场发射显示器件制备中的几个关键问题的研究
摘要
场发射显示技术是新兴的平板显示技术之一，它具有CRT的高图像质量，LCD的超薄型以及PDP的大面积等特性，在发光效率、亮度、视角、功耗等方面具备一定优势。本论文综述了场发射研究的历史、现状及发展，常见冷阴极器件的构成和常见冷阴极材料等，结合现有条件，利用硅微尖阵列上生长金刚石薄膜作为阴极材料，采用电泳沉积技术制备阳极,对器件的封装制备进行了实验研究。第一章引言，综述了场发射的研究进程，发展现状和常见的冷阴极材料；第二章阐述场发射的基本原理,阴极材料的选择和阴极结构以及测试系统；第三章讨论了阳极屏的电泳制备法，研究了电解质浓度、荧光粉含量对沉积速率的影响，给出荧光粉与异丙醇的配比、沉积条件；第四章探讨了FED器件封装过程中问题的解决办法:吸气剂的选择、放置位置，隔离柱的使用，将转印电极法引用在FED器件上。解决了引线难和真空问题。
本文章主要工作要点：
1．将转印电极法引用到场发射器件的引线封装，解决了器件的引线问题。采用固定厚度的金属材料压接，可以保持电极接触态良好, 同时起到隔离阴、阳极间距作用；避免了焊接或粘接所带来的缺点，焊接不均匀易短路，粘接胶一般存在不同程度的溢气和易老化现象；简化了FED封装步骤, 使封装引线变得容易。
2．FED器件制作面临的问题，首先，为保证阴阳极间的距离，需要寻找厚度100微米左右的可靠的隔离柱材料；其次是如何在高度仅百微米左右的空间内实现并保持高真空；另外，在器件内外存在很大压力差的情况下，如何保持显示平板不致于变形。
为此，我们采用了锆—钒—铁合金非蒸散性吸气剂。由于内部空间小，吸气剂的选择依赖于管子的类型和制作工艺，我们将吸其剂放置在封接管内，吸气剂激活温度400℃左右，采用反复多次激活的办法；隔离柱保持阴阳极间距并起到缓解分玻璃压力的作用，我们使用直径在110μm左右的玻璃丝；使用的玻璃是产自日本的钠钙质玻璃，基本满足透光性好、平整度高、机械强度张应力大、低热膨胀系数、同时气体渗透性还要差的要求。
3．我们使用的是商用绿色阴极射线粉（）。基本符合在较低的电压驱动下具有较高的发光效率，具有一定的导电性以承受较高的电流密度，必须放气量小且无毒的条件。采用电泳沉积法制备阳极荧光层，其设备简单易实施，涂层平整，分辨率高，制备的荧光层也平整。选择电解液主要是参考材料的介电常数和粘滞系数。沉积后的荧光粉层需在380℃的温度下进行烘烤，并保持一定的真空度，以免在空气中受潮污染。
4.我们给出沉积荧光层厚度对透光强度的影响曲线。场发射显示屏为透射式发光，所以对沉积层的厚度有一定要求，测试实验表明，粉层厚度在15～18μm之间为最佳。但考虑到实际的FED阴极发射的电子能量要比测试系统发射的电子能量小得多，粉层厚度应比测试的最佳范围稍薄一些。从实际经验来看，沉积层厚度在3～15微米比较好。
5．给出沉积条件。沉积速率是影响沉积层质量的关键参数之一，影响沉积速率的几个关键参数：电解质的浓度、荧光粉的含量、沉积电流大小、沉积时间等。实验给出：荧光粉浓度—商用绿色阴极射线粉（）与异丙醇的配比是1～3mg/ml ；沉积条件：沉积前搅拌时间在6小时以上，沉积电压是120～160V,沉积时间是30～90秒。
Field emission display (FED) as a member of flat panel display has been developed recently, since it shows the promising capabilities such as the picture quality as CRT, the appreciated thickness as LCD and the large screen as PDP. FED has advantages on luminescence efficiency, brightness, view angle and power cost. This thesis has firstly reviewed the development background of FED, and discussed the general device structures based on cold-cathead materials. The diamond films are prepared on silicon pin arrays, the field emission mechanisms and properties are discussed, and finally the device assembly processes are performed.
Chapter 1 has reviewed the development of FED technology. Chapter 2 has discussed the physical model of field emission. Chapter 3 has prepared the anode with electrophoresis, and the influence of solution concentration and fluorence powder contents on the deposition process has been studied. Chapter 4 has investigated the fabrication process of FED devices, employing the transfer-printing of electrode, and the lead-out of electrodes and vacuum keeping are discussed.
Main researches of this study are as follows:
It can solve the problem of lead-in wire to apply electrode transfer method in the lead-in wire packaging of field emission devices. Adopting metal pressure welding at fixed thickness can ensure the good contact state for electrodes and insulation between cathode and anode. Besides, this process can avoid failures caused by welding and cementation, i.e., direct short caused by unevenly welding; aging caused by gelatins, etc. In addition, this process can realize the simplification in FED packaging and make the lead-in wires to be available and pleasing to see.
