WO1999066487A1 - Procede et appareil pour exciter un dispositif d'affichage couleur a sequence de trames et cristaux liquides anti-ferroelectriques par inversion de polarite - Google Patents

Procede et appareil pour exciter un dispositif d'affichage couleur a sequence de trames et cristaux liquides anti-ferroelectriques par inversion de polarite Download PDF

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Publication number
WO1999066487A1
WO1999066487A1 PCT/GB1999/001618 GB9901618W WO9966487A1 WO 1999066487 A1 WO1999066487 A1 WO 1999066487A1 GB 9901618 W GB9901618 W GB 9901618W WO 9966487 A1 WO9966487 A1 WO 9966487A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage pulse
polarity
applying
pixels
liquid crystal
Prior art date
Application number
PCT/GB1999/001618
Other languages
English (en)
Inventor
Paul William Herbert Surguy
Original Assignee
Central Research Laboratories 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 Central Research Laboratories Limited filed Critical Central Research Laboratories Limited
Publication of WO1999066487A1 publication Critical patent/WO1999066487A1/fr

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Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3622—Control of matrices with row and column drivers using a passive matrix
    • G09G3/3629—Control of matrices with row and column drivers using a passive matrix using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
    • G09G3/3633—Control of matrices with row and column drivers using a passive matrix using liquid crystals having memory effects, e.g. ferroelectric liquid crystals with transmission/voltage characteristic comprising multiple loops, e.g. antiferroelectric liquid crystals
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0235—Field-sequential colour display
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3614—Control of polarity reversal in general

