EP0420129A2 - Elektrooptisches Gerät mit Flüssigkristallen und Steuerverfahren dafür - Google Patents

Elektrooptisches Gerät mit Flüssigkristallen und Steuerverfahren dafür Download PDF

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Publication number
EP0420129A2
EP0420129A2 EP90118351A EP90118351A EP0420129A2 EP 0420129 A2 EP0420129 A2 EP 0420129A2 EP 90118351 A EP90118351 A EP 90118351A EP 90118351 A EP90118351 A EP 90118351A EP 0420129 A2 EP0420129 A2 EP 0420129A2
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EP
European Patent Office
Prior art keywords
liquid crystal
optical device
substrates
crystal electro
pair
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Withdrawn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
EP90118351A
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English (en)
French (fr)
Other versions
EP0420129A3 (en
Inventor
Takashi Fukui
Toshio Watanabe
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.)
Semiconductor Energy Laboratory Co Ltd
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Semiconductor Energy Laboratory Co Ltd
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 Semiconductor Energy Laboratory Co Ltd filed Critical Semiconductor Energy Laboratory Co Ltd
Publication of EP0420129A2 publication Critical patent/EP0420129A2/de
Publication of EP0420129A3 publication Critical patent/EP0420129A3/en
Withdrawn legal-status Critical Current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