Problems exist in FED device preparation. First, it is necessary to seek for the insulation materials with stable structure and thickness of only scores ofμm. Second is how to realize and retain the high vacuum in the space of only a small number of μm. Last but not the least, how to keep the display panel not to deform in the occasion of pressure differences between the inside and outside of the device.
Degasser selection depends on the pipe type and the preparation process due to the narrow inner space of FED. We choose the non-evaporating alloy degasser of Zirconium-Vanadium-Fe with the activation temperature around 400℃. The insulation pole can keep the range interval between cathode and anode and release the pressure of glass. The fiberglass that we use is round 110μm with high light transmittance, high planeness, strong tensile stress, low coefficient of thermal expansion and permeability. The fiberglass that we use belongs to the soda-lime glass series originated in Japan. Basically, it can fulfill the requirement of this study.
3. Phosphor powder and cathode are two major obstacles affecting the merchandising plan of FED. The phosphor materials used in FED must possess higher luminous efficiency in lower electric voltage. Besides, the materials must possess a certain conductibility to bear higher density of electric current. Additionally, the materials must possess non-toxicity and low deflating volume and the florescent layer to be prepared must be smooth.
Cataphoresis is adopted to prepare the anode displays. The equipments required in this study are easy to control based on smooth coating and high resolution. The electrolyte is selected with references of dielectric constant and coefficient of viscous of
the materials. The depositional phosphor powers are required to be baked at 380℃ with a certain degree of vacuum to avoid moistures in the air.
The transmitting luminescence of FED possesses a certain requirement for the thickness of sedimentary deposit. The test result indicates that it is the optimal state to maintain the thickness of the power layer to be within 15-18μm. While, the actual energy of electron emitted by the cathode of FED is far less than that of the testing system. Thus, thickness of the powder layer should be thinner than that of the range in the test.
本文章主要工作要点：
1．将转印电极法引用到场发射器件的引线封装，解决了器件的引线问题。采用固定厚度的金属材料压接，可以保持电极接触态良好, 同时起到隔离阴、阳极间距作用；避免了焊接或粘接所带来的缺点，焊接不均匀易短路，粘接胶一般存在不同程度的溢气和易老化现象；简化了FED封装步骤, 使封装引线变得容易。
2．FED器件制作面临的问题，首先，为保证阴阳极间的距离，需要寻找厚度100微米左右的可靠的隔离柱材料；其次是如何在高度仅百微米左右的空间内实现并保持高真空；另外，在器件内外存在很大压力差的情况下，如何保持显示平板不致于变形。
为此，我们采用了锆—钒—铁合金非蒸散性吸气剂。由于内部空间小，吸气剂的选择依赖于管子的类型和制作工艺，我们将吸其剂放置在封接管内，吸气剂激活温度400℃左右，采用反复多次激活的办法；隔离柱保持阴阳极间距并起到缓解分玻璃压力的作用，我们使用直径在110μm左右的玻璃丝；使用的玻璃是产自日本的钠钙质玻璃，基本满足透光性好、平整度高、机械强度张应力大、低热膨胀系数、同时气体渗透性还要差的要求。
3．我们使用的是商用绿色阴极射线粉（）。基本符合在较低的电压驱动下具有较高的发光效率，具有一定的导电性以承受较高的电流密度，必须放气量小且无毒的条件。采用电泳沉积法制备阳极荧光层，其设备简单易实施，涂层平整，分辨率高，制备的荧光层也平整。选择电解液主要是参考材料的介电常数和粘滞系数。沉积后的荧光粉层需在380℃的温度下进行烘烤，并保持一定的真空度，以免在空气中受潮污染。
4.我们给出沉积荧光层厚度对透光强度的影响曲线。场发射显示屏为透射式发光，所以对沉积层的厚度有一定要求，测试实验表明，粉层厚度在15～18μm之间为最佳。但考虑到实际的FED阴极发射的电子能量要比测试系统发射的电子能量小得多，粉层厚度应比测试的最佳范围稍薄一些。从实际经验来看，沉积层厚度在3～15微米比较好。
5．给出沉积条件。沉积速率是影响沉积层质量的关键参数之一，影响沉积速率的几个关键参数：电解质的浓度、荧光粉的含量、沉积电流大小、沉积时间等。实验给出：荧光粉浓度—商用绿色阴极射线粉（）与异丙醇的配比是1～3mg/ml ；沉积条件：沉积前搅拌时间在6小时以上，沉积电压是120～160V,沉积时间是30～90秒。
Field emission display (FED) as a member of flat panel display has been developed recently, since it shows the promising capabilities such as the picture quality as CRT, the appreciated thickness as LCD and the large screen as PDP. FED has advantages on luminescence efficiency, brightness, view angle and power cost. This thesis has firstly reviewed the development background of FED, and discussed the general device structures based on cold-cathead materials. The diamond films are prepared on silicon pin arrays, the field emission mechanisms and properties are discussed, and finally the device assembly processes are performed.
