JPH10333645A - Driving method for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make uniformly correctable a cross talk caused by the position in the scanning line direction, by counting the number of on or off of the display data on one horizontal scanning line, and modulating the voltage effective value of the scanning voltage. SOLUTION: An off-number counting circuit 9 counts the number of display data turning off picture elements 6 during one scan within the display data fed from a control circuit 7. The off-number is weightedly counted as the function depending on the position of the scanning line direction. A PWM signal generating circuit 10 extracts the significant bits of the count value and generates a cross talk correcting signal. The cross talk is largely changed by the kind and display capacity of a liquid crystal panel used, and the number of bits extracted from the count value is changed for the correction quantity. The correction signal is directly inputted to a scanning line driving circuit 4, the applying period of the scanning voltage during one scanning period is changed, and the width of the scanning voltage is changed in response to the count value of the off-number of the display data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal display device, particularly a simple matrix type liquid crystal display device having a matrix pixel structure.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used as display displays such as personal computers and monitors because of their dramatic increase in display capacity and thin and lightweight characteristics. Among them, a super twisted nematic (hereinafter abbreviated as STN) type liquid crystal display device is characterized in that it is relatively inexpensive and good display characteristics can be obtained.

As a conventional driving method of an STN type liquid crystal display device, a voltage average addition method for making an effective voltage applied during a non-selection period constant is generally used (for example, Japanese Patent Application Laid-Open No. 50-68419). However, in an actual liquid crystal panel, there are an electrode resistance of a matrix electrode to be used, an output resistance of a driving IC, and a capacitance of a liquid crystal. The voltage waveform applied to the liquid crystal becomes rounded or distorted. For this reason, the effective voltage value applied to each pixel deviates from the ideal value, and uneven display called crosstalk occurs depending on the display pattern and the like. Crosstalk tends to increase with an increase in the number of pixels and the panel size. In order to ensure higher display quality, crosstalk measures will be more important in the future.

Hereinafter, a conventional liquid crystal display device and a driving method will be described with reference to FIGS. FIG. 11 shows a configuration of a conventional liquid crystal display device. In FIG. 11, 1 is a liquid crystal panel, 2 is a scanning line, 3 is a signal line, and the scanning line 2 and the signal line 3 are arranged in a matrix. The pixel 6 becomes a capacitive load. A scanning line driving circuit 4 is connected to the scanning line 2 and a signal line 3 is connected.
Is connected to the signal line drive circuit 5. The scanning line driving circuit 4 sequentially scans the scanning lines every scanning period.

Further, the signal line driving circuit 5
The display data for the scanning period is held, and a desired voltage is applied to the liquid crystal panel 1 in synchronization with the scanning line driving circuit 4. Further, the control circuit 7 displays the display data and
A control signal such as a synchronization signal necessary for driving the liquid crystal panel 1 is supplied to the scanning line driving circuit 4 and the signal line driving circuit 5, and a power supply circuit 8
Supplies a predetermined liquid crystal driving voltage to the scanning line driving circuit 4 and the signal line driving circuit 5.

FIG. 12 shows an example of an actual driving waveform. Here, reference numeral 121 denotes a frame signal FRM, which indicates a frame start position. A period between the frame signal 121 and the next frame signal is referred to as a frame period 128, and drawing of one screen is completed in the frame period 128. Reference numeral 122 denotes a latch signal LP, which is a control signal obtained by dividing the frame period 128 by the number of scanning lines or more, and the period up to the next pulse indicates a scanning period 129 per scanning line. 123
Is an alternating signal M, which is used to prevent the liquid crystal from being deteriorated by DC application. FIG. 12 shows a case in which the polarity is changed for each frame to perform the AC conversion. However, a method of performing the AC conversion inversion every several scanning lines is widely known.

The liquid crystal drive voltage supplied in the power supply circuit 8 includes a positive scanning line selection voltage V0 and a negative scanning line selection voltage V0.
4. With a scanning line non-selection voltage V2, a positive signal line selection voltage, and a negative signal line non-selection voltage V1, a negative signal line selection voltage,
In addition, a positive signal line non-selection voltage V3 is used.

Specifically, when the polarity of the alternating signal M of the liquid crystal is positive, the scanning line driving circuit 4 applies V0 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. Apply. The signal line driving circuit 5 applies V3 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V1 to the signal line 3 where the OFF pixel exists.

On the other hand, when the polarity of the alternating signal M of the liquid crystal is negative, the scanning line drive circuit 4 applies V4 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. The signal line driving circuit 5 applies V1 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V3 to the signal line 3 where the OFF pixel exists.

Reference numeral 124 denotes a scanning waveform applied to the scanning electrode;
Reference numeral 125 denotes a signal waveform applied to the signal electrode. As described above, each voltage is selected by the AC signal M of 123. Therefore, a difference voltage between the signal line driving waveform and the scanning signal waveform is applied to each display pixel.

Next, a description will be given of crosstalk generated when the above-described driving method is used. FIG. 13 shows a display pattern, and 132 and 133 are, for example, white background 1
31 shows a black horizontal bar. At this time, white is turned on and black is turned off.

The liquid crystal panel has a different pixel capacitance depending on whether the pixel is turned on or off. For this reason, the display pattern off region 13
2 and 133 on regions 134, 135, 13 on both sides
In 6,137, since the number of off pixels having a smaller capacity is larger than that of 131, which is all on, the manner in which the scan waveform is rounded by the CR circuit is different, and the effective value of the scan waveform is higher than in other on regions. For this reason, the brightness at both ends of the horizontal bar is higher than the other background portions (hereinafter, this is referred to as horizontal crosstalk).

Among the above-mentioned horizontal crosstalks, there are also horizontal crosstalks (hereinafter referred to as boundary horizontal crosstalks) generated by superimposing a differential waveform distortion generated by switching of a signal waveform on a scanning waveform. Exists. For example, as shown at 138, 139, 140, 141 in FIG.
In 138 and 140, the luminance is higher than that in the 131 area, and in 139 and 141, the luminance is conversely reduced. This phenomenon occurs at the boundary of the display pattern as shown in FIG.

