WO1997005597A1 - Ensemble de pixels a ecran plat incorporant des commutateurs photoconducteurs - Google Patents

Ensemble de pixels a ecran plat incorporant des commutateurs photoconducteurs Download PDF

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Publication number
WO1997005597A1
WO1997005597A1 PCT/CA1995/000459 CA9500459W WO9705597A1 WO 1997005597 A1 WO1997005597 A1 WO 1997005597A1 CA 9500459 W CA9500459 W CA 9500459W WO 9705597 A1 WO9705597 A1 WO 9705597A1
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WO
WIPO (PCT)
Prior art keywords
array
photoconductive
flat panel
switches
lines
Prior art date
Application number
PCT/CA1995/000459
Other languages
English (en)
Inventor
T. Gordon Pilkington
Original Assignee
Litton Systems Canada Limited
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 Litton Systems Canada Limited filed Critical Litton Systems Canada Limited
Priority to PCT/CA1995/000459 priority Critical patent/WO1997005597A1/fr
Publication of WO1997005597A1 publication Critical patent/WO1997005597A1/fr

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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
    • G02F1/135—Liquid crystal cells structurally associated with a photoconducting or a ferro-electric layer, the properties of which can be optically or electrically varied

Definitions

  • the present invention relates to pixel arrays and in particular to a pixel array incorporating photoconductive semiconductor switches. More particularly, the present invention relates to a flat panel such as a liquid crystal display incorporating a photoconductive bus line switch array.
  • Liquid crystal display (“LCD”) panels are used in televisions and lap-top computer screens and present video information by modulating light intensity on a pixel-by- pixel basis.
  • Panels of this nature include an array of pixels arranged in rows and columns. Select lines interconnect the individual rows of the array while data lines interconnect the individual columns of the array.
  • each pixel may include a TFT switch which uses a semiconductor switch or may be of the passive ferroelectric type.
  • Each pixel has a transparent electrode constituting the output pad of the pixel.
  • the pixels and select and data lines may be fabricated on a common substrate or on separate substrates.
  • a peripheral driver is connected to the select lines on at least one side of the array to select the select lines in succession so that data may be written to a given pixel via the associated data line and onto the transparent electrode.
  • the voltage appearing on the transparent electrode modulates light via the LCD or photoemission effect.
  • the array of pixels in the flat panel is large and may include as many as one thousand (1000) select and data lines.
  • 1000 thousand
  • each select and data line must be connected to a driver, a significant number of external electrical connections must be made between the array and the peripheral driver.
  • redundant drivers the number of electrical connections is doubled. It is desired to reduce the number of such connections between the array and peripheral circuits.
  • a flat panel display comprising: an array of pixels arranged in rows and columns; a plurality of select lines, each interconnecting an individual one of one of the rows or columns of said array for supplying a bias to pixels in said individual one; a plurality of data lines, each interconnecting an individual one of the other of the rows or columns of said array for supplying a bias to pixels in said individual one; and at least one array of photoconductive switches, said at least one array of photoconductive switches being associated with one of said plurality of select or data lines, each photoconductive switch in said at least one array being connected to one of said select or data lines of said plurality, each photoconductive switch being responsive to incident radiation to allow said bias to be supplied to said select or data lines.
  • the flat panel display includes a pair of photoconductive switch arrays, one of the photoconductive switch arrays being connected between each of the select lines and a voltage bus connected to a potential voltage source to supply the bias.
  • the other photoconductive switch array is connected between each of the data lines and a voltage source to supply the bias.
  • the photoconductive switch array connected to the select lines is configured to supply bias to the select lines to allow the gray shade of the pixels to be selected from a plurality of shades. In one embodiment, this is achieved by configuring each data line as a data bus and sub-dividing each pixel into sub-pixel areas. Each sub-pixel area is connected to the voltage source via a photoconductive switch and a data line of the data bus.
  • the gray shade of a pixel can be selected by directing the incident radiation to one or more of the photoconductive switches connected to the sub-pixel areas of that pixel.
  • each pixel is connected to three potential voltage sources via a data line and three photoconductive switches.
  • the gray shade of a pixel can be selected by directing the incident radiation to one or more of the photoconductive switches to connect the pixel to one or more of the potential voltage sources.
  • each photoconductive switch in the photoconductive switch arrays includes means to accelerate the transition of the photoconductive switch to an off-state upon removal of the incident radiation.
  • the array of pixels and the photoconductive switch arrays include thin film transistors and are formed on a common substrate.
  • a passive matrix flat panel display comprising: an array of pixels arranged in rows and columns, each of said pixels for displaying a gray shade and including a pair of spaced electrodes; a plurality of select lines, each interconnecting one electrode of an individual one of one of the rows or columns of said array for supplying a bias to said one electrodes in said individual one; a plurality of data lines, each interconnecting the other electrode of an individual one of the other of the rows or columns of said array for supplying a bias to said other electrodes in said individual one; a first array of photoconductive switches, associated with said select lines, each photoconductive switch in said first array being connected to one of said select lines and being responsive to incident radiation to allow said bias to be supplied to said select lines; and a second array of photoconductive switches associated with said data lines, each photoconductive switch in said second array of photoconductive switches being connected to said data lines and being responsive to incident radiation to allow said bias to be supplied to said data lines.
