EP1552358A2 - Dispositif afficheur a sequence de champ et ses procedes de fabrication - Google Patents

Dispositif afficheur a sequence de champ et ses procedes de fabrication

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Publication number
EP1552358A2
EP1552358A2 EP03741980A EP03741980A EP1552358A2 EP 1552358 A2 EP1552358 A2 EP 1552358A2 EP 03741980 A EP03741980 A EP 03741980A EP 03741980 A EP03741980 A EP 03741980A EP 1552358 A2 EP1552358 A2 EP 1552358A2
Authority
EP
European Patent Office
Prior art keywords
polarizer
display device
light scattering
scattering material
recited
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03741980A
Other languages
German (de)
English (en)
Other versions
EP1552358A4 (fr
Inventor
Homer L. Webb
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP1552358A2 publication Critical patent/EP1552358A2/fr
Publication of EP1552358A4 publication Critical patent/EP1552358A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133621—Illuminating devices providing coloured light
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133621—Illuminating devices providing coloured light
    • G02F1/133622—Colour sequential illumination

Definitions

  • the present invention relates to the field of flat panel displays, and more particularly to a flat panel display comprising cells that include light scattering material between a light source and a viewing surface enabling a field sequential color display.
  • LCDs liquid crystal displays
  • PDP plasma display panels
  • EL electroluminescence displays
  • CRT cathode-ray tube displays
  • TFT-LCD thin film transistor liquid crystal display
  • Figure 1 illustrates a profile view of a cell or pixel 100 of a TFT-LCD device.
  • Cell 100 may comprise two outer layers consisting of polarizers 101, 102, substrates 103, 104 composed of glass, indium tin oxide (ITO) coatings 105, 106, a rubbed polymeric alignment layer 107, 108, electro-optical liquid crystal twisted nematic (TN) material 109, active element TFT transistor 110, metal select and data electrodes 111, 112, color filter 113, light guide 114, and back light 115.
  • ITO indium tin oxide
  • TN electro-optical liquid crystal twisted nematic
  • the cell gap is the space between 107 and 108. This gap is invaded by elements 111, 112, and 110, which constrain the gap dimensions of the electro-optical material 109.
  • active device 110 requires an expensive semiconductor process.
  • active devices 110 may reside inside substrates 107, 108 which limit the cell gap.
  • the drive electrodes 111, 112 may be patterned onto the surface of the ITO coating 106 which is coated onto substrate 104.
  • the thickness of electrodes 111,112 and transistor 110 may be made thin.
  • the width of electrodes 111,112 may be increased.
  • a consequence of thin and wide electrodes 111, 112 and a thin transistor 110 may be a reduction in the aspect ratio of cell 100 as well as a limitation in the dimension of the display.
  • the manufacturing requires a multiplicity of carefully controlled steps. For example, the electro-optical effect of the liquid crystal molecule requires careful alignment of the molecules, necessitating expensive preparation of rubbing polymer layers 107 and 108.
  • field sequential color (FSC) systems have been employed in direct view and projection modes based on reflective scattering LCDS, however liquid crystal dispersion systems such as polymer dispersed liquid crystal (PDLC), have not been developed for transmissive FSC presumably due to the perceived lack of optical contrast with such systems.
  • PDLC polymer dispersed liquid crystal
  • the primary advantage of PDLC is reportedly the lack of a need for polarizers; thus, uses of PDLC in display applications focuses on the reflective scattering mode - direct view and projection - without the use of polarizer films.
  • the transmissive LCD-based approaches to FSC include ferroelectric (U.S. Pub. No. 2001/0035852), optically controlled birefringence (OCB) or pi-cell (U.S. Patent No. 4,582,396, and U.S. Pub. No. 2002/0140888, U.S. Pub. No. 2002/0145579, and U.S. Pub. No. 2002/0149551; and U.S. Pub. No. 20020149576 of Yukio et al.), and modified drive techniques applied to TN displays (as reported by Hunet and Bright Lab Co, of Japan, U.S. Patent No. 6,424,329 and U.S. Pub. No. 2001/0052885).
  • Each of these approaches have their own benefits but also problems with respect to production or cost-performance vis a vis incumbent color LCDs.
  • a display device having first and second polarizers.
  • a light scattering material is disposed between the first and second polarizers.
  • the display includes a light source having a plurality of colors. Portions of the light scattering material are operable for selectable excitation. An excitation of a portion of the light scattering material is operable for controlling an amount of light of a color of the plurality of colors emitted by the display device.
