EP0903721A2 - Méthode de commande d'un crystal liquide nématique - Google Patents

Méthode de commande d'un crystal liquide nématique Download PDF

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Publication number
EP0903721A2
EP0903721A2 EP98113183A EP98113183A EP0903721A2 EP 0903721 A2 EP0903721 A2 EP 0903721A2 EP 98113183 A EP98113183 A EP 98113183A EP 98113183 A EP98113183 A EP 98113183A EP 0903721 A2 EP0903721 A2 EP 0903721A2
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EP
European Patent Office
Prior art keywords
liquid crystal
nematic liquid
driving
electrodes
voltage
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.)
Ceased
Application number
EP98113183A
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German (de)
English (en)
Other versions
EP0903721A3 (fr
Inventor
Masaya Okita
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Individual
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Individual
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Publication date
Application filed by Individual filed Critical Individual
Publication of EP0903721A2 publication Critical patent/EP0903721A2/fr
Publication of EP0903721A3 publication Critical patent/EP0903721A3/fr
Ceased 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
    • 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
    • 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
    • G09G2310/065—Waveforms comprising zero voltage phase or pause
    • 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

Definitions

  • This invention relates to a method for driving a liquid crystal, especially, a nematic liquid crystal.
  • liquid crystal display devices based on the above principle can be shaped flat and are operative with low electric power, they have been widely used in wrist watches, electronic calculating machines, and so forth. In recent years, they are also used in combination with color filters to form color display devices in note-type personal computers and small liquid crystal TV sets, for example.
  • liquid crystal display devices have been inferior to CRT displays especially when used as TV displays for displaying moving images or as personal computer displays required to quickly follow the movements of a mouse cursor.
  • color filters are their optical transmittance as low as 20% approximately.
  • the brightness decreases to approximately one fifth, and a large electric power is consumed for back-lighting to compensate the brightness.
  • Japanese Patent Laid-Open 1-179914 (1989) discloses a color liquid crystal display device to display color images by combining a black-and-white panel and tricolor back-lighting instead of using color filters. This method certainly appears more likely to realize high-fidelity color images inexpensively. Practically, however, response speeds of nematic liquid crystals by conventional liquid crystal driving methods are as slow as several decades of milliseconds through hundreds of milliseconds, and it has been believed difficult to realize a response speed not slower than 8 milliseconds required for color images by tricolor back-lighting with a liquid crystal panel using a nematic liquid crystal.
  • the present invention is based on the above knowledge of the Inventor, and its basic concept lies in increasing the response speed of a liquid crystal by applying a voltage to the liquid crystal at a unique timing different from those of conventional driving circuits.
  • a method for driving a nematic liquid crystal in a liquid crystal display device which includes a nematic liquid crystal, two electrodes confining the nematic liquid crystal and a pair of polarizing plates sandwiching the electrodes confining the nematic liquid crystal, comprising:
  • the voltage applied across two electrodes may be inverted in polarity.
  • the nematic liquid crystal may be heated to a predetermined temperature.
  • the liquid by returning or maintaining the voltage across two electrodes to or in a predetermined value for a predetermined time in predetermined intervals, the liquid can be driven at a much higher response speed than those of conventional driving methods. Therefore, a liquid crystal panel suitable for color images by tri-color back-lighting and for moving images with a high contrast ratio can be realized. It is also possible to reduce the power consumption.
  • Fig. 1 shows an aspect where a voltage is applied to a high-speed nematic liquid crystal panel using appropriate one of conventional TN liquid crystals or STN liquid crystals and optimizing the cell gap. Further, intervals, T1 through T6, are equal in length, and the length is not longer than 8 milliseconds which is the slowest acceptable driving cycle required for driving a liquid crystal for color images by tricolor back-lighting.
  • optical transmittance of a liquid crystal changes with absolute values of applied voltages regardless of their polarities.
  • the applied voltage is usually changed in polarity in predetermined intervals because continuous application of a d.c. voltage to a liquid crystal will cause an electro-chemical reaction and will deteriorate the liquid crystal. Therefore, also in the embodiment of the invention, applied voltages are inverted in polarity.
  • inversion of polarities is substantially immaterial to the subject matter of the invention, namely, high-speed driving of a liquid crystal.
  • each of the intervals of time T1 through T6 includes two time zones.
  • One of these time zones (the former of each of T1 through T6 in Fig. 1) is the time where a voltage responsive to image data is applied, and the absolute value represents V1 or 0V depending upon the image data.
