Flexible electronic displays
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  • 1. M. S. Ramaiah Institute of Technology 1Flexible Electronic DisplaysSindhu AUSN No:1MS09TE054B.E- Telecommunication EnggGuide :Mrs Parimala PAsst. ProfessorMSRIT, Bangalore
  • 2. AcknowledgementsI express immense gratitude towards the Head ofthe Department of Telecommunication Engineering,Dr K Natarajan for continued support.I would also like to thank, Mrs. Parimala P,Mr.Venu K N and Mr.Satish Tunga for their appropriateguidance.2M. S. Ramaiah Institute of Technology,
  • 3. Aim of the Project• To understand the various flexibleelectronic display technologies.M. S. Ramaiah Institute of Technology 3
  • 4. Outline• Introduction and Scope• What makes flexible electronic displays attractive ?• Based on Reflectivity or Emissivity• Properties• Different types of display technologies• Flexible electronic displays have two plans• Flexible Electronic displays based on Reflectivity-Gyricon• Electrophoretic Ink• Self-Emissive based flexible displays -->FOLED• How OLED technology works?• Small molecule OLED vs Polymer OLED• OLED ACTIVE AND PASSIVE DISPLAYS• Advantages and Disadvantages FOLED• Wide variety of applications..• Challenges and Conclusion• References M. S. Ramaiah Institute of Technology 4
  • 5. Introduction• A flexible display is a display which is flexible in nature;differentiable from the more prevalent traditional flatscreen displays used in most electronics devices.• It Enables a New Intuitive User Interface,suitable for simple operations in application software andopens up new possibilities for flexible displays to be used asuser-interface devices.Scope• Offers a more natural way to interact with our gadgets.M. S. Ramaiah Institute of Technology 5
  • 6. What makes flexible electronic displaysattractive ?• Rugged• light weight• unconventional form factors• very thin• non-brittle• the ability to curve, flex, conform, roll,and fold• portability• Low power M. S. Ramaiah Institute of Technology 6
  • 7. Based on either– Reflectivity or Emissivitythere are 2 forms of displaysFlexible E-Paper based displays andFlexible OLED based displaysAs Both of these technologies work on different principles,they exhibit different properties and various different types of displaytechnologies.M. S. Ramaiah Institute of Technology 7
  • 8. Properties• Similarities• DifferencesM. S. Ramaiah Institute of Technology 8Reflective based—E-Paper Technology Emissive based–Flexible OLED TechnologyComfortable to Eyes, as screens reflect lightlike real paper.They emit lightThis relies on reflected ambient light(can beread in direct sunlight without the imagesappearing to fade)Each individual light generating pixelgenerates light when an electric charge isappliedHolds static image and text indefinitelywithout using electricityBoth forms can show images while being bent withoutsuffering from distortion or blank spotsBoth the technologies do not rely on back light
  • 9. • Based on Reflectivity– Flexible Electronic Paper based• Gyricon• Electrophoretic• Cholesteric based bi-stable display• Electrowetting• Electrochromic• Self-Emissivity Based– Flexible OLED (Organic Light Emitting Diode)basedM. S. Ramaiah Institute of Technology 9Different types of display technologies
  • 10. The flexible electronic displays have two plans The back plane – It is made up of organic thin film transistor arrayswhich provide voltage needed by the, E-Paper or the FOLED (FlexibleOrganic Light Emitting Diode) based front plane. The front plane – It is the part where visible images will be displayed.Back Plane constructionFlexible Printed Organic back planesM. S. Ramaiah Institute of Technology 10A piece ofFlexiblePlasticSubstrateCoatedwithOTFTmaterialTo produceBackplaneand a displaythat can behandled like apaper
  • 11. Flexible Electronic displays based onReflectivity-- Gyricon Nicholas K. Sheridon invented Gyricon atXerox Palo Alto Research Center (Xerox PARC),In the 1970s A new display technology eventually became the basis of the e-paper. designed to mimic the appearance of ordinary ink onpaper, as they reflect light. Theoretically making it more comfortable to read,and giving the surface a wider viewing anglecompared to conventional displays.M. S. Ramaiah Institute of Technology 11