Definitions

  • the present invention relates to a method of, and apparatus for, driving a liquid crystal
  • LCD liquid crystal display
  • Liquid crystal, silicon back-plane devices are electro-optic
  • driver which is a type of control device and operates a plurality of switches.
  • the switches are arranged to switch region of the liquid crystal material from one state to
  • the driver selectively switches
  • AFLCs anti-ferroelectric liquid crystals
  • Anti-ferroelectric liquid crystals have an electro-optical response which is shown by the graph in Figure 1.
  • AFLCs anti-ferroelectric liquid crystal materials
  • the electro-optic response of AFLCs is only approximately symmetric about a zero applied voltage and therefore is not truly polarity insensitive. That is when a voltage +V volts is applied the transmission of an AFLC device is Ti. However, if an opposite polarity voltage, (i.e. -V volts is applied), then the transmission of the device is different namely T 2 .
  • UK Patent Application No 2173 629 discloses a driving sequence which employs a strobe type unipolar pulse sequence which combines with a sequence of bipolar pulses. The polarity of strobe pulses is reversed in order to maintain change of balance.
  • This switching sequence would not be suitable for anti-ferroelectric liquid crystal (AFLC) material because they exhibit different properties according to the applied voltage polarity. As there is no reference to colour switching it is assumed that the sequence is only suitable for monochrome devices.
  • AFLC anti-ferroelectric liquid crystal
  • Such a device may be a silicon backplane device and has three separate colour fields, namely: red (R), green (G) and blue (B). Information about the colour of an image is written to each of the appropriate fields sequentially.
  • RGB red
  • G green
  • B blue
  • An advantage of colour sequential LCDs is that the number of pixels required in a display is reduced by a factor of 3 compared to a colour filter display.
  • colour sequential liquid crystal display devices colour is introduced into an image by field sequential reflection or transmission from three different light sources namely red, green or blue.
  • a colour sequential device is preferred over using three separate colour filters because in smaller devices it is extremely difficult (and therefore expensive) to produce different colour pixels on this scale. This makes colour sequential displays cheaper and easier to manufacture, because there are no colour filters.
  • a method of driving a liquid crystal display device comprising the steps of: applying a first voltage pulse, of a first polarity, to a first group of pixels; subsequently applying a second voltage pulse, of opposite polarity to the first voltage pulse, to a second group of pixels; subsequently applying a third voltage pulse of identical polarity to the first voltage pulse, to a third group of pixels; subsequently applying a fourth voltage pulse, of opposite polarity to the first voltage pulse, to the second group of pixels thereby achieving a desired grey level; and repeating the sequence of voltage pulse application so that voltage pulses of the same polarity are always applied to the same group of pixels and thereby obtaining direct current (dc) charge balancing for the device.
  • dc direct current
  • a method of driving a liquid crystal display device comprising the steps of: in a first time interval applying a first voltage pulse, of a first polarity to a first colour display driver; in a subsequent time interval applying a voltage pulse of opposite polarity to the first voltage pulse, to a second colour display driver; in a subsequent time interval applying a voltage pulse of identical polarity to the first pulse, to a third colour display driver; and in a subsequent time interval applying a voltage pulse of identical polarity to the second voltage pulse to said second display driver, then repeating the pulse application sequence so that regions of pixels are illuminated during adjacent time intervals, with reversing polarities, thereby achieving direct current (dc) charge balancing.
  • the liquid crystal display device includes an anti-ferro-electric liquid crystal material (AFLCD).
  • red (R) and blue (B) fields are addressed with the first polarity voltage pulses and the green (G) field is addressed with the second polarity voltage pulses.
  • G green
  • the overall result is that, in any given time period (that is during a plurality of adjacent time intervals), a green field is always addressed before and after a blue field is addressed and a green field is always addressed before and after a red field is addressed.
  • a red field is never addressed immediately before or immediately after a blue field is addressed. Instead there is always an intervening green field which is addressed.
  • Corresponding apparatus is provided in accordance with the aforementioned statements of invention.
  • the apparatus is supported on a silicon back plane device.
  • drive c means is integrated into the device.
  • the drive? means (or driver) for the green light source is always of a slightly lower amplitude than that for the red and blue drivers means.
  • the eye is more sensitive to green light it would appear to be intuitive to use one of the other colours as the colour which is addressed most often.
  • a brighter display results from using green as the most frequently addressed colour with less energy consumption.
  • alternative colour sequences may be used.
  • an alternative sequence may be: red, green, red, blue, red, green, red, blue.
  • the sequence repeats itself after 6N adjacent time intervalswhere N is any positive whole number, and preferably 1.
  • the colour sequence may then change so that alternate interlacing patterns may be used.
  • the overall frame time is 4/3 faster than before and consequently does not place such a great demand upon electronic processing.
  • Previously drivers had to operate at twice the speed in order to achieve direct current (dc) balancing and avoid flicker.
  • Figure 1 shows a graph of AFLCD transmission characteristics between positive and negative pulses
  • Figure 2 shows an example of a sequence of illumination fields used in the prior art
  • Figure 3 shows diagrammatically how alternate voltage polarities are applied to the sequence of illumination of fields in Figure 2;
  • Figure 4 shows diagramatically how flicker arises in a prior art display as a result of asymmetry in optical response characteristics of certain liquid crystals;
  • Figure 5 shows an example of a colour field sequence according to the present invention
  • Figure 6 shows diagrammatically how alternate voltage polarities are applied to the sequence of colour fields in Figure 5;
  • Figure 7 shows overall optical output obtained when combining the sequences in Figures 5 and 6;
  • Figure 8 is a sketch of a block diagram of one example of an apparatus according to the present invention.
  • Figure 1 a graph of the response of a liquid crystal material having asymmetry in transmission between positive and negative voltage pulses.
  • This asymmetry occurs in certain anisotropic materials such as anti- ferroelectric liquid crystals (AFLC).
  • AFLC anti- ferroelectric liquid crystals
  • “Flicker” arises as a result of the addressing sequence of alternate colour fields.
  • An example of such a sequence is shown diagrammatically with reference to Figures 2, 3 and 4.
  • “flicker” occurs as a result of combining dc balancing with alternating colour fields. Colour fields red, green and blue are addressed, always in that order, but with alternate polarity voltage pulses, (shown diagrammatically in Figure 3).
  • Figure 4 shows diagrammatically how "flicker” arises when alternating polarity pulses of ( Figure 3) are used to drive a display illuminated by a colour field sequence, for example of the type shown in Figure 2.
  • the invention overcomes the problem of d.c. charge balancing by adopting a different sequence of addressing colour drivers. This is achieved in a preferred embodiment by using a different sequence of address pulses.
  • the resultant pulse train is described briefly with reference to Figures 5 to 7. The following notation is used: a "plus” (+) indicates a positive applied voltage and a "minus” (-) indicates a negative applied voltage.
  • a "plus" (+) indicates a positive applied voltage
  • a "minus" (-) indicates a negative applied voltage.
  • a display controller 10 which combines a polarity signal from a polarity selector 12, with picture data from picture data source 14. This forms a train of pulses similar to that depicted in Figure 6. Controller 10 then sequentially switches respective pulses to one of three different colour light sources 16, 18 or 20.
  • Light source 16 is for a red field
  • light source 18 is for a green field
  • light source 20 is for a blue field.
  • Illumination optics 22 couple light from sources 16, 18 and 20 to a display 24.
  • the combination of light source and display controller may also be referred to as drive means or driver. These light sources illuminate selectively groups of pixels, as is known in the art, and thereby define an image (not shown).
  • the device 10 may be supported on a silicon back plane device.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Liquid Crystal (AREA)

