JP2004004199A - Method for driving liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent display quality in displaying by applying voltage to a liquid crystal while reducing a transient current accompanying the voltage application to prevent air bubbles in a liquid crystal display device. <P>SOLUTION: In the case of obtaining a desired display by applying a voltage to the liquid crystal between a selected scanning electrode and each of signal electrodes, a selection period is divided into a plurality of periods and the applied voltage is varied for each of the divided periods. In this case, the liquid crystal display device is driven to make the voltage applied to the liquid crystal higher when each of the divided periods is switched between themselves. The transient current accompanying the voltage variation is reduced by stepwise elevating the applied voltage for each of the divided periods of the selection period. Consequently air bubbles in the liquid crystal display device are prevented and excellent display quality is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

【００４４】
表１に示すように、本発明の駆動方法で液晶表示装置を駆動することにより、発熱発泡を抑制し、長期間表示品位を保たせることができることがわかる。
【００４５】
【発明の効果】
本発明の駆動方法によれば、液晶に駆動電圧を印加するときに多くの過渡電流が流れることを防止し、液晶表示装置の内部において、液晶分子の向きが不均一である部分や、水分や不純物によって局所的に比抵抗が低下している部分、あるいはスペーサの周囲等で発熱発泡の発生を防止することができる。この結果、良好な表示品位で画像を表示することができる。
【図面の簡単な説明】
【図１】液晶表示装置の例を示す模式的断面図。
【図２】液晶表示装置を駆動する駆動装置の構成例を示すブロック図。
【図３】本発明の駆動方法による駆動波形の例を示す説明図。
【図４】液晶への印加電圧および印加電圧により生じる電流の変化を示す説明図。
【図５】本発明の駆動方法による駆動波形の例を示す説明図。
【図６】本発明の駆動方法による駆動波形の例を示す説明図。
【図７】本発明の駆動方法による駆動波形の例を示す説明図。
【図８】電圧印加にともなう強誘電性液晶分子の挙動を示す模式図。
【図９】従来の駆動方法による液晶への印加電圧により生じる電流の変化を示す説明図。
【符号の説明】
１_Ａ、１_Ｂ　ガラス基板
２_Ａ、２_Ｂ　電極
４　液晶組成物
１１　コントローラ
１２　走査電極ドライバ
１３　信号電極ドライバ
１４　電源装置
１５　液晶表示装置（液晶パネル）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for driving a liquid crystal display device, and more particularly, to a method for driving a liquid crystal display device using liquid crystal having a high driving voltage.
[0002]
[Prior art]
Chiral nematic liquid crystal (cholesteric liquid crystal), ferroelectric liquid crystal, and the like are known as memory liquid crystals. These memory-like liquid crystals transition to a predetermined alignment state when a voltage higher than a threshold is applied. Then, even after no voltage is applied after the transition to the alignment state, the alignment state after the transition is maintained. Therefore, in a liquid crystal display device including a memory-type liquid crystal, a voltage may be applied to the liquid crystal when rewriting display. After a desired display is written by applying a voltage, the written display can be maintained without applying a voltage.
[0003]
A chiral nematic liquid crystal (cholesteric liquid crystal) is sandwiched between a pair of parallel substrates, and the director of the liquid crystal rotates at regular intervals. When arranged in the vertical direction, light of a specific wavelength is reflected. This state is called a planar state. Further, when the helical axes of the plurality of liquid crystal domains are oriented in random directions with respect to the substrate, light of a specific wavelength is not reflected. This state is called a focal conic state. When an absorbing layer is provided on the back surface of the substrate and the liquid crystal is brought into a focal conic state, the color of the absorbing layer can be displayed. To bring the chiral nematic liquid crystal or the like into the planar state or the focal conic state, a predetermined voltage may be applied to each. The liquid crystal in the planar state or the focal conic state maintains the state until the next voltage is applied.
