EP0561135A2 - Verfahren zur Ansteuerung von bistabilen, insbesondere ferroelektrischen Flüssigkristalldisplays - Google Patents

Verfahren zur Ansteuerung von bistabilen, insbesondere ferroelektrischen Flüssigkristalldisplays Download PDF

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Publication number
EP0561135A2
EP0561135A2 EP93101638A EP93101638A EP0561135A2 EP 0561135 A2 EP0561135 A2 EP 0561135A2 EP 93101638 A EP93101638 A EP 93101638A EP 93101638 A EP93101638 A EP 93101638A EP 0561135 A2 EP0561135 A2 EP 0561135A2
Authority
EP
European Patent Office
Prior art keywords
pulses
pulse
column
line
time
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Withdrawn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
EP93101638A
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German (de)
English (en)
French (fr)
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EP0561135A3 (enrdf_load_stackoverflow
Inventor
Claus Dr. Escher
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.)
Hoechst AG
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Hoechst AG
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 Hoechst AG filed Critical Hoechst AG
Publication of EP0561135A2 publication Critical patent/EP0561135A2/de
Publication of EP0561135A3 publication Critical patent/EP0561135A3/xx
Withdrawn legal-status Critical Current

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    • 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
    • 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
    • G09G2310/0202—Addressing of scan or signal lines
    • G09G2310/0205—Simultaneous scanning of several lines in flat panels
    • 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
    • G09G2310/06—Details of flat display driving waveforms
    • 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
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/066—Adjustment of display parameters for control of contrast

