JP3959291B2 - Method for driving liquid crystal panel and liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving method for rapidly shifting a liquid crystal layer to a bend state in which normal display is possible.
[0002]
[Prior art]
Liquid crystal display devices are thin and lightweight, and their use has been expanded in recent years as an alternative to conventional cathode ray tubes. However, the TN (Twisted Nematic) alignment liquid crystal panel that is widely used at present has a narrow viewing angle, a slow response speed, and the liquid crystal element is a holding type, so that it looks like a tail when displaying moving images, etc. Image quality is inferior to CRT.
[0003]
Using an OCB (Optically Compensated Birefringence) liquid crystal having a bend state as disclosed in Japanese Patent Application Laid-Open No. 61-116329 can sufficiently respond to a moving image display and a large screen with a high response speed and a wide viewing angle, and is thinner than a cathode ray tube. A large screen display with low power consumption can be provided. However, in order to shift the OCB liquid crystal to the bend state, it is necessary to apply a high potential difference to the liquid crystal layer for a certain period of time. It has not reached.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a driving method for transitioning a liquid crystal layer to a bend state in a short time at any operating temperature.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, a first invention is a thin film transistor formed in a matrix corresponding to intersections of a plurality of source lines to which pixel data is supplied and a plurality of gate lines to which a scanning signal is supplied, and Positioned between the first substrate on which the pixel electrode connected to the thin film transistor is formed, the second substrate on which the counter electrode facing the first substrate is formed, and the first substrate and the second substrate In a liquid crystal display device including a liquid crystal layer, a source driver that drives a source line, and a gate driver that drives a gate line, the step of bringing the liquid crystal layer into a splay state, and turning on the thin film transistor by sequentially scanning the gate driver to the gate line The source driver applies a different potential to the source line for each gate scan, and the counter electrode has an average value of the potential applied to the source line. A method of driving a liquid crystal panel having a step of applying a constant voltage to bring the liquid crystal layer into a bend state, thereby generating a gate direction electric field between the pixel electrodes for each gate scan, and By setting a positive polarity potential and a negative polarity potential, a bend state can be obtained in a short period of time.
[0006]
In the second invention, the step of bringing the liquid crystal layer into a splay state and a voltage for turning on the thin film transistor by sequential scanning from the gate driver to the gate line are applied, and the source driver varies from gate source to source line for each gate scan and source line. By applying a predetermined voltage to the counter electrode and applying a predetermined voltage to the average value of the potential applied to the source line to put the liquid crystal layer into a bend state. In addition, a gate-direction electric field and a source-direction electric field are generated between the pixel electrodes for each source line, and the pixel electrode in the gate line is set to a positive polarity potential and a negative polarity potential, so that the bend state can be further shortened. Is possible.
[0007]
According to a third aspect of the invention, in the step of setting the liquid crystal layer in a bend state, the polarity of the potential applied from the source driver to the source line is controlled in response to the temperature change, and the inversion cycle of the potential applied to the pixel electrode is variable. By doing so, it is possible to bend in a short period of time in response to a temperature change.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 6. FIG. 6 shows a configuration diagram of one pixel of the liquid crystal panel used in the embodiment of the present invention.
[0009]
(Embodiment 1)
FIG. 1 is a time chart according to the first embodiment. The actual operation will be described below with reference to FIG. Here, in order to simplify the description, a model with three gate lines is considered. POL in FIG. 1 is a signal applied to the source driver. When POL is H, a positive polarity voltage is applied to the source line, and when it is L, a negative polarity voltage is applied to the source line.