[0004]
In the case of a ferroelectric liquid crystal, when a predetermined voltage is applied, the direction of the ferroelectric liquid crystal molecules changes. FIG. 8 is a schematic diagram showing the behavior of the ferroelectric liquid crystal molecules when a voltage is applied. The state shown on the left side of FIG. 8 is the initial alignment state of the ferroelectric liquid crystal molecules. In the initial alignment state, each liquid crystal molecule faces in the same direction. When a voltage higher than the threshold (here, a positive voltage) is applied to the ferroelectric liquid crystal in the initial alignment state, the direction of the liquid crystal molecules changes as shown on the right side of FIG. Even if the application of the voltage is stopped, the ferroelectric liquid crystal maintains the alignment state on the right side in FIG. When a negative voltage equal to or higher than the threshold is applied to the ferroelectric liquid crystal in this state, the ferroelectric liquid crystal returns to the initial alignment state, and maintains the initial alignment state even after the voltage application is stopped. When a display is performed using a ferroelectric liquid crystal, a ferroelectric liquid crystal is arranged between two polarizing plates whose polarization axes are orthogonal to each other, and the direction of liquid crystal molecules is controlled by changing an applied voltage.
[0005]
The driving voltage of these memory liquid crystals is higher than that of nematic liquid crystals. An antiferroelectric liquid crystal is a liquid crystal that can realize the state of the two liquid crystal molecules shown in FIG. This antiferroelectric liquid crystal also has a higher driving voltage than a nematic liquid crystal.
[0006]
[Problems to be solved by the invention]
When a high driving voltage needs to be used, such as a chiral nematic liquid crystal, a ferroelectric liquid crystal, and an anti-ferroelectric liquid crystal, the following problems have occurred. FIG. 9A is an explanatory diagram illustrating an example of a voltage waveform applied to the liquid crystal. FIG. 9B is an explanatory diagram showing a change in a current caused by applying a voltage. When a voltage is applied to the liquid crystal, a transient current flows immediately after the voltage is applied. When a high voltage (for example, 20 V) is applied to the liquid crystal, the transient current generated immediately after the application of the voltage increases as shown in FIG. 9B. Then, foaming easily occurs in the liquid crystal panel. Foaming occurs in areas where the orientation of liquid crystal molecules is non-uniform (around small foreign substances mixed in the liquid crystal cell, areas where the cell gap becomes uneven, etc.), in areas with low specific resistance, around spacers, etc. Occurs. Hereinafter, this foaming is referred to as exothermic foaming. Exothermic foaming is noticeable in a moisture resistance test.
[0007]
The present invention proposes a method of driving a liquid crystal display device that can prevent heat generation and foaming and obtain good display quality even when the liquid crystal display device must be driven at a relatively high voltage. Aim.
[0008]
[Means for Solving the Problems]
Embodiment 1 of the present invention is a method for driving a liquid crystal display device in which liquid crystal is sandwiched between a plurality of scanning electrodes and a plurality of signal electrodes, wherein the scanning electrodes are scanned while selecting the scanning electrodes, and the selected scanning electrodes are scanned. When applying a voltage to the liquid crystal in order to bring the liquid crystal between the pixel electrode and each signal electrode into a desired state, the selection period of the scanning electrode is divided into a plurality of periods, and the voltage is applied to the liquid crystal every time the divided period is switched. A method for driving a liquid crystal display device, characterized in that the absolute value of the applied voltage is increased.
[0009]
In a second aspect of the present invention, a driving method of a liquid crystal display device in which the lengths of the periods divided from the selection period are equal is input.
[0010]
Embodiment 3 of the present invention provides a method for driving a liquid crystal display device in which the height relationship between the potential of the selected scan electrode and the potential of the signal electrode is reversed each time each divided period is switched.
[0011]
Aspect 4 of the present invention sets the potential of the selected scan electrode alternately to a positive potential higher than a predetermined reference potential and a negative potential lower than the predetermined potential each time each of the divided periods is switched. According to the difference between the effective value voltage during the period in which the potential of the scanning electrode selected in the above is set to the positive potential and the effective value voltage in the period during which the potential of the scanning electrode selected in the selection period is the negative potential, Provided is a method for driving a liquid crystal display device in which the potential of a scan electrode is set to be shifted from a reference potential.