The driving method has been improved to eliminate the horizontal crosstalk. For example, Japanese Patent Application No. 7-34
In No. 2836, the number of ON / OFF pixels on each scanning line is counted in advance, and the selection pulse width is controlled in accordance with the number to correct the effective value.
In Japanese Patent Application No. Hei 8-286591, the selection pulse width is controlled based on the calculation result of the difference between the number of ON / OFF pixels on two consecutive scanning lines, and the effective value is corrected.
The above-described boundary horizontal crosstalk is reduced.

There are crosstalks other than the horizontal crosstalk described above. FIG. 14 shows a display pattern at that time, and 143 and 144 show, for example, black vertical bars on a white background. When white is turned on and black is turned off, differential distortions 147 and 148 are superimposed on the scanning lines according to the switching of the signal waveform and the AC signal. Since the difference between the signal voltage and the scanning voltage is applied to the liquid crystal, the effective voltage of the vertical bar upper and lower portions 145 and 146 becomes higher than the effective voltage of the white background portion of 142 due to the influence of the differential distortion. The brightness of the upper and lower portions of the vertical bar is higher than the brightness of the white background portion (this is hereinafter referred to as vertical crosstalk). Driving methods have been improved to eliminate the above vertical crosstalk. For example, in Japanese Patent Application Laid-Open No. 1-29899, the effective value is corrected by calculating the difference between the number of ON / OFF pixels between two consecutive scanning lines.

[0016]

However, even if the conventional crosstalk correction method is performed, crosstalk cannot be reduced over the entire surface of the liquid crystal panel 1.
For example, as shown in FIG.
The appearance of the horizontal crosstalk differs between when displayed on the power supply side of the scanning line as shown in FIG. 2 and when displayed on the last train side as shown in 133. As described above, since the liquid crystal panel can be represented as a CR distributed constant circuit, the load on the power supply side and the load on the final power side are different even if similar display is performed. In the case of the example in FIG. 13, the luminance at both ends of the black horizontal bar 132 on the power supply side is higher than the luminance at both ends of the black horizontal bar 133 on the last train side. FIG. 15 shows a comparison of the scanning voltage waveforms at this time.

From FIG. 15, the scanning voltage waveform is the most distorted in the white background portion 152 because all pixels are ON pixels. If a black horizontal bar is displayed on the power supply side,
The number of ON pixels in the last train side portion with a heavy load increases. On the other hand, when the black horizontal bar is displayed on the last train side, there are many ON pixels in the power supply side with a relatively light load, and both ends of the black horizontal bar are compared with when the black horizontal bar is displayed on the power supply side. Has the highest voltage effective value. For this reason, the conventional correction method that corrects from the number of ON / OFF pixels cannot perform a uniform correction over the entire surface of power supply and final power.

Also, as in the example shown in FIG. 14, even when black vertical bars are displayed on the power supply side and the last terminal side on a white background, the magnitude of distortion generated in the scanning line is heavier than that of the power supply side. Since the last train is larger, the conventional correction method only corrects a certain point in the scanning line direction, and cannot perform uniform correction over power supply and the last train.

In the examples of FIGS. 13 and 14, black bars are displayed on a white background. On the other hand, white bars are displayed on a black background and halftone displays are also dependent on positions on the liquid crystal panel. Crosstalk occurs.

[0020]

According to the driving method of the liquid crystal display device of the present invention, the number of pixels of display data on or off in one horizontal scanning line is weighted as a function depending on the position in the horizontal scanning direction and the scanning voltage is reduced. This modulates the effective voltage value, and thereby uniformly corrects garbage crosstalk depending on the position in the scanning line direction such as the power supply side or the last power side of the liquid crystal panel, which cannot be dealt with by the conventional crosstalk correction method. It becomes possible.

[0021]

According to the first aspect of the present invention, a liquid crystal is provided between a first substrate provided with a signal electrode group and a second substrate provided with a scanning electrode group intersecting with the signal electrode group. In a matrix type liquid crystal display device, a scanning voltage is applied to the scanning electrode group, a signal voltage is applied to the signal electrode group, and the number of ON or OFF of display data in one horizontal scanning line is applied. Are weighted as a function depending on the position in the horizontal scanning direction and counted, and the voltage effective value of the scanning voltage is modulated according to the obtained count value.

According to a second aspect of the present invention, a liquid crystal is sandwiched between a first substrate provided with a signal electrode group and a second substrate provided with a scanning electrode group intersecting with the signal electrode group. In a matrix type liquid crystal display device, a scanning voltage is applied to the scanning electrode group, a signal voltage is applied to the signal electrode group, and the number of ON or OFF of display data in one horizontal scanning line is determined in a horizontal scanning direction. The weighting and counting are performed as a function depending on the position, and the direction and the magnitude of the voltage distortion caused by the switching of each signal electrode are determined by the difference between the number of on or off of the display data for each one line in two consecutive scanning lines. And modulating the effective voltage value of the scanning voltage based on the calculation result.

According to a third aspect of the present invention, a liquid crystal is sandwiched between a first substrate provided with a signal electrode group and a second substrate provided with a scanning electrode group intersecting with the signal electrode group. In a matrix type liquid crystal display device, a scanning voltage is applied to the scanning electrode group, a signal voltage is applied to the signal electrode group, and the number of ON or OFF of display data in one horizontal scanning line is determined in a horizontal scanning direction. The weighting and counting are performed as a function depending on the position, and the direction and the magnitude of the voltage distortion caused by the switching of each signal electrode are determined by the difference between the number of ON or OFF of the display data of each one line in two consecutive scanning lines. The correction voltage is obtained by calculation and superimposed on the non-selection voltage of the scanning voltage based on the calculation result.