  • Figure 1 illustrates a profile view of a TFT LCD display device
  • Figure 2 illustrates a light scattering display cell in accordance with an embodiment of the present invention
  • Figure 3 illustrates a cell similar in figuration to the cell of Figure 2 including dry circuitry associated therewith;
  • Figure 4 illustrates an embodiment of a cell for use in a reflective display
  • Figure 5 illustrates an exploded view of a display device in accordance with an embodiment of the present invention
  • Figure 6 illustrates, in schematic form, a driver circuitry which may be used in conjunction with the display embodiment of Figure 5;
  • Figure 7 illustrates an exploded view of an alternative embodiment of a display device in accordance with the present invented principle
  • Figure 8 illustrates, in schematic form, an act of device which may be used in conjunction with the embodiment of Figure 7;
  • Figures 9A-9C illustrates, in flow chart form, a field sequential color methodology in accordance with embodiments of the present invention
  • Figure 10 illustrates, in flow chart form, a methodology for manufacturing a liquid crystal display device in accordance with an embodiment of the present invention in which a metal oxide varistor as used as an active element;
  • Figure 11 illustrates, in flow chart form, a process for manufacturing a liquid crystal display device in accordance with an alternative embodiment of the present invention in which a transistor is used as an active element;
  • Figure 12 illustrates, in flow chart form, an alternative methodology for manufacturing a liquid crystal display using a transistor as an active element
  • Figure 13 illustrates, in flow chart form, a method of manufacturing a liquid crystal display device in accordance with an alternative embodiment of the present invention.
  • a field sequential flat panel display device and methods of manufacturing such devices are provided.
  • Field sequential color (FSC) displays enables the display of color without the use of color filters, but rather through the use of fast switching liquid crystal material (or other optical material) in combination with fast switching light sources comprised of different colors. Rather than sub-pixels for spatial modulation of color, FSC displays use temporal multiplexing of colored light in one pixel to show color.
  • Scattering LCDs of the type made with localized volumes created either by the addition of polymer or other techniques, in combination with crossed-polarizers provide a direct view display device.
  • Such devices have been described in U.S. Provisional Patent Application Serial No. 60/388,237, entitled “Solid State Display”, filed on June 13, 2002, and U.S. Provisional Patent Application Serial No. 60/443,053, entitled “Solid State Display”, filed on January 28, 2003, both of which are hereby incorporated herein by reference.
  • Displays using a scattering medium such as scattering LCDs may in accordance with the present inventive principles include liquid crystal dispersion systems (LCDS) which represent one embodiment of a display device based on a light scattering medium to modulate the transmittance of the display to create a displayed image. Additionally, other embodiments of the present invention may use scattering media other than light scattering cells of the LCDS type. Each of theses classes of light scattering materials will be discussed further below. It would be appreciated by those of ordinary skill in the art that the present inventive principles may be practiced with any scattering medium exhibiting the required optical and switching characteristics imposed on display devices by the attributes of human perception, such a persistence of vision.
  • LCDS liquid crystal dispersion systems
  • LCDS may be defined to encompass all light scattering liquid crystal systems whereby multiple surfaces are created in the cell; including as examples, but not limited to, the following systems: polymer dispersed liquid crystal (PDLC), reverse-mode PDLC (such as described in U.S. Patent Nos.
  • PDLC polymer dispersed liquid crystal
  • reverse-mode PDLC such as described in U.S. Patent Nos.
  • IRIS Internal-Reflection Inverted-Scattering
  • H-PDLC holographic PDLC
  • NCAP nematic curvilinear aligned phase
  • PNLC polymer network liquid crystal
  • PELC polymer encapsulated liquid crystal
  • PSCT polymer stabilized cholesteric texture
  • PSCOF phase separated composite film
  • colloidal templated liquid crystal composition such as the composition disclosed in U.S. Pub. No. 2001/0035918, which is hereby incorporated herein by reference, PMMA resin LC composition, and LC and macromolecular LC molecule compositions.
  • LCDS may also include LC mixtures including dispersed nanoparticles (such as silica made by Nanotechnology Inc., Austin, TX or Altair Nanotechnology, Reno, NV) which creates the necessary effect to enable light scattering by the LC molecules.
  • dispersed nanoparticles such as silica made by Nanotechnology Inc., Austin, TX or Altair Nanotechnology, Reno, NV
  • the particles themselves are small and transparent.
  • LCDS may also include those LCDS made with channels, pockets or other cavities within the cell which have the same effect as polymer dispersion for scattering light.
  • Examples of such techniques may be Plastic PixelsTM a product and process of Viztec, Inc., Cleveland, OH, Microcup LCD, a product and process by SiPix Imaging, Milpitas, CA, (described in U.S. Pub. No. 2002/0126249 Al, which is hereby incorporated herein by reference) and PoLiCryst, as described by L. Vicari, J. Opt. Soc. Am. B, Vol. 16 pp. 1135-1137 (1999), which is hereby incorporated herein by reference.