  • an active matrix liquid crystal display comprising: a thin film transistor switch array arranged in rows and columns and formed on a common substrate; a plurality of gate lines formed on said substrate, each interconnecting an individual one of one of the rows or columns of said array; a plurality of source lines formed on said substrate, each interconnecting an individual one of the other of the rows or columns of said array; an array of photoconductive switches formed on said substrate, each being connected to one of said gate lines, each photoconductive switch being responsive to incident radiation to connect said gate line to a potential voltage source and select the pixels connected thereto to allow for data to be written to the selected pixels; and an optical scanning system to direct said incident radiation towards a selected photoconductive switch of said array.
  • a flat panel for radiation imaging comprising: a thin film transistor switch array arranged in rows and columns and formed on a common substrate; a plurality of gate lines formed on said substrate, each interconnecting an individual one of one of the rows or columns of said array; a plurality of source lines formed on said substrate, each interconnecting an individual one of the other of the rows or columns of said array; an array of photoconductive switches formed on said substrate, each being connected to one of said gate lines, each photoconductive switch being responsive to incident radiation to connect said gate line to a potential voltage source and select the pixels connected thereto to allow for data to be read from the selected pixels; and an optical scanning system to direct said incident radiation towards a selected photoconductive switch of said array.
  • the present invention provides advantages in that since the select and/or data lines are selected by exposing each photoconductive switch to incident radiation, the number of physical electrical connections between the array of pixels and peripheral circuitry is reduced as compared with prior art flat panels.
  • Figure 1 is a schematic of a flat panel display
  • Figure 2 is a schematic of an optical scanning system forming part of the flat panel display of Figure 1;
  • Figures 3a and 3b are top plan views of portions of the flat panel display of Figure 1;
  • Figure 4 is a cross-sectional view a photoconductive switch forming part of the flat panel display of Figure 1;
  • Figure 5 is a cross-sectional view an alternative embodiment of a photoconductive switch for a flat panel display.
  • the liquid crystal display 20 includes an LCD panel 22 constituted by an array of pixels 24 arranged in rows and columns. Each pixel 24 includes a lower electrode 24a and a transparent upper electrode 24b constituting the output pad of the pixel.
  • the pixels 24 in each row of the array are interconnected by a select line 26 while the pixels 24 in each column of the array are interconnected by data busses 28.
  • the select lines are connected to the upper electrode 24b of each pixel while the data busses are connected to the lower electrode 24a of each pixel.
  • both the upper and lower electrodes of that pixel need to be biased.
  • a photoconductive switch array 30 is connected to one side of the LCD panel 22 and supplies a bias to the select lines 26 as will be described.
  • the photoconductive switch array 30 includes an array of photoconductive switches 60 (see Figures 3a and 4) , each of which is connected to one of the select lines 26.
  • An optical scanning system 32 is associated with the photoconductive switch array 30 and directs an incident beam of radiation 34 towards the photoconductive switch array in response to input received from a control circuit 36.
  • a second photoconductive switch array 37 is connected to another side of the LCD panel 22 and supplies a bias to the data busses 28 as will be described.
  • the photoconductive switch array 37 also includes an array of photoconductive switches 60, each of which is connected to one of the data busses 28.
  • An optical scanning system 38 is associated with the photoconductive switch array 37 and directs an incident beam of radiation 39 towards photoconductive switch array 37 in response to input from the control circuit 36.
  • the optical scanning system 32 includes a shutter 40 receiving the incident beam of radiation 34.
  • the shutter 40 opens in response to gate pulses received on input line 42 from control circuit 36 to allow the incident beam of radiation to pass.
  • An optical scanner 44 receives the incident beam of radiation 34 when the shutter 40 is open.
  • the optical scanner 44 sweeps the beam of incident radiation across the photoconductive switch array 30 in response to input from control circuit 36 to turn on the photoconductive switches and thereby bias successively the select lines 26.
  • Optical scanner 44 may be of the reflective type having a moving mirror to sweep the incident beam of radiation, or of the refractive type having an optically active crystal to sweep the incident beam of radiation or may be of the electronic type such as a linear LED array similar to those used in photocopiers and facsimile machines.
  • optical scanning system 38 is basically the same as optical scanning system 30. However, in optical scanning system 38 the incident beam of radiation 39 is swept across the photoconductive switch array 37 to select the desired data busses 28 to allow data to be written to pixels 24 that have also been selected via the select lines 26.
  • FIG. 3a best illustrates the photoconductive switch array 30 and as can be seen, the photoconductive switch array is connected between the select lines 26 and a voltage bus 50.
  • the voltage bus 50 leads to a positive potential voltage source V PP .
  • An accelerate bus 52 is also connected to the photoconductive switch array 30 and leads to a control voltage V cc .
  • Each photoconductive switch 60 in the array 30 is connected to one of the select lines 26 and to the voltage and accelerate busses 50 and 52 respectively.
  • the photoconductive switch array 37 is better illustrated. As can be seen, the photoconductive switch array 37 is connected between the data busses 28 and a voltage bus 56 leading to a potential voltage source V ⁇ . An accelerate bus 58 is also connected to the photoconductive switch array 37 and leads to the control voltage Vcc.
