JP3453987B2 - Driving method of liquid crystal display device, liquid crystal display device and electronic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a liquid crystal display device, a liquid crystal display device and electronic equipment.

[0002]

2. Description of the Related Art As a conventional method for driving a liquid crystal display device,
As a driving method for sequentially scanning a plurality of scanning electrodes while simultaneously selecting them, there are driving methods shown in US Pat. No. 5,262,881 and International Published Application WO93 / 18501.

[0003]

In the driving method for simultaneously selecting a plurality of scanning electrodes as described above, in the case of a frame gray scale in which gray scales are displayed by turning on and off for each frame,
There is a difference in the luminance change of each pixel due to the gradation pattern that indicates the combination of turning on and off each pixel and the selection pattern that indicates the combination of the polarities of the selection signals of the scanning signals, and the combination of the gradation pattern and the selection pattern It was discovered that the flickering could be intense due to.
The details will be described below.

FIG. 11 shows scanning signals applied to the scanning electrodes when four lines are simultaneously selected. The scanning signals X1 to X6 are the scanning electrodes X1 to X of the liquid crystal display of FIG.
6, the luminance change of the pixel A when the 2/3 gray scale of the gray scale pattern 1 of FIG. 1 is displayed is shown by T1, and the luminance change of the pixel B is shown by T2.

As indicated by T1 and T2, the pixel A has a very large difference in luminance change in a three-frame period in which the grayscale pattern makes one turn, resulting in large flicker. Also,
Pixel B has a small difference in luminance change and has little flicker. For this reason, the difference in luminance change between the pixel A and the pixel B becomes large, and the flickering becomes more noticeable, and the display quality is deteriorated.

[0006]

According to the method of driving a liquid crystal display device of the present invention, a plurality of scans to which a scanning signal is applied during a selection period and a scanning signal is applied during a non-selection period. The scanning having electrodes, a plurality of signal electrodes to which a data signal based on display data is applied, and a display element driven by the scanning signal and the data signal, and grouped into a plurality of groups. Among the electrodes, the scanning electrodes belonging to the same group are simultaneously selected by the selection signals which are orthogonal to each other in a certain period, and the selection period is divided into p (p is an integer of 2 or more) sub-selection periods, A driving method of a liquid crystal display device for performing gray scale display by frame gray scale, wherein a selection pattern for defining a pattern of the selection signal applied to the simultaneously selected scan electrodes in one frame period. A plurality of selection patterns in which the patterns of the selection signals applied to the scan electrodes selected at the same time are partially different for each sub-selection period, A gradation pattern that defines ON / OFF states in a plurality of frame periods in which gradation is expressed by the frame gradation of each display element that constitutes a basic unit that expresses a gradation, and corresponds to each selection pattern. A plurality of gradation patterns in which the ON and OFF states in the frame period of each display element forming the basic unit are partially different from each other, and the selection pattern and the gradation pattern corresponding thereto are provided. It is characterized in that the groups are switched to drive the gradation display.

With this structure, it is possible to improve the contrast of the liquid crystal display device, effectively suppress the flicker, and improve the display quality.

The driving method of the liquid crystal display device according to the present invention is the same as the driving method of such a liquid crystal display device,
In each of the display elements, the number of consecutive same states among the ON and OFF states is the minimum for each period in which the gradation pattern makes one turn, and the same state between the display elements in each of the gradation patterns. It is characterized in that the difference in the number of consecutive is minimized.

Further, the driving method of the liquid crystal display device according to the present invention is characterized in that, in such a driving method of the liquid crystal display device, the gradation pattern is such that the voltage level of the data signal is minimum.

Further, according to the driving method of the liquid crystal display device of the present invention, in the driving method of the liquid crystal display device, when the selection pattern of the scanning signal is switched,
The gradation pattern is switched according to the switching.

Further, according to the driving method of the liquid crystal display device of the present invention, in the driving method of such a liquid crystal display device, the gradation pattern is provided for each block of the display screen at which display data switching timing is different. It is characterized by switching.

Further, a liquid crystal display device of the present invention is characterized in that it is a liquid crystal display device using any one of the methods for driving a liquid crystal display device described above.