  • micropores of a plastic sheet with a nematic or other type of liquid crystal (as disclosed in U.S. Patent No. 4,048,358, which is hereby incorporated herein by reference).
  • Such pores could be fabricated today for example with microreplication technologies employed by such companies as 3M, Minneapolis, MN and Avery Dennison, Pasadena, CA or for example utilizing the a pixilated foil platform such as that developed by Papyron B.V., The Netherlands.
  • embodiments of the present invention are not only limited to light scattering cells of the LCDS type, but also may include other light scattering liquid crystal materials such as chiral nematic liquid crystal or cholesteric liquid crystal which exhibits a light scattering mode in the focal conic state and a transparent state in the planar state.
  • smectic A liquid crystal is also known to scatter light in one state and change to a transparent state in another state. Cholesteric and smectic A liquid crystal do not require a polymer network or dispersion within a polymer matrix to create the scattering effect, but may be created with a polymer network.
  • this invention is also applicable to non-liquid crystal materials which may be optically switched from a light scattering state to a substantially light transparent state.
  • small particulate matter may be suspended in a medium and behave in the same manner (scattering and non-scattering) as described herein.
  • One such example of particulate matter suspended in a medium is Suspended Particle Device (SPD) light control technology developed by Research Frontiers, Inc., Woodbury, NY. This is only one of several types of non-liquid crystal electro-optical (switchable) light scattering materials which could be used in conjunction with the present inventive principles.
  • SPD Suspended Particle Device
  • Figure 2 illustrates an embodiment of the present invention of a cell or pixel 200.
  • a display may be fabricated f om a plurality of cells 200.
  • Cell 200 may include three layers including a top polarizer 201, a light scattering material 202 such as liquid crystal dispersion systems (LCDS) or other electro-optical scattering materials as previously discussed hereinabove.
  • light scattering material may be a PDLC.
  • cell 200 may include a bottom polarizer 203.
  • Top polarizer 201 may be coated with a substantially transparent conductive material 204 such as Indium-Tin-Oxide (ITO).
  • Bottom polarizer 203 may be coated with a substantially transparent conductive material 205.
  • a plastic or polymer may hold polarizers 201, 203 eliminating glass or other substrates used in conventional displays.
  • light scattering material 202 may be configured to capture nematic liquid crystal into very small droplets called "bubbles". Once light scattering material 202 hardens, the bubbles are captured. Further, light scattering material 202 may be configured to harden to form a gas fight bond between polarizers 201, 203.
  • a PDLC composition that may be used includes a commercially available liquid crystal BL035 available from Merck Specialty by Chemicals, Ltd. Poole, UK, dispersed in a ultraviolet (UV) curing epoxy MXM35 available from FFLgnacsfluid GmbH, Mainz-Hechtsheim, Germany. For example, in one such composition that may be used the epoxy and liquid crystal may be in the ratio of about thirty percent (30%) epoxy to about seventy percent (70%) liquid crystal.
  • light scattering material 202 may be configured to harden to form a bond between polarizers 201, 203. Moreover, by incorporating light scattering material 202 in cell 200, a liquid filling process as required in prior art LCD displays may no longer be required. And, by replacing LCD material with light scattering material 202, the critical vacuum seal around the edges may be eliminated.
  • Figure 2 also depicts a light source, LEDs 209, to illustrate the use of cell 200 in a display configuration.
  • LED's 209 may replace the flourescent light source used in conventional LCD displays, and eliminate the need for expensive color filters. Additionally, because LEDs may be switched in conjunction with the switching of electro-optical scattering material 202, a field sequential color display may be fabricated using a cell 200 in accordance with the present inventive principles. Additionally, such operation eliminates two-thirds of the number of data drivers that are otherwise needed in a conventional LCD display as the same driver may be used to exhibit all three colors (red, green and blue). Additionally, this increases the aperture- ratio of the pixel since cell 200 is not divided into red, green and blue sub-pixels as in a conventional LCD display.
  • light scattering material may constitute a LCDS. It is noted that light scattering material may be any material capable of switching between a first state to a second state where in the first state, the light scattering material is substantially non-scattering in at least the operable portion of the light spectrum for which the display is to be used, and where in the second state the light scattering materials is substantially non-scattering in that portion of the spectrum.
  • the operable portion of the spectrum is the visible light spectrum
  • the present inventive principles may be used application in which at least one of the light sources is in the nonvisible portion of the spectrum.
  • a night vision application for example, may use an infrared light source.
  • the transition of the light scattering material between the first and second states (and vice versa) may be substantially continuous as a function of the voltage across the cell, whereby an amount of light scattering also varies continuously. This is described further hereinbelow.
