Liquid crystal display unit and display control method therefor

• US 6,873,311 B2
• Filed: 03/19/1998
• Issued: 03/29/2005
• Est. Priority Date: 10/14/1997
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Makino, Tetsuya, Kiyota, Yoshinori, Mochizuki, Akihiro, Shiroto, Hironori, Yoshihara, Toshiaki
• Primary Examiner(s): Liang, Regina
• Assistant Examiner(s): Dinh, Duc Q.
• Application Number:
  US09/044,421
• Publication Number:
  US 20020000960A1
• Time in Patent Office: 2,567 Days
• Field of Search: 345 87- 89, 345102-103, 345 94- 96
• US Class Current: 345/87
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals

Abstract

A liquid crystal display unit includes a liquid crystal panel having a plurality of liquid crystal pixels and a plurality of switching elements provided in correspondence to the respective pixels. A back light disposed at the back of the liquid crystal panel and guides red, green, and blue light to the surface thereof; an image memory for storing pixel data PD to be displayed on the respective pixels; an inverted data generating circuit for generating inverted pixel data #PD of the respective pixel data PD; and a control signal generating circuit and a data driver wherein first scanning for writing the pixel data PD with respect to individual pixels of the liquid crystal panel during each period in which red, green, and blue light are emitted in time-sharing manner, and second scanning for writing the inverted pixel data #PD with respect thereto are carried out in this order. Such problems that crosstalk occurs easily, besides response speed thereof is comparatively slow, so that it is not suitable for display of moving picture despite manufacturing cost of STN type display unit is comparatively inexpensive, while because TFT-TN type display unit requires a highly luminous back light, its power consumption is high, viewing angle is narrow, adjustment is difficult in color balance and the like are solved.

Claims

1. A display control method for a liquid crystal display unit which includes two polarizing plates, each polarizing plate having a polarizing axis, the polarizing plates being disposed in directions along which the respective polarizing axes cross at right angles with each other;

a liquid crystal panel sandwiched between the polarizing plates, the liquid crystal panel having a plurality of pixels;

a back light disposed at the back of the liquid crystal panel, the back light being composed of a light source, and a light-emitting region, the light-emitting region guiding red, green, and blue light emitted from the light source into the liquid crystal panel;

a plurality of switching elements, at least one switching element being provided for each one of the plurality pixels, selective ones of the switching elements being ON/OFF driven in response to red, green, and blue data of selected ones of the plurality of pixels during a period of respective display cycles, and at the same time, red, green, and blue light of the back light being emitted in a time-sharing manner in synchronism with the ON/OFF driving of corresponding ones of the plurality of switching elements during the period of respective display cycles, said method comprising;

a first scanning for displaying individual ones of the plurality of pixels of the liquid crystal panel; and

a second scanning for erasing the display of said individual ones of the plurality of pixels are carried out in this order, during each period in which the back light emits red, green, blue light in a time-sharing manner;

wherein an electric field is applied to respective ones of said pixels of said liquid crystal panel at each of said first scanning and said second scanning, a direction of said electric field applied to each of said pixels during said first scanning being opposite a direction of said electric field applied to each of said pixels respectively during said second scanning, and a magnitude of said electric field applied to each of said pixels during said first scanning is equivalent to a magnitude of said electric field applied to each of said pixels respectively during said second scanning.

2. The display control method for a liquid crystal display unit as set forth in claim 1, wherein a finishing timing of said first scanning for a given color light is matched to a starting timing of light emission of said given color light, and a starting timing of said second scanning is matched to a finishing timing of light emission of said given color light for each of said red, green and blue colored lights.

3. The display control method for a liquid crystal display unit as set forth in claim 1, wherein a direction of molecular major axes of liquid crystal molecules is made to be substantially coincident with either of polarizing axes of said two polarizing plates in the case when an electric field is applied to respective ones of said pixels of said liquid crystal panel in said second scanning.

4. The display control method for a liquid crystal display unit as set forth in claim 1, wherein a polarity of an applied electric field is controlled such that a direction of molecular major axes of liquid crystal molecules is substantially coincident with either of said polarizing axes of said two polarizing plates when the electric field is applied to respective ones of said pixels of said liquid crystal panel in said second scanning.

5. The display control method for a liquid crystal display unit as set forth in claim 1, wherein said light-emitting region of said back light is divided into at least two, and said light source is divisionally driven in response to said divided light-emitting regions of said back light.