Further, the liquid crystal display device according to the present invention is
A plurality of scanning electrodes to which a selection signal is applied during a selection period and a scanning signal which is applied during a non-selection period are applied; and a plurality of signal electrodes to which a data signal based on display data is applied, Of the scanning electrodes grouped into a plurality of groups, each of which has a display element driven by a scanning signal and the data signal, and the scanning electrodes belonging to the same group are orthogonal to each other in a certain period. A liquid crystal display device, which is simultaneously selected by a signal, is divided into p (p is an integer of 2 or more) sub-selection periods, and performs gradation display by frame gradation,
A selection pattern defining a pattern of the selection signal applied to the scan electrodes selected at the same time in one frame period, the pattern of the selection signal applied to the scan electrodes selected at the same time in each sub-selection period. In a plurality of frame periods in which the gradation is expressed by the frame gradation of each display element that forms a basic unit that expresses gradation by the frame gradation. It is a gradation pattern that defines the on / off state, and the on / off states in the frame period of each display element forming the basic unit are partially different corresponding to the selection patterns. The selection pattern switching means having a plurality of the gradation patterns and for switching the selection patterns, and the gradation pattern selection signal Characterized by comprising a gradation pattern switching means for gradation display driving by switching the set of the gradation pattern corresponding to the pattern.

Further, the liquid crystal display device according to the present invention is
In such a liquid crystal display device, a gradation pattern switching unit for switching the gradation pattern and a gradation data conversion unit are provided for each block of the display screen at which display data switching timing is different. Characterize.

Further, the electronic equipment of the present invention is characterized in that it is an electronic equipment equipped with any one of the above liquid crystal display devices.

[0016]

DETAILED DESCRIPTION OF THE INVENTION

(Embodiment 1) Embodiment 1 is a drive system in which scanning electrodes are sequentially selected while simultaneously selecting scanning electrodes for every four lines.
A case will be described in which four gradations are displayed by frame gradations in which gradations are displayed by turning pixels on and off for each frame.

FIG. 1 is a diagram showing a gradation pattern for displaying 4 gradations, which expresses 4 gradations in 3 frame periods with 3 × 4 pixels as a basic unit. Three types of patterns 1 to 3 are taken as an example. And
In the basic unit of 3 × 4 pixels, four vertical pixels correspond to four lines that are simultaneously selected, and the gradation pattern is repeated every three pixels in the horizontal direction. In the figure showing each gradation pattern, 1F, 2F, and 3F represent frame periods, and 0/3,
1/3, 2/3, and 3/3 represent gradation levels.

Further, FIG. 2 is a diagram showing the polarities of the selection signals of the scanning signals and shows four types of selection patterns 1 to 4 as an example. Then, 1f to 4f represent each field in one frame period, and Xa to Xd represent four lines to be selected simultaneously.

By using the optimum combination of the gradation patterns shown in FIG. 1 and the selection patterns shown in FIG. 2, gradation display with less flicker can be realized.

FIG. 3 is a diagram showing scanning signal and pixel luminance change when gradation display is performed by the combination of the gradation pattern 1 of FIG. 1 and the selection pattern 1 of FIG. 2, and the portion indicated by A is the selection signal. The part indicated by B is the non-selection signal.

The scanning signals X1 to X6 of FIG. 3 are applied to the scanning electrodes X1 to X6 of the liquid crystal display of FIG. 10, and the four lines of X1 to X4 that are simultaneously selected have the polarity of the selection signal of the first frame. The polarity is as shown in pattern 1 of FIG. 1, the second frame has the opposite polarity to the first frame, the third frame has the opposite polarity to the second frame, and the polarity is inverted for each frame. The polarity inversion cycle can be changed in each frame, every n (n is an integer of 1 or more) field, every n selection period, or the like. This also applies to other embodiments.

The change in luminance of the pixel A when the liquid crystal display displays 2/3 gradation is shown in T1 of FIG.
The brightness change of the pixel B is shown at T2. Here, the pixel A is the pixel with the smallest luminance change, and the pixel B is the pixel with the largest luminance change. In this way, the difference in the luminance change between the pixel with a small luminance change and the pixel with a large luminance change can be reduced, and the amplitude of the maximum luminance change can also be reduced, and the flicker can be reduced.