  • Contrast is achieved by the ratio of the maximum transmission - also referred to as the bright ( optical ON) state - through the display compared to the dark (optical OFF) state.
  • the light scattering material is substantially transparent, the incoming polarized light from the backlight and first polarizer layer is unaffected, substantially blocked by the front polarizer and the optical OFF or dark state is achieved.
  • the light scattering material is in its most scattering bright (optical ON) state, the incoming polarized light is scattered, which effectively depolarizes the light enabling transmission through the front polarizer and the optical ON or bright state is achieved.
  • a display device may incorporate a plurality of cells 200. Such a display may include drive circuitry in conjunction with each cell to modulate the light transmittance of the cell by modulating the light scattering by the opto-electronic scattering medium.
  • Figure 3 illustrates a cell 300, similar in configuration to cell 200 in Figure 2 and further including drive circuitry associated therewith.
  • Polarizers 301 and 303, conductive material 304 and 305, light scattering material 302 and light source 309 are respectively similar to polarizers 201, 203, conductive material 204 and 205, light scattering material 202 and light source 209 in Figure 2.
  • Drive electrodes include row select 306, and data line (or, equivalently, column select) 307.
  • electrodes 306 and 307 are coupled to active element 308.
  • An active element may include an amorphous silicon (a-Si) thin film transistor (TFT), a polysilicon TFT, TFT, a CdSe TFT or other switching device such as a metal-insulator-metal (MIM) diode, or a metal oxide varistor (MOV) as described in further detail hereinbelow.
  • Electrodes 306, 307 may be bonded directly to polarizer 303 since a plastic or polymer may hold polarizer 303. Hence, the need for printed circuit boards (PCBs), printed wiring boards (PWBs) or tape automated bonding (TAB) may be eliminated.
  • PCBs printed circuit boards
  • PWBs printed wiring boards
  • TAB tape automated bonding
  • circuits 306, 307 may be configured to be thicker than in prior art thereby allowing very long thick but thin traces of the desired resistance.
  • active element 308 is placed inside the profile allowing more surface area while reducing the aspect ratio of cell 300 and permitting higher resolution pixel display densities.
  • cell 300 does not place any components inside the critical cell gap (spacing between the top and bottom electrodes) as in conventional displays.
  • cell 300 may be used to display materials such as supertwist nematic (STN), twisted nematic (TN), cholesteric, organic LED, electroluminescent (EL), electrophoretic ink (E-ink) and electrophoretic paper (E-paper).
  • STN supertwist nematic
  • TN twisted nematic
  • cholesteric organic LED
  • EL electroluminescent
  • E-ink electrophoretic ink
  • E-paper electrophoretic paper
  • Figure 4 illustrates another embodiment of a cell 400 incorporating the principles of the present invention that allows construction of a reflective display using off-the-shelf components.
  • Cell 400 is configured substantially the same as cell 300 ( Figure 3) except polarizers 301, 303 ( Figure 3) of cell 300 are replaced with polymer or glass substrates 401, 402.
  • Substrates 401, 402 may each be coated with electrical conductive material (404, 407, respectively).
  • substrate 402 may not be transparent.
  • Conductive material 404 may be transparent, e.g., ITO, and coating 407 may be a solid conductive paint or print.
  • Substrate 402 may be dimensioned to hold active component 406. Color element 403 may be added.
  • Figures 5 Exploded Views
  • Display device 500 may be particularly adapted for use with a metal oxide varistor 530 (MOV) as the active device and a passive device 532 resistor.
  • Display device 500 includes top and bottom polarizers, 502 and 504, respectively.
  • An LED light source 506 including at least a tri-colored set of LEDs (primary colors, red, green and blue) are disposed behind polarizer 504. Additionally a fourth, white LED may also be included in light source 506. (It would be appreciated by those of ordinary skill in the art that the depiction of light source 506 is schematic, and that an backlight embodiment would include a multiplicity of LED devices for each color.
  • bottom polarizer may be omitted if a polarized light source is used.
  • laser diode sources may be used to provide a polarized source.
  • a polarization mechanism may be integrated with the LEDs.
  • One such device is the ProFlux MicrowireTM polarizer supplied by Moxtek, Inc., Orem, UT.
  • polarizer films need not be placed on the outside of the substrate.
  • the polarizers may be placed on the inner surface of the substrate, for example using thin crystal film (TCFTM) polarizer technology as is available from Optiva, Inc., South San Francisco, CA. Such placement may reduce parallax.
  • TCFTM thin crystal film
  • Upper substrate 508 may be glass in an embodiment of the present invention.
  • Electrically conductive data lines 514 may be disposed on a bottom surface of upper substrate 508.
