Driving method of liquid crystal display panel and liquid crystal display device

• US 20030001813A1
• Filed: 07/19/2002
• Published: 01/02/2003
• Est. Priority Date: 01/21/2000
• Status: Active Grant

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Inventors: Sekiguchi, Kanetaka
• Granted Patent: US 7,161,569 B2
• Time in Patent Office: Days
• US Class Current: 345/96
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2300/0895 having more than one selection line for a two-terminal active matrix LCD, e.g. Lechner and D2R circuits
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3633 with transmission/voltage characteristic comprising multiple loops, e.g. antiferroelectric liquid crystals
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals

Abstract

This invention is a driving method of a liquid crystal display panel in which a liquid crystal layer is sealed between a transparent first substrate formed with a plurality of scanning electrodes and a transparent second substrate formed with a plurality of data electrodes, the electrodes being formed on respective inner faces opposing each other, and portions where the scanning electrodes and data electrodes oppose each other with the liquid crystal layer sandwiched therebetween constitute pixel portions respectively, and which performs display by an electrooptical change having a memory property in the liquid crystal layer at each pixel portion, in which selection signals are applied to the plurality of scanning electrodes and a data signal is applied to the data electrode in correspondence with the selection signal of each scanning electrode to control the individual pixel portion independently, and a plurality of selection signals having different selection periods each for selecting one scanning electrode are selectively applied as the selection signals.

Claims

1. A driving method of a liquid crystal display panel in which a liquid crystal layer is sealed between a transparent first substrate formed with a plurality of scanning electrodes and a transparent second substrate formed with a plurality of data electrodes, said electrodes being formed on respective inner faces opposing each other, and portions where said scanning electrodes and data electrodes oppose each other with said liquid crystal layer sandwiched therebetween constitute pixel portions respectively, and which performs display by an electrooptical change having a memory property in said liquid crystal layer at each said pixel portion, wherein

selection signals are applied to said plurality of scanning electrodes and a data signal is applied to said data electrode in correspondence with said selection signal of each said scanning electrode to control said individual pixel portion independently, and a plurality of selection signals having different selection periods each for selecting one scanning electrode are selectively applied as said selection signals.

2. The driving method of a liquid crystal display panel according to claim 1, wherein

a liquid crystal layer charge memory period, during which potentials of said scanning electrode and said data electrode are set to the same potential or a floating potential, is provided after each said pixel portion within a display region of said liquid crystal display panel is selected at least once and display contents thereof are rewritten.

3. The driving method of a liquid crystal display panel according to claim 1, wherein

a liquid crystal layer charge memory period, during which potentials of said scanning electrode and said data electrode are set to the same potential or a floating potential, is provided after each said pixel portion within a display region of said liquid crystal display panel is repeatedly selected and display contents thereof are rewritten a plurality of times.

4. The driving method of a liquid crystal display panel according to claim 1, wherein

a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer at the same time to said liquid crystal layer between each of said plurality of scanning electrodes and each of said plurality of data electrodes is provided before said selection period of a first scanning electrode by said selection signal, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

5. The driving method of a liquid crystal display panel according to claim 1, wherein

a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer to said liquid crystal layer between said scanning electrode and said data electrode associated therewith is provided before said selection period of each said scanning electrode by said selection signal, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

6. The driving method of a liquid crystal display panel according to claim 1, wherein

a whole display rewriting and a partial display rewriting are performed, in said whole display rewriting, said selection signal being applied to each of said scanning electrodes constituting all said pixel portions within a display region of said liquid crystal display panel, and said data signal being applied to each said data electrode in correspondence with said selection signal of each said scanning electrode to thereby rewrite display contents of all said pixel portions, and in said partial display rewriting, said selection signals being applied only to said scanning electrodes constituting said pixel portions within a display change region where display contents are changed within said display region, said data signals being applied only to said data electrodes associated therewith respectively, and potentials of said scanning electrodes and said data electrodes constituting said pixel portions except for said display change region being set to a floating potential to thereby rewrite a part of display contents of said display region.

7. The driving method of a liquid crystal display panel according to claim 6, wherein

said selection period for selecting one scanning electrode by said selection signal is made longer in said partial display rewriting than in said whole display rewriting.