[0010]
A reset period 101 is provided in order to change the arrangement state of the liquid crystal layer disturbed by power-on or the like into a uniform spray state arrangement. The potential (liquid crystal layer) between the pixel electrode and the counter electrode during this period is 0V. Without this reset period, the entire panel does not transition to the bend state even if a considerably large voltage is applied to the liquid crystal layer. Here, the gate waveform in the reset period 101 is subjected to sequential scanning (normal driving) that is turned ON line by line in order to simplify the driving waveform. However, in the case of a large panel, the penetration voltage of the pixel transistor 601 due to gate OFF differs within the panel surface, and the potential of the pixel electrode and the counter electrode on the entire panel surface may not be 0V. In this case, it is better to keep the gate waveform in the reset period 101 all ON and fix the pixel electrode potential of the entire panel. When the gate waveform is fully turned on, it is better to change the timing for each gate line or a plurality of gate lines. Then, the current concentration of the gate driver can be reduced and the configuration of the power supply circuit can be simplified, so that the power can be reduced. Note that in the reset period 101, a uniform spray state cannot be obtained unless the potentials of the pixel electrode and the counter electrode are within ± 1V.
[0011]
Next, in order to make the liquid crystal layer bend completely, a transition voltage application period 102 is provided. In this period, a large voltage is applied to the counter electrode, and a maximum voltage whose polarity changes every gate scan is applied to the source line from the source driver. In the period A, when the first gate line is turned ON, POL is H, so that the source line potential becomes a positive polarity potential, and the first line pixel electrode potential 105 becomes a positive polarity potential. Next, when the second gate line is turned on, POL is L at this time, so that the pixel electrode potential 106 of the second line becomes a negative polarity potential. Next, when the third gate line is turned on, since POL is H, the pixel electrode potential 107 of the third line becomes a positive polarity potential.
[0012]
FIG. 2A shows the state of the pixel electrode. Further, the pixel electrode potential in the period B in FIG. 1 is as shown in FIG. In FIG. 2, an electric field is generated between the pixel electrodes for each gate scan. When this gate direction electric field 201 is generated, transition nuclei are generated in this portion, and the speed at which the liquid crystal layer is bent can be increased.
[0013]
Further, by repeating the period A and the period B in FIG. 1, it is possible to make the pixel electrode in the gate line have a positive polarity potential and a negative polarity potential. Can be in a state. Here, the reset period 101 and the transition voltage application period 102 should be repeated twice or more. This is because the bend state may not be completely achieved at a low temperature where it is difficult to bend only with one reset period 101 and transition voltage application period 102. Note that the counter electrode potential 104 in the transition voltage application period 102 is preferably equal to or higher than the maximum potential applied to the source line. However, when the counter electrode potential 104 in that period is a negative voltage with respect to the average value of the potential applied to the source line, it is preferably equal to or less than the minimum potential applied to the source line.
[0014]
When driving as described above is performed and the liquid crystal layer on the entire surface of the panel is completely bent, the normal display period 103 is set next, and video display becomes possible. When the driving method according to the first embodiment is used, the entire panel can be completely bent in a shorter time, and an image can be displayed.
[0015]
(Embodiment 2)
In the first embodiment, a source driver whose polarity is inverted every gate scan is used. However, in the second embodiment, the source driver has a polarity every gate scan and every source line (one pixel unit). Use the one that reverses.
[0016]
When this source driver is used to perform the transfer driving of FIG. 1, the arrangement state of the liquid crystal layer disturbed by power-on in the reset period 101 can be made uniform in the splay state as in the first embodiment. It is. Further, in the transition voltage application period 102, a large voltage is applied to the counter electrode, and a maximum voltage is applied to the source line that changes in polarity from the source driver for each gate scan and also changes in polarity for each source line. When the gate is turned on by the gate driver at the same timing as in the first embodiment, the pixel electrode potential in the A period is as shown in FIG. 3A, and the pixel electrode potential in the B period is as shown in FIG. become. In FIG. 3, an electric field is generated between the pixel electrodes for each gate scan and between the pixel electrodes for each source line. When these gate direction electric field 301 and source direction electric field 302 are generated, transition nuclei are generated in these portions, and the liquid crystal layer can be bent more quickly than in the driving method of the first embodiment. .
[0017]
In addition, by repeating the period A and the period B in FIG. 1, the pixel electrode in the pixel can be set to a positive polarity potential and a negative polarity potential. Therefore, the liquid crystal layer is further disturbed, and the bend state is shortened in a short period. Can be. As in the first embodiment, the reset period 101 and the transition voltage application period 102 should be repeated twice or more. This is because the bend state may not be completely achieved at a low temperature where it is difficult to bend only with one reset period 101 and transition voltage application period 102.