According to a fourth aspect of the present invention, in the first or second aspect, the effective value voltage modulation is performed according to the width of the scanning voltage. The invention according to claim 5 is characterized in that, in claim 1 or 2, the effective value voltage modulation is performed by changing the potential of the scanning voltage at each switching.

According to a sixth aspect of the present invention, in the third aspect, the direction of the correction voltage superimposed on the non-selection voltage of the scanning voltage is obtained by an exclusive OR of the display data and the liquid crystal alternating signal. It is characterized by being calculated from data.

According to a seventh aspect of the present invention, in the first or second or third aspect, the horizontal scanning line direction is divided into at least two or more regions, and display data is turned on or off for each of the divided regions. It is characterized by having a table for weighting numbers.

According to the driving method of the present invention, the number of ON or OFF of the display data in one horizontal scanning line is weighted and counted as a function depending on the position in the horizontal scanning direction, and according to the obtained count value, By modulating the effective value of the scanning voltage, it is possible to digitally obtain the difference between the power supply side area and the load side area in the scanning line direction in advance from the count value of the display data, and to perform correction according to the load difference. Since the value can be obtained, crosstalk depending on the position in the scanning direction that occurs when a horizontal bar or the like is displayed can be effectively corrected.

The direction and the magnitude of the voltage distortion caused by the switching of each signal electrode are determined by the above-mentioned weighting of the number of ON or OFF of the display data for each one line in two consecutive scanning lines. By calculating the difference and modulating the effective voltage value of the scanning voltage, the difference between the load in the power supply side region and the load in the last line side region in the scanning line direction and the direction of the distortion can be digitally determined in advance from the count value of the display data. Therefore, it is possible to effectively correct the boundary horizontal crosstalk depending on the position in the scanning direction that occurs when the signal waveform is switched when a horizontal bar or the like is displayed.

Further, the difference between the number of ON or OFF of the display data of each one line in two consecutive scanning lines obtained by weighting is calculated, and from the calculation result,
By superimposing the correction voltage on the scanning voltage, the direction of the distortion generated in the scanning voltage when the signal waveform is switched and the magnitude of each distortion generated in the power supply side area and the last power side area can be digitally determined from the display data count value. It is possible to effectively correct vertical crosstalk depending on the position in the scanning direction that occurs when a vertical bar or the like is displayed.

Hereinafter, the present invention will be described based on embodiments. (Embodiment 1) A liquid crystal display device that implements a driving method according to Embodiment 1 of the present invention is configured as shown in FIG.

In this liquid crystal display device, the liquid crystal panel 1 has scanning lines 2 and signal lines 3 arranged in a matrix, and the intersection of the scanning lines 2 and the signal lines 3 is a pixel 6. Note that the display pixel becomes a capacitive load. A scanning line driving circuit 4 is connected to the scanning lines 2 of the liquid crystal panel 1, and a signal line driving circuit 5 is connected to the signal lines 2.
Connect. The scanning line driving circuit 4 sequentially scans the scanning lines every scanning period. The signal line drive circuit 5 holds the display data for one scanning period and drives the load in synchronization with the scan line drive circuit 4 according to the display data. The power supply circuit 8 supplies a predetermined liquid crystal driving voltage to the scanning line driving circuit 4 and the signal line driving circuit 5. The control circuit 7 supplies display data to be displayed and necessary control signals such as a synchronization signal to the scanning line driving circuit 4 and the signal line driving circuit 5.

Reference numeral 9 denotes an off-number counting circuit for counting the number of display data for turning off the pixel 6 in one scanning period among the display data sent from the control circuit 7. The number of offs is weighted and counted as a function that depends on the position in the scan line direction. Since the weighting value changes depending on the display capacity and size of the liquid crystal panel to be used, it is necessary to determine an optimum value by a simple matrix panel to be displayed.

FIGS. 2A and 2B show a 17-type SXGA.
A simulation result of the position dependency of the scanning voltage waveform when a horizontal (1024 × 1280 RGB) color STN panel is displayed on each of the power supply side and the terminal end side is shown. Here, FIG. 2A shows the rounding of the scanning voltage waveform on the power supply side. Reference numeral 21 denotes a black display on the power supply side half surface and white display on the final power supply side half. Reference numeral 23 denotes a scanning voltage waveform when the display and the last half side are black display, and when the whole surface is white display. The horizontal axis indicates the normalized time and the vertical axis indicates the voltage. It is assumed here that white display is on (high load) and black display is off (low load). From the above simulation results, it can be seen that the rounding of the scanning voltage waveform is smaller when black is displayed on the last train side than when black is displayed on the power feeding side. FIG. 2 (b)
Shows the rounding of the scanning voltage waveform on the last train side, and the all white display of 26 has the largest rounding of the waveform similarly to the rounding result of the scanning voltage waveform on the power feeding side, and black is displayed on the last train side of 25. The waveform has the least rounding.

FIG. 3 shows a simulation result in which these results are shown by the effective value of the scanning voltage. FIG. 3 shows the effective value of the scanning voltage with respect to the position of the horizontal crosstalk pattern in the scanning line direction. From this, it can be seen that the effective value of the scanning voltage becomes higher on the last train side.

That is, for example, when a black horizontal bar pattern is displayed on the power supply side and the last train side on a white background, crosstalk appears more remarkably when displayed on the last train side. Using the above result, crosstalk correction depending on the position in the scanning line direction is performed. Hereinafter, an example of actual weighting will be described.

FIG. 4 shows a method of dividing the scanning line direction of the liquid crystal panel 1 into four regions in the off-number counting circuit 9 and weighting the number of offs in each region. Here, each of the areas 1 to 4 is divided by the number of data shift clocks. In the normal STN, 8-bit or 12-bit parallel data is input as display data, and is transferred to the signal line driving circuit 5 every 8 or 12 bits by a data shift clock. Thus, for example, SXG
In the case of A (1024 × 1280 RGB) and the transfer of the display data is 12 bits, the required number of data shift clocks is 32
It becomes 0 clock. Thus, the regions 1 to 4 can be divided by the number of data shift clocks. The coefficient in FIG. 4 is for a case where 4 is 100%, and at this time, the maximum number of off-numbers is counted. Here, weight 3 is 7
5%, 2 is 50%, and 1 is 25%. Therefore, when a table without weighting such as 41 is used, the maximum value of the number of off-states is 3840. Also,
In the case of 42, the weight is counted and the value is reduced to 2400.

