JPH09330062A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve display quality by setting the count values of a clock in an AC-converted signal generating means so that a specified relational expression is satisfied between the count value and the number of clocks in one frame. SOLUTION: It is desirable that the following equation is satisfied D/N=no+2 or D/N=ne+(N-2), where D is the number of clocks in one frame, N is the count value of the clock in an AC-converted signal generating means, n0 is a positive odd number, and ne is a positive even number. Flickering is made unrecognized by human eyes since the number of the clocks CLI which reverse the voltage level of the AC-converted signal M is set so as to satisfy a specified relational expression for the duty number (number of clocks CLI in one frame) of the display control device. By this, no flickering is generated on the display surface of the liquid crystal display panel and the display quality of the displayed pictures is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a technique effective when applied to an alternating signal generating circuit in a simple matrix type liquid crystal display device.

[0002]

2. Description of the Related Art STN (Super Twisted)
Nematic) simple matrix type liquid crystal display devices are widely used as display devices such as notebook personal computers.

FIG. 11 is a block diagram showing a schematic structure of a conventional STN type simple matrix type liquid crystal display device, 101 is a display control device, 102 is a power supply circuit, and LCD.
Is a liquid crystal display panel, IC-U1, IC-U2, IC-U
3, IC-Un is an upper drain driver (data signal line drive circuit), IC-L1, IC-L2, IC-L3.
IC-Ln is a lower drain driver (data signal line drive circuit), IC-C1, IC-C2, IC-C3, IC
-C4 and IC-C5 are common drivers (scanning signal line drive circuits).

In FIG. 11, a liquid crystal panel control device 10 is shown.
1 is each segment driver (IC-U1 to IC-Un, IC-L1 to IC-Ln) based on a display control signal and display data transferred from the host computer side or the like.
And control each common driver (IC-C1 to IC-Cn).

The power supply circuit 102 generates different voltages of V1 to V6 and supplies the voltages of V1, V2, V3 and V4 to the segment drivers (IC-U1 to IC-Ln).
And supply the voltages of V1, V2, V5 and V6 to the common drivers (IC-C1 to IC-Cn).

A liquid crystal display panel (LCD) includes a pair of glass substrates arranged to face each other with a liquid crystal in between, and a liquid crystal side surface of one glass substrate extends in the X direction and in the Y direction. M common electrodes (scanning signal lines) arranged in parallel are formed, and each of the m common electrodes is
Corresponding common drivers (IC-C1 to IC-Cn)
Connected to.

On the liquid crystal side surface of the other glass substrate, n segment electrodes (data signal lines) extending in the Y direction and arranged in parallel in the X direction are formed.
The n segment electrodes are vertically divided into two, and each of the n segment electrodes divided into two is provided with a corresponding upper segment driver (IC-U1 to IC-).
Un), or each corresponding lower segment driver (IC-L1 to IC-Ln).

The intersection of the plurality of segment electrodes and the plurality of common electrodes constitutes a pixel region, and each upper segment driver (IC-U1 to IC-Un) and each lower segment driver (IC-L1 to IC-Ln) and each common driver (IC-C1 to IC-Cn), to the plurality of segment electrodes, a data signal line drive voltage, and
A scan signal line drive voltage is applied to the plurality of common electrodes to drive the pixels.

In the simple matrix type liquid crystal display device, the driving voltages applied to the plurality of segment electrodes and the plurality of common electrodes are inverted at a predetermined cycle so that no DC voltage is applied to the liquid crystal. A so-called AC drive method is employed.

FIG. 12 is a diagram showing an example of an AC driving method in the conventional STN type simple matrix type liquid crystal display device shown in FIG.

In the example shown in FIG. 12, for example, when the alternating signal (M) is at the high level, the drive voltage of V2 supplied from the power supply circuit 102 is applied to each segment electrode of the display data "1". A drive voltage of V4 supplied from the power supply circuit 102 is applied to each segment electrode of the display data “0”, and each segment of the display data “1” when the alternating signal (M) is at the Low level. The drive voltage of V1 supplied from the power supply circuit 102 is applied to the electrodes, and the drive voltage of V3 supplied from the power supply circuit 102 is applied to each segment electrode of the display data “0”.

