Published on March 2, 2014
Surface Conduction Electron Emitter Display (SED)
INTRODUCTION The SED technology has been developing since 1987. The flat panel display technology that employs surface conduction electron emitters for every individual display pixel can be referred to as The Surface-conduction Electron-emitter Display (SED). Though the technology differs, the basic theory that the emitted electrons can excite a phosphor coating on the display panel seems to be the bottom line for both the SED display technology and the traditional cathode ray tube (CRT) Televisions.
Current display technologies CRT Highest image quality. Costlier than most others. LCD Motion blur. Low power consumption. PLASMA Grey levels are high. High power consumption.
Manufacture of SED TV SED is a display device includes an electronemitting device which is a laminate of an insulating layer and a pair of opposing electrodes formed on a planar substrate. 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.
WORKING CREATING THE PICTURE Electrons are emitted from the electron emission region by applying a voltage to the electrodes, thereby stimulating a phosphorous to emit light . It's a flat-panel television that uses millions of miniature CRTs are called Surface Conducting Electron emitters (SCEs). A set has three SCEs for every pixel -- one each for Red, Green and Blue.
A widescreen, high-definition set can have more than 6 million SCEs. An SED-TV has millions of these SCEs arranged in a matrix, and each one controls the Red, Green or Blue aspect of one pixel of the picture. The inside of an SED-TV is a vacuum. All of the SCEs are on one side of the vacuum, and the phosphor- coated screen is on the other. The screen has a positive electrical charge, so it attracts the electrons from the SCEs.
When bombarded by moderate voltages (tens of volts), the electrons tunnel across a thin slit in the surface conduction electron emitter apparatus. Some of these electrons are then scattered at the receiving pole and are accelerated towards the display surface. These emitted electrons can then excite the phosphor coating on the display panel. When they reach the screen, the electrons pass through a very thin layer of aluminum. They hit the phosphors, which then emit red, green or blue light.
Our eyes and brain combine these glowing dots to create a picture. Any part of the screen that's not used to create pixels is black, which gives the picture better contrast. There's also a color filter between the phosphors and the glass to improve color accuracy and cut down on reflected light.
To tie it all together, when the SED-TV receives a signal, it: Decodes the signal Decides what to do with the red, green and blue aspect of each pixel Activates the necessary SCEs, which generate electrons that fly through the vacuum to the screen. The set can create a picture sixty times per second. It creates the entire picture every time unlike CRT.
FABRICATION OF NANO GAPS Nanogaps are the electron guns of SED.A nanometer scale gap (nanogap) structure in palladium strip fabricated by hydrogen absorption under high-pressure treatment. It is found that the edge roughness of the nanogap improves the electron emission characteristics. The electron emission current is dependent upon the angle of inclination of surface.
Hydrogen plasma treatment is used to increase the edge roughness of the nanogap and thereby dramatically improve the electron emission characteristics. For the nanogap with a separation of 90 nm, the turn-on voltage significantly reduces from 60 to 20 V after the hydrogen plasma treatment.
Electrons are supplied to the anode in 2 steps Step 1: The electron source operates by first emitting electrons laterally across a very narrow gap formed between two electrodes. The electrons tunnel through the vaccum gap from one electrode to the other electrode.
Step 2: The electrons that tunnel across the gap and strike the counter-electrode are either absorbed into the counter electrode or they are scattered, captured by the electric field created by the anode potential and accelerated to a particular phosphor dot, thus creating a spot of red, green or blue light. Multiple scattering events may take place before the electron is captured by the anode field.
SED TV Compared to CRT CRT They are as deep as they are wide and they are heavy too. Have image challenges around the far edges of the picture tube. SED They’re slim and light weight. CRTs can be made as large as the manufacturer dares.
SED TV Compared to Plasma TV Plasma TV SED Grey levels in plasma TVs are high. The black is actually dark grey. Consumes more power. Perfect black. Suffers from black level issues and solarization. SEDs consumes half the power that the plasma does at the given screen size. SEDs don’t have such issues.
SED TV Compared to LCD LCD LCD suffers from motion blur. It has limited angle of view and tends to become too dim to view off axis. Outdoor scenes in bright light block up blacks and bleach out whites. Suffers from black level issues and solarization. SED There is no motion blur in SED. This will not be an issue for SED’s self illuminated phosphors. SED shows the peak brightness. SEDs don’t have such issues.
ADVANTAGES Slim Superior contrast ratios Exceptional response time Better picture quality More brightness Color performance Viewing angles Consumes very less power.
FEATURES Contrast ratio 100,000:1. Response time 0.2 milliseconds. Brightness of 450 cd/m2. 180º Viewing angle. Viewable in Bright room. It can be used in Mobile device display. Low power consumption. Longer life expectancy.
CONCLUSION SED will be the next generation display technology in the near by future though patent controversy and the lack of cheaper manufacturing techniques are slowing down the commercial viability of SED TV.
REFERENCE www.canon.com www.thoshiba.com www.electronics.howstuffworks.com www.howstuffworks.com www.wikipedia.com www.patentstorm.us www.freepatentsonline.com www.googlepatents.com
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