Reference numeral 10 in FIG. 1 is a PWM signal generation circuit.
The higher-order bits of the weighted count value are extracted from the off-number counting circuit 9 to generate a signal for crosstalk correction. As mentioned above, crosstalk varies greatly depending on the type of liquid crystal panel used and the display capacity.
The correction amount is also dealt with by changing the number of bits extracted from the above count value. The correction signal is directly input to the scanning line driving circuit 4, where the scanning voltage application period in one scanning period is varied. By varying the width of the scanning voltage in accordance with the count value of the number of OFF display data, horizontal crosstalk can be corrected.

Further, by using the above-mentioned weighting table, when the horizontal bar display as shown in FIG. 13 is performed, the count value obtained by the weighting table in the horizontal bar displayed on the power supply side is larger than that displayed on the last train side. As a result, the correction amount decreases accordingly. For this reason, it is possible to absorb the difference between the rounding on the power supply side and the rounding on the terminal side, and it is possible to uniformly correct crosstalk depending on the position.

FIG. 5 shows an example of a driving waveform actually applied to the liquid crystal. Here, 50 is a frame signal FRM, which indicates the start position of the frame. A period between the frame signal and the next frame signal is referred to as a frame period 56, and drawing of one screen is completed in the frame period 56. 51 is a latch signal LP
The control signal is obtained by dividing the frame period 56 by the number of scanning lines or more, and the period up to the next pulse indicates a scanning period 57 per scanning line. Reference numeral 52 denotes an alternating signal M, which is used to prevent the liquid crystal from being degraded by DC application.

In FIG. 5, the polarity is changed for each frame.
Although the case of performing AC conversion is shown, a method of performing AC conversion inversion over several scanning lines is also widely known. The liquid crystal driving voltage supplied in the power supply circuit 8 of FIG. 1 includes a positive scanning line selection voltage V0, a negative scanning line selection voltage V4, a scanning line non-selection voltage V2, a positive signal line selection voltage, and a negative signal. The line non-selection voltage V1, the negative signal line selection voltage, and the positive signal line non-selection voltage V3.

More specifically, when the polarity of the alternating signal M of the liquid crystal is positive, the scanning line drive circuit 4 applies V0 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. Apply. The signal line driving circuit 5 applies V3 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V1 to the signal line 3 where the OFF pixel exists.

On the other hand, when the polarity of the liquid crystal alternating signal M is negative, the scanning line drive circuit 4 applies V4 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. The signal line driving circuit 5 applies V1 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V3 to the signal line 3 where the OFF pixel exists.

Reference numeral 59 denotes a scanning waveform applied to the scanning electrode,
Reference numeral 91 denotes a signal waveform applied to the signal electrode, and each voltage is selected by the AC signal M of 52 as described above. Therefore, a difference voltage between the signal waveform 591 and the scanning waveform 59 is applied to each display pixel. 53 is M
With the ASK signal, the signal goes to the L level only during a period based on the count value of the display data obtained by the off-number counting circuit 9 and the PWM signal generating circuit 10. This data changes the width of the scanning voltage via the scanning line driving circuit 4.

In FIG. 5, a first period 56 shows a waveform when a black horizontal bar 132 is displayed on the power supply side in FIG. 13, and a second period 58 shows a black horizontal bar 13 on the last power side in FIG.
3 shows a waveform when 3 is displayed. The width of the scanning voltage and the width of the MASK signal are output in accordance with the weighted count value.
The MASK signal width 55 in the second period 58 is larger than the K signal width 54. Since the width of the MASK signal is directly equal to the width of the scanning voltage, the effective value of the scanning voltage in the second period 58 is smaller than the effective value in the first period 56, and as a result, the effective value occurs depending on the position in the scanning line direction. Lateral crosstalk can be uniformly corrected.

In this embodiment, an example has been shown in which the weighting method is divided into four areas and the respective areas are provided with a weighting table to perform counting. Is not limited to this example. For example, it is possible to divide into two or more arbitrary areas and have a table for each area.
By having a table using the above function for each dot, all methods can be applied, such as using one or more linear approximation formulas to find the effective value by referring to the above table from the coordinates in a certain scanning line direction It goes without saying that the effect of the crosstalk correction can be expected even if it is performed.

Further, in this embodiment, an example has been shown in which the number of OFF data is counted as a method of counting display data. However, even if the number of ON data is counted instead, only the sign is inverted. Similar results can be obtained.

Similar counting can be performed not only on a black horizontal bar on a white background but also on a black background display and a gradation display. By using the above method, it is possible to correct horizontal crosstalk depending on the position. Needless to say,

(Embodiment 2) Next, a method of driving a liquid crystal display device according to Embodiment 2 of the present invention will be described.

In this embodiment, the differential voltage distortion generated on the scanning side at the time of switching of the signal waveform is calculated using weighting, the scanning pulse width is modulated according to this, the effective value is corrected, and the boundary horizontal crosstalk is calculated. Is to be reduced.

A liquid crystal display device that performs the driving method according to the second embodiment is configured as shown in FIG. Where 1
Denotes a liquid crystal panel, in which scanning lines 2 and signal lines 3 are arranged in a matrix, and an intersection of the scanning lines 2 and the signal lines 3 is defined as a pixel 6. Note that the display pixel becomes a capacitive load. A scanning line driving circuit 4 is connected to the scanning lines 2 of the liquid crystal panel 1, and a signal line driving circuit 5 is connected to the signal lines 3. The scanning line driving circuit 4 sequentially scans the scanning lines every scanning period.