  • Data lines 514 may be fabricated from ITO, for example, and the grooves therebetween formed by laser etching other etching methods scribing or printing.
  • Lower substrate 512 provides a supporting structure for the electronic components of the display device. These may include row and column drivers 518 and 516, which are respectively coupled to select lines 522 and data lines 520, and mounted to the bottom surface of lower substrate 512.
  • Data lines 520 may be electrically coupled to corresponding ones of data lines 514.
  • Display device 500 also includes drivers for each cell, which may comprise active driver members 530 and passive driver members 532. Active driver members 530 and passive driver members 532 may be disposed within corresponding holes 536 in substrate 512. Active driver members 530 may be MOV devices, and passive driver members 532 may be resistors. Active driver members 530 may be coupled to corresponding ones of select lines 522 and passive members may be coupled to corresponding ones of data lines 520.
  • FIG. 6 illustrating a schematic representation of a driver 600 comprised of an active member 530 and passive member 532.
  • Capacitor 602 represents the parasitic capacitance of a cell.
  • Node 604 corresponds to the electrical interconnnection between data lines 520 and data lines 514 described hereinabove.
  • Line 606 represents the electrical connection between passive member 532 and active member 530 formed by conductive coating 526.
  • the active member provides a threshold for the electro-optic scattering medium.
  • the device remains inactive for at least one-half the applied voltage, V on .
  • V on the applied voltage
  • the device is essentially fully on at the applied voltage V orij it is desirable to be fully off at 0.5 V on Volts.
  • the data voltage on data 522 voltage is at 0.5V on Volts
  • no other cell in the column can turn on unless the voltage across the cell is V on Volts-
  • the select or row voltage (on the corresponding select 520) has to go to a negative value, or -0.5V O n Volts.
  • the data voltage is at ground and the row voltage is at -0.5V on Volts the cell should not turn on.
  • a MOV can be made to turn on at any desired voltage, primarily by changing the thickness, which sets the distance between the input and output electrodes.
  • the MOV may be selected to operate at the desired threshold.
  • the MOV may be selected to have a turn-on voltage (commonly referred to as the MOV breakdown voltage) of about 5 volts.
  • active members 530 are shown to be located between the select electrodes and the bottom electrode of the cells. Alternatively the active members may be located between the top of the cell and the data electrodes.
  • the MOV active member also acts as a switch that will not let the cell discharge. This allows the cell to perform similarly to an active matrix device. Thus, the display does not depend on average voltage to operate. The result is that the display performance may be similar to active matrix displays.
  • FIGURE 7 illustrates an exploded view of another embodiment of a display device 700 in accordance with the principles of the present invention.
  • Display device is similar to device 500 of FIGURE 5 and includes top polarizer 702, opto-electronic light scattering medium 710 and a lower polarizer 712.
  • Electrically conductive top electrode 714 may be disposed on a bottom surface of polarizer 702.
  • Lower polarizer 712 may provide in the illustrated embodiment, a supporting structure for the electronic components of the display device which may include row and column drivers 716 and 718, which are respectively coupled to select lines 720 and data lines 722. Additionally, lower polarizer 712 may form a light channel for the light supplied by LED light source 706.
  • a lower substrate similar to lower substrate 512, Figure 5, may be used in conjunction with a lower polarizer, similar to bottom polarizer 504, Figure 5, or alternatively, a polarized light source.
  • LED light source 706 may include at least a tri-colored set of LEDs (primary colors, red, green and blue). Alternatively, LED light source 706 may also have a white LED (not shown).
  • the operation of display device 700 is similar to that of display device 500.
  • An active element 800 mounted on polarizer 712 may be used as an alternative to active element 530 and passive element 532 shown in FIGURE 5. Active element 800 uses only one hole 736 through polarizer 712.
  • active element 800 may be a TFT or similar device including a drain 801, source 802 and gate 803.
  • the corresponding structures are also illustrated in Figure 7.
  • Figures 9A-9C Operation of Field Sequential Color
  • a field sequential color display in accordance with the present invention may be further understood by referring to Figures 9A-9C.
  • the generation of an image frame starts in step 902 of process 900 for generating a field sequential display in accordance with an embodiment of the present invention.
  • Process 900 then enters a loop over sub-frames in step 904.
  • a sub-frame may be understood to be any portion of a complete frame of an image being rendered on the display; the complete frame being a composite of sub-frames.
  • field sequential color may be perceived to constitute the sequential display of three monochrome sub-frames in which all pixels of the display are addressed in each sub-frame.
  • a sub-frame is not restricted to be monochromatic illumination, nor are the sub-frames necessarily three in number.