  • the other time zone (the latter of each of T1 through T6) is the time where the voltage of 0V is applied irrespectively of the image data. That is, in the present embodiment, the applied voltage is forcibly changed to or maintained in 0V for a predetermined time in predetermined intervals.
  • the applied voltage responsive to image data is 0V
  • the optical transmittance maintains the black level throughout the intervals.
  • the applied voltage first becomes V1 in response to image data, and is forcibly changed to 0V later.
  • the optical transmittance first changes from the black level to the white level and then changes from the white level to the black level. That is, the optical transmittance changes from the black level to the white level, and returns from the black level to the white level within each interval, T1, T2, T4 or T6.
  • Fig. 2 shows an aspect where a voltage is applied by using the same nematic liquid crystal panel as used in Fig. 1, and the same image data is supplied. Also the intervals T1 through T6 are the same as those of Fig. 1.
  • the applied voltage is determined exclusively by image data. Therefore, the absolute value of the applied voltage becomes V2 or 0V, depending upon the image data to be displayed, but the value is maintained throughout the interval, or beyond the interval, until an image data is changed to the next image data. In this case, the movement of the liquid crystal is slow, and it takes time for the optical transmittance to change. For example, even when the absolute of the applied voltage changes from V2 to 0V, like T2 to T3 in Fig. 2, the optical transmittance does not change the full black level within the interval T3. Further, when the absolute value of the applied voltage changes from 0V to V2 like T3 to T4 in Fig.
  • the optical transmittance begins to change from an incomplete black level toward the full black level, but fails to return to the full white level within the interval T1. That is, the response speed of the liquid by the conventional driving method is slow, and high-contrast images cannot be displayed at a sufficient speed either on a TN liquid crystal panel or on a STN liquid crystal panel.
  • the embodiment can change the optical transmittance from the black level to the white level or vice versa more quickly by changing the applied voltage to 0V for a predetermined time in predetermined intervals. Additionally, the embodiment can use a higher applied voltage V1 than V2 of the conventional method to change the optical transmittance to the white level. This is effective for more quickly changing the optical transmittance from the black level to the white level.
  • the embodiment of the invention invert the polarity within each interval (T1 through T6) so that the average voltage becomes substantially 0V in each interval (T1 to T6). Since the liquid crystal moves very quickly, if the polarity is inverted between two adjacent intervals (for example, if the polarity in the interval T1 is positive, the polarity is changed to negative in the interval T1), flickers will occur due to a delicate difference between absolute values of the positive applied voltage and the negative applied voltage.
  • the frame cycle must be set appropriately in accordance with characteristics of the liquid crystal. If the frame period is short, the optical transmittance of a certain liquid crystal fails to return to the original level within the interval, and it results in a decrease in contrast ratio. In contrast, if the frame period is long, flickers are liable to occur.
  • the duration of time required for the optical transmittance to return to the original level largely varies with the property of the liquid crystal material, especially, the viscosity of the liquid crystal material. Therefore, by selecting an appropriate liquid crystal whose optical transmittance quickly returns to the original level, high-contrast images with substantially no flicker can be realized. Even when a normal liquid crystal is used, the time for returning the optical transmittance to the original level can be shortened by increasing the temperature to adjust the viscosity, and high-contrast images can be ensured.
  • Fig. 1 has been explained as using a normally-black liquid crystal panel which displays black under no applied voltage.
  • a normally-white liquid crystal panel configured to display white under no applied voltage, by appropriately modifying the voltage to be applied for a predetermined time in predetermined intervals.
  • substantially the same effects are promised by appropriately modifying the voltage to be applied for a predetermined time in predetermined intervals.
  • the liquid can be driven very quickly. Therefore, on a liquid crystal panel using the invention, the operation for displaying and completely erasing an image can be completed in a very short time, and high-quality moving images are promised.
  • the waveform of the applied voltage used in the invention is essentially the same as that used for TFT systems, the invention is applicable also to TFT liquid crystal panels. Also for other driving systems, the operation speed of liquid crystals can be increased by appropriately changing the applied voltage value for a predetermined time in predetermined intervals.
  • the method according to the invention is configured to complete the operation for displaying an image and erasing it completely within each frame interval, it is optimum for color images by tricolor back-lighting, and can realize high-performance, inexpensive color displays.