  • 12. each bead is a dipolespheres are embedded in a transparent silicone sheet,suspended in a bubble of oil so that they can rotate freely.polarity of the applied voltage by the backplane to each pair of electrodes determineswhether white or black face is up.Thus giving the pixel a white or black appearance in the front-plane.bi-chromal front-plane had a number of limitations, including relatively low brightness andresolution and a lack of color.used only in message boardsM. S. Ramaiah Institute of Technology 12Polyethylenespheres, 75 to106micrometers-ve Chargedwhite plastic+ vechargedBlackPlastic
  • 13. Electrophoretic Ink- Rearranging charged pigmentparticles using an applied electric field• Developed by the E Ink CorporationM. S. Ramaiah Institute of Technology 13Millions ofMicrocapsules,100micrometers indiameter(size of ahuman hair)Each capsule contains- Oily solution (black dye)-numerous suspendedtitanium dioxide particlesTitanium particles–vely charged andnaturally white
  • 14. M. S. Ramaiah Institute of Technology 14• The brightness and resolution of electrophoretic-based e-inkis better than that of gyricon-based e-ink, but both aremonochromatic in nature.• To create color, E Ink joined hands with the Japanesecompany Toppan Printing, which produces color filterUsingMicrocapsuleAllowed the display to be usedon flexible plastic sheets insteadof glass
  • 15. Generations of E-inkE Ink Vizplex -internal name of E Inks current line of display technologiesE Ink Pearl- is the second generation of E Ink Vizplex displays, a highercontrast screenE Ink Triton - third generation of E Ink Vizplex displays: a colour display that iseasy to read in high light. The Triton is able to display 16 shades of gray,and 4096 colours.Drawback of electrophoretic e-ink is– Low Refresh rate  causing Ghost of the images.– drawing a new text or image is too slow and creates a flicker effect.M. S. Ramaiah Institute of Technology 15
  • 16. • Cholesteric based bi-stable display– Possess a helical structureThe planer texture» They reflect circularly polarized lightThe focal conic texture» Scatter light in forward directionSwitched from planar to focal conic texture by Low VoltageFocal conic texture to planar by high voltageUsed in price labels,e-books.• Electrowetting– Modification of the wetting properties of a surface(typically hydrophobic)with applied electric field• Electrochromic– Reversibly changing color when a burst of charge is appliedAre other technologies used to increase resolution.M. S. Ramaiah Institute of Technology 16
  • 17. Self-Emissive based flexible displays-FOLEDM. S. Ramaiah Institute of Technology 17A flexible organic light emitting diode (FOLED) is a type of organic light-emittingdiode (OLED) incorporating a flexible plastic substrate on which the electroluminescentorganic semiconductor is deposited. This enables the device to be bent or rolled whilestill operating. The organic semiconductor is situated between two electrodes. Generally,at least one of these electrodes is transparent. An OLED display works withouta backlight
  • 18. How OLED technology works?M. S. Ramaiah Institute of Technology 18Substrate (clear plastic, glass, foil) -The substrate supports the OLED.(polyethylene terephthalate (PET))Anode (transparent) – positivelycharged wrt to cathode, provides"holes“ when a current flows throughthe device.(Indium Tin Oxide)Cathode (may not be transparent) -The cathode injects electrons whena current flows through the device.(Barium or Calcium)Conducting layer-made of organicplastic molecules that transport"holes" from the anode.(polyaniline)Emissive layer-made of organicplastic molecules (different from theconducting layer) that transportelectrons from the cathode; this iswhere light is made.(polyfluorene.)
  • 19. M. S. Ramaiah Institute of Technology 19OLED light is createdthrough a process calledelectrophosphorescence•The color of the lightdepends on the type oforganic molecule in theemissive layer.•Manufacturers place severaltypes of organic films on thesame OLED to make colordisplays.•The intensity or brightnessof the light depends on theamount of electrical currentapplied: the more current,the brighter the light.