The signal line driving circuit 5 holds the display data for one scanning period and drives the liquid crystal panel 1 in synchronization with the scanning line driving circuit 4. The power supply circuit 8 supplies a predetermined liquid crystal driving voltage to the scanning line driving circuit 4 and the signal line driving circuit 5.

The control circuit 7 supplies display data to be displayed and necessary control signals such as a synchronization signal to the scanning line driving circuit 4 and the signal line driving circuit 5. OFF number counting circuit 61
Is the scanning line 2 when the signal waveform from the signal line 3 is switched.
Is provided as means for correcting the effective value of the scanning voltage when the distortion waveform generated in the scanning voltage is superimposed on the scanning voltage. Here, the off-number counting circuit 61 counts the number of offs in one scanning period of the data for turning off the pixels 6 among the display data sent from the control circuit 7.

The off-number counting circuit 61 counts the display data using the weighting described in the first embodiment. FIG. 4 illustrates the off-number counting circuit 61.
The scanning line direction of the liquid crystal panel 1 is divided into four regions, and weighting of the number of OFFs in each region is shown. Here, each of the areas 1 to 4 is divided by the number of data shift clocks. In the normal STN, 8-bit or 12-bit parallel data is input as display data, and is transferred to the signal line driving circuit 5 every 8 or 12 bits by a data shift clock.

For example, SXGA (1024 × 1280RG)
When the display data is 12-bit transfer in B), the required number of data shift clocks is 320 clocks. Thus, the regions 1 to 4 can be divided by the number of data shift clocks. The coefficient in FIG. 4 is for a case where 4 is 100%, and at this time, the maximum number of off-numbers is counted.
Here, weight 3 is 75%, 2 is 50%, and 1 is 25
% Count shall be performed. Therefore, when a table without weighting such as 41 is used, the maximum value of the number of off-states is 3840. In addition, since the weight is counted at 42, the maximum value of the number of OFFs is as small as 2400.

The arithmetic circuit 62 has a means for storing the number of off-states in the scanning period one line before the current scanning period. By taking the difference between the number of off-states in the two scanning lines, it is possible to extract the number of switching between the signal waveform one scanning period ago and the signal waveform in the current scanning period.

Here, it should be noted that unlike the method of simply using the value obtained by counting the number of off or on data obtained from the display data as in the case of normal horizontal crosstalk correction, the waveform between two lines is different. That is, it is necessary to determine the magnitude and the direction of the distortion of the scanning voltage waveform caused by the switching.

As described above, since the driving of the liquid crystal is performed by the AC inversion driving, it is necessary to monitor the polarity of the AC signal M applied to the line. By monitoring the polarity of the AC signal, it is possible to know the polarity of the signal actually applied during a certain scanning period and the switching direction. To monitor the polarity of the AC signal, for example, as shown in FIG. 7, an EX-OR circuit 71 to which the display data 72 and the AC signal M of the 73 sent from the control signal are input.
Can be easily realized by counting the M display data 74 of the output.

Since the number of switching is counted, a similar result can be obtained by counting the number of ON data, only by inverting the sign. All that is required is to be able to calculate the number of switching signal waveforms. Similar counting can be performed for grayscale data.

The arithmetic circuit 62 first calculates the number of switching signal waveforms from the number of off pixels in one scanning period obtained by the off number counting circuit 61 and the number of off pixels in the preceding one scanning period. To perform a predetermined operation. For example, when the direction of the differential distortion waveform from the signal waveform has the same polarity as the scanning waveform, the width of the scanning waveform is calculated to be narrow in order to increase the effective voltage per scan. If the switching amount is large, the width of the scanning waveform is varied according to the amount. Conversely, if the direction of the differential distortion from the signal waveform is different from the scanning waveform, the reduced effective voltage is compensated by increasing the width of the scanning waveform.

Numeral 63 denotes a PWM signal generating circuit which extracts the upper bits of the count value calculated by weighting from the off-number counting circuit 61 and the arithmetic circuit 62, and generates a signal for crosstalk correction. As described above, since the crosstalk greatly changes depending on the type of liquid crystal panel used and the display capacity, the correction amount is also dealt with by changing the number of bits extracted from the above count value. The correction signal is directly input to the scanning line driving circuit 4, where the width of the scanning voltage is varied so as to correct the distortion generated in the scanning line 2.

FIG. 8 shows an example of a driving waveform actually applied to the liquid crystal. Here, reference numeral 80 denotes a frame signal FRM, which indicates a frame start position. A period between the frame signal and the next frame signal is referred to as a frame period 86, and drawing of one screen is completed in the frame period 86. 81 is a latch signal LP
A control signal obtained by dividing the frame period 86 by the number of scanning lines or more, and the period up to the next pulse indicates a scanning period 87 per scanning line. Reference numeral 82 denotes an alternating signal M, which is used to prevent the liquid crystal from being deteriorated by DC application.

Although FIG. 8 shows a case where the polarity is changed for each frame to perform the AC conversion, a method of performing the AC inversion for a few scanning lines is also widely known. The liquid crystal driving voltage supplied in the power supply circuit 8 is a positive scanning line selection voltage V0, a negative scanning line selection voltage V4, a scanning line non-selection voltage V2, a positive signal line selection voltage, and a negative signal line non-selection. The voltage V1 is a negative signal line selection voltage and a positive signal line non-selection voltage V3.

Specifically, when the polarity of the alternating signal M of the liquid crystal is positive, the scanning line driving circuit 4 applies V0 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. Apply. The signal line driving circuit 5 applies V3 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V1 to the signal line 3 where the OFF pixel exists.

On the other hand, when the polarity of the alternating signal M of the liquid crystal is negative, the scanning line drive circuit 4 applies V4 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. The signal line driving circuit 5 applies V1 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V3 to the signal line 3 where the OFF pixel exists.