8. The driving method of a liquid crystal display panel according to claim 7, wherein

a potential difference between said scanning electrode to which said selection signal is applied and said data electrode to which said data signal is applied is made smaller in said partial display rewriting than in said whole display rewriting.

9. The driving method of a liquid crystal display panel according to claim 6, wherein

when said partial display rewriting is switched to said whole display rewriting, a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer at the same time to said liquid crystal layer between each of said plurality of scanning electrodes and each of said plurality of data electrodes is provided before start of said whole display rewriting, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

10. The driving method of a liquid crystal display panel according to claim 7, wherein

when said partial display rewriting is switched to said whole display rewriting, a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer at the same time to said liquid crystal layer between each of said plurality of scanning electrodes and each of said plurality of data electrodes is provided before start of said whole display rewriting, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

11. The driving method of a liquid crystal display panel according to claim 8, wherein

when said partial display rewriting is switched to said whole display rewriting, a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer at the same time to said liquid crystal layer between each of said plurality of scanning electrodes and each of said plurality of data electrodes is provided before start of said whole display rewriting, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

12. The driving method of a liquid crystal display panel according to claim 1, wherein

a voltage amplitude of at least one of said selection signal and said data signal is decreased as said selection period for selecting one scanning electrode by said selection signal is increased.

13. The driving method of a liquid crystal display panel according to claim 1, wherein

a longest selection period for selecting one scanning electrode by said selection signal is 100 milliseconds or more.

14. The driving method of a liquid crystal display panel according to claim 1, wherein

a potential difference between said selection signal to be applied to said scanning electrode and said data signal to be applied to said data electrode when said selection period for selecting one scanning electrode by said selection signal is short is made larger than a potential difference between said selection signal and said data signal when said selection period is long.

15. The driving method of a liquid crystal display panel according to claim 1, wherein

said plurality of selection signals having different selection periods are changed after said pixel portions at least within a predetermined region in said display region of said liquid crystal display panel are selected and display contents thereof are rewritten.

16. The driving method of a liquid crystal display panel according to claim 1, wherein

said selection signal and said data signal are generated by electric energy generated by a power generating element or by discharge energy of a storage battery for storing said electric energy, and said selection period for selecting one scanning electrode by said selection signal is changed in accordance with an amount of power generated by said power generating element or an amount of power stored in said storage battery.

17. The driving method of a liquid crystal display panel according to claim 16, wherein

said selection period for selecting one scanning electrode by said selection signal is made shorter and a potential difference between said selection signal to be applied to said scanning electrode and said data signal to be applied to said data electrode is made larger when the amount of power generated by said power generating element or the amount of power stored in said storage battery is large than when it is small.

18. The driving method of a liquid crystal display panel according to claim 1, wherein

said plurality of selection signals are switched at a set point of time, and one selection signal of said plurality of selection signals has a period during which a potential thereof to said data signal is positive and a period during which the potential is negative in said selection period of one scanning electrode.

19. The driving method of a liquid crystal display panel according to claim 15, wherein

one selection signal of said plurality of selection signals has a period during which a potential thereof to said data signal is positive and a period during which the potential is negative in said selection period of one scanning electrode, and assuming that a period from selection of a first scanning electrode to rewrite once display contents of each said pixel portion within said display region of said liquid crystal display panel to reselection of said first scanning electrode to rewrite them the next time is defined as a field, an order of the period during which the potential of said selection signal to said data signal is positive and the period during which the potential is negative is reversed in a filed and in the next field.

20. The driving method of a liquid crystal display panel according to claim 1, wherein

assuming that a period from selection of a first scanning electrode to rewrite once display contents of each said pixel portion within a display region of said liquid crystal display panel to reselection of said first scanning electrode to rewrite them the next time is defined as a field, each said selection signal applies voltages of the same polarity during said period for selecting each said scanning electrode in a sequential plurality of fields, and thereafter applies voltages of both positive and negative polarities during said period for selecting one scanning electrode in the next field.