[0012]
In a fifth aspect of the present invention, when n is a natural number, every time n times of scanning of the scanning electrodes for selecting all the scanning electrodes is performed n times, the potential of the selected scanning electrode and the potential of the signal electrode are changed. Provided is a method for driving a liquid crystal display device in which the relationship is reversed.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of a liquid crystal display device driven by the driving method of the present invention. The liquid crystal display device shown in FIG. 1 includes a glass substrate 1 _A , 1 _B , electrodes 2 _A , 2 _B , polymer thin films 3 _A , 3 _B , and a liquid crystal composition (chiral nematic liquid crystal) 4 arranged in a focal conic state. And a liquid crystal panel that stably displays the planar state. Further, a black light absorber 5 is arranged on the back side of the liquid crystal display device. Electrodes ₂ A, _{2 B} are transparent electrodes, respectively. In the following description, it is assumed that the electrode _2A is a signal electrode and the electrode _2B is a scanning electrode. The liquid crystal composition 4 and the electrode 2 _A, 2 and _B may be configured to direct contact.
[0014]
FIG. 2 is a block diagram illustrating a configuration example of a driving device that drives the liquid crystal display device. The controller 11 is instructed to set the potentials of the scanning electrodes 2 _B to the scan electrode driver 12, an instruction to set the potentials of the signal electrodes 2 _A to the signal electrode driver 13. The scanning electrode driver 12 and the signal electrode driver 13 set the potential of each electrode according to an instruction from the controller 11. The power supply 14 supplies necessary voltages to the scan electrode driver 12 and the signal electrode driver 13. The controller 11 switches the potential of each electrode by the scanning electrode driver 12 and the signal electrode driver 13 to shift the chiral nematic liquid crystal 4 arranged in each pixel to a planar state or a focal conic state. Hereinafter, a case will be described as an example where binary display is performed in the planar state and the focal conic state.
[0015]
Next, the operation of the driving device when writing display on the liquid crystal display device 15 will be described. The driving device performs line-sequential scanning while selecting the scanning electrodes _2B one by one, and applies a voltage for shifting the chiral nematic liquid crystal 4 arranged in the pixel of the selected row to the planar state or the focal conic state. The driving device divides each selection period into a plurality of periods. In each of the periods divided from one selection period, the liquid crystal display device 15 is controlled so that the voltage applied to the pixels in the selected row is increased (the absolute value of the voltage is increased) when the period is switched. Drive.
[0016]
FIG. 3 shows an example of a change in the potential set for the scanning electrode and the signal electrode and a change in the voltage applied to the liquid crystal. The scan electrode driver 12 sequentially selects each scan electrode under the control of the controller 11. In the selection period of one scan electrode, the scan electrode driver 12 sets the potentials of the scan electrodes of the selected row and the scan electrodes of the non-selected rows, respectively.
[0017]
When setting the potential of the scanning electrode in the selected row, the scanning electrode driver 12 divides the selection period into a plurality of periods according to the controller 11. Then, the potential of the selected row is set so that the difference (absolute value) between the predetermined reference potential (here, 0 V) and the potential of the selected row is increased in each of the divided periods. In the example shown in FIG. 3, by dividing the selection period in a period of _T 1 through T _3, it sets the potential of the selected row to _{V 1,} -V 2, _{V 3} for each period. Note that V ₁ <V ₂ <V ₃ . The length of each of the divided periods T _{1 to} T ₃ is arbitrary.
[0018]
The signal electrode driver 13 sets the potential of each signal electrode so that the pixels in the selected row are in the planar state or the focal conic state. The potential ± V _p shown in FIG. 3 is the potential of the signal electrode when the liquid crystal between the selected scanning electrode and the signal electrode is brought into the planar state, and ± V _f is the potential of the signal electrode when the liquid crystal is brought into the focal conic state. Potential. Signal electrode driver 13, similarly to the selection period to the scanning electrode driver 12 is divided into a plurality of periods, setting the potential of the signal electrodes in each period V _p and -V p _(or, V _f and -V _f) I do. In Figure 3, shows an example in determining the potential for each period _{-V p, V p, -V p} ( or _{-V f, V f, -V f} ) and. Note _{that the} value of V p, _{V f} defines a voltage _V p, _{V f} as a value also does not affect the liquid crystal state is applied to the liquid crystal 4.