  • Four photoconductive switches 60 in the array 37 are associated with the pixels 24 of each column and are connected to the data bus 28 extending to that column as well as to the voltage bus 56.
  • One of the pixels 24 is shown divided into four weighted sub-pixel areas 25a to 25d. By selecting one or more of the sub- pixel areas by activating one or more of the photoconductive switches 60 connected to that pixel via the data bus 28, the pixel 24 can be illuminated to different gray shades.
  • Each photoconductive switch 60 is in the form of a thin film transistor allowing the photoconductive switches of the arrays 30 and 37 to be fabricated on a common substrate 29.
  • the accelerate bus 52 or 58 passes beneath the photoconductive switch 60 and is covered by a dielectric layer 62 formed of Si0 2 .
  • a photoconductive semiconductor material film 64 formed of CdSe is deposited on the dielectric layer 62. The photoconductive semiconductor material film 64 contacts both the voltage bus 50 or 56 and the select line 26 or a data line of data bus 28 and establishes an electrical connection between the voltage bus and the select or data line upon exposure to incident radiation.
  • the select line 26 connected to that particular pixel must be selected.
  • the control circuit 36 provides input to the shutter 40 as well as to the optical scanner 44 so that the incident beam of radiation 34 passes through the shutter and is directed by the optical scanner to the photoconductive switch 60 of the photoconductive switch array 30 connected to the appropriate select line 26.
  • the photoconductive semiconductor material film 64 Upon exposure to incident radiation, the photoconductive semiconductor material film 64 establishes an electrical connection between the voltage bus 50 and the select line 26. Since the voltage bus 50 is connected to the positive potential voltage source V PP , the select line 26 becomes biased to a high potential. The bias on the select line 26 is applied to the lower electrode of each pixel 24 connected to the select line. Once the lower electrodes are biased, data can be written to any of these selected pixels 24. This is achieved by causing the optical scanning system 38 to direct the incident beam of radiation 39 to the appropriate photoconductive switches 60 associated with the selected pixels. When this occurs, the voltage source V ⁇ is connected to one or more of the upper electrodes of the sub-pixel areas of the selected pixels via the lines of the data bus 28. The optical scanning system 38 and the photoconductive switches 60 of array 37 operate in a similar manner as array 30 and optical scanning system 32.
  • the photoconductive switches 60 connected to that select line and data bus must be isolated from the incident beam of radiation 34 and 39. This can be achieved by closing the shutter 40 or causing the optical scanner 44 to direct the incident beams of radiation 34 and 39 to other photoconductive switches 60. Once the photoconductive switches have been isolated from the incident beam of radiation, the photoconductive switches 60 become conditioned to an off-state to isolate the voltage busses 50 and 56 from the select line 26 and data bus 28. In order to accelerate the transition of the photoconductive switches 60 from the on-state to the off- state, a potential is applied to the accelerate busses 52 and 56. The potential on the accelerate busses speeds up this process by forcing a depletion of current carriers in the semiconductor material of the photoconductive switches 60 rather than relying on natural recombination of current carriers.
  • FIG. 5 shows a conventional photoconductive switch 70.
  • photoconductive switch includes a photoconductive semiconductor material film 72 which contacts both the voltage bus and the select line or data bus and establishes an electrical connection between the voltage bus and the select line or data bus upon exposure of the photoconductive switch to incident radiation. If photoconductive switches 70 of this type are used in the array, no accelerate bus 52 is required.
  • the photoconductive switch array includes three rows 37a, 37b and 37c of photoconductive switches 60.
  • the photoconductive switches in each row of the array are associated with one data line 28.
  • the first row of photoconductive switches is connected between a high potential data bus V ⁇ , and the data lines 28.
  • the second row of photoconductive switches is connected between a medium potential data bus V M *. and the data lines 28.
  • the third row of photoconductive switches is connected between a low potential data bus V LP and the data lines 28.
  • the optical scanning system 38 is conditioned by control circuit 36 to direct an incident beam of radiation 39 to one or more of the photoconductive switches 60 connecting that pixel to the three voltage buses.
  • the potential voltage buses Vm*, V M *. and V-j connected to the pixel 24 through the data line, will determine the gray shade of the pixel.
  • the liquid crystal display has been described as including a pair of photoconductive switch arrays, it should be apparent to those of skill in the art that the liquid crystal display need only include one photoconductive switch array associated with either the data or select lines.
  • the photoconductive switch array is associated with the select lines, either type of photoconductive switch 60 or 70 is suitable since turn-off speed of the conventional photoconductive switches is satisfactory.
  • the photoconductive switch array is associated with the data lines, it is preferred that the array includes photoconductive switches 60 since fast turn- off speed is important for desired results.
  • the photoconductive switch arrays can also be used in other applications such as in an active matrix
  • LCD passive matrix LCD
  • plasma display
  • the photoconductive switches 60 can be formed on the substrate simultaneously with the pixels 24.
  • the photoconductive switch arrays may also be used in a flat panel for radiation imaging including a TFT switch array.
  • a photoconductive switch array would be connected to the gate lines of the array to allow the gate lines to be selected by directing an incident beam of radiation to the photoconductive switches in the array.
  • the data stored by the pixels connected to that gate line which represents the exposure of the pixels to radiation, can be read via the source lines.
  • each row of pixels can be selected successively while avoiding the need for electrical connections between each select and data line and a peripheral circuit.

