摘要:
采用电晕注极和热注极技术，在厚度为25μm的氟化乙丙烯共聚物(FEP)表面制备了宽度为2 mm和3 mm的具有栅型电场分布的驻极体，研究了注极温度和电极宽度对其电荷存储性能的影响。样品注极后经150天的存储，栅型电场分布变得清晰而有规律，覆盖铝电极区电位已衰减至接近零，未覆盖铝电极区仍保持高电位；对电极宽度为2 mm和3 mm的样品，覆盖铝电极区与未覆盖铝电极区的表面电位差分别为110 V和130 V(电场强度差分别为44 kV/cm和52 kV/cm)。表面电位跟踪测试结果表明：电晕注极样品初始表面电位高于热注极样品；在相同的注极方法下，注极温度越高初始表面电位越高，电极宽度越小初始表面电位越低。依据电晕注极和热注极原理对实验结果的分析表明， FEP和金属铝在电荷存储性能上的差异是FEP表面蒸镀铝电极后能获得栅型电场分布的原因所在。
Abstract:
Electret has caught wide attention because it can produce a lasting and stable electrostatic field in the application of MEMS devices such as miniwatt electret generator, electret motor, electret sensor, electret transducer, and so on. Of all the above applications, a remarkable feature is that the electrostatic field distribution on electret surface is patterned in millimeter size or even smaller. However, the charge storage performance of electret in miniature size will dramatically get worse in contrast with the macro-electret. Therefore, it is very important to develop an applicable preparing method to maintain the stability of electrostatic field distribution in micro-patterned electret. In this paper, it is reported that a fluorinated ethylene propylene copolymer (FEP) with evaporated aluminum grid electrode a 25 μm thickness topped with at a step of 2 or 3 millimeter are successfully prepared to form the electret with well grid distribution of electric field(abbreviated as grid electret) by means of corona charging and thermal charging technology. Effect of grid width and charging temperature on the charge storage performance is studied. After stored for 150 days, the grid distribution of electric field on the FEP surface becomes clear and organized. The potentials of the area covered by aluminum electrode are close to zero, while that of uncovered area still remain high. The potential differences between the covered and uncovered by aluminum electrode area are identical in different charging methods, it is 110 V (electric field 44 kV/cm) for the sample with an electrode width of 2 mm, and 130 V (electric field 52 kV/cm) for the sample with an electrode width of 3 mm. Results also show that the initial surface potentials of the grid electrets prepared by corona charging is higher than that by thermal charging, but the former decays more rapidly. For the same charging method, the narrower the aluminum electrode area can lead to the lower initial surface potential, and the higher charging temperature causes the larger initial surface potential. According to the principle of corona charging and thermal charging technology it is concluded that the difference of charge storage capability between FEP and aluminum can account for the grid distribution of electric field on the FEP surface.
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