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为了防止萤光粉因离子灼伤而出现暗斑,目前各种磁偏转显像管萤光屏的内壁大多用真空蒸发的方法敷上一层薄而密致的铝膜。这层铝膜除能有效地防止离子灼伤外,还能够改善图像反差和克服“粘着电位”所产生的高电压亮度限制。然而电子在通过铝膜时,要损失一部分能量,因此也伴随着降低亮度的效应,如图1所示。由此可见,过薄的铝膜不能有效地克服离子灼伤,过厚的铝膜则使电子束的能量损失太大,影响亮度,因此对
In order to prevent the fluorescent powder from being burned by ions, dark spots appear. At present, most of the inner walls of various magnetic deflection tube fluorescent tubes are coated with a thin and dense aluminum film by the method of vacuum evaporation. This layer of aluminum film can not only effectively prevent ion burns, but also improve image contrast and overcome the high voltage brightness limit caused by “sticking potential”. However, when electrons pass through the aluminum film, a part of the energy is lost, so the effect of reducing the brightness is also accompanied by the phenomenon shown in FIG. 1. Thus, too thin aluminum film can not effectively overcome ion burn, too thick aluminum film is the energy loss of the electron beam is too large, affecting the brightness, so the