Similarly, when the alternating signal (M) is at the high level, the power supply circuit 10 is connected to the selected common electrode.
The drive voltage V1 supplied from the power supply circuit 102 is applied to the non-selected common electrode, and the drive voltage V5 supplied from the power supply circuit 102 is applied to the non-selected common electrode. The drive voltage of V2 supplied from the power supply circuit 102 is applied to the common electrode, and the drive voltage of V6 supplied from the power supply circuit 102 is applied to the unselected common electrodes.

In FIG. 13, the display control device 101 sends each segment driver (IC-U1 to IC-Un, IC-L).
1-IC-Ln) and each common driver (IC-
C1 to IC-Cn) display data (Di
n) and a display control signal (clock (CL1, CL
2) is a diagram showing a timing chart of a frame signal (FLM) and an alternating signal (M)).

Each segment driver (IC-U1 to IC
-Un, IC-L1 to IC-Ln) are the display control device 1
Clock for display data latch input from 01 (CL
By 2), the display data (Din) is taken into the internal logic circuit, and the output timing control clock (CL1)
Thus, the drive voltage of V1 or V2 supplied from the power supply circuit 102 based on the alternating signal (M) is applied to each segment electrode whose display data (Din) for one horizontal line for each segment electrode is "1". Also, 1 for each segment electrode
For each segment electrode whose horizontal display data (Din) is "0", the drive voltage of V4 or V3 supplied from the power supply circuit 102 based on the alternating signal (M) is applied from the liquid crystal drive voltage output circuit to the segment electrode. Output.

In this case, each segment driver (IC
-U1 to IC-Un, IC-L1 to IC-Ln) output a carry signal, and the carry signal of the previous stage is directly input to the carry input of the drain driver of the next stage. The display data fetching operation of the segment driver is controlled to prevent wrong display data from being fetched by the segment driver.

Each segment driver (IC-U1
To IC-Un, IC-L1 to IC-Ln), display control signals other than the clocks (CL1, CL2) and the alternating signal (M) described above are also input as display control signals from the display control device 101. Although input, it is omitted in FIG. 11.

Each common driver (IC-C1 to IC-C
n) is 1 by the frame signal (FLM) input from the display control device 101 and the clock (CL1).
A common electrode driven at every horizontal scanning time is selected by an internal logic circuit, and the voltage V1 or V2 supplied from the power supply circuit 102 based on the alternating signal (M) is applied to the selected common electrode. The liquid crystal drive voltage output circuit outputs the voltage to the common electrode, and to the common electrodes other than the selected common electrode, the voltage of V5 or V6 supplied from the power supply circuit 102 based on the alternating signal (M). The voltage is output from the liquid crystal drive voltage output circuit to the common electrode.

Each common driver (IC-C1 to IC
In C-Cn), as the display control signals input from the display control device 101, display control signals other than the clock (CL1), the alternating signal (M) and the frame signal (FLM) are also input. It is omitted in FIG.

[0019]

In the conventional liquid crystal display device shown in FIG. 11, when the voltage level of the alternating signal (M) is inverted, display unevenness on the display screen of the liquid crystal display panel (LCD), for example, common. White streaks that emit light brightly along the electrodes or black streaks that darken along the common electrodes may occur.

The reason why this phenomenon occurs is that when the voltage level of the alternating signal (M) is inverted, the voltage level of the scanning signal line drive voltage applied to the common electrode greatly changes, and accordingly, the liquid crystal display. The liquid crystal capacity of the panel (LCD) is charged and discharged, but since the liquid crystal capacity is exponentially charged and discharged through a time constant circuit composed of the equivalent internal resistance of the power supply circuit and the liquid crystal capacity, The voltage waveform of the scanning signal line drive voltage applied to the common electrode is distorted,
It is considered that this is because the effective voltage value of the common electrode at the time when the voltage level of the alternating signal (M) is inverted is different from the effective voltage value of the other common electrodes.