(Embodiment 2) Embodiment 2 is an embodiment in which the driving method is the same as that of Embodiment 1 and the combination of the gradation pattern and the selection pattern is changed.

FIG. 4 is a diagram showing the change in the scanning signal and the luminance of the pixel when the gradation display is performed by the combination of the gradation pattern 2 in FIG. 1 and the selection pattern 3 in FIG. The part indicated by B is the non-selection signal.

The scanning signals of X1 to X6 of FIG. 4 are applied to the scanning electrodes X1 to X6 of the liquid crystal display of FIG. 10, and the four lines of X1 to X4 selected at the same time have the polarity of the selection pulse of the first frame. The polarity is as shown in pattern 3 of FIG. 1, the second frame has a polarity opposite to that of the first frame, the third frame has a polarity opposite to that of the second frame, and the polarity is inverted for each frame.

The change in the luminance of the pixel B when the liquid crystal display displays 2/3 gradation is shown in T1 of FIG.
The change in luminance of the pixel C is shown at T2. Here, the pixel B is the pixel having the largest luminance change, and the pixel C is the pixel having the smallest luminance change. In this way, the difference in the luminance change between the pixel with a small luminance change and the pixel with a large luminance change can be reduced, and the amplitude of the maximum luminance change can also be reduced, and the flicker can be reduced.

Further, as other examples for reducing the flicker by combining the gradation pattern and the selection pattern, the gradation pattern 1 of FIG. 1 and the selection pattern 2 of FIG. 2 and the gradation pattern 2 of FIG. 1 and FIG. There are several combinations such as the selection pattern 4 of FIG. 1, the gradation pattern 3 of FIG. 1 and the selection pattern 3 of FIG. 2, and the gradation pattern 3 of FIG. 1 and the selection pattern 4 of FIG.

Thus, by optimizing the combination of the gradation pattern and the selection pattern, it is possible to suppress the flicker in the frame gradation and improve the display quality.

(Embodiment 3) Embodiment 3 is a drive system in which scanning electrodes are sequentially selected while simultaneously selecting scanning electrodes by four lines, and a frame is displayed in gray scale by turning on and off pixels for each frame. A case will be described in which a combination of selection patterns is replaced every few lines in the case of displaying four gradations by gradation.

FIG. 5 shows the polarities of the selection signals when the combination of the selection patterns is changed every 16 lines for the scanning electrodes. 1F, 2F and 3F represent frame periods, 1f to 4f represent field periods within one frame period, X1 to X4 apply the selection signal shown in FIG. 5 to the scan electrodes X1 to X4 in FIG. 10, and X17 to X20 is shown in FIG.
5 is applied to the scan electrodes X17 to X20 of the same, and X33 to X36 are scan electrodes X33 to X3 of FIG.
6 is applied with the selection signal shown in FIG. 5, and X49 to X52 are applied with the selection signal shown in FIG. 5 to the scan electrodes X49 to X52 shown in FIG. Scan signals of the same selection pattern combination are applied to the scan electrodes X1 to X16 of FIG. 10, scan signals of the same selection pattern combination are applied to the scan electrodes X17 to X32, and scan electrodes X33 to X48. Scan signals of the same combination of selection patterns are applied, scan signals of the same combination of selection patterns are applied to the scan electrodes X49 to X64, and scan signals of the same combination of selection patterns of scan electrodes X1 to X16 are applied to the scan electrodes X65 to X80. A scanning signal is applied, and as described above, the combinations of the selection patterns of the scanning electrodes are changed every 16 lines, and four kinds of selection patterns are sequentially switched and repeated.

As described above, when the selection pattern of the scanning signal changes due to the scanning electrodes, it is necessary to switch the gradation pattern according to the change of the selection pattern.

Therefore, the gradation pattern may be selected in accordance with each selection pattern from the optimum combination of the gradation pattern and the selection pattern shown in the first and second embodiments.
The gradation pattern 1 of FIG. 1 is used for the selection patterns X1 to X4 of FIG. 5, the gradation pattern 2 of FIG. 1 is used for the selection patterns of X17 to X20 of FIG. 5, and the gradation pattern X3 of FIG.
For the selection pattern of 3 to X36, the gradation pattern 1 of FIG.
When the selection pattern of X49 to X52 in FIG. 5 is used, the gradation pattern 2 in FIG. 1 is used.