  • step 906 the sub-frame is displayed. Step 906 will be described further in conjunction with Figures 9A and 9B (where, for clarity the alternative embodiments have been labeled 906a and 906b, respectively). If the current sub-frame is not the last sub-frame of the image frame, process 900 returns to step 904 to continue looping over sub-frames. Otherwise a new frame starts in step 902.
  • step 906 in further detail for a field sequential color methodology in accordance with an embodiment of the present invention.
  • step 926 the sub-frame is addressed, whereby the illumination values are stored in the pixels (or equivalently cells) of the sub-frame.
  • a delay may be employed.
  • a delay may be used to allow time for the light scattering material to reach a substantially stabilized state.
  • electro-optic light scattering materials may be switched from a light scattering state to a substantially light transparent state and a continuum of light scattering states therebetween.
  • step 930 the light source is flashed.
  • the duration of the flash is determined by several factors, including but not limited to the sub-frame refresh rate, the addressing speed, the response of the display medium to a substantially stabilized state, and other human factors related issues. These factors are recognized to those skilled in the display art. And typical values may be in the range of about 1 to about 20 ms.
  • Step 906a then continues with step 908, Figure 9A.
  • step 906b An alternative embodiment of a field sequential color display methodology in accordance with the present invention, which may be referred to a segmented field sequential color (SFSC) is illustrated in Figure 9C (step 906b).
  • step 906a may be understood as a subset of step 906b in which a sub-frame comprises a single segment, or stated conversely, an SFSC having a single segment.
  • step 956 loop over segments is entered.
  • step 958 the pixels corresponding to a segment are addressed.
  • a segment may include a preselected subset of pixels whereby the entire display constitutes the union of the segments.
  • the addressing in step 956 may address a portion of the sub-frame.
  • a delay may be employed. As previously noted, a delay may be used to allow time for the light scattering material to reach a substantially stabilized state. Recall that electro-optic light scattering materials may be switched from a light scattering state to a substantially light transparent state and a continuum of light scattering states therebetween.
  • the light source is flashed.
  • the duration of the flash is determined by several factors, including but not limited to the sub-frame refresh rate, the addressing speed, the response of the display medium to a substantially stabilized state, and other human factors related issues. These factors are recognized to those skilled in the display art. And typical values may be in the range of about 1 to about 20 ms.
  • a light source may be designed to be a segmented light source which may be used in conjunction with segmented addressing described in step 956.
  • a typical three color (RGB) field sequential display three light color sources are switched "OFF" while the specific color pattern is written to the entire sub-frame. Since a typical display operates at 60 Hz or 16.66 milliseconds this leaves approximately 5.5 milliseconds per sub-frame. This means that the display drivers must operate 3 times faster than normal. However, this does not leave any time to turn on the light sources. Therefore, it is desirable to write to the entire display in 1 millisecond, leaving 4.6 milliseconds to turn on the light source. This puts an even higher burden on the display driver circuits to run 16 times faster.
  • the respective color light source remains “ON” for most of the time, approximately 5.5 milliseconds, and is only switched “OFF” during the time the drivers are writing to the pixels in the segmented sub-frame. If that segmented sub-frame constitutes 20 rows of a VGA display (640 x 480), as a further example, at 60 Hz frame rate this will be 16.66 ms/480/20 or 694.44 microseconds leaving 4.80 milliseconds for the light to be on. As discussed below, two benefits are apparent from this approach. First, the drivers can write at slower speeds.
  • the time the segmented image frame is illuminated is longer since the address time for a segmented sub-frame is less than the time required to address a complete sub-frame. This time difference is additional time the light source may stay flashed on for the segmented sub- frame.
  • steps 956-964 are inside the loop over sub-frames (step 904, Figure 9A).
  • each segment is addressed, and therefore within each sub-frame, all pixels (or equivalently cells) are addressed.
  • the color of the light source flashed in step 962 need not be the same.
  • the color of the light source flashed in step 962 may be a first color, say red, for example.
  • the color of the light source flashed in step 962 may be a second color, say green.
  • each segment in the loop over segments may sequence through the colors comprising the light source.
  • a display in accordance with the present invention may be divided into segments each composed of n select lines or rows of pixels. For illustration suppose n is five. At typical frame rates of about 120 Hz - 190 Hz each segment may be written in 1.1 milliseconds. For an XGA of 1024 columns X 1024 rows, each segment would be composed of 1024 /5 or approximately 205 lines or rows.
  • the segment is written in 1 millisecond leaving 4.5 milliseconds for the light source to add color, implying a writing speed 4.8 microseconds per row.
  • the result is slower writing speed (4.8us) for SFSC than for FSC (2.9us). Because the time the segment is on is longer a slower responding LCD or scattering material may be used.