Chapter 1 has reviewed the development of FED technology. Chapter 2 has discussed the physical model of field emission. Chapter 3 has prepared the anode with electrophoresis, and the influence of solution concentration and fluorence powder contents on the deposition process has been studied. Chapter 4 has investigated the fabrication process of FED devices, employing the transfer-printing of electrode, and the lead-out of electrodes and vacuum keeping are discussed.
Main researches of this study are as follows:
It can solve the problem of lead-in wire to apply electrode transfer method in the lead-in wire packaging of field emission devices. Adopting metal pressure welding at fixed thickness can ensure the good contact state for electrodes and insulation between cathode and anode. Besides, this process can avoid failures caused by welding and cementation, i.e., direct short caused by unevenly welding; aging caused by gelatins, etc. In addition, this process can realize the simplification in FED packaging and make the lead-in wires to be available and pleasing to see.
Problems exist in FED device preparation. First, it is necessary to seek for the insulation materials with stable structure and thickness of only scores ofμm. Second is how to realize and retain the high vacuum in the space of only a small number of μm. Last but not the least, how to keep the display panel not to deform in the occasion of pressure differences between the inside and outside of the device.
Degasser selection depends on the pipe type and the preparation process due to the narrow inner space of FED. We choose the non-evaporating alloy degasser of Zirconium-Vanadium-Fe with the activation temperature around 400℃. The insulation pole can keep the range interval between cathode and anode and release the pressure of glass. The fiberglass that we use is round 110μm with high light transmittance, high planeness, strong tensile stress, low coefficient of thermal expansion and permeability. The fiberglass that we use belongs to the soda-lime glass series originated in Japan. Basically, it can fulfill the requirement of this study.
3. Phosphor powder and cathode are two major obstacles affecting the merchandising plan of FED. The phosphor materials used in FED must possess higher luminous efficiency in lower electric voltage. Besides, the materials must possess a certain conductibility to bear higher density of electric current. Additionally, the materials must possess non-toxicity and low deflating volume and the florescent layer to be prepared must be smooth.
Cataphoresis is adopted to prepare the anode displays. The equipments required in this study are easy to control based on smooth coating and high resolution. The electrolyte is selected with references of dielectric constant and coefficient of viscous of
the materials. The depositional phosphor powers are required to be baked at 380℃ with a certain degree of vacuum to avoid moistures in the air.
The transmitting luminescence of FED possesses a certain requirement for the thickness of sedimentary deposit. The test result indicates that it is the optimal state to maintain the thickness of the power layer to be within 15-18μm. While, the actual energy of electron emitted by the cathode of FED is far less than that of the testing system. Thus, thickness of the powder layer should be thinner than that of the range in the test.
引文
[01] R.H.Forler,L.W.Nordheim,Proc.R.Soc.VolA119(1928),173
[02] C.A.Spint,J.Appl.Phys.Vol39,(1968),3504
[03] C.Wang,A.Garcia,D.C.Ingram,M.Lake,Electron.Lett.
27(1991),1459
[04]“场致发射显示器的现状与发展”，《国际光电显示技术》，2003年1月，pp134
[05]王维彪，中科院长春光机所博士论文，1999，pp9
[06]Gung Joon Chi,Technical Digest of 9th IVMC,pp245(1996),
St.Petersbug,RUSSIA
[07]In-Han Chung et al.,Technical Digest of 9th IVMC, pp245(1996)
St.Petersbug,RUSSIA
[08]T.Xie,J.Vac.Sci.Technol.B14(3),pp2090(1996)
[09]M.Endo,J.Vac.Sci.Technol.B14(3),pp2144(1996)
[10]B.C.Djubua,IEEE Trans.ED38(10),pp2314(1991)
[11]E.Yamaguchi,K.Sakai,I.Nomura,J.of The SID5/4,pp345(1997)
[02] C.A.Spint,J.Appl.Phys.Vol39,(1968),3504
[03] C.Wang,A.Garcia,D.C.Ingram,M.Lake,Electron.Lett.
27(1991),1459
[04]“场致发射显示器的现状与发展”，《国际光电显示技术》，2003年1月，pp134
[05]王维彪，中科院长春光机所博士论文，1999，pp9
[06]Gung Joon Chi,Technical Digest of 9th IVMC,pp245(1996),
St.Petersbug,RUSSIA
[07]In-Han Chung et al.,Technical Digest of 9th IVMC, pp245(1996)
St.Petersbug,RUSSIA
[08]T.Xie,J.Vac.Sci.Technol.B14(3),pp2090(1996)
[09]M.Endo,J.Vac.Sci.Technol.B14(3),pp2144(1996)
[10]B.C.Djubua,IEEE Trans.ED38(10),pp2314(1991)
[11]E.Yamaguchi,K.Sakai,I.Nomura,J.of The SID5/4,pp345(1997)