Further, in the conventional liquid crystal display device shown in FIG. 11, the number of output timing control clocks (CL1) in one cycle of the frame signal (FLM) is (240 + α) in the VGA system and in the SVGA system. Is (300+
α).

Here, α varies depending on the setting of the display control device 101, and, in the following, the frame signal (FL
The number of clocks (CL1) in one cycle of M) is called the duty number.

FIG. 13 shows the relationship between the clock (CL1) and the frame signal (FLM) in the case of the VGA system. One cycle of the frame signal (FLM) is T of the cycle of the clock (CL1). Then, (240 + α) ×
It becomes T.

Further, in the conventional liquid crystal display device shown in FIG. 11, the alternating signal (M) is generated by counting the clock (CL1) with the counter in the display control device 101, and the predetermined clock (CL1) is generated. The voltage level was supposed to be inverted by the number.

The alternating signal (M) shown in FIG. 13 has its voltage level inverted every time the clock (CL1) is counted 13.

FIG. 14 shows a clock (CL1) in which the duty number is 240 and the voltage level of the alternating signal (M) is inverted.
FIG. 6 is a diagram for explaining the timing at which the voltage level of the alternating signal (M) is inverted for each frame when the number of counts is 13.

The voltage level of the alternating signal (M) shown in FIG. 14 is inverted every 13 counts of the clock (CL1) regardless of the frame period, so that the number of clocks (CL1) in the frame period is not changed. When it is divisible by 13, display unevenness (white streaks or black streaks) occurs every 13 lines on the display screen of the liquid crystal display panel (LCD).

Further, the clock (CL
1) When the number is not divisible by 13, as shown in FIG. 14, the remaining clock (CL1) of each frame period is
Since it is assigned to the beginning of the next frame period, the timing at which the voltage level of the alternating signal (M) is inverted moves for each frame period.

Therefore, when the voltage level of the alternating signal (M) is inverted, the display unevenness generated on the display screen of the liquid crystal display panel (LCD) also moves for each frame.

In this case, depending on the combination of the duty factor of the display control device 101 and the cycle of the alternating signal (M), when the voltage level of the alternating signal (M) is inverted, the liquid crystal display panel (LCD) is displayed. There is a problem in that the display unevenness generated on the display screen of No. 1 becomes a flicker (or a ripple) that flows upward or downward, significantly impairing the display quality of the display screen of the liquid crystal display panel (LCD).

Therefore, in the conventional liquid crystal display device, the period of the alternating signal (M) is set according to the duty number of the display control device 101, and the voltage level of the alternating signal (M) in each frame period is set. The flicker is made invisible to human eyes by preventing the flicker from being gradually shifted at each frame cycle.

However, since the number of duty of the display control device 101 is different for each display control device 101, the optimum cycle of the alternating signal (M) according to the number of duty for each display control device 101. Had to set.

Then, in order to set the optimum cycle of the alternating signal (M) in accordance with the duty number of each display control device 101, the liquid crystal display panel (LCD) is actually driven to change the alternating signal. There is a problem that it is necessary to set the period (M), and a great deal of labor and time are required for the setting.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an alternating signal which does not cause flicker on the display screen of a liquid crystal display panel in a liquid crystal display device. It is an object of the present invention to provide a technology capable of easily setting the cycle of, and thereby improving the display quality.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0036]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

(1) A liquid crystal display panel having a plurality of pixels arranged in a matrix, a pixel drive means for applying a pixel drive voltage to the plurality of pixels, and a display control device for controlling the pixel drive means. In the liquid crystal display device, the display control device sends a clock for controlling and driving the pixel driving means to the pixel driving means,
An alternating current signal generating means for generating an alternating current signal whose voltage level is inverted every time the clock is counted by a predetermined number is provided, and the pixel driving means outputs a plurality of signals from the pixel driving means according to a high level or a low level of the alternating current signal. In a liquid crystal display device in which the pixel drive voltage value applied to a pixel is changed to invert the polarity of the voltage applied to the pixel, the count value of the clock in the alternating signal generating means and the number of clocks in one frame are predetermined. The count value of the clock in the alternating signal generating means is set so as to satisfy the relational expression of.