21. The driving method of a liquid crystal display panel according to claim 1, wherein

in a mode of reducing power consumption, voltages of one polarity to said data signal are applied as said selection signal during said selection period of each said scanning electrode by said selection signal, and

a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer at the same time to said liquid crystal layer between each of said plurality of scanning electrodes and each of said plurality of data electrodes is provided before said selection period of a first scanning electrode by said selection signal, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

22. The driving method of a liquid crystal display panel according to claim 1, wherein

in a mode of reducing power consumption, assuming that a period from selection of a first scanning electrode to rewrite once display contents of each said pixel portion within a display region of said liquid crystal display panel to reselection of said first scanning electrode to rewrite them the next time is defined as a field, there are provided a field, in which voltages of one polarity to said data signal are applied as said selection signal during said selection period of said scanning electrode by said selection signal, and a field, in which voltages of both positive and negative polarities are applied, and

a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer at the same time to said liquid crystal layer between each of said plurality of scanning electrodes and each of said plurality of data electrodes is provided before said selection period of a first scanning electrode by said selection signal, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

23. The driving method of a liquid crystal display panel according to claim 1, wherein

in a mode of reducing power consumption, assuming that a period from selection of a first scanning electrode to rewrite once display contents of each said pixel portion within a display region of said liquid crystal display panel to reselection of said first scanning electrode to rewrite them the next time is defined as a field, there are provided a field, in which voltages of one polarity to said data signal are applied as said selection signal during said selection period of said scanning electrode by said selection signal, and a field, in which voltages of both positive and negative polarities are applied,

said selection period of one scanning electrode is made longer in the field, in which said voltages of both positive and negative polarities to said data signal are applied as said selection signal, than in the field, in which said voltages of one polarity are applied, and absolute values of said voltages of both polarities are made equal to absolute values of said voltages of one polarity, and

a refresh period for applying a refresh voltage for canceling unbalance of charge in said liquid crystal layer at the same time to said liquid crystal layer between each of said plurality of scanning electrodes and each of said plurality of data electrodes is provided before said selection period of a first scanning electrode by said selection signal, and voltages of both positive and negative polarities are applied as said refresh voltage by said selection signal and said data signal.

25. The liquid crystal display device according to claim 24, wherein

said liquid crystal layer performing an electrooptical change having a memory property is a chiral nematic liquid crystal layer.

26. The liquid crystal display device according to claim 24, wherein

said liquid crystal layer performing an electrooptical change having a memory property is a ferroelectric liquid crystal layer.

27. The liquid crystal display device according to claim 24, wherein

said liquid crystal layer performing an electrooptical change having a memory property is an antiferroelectric liquid crystal layer.

28. The liquid crystal display device according to claim 24, wherein

said liquid crystal layer performing an electrooptical change having a memory property is a scattering type liquid crystal layer composed of a ferroelectric liquid crystal and a transparent solid substance containing a ferroelectric liquid crystal.

29. The liquid crystal display device according to claim 24, further comprising a power generating element,

wherein said liquid crystal display panel drive circuit being a circuit for generating said selection signal and said data signal by electric energy generated by said power generating element or by discharge energy of a storage battery for storing said electric energy, and having means for changing said selection period for selecting one scanning electrode by said selection signal in accordance with an amount of power generated by said power generating element or an amount of power stored in said storage battery.

30. The liquid crystal display device according to claim 29, wherein

said power generating element is a photovoltaic element.

31. The liquid crystal display device according to claim 30, wherein

said photovoltaic element is provided on a visible side of said liquid crystal display panel and a reflection type polarizer is provided on the visible side of said liquid crystal display panel or opposite side thereto to reflect incident light from outside toward said photovoltaic element by said reflection type polarizer.

32. The liquid crystal display device according to claim 24, wherein

said liquid crystal display panel drive circuit has means for making a potential difference between said selection signal and said data signal larger when said selection period by said selection signal is short than when said selection period is long, and

said liquid crystal display device further comprising an operation member for causing, from outside, said liquid crystal display panel drive circuit to select said selection signal having a different selection period.

33. The liquid crystal display device according to claim 24, further comprising a power generating element,

wherein said liquid crystal display panel drive circuit has means for making a potential difference between said selection signal and said data signal larger when said selection period by said selection signal is short than when said selection period is long as well as for making said potential difference smaller when an amount of power generated by said power generating element is small than when said amount of power generation is large, and

an operation member for forcing, from outside, said liquid crystal display panel drive circuit to increase said selection period by said selection signal and decrease said potential difference is provided.