6. The display control method for a liquid crystal display unit as set forth in claim 5, wherein said light source in response to the respective divided light-emitting regions of said back light is controlled in such that said divided light-emitting regions of said back light assume a light-emitting condition or nonemitting condition in synchronism with a scanning of respective ones of said pixels in a section corresponding to said liquid crystal panel.

7. The display control method for a liquid crystal display unit as set forth in claim 5, wherein said light source, in response to said divided light-emitting regions of said back light, is controlled such that the respective divided light-emitting regions of said back light assume a light-emitting condition during only a period wherein selected ones of said pixels of the corresponding section of said liquid crystal panel are in a display state.

15. The display control method according to claim 1, wherein image data supplied from said first scanning to said respective ones of said pixels is passed through an inverted data generating circuit and supplied in said second scanning to same respective ones of said pixels.

8. A liquid crystal display unit, comprising:

two polarizing plates, each said polarizing plate having a polarizing axis, said polarizing plates being disposed in directions along which the respective polarizing axes cross at right angles with each other;

a liquid crystal panel sandwiched between said polarizing plates and composed of a plurality of liquid crystal pixels, and a plurality of switching elements provided in correspondence to said plurality pixels;

a back light composed of a light source, and a light-emitting region which is disposed at the back of said liquid crystal panel, said light-emitting region guides red, green, and blue light emitted from said light source into said liquid crystal panel;

back light control means for controlling said back light so as to output successively red, green, and blue light one by one during a period for one frame wherein an image is displayed; and

liquid crystal driving control means for carrying out a first scanning for displaying on individual pixels of said liquid crystal panel, and a second scanning for erasing such display in this order, during each period in which said back light emits red, green, and blue light in a time-sharing manner;

wherein said liquid crystal driving control means controls said first and second scanning such that an electric field is applied to respective pixels of said liquid crystal panel at each of said first scanning and said second scanning, a direction of said electric field applied to each of said pixels during said first scanning being opposite a direction of said electric field applied to each of said particular pixels respectively during said second scanning, and a magnitude of said electric field applied to each of said pixels during said first scanning is equivalent to a magnitude of said electric field applied to each of said pixels respectively during said second scanning.

9. The liquid crystal display unit as set forth in claim 8, wherein:

said liquid crystal driving control means, includes;

storing means for storing pixel data corresponding to respective ones of said pixels of an image to be displayed on said liquid crystal panel;

inverted data generating means for generating inverted data of said respective ones of said pixel data stored in said storing means;

liquid crystal driving means for carrying out said first scanning and said second scanning with respect to individual pixels of said liquid crystal panel during each period in which said back light emits red, green, and blue light in time-sharing manner in this order; and

control means for supplying said pixel data stored in said storing means to said liquid crystal driving control means at said first scanning, and supplying the inverted data generated by said inverted data generating means to said liquid crystal driving means at said second scanning.

10. The liquid crystal display unit as set forth in claim 8, wherein said two polarizing plates are disposed such that a direction of molecular major axes of liquid crystal molecules is substantially coincident with either of axes of polarization of said two polarizing plates in the case when an electric field is applied to the respective pixels of said liquid crystal panel in said second scanning.

11. The liquid crystal display unit as set forth in claim 8, wherein said liquid crystal driving control means controls a polarity of an applied electric field such that a direction of molecular major axes of liquid crystal molecules is substantially coincident with either of polarizing axes of said two polarizing plates in the case when the electric field is applied to the respective pixels of said liquid crystal panel in said second scanning.

12. The liquid crystal display unit as set forth in claim 8, wherein the light-emitting region of said back light is divided into at least two, and said light source is divided in response to the respective divided light-emitting regions of said back light.

13. The liquid crystal display unit as set forth in claim 12, further comprising means for controlling light emission of said back light such that respective sections of said divided light-emitting regions of said back light assume a light-emitting condition or a nonemitting condition in synchronism with scanning of the respective pixels in a section corresponding to said liquid crystal panel.

14. The liquid crystal display unit as set forth in claim 12, further comprising means for controlling light emission of said back light such that respective sections of said divided light-emitting regions of said back light assume a light-emitting condition during only a period wherein selected ones of said pixels in a corresponding section of said liquid crystal panel are in a display state.