EP0221582A2 - Circuit de commande d'un dispositif d'affichage à cristaux liquides - Google Patents

Circuit de commande d'un dispositif d'affichage à cristaux liquides Download PDF

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Publication number
EP0221582A2
EP0221582A2 EP86201631A EP86201631A EP0221582A2 EP 0221582 A2 EP0221582 A2 EP 0221582A2 EP 86201631 A EP86201631 A EP 86201631A EP 86201631 A EP86201631 A EP 86201631A EP 0221582 A2 EP0221582 A2 EP 0221582A2
Authority
EP
European Patent Office
Prior art keywords
control circuit
crystal display
liquid crystal
display unit
circuit according
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Withdrawn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
EP86201631A
Other languages
German (de)
English (en)
Other versions
EP0221582A3 (fr
Inventor
Eckhard Dipl.-Ing. Walters
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.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Corporate Intellectual Property GmbH
Philips Patentverwaltung GmbH
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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 Philips Corporate Intellectual Property GmbH, Philips Patentverwaltung GmbH, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Corporate Intellectual Property GmbH
Publication of EP0221582A2 publication Critical patent/EP0221582A2/fr
Publication of EP0221582A3 publication Critical patent/EP0221582A3/fr
Withdrawn legal-status Critical Current

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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
    • G09G3/04—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of a single character by selection from a plurality of characters, or by composing the character by combination of individual elements, e.g. segments using a combination of such display devices for composing words, rows or the like, in a frame with fixed character positions
    • G09G3/16—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of a single character by selection from a plurality of characters, or by composing the character by combination of individual elements, e.g. segments using a combination of such display devices for composing words, rows or the like, in a frame with fixed character positions by control of light from an independent source
    • G09G3/18—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of a single character by selection from a plurality of characters, or by composing the character by combination of individual elements, e.g. segments using a combination of such display devices for composing words, rows or the like, in a frame with fixed character positions by control of light from an independent source using liquid crystals