Definitions

  • the present invention relates to a method of driving a liquid crystal electro-optical device with high contrast and the liquid crystal electro-optical device having high contrast.
  • Nematic liquid crystals having positive dielectric anisotropy including optically active substances therein are disposed between a pair of substrates and are arranged in a helical structure wherein the uppermost and lowermost nematic liquid crystals between said pair of substrates are oriented in different directions by an angle of 90°.
  • Liquid crystal panels of twisted nematic (TN) type having such a helical structure above mentioned have been used for watches, electric calculators and so on for years.
  • liquid crystal electro-optical devices of super twisted nematic (STN) type have been popular as comparatively large sized displays such as displays of word processors.
  • the difference of the structures of the liquid crystal electro-optical device of STN type from that or the liquid crystal electro-optical device or TN type is that, particularly, the angle at which the uppermost and lowermost nematic liquid crystals between a pair of substrates in said device of STN type are crossed is not 90° but 180° to 270°.
  • the threshold value of voltage against switching or liquid crystals becomes definite compared with the case of the liquid crystal electro-optical device of TN type.
  • the application for comparatively large displays can be actualized though the conventional liquid crystal electro-optical devices of TN type could not be used as such large displays.
  • the comparative large display has a large duty number, for example 200 to 240, in the case of the liquid crystal electro-optical device of STN type.
  • a frame frequency during driving the conventional liquid crystal electro-optical device of STN type is in the range of 120 to 160Hz.
  • Fig. 2(A) shows a waveform of pulsed voltage applied to liquid crystals at one picture element of the liquid crystal electro-optical device of STN type having a duty number of 200 to 240.
  • the pulsed voltage is applied at a frame frequency of 120 to 160Hz.
  • a quantity of light transmitted through said one picture element varies as shown in Fig. 2(B).
  • Fig. 2(B) shows a waveform appearing on an oscilloscope display by inputting in the oscilloscope a voltage into which the quantity of light is converted by photomultiplier.
  • every pulsed voltage acts as ON voltage.
  • Pulsed voltage 5 is applied to the picture element of the conventional liquid crystal electro-optical device of STN type in order to obtain a black display and a low voltage 6 is applied to the same picture element in order to obtain a white display.
  • the quantity of transmitted light becomes too large when the low voltage is applied. For this reason, an application of pulsed voltage 5 after the application of the low voltage 6 results in almost white display rather than black display.
  • a liquid crystal electro-­optical device of STN type in which the uppermost and lowermost nematic liquid crystals are oriented in different directions by an angle of 180° to 270° and which has a duty number of 200 or more, is driven at a frame frequency of 200 to 280Hz.
  • the present invention has an object to provide a liquid crystal electro-optical device having high contrast.
  • the device in accordance with the present invention has nematic liquid crystals having positive dielectric anisotropy including optically active substances which are disposed between a pair of substrates and the nematic liquid crystals are arranged in a helical structure wherein the uppermost and lowermost nematic liquid crystals are oriented in different directions at an angle of 180° to 270°.
  • the device has a duty number of 200 or more. In order to obtain high contrast, such a device is driven at a frame frequency of 200 to 280Hz.
  • a frame frequency is a reciprocal of the time from the moment that a common electrode is selected till the moment that the common electrode is again selected.
  • Fig. 1(A) is illustrated a waveform of voltage applied to one picture element of display and in Fig. 1(B) is illustrated a waveform of the moment that a quantity of transmitted light on said picture element is converted into voltage and the voltage is inputted in an oscilloscope by the use of a photomultiplier.
  • a pulsed voltage 1 is applied to liquid crystals and the display is made black.
  • a non-selection term 3 the quantity of transmitted light becomes large.
  • the frame frequency is larger than that of a conventional device, a variation 4 of the quantity of transmitted light is less than that of a conventional device. Therefore, when the quantity of transmitted light is integrated within one term, the integral value becomes smaller than that of a conventional case, and black display can be obtained. Accordingly, contrast of display improves largely compared with the contrast of a conventional display.
  • an ITO thin film as transparent electrodes by means of DC sputtering method, and subsequently the ITO (indium tin oxide) thin film is patterned into 640 of segment electrodes by means of well-known photolithography method.
  • a second substrate made from soda glass On a second substrate made from soda glass are formed 240 of common electrodes made from an ITO thin film by means of the same methods as the preceding methods.
  • polyamic acid polyamide carboxylic acid
  • the polyimide thin films formed on the both substrates are rubbed by the use of cotton cloth.
  • the rubbing treatment is done to cross the rubbing directions of the first and the second substrates at an angle of 240°.
  • On one substrate are scattered ball-like fine particles made of SiO2 having the diameter of 7.5 ⁇ m (which are called spacers) and on the other substrate is screen-printed a sealing material consisting mainly of epoxy resin, and the substrates are mated.
  • liquid crystals are injected by means of well-­known vacuum injection method to produce a liquid crystal panel. But the center of the panel swells by the injection, so that pressing is again carried out. Namely, in order to take the excessive liquid crystals out from the interior of the panel, pressure is added toward the inside. Then an injection port of liquid crystals is sealed with ultraviolet ray curable agent, and the liquid crystal panel is completed.
  • a pair of polarizing plates is disposed sandwiching the liquid crystal panel.
  • liquid crystal panel and a driving circuit are connected by the use of FPC (flexible print circuit).
  • an ITO thin film as transparent electrodes by means of DC sputtering method, and subsequently the ITO thin film is patterned into 640 of segment electrodes by means of well-known photolithography method.
  • a second substrate made from soda glass On a second substrate made from soda glass are formed 240 of common electrodes made from an ITO thin film by means of the same methods as the preceding methods.
  • first and second substrates are applied polyamic acid by the use of an offset press, and the substrates are heated at a temperature of 300 degrees Centigrade for 3 hours to form polyimide thin films thereon.
  • the polyimide thin films formed on the both substrates are rubbed by the use of cotton cloth.
  • the rubbing treatment is done to cross the rubbing directions of the first and the second substrates at an angle of 240°.
  • On one substrate are scattered ball-like fine particles made of SiO2 having the diameter of 7.5 ⁇ m (which are called spacers) and on the other substrate is screen-printed a sealing material consisting mainly of epoxy resin, and the substrates are mated.
  • liquid crystals are injected by means of well-­known vacuum injection method to produce a liquid crystal panel. But the center of the panel swells by the injection, so that pressing is again carried out. Namely, in order to take the excessive liquid crystals out from the interior of the panel, pressure is added toward the inside. Then an injection port of liquid crystals is sealed with ultraviolet ray curable agent, and the liquid crystal panel is completed.
  • a pair of polarizing plates is disposed sandwiching the liquid crystal panel.
  • liquid crystal panel and a driving circuit are connected by the use of FPC.