Reference numeral 89 denotes a scanning waveform applied to the scanning electrode;
Reference numeral 91 denotes a signal waveform applied to the signal electrode, and each voltage is selected by the AC signal M of 82 as described above. Therefore, the scanning waveform 89 and the signal waveform 8 are applied to each display pixel.
A differential voltage of 91 will be applied. 83 is M
With the ASK signal, the OFF number counting circuit 61 and the arithmetic circuit 62
And L level only during a period based on the count value of the display data obtained by the PWM signal generation circuit 63.
The MASK waveform 83 varies the width of the scanning voltage via the scanning line driving circuit 4.

In FIG. 8, a first period 86 shows a waveform when a black horizontal bar 132 is displayed on the power supply side in FIG. 13, and a second period 88 shows a black horizontal bar 13 on the last train side in FIG.
3 shows a waveform when 3 is displayed. Further, reference numeral 84 denotes a MASK signal of a boundary horizontal crosstalk generation line corresponding to the portion 138 in FIG. 13, and reference numeral 85 denotes 140 in FIG.
MASK of the boundary horizontal crosstalk generation line corresponding to the section
Indicates a signal.

As described above, the MASK signal is 1
This is a value obtained as a result of calculating the number of switching of each of the 38 or 140 scan lines and the display data one scan line before and the direction of the distortion generated in the scan line 2. Further, since the width of the scanning voltage and the MASK signal width are output in accordance with the weighted count value, the MASK signal width 84 in the first period 86 is compared with the MASK signal width 84 in the second period 8.
8, the MASK signal width 85 increases. Since the width of the MASK signal is directly equal to the width of the scanning voltage, the effective value of the scanning voltage in the second period 88 is smaller than the effective value of the first period 86, and as a result, the effective value occurs depending on the position in the scanning line direction. Boundary horizontal crosstalk can be uniformly corrected.

In this embodiment, an example has been shown in which the weighting method is divided into four areas and the respective areas are provided with a weighting table to perform counting. Is not limited to this example. For example, it is possible to divide into two or more arbitrary areas and have a table for each area.
By having a table using the above function for each dot, all methods can be applied, such as using one or more linear approximation formulas to find the effective value by referring to the above table from the coordinates in a certain scanning line direction It goes without saying that the effect of the crosstalk correction can be expected even if it is performed.

By using the above-mentioned weighting table, even when the horizontal bar display as shown in FIG. 13 is performed, the count value obtained by the above-mentioned weighting table is displayed on the last train side in the horizontal bar displayed on the power supply side. The correction amount is smaller, and the correction amount is correspondingly smaller. For this reason, it is possible to absorb the difference between the rounding on the power supply side and the rounding on the final train side, and it is possible to uniformly correct the boundary lateral crosstalk depending on the position.

Further, in this embodiment, an example in which the number of off-states is counted as a method of counting display data has been described. However, it is better to count the number of switching of display data for correction of boundary horizontal crosstalk. Alternatively, even if the number of ON data is counted, a similar result can be obtained only by inverting the sign. That is, it is only necessary that the waveform switching amount can be calculated. Similar corrections can be made for black background and gradation data.

As described above, in this embodiment, the width of the scanning waveform applied to the scanning line is changed in accordance with the weighted and counted number of switchings of the signal waveform, thereby canceling the nonuniformity of the effective value. The voltage can be controlled at a high level, and can be greatly improved. Further, since the effective value voltage is controlled by modulating the width of the scanning line as a scanning voltage modulation means, the circuit configuration is simplified, and a large display power is not required.

Although the correction of the effective voltage value is performed by modulating the scanning waveform width, the same result can be obtained by using a method of modulating the potential of the scanning waveform. .

(Embodiment 3) Next, a method of driving the liquid crystal display device in Embodiment 3 will be described. In this embodiment, the differential voltage distortion that occurs on the scanning side when the signal voltage is switched is calculated using weighting, and the correction voltage is applied to the non-selection voltage of the scanning voltage in accordance with the weighting. This reduces vertical crosstalk.

A liquid crystal display device for implementing the driving method according to the third embodiment of the present invention is configured as shown in FIG. Here, reference numeral 1 denotes a liquid crystal panel. The scanning lines 2 and the signal lines 3 are arranged in a matrix, and the intersection of the scanning lines 2 and the signal lines 3 is a pixel 3. Note that the display pixel becomes a capacitive load. A scanning line driving circuit 4 is connected to the scanning lines 2 of the liquid crystal panel, and a signal line driving circuit 5 is connected to the signal lines 2. The scanning line driving circuit 4 sequentially scans the scanning lines every scanning period.

Further, the signal line driving circuit 5
The display data for the scanning period is held, and the load is driven in accordance with the display data in synchronization with the scanning line driving circuit 4. The power supply circuit 8 supplies a predetermined liquid crystal driving voltage to the scanning line driving circuit 4 and the signal line driving circuit 5. Control circuit 7
Supplies display data to be displayed and necessary control signals such as a synchronization signal to the scanning line driving circuit 4 and the signal line driving circuit 5.

Reference numeral 91 denotes an off-number counting circuit.
It is provided as a means for correcting an effective value when a distortion waveform generated in the scanning line 2 at the time of switching of the signal waveform from the signal line 3 is superimposed on the scanning waveform. Here, the number-of-offs counting circuit 91 counts the number of offs in one scanning period for the data for turning off the pixel 6 among the display data sent from the control circuit 7. Further, the above-described off-number counting circuit 91 performs counting using weighting as described in the first and second embodiments. FIG. 4 shows the weighting of the number of OFFs in each area when the scanning line direction of the liquid crystal panel 1 is divided into four areas in the OFF number counting circuit 91. Here, each of the areas 1 to 4 is divided by the number of data shift clocks. In the normal STN, the display data is 8 bits or 12 bits.
Bit parallel data is input, and is transferred to the signal electrode drive circuit every 8 bits or 12 bits by a data shift clock. Therefore, for example, SXGA (102
In the case of 4 × 1280 RGB) transfer of display data of 12 bits, the required number of data shift clocks is 320 clocks. Thus, the regions 1 to 4 can be divided by the number of data shift clocks. The coefficient in FIG. 4 is for a case where 4 is 100%, and at this time, the maximum number of off-numbers is counted. Here, it is assumed that the weighting 3 counts 75%, 2 counts 50%, and 1 counts 25%. Therefore, when using an unweighted table as in 41,
The maximum value of the off-number is 3840. In the case of 42, the weight is counted and the value is reduced to 2400.

