之間，用來承受大氣壓力。真空隔板是由絕緣材料所組成，使得陰極板和螢光板不受電而導通。然而，場發射源從陰極發射至螢光板，背向散射電子可能轟擊絕緣真空隔板造成二次電子的產生。因為大部份材料的二次電子產生率都大於1，使得隔板產生二次電子，而形成正電荷，會改變真空隔板與附近發射源之間的電場分怖，因此改變了電子的入射軌跡，造成影像失真。 為了降低這二次電子產生不利的影響，我們在玻璃基板上製備出多孔性陽極氧化鋁和多孔性二氧化鈦薄膜塗層，用來減少隔板二次電子產生。因為二次電子能量低且其逃脫深度較淺，孔洞的結構可以抓住二次電子使其不易逃脫，所以二次電子產生率有明顯著的降低。 我們研究上述兩種隔板的二次電子產生率，藉由一個特殊設計樣品放置於歐傑電子能譜儀上。也對於上述兩種塗層進行表面粗糙度、附著力強度和電阻的研究。進而發現多孔性塗層表現出良好的電性和機械性質，適合用來當作場發射平面顯示器真空隔板。我們已經成功地製備出大表面積為 24 x 60 mm2 的均一多孔性陽極氧化鋁和多孔性二氧化鈦薄膜塗層。

Field-emission flat panel displays (FE-FPD) require a high-vacuum operation condition to optimize the life-time of electron field-emitters; this requirement needs vacuum spacers to be placed between the cathode plate comprising field-emitters and the screen plate to withstand the atmospheric pressure. Vacuum spacers are made of insulators so that the cathode and the screen plates are free from electrical breakdown. However, as the field-emitted electrons from the cathode strike the screen plate, backscattered electrons may impinge on the insulating spacers resulting in secondary electron (SE) emission from the spacers. Because the SE yield is larger than one for most materials, the SE emission will render the spacers positively charged, thereby modifying the local electric field; the modification can change the trajectory of the field-emitted electrons resulting in image distortion. To overcome the adverse effect of the SE emission, we fabricated porous coatings anodic aluminum oxide (AAO) and porous TiO2 thin films on glass to minimize the SE yield of the spacer. Because the porous structure can trap secondary electrons, which have a low kinetic energy and a very shallow escape depth, the SE yield can be significantly reduced. We studied the relative SE yield of the two types of spacers in an Auger electron spectrometer using a specially designed sample holder. The surface roughness, the adhesion strength and the electrical resistance of the coatings were also studied. The porous coatings demonstrated good electrical and mechanical properties, which are suitable for the use of vacuum spacers in FE-FPDs。We have successfully fabricated uniform porous AAO and porous TiO2 coatings on the large substrate with a surface area of 24 x 60 mm2.