  • 20. Small molecule OLED vs Polymer OLED• Although small molecules emit bright light, deposition ontothe substrates is by thermal evaporation process in vaccum.• This is an expensive manufacturing process called vacuumdeposition. For depositing thin films of Polymers-Vacuum deposition isnot a suitable method. However, polymers can be processed in solution, and spincoating is a common method of depositing thin polymer films. This method is more suited to forming large-area films thanthermal evaporation. No vacuum is required, and the emissive materials can also beapplied on the substrate by a technique derived fromcommercial inkjet printing.M. S. Ramaiah Institute of Technology 20
  • 21. M. S. Ramaiah Institute of Technology 21OLED ACTIVE AND PASSIVE DISPLAYS
  • 22. Advantages and DisadvantagesFOLED•Advantages•Thinner(hence brighter), lighter ,flexible(usedplastic instead of glass)•Backlight not required hence consume lesspower•easier to produce and can be made to largersizes. As they are essentially plastics, they canbe made into large, thin sheets. It is muchmore difficult to grow and lay down so manyliquid crystals.•Large field of view about 170 degrees•Low heat generation•Low Power requirement•Contrast Ratio Over 1,000,000:1DisadvantagesLifetime -Red and green OLED films havelonger lifetimes (46,000 to 230,000 hours),blue organics currently have much shorterlifetimes (up to around 14,000 hoursresidual stress from the deposition of layersonto a flexible substratethermal stresses due to the differentcoefficient of thermal expansion of materials inthe device,in addition to the external stressfrom the bending of the device.•Manufacturing - Manufacturing processes areexpensive right now.•Water - Water can easily damage OLEDs.M. S. Ramaiah Institute of Technology 22
  • 23. Its wide variety of applications..1. Smart Cards, Electronic Paper2. Mobile communications3. Personal computers/portable displays/E-Readers4. Large area displays5. Wearable Electronics6. Automotive Applications7.Non-display Applications (toys, plastic arts etc.)8. Electronic billboardsM. S. Ramaiah Institute of Technology 23
  • 24. M. S. Ramaiah Institute of Technology 24
  • 25. Challenges• Encapsulation is challenge for flexible OLED devices.• Integration of componentsConclusion• Flexible electronic displays have theopportunity to revolutionize an Industry.• Effort to understand the failure limits andmechanisms have been gaining momentum.M. S. Ramaiah Institute of Technology 25
  • 26. References• Development of a Flexible Electronic Display Using Photographic Technology by Stanley W. Stephenson,David M. Johnson, John I. Kilburn, Xiang-Dong Mi, Charles M. Rankin, Robert G. Capurso• Flexible Electronics: The Next Ubiquitous Platform byBy Arokia Nathan, Fellow IEEE, Arman Ahnood, Matthew T. Cole, Sungsik Lee, Member IEEE, Yuji Suzuki,Pritesh Hiralal, Francesco Bonaccorso,Tawfique Hasan, Luis Garcia-Gancedo, Andriy Dyadyusha, SamiulHaque,Piers Andrew, Stephan Hofmann, James Moultrie, Daping Chu, Andrew J. Flewitt,Andrea C.Ferrari, Michael J. Kelly, John Robertson, Fellow IEEE,Gehan A. J. Amaratunga, and William I. Milne• Invited Paper: Ultra-thin and Flexible LSI Driver Mounted ElectronicPaper Display using Quick-Response Liquid-Powder Technology Ryo Sakurai, Reiji Hattori+, MichihiroAsakawa+, Takuro Nakashima+, Itsuo Tanuma,Akihiko Yokoo, Norio Nihei, and Yoshitomo Masuda• Distinguished Paper: Ultra Thin and Flexible Paper-Like Display using QR-LPD Technology Reiji Hattori,Shuhei Yamada• IBM Research Report Unraveling Flexible OLED Displays for Wearable Computing ChandraNarayanaswami, M. T. Raghunath• Flexible and Roll-able Displays/Electronic Paper A Brief Technology OverviewRong-Chang (R.C.) Liang• Flexible display enabling technology Sigurd Wagnera, Stephen J. Fonashb, Thomas N. Jacksonb, James C.Sturma aPrinceton University, bPennsylvania State University• Resources from How Stuff Works.• Resources From Wikipedia. M. S. Ramaiah Institute of Technology 26
  • 27. Thank YouM. S. Ramaiah Institute of Technology 27