LIQUID CRYSTAL DISPLAY DEVICE

• US 20070176882A1
• Filed: 01/31/2007
• Published: 08/02/2007
• Est. Priority Date: 01/31/2006
• Status: Active Grant

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: Nishiyama, Kazuhiro, Suzuki, Daiichi, Okita, Mitsutaka, ARAKI, Shigesumi
• Granted Patent: US 8,223,299 B2
• Time in Patent Office: Days
• US Class Current: 345/101
• CPC Class Codes: G09G 2300/0491 Use of a bi-refringent liquid crystal, optically controlled bi-refringence [OCB] with bend and splay states, or electrically controlled bi-refringence [ECB] for controlling the color
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

The OCB mode liquid crystal display device applies a black display voltage V(Tr) with temperature characteristic requirements expressed by:
V(T)=<Vs(T), and V(Tr−ΔT)=V(T)=<Vs(Tr), where T represents a panel temperature of the liquid crystal panel, Tr represents a sensed temperature, ΔT represents a temperature difference between the panel temperature and the sensed temperature, and Vs(T) represents an optimal black display voltage.

Claims

1. A liquid crystal display device having an OCB mode liquid crystal panel, comprising:

a temperature-sensing unit configured to sense a temperature Tr around the liquid crystal panel;

a liquid crystal drive voltage-applying unit configured to determine a black display voltage V(Tr) when brightness of the liquid crystal panel is made minimum with respect to the sensed temperature Tr and applying the black display voltage V(Tr), the liquid crystal drive voltage-applying unit applying the black display voltage V(Tr) satisfying temperature characteristic requirements expressed by;

V(T)=<

Vs(T) and,
V(Tr−

Δ

T)=V(T)=<

Vs(Tr),

where T is a panel temperature of the liquid crystal panel, Δ

T is a temperature difference between the sensed temperature Tr and panel temperature T, and Vs(T) is an optimal black display voltage which lowers with a rise of the panel temperature T.

2. The liquid crystal display device of claim 1, wherein a range of the sensed temperature Tr meets a requirement expressed by:

20°

C.<

Tr<

30°

C.

3. The liquid crystal display device of claim 1, wherein the liquid crystal drive voltage-applying unit makes the black display voltage V(T) substantially constant when the panel temperature T is equal to or below a predetermined temperature Ts.

4. The liquid crystal display device of claim 1, wherein the liquid crystal drive voltage-applying unit lowers the black display voltage V(T) together with the panel temperature T when the panel temperature T is equal to or below a predetermined temperature Ts.

5. The liquid crystal display device of claim 1, further comprising a storage unit which stores a black display voltage V(Tr) with the temperature characteristic requirements attached,

wherein the liquid crystal drive voltage-applying unit reads out the black display voltage V(Tr) from the storage unit in response to input of the sensed temperature Tr and applies the black display voltage V(Tr).

6. The liquid crystal display device of claim 1, wherein the liquid crystal drive voltage-applying unit forces display voltages for other color gradations to fluctuate corresponding to the black display voltage V(Tr).

7. The liquid crystal display device of claim 1, further comprising a drive circuit to drive the liquid crystal panel,

wherein the temperature-sensing unit is provided on the drive circuit.

10. The liquid crystal display device of claim 1 or 2, wherein the temperature control unit includes a digital temperature sensor.

8. A liquid crystal display device comprising:

an OCB mode liquid crystal panel having a pair of substrates and a liquid crystal layer held between the paired substrates;

a temperature-sensing unit configured to sense a temperature of a periphery of the liquid crystal panel when the liquid crystal panel is installed in a housing; and

a control unit configured to control a black display voltage to be applied to the liquid crystal layer depending on a panel temperature of the liquid crystal panel in order to display a black image, the control unit correcting a sensed temperature sensed by the temperature-sensing unit based on a predetermined correction amount, and setting the black display voltage depending on a correction temperature produced by the correction.

11. The liquid crystal display device of claim 8, wherein the first memory includes a rewritable storage medium.

9. A liquid crystal display device comprising:

an OCB mode liquid crystal panel having a pair of substrates and a liquid crystal layer held between the paired substrates;

a temperature-sensing unit configured to sense a temperature of a periphery of the liquid crystal panel when the liquid crystal panel is installed in a housing;

a control unit configured to control a black display voltage to be applied to the liquid crystal layer depending on a panel temperature of the liquid crystal panel in order to display a black image;

a first memory which stores a correction amount between a sensed temperature sensed by the temperature-sensing unit and the panel temperature of the liquid crystal panel; and

a second memory which stores a correction table of the black display voltage to be applied to the liquid crystal layer with respect to the panel temperature of the liquid crystal panel,

the control unit correcting the sensed temperature sensed by the temperature-sensing unit based on the correction amount stored in the first memory, and setting the black display voltage depending on a correction temperature produced by the correction based on the correction table stored in the second memory.

