OLED-TV|Laser-TV|SED|Display|FED|

Structure of SED-TV FED-TV
Structure—Electron acceleration requires a vacuum to avoid corona or plasma discharge. Thus, the mechanical structure of the SED and other FEDs consists of a hermetically sealed glass envelope that is evacuated to form the vacuum space required to accelerate the electron beams. Depending on the size of the display and thickness of the glass walls, spacers are generally required in order to support the glass walls against the atmospheric pressure. The spacers must also be able to stand off high voltage gradients and be optically invisible to viewers under normal operating conditions. The 36-inch SED required 20 rib-type spacers to maintain the 1.7mm vacuum
gap. A schematic of the SED display is shown in Figure . FED
displays have been demonstrated with both rib-type and post-type spacers. Furthermore, all FED technologies —including SED—require a form of getter technology to maintain the required vacuum inside the glass envelope after the display is evacuated and sealed.

Manufacturing process SED-TV FED-TV
Manufacturing—Their fabrication and assembly approaches are also very similar except for the cathode plate, which will be described later. All FED approaches being developed today require assembling a face-plate (anode) with a back-plate (cathode or electron source), together with sidewalls, spacers and getters. First, the anode and cathode plates are fabricated
separately, assembled with the other components, sealed
using glass frit or other novel materials and then evacuated.
Figure 2 diagrams the assembly process for a CNT-based FED,
but can be applied to other FED technologies, including SED. In
some approaches, the sealing and evacuation steps are combined, and still other approaches hope to eliminate or reduce the number of spacers. New materials are under development to replace frit-glass seals in order to lower the sealing temperature and to avoid materials with high lead content.

The anode fabrication process is very similar for both SED and
FED. Figure 3 shows the details of the anode configuration for an
SED panel. The black matrix and color filters are used to improve
contrast. The metal back film is used to improve brightness and
efficiency, and also acts as an electrode for the high voltage
potential and bleeds charge away from the phosphor during
e-beam illumination. These are standard technical modifications
used in CRT, FED and high-voltage vacuum fluorescent display
to improve the performance of the phosphor.
Finally, both SED and CNTbased FED displays have used
printing to fabricate the anode and cathode plate, as will be
detailed in the following section.
Thus depending on your point of view, the SED and other FED
technologies have many components in common, such as the
anode and phosphors used on the anode, spacer technology,
getters and much of the assembly process. Now let’s look at what
is unique to SED and other FED technologies.

Technology distinctions
The significant differences between SED and FED are clearly
seen in the electron source plate and the drive electronics. Before
we discuss the significance of the differences, we must first understand how each is structured and operated.
Standard FED emitter configurations

—Some typical configurations
using CNT emitters are
shown in Figure 4.

Microtip emitters have similar configurations
as CNT. In either case, electron beams are created by extracting
electrons from the emitter structure (CNT or microtip) as a result
of the high electric fields applied to the emitter from voltage differences between the anode, gate and cathode electrodes. In some cases, the anode field contributes to the electron emission, but the cathode-gate voltage difference controls the emission current intensity.Electron current from the FED emitters is controlled by the field applied to the emitter as a result of the cathode to gate bias and is governed by the Fowler-Nordheim equation. The current from the emitter as a function of the applied voltage is highly nonlinear. An example of the I-V characteristics for a CNT emitter is shown in Figure 5. In addition to the applied field, the emission
current is also dependent on the workfunction () of the emitter and the shape of the emitter. As the workfunction is decreased such as with a coating of alkali metal it is easier to extract electrons at lower fields. As the shape of the emitter becomes sharper, it is also easier to extract electrons since the local electric field is higher at the point of the emitter. There are two important points to make concerning the standard FED approaches. Firstly, the configuration is largely vertical.
Typically, the gate is placed near the cathode electrode, such
that the applied electric field is mostly vertical at the cathode
electrode where the CNT emitter is deposited. The electrons that
are emitted from the cathode travel directly to the anode. Some
broadening of the beam takes place as a result of the lateral
components of the applied field, but these are limited as much
as possible by the design or are corrected with additional focus
electrodes placed in the path as needed.

Figure1: The structure of FED (b) is similar with the structure of SED (a) except for the details of the cathode plate

Figure 3: The anode fabrication process is very similar for both SED and FED.
SED-TV FED-TV Technical details PART ONE
Structure and manufacturing process of SED and FED-TV
By Richard Fink
VP of Engineering
E-mail: dfink@appliednanotech.net
Applied Nanotech Inc.