(2) In the above-mentioned means (1), the number of clocks in one frame is D, the count value of the clock in the AC signal generating means is N, no is a positive odd number, ne
Is a positive even number, D / N = no + 2, or
It is characterized in that D / N = ne + (N-2).

(3) In the above-mentioned means (1), the number of clocks in one frame is D, the count value of the clock in the AC signal generating means is N, no is a positive odd number, ne
Is a positive even number, D / N = no + 3, or
It is characterized in that D / N = ne + (N-3).

(4) In the above-mentioned means (1), the number of clocks in one frame is D, the count value of the clock in the alternating signal generating means is N (where N is a positive odd number), and n is a positive value. When it is an integer, D / N = n + (N /
2) It is characterized in that it is ± 0.5.

As described above, when the voltage level of the alternating signal (M) is inverted, the display unevenness generated on the display screen of the liquid crystal display panel (LCD) is flicker (or rippling) flowing up or down. The timing at which the voltage level of the alternating signal (M) is inverted in the frame cycle is
The alternating signal (M) is adjusted according to the duty number of the display control device so as not to move gradually in each frame cycle.
By setting the cycle of, it becomes impossible for the human eye to recognize.

The present inventor has examined the duty number of the display control device in which the flicker cannot be recognized by human eyes and the cycle of the alternating signal (M), and as a result, the duty number (1 The number of output timing control clocks (CL1) in the frame) and the number of clocks (CL1) at which the voltage level of the alternating signal (M) is inverted satisfy the predetermined relational expressions described in each of the means. It was discovered that the flickering could not be recognized by human eyes.

The present invention has been made on the basis of the above findings, and according to each of the above means, a predetermined relational expression with respect to the duty number of the display control device (the number of clocks (CL1) in one frame) is given. AC signal (M)
Since the number of clocks (CL1) for inverting the voltage level of is set, the flicker cannot be recognized by human eyes, which causes flicker on the display surface of the liquid crystal display panel (LCD). The display quality of the display screen of the liquid crystal display panel can be improved.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention applied to a simple matrix type liquid crystal display device of the STN mode will be described below in detail with reference to the drawings.

In all the drawings for explaining the embodiments of the invention, components having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted.

The STN type simple matrix type liquid crystal display device according to the embodiments of the present invention is the display control device 1.
The duty number of 01 and the cycle of the alternating signal (M) are
1 except that it is set so as to satisfy a predetermined relational expression.
Since it is the same as the conventional STN type simple matrix liquid crystal display device shown in FIG. 1, its detailed description is omitted.

[First Embodiment of the Invention] FIG. 1 shows that the voltage level of an alternating signal (M) is inverted for each frame in a STN type simple matrix type liquid crystal display device according to a first embodiment of the present invention. It is a figure for explaining an example of timing.

In FIG. 1, the duty number of the display control device 101 is 257, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

Therefore, the duty number of the display control device 101 (the output timing control clock (CL1) number in one frame) is D, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted. When N is set, the relational expression shown in the following expression (1) is established between D and N.

[0050]

## EQU1 ## D / N = 257 ÷ 17 = 15 remainder 2 = quotient (odd number) remainder 2 (1) FIG. 2 is a STN type simple matrix liquid crystal display device shown in FIG. 6 is a schematic diagram showing a change point of the voltage level of the alternating signal (M) for each frame in one drain signal line in FIG.

In FIG. 2, the vertical axis represents the wiring direction of the drain signal line, the horizontal axis represents the frame period (time), and one vertical column represents one frame period.

The numeral 5 indicates the rising edge of the alternating signal (M), the numeral 8 indicates the falling edge of the alternating signal (M), and the numeral 1 indicates the high level or low level of the alternating signal (M). Show.

Note that, in FIG. 2, the downward direction of FIG. 2 indicates the upward direction of the display screen of the liquid crystal display panel (LCD), and actually there are digits of the number of duty, but in FIG. Some are omitted.