Definitions

  • the invention relates to a control circuit for a liquid crystal display unit, which is installed in particular in a telecommunications device, according to the preamble of patent claim 1.
  • Liquid crystal display units have so far been used with preference in quartz watches and pocket calculators. Since liquid crystal display units allow almost powerless operation and therefore only require a low power supply, they are increasingly being used in telecommunications equipment.
  • So-called "twisted nematic liquid crystals” are located in liquid crystal display units between a front and rear polarization layer.
  • the molecules of the mesogenic compounds are elongated and the longitudinal axes of the molecules are parallel in the nematic phase, apart from thermal fluctuations.
  • So-called Frédericksz transitions take place under the influence of an electric field applied to the liquid crystal, so that the initially opaque liquid becomes transparent with a suitable arrangement with polarizers.
  • the direction of the axes of each molecular layer is twisted by a small angle with respect to the neighboring molecular layer. Strikes the twisted-planar liquid crystal layer light, which polarizes linearly on the entrance side in the direction of the middle direction is the longitudinal axes of the molecules, the polarization plane with the screw-like structure of the molecular layers rotates in the layer. If the polarization direction of the rear polarizer is the same as the central direction of the longitudinal axes of the molecules, then appropriately polarized light can enter the liquid crystal display unit and is rotated in accordance with the twisting of the twisted planar layers.
  • the light (illumination by daylight or lamp) enters with horizontal polarization on the back, this is vertically polarized when exiting the liquid crystal layer. If the polarizer on the front is also oriented vertically, the light passes through it unhindered and the image surface appears bright to the viewer.
  • the liquid crystal layer is embedded between rear and front plates (and between a seal running between the glass plates), which are provided with transparent electrodes.
  • a voltage is applied to the two electrodes, the liquid crystal layer is exposed to an electric field, which causes all molecular layers to be aligned in the field direction, as a result of which the twisting in the liquid crystal layer and thus the rotation of the polarization direction of the light passing through are eliminated.
  • a matrix display is often used to display characters, graphics and images, i.e. a display with horizontally and vertically mutually parallel picture elements used.
  • the segment display e.g. 7-segment display, used.
  • a control circuit is connected to the liquid crystal display unit for addressing or selecting the picture elements and for controlling their brightness.
  • Pulse amplitude modulation is often used to control the brightness of the picture elements, i.e. the amplitude of the drive pulses determines the light transmission and thus the brightness of the picture element.
  • a multiplex control with a high multiplex ratio (e.g. 1: 8)
  • the row and column electrodes are driven with short pulses, the difference in voltage amplitude between the voltage of the switched on and off segments (or pixels) decreasing with increasing multiplex ratio, so that results in a low contrast ratio of the liquid crystal display unit.
  • An isocontrast characteristic curve is a line in a polar diagram which indicates the direction in space and to which the contrast of the liquid crystal display unit has a constant value.
  • the contrast ratio changes depending on the position of the liquid crystal display unit (expressed by the angles alpha and phi).
  • the transmissive display unit has a light-guiding body on the back, which can be used for optional introduction the ambient light or the light of a light source is designed to be movable into the liquid crystal layer.
  • the light source In the day position, the light source is switched off and the daylight is bundled by means of a lens and illuminates the light-guiding body.
  • the light-guiding body has a reflective coating on the back, as a result of which the incident daylight illuminates the liquid crystal layer from the back.
  • the light-guiding body rests on the back of the liquid crystal display unit and the light source is switched on.
  • the light reflected by the reflective coating of the light-guiding body is used to illuminate the liquid crystal display unit.
  • the brightness of the liquid crystal display device known from DE-PS 30 29 122 is controlled by the brightness of the ambient light or the light output of the light source. These values are chosen so that the information is clearly recognizable within a given observation angle range.
  • the invention is based on the object of designing a control circuit for a liquid crystal display unit in such a way that, even when the position of the liquid crystal display unit installed in a device is changed, the recognizability of the information displayed is still ensured.
  • control circuit according to the invention automatically changes the contrast when the position of the device changes also ensures that the recognizability of the information is also ensured for the new observation angle range.
  • contrast is the quotient of the difference and the sum of the luminance of to understand the light and dark part (on and off segments) of the display area.
  • the two voltage values are preferably generated by means of a switchable voltage divider circuit.
  • the switching outlay for switching over the voltage divider circuit is particularly low if, according to claim 4, the fork switch contact or, according to claim 5, a position sensor is used.
  • the switchover is additionally made dependent on a control signal from a control device arranged in the communications technology device, the customer's request can also be met for assembly locations where a change in the contrast is not desired.
  • Static, unmultiplexed liquid crystal display units are operated, for example, with a level of ⁇ 5 V AC voltage (approx. 100 Hz) with activated segments, the level of the "off" segments being 0 V.
  • the drive voltages of the multiplexed liquid crystal display unit must now be set so that the "off" segments or points are barely visible under the chosen observation angle.
  • the ratio of the drive levels of the segments is determined by the multiplex ratio, the absolute values of the voltages V on and V off depend on the solid angle.
  • a control circuit S which electrically drives each segment of the liquid crystal display unit LCD is connected to a liquid crystal display unit LCD.
  • the control circuit S generates two different voltage values for a multiplex control MA connected to the display electrodes of the liquid crystal display unit LCD for two predefinable positions of the device.
  • the control circuit S has a switchable voltage divider circuit ST for generating the two voltage values.
  • the switchable voltage divider circuit ST contains a voltage divider connected to the two connection terminals A1, A2 of a supply voltage with the resistors R1, R2, a resistor R21 connected to the tap A of the voltage divider and a fork switch contact g connected to its second connection.
  • a dark field is used for the aforementioned application display, ie a display in which the information is provided with light characters on a dark background, is preferred.
  • the control circuit S described above is supplemented with an AND gate U.
  • the output of the AND gate U is connected to the second terminal of the resistor R21.
  • the first input of the AND gate U is connected via the fork switch contact g to the connection terminal A1 and the second input of the AND gate U is supplied with a control signal STS of a control device arranged in the communications technology device.
  • the control signal STS can now be used to prevent the contrast from being switched when the position of the handset changes.

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)
  • Liquid Crystal (AREA)
  • Mobile Radio Communication Systems (AREA)
EP86201631A 1985-09-28 1986-09-23 Circuit de commande d'un dispositif d'affichage à cristaux liquides Withdrawn EP0221582A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19853534703 DE3534703A1 (de) 1985-09-28 1985-09-28 Steuerschaltung fuer eine fluessigkristall-anzeigeeinheit
DE3534703 1985-09-28

Publications (2)

Publication Number Publication Date
EP0221582A2 true EP0221582A2 (fr) 1987-05-13
EP0221582A3 EP0221582A3 (fr) 1988-09-28

Family

ID=6282247

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86201631A Withdrawn EP0221582A3 (fr) 1985-09-28 1986-09-23 Circuit de commande d'un dispositif d'affichage à cristaux liquides

Country Status (5)

Country Link
US (1) US4832454A (fr)
EP (1) EP0221582A3 (fr)
JP (1) JPS6281628A (fr)
DE (1) DE3534703A1 (fr)
DK (1) DK458086A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0272018A2 (fr) * 1986-12-04 1988-06-22 Sony Corporation Appareil d'affichage à cristaux liquides
EP0329399A2 (fr) * 1988-02-16 1989-08-23 Nec Corporation Equipement de petite dimension avec un affichage à cristaux liquides
WO1995027973A1 (fr) * 1994-04-07 1995-10-19 The Boeing Company Systeme d'affichage permettant a plusieurs utilisateurs de voir un meme ecran ou a un seul, d'en voir plusieurs