  • sub-frame contains one-third of the full color image frame (for a three-color system) and it is harder for the eye to see changes in the image as the extra one-third is added each sub-frame.
  • the result is that human eye sees less flicker and the sub-frame rate may be reduced from for example 120 Hz to about 25-30 Hz.
  • Step 906b then continues with step 908, Figure 9A.
  • FIG. 10 A method of manufacturing a liquid crystal device in accordance with the current invention, using a metal oxide varistor (MOV) as the active element, is shown in Figure 10.
  • MOV metal oxide varistor
  • step 1005 top and bottom polarizers are provided, such as 502 and 504 in Figure 3. These polarizers have interior and exterior surfaces.
  • the interior of the top polarizer is coated with a conductive material, such as ITO, in step 1010.
  • a data pattern is then etched into that conductive coating in step 1015.
  • a light scattering material is then deposited in step 1020.
  • step 1025 Drive electrodes and cell data and source electrodes are etched or printed onto the exterior surface of the bottom polarizer in step 1025.
  • step 1030 sets of first and second holes are fabricated through the bottom polarizer.
  • step 1035 metal oxide varistor active elements are then printed or installed into the first holes through the bottom polarizer so that one electrode of the active element is resident to the interior surface of the polarizer, but not pertruding past the plane of the interior surface.
  • step 1040 passive elements are printed or installed into the second holes through the bottom polarizer so that they are congruent to but not protruding past the plane of the interior surface of the bottom polarizer.
  • the interior of the bottom polarizer is coated with a conductive medium in step 1045. This conductive medium, shown as 526 in Figure 5, will make an electrical contact between the active and passive electrical elements.
  • step 1050 a cell pattern is etched in the conductive material deposited in step 1045.
  • Step 1055 involves filling the electrode pattern on the exterior surface of the bottom polarizer with conductive ink, provided that this was not previously printed in step 1025.
  • a crossover electrode pattern is printed or masked on the exterior of the bottom polarizer in step 1060.
  • crossover electrodes are printed or masked on to the exterior surface of the bottom polarizer.
  • the top and bottom polarizer assemblies are then bonded together in step 1070 and the data pattern on the top polarizer is interconnected with the data electrode pattern on the bottom polarizer in step 1075.
  • Top and bottom polarizers are provided in the step 1105. These polarizers also comprise the top and bottom substrates and have surfaces both interior to and exterior to the cell.
  • the interior of the top polarizer is coated with a conductive material, such as ITO, in step 1110.
  • a light scattering medium 510 is then deposited onto the coated interior surface of the top polarizer in step 1115.
  • Driver electrodes and cell and data source electrodes are etched or printed onto the exterior surface of the bottom polarizer 504 in step 1120.
  • step 1125 holes are fabricated through the bottom polarizer, which are then filled with a conductive material in step 1130.
  • This conductive material forms an electrical conduit between the interior and exterior surfaces of the bottom polarizer.
  • the interior of the bottom polarizer is coated with a conductive medium in step 1135, which makes an electrical contact with the conductive material filled into the holes in step 1125.
  • a cell pattern is then etched into the conductive material coated on in 1135, if not previously printed in that step.
  • the electrode pattern on the exterior of the bottom polarizer is then filled with conductive ink in step 1145, if this has not previously been done as part of step 1120.
  • An electrode crossover pattern is printed or masked onto the exterior of the bottom polarizer at the intersection of the data source electrodes, in step 1150 and then crossover electrodes are printed or masked on in step 1155.
  • the active element transistors are installed to make electrical connections between the row and data electrodes and the electrical conduits through the polarizer; this includes connections between data and drain, gate and row, and source to conduit.
  • the two polarizer assemblies are then bonded to one another in step 1165.
  • a top polarizer is printed onto the exterior surface of a substrate.
  • the interior of that substrate is coated with a conductive material, such as ITO, in step 1210.
  • Light scattering material is deposited onto the conductive material in step 1215.
  • the light scattering material is then coated with a conductive material layer, such as ITO, in step 1220.
  • a bottom substrate is then provided, onto which the bottom polarizer is printed, holes are masked or printed for pass-through conductors and a waffle pattern is printed 1225.
  • Driver electrodes and cell data and source electrodes are printed onto the exterior surface of the bottom polarizer in step 1230.
  • the holes through the bottom substrate are then filled with conductive material, in step 1235, thus forming an electrical conduit between the interior and exterior surfaces.
  • An electrode crossover pattern is then printed or masked onto the exterior surface of the bottom substrate in step 1240, and then crossover electrodes are then printed or masked onto that substrate in step 1245.
  • Active element transistors are then installed in step 1250, to make electrical connections among the row and data electrodes and electrical conduits; this includes connections between drain and data, gate and row, and source to conduit.