As shown in FIG. 2, the first embodiment of the present invention
In the simple matrix type liquid crystal display device of No. 3, 5 and 8 indicating the switching point of the alternating signal (M) are shifted by 2 lines in one frame, that is, the simple matrix type liquid crystal display device of the first embodiment of the present invention. Then, the alternating signal (M) is switched for every two common electrodes between adjacent frames.

In this case, paying attention to only the arrangement of 5, as shown in A of FIG. 2, the intervals between 5 and 5 are greatly separated between adjacent frames, and the alternating signal (M) is generated in a certain frame. Common electrode that rises
In the next frame, the common electrode at which the alternating signal (M) rises is greatly separated.

Similarly, paying attention to the arrangement of only eight, as shown in FIG. 2B, the intervals between adjacent frames are greatly separated from each other, and in a certain frame, the alternating signal (M) is generated. The falling common electrode and the common electrode on which the alternating signal (M) falls in the next frame are largely separated from each other.

In this case, a liquid crystal display panel (LCD)
The flicker that occurs on the display screen cannot be recognized by human eyes, and the flicker that appears on the display screen of the liquid crystal display panel (LCD) cannot be seen.

FIG. 3 is a schematic diagram showing an example of a change point of the voltage level of the alternating signal (M) for each frame in one drain signal line when the liquid crystal display panel (LCD) flickers. is there.

In FIG. 3, the display control device 101
Of 242 and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

In FIG. 3, when attention is paid to the arrangement of only 5 or 8, as shown in C and D of FIG. 2, the interval between 5 and 5 or 8 and 8 between adjacent frames.
And the interval is close to each other, and a common electrode where the alternating signal (M) rises or falls in a certain frame and a common electrode where the alternating signal (M) rises or falls in the next frame. The spaces will come closer.

In this case, a liquid crystal display panel (LCD)
Flickering occurs on the display surface of.

As a result of an actual experiment, a liquid crystal display panel (L
The speed of flickering on the display surface of (CD), the speed obtained from the inclination of the arrangement of 5 or 8 in the schematic diagram shown in FIG.

As described above, in the arrangement of only 5 or 8 in FIG. 2 or FIG. 3, when the distance between 5 and 5 or the distance between 8 and 8 greatly separates, the display of the liquid crystal display panel (LCD) is displayed. Flickering of the surface becomes invisible to the human eye.

FIG. 4 is a schematic diagram showing another example of the change point of the voltage level of the alternating signal (M) for each frame in one drain signal line when the liquid crystal display panel (LCD) flickers. It is a figure.

In FIG. 4, the display control device 101
Is 256, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

In the example shown in FIG. 4, 5 and 8 indicating the switching point of the alternating signal (M) are shifted by one line in one frame, and in this case, shown in E of FIG. As described above, the display surface of the liquid crystal display panel (LCD) slowly flickers.

This is the same even when 5 and 8 indicating the switching point of the alternating signal (M) are deviated on the same common electrode.

Therefore, in the arrangement of only 5 or 8 in FIG. 2 (or FIG. 3), even if the distance between 5 and 5 or the distance between 8 and 8 is increased, the distance between 5 and 8 is at least 2. Lines are needed.

Further, even if the interval between 5 and 5 or the interval between 8 and 8 shown in FIG. 2 is increased, if the time interval (frame period) becomes short, the flickering of the fast flow causes a liquid crystal display panel ( Since it occurs on the display surface of the LCD, in consideration of these things, in order to prevent the flicker on the display surface of the liquid crystal display panel (LCD), the number of duty of the display control device 101 and the alternating signal (M) are changed. The count value of the clock (CL1) whose voltage level is inverted needs to satisfy the relational expression (1).

Further, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the following relational expression (2). Even when the above condition is satisfied, 5 and 8 indicating the switching point of the alternating signal (M) shown in FIG. 2 are shifted by 2 lines in one frame.