Definitions

  • the present invention relates to a liquid crystal switching and display device (display) with a special electrical control scheme, which leads to a high contrast and in particular to short switching times.
  • FLC light valves Ferroelectric liquid crystal mixtures
  • Examples are the well-known clock and calculator displays or liquid crystal displays in the OA (office automation) or TV (television) area. However, this also includes optical closures, so-called "light shutters", as used for. B. in copiers, printers, etc. are used.
  • spatial light modulators also belong to the field of application of liquid crystal light valves (see Liquid Crystal Device Handbook, Nikkan Kogyo Shimbun, Tokyo, 1989; ISBN 4-526-02590-9C 3054 and the works cited therein).
  • the electro-optical switching and display devices are constructed in such a way that the FLC layer is enclosed on both sides by layers which usually, in this order starting from the FLC layer, have at least one orientation layer, electrodes and a boundary plate (e.g. made of glass). are. They also contain a polarizer if they are operated in "guest-host” or reflective mode, or two polarizers if transmissive birefringence ("birefringence mode") is used as the mode.
  • the switching and display elements can optionally further auxiliary layers, such as. B. Diffusion barrier or insulation layers included.
  • Such orientation layers together with a sufficiently small spacing of the boundary disks, bring the FLC molecules of the FLC mixture into a configuration in which the molecules lie with their longitudinal axes parallel to one another and the smectic planes are arranged perpendicular or obliquely to the orientation layer.
  • the molecules are known to have two equivalent orientations, between which they can be switched by the pulsed application of an electric field, i. H. FLC displays can be switched bistably.
  • the switching times are inversely proportional to the spontaneous polarization of the FLC mixture and are in the range of ⁇ s.
  • the main advantage of the FLC displays compared to the LC displays that have so far been found in industrial practice is the multiplex ratio that can be achieved.
  • FIG. 1 A simple matrix arrangement of electrodes (rows 1 to n and columns 1 to m) is shown in Fig. 1.
  • the electrodes are usually located on the inside of the carrier plates of the display with the rows on one and the columns on the other carrier plate. In the crossover areas, the pixels B, the liquid crystal located between rows and columns is switched. As usual, the electrodes are referred to as columns, to which the information-carrying pulses (also called column or data pulses) are applied.
  • the lines are then activated in a stroboscopic manner sequentially by electrical pulses (activation pulses), which is the prerequisite for information transmission to the pixels of the lines.
  • the number of slots can be increased by introducing so-called blanking pulses or (also called reset pulses), as in the literature (e.g. in Proc. SID 28/2, 211 (1987); Japan-Display 18, (1989); Liquid Crystals and Uses, vol. 1, p. 305 ff, World Scientific Publishing Co., 1990; Jap. J. Appl. Physics 28, L483 (1989) and in DE 4017893Al).
  • blanking pulses form part of the line addressing and have the purpose of switching one or more lines of the display into a certain state without the influence of any information transfer to other display lines. According to the in the Proc. SID described method this happens simultaneously for several lines in a special time interval in which no information is written into the display.
  • the image change time of a display is the product of the line addressing time and the number of lines - for a given number of lines (due to standards or requirements for resolution) and a given number of slots proportional to the cycle time ⁇ .
  • the cycle time ⁇ is now capped for at least two reasons: 1. With no ⁇ , the available electrical maximum voltage (limited by semiconductor components or costs) is not sufficient to switch the liquid crystal; 2. If the ⁇ is too small, the voltage required for switching leads to electrical breakdown in the addressed pixel.
  • the restriction mentioned under 1. relates primarily to the row drivers and not so much to the column drivers, since in the addressing methods described above the row drivers have to deliver at least twice the voltage as the column drivers.
  • a number of display properties e.g. B. the contrast or the frame rate, can be improved by choosing a shorter period of time for the information-carrying column pulses than for the line pulses, specifically also for the generation of the write pulse.
  • the invention thus relates to a method for multiplex addressing an FLC switching device, in which an electrical pulse sequence is applied to the row and column electrodes in such a way that the information is transmitted for a pixel in the form of a write pulse, which is built up from the superposition of activating row pulses and Information-carrying column pulses, characterized in that the individual column pulses building up the write pulse are shorter in time than the activating row pulses assigned in time.
  • the invention relates to the structure of the write pulse and it is immaterial how the addressing scheme is otherwise carried out. In order to achieve a short image repetition time, it may be advantageous to work with blanking pulses. Lines addressed one after the other do not necessarily have to be lines that are spatially adjacent.
  • the method for multiplex addressing can also be carried out in that the longest column pulse building the write pulse is shorter than the shortest line pulse building up this write pulse.
  • a DC voltage component is avoided in particular if the write pulses are constructed antisymmetrically, i. H. in the case of time mirroring, represent similar pulses with inverter polarity.
  • control according to the invention can be used advantageously if the ferroelectric liquid crystal in an SSFLC cell is previously brought into a so-called bookshelf geometry by electrical field treatment (SID 91 Digest pp. 396, 1991).
  • the method according to the invention can be carried out in each of the two partial images.
  • the invention can be used both for the black and white addressing of FLC displays with fixed values of the column pulse amplitudes (modulo sign) as also for addressing to generate analog grayscale with variable values of the column pulse amplitudes or lengths.
  • the invention is not limited to FLC displays, but can also be used for other switching elements which, due to their symmetry, can be switched by means of pulse addressing, such as e.g. B. Arrangements with nematic liquid crystals as described in WO 91/11747.
  • the invention is not limited to optical displays, but can also be used for spatial light modulators (SLM) and the like. ⁇ . are used.
  • SLM spatial light modulators
  • the invention relates to an FLC switching device which contains the multiplex addressing system to which the method according to the invention can be applied.
  • Overlapping bipolar pulses of height V r are applied to the lines.
  • bipolar but shorter data pulses of the amplitude V d are added in the pixels, the inversion point of which lies at the same time as the assigned bipolar line pulses (FIG. 3).
  • the overlap time of the bipolar line pulses of successively addressed lines is (2b) ⁇ where ⁇ is the width of the (half) bipolar line pulses and a ⁇ is the width of the (half) bipolar data pulses and the following applies that 0 ⁇ a ⁇ 1, 0 ⁇ 2b ⁇ 1- a.
  • the switching pulse switches (select pulse, supercritical) or does not switch (half-select, subcritical).
  • F1 has the following composition: F1 has the phase sequence X-2 S c * 63 S A 75 N * 851 and has a spontaneous polarization of 45 nC / cm2 at 25 ° C.
  • the pulse area that is primarily relevant for switching is shown hatched for the pixels in FIG. 3. In the subcritical case it is (V r -aV d ) ⁇ and in the supercritical case (V r + aV d ) ⁇ .
  • the line addressing time is 2 (1-b) ⁇ , which is shorter than the time 2 ⁇ that applies to conventional addressing schemes.
  • Example 1 can also be modified in such a way that the polarity of the bipolar line pulses of lines addressed one after the other is inverted.
  • the information coding for the column pulses is inverted accordingly.
  • This addressing has the advantage that the line drivers do not have to deliver more than two voltage levels (0 and V r , or 0 and -V r ) at a given time.
  • Example 1 can also be changed so that the first part of the bipolar row addressing pulse is omitted or - for the purpose of DC field compensation - elsewhere in the addressing scheme - e.g. B. in connection with a blanking pulse - is executed.
  • the lines are exposed to bipolar pulses, but without temporal overlap.
  • 6a to 6c show the optical response after filtering through a low-pass filter, which clearly shows that the contrast in the case according to the invention is approximately twice as large as in the conventional comparison case.
  • the pixels (indicated by way of example: B) of a liquid crystal switching element are the overlap regions of the electrode strips which are applied to the two inner sides of the substrates in such a way that they form horizontal strips (rows) on one substrate and vertical strips (columns) on the other substrate .
  • the known technique of a split screen can also be used, in which the columns z. B. are interrupted in the middle and two fields are written simultaneously by using both ends of the column for data input.
  • Row pulse (1) and column pulse (2) subtract to the pixel signal (3). So far, controls with the same pulse duration for row and column pulses have been used to build up the write pulse.
  • Overlapping line activation pulses allow a shorter line addressing time with correspondingly short pulses for data transmission (second and third lines from above).
  • Exemplary pulse sequences for two information cycles are shown from the electrical addressing sequence for two rows (k and k + 1) (Fig. 3a) and two columns (i and i + 1) (Fig. 3b and c). These lead to the voltage curves shown in the lower part of the figure at the four overlapping pixels of the above. Rows and columns, (Fig. 3d and e).
  • the sequence of pulses is shown as it acts on a picture element or on the test cell filled with the ferroelectric liquid crystal F1 according to Example 1.
  • the associated optical transmission curve of the liquid crystal cell is recorded in intensity units as measured with a photodiode.
  • the electrical pulse sequence contains a reset or blanking pulse R, which switches the liquid crystal independently of the action of data pulses, as well as a supercritical write pulse S (a) and c)) and a subcritical write pulse HS (b) and d)).
  • the simulated overlap time 2b of the line pulses is 16 ⁇ s.
  • the sequence of pulses is shown as it is a picture element of an FLC display under conventional control experiences.
  • the associated optical transmission curve is shown in the lower part of the picture.
  • the complete dark state is shown as a reference line. 5a and b clearly show the interference from the column pulses.
  • a contrast (ratio of light to dark transmission) of just under 10: 1 can be seen from FIG. 5c.