[0019]
As a result, each pixel of the selected row, the voltage of _V 1 + _{V p} (or _V 1 + _{V f)} is applied in period _{T 1.} In the subsequent period _{T 2} voltage _-V 2 -V _p (or _-V 2 -V _f) is applied. Further, the voltage of the next in the period _{T 3 V 3} + _{V p} (or _V 3 + _{V f)} is applied. As described above, every time the period is switched between T ₂ and T ₃ , the height (absolute value) of the voltage applied to the pixel is increased.
[0020]
FIG. 4A shows a voltage applied to the liquid crystal during the selection period shown in FIG. FIG. 4B shows a change in the amount of current caused by the voltage. In FIG. 4, the voltage applied during periods other than the selection period is set to 0 V, ignoring. If the voltage is increased stepwise in each period, a high voltage need not be applied at once. Therefore, although a slight transient current occurs every time the applied voltage is changed, a large amount of transient current as shown in FIG. 9 does not occur because the amount of change in the voltage is small. For this reason, inside the liquid crystal display device 15, generation of heat generation bubbles occurs in a portion where the orientation of liquid crystal molecules is non-uniform, a portion where the specific resistance is locally reduced by moisture or impurities, or around a spacer. Can be prevented. As a result, good display quality can be obtained.
[0021]
In the example shown in FIG. 3, the length of each period obtained by dividing the selection period is arbitrary, but the length of each period may be equal. FIG. 3 shows a case where the selection period is divided into three periods, but the number of divisions is not limited to three.
[0022]
Driving such that the potential of the selected scanning electrode is higher than the potential of the signal electrode is referred to as positive polarity driving. Driving such that the potential of the selected scanning electrode is lower than the potential of the signal electrode is called negative polarity driving. Further, a potential higher than a predetermined reference potential (0 V in this embodiment) is defined as a positive potential, and a potential lower than the predetermined reference potential is defined as a negative potential. The scan electrode driver 12 sets the potential of the selected scan electrode to a positive potential during positive drive, and sets the potential of the selected scan electrode to a negative potential during negative drive.
[0023]
When switching between the positive polarity drive and the negative polarity drive, the effective value voltage (voltage expressed as an effective value) in one of the driving cases may be higher than the effective value voltage in the other driving. FIG. 5 shows drive waveforms when the selection period is divided into four equal parts and the voltages V ₁₁ , −V ₁₂ , V ₁₃ , and −V ₁₄ are applied to the liquid crystal during each period T. _However, a _{V 11 <V 12 <V 13} <V 14. In this case, since the actual voltages (−V ₁₂ , −V ₁₄ ) at the time of the negative polarity driving are higher than the actual voltages (V ₁₁ , V ₁₃ ) at the time of the positive polarity driving, the effective value voltage is also lower in the case of the negative polarity driving. Is higher. By shifting the potential of the scanning electrodes in the non-selected rows from the reference potential, bias of the effective value voltage in the entire one frame period may be prevented. That is, when the effective value voltage during the negative drive is increased during the selection period, the effective value voltage during the positive drive is increased during the non-selection period, and either one of the effective values is applied during the entire frame period. May not be increased.
[0024]
The calculation of the effective value of the voltage represented by the rectangular wave will be described. When calculating an effective value voltage during positive driving (a period during which the potential of the selected row is set to a positive potential) within a certain period, application of each real voltage to the positive driving time for each real voltage during positive driving Determine the time ratio and multiply that value by the square of each actual voltage. By calculating this value for each actual voltage and determining the square root of the sum, an effective value voltage during positive polarity driving can be obtained. For example, the positive drive time in the selection period shown in FIG. 5 is 2 · T. The ratio of the application time of the actual voltage _{V 11} for this time is T / (2 · T) = 1/2. When multiplied by the square of the actual voltage _{V 11} to this value becomes (1/2) · _{V 11} ^2. Doing calculations Similarly, the actual voltage _{V 13} (1/2) a · _{V 13} ^2. When the square root of the sum of the results calculated for each actual voltage is obtained, the effective value voltage (referred to as _{Vrms +} ) at the time of positive polarity driving is as shown in Expression 1.