[0071]

## EQU00002 ## D / N = quotient (even number) remainder (N-2) (2) FIG. 5 shows the drain in the STN type simple matrix liquid crystal display device according to the first embodiment of the present invention. It is a schematic diagram which shows the other example of the change point of the voltage level of the alternating current signal (M) for every frame in 1 signal lines.

In FIG. 5, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the above equation (2). This is an example of the case where the relational expression is satisfied.

In FIG. 5, the duty factor of the display control device 101 is 253, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

Therefore, the relational expression between the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the AC signal (M) is inverted is as follows (3) ) It becomes like a formula.

[0075]

## EQU00003 ## D / N = 253 ÷ 17 = 14 remainder 15 (= 17-2) = quotient (even number) remainder (N-2) (3) In addition, in FIG. , There are digits for the number of duties, but they are partially omitted in FIG.

Also in the example shown in FIG. 5, 5 and 8 indicating the switching point of the alternating signal (M) are shifted by 2 lines in one frame, and therefore, the liquid crystal display panel (L
The flicker that occurs on the display screen of the CD) cannot be recognized by human eyes, and the flicker that occurs on the display screen of the liquid crystal display panel (LCD) cannot be seen.

As is clear from FIG. 2 and FIG. 5, FIG. 2 and FIG.

In this way, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the above formula (1), Alternatively, when the relation of the expression (2) is satisfied, the flicker that occurs on the display screen of the liquid crystal display panel (LCD) becomes invisible.

That is, when the duty number (D) of the display control device 101 is divided by the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted, the quotient is odd and the remainder is left. 2 or when the quotient is even and the remainder is (N-2), the liquid crystal display panel (LC
The flicker that occurs on the display screen of D) becomes invisible.

[Embodiment 2] The STN type simple matrix type liquid crystal display device of Embodiment 2 of the present invention shows the switching time point of the alternating signal (M) shown in FIG. 2 (or FIG. 5). 5 and 8 are arranged so that there is a shift of 3 lines in one frame.

FIG. 6 is a view for explaining an example of the timing at which the voltage level of the alternating signal (M) is inverted in each frame in the STN simple matrix type liquid crystal display device according to the second embodiment of the present invention. It is a figure.

In FIG. 6, the duty number of the display control device 101 is 258, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

Therefore, between the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted, the following expression (4) is established. The relational expression shown in is established.

[0084]

## EQU00004 ## D / N = 258 ÷ 17 = 15 remainder 3 = quotient (odd number) remainder 3 (4) FIG. 7 shows the drain in the STN type simple matrix liquid crystal display device shown in FIG. It is a schematic diagram which shows the change point of the voltage level of the alternating signal (M) for every frame in one signal line.

In FIG. 7, although there are actually digits corresponding to the number of duties, some of them are omitted in FIG.

As shown in FIG. 7, in the example shown in FIG. 7, 5 and 8 indicating the switching point of the alternating signal (M) are 1
There is a shift of 3 lines in the frame.

In the STN type simple matrix type liquid crystal display device according to the third embodiment of the present invention, the flicker occurring on the display screen of the liquid crystal display panel (LCD) cannot be recognized by human eyes, and the liquid crystal display The flicker that occurs on the display screen of the panel (LCD) disappears.

Further, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the following relational expression (5). Even when the above condition is satisfied, 5 and 8 indicating the switching point of the alternating signal (M) shown in FIG. 7 are shifted by 3 lines in one frame.

[0089]

## EQU00005 ## D / N = quotient (even number) remainder (N-3) (5) FIG. 8 shows the drain in the STN type simple matrix type liquid crystal display device according to the second embodiment of the present invention. It is a schematic diagram which shows the other example of the change point of the voltage level of the alternating current signal (M) for every frame in 1 signal lines.

In FIG. 8, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the above equation (5). This is an example of the case where the relational expression is satisfied.

In FIG. 8, the duty number of the display control device 101 is 252, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

Therefore, the relational expression between the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is as follows (6) ) It becomes like a formula.

[0093]

## EQU00006 ## D / N = 252.div.17 = 14 remainder 14 (= 17-3) = quotient (even number) remainder (N-3) (6) In addition, in FIG. , There are digits for the number of duties, but they are partially omitted in FIG.