The arithmetic circuit 92 has means for storing the number of off-states in the scanning period one line before the currently scanning period. By taking the difference between the number of off-states in the two scanning lines, it is possible to count the number of switching between the signal waveform one scanning period before and the signal waveform in the current scanning period.

Here, attention should be paid to the first embodiment.
Unlike the method of simply using the value obtained by counting the number of off or on data obtained from the display data, such as the correction of the horizontal crosstalk shown in the above, the magnitude of the distortion of the scanning voltage waveform caused by the switching of the waveform between two lines That is, it is necessary to determine the direction of the distortion.

As described above, since the driving of the liquid crystal is performed by the AC inversion drive, it is necessary to monitor the polarity of the AC signal M applied to the line. By monitoring the polarity of the AC signal, it is possible to know the polarity of the signal actually applied during a certain scanning period and the switching direction. To monitor the polarity of the AC signal, for example, as shown in FIG.
It can be easily realized by counting the M display data 74 of the output of the EX-OR circuit 71 to which the data and the AC signal 73 are input.

Incidentally, since the number of switching is counted, the same result can be obtained only by inverting the sign even if the number of ON data is reversed. What is needed is that it is only necessary to calculate the number of switching of the signal waveform. Similar counting can be performed for grayscale data.

The above is the same as the structure shown in the first and second embodiments. Correction voltage generation circuit 9
3 calculates the number of switching signal waveforms based on the number of off-states in one scanning period obtained by the off-number counting circuit 91 and the preceding one scanning period, and performs a predetermined operation on the result. By comparing the number of off-states in the current scanning period with the number of off-states one scanning period ago, the direction and magnitude of the differential distortion actually generated in the scanning voltage are calculated, and the correction voltage is corrected in the direction for correcting the differential distortion. Occurs. The correction voltage is superimposed on the non-selection potential of the scanning voltage, and corrects vertical crosstalk caused by differential distortion.

FIG. 10 shows an example of the driving waveform actually applied to the liquid crystal. Here, 100 is a frame signal FRM, which indicates the start position of the frame. A period between the frame signal and the next frame signal is referred to as a frame period 106, and drawing of one screen is completed in the frame period 106. Reference numeral 101 denotes a latch signal LP, which is a control signal obtained by dividing the frame period 106 by the number of scanning lines or more, and the period up to the next pulse indicates a scanning period 107 per scanning line.
An AC signal M is used to prevent the liquid crystal from being deteriorated by DC application. In FIG. 10, alternating inversion is performed every three scanning periods.

The liquid crystal driving voltage supplied in the power supply circuit 8 includes a positive scanning line selection voltage V0 and a negative scanning line selection voltage V
4. With a scanning line non-selection voltage V2, a positive signal line selection voltage, and a negative signal line non-selection voltage V1, a negative signal line selection voltage,
In addition, it is provided with a positive signal line non-selection voltage V3.

Specifically, when the polarity of the liquid crystal alternating signal M is positive, the scanning line drive circuit 4 applies V0 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. Apply. The signal line driving circuit 5 applies V3 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V1 to the signal line 3 where the OFF pixel exists.

On the other hand, when the polarity of the liquid crystal alternating signal M is negative, the scanning line drive circuit 4 applies V4 to the scanning line 2 to be scanned, and applies V2 to the remaining scanning lines 2. The signal line driving circuit 5 applies V1 to the signal line 3 of the ON pixel among the display pixels on the scanning line 2 to be scanned, and applies V3 to the signal line 3 where the OFF pixel exists.

Reference numeral 109 denotes a voltage waveform applied to the scanning electrode;
Reference numeral 110 denotes a signal waveform applied to the signal electrode;
Each voltage is selected by the AC conversion signal M. Therefore,
A difference voltage between the scanning waveform and the signal waveform is applied to each display pixel.

In FIG. 10, the first period 106 corresponds to FIG.
14 shows a waveform when a vertical bar 143 is displayed on the middle power supply side. In the second period 108, the vertical bar 143 is displayed on the last train side in FIG.
4 shows a waveform when 4 is displayed. Also, 103
Is a correction voltage to be superimposed on the scanning voltage, which is obtained by calculating the direction and magnitude of the voltage to be corrected from the number of switching of the display data in the current scanning period and the number of offs of the display data one scanning period ago. It is. In addition, for example, a weighting table indicated by reference numeral 42 in FIG. By performing the above counting, when a vertical bar is displayed on the power supply side as in 143, the correction voltage 103
Is smaller than when a vertical bar is displayed on the last train side as in 144. The correction voltage acts in a direction to compensate for the differential distortion generated in the scanning line 2, and its magnitude is determined depending on the position in the scanning line direction, so that the vertical crosstalk generated depending on the position is uniformly corrected. can do.

In this embodiment, an example has been shown in which the weighting method is divided into four areas and the respective areas are provided with a weighting table to perform counting, but the weighting method according to the present invention is used. Is not limited to this example. For example, it is possible to divide into two or more arbitrary areas and have a table for each area.
By having a table using the above function for each dot, all methods such as using one or more linear approximation formulas for obtaining an effective value by referring to the above table from coordinates in a certain scanning line direction can be used. It goes without saying that the effect of crosstalk correction can be expected even if applied.

Further, in this embodiment, an example has been shown in which the number of off-states is counted as a method of counting display data. Counting is good, and even if the number of ON data is counted instead, the same result can be obtained only by inverting the sign. That is, it is only necessary that the waveform switching amount can be calculated. Similar calculations can be performed on the gradation data. Further, in this embodiment, the change in the correction amount is dealt with by changing the width of the correction voltage. However, if the change in the effective value due to the differential distortion can be compensated, the above-described example is used. However, it is needless to say that the correction can be made by, for example, the magnitude of the voltage.

