場發射顯示器用高亮度用螢光面板的研究

Abstract

中文摘要 本文是利用網印技術及乙基丁基纖維素(cellulose acetate butyrate)為黏結劑，製作場發射顯示器(FED)用的含鋁膜螢光基板，所使用的螢光粉包括綠色(ZnS:Cu,Au,Al)，紅色(Y2O2S:Eu)，藍色(ZnS:Ag,Cl)，白色(Y2O2S:Tb)等四色螢光粉，其在陽極電壓10 keV時，其效率分別為23.20，2.65，3.68及9.87 lm/w。除此之外，由於使用乙基丁基纖維素為黏結劑，因其本身即具有相當平整的成膜性質，因此在陽極電壓9 keV時，含鋁膜螢光板的亮度是不含鋁膜的兩倍，表示此螢光基板的鋁膜具有鏡面效應(mirror effect)；而所謂的”交連電壓”是定義為含鋁膜及不含鋁膜螢光板亮度曲線的交叉點的電壓，此電壓會隨著鋁膜的厚度增加而增加。而電流密度對螢光基板的亮度和效率之影響明顯地顯示出電流密度在0.1 ~ 140 □A/cm2對亮度有一線性的影響。然而，當電流密度繼續增加時，其效率確有明顯地降低。另一方面，此含鋁膜之螢光基板已成功的裝置在場發射顯示器上，其影像品質及亮度，都有不錯的結果；以CRT為例，傳統家用CRT螢光幕約有300 cd/m2的亮度，而利用本論文所提出的方法，所製作出的螢光板的亮度約有400 cd/m2，比傳統的CRT的亮度更佳。紫外線入射螢光板時，有大部分的紫外線會從個別的顆粒表面反射，而其餘的部分則會激發螢光粉體，使其產生冷發光(photoluminescence)；由於反射的紫外線可散射到細微結構內，因此導致可發光區域，延伸到離表面10層積層顆粒深處。而對於反射及穿透模式(mode)，在經過每層顆粒吸收(absorption)及散射 (scattering)係數的計算之後，可以得到最佳的發光顆粒積層數，此一結果不管從理論計算，或由實驗所得的結果，都具有相當的一致性。 在一個別相關性的研究，我們探討了氧化釔與鋯膠液系統的流變性。多價離子如鑭離子或鎂離子可做為氧化釔顆粒在水溶液中的表面活性離子(surface-active counter ions)，由於這些離子的存在，可以改進氧化釔與鋯膠液漿料系統的穩定性，也可使其固含量增加。而離子的價數及大小會影響漿體的流變行為。使用膠液凝膠(sol-gel)法並加入乾燥速率控制化學物(drying control chemical additive)，可成功地製作出攙鉺棒狀玻璃，其吸收及螢光(fluorescence)光譜，與用化學蒸氣沉積(CVD)法所合成出的樣品之光譜，有相當大的一致性，而其鉺離子所含濃度為500到10000 ppm。在兩步驟水解的過程中，因為N,N-dimethyl formamide (DMF)的加入，可使製作時間大大地減少；這些所製作出棒狀攙鉺玻璃其密度和反射率各為1.65 g/cm3及2.2。

Abstract By using of screen printing method and cellulose acetate butyrate as the binder, the phosphor screens of aluminized ZnS:Cu,Au,Al (green), Y2O2S:Eu (red), ZnS:Ag,Cl (blue) and Y2O2S:Tb (white) with the efficiencies of 23.2, 2.65, 3.68 and 9.87 lm/w, respectively, at 10 keV have been prepared for field emission display (FED). In addition, the screens with Al coating have nearly 2 times the brightness in comparison with pure screens at 9 keV due to the excellent film-forming properties of cellulose acetate butyrate. As the thickness becomes larger, the crossing voltage must be increased to penetrate the aluminum film and hit the phosphor powders. And the effects of current densities on efficiency and brightness of screens were also explored. The linear dependence on brightness was observed with the range of current densities of 0.1 ~ 140 □A/cm2. However, the efficiencies significantly decreased as the current densities increased. On the other hand, the FED panel was successfully made using Al film coated phosphor screen and demonstrated an image of high brightness and relatively good quality which is suitable for practical application. For example, there is 400 cd/m2 in FED panel that was installed by using the method proposed in the thesis, compared to 300 cd/m2 in conventional CRT. In powdered phosphor screens a large fraction of incident UV light reflects from the surface of individual particles, with the remainder penetrating the phosphor surfaces to generate photoluminescence. The reflected UV photons entering the screen are randomly scattered throughout the particulate structure, resulting in photoluminescence down to, for example, 10 layers deep from the surface. An optimum number of layers within a screen for luminance in reflection and transmission modes is calculated after determination of the absorption and scattering coefficients per layer in a practical phosphor screen. Good agreement has been obtained between the calculated and experimental results. On a separate study, the rheological properties of the Y2O3/ZrO2 binder sol system were studied. Multivalent ions such as La3+ and Mg2+ function as surface-active counter ions for Y2O3 particles in aqueous solution. Due to the addition of these electrolytes, the solid content of Y2O3/ZrO2 binder sol slurry was increased and the stability of the slurry was improved. Both ion valence and ion size of electrolytes added into the slurry are expected to influence rheological flow behavior of the slurry. Characterization of erbium-doped silicate produced by sol-gel method with drying control chemical additive has also been carried out. Both of the absorption and fluorescence spectra of these samples were similar to those of erbium-doped optical fibers prepared by modified chemical vapor deposition. The homogeneous monolithic erbium-doped silicate glasses with concentration ranging from 500 to 10000 ppm were constantly fabricated. Due to N,N-dimethyl formamide (DMF) in 2-step hydrolysis procedure, the processing time can be reduced significantly. The index of refraction and specific density of the samples were approximately 1.65 g/cm3 and 2.2, respectively.