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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)
  • Liquid Crystal (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Liquid Crystal Substances (AREA)
EP98113183A 1997-09-12 1998-07-15 Méthode de commande d'un crystal liquide nématique Ceased EP0903721A3 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP26781997A JPH1184341A (ja) 1997-09-12 1997-09-12 ネマティック液晶の駆動方法
JP26781997 1997-09-12
JP267819/97 1997-09-12

Publications (2)

Publication Number Publication Date
EP0903721A2 true EP0903721A2 (fr) 1999-03-24
EP0903721A3 EP0903721A3 (fr) 1999-07-21

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EP98113183A Ceased EP0903721A3 (fr) 1997-09-12 1998-07-15 Méthode de commande d'un crystal liquide nématique

Country Status (6)

Country Link
EP (1) EP0903721A3 (fr)
JP (1) JPH1184341A (fr)
KR (1) KR100639602B1 (fr)
CN (1) CN1161729C (fr)
CA (1) CA2243383C (fr)
TW (1) TW421775B (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0949605A1 (fr) * 1998-04-10 1999-10-13 Masaya Okita Méthode de commande à haute vitesse d'un panneau d'affichage à cristaux liquides

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1202503C (zh) 2000-12-22 2005-05-18 日商·互网路股份有限公司 液晶驱动装置以及灰度显示方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3812463A1 (de) * 1987-04-15 1988-10-27 Akad Wissenschaften Ddr Verfahren zum ansteuern einer fluessigkristallzelle
EP0438093A2 (fr) * 1990-01-16 1991-07-24 Honeywell Inc. Dispositif et méthode de compensation en température d'afficheurs à cristal liquide
JPH06118383A (ja) * 1992-10-07 1994-04-28 Sharp Corp 液晶表示装置の駆動方法
EP0827130A2 (fr) * 1996-08-26 1998-03-04 Bright Lab. Co., Ltd. Méthode et dispositif de commande d'un cristal liquide

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2346974A1 (de) * 1973-09-18 1975-04-03 Commissariat Energie Atomique Verfahren und abbildungseinrichtung zum sequentiellen steuern einer optischen kenngroesse
JPH03132692A (ja) * 1989-10-18 1991-06-06 Matsushita Electric Ind Co Ltd 液晶表示装置の駆動方法及びその駆動回路

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3812463A1 (de) * 1987-04-15 1988-10-27 Akad Wissenschaften Ddr Verfahren zum ansteuern einer fluessigkristallzelle
EP0438093A2 (fr) * 1990-01-16 1991-07-24 Honeywell Inc. Dispositif et méthode de compensation en température d'afficheurs à cristal liquide
JPH06118383A (ja) * 1992-10-07 1994-04-28 Sharp Corp 液晶表示装置の駆動方法
EP0827130A2 (fr) * 1996-08-26 1998-03-04 Bright Lab. Co., Ltd. Méthode et dispositif de commande d'un cristal liquide

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
"LCDisplays", ELEKTOR, vol. 2420, May 1980 (1980-05-01), CANTERBURY, pages 34 - 43 *
SMITH PAUL: "Multiplexing liquid-crystal displays", ELECTRONICS, vol. 51, no. 11, 25 May 1978 (1978-05-25), pages 113 - 121 *
WILD P.J.; KLEIN H.P.; WULLSCHLEGER J.: "Alphanumeric and Quasianalog Liquid Crystal Displays and Their Application", BROWN BOVERI REVIEW, vol. 66, February 1979 (1979-02-01), pages 48 - 53 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0949605A1 (fr) * 1998-04-10 1999-10-13 Masaya Okita Méthode de commande à haute vitesse d'un panneau d'affichage à cristaux liquides

Also Published As

Publication number Publication date
CN1211778A (zh) 1999-03-24
CA2243383C (fr) 2012-12-18
EP0903721A3 (fr) 1999-07-21
KR100639602B1 (ko) 2006-12-19
TW421775B (en) 2001-02-11
CN1161729C (zh) 2004-08-11
KR19990029212A (ko) 1999-04-26
JPH1184341A (ja) 1999-03-26
HK1019106A1 (en) 2000-01-21
CA2243383A1 (fr) 1999-03-12

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