[0090]

As described above, according to the present invention, the position in the scanning line direction such as the power supply side or the last power side of the liquid crystal panel cannot be dealt with by the conventional horizontal crosstalk, boundary horizontal crosstalk and vertical crosstalk correction method. Dependent crosstalk can be uniformly corrected, and higher quality display can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a liquid crystal display device according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating the principle of occurrence of position-dependent horizontal crosstalk.

FIG. 3 is a diagram showing a scanning voltage effective value due to a position-dependent horizontal crosstalk.

FIG. 4 is a diagram showing a weighting method according to the first embodiment of the present invention.

FIG. 5 is a timing chart showing driving waveforms according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram of a liquid crystal display device according to Embodiment 2 of the present invention.

FIG. 7 is an explanatory diagram of a counting method according to the second embodiment of the present invention.

FIG. 8 is a timing chart showing driving waveforms according to the second embodiment of the present invention.

FIG. 9 is a configuration diagram of a liquid crystal display device according to Embodiment 3 of the present invention.

FIG. 10 is a timing chart showing driving waveforms according to the third embodiment of the present invention.

FIG. 11 is a configuration diagram of a conventional liquid crystal display device.

FIG. 12 is a timing chart showing a conventional drive waveform.

FIG. 13 is a diagram showing a display pattern of occurrence of horizontal crosstalk and boundary horizontal crosstalk.

FIG. 14 shows a display pattern of occurrence of vertical crosstalk.

FIG. 15 is a diagram of a scanning waveform illustrating a principle of occurrence of horizontal crosstalk depending on a position.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Scanning line 3 Signal line 4 Scanning line drive circuit 5 Signal line drive circuit 6 Display pixel 7 Control circuit 8 Power supply circuit 9, 61, 91 Off-count circuit 10, 63 PWM signal generation circuit 21, 24 Power supply black Scan voltage waveform 22, 25 scan voltage waveform at the time of final black 23, 26 scan voltage waveform at all white 41 value of weighting factor without weight 42 value of weighting factor with weighting 50, 80, 100, 121 Frame signal 51, 81, 101, 122 Latch pulse 52, 73, 82, 102, 123 Alternating signal 53, 83 MASK signal 54, 55, 84, 85 Scan voltage waveform correction width 56, 58, 86, 88, 106 , 108,128
Frame period 57, 87, 107, 129 1 scanning period 59, 89, 109, 124 scanning waveform 591, 891, 110, 125, 126 signal waveform 62, 92 arithmetic circuit 72 display data 74 M display data 93 correction voltage generation circuit 103 Correction voltage 104 Power supply side display correction voltage 105 Final power side display correction voltage 131, 142 White background area 132 Power supply side black horizontal bar 133 Final power side black horizontal bar 134, 135, 136, 137 Horizontal crosstalk generation area 135, 139 , 140, 141 Boundary horizontal crosstalk generation area 143 Black vertical bar on power supply side 144 Black vertical bar on final side 145, 146 Vertical crosstalk generation area 147, 148 Differential distortion 150, 151, 152 Scanning waveform

Claims (7)

[Claims] 1. A matrix type liquid crystal display in which liquid crystal is sandwiched between a first substrate provided with a signal electrode group and a second substrate provided with a scanning electrode group arranged in an intersecting manner with the signal electrode group. In the apparatus, a scan voltage is applied to the scan electrode group, a signal voltage is applied to the signal electrode group, and the number of ON or OFF of display data in one horizontal scan line is weighted as a function depending on a horizontal scan direction position. And count,
A method for driving a liquid crystal display device that modulates a voltage effective value of a scanning voltage according to an obtained count value. 2. A matrix type liquid crystal display in which a liquid crystal is sandwiched between a first substrate provided with a signal electrode group and a second substrate provided with a scanning electrode group crossed with the signal electrode group. In the apparatus, a scan voltage is applied to the scan electrode group, a signal voltage is applied to the signal electrode group, and the number of ON or OFF of display data in one horizontal scan line is weighted as a function depending on a horizontal scan direction position. And count,
The direction and the magnitude of the voltage distortion caused by the switching of each signal electrode are obtained by calculating the difference between the number of ON or OFF of the display data for each one of two consecutive scanning lines, and from the calculation result, A method for driving a liquid crystal display device that modulates a voltage effective value of a scanning voltage. 3. A matrix type liquid crystal display in which a liquid crystal is sandwiched between a first substrate provided with a signal electrode group and a second substrate provided with a scanning electrode group intersecting with the signal electrode group. In the apparatus, a scan voltage is applied to the scan electrode group, a signal voltage is applied to the signal electrode group, and the number of ON or OFF of display data in one horizontal scan line is weighted as a function depending on a horizontal scan direction position. And count,
The direction and the magnitude of the voltage distortion caused by the switching of each signal electrode are obtained by calculating the difference between the number of ON or OFF of the display data of each one line in two consecutive scanning lines, and from the above calculation result, A method for driving a liquid crystal display device in which a correction voltage is superimposed on a non-selection voltage of a scanning voltage. 4. The method of driving a liquid crystal display device according to claim 1, wherein the effective value voltage modulation is performed according to the width of the scanning voltage. 5. The driving method for a liquid crystal display device according to claim 1, wherein the effective value voltage modulation is performed by changing the potential of the scanning voltage at each switching. 6. The method according to claim 1, wherein a direction of the correction voltage superimposed on the non-selection voltage of the scanning voltage is calculated from data obtained by an exclusive OR of the display data and the liquid crystal alternating signal. 4. The method for driving a liquid crystal display device according to item 3. 7. A horizontal scanning line direction is divided into at least two or more regions, and weighting of the number of display data on or off is performed for each of the divided regions using a table having a weight. 4. The driving method for a liquid crystal display device according to claim 1, wherein