[0025]
^{_{V rms + = √ ((V}} 11 2 + V 13 2) / 2) Equation 1
[0026]
The calculation of the effective value voltage at the time of the negative polarity driving can be similarly performed. That is, when calculating the effective value voltage during the negative drive in a certain period (a period during which the potential of the selected row is set to a negative potential), the application of each actual voltage to the negative drive time is performed for each actual voltage during the negative drive. Determine the time ratio and multiply that value by the square of each actual voltage. By calculating this value for each actual voltage and calculating the square root of the sum, an effective value voltage ( _referred to as _Vrms- ) at the time of negative polarity driving can be obtained. Equation 2 is obtained when _Vrms- in the selection period shown in FIG. 5 is obtained.
[0027]
^{_{V rms- = √ ((V 12}} 2 + V 14 2) / 2) Equation 2
[0028]
Figure 6 shows a drive waveform when higher by V _n than the reference potential the potential of the scan electrodes in the non-selection period (0V). By increasing the potential of the scan electrode in the non-selection period in one frame period, the effective value voltage in the positive drive becomes higher than the effective value voltage in the negative drive in the non-selection period. As a result, even during the selection period, even if the effective value voltage at the time of negative drive is higher than the effective value voltage at the time of positive drive, there is no bias in the entire one frame period. Figure 5 and 6 will be explained as an example for the method of calculating V _n. First, a difference between _{V rms +} and _{V rms-within} the selection period _{(the A rms). Arms} is the difference between the effective value voltage during positive drive and the effective value voltage during negative drive. If the effective value voltage in the non-selection period (T _n ) is increased by _Arms , the bias in the entire one frame period is eliminated.
[0029]
Calculating the increase in effective voltage due to the increased potential V _n across unselected entire period T _n. The ratio of the period to increase the potential _{V n} for the non-selection period _{T n} is _T n _{/ T} n = 1. A V _n ² is multiplied by the square of this value to the potential was raised (voltage) V _n. Here, since the thinking non-selection period to raise the potential (voltage) V _n as one period, by calculating the square root of V _n ^2, the increase in the effective value due to the rise in the potential V _n is determined . This increase is, deviation of the effective value is eliminated equal to A _rms. Accordingly, the potential V _n to shift with respect to the reference potential has a value shown in Equation 3.
[0030]
V _n = √ (A _rms ² ) Equation 3
[0031]
The higher towards the effective voltage of the negative polarity driving in the selection period, the potential of the scan electrodes in the non-selection period (the non-selected rows of the scanning electrodes) may be increased V _n than the reference potential. Also, the higher the better the effective voltage of the positive polarity driving in the selection period, the potential of the scan electrodes in the non-selection period (the non-selected rows of the scanning electrodes) may be V _n lower than the reference potential.
[0032]
Incidentally, when driven in this way, although the pixels of the non-selected row voltage of ± V _{f +} V _n or ± V _{p +} V _n is applied, the value of these voltages does not affect the state of the liquid crystal 4 _Vp and _Vf are determined so that
[0033]
In the drive waveforms shown in FIGS. 3 and 6, an example in which the positive drive and the negative drive are switched within the selection period has been described. However, the positive drive and the negative drive may be switched every frame period. . FIG. 7 shows an example of the driving waveform in this case. In the first frame period, the controller 11 instructs the scan electrode driver 12 and the signal electrode driver 13 to perform positive drive. In this case, the signal electrode driver 13 during the selection period, setting the potential of the signal electrodes to -V _p or -V _f. On the other hand, the scan electrode driver 12 divides the selection period into a plurality of periods in accordance with the controller 11, and sets the potential of the selected row such that the difference (absolute value) between the reference potential and the potential of the selected row increases for each of the divided periods. Set. At this time, the potential set for each period is a positive potential. As a result, the voltage applied to the pixels in the selected row increases while maintaining the polarity each time the divided periods are switched.
[0034]
In the next frame period, the controller 11 instructs the scan electrode driver 12 and the signal electrode driver 13 to perform a negative drive. In this case, the signal electrode driver 13 sets the potential of each signal electrode to _Vp or _Vf during the selection period. On the other hand, the scan electrode driver 12 divides the selection period into a plurality of periods in accordance with the controller 11, and sets the potential of the selected row such that the difference (absolute value) between the reference potential and the potential of the selected row increases for each of the divided periods. Set. Note that the potential set for each period is a negative potential. As a result, the voltage applied to the pixels in the selected row increases while maintaining the polarity each time the divided periods are switched. Although FIG. 7 shows a case in which the positive drive and the negative drive are switched every frame period, the drive may be switched every n frame periods (n is a natural number). Further, in one frame period, scanning of the scanning electrodes for selecting all the scanning electrodes once is performed once.
