DISPLAY APPARATUS, LIQUID CRYSTAL DISPLAY APPARATUS AND DRIVING METHOD FOR DISPLAY APPARATUS

• US 20030107538A1
• Filed: 06/23/1999
• Published: 06/12/2003
• Est. Priority Date: 06/24/1998
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: ASAO, YASUFUMI, TERADA, MASAHIRO, MORIYAMA, TAKASHI, MORI, SHOSEI, ISOBE, RYUICHIRO, TOGANO, TAKESHI
• Granted Patent: US 6,809,717 B2
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals

Abstract

A display apparatus is constituted by a display device including a plurality of pixels and control means for effecting a plurality of displaying operations at each pixel. Each of the displaying operation includes at least a first operation for displaying a first image at a first luminance and a second operation for displaying a second image substantially identical to the first image at a second luminance, said first and second luminances being non-zero and different from each other. One of the first and second luminances may preferably be smaller than ⅕ of the other luminance.

Claims

1. A display apparatus, comprising:

a display device including a plurality of pixels, and

control means for effecting a plurality of displaying operations at each pixel, each displaying operation including at least a first operation for displaying a first image at a first luminance and a second operation for displaying a second image substantially identical to the first image at a second luminance, said first and second luminances being non-zero and different from each other.

2. An apparatus according to claim 1, wherein one of said first and second luminances is smaller than {fraction (1/5)} of the other luminance.

3. A liquid crystal display apparatus, comprising:

a liquid crystal device including a layer of liquid crystal, a pair of substrates disposed to sandwich the liquid crystal, and a polarizer disposed on at least one of the substrates, at least one of the substrates being provided with an alignment film for aligning the liquid crystal in contact therewith, the pair of substrates respectively having thereon mutually intersecting electrodes for applying a voltage to the liquid crystal thereby forming a matrix of pixels each at an intersection of the electrodes on the pair of substrates, and

control means for effecting a plurality of displaying operations at each pixel, each displaying operation including at least a first operation for displaying a first image at a first luminance and a second operation for displaying a second image substantially identical to the first image at a second luminance, said first and second luminances being non-zero and different from each other.

4. An apparatus according to claim 3, wherein one of said first and second luminances is smaller than {fraction (1/5)} of the other luminance.

5. An apparatus according to claim 3, wherein said first operation is effected by optical modulation so as to provide a first transmittance and said second operation is effected by optical modulation so as to provide a second transmittance which is non-zero and lower than {fraction (1/5)} of the first transmittance.

6. A liquid crystal apparatus, comprising:

a liquid crystal device including a layer of liquid crystal, a pair of substrates disposed to sandwich the liquid crystal, and a polarizer disposed on at least one of the substrates, at least one of the substrates being provided with an alignment film for aligning the liquid crystal in contact therewith, the pair of substrates respectively having thereon mutually intersecting electrodes for applying a voltage to the liquid crystal thereby forming a matrix of pixels each at an intersection of the electrodes on the pair of substrates, and

a light source provided to one of the substrates for emitting light to be optically modulated by the liquid crystal device, and

control means for effecting a plurality of illuminating operations including at least a first operation for displaying a first image by turning the light source on at a first illuminance and a second operation for displaying a second image substantially identical to the first image by turning the light source on at a second illuminance, said first and second illuminances being non-zero and different from each other.

7. An apparatus according to claim 6, wherein one of said first and second illuminance is smaller than {fraction (1/5)} of the other illuminance.