  • the top and bottom substrate/polarizer assemblies are then bonded to one another in step 1255.
  • Figure 13 discloses a method for modifying existing liquid crystal display devices.
  • the existing LCD is disassembled by removing the top substrate assembly, including the polarizer, the conductive (ITO) layer, rubbing layer and color filter (described in Figure 1). Up to two-thirds of the transistors are removed from the bottom substrate assembly, along with, optionally, the rubbing layer on that substrate, in step 1310. Light scattering material is then coated onto the interior surface of the bottom substrate, in step 1315.
  • the top substrate assembly is then reinstalled including only the polarizer, the substrate itself and the conductive (ITO) layer, and optionally the rubbing layer, in step 1320.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Liquid Crystal (AREA)
  • Illuminated Signs And Luminous Advertising (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)

Abstract

L'invention concerne un dispositif à utiliser dans un afficheur couleur à séquence de champ. Ledit dispositif peut comprendre des premier et second polariseurs, une matière de diffusion de la lumière peut être placée entre les premier et second polariseurs. De plus, l'afficheur peut comporter une source de lumière possédant différentes couleurs. Des parties de la matière de diffusion de la lumière sont utilisables pour une excitation sélectionnable. L'excitation d'une partie de la matière à diffusion de lumière est utilisable pour réguler une quantité de lumière d'une couleur parmi la pluralité de couleurs émises par le dispositif afficheur. Par ailleurs, les sous-trames à partir desquelles une trame d'image est composée peuvent être adressées de manière segmentée, chaque sous-trame comprenant plusieurs segments. La source de lumière est pulsée de ce fait de manière segmentée. Un segment donné peut être illuminé dans une couleur différente dans chaque sous-trame. Ainsi, le scintillement perçu peut être réduit.
EP03741980A 2002-06-13 2003-06-13 Dispositif afficheur a sequence de champ et ses procedes de fabrication Withdrawn EP1552358A4 (fr)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
US38823702P 2002-06-13 2002-06-13
US388237P 2002-06-13
US44305303P 2003-01-28 2003-01-28
US443053P 2003-01-28
US44630403P 2003-02-10 2003-02-10
US446304P 2003-02-10
PCT/US2003/018762 WO2003107130A2 (fr) 2002-06-13 2003-06-13 Dispositif afficheur a sequence de champ et ses procedes de fabrication

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EP1552358A2 true EP1552358A2 (fr) 2005-07-13
EP1552358A4 EP1552358A4 (fr) 2007-01-31

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JP (1) JP2005530197A (fr)
AU (1) AU2003276705A1 (fr)
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US7349043B2 (en) 2004-05-24 2008-03-25 Nec Corporation Light source, display device, portable terminal device, and ray direction switching element
JP2007322913A (ja) * 2006-06-02 2007-12-13 Vision Multimedia Technology:Kk 液晶表示装置
JP6983674B2 (ja) * 2018-01-19 2021-12-17 株式会社ジャパンディスプレイ 表示装置及び液晶表示装置

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JP2000002870A (ja) * 1998-06-16 2000-01-07 Harness Syst Tech Res Ltd 液晶表示素子

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US5751388A (en) * 1995-04-07 1998-05-12 Honeywell Inc. High efficiency polarized display
US6501521B2 (en) * 2001-03-07 2002-12-31 Sharp Kabushiki Kaisha Transmission/reflection type color liquid crystal display device

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JP2000002870A (ja) * 1998-06-16 2000-01-07 Harness Syst Tech Res Ltd 液晶表示素子

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HIDEFUME YOSHIDA ET AL: "A FULL-COLOR TFT-LCD WITH A POLYMER-DISPERSED STRUCTURE" JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY, SOCIETY FOR INFORMATION DISPLAY, SAN JOSE, US, vol. 1, no. 4, 1 December 1993 (1993-12-01), pages 417-422, XP000505595 ISSN: 1071-0922 *
PATENT ABSTRACTS OF JAPAN vol. 2000, no. 04, 31 August 2000 (2000-08-31) -& JP 2000 002870 A (HARNESS SYST TECH RES LTD; SUMITOMO WIRING SYST LTD; SUMITOMO ELECTRIC), 7 January 2000 (2000-01-07) *
See also references of WO03107130A2 *

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CA2489365A1 (fr) 2003-12-24
WO2003107130A2 (fr) 2003-12-24
EP1552358A4 (fr) 2007-01-31
JP2005530197A (ja) 2005-10-06
AU2003276705A1 (en) 2003-12-31
WO2003107130A3 (fr) 2004-03-04
AU2003276705A8 (en) 2003-12-31

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