The Role of Hop and Flue Plates in Flat Panel Displays

Field emission displays (FED) are based on a large array of individually switched electron sources. A major problem in such displays is intra-pixel uniformity. In particular, the eye is very sensitive to variations in spot shape even if pixel intensities are uniform. A second problem lies in visually unacceptable charging artifacts from the spacers, required to support the vacuum envelope. Incorporating hop and flue plates into the FED structure effectively removes these problems and has other advantages, such as improving colour purity. The glass hop plate (~0.4mm thick) has an array of conical holes; one for each sub-pixel. The electrons are channeled through the holes in a chaotic manner, resulting from secondary emission and surface charging, producing a virtual source of electrons that is independent of the shape of the original source. The electrons then pass into the inverted flue plate cones and are accelerated towards the anode. Spacing nibs on one plate leave a pumping space between the two plates. A non-evaporable getter layer between the plates can provide pumping after sealing. The dimensions and coating of the holes in the hop plate are optimized for providing a uniform virtual source, while those of the flue plate have to provide maximum voltage hold off to allow as high an anode voltage as possible