[0035]
Although an example in which binary display is performed is described here, halftone display may be performed by receiving a plurality of potentials set to the signal electrodes. For example, in the example shown in FIG. 3, the signal electrode driver 13 is ± _{V p,} in addition to ± _{V f,} more _{V f V p} less (or, -V _p or -V _f below) the potential of the set, planar state A halftone display between and the focal conic state may be performed. Even in the case where the potential of the signal electrode is set to a potential corresponding to the halftone as described above, it is possible to prevent heat generation and foaming by increasing the height of the applied voltage every time the divided periods are switched.
[0036]
FIG. 1 shows a case where a chiral nematic liquid crystal is used as the liquid crystal composition 4, but the liquid crystal composition 4 is not limited to a chiral nematic liquid crystal. As the liquid crystal composition 4, a cholesteric liquid crystal, a ferroelectric liquid crystal, an antiferroelectric liquid crystal, or the like may be used. When the driving method of the present invention is applied to a liquid crystal display device using a liquid crystal that requires a high driving voltage (for example, a driving voltage of 15 V or more) as the liquid crystal composition 4, heat generation and bubbling can be prevented and good display quality can be obtained. Obtainable. Further, the driving method of the present invention may be applied to a liquid crystal display device including a TN liquid crystal or an STN liquid crystal that does not generate heat even when driven by a conventional driving method. Note that the configuration of the liquid crystal display device 15 may be changed according to the liquid crystal composition 4. For example, when using a ferroelectric liquid crystal or anti-ferroelectric liquid crystal, without providing the light-absorbing member 5 on the liquid crystal panel, a polarizing plate is provided on the glass substrates 1 _A, 1 _B.
[0037]
When a chiral nematic liquid crystal is used as the liquid crystal composition 4, one of a voltage for setting a planar state and a voltage for setting a focal conic state is applied to each pixel in a selected row. When a ferroelectric liquid crystal is used as the liquid crystal composition 4, a voltage for changing the alignment state or a voltage equal to or lower than a predetermined threshold is applied to each pixel in the selected row to display a desired image. When a voltage lower than a predetermined threshold is applied to the pixels in the selected row, the potential of the signal electrode may be set so that the potential difference between the selected scanning electrode and the pixel is lower than the predetermined threshold.
[0038]
【Example】
[Example 1] A glass substrate with ITO (Indium Tin Oxide) having a sheet resistance of 20Ω was etched into a predetermined display pattern to form a pair of glass substrates. The MIC and the alignment film were transferred and fired on each substrate to form a thin film. The MIC is an abbreviation for a middle coat film, and is an insulating film. An empty cell was created by disposing a sealing material around the pair of substrates. Further, a chiral nematic liquid crystal was injected into the empty cell, thereby producing a liquid crystal display device.
[0039]
This liquid crystal display device was subjected to a moisture resistance test. In the moisture resistance test, the liquid crystal display device was allowed to stand still in a bath at a temperature of 80 ° C. and a humidity of 90%, and after a predetermined time had elapsed, the liquid crystal display device was taken out of the bath to determine whether or not good display was obtained. It was done by confirmation. Immediately before putting in the tank, an image was displayed on the liquid crystal display device with the driving waveforms shown in FIGS. Also, the liquid crystal display device was taken out of the tank 72 hours, 144 hours, 300 hours, and 504 hours after the liquid crystal display device was allowed to stand still in the tank, and images were taken with the driving waveforms shown in FIGS. Displayed. In each case, good display was obtained. The contrast was also good.
[0040]
[Example 2] A liquid crystal display device was prepared in the same manner as in Example 1 using a glass substrate with ITO having a sheet resistance of 4Ω, and a moisture resistance test was performed in the same manner as in Example 1. However, when an image was displayed, it was driven with the drive waveform shown in FIG. Good display was obtained similarly to the case of Example 1. The contrast was also good. This shows that good display can be obtained even when the resistance value of ITO is reduced.
