Emerging Display Technologies

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Emerging Display Technologies

• Wesley Holland

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Organic Light Emitting Diode (OLED)

• Similarities to conventional LED
• Has anode and cathode
• Electrons flow out through anode and in through
  cathode
• Operates like diode must be forward-biased
• Photons are emitted when electrons fill holes in
  the emissive layer
• Differences from conventional LED
• Emissive and conductive layers are organic
  compounds or polymers
• Substrate can be plastic
• Color displays can be made of triads of RGB OLEDs

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Organic Light Emitting Diode (OLED)

• Advantages
• Can be printed onto a wide variety of substrates
  1
• Can be made using plastic screens LCDs require
  glass backing 3
• Low power requirements
• No backlight required
• No polarization filters necessary no wasted
  light
• Off pixels consume no power
• Faster response time than LCDs 2
• Larger field of view than LCDs up to 170 degrees
  3
• Disadvantages
• Short lifetime (lt1000 hours for blue OLEDs 3)
• Currently, manufacturing is more expensive than
  LCDs
• More susceptible to water damage than LCDs

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Electronic Paper Display (EPD) (a.k.a E-Ink)

• E-ink consists of capsules containing negatively
  charged white plastic suspended in blue or black
  oil
• E-ink is sandwiched between two electrode layers
• When field orients one way, the white particles
  rise to the top. When field orients the other
  way, the oil color is visible
• Color displays can be made by adding color
  filters on top of transparent electrodes and
  organizing pixels in CMY triads

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Electronic Paper Display (EPD) (a.k.a E-Ink)

• Advantages
• Can be printed onto flexible plastic 4
• Extremely large viewing angle (light is
  reflected, not generated)
• Extremely low power requirements
• Power is only consumed while image is switching
• Disadvantages
• Currently, manufacturing is more expensive than
  LCDs
• Slower response time than LCDs 5

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Surface-Conduction Electron-Emitter Display (SED)

• SEDs work on the same principle as CRTs
• One side of a glass is covered in phosphor that
  lights up when hit by electrons
• Electrons are fired at the phosphor to create the
  picture
• However, where CRTs use one electron gun for the
  whole screen, SEDs use an electron emitter for
  each pixel
• A SED is an array of Surface-Conduction
  Electron-Emitters (SCEs), each of which has a
  separate emitter for RGB

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Surface-Conduction Electron-Emitter Display (SED)

• Advantages
• Thin when compared to CRTs approximately the
  same width as LCDs
• Higher contrast ratio and better viewing angle
  than LCDs 6
• Faster response time than LCDs
• Comparable power consumption to LCDs
• Disadvantages
• Phosphor screens are subject to burn-in
• Due to ongoing patent litigation, not currently
  mass-produced

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Plasma Display

• Each pixel is composed of three gas-filled
  capsules (RGB) that operate on the same principle
  fluorescent lights.
• When a voltage is applied across the gas, free
  electrons bombard gas atoms, causing some
  electrons to jump to higher energy levels. When
  they fall back to stable energy level, a photon
  is emitted.
• The Xeon and Neon atoms in plasma screens release
  ultra-violet photons.
• These ultra-violet photons collide with a
  phosphor coating and create visible light.
• An electrode grid is used to turn individual
  pixels on and off.

Glass
Display Electrode
Phosphor-Coated Cells
Address Electrode
Pixel
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Plasma Display

• Advantages
• Thin when compared to CRTs approximately the
  same width as LCDs
• Higher contrast ratio and better viewing angle
  than LCDs 7
• Easy to produce in large sizes
• Disadvantages
• Phosphor cells are subject to burn-in
• High production cost

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Digital Light Processing (DLP)

• The heart of a DLP system is a DLP chip
• Contains many microscopic mirrors (one for each
  pixel)
• Each mirror can be in one of two positions (on or
  off)
• A light source is shined on the DLP chip
• When a mirror is on, light is reflected onto
  the screen, lighting that pixel
• To create color images, light is filtered through
  a color wheel. When the light source is red, red
  mirrors turn on. Likewise for green and blue

DLP Marketing Photo 9
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Digital Light Processing (DLP)

• Advantages
• Thin when compared to CRTs, though not as thin as
  LCDs
• Higher contrast ratio than LCDs8
• Low production costs
• Extremely long lifetime
• No possibility of burn-in
• Disadvantages
• Only one color is displayed at a time if colors
  are not rotated fast enough, this becomes
  noticeable and is called the rainbow effect
• The manner in which light is reflected toward the
  screen results in poor viewing angles when
  compare to other technologies8

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Comparison Summary
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Future Market Share

• OLED
• Will capture the low-power electronics market
  (cell phones and PDAs)
• Will capture emerging market of wearable displays
  and find limited use in electronic billboards due
  to flexibility
• E-Ink
• Will capture E-book market due to extremely low
  power requirements
• Will dominate electronic billboard market due to
  flexibility
• SED
• Will enter production and compete with LCDs in
  all areas
• Plasma
• Will continue to compete with LCDs in the
  medium-sized television market
• Will increase dominance of large-sized television
  market
• DLP
• Will continue to compete in all-sized television
  markets

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References

• 1 D. A. Pardo, G. E. Jabbour, N. Peyghambarian,
  Application of Screen Printing in the Fabrication
  of Organic Light-Emitting Devices, Adv. Mater.
  2000, 12, No. 17, 1249
• 2 Samsung SDI, OLED - Passive Matrix (PM),
  http//www.samsungsdi.com/contents/en/product/oled
  /type01.html , retrieved on July 28 2007
• 3 http//electronics.howstuffworks.com/oled1.htm
  
• 4 Comiskey, B. Albert, J. D. Yoshizawa, H.
  Jacobson, J. "An electrophoretic ink for
  all-printed reflective electronic displays"
  Nature 1998, 394, (6690), 253-255.
• 5 http//www.eink.com/products/matrix/High_Res.h
  tml
• 6 http//entertainment.howstuffworks.com/sed-tv2
  .htm
• 7 http//electronics.howstuffworks.com/plasma-di
  splay1.htm
• 8 http//electronics.howstuffworks.com/dlp1.htm
• 9 http//www.dlp.com/