The control circuit for selecting the gradation pattern according to the selection pattern will be described. FIG. 6 is a block diagram of the control circuit. Display data and a control signal 607 from a computer or the like are input to the control circuit 600.
The display data is stored in the data storage unit 601 every three frames, and the display data is read from the data storage unit 601 in synchronization with the signal generated by the control signal generation unit 602 and transferred to the gradation data conversion unit 604.

In the scan data generating means 603, the selection pattern switching means 606 selects a selection pattern and transfers the data 612 of the selection pattern to the scan driver. Then, the selection pattern switching unit 606
Of the gradation pattern selection signal 614 of the gradation data conversion means 6
Transfer to 04. The gradation data conversion unit 604 selects an optimum gradation pattern that matches the selection pattern according to the selection signal 614, transfers the ON / OFF gradation data 609 to the calculation unit 605 according to the gradation pattern, and calculates the calculation unit 6
In 05, it is converted into data for simultaneous selection of 4 lines.

As described above, by selecting the optimum gradation pattern according to the change of the selection pattern, it is possible to reduce the display unevenness and suppress the flicker.

(Fourth Embodiment) A fourth embodiment will be described by exemplifying a case where the data storage means has a memory capacity of only one screen.

FIG. 9 is a diagram showing a data driver used in the method of driving the liquid crystal display device according to the fourth embodiment. The fourth embodiment will be described using a liquid crystal display device having 240 scanning electrodes and 4 simultaneous selection lines.

The data driver 900 shown in FIG. 9 includes a control means 901, a buffer means 903, and a data storage means 90.
4, gradation data conversion means 905, and decoding means 90
6 and drive means 907.

The buffer means 903 functions to buffer four lines of display data transferred to the data driver. The data storage unit 904 has a storage capacity for one screen, and stores the display data for four lines buffered by the buffer unit, and at the same time, the display data is read out by four lines and read out. The display data is converted by the gradation data conversion unit 905 into gradation data according to the gradation pattern and transferred to the decoding unit 906. The decoding unit 906 converts the data signal from the selection pattern of the scanning signal and the gradation data. It is determined and transferred to the drive means 907, and the data signal is output from the drive means to each signal electrode.

Since the data storage means 904 of the fourth embodiment has a memory capacity of only one frame, the timing of writing / reading the display data to / from the data storage means 904 is different. FIG. 8 is a diagram showing the timing of writing / reading the display data to / from the data storage means 904 of the data driver 900 of FIG. 9 and the timing of switching the display data.

The pulse voltage to the pulse voltage of the frame signal 801 in FIG. 8 is one frame period, and four gradations are expressed using three frame periods. In the 1st frame shown in 1F, the display data from the 1st line to 2nd as shown in 803.
The data storage means 904 is sequentially written up to the 40th line, and at the same time, as shown in 804, four lines are sequentially read from the data storage means 904 in order from the 1st line to the 240th line. in this way,
Reading of display data for one screen is completed in one field period, and this reading operation is repeated four times in one frame period.

As described above, since the display data write cycle and the display data cycle are different from each other, in the display screen shown in FIG.
The switching timing of the display data is deviated between the parts B, C, and C. The switching timing of the display data at each of the parts a, b, and c is shown at 805 in FIG. 805
A, b, and c indicate the respective places on the display screen, 0 in the upper row represents the display data of the previous frame, 1 represents the display data rewritten in the 1F period, and 1 in the lower row, 1, 2, Three
Indicates which frame of the gradation pattern is displayed in gradation in three frame periods. Then, for example, in the 2f period of 1F, the display data written in the 1F period becomes the data of the gradation pattern of the first frame, and the b portion shows the display data of the previous frame and the data of the gradation pattern of the third frame. Which indicates that part c is the same as part b.

As described above, in the part a, the display data is switched between 1f and 2f in the period 1F for rewriting the display data, and in the part b, the display data is switched between 2f and 3f in the period 1F for rewriting the display data. The display data is rewritten in the c section.
The display data is switched between f.

As described above, when the display data switching timing is different for each place in one screen, it is necessary to change the combination of the gradation patterns in accordance with it.