[0018]
When the driving method according to the second embodiment is used, the entire panel can be completely bent in a shorter time than the driving method according to the first embodiment, and an image can be displayed.
[0019]
(Embodiment 3)
FIG. 4 is a time chart according to the third embodiment. The actual operation will be described below with reference to FIG. Again, to simplify the description, consider a model with three gate lines. POL in FIG. 4 is a signal applied to the source driver. When POL is H, a positive polarity voltage is applied to the source line, and when L is L, a negative polarity voltage is applied to the source line.
[0020]
As in the first embodiment, a reset period 401 is provided in order to change the arrangement state of the liquid crystal layer disturbed by power-on to a uniform spray state.
[0021]
Next, a transition voltage application period 402 is provided in order to make the liquid crystal layer bend completely. In this period, every time the gate is turned on once in FIG. 1, the polarity of the pixel electrode potential of the same pixel is changed from the A period to the B period. In the third embodiment, however, the POL is changed as shown in FIG. By controlling, every time the gate is turned ON twice, the polarity of the pixel electrode potential of the same pixel is changed between the A period and the B period. That is, by controlling the polarity of the potential applied to the source line, it is possible to control the cycle of reversing the polarity of the pixel electrode potential in the pixel (hereinafter referred to as the polarity reversal cycle).
[0022]
FIG. 5 shows the optimum polarity inversion period at each use temperature. From FIG. 5, it can be seen that the optimum value of the polarity reversal period differs depending on each use temperature. Therefore, when the driving method according to the third embodiment is used, the polarity inversion period can be easily varied in accordance with the temperature change. Since the transfer operation is most difficult at low temperatures, when the polarity reversal period is fixed, it is better to set the optimum value at the lowest use temperature.
[0023]
【The invention's effect】
As described above, according to the first embodiment of the present invention, by generating an electric field in the gate direction between the pixel electrodes for each gate scan, the speed at which the liquid crystal layer is bent is increased, and the pixel electrodes in the gate lines are increased. By making + a positive potential and a negative polarity potential, the liquid crystal layer can be further disturbed to bend in a short period of time. In addition, according to the second embodiment of the present invention, the liquid crystal layer is bent from the first embodiment by generating a gate direction electric field and a source direction electric field between the pixel electrodes for each gate scanning and for each source line. The pixel electrode in the gate line is set to a positive polarity potential and a negative polarity potential, whereby the liquid crystal layer is further disturbed and can be bent in a shorter period than in the first embodiment. Further, according to the third embodiment of the present invention, by controlling the polarity of the potential applied to the source line, it is possible to vary the cycle of reversing the polarity of the pixel electrode potential in accordance with the temperature change.
[0024]
By using the present invention, it is possible to provide a liquid crystal display capable of sufficiently responding to a moving image display and a large screen with a high response speed and a wide viewing angle, and lower power compared to a cathode ray tube. It will be kind.