8. A liquid crystal apparatus, comprising:

a liquid crystal device including a layer of chiral smectic liquid crystal, a pair of substrates disposed to sandwich the liquid crystal, and a polarizer disposed on at least one of the substrates, at least one of the substrates being provided with an alignment film for aligning the liquid crystal in contact therewith, the pair of substrates respectively having thereon mutually intersecting electrodes for applying a voltage to the liquid crystal thereby forming a matrix of pixels each at an intersection of the electrodes on the pair of substrates, and

voltage application means for applying a voltage to the liquid crystal through the electrodes, wherein

the liquid crystal has an alignment characteristic such that the liquid crystal is aligned to provide an average molecular axis to be placed in a monostable alignment state under no voltage application, is tilted from the monostable alignment state in one direction when supplied with a voltage of a first polarity at a tilting angle which varies depending on magnitude of the supplied voltage, and is tilted from the monostable alignment state in the other direction when supplied with a voltage of a second polarity opposite to the first polarity at a tilting angle, said tilting angles providing maximum tilting angles formed under application of the voltages of the first and second polarities, respectively, different from each other.

9. An apparatus according to claim 8, wherein said maximum tilting angle formed under application of the voltage of the first polarity is at least five times larger than that formed under application of the voltage of the second polarity.

10. An apparatus according to claim 8, wherein the liquid crystal device provides an emitting light quantity characteristic such that an emitting light quantity from the liquid crystal device provides a first light quantity in the monostable alignment state, a second light quantity most different from the first light quantity in a prescribed tilted state from the monostable alignment state when supplied with the voltage of the first polarity and a third light quantity most different from the first light quantity in a prescribed tilted state from the monostable alignment state when supplied with the voltage of the second polarity, said emitting light quantity being changed continuously between the first and second light quantities depending on magnitude of the supplied voltage of the first polarity by changing a tilting angle of the liquid crystal from a molecular position in the monostable alignment state, and the first and third light quantities providing a difference therebetween smaller than that between the first and second light quantities.

11. An apparatus according to claim 10, wherein the emitting light quantity from the liquid crystal device provides the first light quantity as a maximum value and the second light quantity as a maximum value.

12. An apparatus according to claim 11, wherein the emitting light quantity provides a ratio of the second light quantity to the third light quantity of at least 5.

13. An apparatus according to claim 8, wherein the liquid crystal shows a phase transition on temperature decrease including isotropic liquid phase (Iso), cholesteric phase (Ch) and chiral smectic C phase (SmC*) or isotropic liquid phase (Iso) and chiral smectic C phase (SmC*) and provide a layer normal direction of its smectic molecular layers substantially aligned in one direction in SmC*.

14. An apparatus according to claim 8, wherein the liquid crystal has a helical pitch larger than a cell thickness in a bulk state thereof.

15. An apparatus according to claim 8, which further incudes a drive circuit for effecting active matrix drive allowing analog-like gradational display, and one of the pair of substrates comprises a substrate provided with active devices each electrically connected with an electrode portion defining each of a plurality of pixels.

16. An apparatus according to claim 10, which further includes a drive circuit for effecting active matrix drive, and one of the substrates comprises a substrate provided with active devices each electrically connected with an electrode portion defining each of a plurality of pixels each of which is supplied with a driving signal from said drive circuit, said driving signal including in a first period a voltage of a first polarity equal to or larger than a voltage or providing a prescribed gradational image at a light quantity between the first and second light quantities and in a second period a voltage for providing a light quantity between the first and third light quantities, thereby to effect desired gradational display through the first and second period.

17. An apparatus according to claim 16, wherein the first light quantity is a minimum value of the emitting light quantity from the liquid crystal device and the second light quantity is a maximum value of the emitting light quantity.

18. An apparatus according to claim 17, wherein the emitting light quantity provides a ratio of the second light quantity to the third light quantity of at least 5.

