A field emission display (FED) has the advantages of wide viewing angle, quick response speed, high luminescence efficiency, etc., and has long been considered as highly important in the development of flat TV. Unlike the liquid crystal display (LCD) that requires a backlight panel, the FED is a self-emission display and has an operational mechanism similar to that of a cathode-ray tube (CRT) display. The FED advantageously combines the slim and planar structure of the LCD display with the good picture quality of the CRT display. The field emission display (FED) is superior to the conventional LCD in many aspects, including the brightness, response speed, viewing angle, etc. Generally speaking, the FED is very suitable for use as a display. However, the conventional field emission display is hindered from being commercialized within a short time by several tough problems in the manufacturing process thereof.
FIG. 1 is a conceptual diagram of a conventional vertical type field emission device, which includes a cathode 20 having a field emitter 21, on which a carbon nano material is grown or an array of spindles is formed; an anode 10 that is an indium tin oxide (ITO) glass coated with a layer of fluorescent powder 11, and a gate 22 provided close to a top of the cathode 20. Due to a high electric field between the cathode 20 and the anode 10, field-emission electrons are emitted from the field emitter 21 of the cathode 20 in a vacuum space to impact the fluorescent powder 11 on the anode 10 for the fluorescent powder 11 to produce light. The gate 22 is connected to a relatively small positive electricity, so as to attract the cathode to increase the electron emissivity.
The above-described conventional vertical type field emission device is prevented from commercializing due to the following disadvantages: (1) It requires a spacer 12 to control a vertical distance between the cathode 20 and the anode 10; (2) since the allowable tolerance for the vertical type FED is very small, considerations in structural design and good yield must be taken when the vertical FED is applied to a large-area display; moreover, it is also very difficult to control the evenness of an overall brightness when the vertical FED is applied to a large-area display; (3) the electric current amount of the field-emission electron beam is very sensitive to the distance between the gate 22 and the cathode 20, and would have direct influences on the luminescent intensity of individual pixels; and since the distance between the gate 22 and the cathode 20 is very small that is measured in μm, it is very difficult to obtain uniform brightness for all pixels in the manufacturing process; moreover, the emitted electron beams tend to be out-of-focus and result in low contrast of pixels; (4) in the event the carbon nano material is not evenly grown on the field emitter 21 at the cathode 20, there would be some areas on the cathode 20 that do not have emitted electrons, resulting in dark spots on the fluorescent powder 11; (5) since the light from the fluorescent powder 11 would be blocked by the anode 10, the anode 10 must be an expensive light-transmittable conducting glass made of indium tin oxide; and (6) the gate 22 also requires additional manufacturing cost.