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  • 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)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Liquid Crystal (AREA)
EP93101638A 1992-02-08 1993-02-03 Verfahren zur Ansteuerung von bistabilen, insbesondere ferroelektrischen Flüssigkristalldisplays Withdrawn EP0561135A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4203685 1992-02-08
DE4203685 1992-02-08

Publications (2)

Publication Number Publication Date
EP0561135A2 true EP0561135A2 (de) 1993-09-22
EP0561135A3 EP0561135A3 (enrdf_load_stackoverflow) 1994-12-21

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EP93101638A Withdrawn EP0561135A2 (de) 1992-02-08 1993-02-03 Verfahren zur Ansteuerung von bistabilen, insbesondere ferroelektrischen Flüssigkristalldisplays

Country Status (3)

Country Link
EP (1) EP0561135A2 (enrdf_load_stackoverflow)
JP (1) JPH05281912A (enrdf_load_stackoverflow)
KR (1) KR930018456A (enrdf_load_stackoverflow)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2208559B (en) * 1987-08-12 1991-09-04 Gen Electric Co Plc Ferroelectric liquid crystal devices
GB2208740B (en) * 1987-08-12 1991-09-04 Gen Electric Co Plc Ferroelectric liquid crystal devices
ATE126381T1 (de) * 1989-10-27 1995-08-15 Canon Kk Flüssigkristall-anzeigegerät mit kontrollierter abschaltung.

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KR930018456A (ko) 1993-09-22
EP0561135A3 (enrdf_load_stackoverflow) 1994-12-21
JPH05281912A (ja) 1993-10-29

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