19. An apparatus according to claim 8, wherein the liquid crystal device is of a transmission-type.

20. An apparatus according to claim 8, wherein the liquid crystal device is of a reflection-type.

21. A liquid crystal apparatus, comprising:

a liquid crystal device including a layer of liquid crystal, a pair of substrates disposed to sandwich the liquid crystal, and a polarizer disposed on at least one of the substrates, the pair of substrates respectively having thereon mutually intersecting electrodes for applying a voltage to the liquid crystal thereby forming a matrix of pixels each at an intersection of the electrodes on the pair of substrates, and

a drive circuit for driving the liquid crystal device to effect desired gradational display based on change in emitting light quantity for each pixel, wherein each pixel is supplied with a driving signal from said drive circuit, said driving signal including in a first period a voltage of a first polarity for providing a prescribed light quantity equal to or larger than a light quantity for providing a prescribed gradational image and in a second period a voltage of a second polarity opposite to the first polarity for providing a second light quantity smaller than the prescribed light quantity but larger than zero, thereby to effect desired gradational display through the first and second periods.

22. An apparatus according to claim 21, which and one of the pair of substrates comprises a substrate provided with active devices each electrically connected with an electrode portion defining each of the pixels, and the liquid crystal device was driven by the drive circuit to effect active matrix drive allowing analog-like gradational display.

23. A driving method for a display apparatus wherein a plurality of color lights are successively emitted from a color light source and in synchronism with the respective light emissions, switching of the respective lights is effected by a display device to visually color-mixing the respective lights to provide a full-color image, said driving method comprising:

dividing one frame period into a plurality of field periods and further dividing each field period into a plurality of sub-field periods,

changing a color of a light emitted from the color light source for each field period, and

displaying a higher luminance image in at least one sub-field period in each field period and a lower luminance image in at least one another sub-field period in each field period.

24. A method according to claim 23, wherein each field period is divided into three sub-field periods, and a displaying operation is performed so that a higher luminance image is displayed in one of the sub-field periods, a lower luminance image is displayed in another one of the sub-field periods and in the remaining sub-field period a luminance is set to be substantially zero.

25. A method according to claim 23, wherein the lower luminance image is displayed at a luminance which is non-zero and lower than {fraction (1/5)} of that of the higher luminance image.

26. A method according to claim 23, wherein the lights emitted from the color light source are three colors of red, green and blue and one frame period is divided into three field periods.

27. A method according to claim 23, wherein the display device is a liquid crystal device.

28. A method according to claim 27, wherein the liquid crystal device comprises a pair of substrates each provided with electrodes and a liquid crystal disposed between the pair of substrates so as to form a plurality of pixels and is driven by applying a voltage to the electrodes of the substrates to control a luminance thereby to display a higher luminance image or a lower luminance image.

29. A method according to claim 28, wherein the liquid crystal is a chiral smectic liquid crystal.

30. A method according to claim 29, wherein the chiral smectic liquid crystal has an alignment characteristic such that the liquid crystal is aligned to provide an average molecular axis to be placed in a monostable alignment state under no voltage application, is tilted from the monostable alignment state in one direction when supplied with a voltage of a first polarity, and is tilted from the monostable alignment state in the other direction when supplied with a voltage of a second polarity opposite to the first polarity.

31. A method according to claim 30, wherein the liquid crystal is tilted from the monostable alignment state under application of the first polarity voltage to provide a maximum tilting angle different from that formed under application of the second polarity voltage.

32. A method according to claim 31, wherein said maximum tilting angle formed under application of the voltage of the first polarity is larger than that formed under application of the voltage of the second polarity.

33. An apparatus according to claim 32, wherein said maximum tilting angle formed under application of the voltage of the first polarity is at least fine times larger than that formed under application of the voltage of the second polarity.

34. A method according to claim 29, wherein the liquid crystal shows a phase transition on temperature decrease including isotropic liquid phase (Iso), cholesteric phase (Ch) and chiral smectic C phase (SmC*) or isotropic liquid phase (Iso) and chiral smectic C phase (SmC*) and provide a layer normal direction of its smectic molecular layers substantially aligned in one direction in SmC*.

35. A method according to claim 29, wherein the liquid crystal has a helical pitch larger than a cell thickness in a bulk state thereof.

36. A method according to claim 23, wherein the display device is of a transmission-type.

37. A method according to claim 23, wherein the display device is of a reflection-type.