  • an ITO thin film as transparent electrodes by means of DC sputtering method, and subsequently the ITO thin film is patterned into 640 of segment electrodes by means of well-known photolithography method.
  • a second substrate made from soda glass On a second substrate made from soda glass are formed 240 of common electrodes made from an ITO thin film by means of the same methods as the preceding methods.
  • first and second substrates are applied polyamic acid by the use of an offset press, and the substrates are heated at a temperature of 300 degrees Centigrade for 3 hours to form polyimide thin films thereon.
  • the polyimide thin films formed on the both substrates are rubbed by the use of cotton cloth.
  • the rubbing treatment is done to cross the rubbing directions of the first and the second substrates at an angle of 240°.
  • On one substrate are scattered ball-like fine particles made of SiO2 having the diameter of 5.6 ⁇ m (which are called spacers) and on the other substrate is screen-printed a sealing material consisting mainly of epoxy resin, and the substrates are mated.
  • liquid crystals are injected by means of well-­known vacuum injection method to produce a liquid crystal panel. But the center of the panel swells by the injection, so that pressing is again carried out. Namely, in order to take the excessive liquid crystals out from the interior of the panel, pressure is added toward the inside. Then an injection port of liquid crystals is sealed with ultraviolet ray curable agent, and the liquid crystal panel is completed.
  • film 30 having anisotropy of refractive index whose retardation dn o -dn e is 305nm and film 31 having anisotropy of refractive index whose retardation dn o -dn e is 390nm (dn o is an optical distance of ordinary ray and dn e is an optical distance of extraordinary ray) are stuck on one surface of the liquid crystal panel 33 in order to remove the coloring which is characteristic of a conventional liquid crystal electro-optical device of STN type.
  • a pair of polarizing plates 32 and 34 is disposed sandwiching the liquid crystal panel.
  • liquid crystal panel and a driving circuit are connected by the use of FPC.
  • a liquid crystal panel is produced followed by sticking both film 30 having anisotropy of refractive index whose retardation dn o -dn e is 305nm and film 31 having anisotropy of refractive index whose retardation dn o -­dn e is 390nm on one surface of the liquid crystal panel 33. Further a pair of polarizing plates 32 and 34 is disposed sandwiching the liquid crystal panel. Then the liquid crystal panel and a driving circuit are connected by the use of FPC.
  • an ITO thin film as transparent electrodes by means of DC sputtering method, and subsequently the ITO thin film is patterned into 640 of segment electrodes by means of well-known photolithography method.
  • a second substrate made from soda glass On a second substrate made from soda glass are formed 240 of common electrodes made from an ITO thin film by means of the same methods as the preceding methods.
  • first and second substrates are applied polyamic acid by the use of an offset press, and the substrates are heated at a temperature of 300 degrees Centigrade for 3 hours to form polyimide thin films thereon.
  • the polyimide thin films formed on the both substrates are rubbed by the use of cotton cloth.
  • the rubbing treatment is done to cross the rubbing directions of the first and the second substrates at an angle of 240°.
  • On one substrate are scattered ball-like fine particles made of SiO2 having the diameter of 5.5 ⁇ m (which are called spacers) and on the other substrate is screen-printed a sealing material consisting mainly of epoxy resin, and the substrates are mated.
  • liquid crystals are injected by means of well-­known vacuum injection method to produce a liquid crystal panel. But the center of the panel swells by the injection, so that pressing is again carried out. Namely, in order to take the excessive liquid crystals out from the interior of the panel, pressure is added toward the inside. Then an injection port of liquid crystals is sealed with ultraviolet ray curable agent, and the liquid crystal panel is completed.
  • films 38 and 39 having anisotropy of refractive index whose retardation dn o -dn e is 350nm are stuck on the both surfaces of the liquid crystal panel 35 in order to remove the coloring which is characteristic of a conventional liquid crystal electro-optical device of STN type. Further a pair of polarizing plates 36 and 37 is disposed sandwiching the liquid crystal panel.
  • liquid crystal panel and a driving circuit are connected by the use of FPC.
  • a liquid crystal panel is produced followed by sticking films 38 and 39 having anisotropy of refractive index whose retardation dn o -dn e is 350nm on both surfaces of the liquid crystal panel 35. Further a pair of polarizing plates 36 and 37 is disposed sandwiching the liquid crystal panel. Then the liquid crystal panel and a driving circuit are connected by the use of FPC.
  • an ITO thin film as transparent electrodes by means of DC sputtering method, and subsequently the ITO thin film is patterned into segment electrodes by means of well-known photolithography method.
  • first and second substrates are applied polyamic acid by the use of an offset press, and the substrates are heated at a temperature of 300 degrees Centigrade for 3 hours to form polyimide thin films thereon.
  • the polyimide thin films formed on the both substrates are rubbed by the use of cotton cloth.
  • the rubbing treatment is done to cross the rubbing directions of the first and the second substrates at an angle of 240°.
  • On one substrate are scattered ball-like fine particles made of SiO2 having the diameter of 6.2 ⁇ m (which are called spacers) and on the other substrate is screen-printed a sealing material consisting mainly of epoxy resin, and the substrates are mated.
  • liquid crystals are injected by means of well-­known vacuum injection method to produce a panel for driving liquid crystals. But the center of the panel swells by the injection, so that pressing is again carried out. Namely, in order to take the excessive liquid crystals out from the interior of the panel, pressure is added toward the inside. Then an injection port of liquid crystals is sealed with ultraviolet ray curable agent, and the panel for driving liquid crystals is completed.
  • third and fourth substrates made from soda glass is applied polyamic acid by the use of an offset press, and subsequently the substrates are heated at a temperature of 300 degrees Centigrade for 3 hours to form polyimide thin films thereon.
  • the polyimide thin films formed on the both substrates are rubbed by the use of cotton cloth.
  • the rubbing treatment is done to cross the rubbing directions of the third and the fourth substrates at an angle of 240° in the opposite direction to the case of the panel for driving liquid crystals. Further the rubbing direction of the third substrate and the rubbing direction of the second substrate are crossed at an angle of 80°.
  • On one substrate are scattered ball-like fine particles made of SiO2 having the diameter of 7.5 ⁇ m (which are called spacers) and on the other substrate is screen-printed a sealing material consisting mainly of epoxy resin. Then the substrates are mated.
  • liquid crystals are injected by means of well-­known vacuum injection method to produce a panel for optical compensation. But the center of the panel swells by the injection, so that pressing is again carried out. Namely, in order to take the excessive liquid crystals out from the interior of the panel, pressure is added toward the inside. Then an injection port of liquid crystals is sealed with ultraviolet ray curable agent, and the panel for optical compensation is completed.
  • polarizing plates 16 and 17, a light source 20, the panel for driving liquid crystals 11, and the panel for optical compensation 12 are disposed as shown in Fig.5 and Fig.6.
  • the orientation direction of liquid crystals on a substrate 14 in the panel for driving liquid crystals 11 and the orientation direction of liquid crystals on a substrate 15 in the panel for optical compensation 15 are crossed at an angle of 80°.
  • the panel for driving liquid crystals and a driving circuit are connected by the use of FPC.