[0041]
Comparative Example The same liquid crystal display device as in Example 1 was prepared, and a moisture resistance test was performed in the same manner as in Example 1. However, when displaying an image, the voltage applied to the liquid crystal was not changed stepwise but driven so that the voltage was applied with the waveform shown in FIG. 9A. In this case, good display was obtained immediately before the liquid crystal display device was put in the tank and 72 hours after the liquid crystal display device was put in the tank, but when driven after 144 hours, foaming occurred and good display was not obtained. .
[0042]
Table 1 shows the results of Examples 1 and 2 and Comparative Example. In Table 1, “○” indicates that good display was obtained without foaming. “X” indicates that foaming occurred and good display was not obtained.
[0043]
[Table 1]

[0044]
As shown in Table 1, it can be seen that by driving the liquid crystal display device by the driving method of the present invention, heat generation and foaming can be suppressed, and display quality can be maintained for a long period of time.
[0045]
【The invention's effect】
According to the driving method of the present invention, it is possible to prevent a large amount of transient current from flowing when a driving voltage is applied to a liquid crystal, and in a liquid crystal display device, a portion where directions of liquid crystal molecules are non-uniform, moisture, or the like. It is possible to prevent the occurrence of heat generation and foaming in a portion where the specific resistance is locally reduced due to impurities, or around a spacer. As a result, an image can be displayed with good display quality.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating an example of a liquid crystal display device.
FIG. 2 is a block diagram illustrating a configuration example of a driving device that drives a liquid crystal display device.
FIG. 3 is an explanatory diagram showing an example of a driving waveform according to the driving method of the present invention.
FIG. 4 is an explanatory diagram showing an applied voltage to a liquid crystal and a change in current caused by the applied voltage.
FIG. 5 is an explanatory diagram showing an example of a driving waveform according to the driving method of the present invention.
FIG. 6 is an explanatory diagram showing an example of a driving waveform according to the driving method of the present invention.
FIG. 7 is an explanatory diagram showing an example of a driving waveform according to the driving method of the present invention.
FIG. 8 is a schematic diagram showing the behavior of ferroelectric liquid crystal molecules when a voltage is applied.
FIG. 9 is an explanatory diagram showing a change in current caused by a voltage applied to a liquid crystal by a conventional driving method.
[Explanation of symbols]
_Reference Signs List 1 _A , 1 _B glass substrate 2 _A , 2 _B electrode 4 Liquid crystal composition 11 Controller 12 Scanning electrode driver 13 Signal electrode driver 14 Power supply device 15 Liquid crystal display (liquid crystal panel)

Claims (5)

A method for driving a liquid crystal display device that sandwiches liquid crystal between a plurality of scanning electrodes and a plurality of signal electrodes,
Scan the scan electrode while selecting the scan electrode,
When applying a voltage to the liquid crystal in order to bring the liquid crystal between the selected scan electrode and each signal electrode into a desired state, the selection period of the scan electrode is divided into a plurality of periods, and each of the divided periods is A driving method of a liquid crystal display device, wherein the absolute value of a voltage applied to a liquid crystal is increased each time switching is performed. 2. The driving method for a liquid crystal display device according to claim 1, wherein the lengths of the divided periods are made equal. 3. The driving method for a liquid crystal display device according to claim 1, wherein the level relationship between the potential of the selected scanning electrode and the potential of the signal electrode is reversed each time each of the divided periods is switched. Each time the divided periods are switched, the potential of the selected scan electrode is alternately set to a positive potential higher than a predetermined reference potential and a negative potential lower than a predetermined potential,
In accordance with the difference between the effective value voltage during the period when the potential of the selected scan electrode is positive during the selection period and the effective value voltage during the period when the potential of the selected scan electrode is negative during the selection period, 4. The driving method for a liquid crystal display device according to claim 3, wherein the potential of the scanning electrode in the selected row is set to be shifted from the reference potential. When n is a natural number, every time n times of scanning of a scanning electrode for selecting all of the scanning electrodes is performed n times, the height relationship between the potential of the selected scanning electrode and the potential of the signal electrode is reversed. The method for driving a liquid crystal display device according to claim 1 or 2.

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