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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)

Abstract

Ecran plat, tel qu'un écran à cristaux liquides (20), comprenant un ensemble de pixels (24) disposés en rangées et en colonnes. Une ligne de sélection (26) interconnecte chacune des rangées de l'ensemble, tandis qu'une ligne de données (28) interconnecte chacune des colonnes de l'ensemble. Une série (30) de commutateurs photoconducteurs (60) est branchée entre chaque ligne de sélection (26) et un bus de tension (50) lui-même branché sur une source de tension potentielle (VPP). Une série (37) de commutateurs photoconducteurs (60) est branchée entre chaque ligne de données (28) et un bus de tension (56) branché lui-même sur une source de tension potentielle (VSS). Chaque commutateur photoconducteur (60) réagit à un rayonnement incident (34, 39) en connectant les lignes de sélection et les lignes de données au bus de tension et en excitant les pixels en données d'affichage.
PCT/CA1995/000459 1995-07-31 1995-07-31 Ensemble de pixels a ecran plat incorporant des commutateurs photoconducteurs WO1997005597A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/CA1995/000459 WO1997005597A1 (fr) 1995-07-31 1995-07-31 Ensemble de pixels a ecran plat incorporant des commutateurs photoconducteurs

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CA1995/000459 WO1997005597A1 (fr) 1995-07-31 1995-07-31 Ensemble de pixels a ecran plat incorporant des commutateurs photoconducteurs

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WO1997005597A1 true WO1997005597A1 (fr) 1997-02-13

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU768515B2 (en) * 1999-01-13 2003-12-18 Igeneon Krebs-Immuntherapie Forschungs- Und Entwicklungs-Ag Use of antibodies for anticancer vaccination
US7542178B2 (en) 2003-01-21 2009-06-02 Hewlett-Packard Development Company, L.P. Electronic device display and document scanner

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4952031A (en) * 1987-06-19 1990-08-28 Victor Company Of Japan, Ltd. Liquid crystal display device
JPH06138437A (ja) * 1992-10-23 1994-05-20 Pioneer Electron Corp 線順次駆動型光導電型液晶ライトバルブ表示装置
EP0633542A2 (fr) * 1993-07-05 1995-01-11 Philips Electronics Uk Limited Dispositif électro-optique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4952031A (en) * 1987-06-19 1990-08-28 Victor Company Of Japan, Ltd. Liquid crystal display device
JPH06138437A (ja) * 1992-10-23 1994-05-20 Pioneer Electron Corp 線順次駆動型光導電型液晶ライトバルブ表示装置
EP0633542A2 (fr) * 1993-07-05 1995-01-11 Philips Electronics Uk Limited Dispositif électro-optique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 18, no. 439 (P - 1787) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU768515B2 (en) * 1999-01-13 2003-12-18 Igeneon Krebs-Immuntherapie Forschungs- Und Entwicklungs-Ag Use of antibodies for anticancer vaccination
US7542178B2 (en) 2003-01-21 2009-06-02 Hewlett-Packard Development Company, L.P. Electronic device display and document scanner

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