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  • Engineering & Computer Science (AREA)
  • Liquid Crystal (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)
EP19900118351 1989-09-25 1990-09-24 Liquid crystal electro-optical device and method for driving the same Withdrawn EP0420129A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP24873189 1989-09-25
JP248731/89 1989-09-25

Publications (2)

Publication Number Publication Date
EP0420129A2 true EP0420129A2 (de) 1991-04-03
EP0420129A3 EP0420129A3 (en) 1992-04-22

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Application Number Title Priority Date Filing Date
EP19900118351 Withdrawn EP0420129A3 (en) 1989-09-25 1990-09-24 Liquid crystal electro-optical device and method for driving the same

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EP (1) EP0420129A3 (de)
JP (1) JP2873616B2 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0674304A3 (de) * 1994-03-23 1996-09-04 Seiko Instr Inc Flüssigkristallanzeigegerät.

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6145479B2 (ja) * 2015-07-16 2017-06-14 スタンレー電気株式会社 液晶表示装置

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
HITACHI REVIEW. vol. 38, no. 2, April 1989, TOKYO JP pages 103 - 108; K.KINUGAWA ET AL.: 'High Resolution Super-Twisted Nematic Liquid Crystal Displays' *
IEE PROCEEDINGS I. SOLID- STATE & ELECTRON DEVICES. vol. 133, no. 4, August 1986, STEVENAGE GB pages 145 - 151; J.R.HUGHES ET AL.: 'Contrast variations in high-level multiplexed twisted nematic liquid crystal displays' *
TRANSACTIONS OF THE INSTITUTE OF ELECTRONICS, & COMMUNICATION ENGINEERING vol. E71, no. 11, November 1988, TOKYO JP pages 1063 - 1069; E.KANEKO: 'Directly Addressed Matrix Liquid Crystal Display Panels with High Information Content' *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0674304A3 (de) * 1994-03-23 1996-09-04 Seiko Instr Inc Flüssigkristallanzeigegerät.
US5748162A (en) * 1994-03-23 1998-05-05 Seiko Instruments Inc. Low voltage liquid crystal display device

Also Published As

Publication number Publication date
EP0420129A3 (en) 1992-04-22
JPH03174116A (ja) 1991-07-29
JP2873616B2 (ja) 1999-03-24

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