Here, the case of driving by the selection pattern shown in the first embodiment will be described.

The selection pattern of the first embodiment is the selection pattern 1 of FIG. However, since the display data is switched between 1f and 2f of 1F in the part a, the selection pattern between the switching of the display data and the switching becomes the selection pattern 3, and this selection pattern 3 The gradation pattern 2 is selected from among the optimum gradation patterns. In part b, the display data is switched between 2f and 3 on 1F.
Since it occurs during the period f, the selection pattern between the switching of the display data looks like the selection pattern 2, and the gradation pattern 1 is selected from the optimum gradation patterns for this selection pattern 2. Choose. In the part c, the display data is switched between 3f and 4f of 1F, so the selection pattern between the switching of the display data and the switching is as shown in the selection pattern 4, which is most suitable for this selection pattern 4. The gradation pattern 2 is selected from among the gradation patterns.

As described above, since the display data switching timing is different for each location in one screen, it is necessary to switch the gradation pattern for each location. Therefore,
A gradation pattern switching unit 902 is provided in the control circuit 901 of FIG. 9, and this gradation pattern switching unit 902 detects which scan electrode the display data is being read out, and according to the detection result. A selection signal for selecting a gradation pattern is transferred to the gradation data conversion means 905, and the gradation data conversion means selects an optimum gradation pattern by this selection signal.

As described above, even when the memory capacity of the data accumulating means has only one screen, an optimum gradation pattern can be obtained according to the difference in the switching timing of the display data at each place in one screen. By switching, it is possible to suppress the flickering of the screen and improve the display quality.

In the fourth embodiment, the control unit 901, the buffer unit 903, the data storage unit 904, the grayscale data conversion unit 905, and the decoding unit 906 are included in the data driver, but all or one of them is included. The section may be external to the data driver.

(Embodiment 5) A liquid crystal display device was manufactured by using the method for driving a liquid crystal display device as shown in Embodiments 1 to 4.
When evaluated, flicker on the screen was suppressed, display quality was improved, the display screen was easier to see, and fatigue was reduced.

By using these liquid crystal display devices as display devices for electronic equipment such as small portable terminals and personal computers, electronic equipment with relatively low cost and good display quality can be realized.

The control circuit, the data driver, and the scan driver for driving these liquid crystal display devices are drive circuits which are indispensable for realizing these liquid crystal display devices.

Although the driving method of the liquid crystal display device according to the present invention has been described as an example in which four scanning electrodes are simultaneously selected, the number of scanning electrodes to be simultaneously selected is not limited to this, and how many scanning electrodes are selected. But it can be applied.

Also, with respect to the number of gradations, four gradations are taken as an example, but this can be applied to any gradation.

The same method can be applied to a combination with a pulse width gradation and a combination with a voltage gradation.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a gradation pattern of a driving method of a liquid crystal display device according to the present invention.

FIG. 2 is a diagram showing an example of a selection pattern of a driving method of a liquid crystal display device according to the present invention.

FIG. 3 is a diagram showing an example of a scanning signal and a luminance change of a pixel in a method of driving a liquid crystal display device according to the present invention.

FIG. 4 is a diagram showing an example of a scanning signal and a luminance change of a pixel in a driving method of a liquid crystal display device according to the present invention.

FIG. 5 is a diagram showing an example of a selection pattern of a driving method of a liquid crystal display device according to the present invention.

FIG. 6 is a block diagram showing an example of a control circuit of a driving method of a liquid crystal display device according to the present invention.

FIG. 7 is a diagram for explaining the switching timing of display data in the driving method of the liquid crystal display device according to the present invention.

FIG. 8 is a diagram showing a write / read timing of display data to / from a data storage means and a display data switching timing in a method of driving a liquid crystal display device according to the present invention.

FIG. 9 is a diagram showing a configuration of a data driver of a method for driving a liquid crystal display device according to the present invention.

FIG. 10 illustrates a structure of a liquid crystal display device.

FIG. 11 is a diagram showing an example of a scanning signal and a luminance change of a pixel in a comparative example.