12. The liquid crystal display device of claim 9, wherein the first memory includes a rewritable storage medium.

13. A liquid crystal display device comprising:

an OCB mode liquid crystal panel having a pair of substrates and a liquid crystal layer held between the paired substrates;

a temperature-sensing unit configured to sense a temperature of a periphery of the liquid crystal panel; and

a control unit configured to control a black display voltage to be applied to the liquid crystal layer depending on a panel temperature of the liquid crystal panel in order to display a black image, the control unit setting the black display voltage to a predetermined constant voltage based on a sensed temperature sensed by the temperature-sensing unit when having sensed a temperature below a particular temperature, and the control unit setting the black display voltage so that the higher the sensed temperature is, the lower the black display voltage is in comparison to the constant voltage when having sensed a temperature equal to or above the particular temperature.

14. The liquid crystal display device of claim 13, wherein the particular temperature is set to a temperature within a range of 25 to 50°

C.

15. The liquid crystal display device of claim 13, wherein the temperature control unit includes a digital temperature sensor.

16. The liquid crystal display device of claim 13, further comprising a memory which stores a correction table of the black display voltage to be applied to the liquid crystal layer with respect to the panel temperature of the liquid crystal panel.

17. The liquid crystal display device of claim 16, wherein the memory includes a rewritable storage medium.

18. A liquid crystal display device comprising:

an OCB mode liquid crystal panel having a pair of substrates and a liquid crystal layer held between the paired substrates;

a temperature-sensing unit configured to sense a temperature of a periphery of the liquid crystal panel;

a control unit configured to control a black display voltage to be applied to the liquid crystal layer depending on a panel temperature of the liquid crystal panel in order to display a black image;

a first memory which stores a correction amount between a sensed temperature sensed by the temperature-sensing unit and the panel temperature of the liquid crystal panel; and

a second memory which stores a correction table of the black display voltage to be applied to the liquid crystal layer with respect to the panel temperature of the liquid crystal panel, the control unit correcting the sensed temperature sensed by the temperature-sensing unit based on the correction amount stored in the first memory, and setting the black display voltage depending on a correction temperature produced by the correction based on the correction table stored in the second memory,

wherein the correction table is data covering a voltage distribution taking a predetermined constant voltage with respect to a temperature below a particular temperature, and taking a voltage so that the higher the sensed temperature is, the lower the voltage is in comparison to the constant voltage, with respect to the sensed temperature equal to or above the particular temperature.

19. A liquid crystal display device comprising:

an OCB mode liquid crystal panel having a pair of substrates and a liquid crystal layer held between the paired substrates;

a temperature-sensing unit configured to sense a temperature of a periphery of the liquid crystal panel;

a control unit configured to control a black display voltage to be applied to the liquid crystal layer depending on a temperature of the liquid crystal panel in order to display a black image; and

a measurement unit configured to measure an elapsed time, the control unit setting the black display voltage depending on the temperature sensed by the temperature-sensing unit from power-on to time when the measurement unit has measured a predetermined length of time, correcting the temperature sensed by the temperature-sensing unit, and setting the black display voltage depending on a temperature produced by the correction from and after the time when the measurement unit has measured the predetermined length of time from the power-on.

20. The liquid crystal display device of claim 19, further comprising a memory which stores correction data of the black display voltage to be applied to the liquid crystal layer with respect to the temperature of the liquid crystal panel.

21. The liquid crystal display device of claim 19, wherein the control unit corrects the temperature so that a predetermined value is subtracted from the temperature sensed by the temperature-sensing unit.

22. A liquid crystal display device comprising:

an OCB mode liquid crystal panel having a pair of substrates and a liquid crystal layer held between the paired substrates;

a temperature-sensing unit configured to sense a temperature of a periphery of the liquid crystal panel;

a control unit configured to control a black display voltage to be applied to the liquid crystal layer depending on a temperature of the liquid crystal panel in order to display a black image;

a measurement unit configured to measure an elapsed time; and

a memory which stores first correction data of the black display voltage to be applied to the liquid crystal layer with respect to the temperature of the liquid crystal panel, and second correction data of the black display voltage to be applied to the liquid crystal layer with respect to the temperature sensed by the temperature-sensing unit, the control unit setting the black display voltage depending on the temperature sensed by the temperature-sensing unit based on the first correction data from power-on to time when the measurement unit has measured a predetermined length of time, and setting the black display voltage based on the second correction data depending on the temperature sensed by the temperature-sensing unit from and after the time when the measurement unit has measured the predetermined length of time from the power-on.

23. A liquid crystal display device comprising:

an OCB mode liquid crystal panel having a pair of substrates and a liquid crystal layer held between the paired substrates;

a temperature-sensing unit configured to sense a temperature of a periphery of the liquid crystal panel;

a control unit configured to control a black display voltage to be applied to the liquid crystal layer depending on a temperature of the liquid crystal panel in order to display a black image;

a measurement unit configured to measure an elapsed time; and

a memory which stores correction data of the black display voltage to be applied to the liquid crystal layer with respect to the temperature of the liquid crystal panel, the control unit setting the black display voltage based on the correction data depending on the temperature sensed by the temperature-sensing unit from power-on to time when the measurement unit has measured a predetermined length of time, and setting the black display voltage to a value lower than a value depending on the temperature sensed by the temperature-sensing unit based on the correction data from and after the time when the measurement unit has measured the predetermined length of time from the power-on.