35. The liquid crystal display device according to claim 34, wherein

each said pixel portion is provided with a storage element connected in series to said switching element and in parallel to said liquid crystal layer constituting said pixel portion.

36. The liquid crystal display device according to claim 35, wherein

said storage element is composed of a capacitor.

37. The liquid crystal display device according to claim 34, wherein

said switching element is a thin film transistor with a semiconductor layer of polysilicon.

39. The liquid crystal display device according to claim 38, wherein

each said pixel portion is provided with a storage element connected in series to said switching element and in parallel to said liquid crystal layer constituting said pixel portion.

40. The liquid crystal display device according to claim 39, wherein

said storage element is composed of a capacitor.

41. The liquid crystal display device according to claim 38, wherein

said switching element is a thin film diode composed of an amorphous silicon film.

24. A liquid crystal display device, comprising:

a liquid crystal display panel in which a liquid crystal layer is sealed between a transparent first substrate formed with a plurality of scanning electrodes and a transparent second substrate formed with a plurality of data electrodes, said electrodes being formed on respective inner faces opposing each other, and portions where said scanning electrodes and said data electrodes oppose each other with said liquid crystal layer sandwiched therebetween constitute pixel portions respectively, and which performs display by an electrooptical change having a memory property in said liquid crystal layer at each said pixel portion; and

a liquid crystal display panel drive circuit for applying selection signals to said plurality of scanning electrodes and applying a data signal to said data electrode in correspondence with said selection signal of each said scanning electrode to control said individual pixel portion independently, and for selectively applying, as said selection signals, a plurality of selection signals having different selection periods each for selecting one scanning electrode.

34. A liquid crystal display device, comprising:

a liquid crystal display panel, in which transparent first and second substrates are disposed with inner faces opposing each other, a plurality of scanning electrodes and a plurality of signal electrodes are formed to be perpendicular to each other as well as a pixel electrode is formed for every isolated region surrounded by said scanning electrodes and said signal electrodes on said inner face of one of said substrates, an opposed electrode is formed on said inner face of the other of said substrates, a liquid crystal layer is sealed between said first substrate and said second substrate, and portions where said pixel electrodes and said opposed electrode oppose each other with said liquid crystal layer sandwiched therebetween constitute pixel portions respectively, and

a switching element which is ON/OFF controlled by said selection signal applied to each said scanning electrode is provided between said signal electrode and said pixel electrode in the vicinity of an intersection of each said scanning electrode and signal electrode, and

which performs display by an electrooptical change having a memory property in said liquid crystal layer at each said pixel portion; and

a liquid crystal display panel drive circuit for applying selection signals to said plurality of scanning electrodes and applying a data signal to said signal electrode in correspondence with said selection signal of each said scanning electrode to control said individual pixel portion independently, and for selectively applying, as said selection signals, a plurality of selection signals having different selection periods each for selecting one scanning electrode.

38. A liquid crystal display device, comprising:

a liquid crystal display panel, in which transparent first and second substrates are disposed with inner faces opposing each other, a plurality of signal electrodes and many pixel electrodes adjacent to said signal electrodes are formed on said inner face of one of said substrates, a plurality of scanning electrodes perpendicular to said signal electrodes and opposing said pixel electrodes are formed on said inner face of the other of said substrates, a liquid crystal layer is sealed between said first substrate and said second substrate, and portions where said pixel electrodes and said scanning electrodes oppose each other with said liquid crystal layer sandwiched therebetween constitute pixel portions respectively, and

a switching element is provided between said signal electrode and each said pixel electrode, and

which performs display by an electrooptical change having a memory property in said liquid crystal layer at each said pixel portion; and

a liquid crystal display panel drive circuit for applying selection signals to said plurality of scanning electrodes and applying a data signal to said signal electrode in correspondence with said selection signal of each said scanning electrode to control said individual pixel portion independently, and for selectively applying, as said selection signals, a plurality of selection signals having different selection periods each for selecting one scanning electrode.