Liquid crystal display device

• US 20060092122A1
• Filed: 12/07/2005
• Published: 05/04/2006
• Est. Priority Date: 08/04/2003
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Betsui, Keiichi, Yoshihara, Toshiaki, Tadaki, Shinji, Makino, Tetsuya, Kiyota, Yoshinori, Shiroto, Hironori, Kasahara, Shigeo
• Granted Patent: US 7,724,229 B2
• Time in Patent Office: Days
• US Class Current: 345/99
• CPC Class Codes: G09G 2330/022 in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3677 suitable for active matrices only

Abstract

A voltage corresponding to desired image data is applied to a ferroelectric liquid crystal having a spontaneous polarization at a predetermined cycle to rewrite the displayed image (period A), and then, all voltages applied to the ferroelectric liquid crystal are removed (timing C) to retain the displayed image before the removal (period B). A gate selection period (voltage application period to the ferroelectric liquid crystal) t₂ before stopping the voltage application is set longer than a gate selection period (voltage application period to the ferroelectric liquid crystal) t₁ in the normal display. Increasing the voltage application period to the ferroelectric liquid crystal provides a sufficient response of the liquid crystal during the gate selection period, thereby realizing high memory ability.

Claims

1. A liquid crystal display device comprising a liquid crystal material sealed in a gap formed by at least two substrates;

and switching elements corresponding to respective pixels, for controlling selection/non-selection of voltage application to control light transmittance of the liquid crystal material, and having a first display function that displays an image by applying a voltage to the liquid crystal material through the switching elements, and a second display function that stops the application of voltage to the liquid crystal material through the switching elements and retains a display state just before the application of voltage is stopped, wherein a selection period of the switching elements just before the stop of the application of voltage for executing the second display function is longer than a selection period of the switching elements in the first display function.

2. The liquid crystal display device according to claim 1, wherein all pixels are caused to display black image before resuming the application of voltage to the liquid crystal material to return to the first display function from the second display function.

3. The liquid crystal display device according to claim 2, wherein the selection period of the switching elements upon causing all pixels to display black image is longer than the selection period of the switching elements in the first display function.

4. A liquid crystal display device comprising a liquid crystal material sealed in a gap formed by at least two substrates;

and switching elements corresponding to respective pixels, for controlling selection/non-selection of voltage application to control light transmittance of the liquid crystal material, and having a first display function that displays an image by applying a voltage to the liquid crystal material through the switching elements, and a second display function that stops the application of voltage to the liquid crystal material through the switching elements and retains a display state just before the application of voltage is stopped, wherein a non-selection period of the switching elements just before the stop of the application of voltage for executing the second display function is longer than a non-selection period of the switching elements in the first display function.

5. The liquid crystal display device according to claim 4, wherein all pixels are caused to display black image before resuming the application of voltage to the liquid crystal material to return to the first display function from the second display function.

6. The liquid crystal display device according to claim 5, wherein the non-selection period of the switching elements upon causing all pixels to display black image is longer than the non-selection period of the switching elements in the first display function.

7. A liquid crystal display device comprising a liquid crystal material sealed in a gap formed by at least two substrates;

and switching elements corresponding to respective pixels, for controlling selection/non-selection of voltage application to control light transmittance of the liquid crystal material, and having a first display function that displays an image by applying a voltage to the liquid crystal material through the switching elements, and a second display function that stops the application of voltage to the liquid crystal material through the switching elements and retains a display state just before the application of voltage is stopped, wherein an image display is performed by carrying out a switching between a first driving system in which a selection period of the switching elements just before the stop of the application of voltage for executing the second display function is longer than a selection period of the switching elements in the first display function and a second driving system in which the selection period of the switching elements just before the stop of the application of voltage for executing the second display function is equal to the selection period of the switching elements in the first display function.

8-10. -10. (canceled)

11. A liquid crystal display device comprising a liquid crystal material sealed in a gap formed by at least two substrates;

and switching elements corresponding to respective pixels, for controlling selection/non-selection of voltage application to control light transmittance of the liquid crystal material, and having a first display function that displays an image by applying a voltage to the liquid crystal material through the switching elements, and a second display function that stops the application of voltage to the liquid crystal material through the switching elements and retains a display state just before the application of voltage is stopped, wherein an image display is performed by carrying out a switching between a first driving system in which a non-selection period of the switching elements just before the stop of the application of voltage for executing the second display function is longer than a non-selection period of the switching elements in the first display function and a second driving system in which the non-selection period of the switching elements just before the stop of the application of voltage for executing the second display function is equal to the non-selection period of the switching elements in the first display function.

12. The liquid crystal display device according to claim 7 or claim 11, further comprising measuring means for measuring a temperature of the liquid crystal display material and means for controlling the switching between the first driving system and the second driving system according to the measured results of the measuring means.