[Explanation of symbols]

1F, 2F, 3F each frame period 1f, 2f, 3f, 4f Each field period 100 liquid crystal display 101 Data driver 102 scan driver 103 scanning electrode 104 signal electrode 600 control circuit 601 Data storage means 602 control signal generating means 603 Scan data generating means 604 gradation data conversion means 605 Calculation means 606 selection pattern switching means 900 data driver 901 control means 902 gradation pattern switching means 903 buffer means 904 data storage means 905 gradation data conversion means 906 Decoding means 907 drive means

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Claims (9)

(57) [Claims] 1. A plurality of scan electrodes to which a selection signal is applied during a selection period and a scanning signal which applies a non-selection signal during a non-selection period are applied, and a plurality of scan electrodes to which a data signal based on display data is applied. Of the scan electrodes grouped into a plurality of groups, the scan electrodes having a signal electrode and a display element driven by the scan signal and the data signal are orthogonal to each other in a certain period. Are selected at the same time by the above selection signal, the selection period is divided into p (p is an integer of 2 or more) sub-selection periods, and gradation display is performed by frame gradation. A selection pattern that defines a pattern of the selection signal applied to the scan electrodes that are simultaneously selected in one frame period, and is simultaneously selected in each of the sub-selection periods. The frame floor of each display element that has a plurality of selection patterns in which the patterns of the selection signals applied to the scan electrodes are partially different, and that constitutes a basic unit that expresses gradation by the frame gradation. A gradation pattern that defines an on / off state in a plurality of frame periods in which gradation is represented by a key, and each display element that constitutes the basic unit is turned on in a frame period in correspondence with each selection pattern. , A liquid crystal display having a plurality of gradation patterns in which OFF states are partially different, and gradation display driving is performed by switching a set of the selection pattern and the gradation pattern corresponding thereto. Device driving method. 2. The method of driving a liquid crystal display device according to claim 1, wherein the number of consecutive same states among the on and off states of each of the display elements is minimum for each period in which the gradation pattern makes one turn. Then, the method for driving a liquid crystal display device is characterized in that the difference in the number of consecutive same states between the respective display elements in each of the gradation patterns is minimized. 3. The method for driving a liquid crystal display device according to claim 1, wherein the gradation pattern is such that the voltage level of a data signal is minimum. 4. The method for driving a liquid crystal display device according to claim 1, wherein when the selection pattern of the scanning signal is switched, the gradation pattern is switched according to the switching. Driving method for liquid crystal display device. 5. The method for driving a liquid crystal display device according to claim 1, wherein the gradation pattern is switched for each block on the display screen at which display data switching timing is different. And a method for driving a liquid crystal display device. 6. A liquid crystal display device using the method for driving a liquid crystal display device according to claim 1. 7. A plurality of scan electrodes to which a selection signal is applied in a selection period and a scanning signal to which a non-selection signal is applied in a non-selection period are applied, and a plurality of scanning electrodes to which a data signal based on display data is applied. Of the scan electrodes grouped into a plurality of groups, the scan electrodes having a signal electrode and a display element driven by the scan signal and the data signal are orthogonal to each other in a certain period. A liquid crystal display device that is selected by the selection signal at the same time, and the selection period is divided into p (p is an integer of 2 or more) sub-selection periods to perform gradation display by frame gradation. A selection pattern defining a pattern of the selection signal applied to the selected scan electrodes in one frame period, wherein the selection patterns are simultaneously selected in each sub-selection period. The frame gradation of each display element having a plurality of selection patterns in which the pattern of the selection signal applied to the inspection electrode is partially different, and which constitutes a basic unit for expressing gradation by the frame gradation. Is a gradation pattern that defines an on / off state in a plurality of frame periods that express gradation by means of an ON state in a frame period of each display element that constitutes the basic unit corresponding to each of the selection patterns. A selection pattern switching unit for switching the selection patterns, the gradation pattern corresponding to the selection patterns having a plurality of the gradation patterns in which the off state is partially different; A liquid crystal display device, comprising: 8. The liquid crystal display device according to claim 7,
A liquid crystal display device comprising: a gradation pattern switching unit for switching the gradation pattern and a gradation data conversion unit for each block of the display screen, which has a different switching timing of display data. 9. An electronic apparatus comprising the liquid crystal display device according to claim 6.