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5835074A (en) * 1992-12-30 1998-11-10 Advanced Displays Corporation Method to change the viewing angle in a fixed liquid crystal display by changing the pre-tilt angle in the liquid crystal layer with a bias voltage
US6646626B1 (en) * 1999-11-01 2003-11-11 Motorola, Inc. Method and apparatus for automatic viewing angle adjustment for liquid crystal display
KR100729762B1 (ko) * 2000-11-14 2007-06-20 삼성전자주식회사 측면 대비비 및 측면 색재현성을 향상시킨 액정 표시 장치
US7116287B2 (en) * 2001-05-09 2006-10-03 Eastman Kodak Company Drive for cholesteric liquid crystal displays
US10068512B2 (en) * 2015-07-07 2018-09-04 Texas Instruments Incorporated Modulator for a MUX LCD

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2621577A1 (de) * 1975-05-14 1976-12-16 Sharp Kk Schaltung zur bereitstellung der zur steuerung einer fluessigkristall-wiedergabeanordnung erforderlichen spannungen
DE2846874A1 (de) * 1977-10-31 1979-05-03 Sharp Kk Verfahren und schaltungsanordnung zur ansteuerung eines fluessigkristall-anzeigefelds mit ansteuerelektroden in xy-matrixanordnung
US4168498A (en) * 1975-11-04 1979-09-18 Kabushiki Kaisha Suwa Seikosha Digital display drive and voltage divider circuit
DE3024530A1 (de) * 1980-06-28 1982-01-28 Eurosil GmbH, 8000 München Fluessigkristall-steuerspannungsschaltung
EP0184762A2 (fr) * 1984-12-13 1986-06-18 Blaupunkt-Werke GmbH Méthode et dispositif de commande d'un dispositif d'affichage à cristaux liquides

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54126497A (en) * 1978-03-24 1979-10-01 Sharp Corp Dap-type liquid crystal display device
US4236150A (en) * 1978-10-18 1980-11-25 Minnesota Mining And Manufacturing Company Liquid crystal display system
JPS5622468A (en) * 1979-08-01 1981-03-03 Nissan Motor Liquid crystal display unit
US4462027A (en) * 1980-02-15 1984-07-24 Texas Instruments Incorporated System and method for improving the multiplexing capability of a liquid crystal display and providing temperature compensation therefor
CH632368B (fr) * 1980-12-19 Asulab Sa Cellule d'affichage a cristaux liquides.
JPH0654960B2 (ja) * 1983-10-20 1994-07-20 シチズン時計株式会社 液晶表示装置の駆動方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2621577A1 (de) * 1975-05-14 1976-12-16 Sharp Kk Schaltung zur bereitstellung der zur steuerung einer fluessigkristall-wiedergabeanordnung erforderlichen spannungen
US4168498A (en) * 1975-11-04 1979-09-18 Kabushiki Kaisha Suwa Seikosha Digital display drive and voltage divider circuit
DE2846874A1 (de) * 1977-10-31 1979-05-03 Sharp Kk Verfahren und schaltungsanordnung zur ansteuerung eines fluessigkristall-anzeigefelds mit ansteuerelektroden in xy-matrixanordnung
DE3024530A1 (de) * 1980-06-28 1982-01-28 Eurosil GmbH, 8000 München Fluessigkristall-steuerspannungsschaltung
EP0184762A2 (fr) * 1984-12-13 1986-06-18 Blaupunkt-Werke GmbH Méthode et dispositif de commande d'un dispositif d'affichage à cristaux liquides

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
NEUES AUS DER TECHNIK, Nr. 2, 15 April 1981, Seite 1, W}rzburg, DE; "Fl}ssigkristall-Wiedergabeanordnung" *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0272018A2 (fr) * 1986-12-04 1988-06-22 Sony Corporation Appareil d'affichage à cristaux liquides
EP0272018A3 (en) * 1986-12-04 1990-04-11 Sony Corporation Liquid crystal display apparatus
EP0329399A2 (fr) * 1988-02-16 1989-08-23 Nec Corporation Equipement de petite dimension avec un affichage à cristaux liquides
EP0329399A3 (fr) * 1988-02-16 1991-05-22 Nec Corporation Equipement de petite dimension avec un affichage à cristaux liquides
WO1995027973A1 (fr) * 1994-04-07 1995-10-19 The Boeing Company Systeme d'affichage permettant a plusieurs utilisateurs de voir un meme ecran ou a un seul, d'en voir plusieurs

Also Published As

Publication number Publication date
JPS6281628A (ja) 1987-04-15
EP0221582A3 (fr) 1988-09-28
DK458086D0 (da) 1986-09-25
US4832454A (en) 1989-05-23
DK458086A (da) 1987-03-29
DE3534703A1 (de) 1987-04-09

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