Abstract

L'invention concerne un procédé et un appareil qui servent à exciter un dispositif d'affichage à cristaux liquides incorporant des cristaux liquides anti-ferroélectriques (AFLCD). Une séquence de commutation est mise en oeuvre pour adresser tous les champs de couleurs selon une séquence du type rouge, vert, bleu, vert, rouge, vert, bleu, etc., par inversion de polarité, ce qui permet d'obtenir un équilibrage de charge. De plus, le papillotement dû à l'asymétrie de la courbe des caractéristiques de transmission des AFLCD est évité, sans doublage de la vitesse de commutation, étant donné que chaque champ est toujours adressé au moyen d'une tension ayant la même polarité (p. ex. rouge toujours positif, vert toujours négatif, etc.).
PCT/GB1999/001618 1998-06-18 1999-05-21 Procede et appareil pour exciter un dispositif d'affichage couleur a sequence de trames et cristaux liquides anti-ferroelectriques par inversion de polarite WO1999066487A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9813226.9A GB9813226D0 (en) 1998-06-18 1998-06-18 Method of,and apparatus for, driving a liquid crystal display device
GB9813226.9 1998-06-18

Publications (1)

Publication Number Publication Date
WO1999066487A1 true WO1999066487A1 (fr) 1999-12-23

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/001618 WO1999066487A1 (fr) 1998-06-18 1999-05-21 Procede et appareil pour exciter un dispositif d'affichage couleur a sequence de trames et cristaux liquides anti-ferroelectriques par inversion de polarite

Country Status (3)

Country Link
GB (1) GB9813226D0 (fr)
TW (1) TW455830B (fr)
WO (1) WO1999066487A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1180714A1 (fr) * 2000-03-27 2002-02-20 Citizen Watch Co. Ltd. Obturateur cristaux liquides

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5113274A (en) * 1988-06-13 1992-05-12 Mitsubishi Denki Kabushiki Kaisha Matrix-type color liquid crystal display device
US5461503A (en) * 1993-04-08 1995-10-24 Societe D'applications Generales D'electricite Et De Mecanique Sagem Color matrix display unit with double pixel area for red and blue pixels
EP0875881A2 (fr) * 1997-04-30 1998-11-04 SHARP Corporation Modulateurs de lumière à matrice active, utilisation d'un modulateur de lumière à matrice active, et dispositif d'affichage

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5113274A (en) * 1988-06-13 1992-05-12 Mitsubishi Denki Kabushiki Kaisha Matrix-type color liquid crystal display device
US5461503A (en) * 1993-04-08 1995-10-24 Societe D'applications Generales D'electricite Et De Mecanique Sagem Color matrix display unit with double pixel area for red and blue pixels
EP0875881A2 (fr) * 1997-04-30 1998-11-04 SHARP Corporation Modulateurs de lumière à matrice active, utilisation d'un modulateur de lumière à matrice active, et dispositif d'affichage

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1180714A1 (fr) * 2000-03-27 2002-02-20 Citizen Watch Co. Ltd. Obturateur cristaux liquides
EP1180714A4 (fr) * 2000-03-27 2002-10-02 Citizen Watch Co Ltd Obturateur cristaux liquides
US6804029B2 (en) 2000-03-27 2004-10-12 Citizen Watch Co., Ltd. Liquid crystal shutter

Also Published As

Publication number Publication date
TW455830B (en) 2001-09-21
GB9813226D0 (en) 1998-08-19

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