[Brief description of the drawings]
FIG. 1 is a time chart according to the first embodiment of the present invention. FIG. 2 is a configuration diagram of a pixel electrode potential according to the first embodiment of the present invention. FIG. 4 is a time chart according to the third embodiment of the present invention. FIG. 5 is a relationship diagram between operating temperature and polarity inversion period. FIG. 6 is a diagram of the liquid crystal panel used in the embodiment of the present invention. Configuration diagram for one pixel [Explanation of symbols]
101, 401 Reset period 102, 402 Transition voltage application period 103, 403 Normal display period 104, 404 Counter electrode potential 105, 405 First line pixel electrode potential 106, 406 Second line pixel electrode potential 107, 407 Third line Pixel electrode potential 201, 301 gate direction electric field 302 source direction electric field 601 pixel transistor 602 pixel electrode 603 Cgd (capacitance between gate and drain)
604 Cst (storage capacity)
605 Clc (capacity of liquid crystal layer)
606 Source line 607 Gate line 608 Counter electrode 609 Common electrode

Claims (16)

A first thin film transistor formed in a matrix and a pixel electrode connected to the thin film transistor are formed corresponding to intersections of a plurality of source lines to which pixel data is supplied and a plurality of gate lines to which a scanning signal is supplied. The substrate, a second substrate on which a counter electrode facing the first substrate is formed, a liquid crystal layer positioned between the first substrate and the second substrate, and driving the source line In a liquid crystal display device comprising a source driver for driving and a gate driver for driving the gate line, a step of bringing the liquid crystal layer into a splay state, and a voltage for turning on the thin film transistor by sequential scanning from the gate driver to the gate line are provided. The source driver applies a different potential to the source line for each gate scan, and the counter electrode supplies a power to the source line. Method of driving a liquid crystal panel, wherein the relative mean value and a step of the bend state the liquid crystal layer by applying a predetermined voltage. In the liquid crystal display device, the step of bringing the liquid crystal layer into a splay state, the gate driver applies a voltage for sequentially turning on the thin film transistor to the gate line, and the source driver applies the source line to the source line every gate scan. And applying a predetermined voltage to the counter electrode with respect to an average value of the potential applied to the source line to place the liquid crystal layer in a bend state. The method for driving a liquid crystal panel according to claim 1. 3. The liquid crystal panel according to claim 1, wherein in the step of setting the liquid crystal layer to a splay state, a voltage for turning on the thin film transistor is continuously applied from the gate driver to all lines of the gate line. Driving method. 4. The method for driving a liquid crystal panel according to claim 3, wherein a voltage for turning on or off the thin film transistor is applied from the gate driver to the plurality of gate lines at different timings for each line. 4. The method for driving a liquid crystal panel according to claim 3, wherein a voltage for turning on or off the thin film transistor is simultaneously applied to the plurality of gate lines from the gate driver. 6. The method of driving a liquid crystal panel according to claim 5, wherein a voltage for turning on or off the thin film transistor is applied simultaneously to the plurality of gate lines from the gate driver. 3. The liquid crystal panel according to claim 1, wherein in the step of bringing the liquid crystal layer into a splay state, a voltage for turning on the thin film transistor is sequentially applied from the gate driver to the gate line. Driving method. 8. The liquid crystal panel according to claim 3, wherein in the step of setting the liquid crystal layer to a splay state, the liquid crystal panel has a certain period in which the potential of the pixel electrode and the counter electrode is within ± 1V. Driving method. 3. The step of bringing the liquid crystal layer into a bend state, wherein the predetermined voltage applied to the counter electrode is a positive voltage with respect to an average value of potentials applied to the source line. The driving method of the liquid crystal panel as described in 1. 10. The method of driving a liquid crystal panel according to claim 9, wherein in the step of bending the liquid crystal layer, a potential applied to the counter electrode is equal to or greater than a maximum potential applied to the source line. 3. The step of bringing the liquid crystal layer into a bend state, wherein a predetermined voltage applied to the counter electrode is a negative voltage with respect to an average value of potentials applied to the source line. The driving method of the liquid crystal panel as described in 1. 12. The method of driving a liquid crystal panel according to claim 11, wherein in the step of bringing the liquid crystal layer into a bend state, a potential applied to the counter electrode is equal to or lower than a minimum potential applied to the source line. The method for driving a liquid crystal panel according to claim 1, wherein the step of setting the liquid crystal layer to a splay state and the step of setting the liquid crystal layer to a bend state are performed twice or more. In the step of setting the liquid crystal layer in a bend state, the polarity of the potential applied from the source driver to the source line is controlled in response to a temperature change, and the inversion period of the polarity of the potential applied to the pixel electrode is varied. The method for driving a liquid crystal panel according to claim 1, wherein: 15. The method of driving a liquid crystal panel according to claim 14, wherein the inversion period of the polarity of the potential applied to the pixel electrode is set to an optimum value at the lowest temperature at which the liquid crystal display device is used. The liquid crystal display device by the drive method of the liquid crystal panel in any one of Claims 1-15.

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