Also in the example shown in FIG. 8, 5 and 8 indicating the switching time points of the alternating signal (M) are shifted by 3 lines in one frame, and therefore, the liquid crystal display panel (L
The flicker that occurs on the display screen of the CD) cannot be recognized by human eyes, and the flicker that occurs on the display screen of the liquid crystal display panel (LCD) cannot be seen.

As is clear from FIGS. 7 and 8, FIGS. 7 and 8 are symmetrical with respect to the vertical direction.

As described above, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the equation (4), Alternatively, when the relational expression (5) is satisfied, the flicker that occurs on the display screen of the liquid crystal display panel (LCD) becomes invisible.

That is, when the duty number (D) of the display control device 101 is divided by the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted, the quotient is odd and the remainder is Is 3 or the quotient is even and the remainder is (N-3), the liquid crystal display panel (LC
The flicker that occurs on the display screen of D) becomes invisible.

[Third Embodiment of the Invention] In the STN type simple matrix type liquid crystal display device of the above-mentioned respective embodiments of the present invention, the switching point of the alternating signal (M) shown in FIG. 2 (or FIG. 5) is shown. Although 5 and 8 are arranged so that there is a shift of 2 lines in one frame or 3 lines in one frame, in the STN simple matrix type liquid crystal display device according to the third embodiment of the present invention, The points 5 and 8 at which the alternating signal (M) is switched shown in FIG. 2 (or FIG. 5) are shifted by one line in two frames.

FIG. 9 is a diagram showing an STN type simple matrix type liquid crystal display device according to the third embodiment of the present invention, focusing on an arbitrary drain signal line, and showing the alternating signal (M) for each frame. It is a schematic diagram which shows an example of the change point of a voltage level.

In FIG. 9, the duty factor of the display control device 101 is 264, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

Therefore, between the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted, the following expression (7) is established. The relational expression shown in is established.

[0102]

## EQU7 ## D / N = 264 ÷ 17 = 15 remainder 9 (= 17/2 + 0.5) = quotient (odd number) remainder M / 2 + 0.5 (7) In addition, in FIG. , There are digits corresponding to the number of duties, but they are partially omitted in FIG.

As shown in FIG. 9, the third embodiment of the present invention.
Also in the simple matrix type liquid crystal display device of No. 5, 5 and 8 indicating the switching time point of the alternating signal (M) are shifted by one line in two frames.

Even in this case, the flicker is no longer recognized by human eyes, and the flicker that occurs on the display screen of the liquid crystal display panel (LCD) cannot be seen.

In the example shown in FIG. 9, paying attention to the arrangement of 5 or 8 only, as shown in A ′ and B ′ of FIG. 9, as compared with the example shown in FIG. The distance between 5 and 5 or the distance between 8 and 8 is close to each other. The reason why the flicker cannot be recognized by human eyes in the example shown in FIG. 9 must be sufficiently clarified. However, in the example shown in FIG. 9, the interval between 5 and 5 (or 8 and 8) between adjacent frames, and 5
And 8 (or 8 and 5) are substantially equal to each other, which causes the display unevenness to move up and down, which makes it difficult for human eyes to recognize the flicker.

Further, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the following relational expression (8). Even when the above condition is satisfied, 5 and 8 indicating the switching point of the alternating signal (M) shown in FIG. 9 are shifted by one line in two frames.

[0107]

## EQU00008 ## D / N = quotient (odd number) remainder M / 2-0.5 (8) FIG. 10 shows an STN type simple matrix type liquid crystal display device according to the third embodiment of the present invention. , Drain signal line 1
It is a schematic diagram which shows the other example of the change point of the voltage level of the alternating signal (M) for each frame in this main part.

In FIG. 10, the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are expressed by the equation (8). This is an example of the case where the relational expression is satisfied.

In FIG. 10, the duty number of the display control device 101 is 263, and the count value of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 17.

Therefore, the relational expression between the duty number (D) of the display control device 101 and the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is given by (9) ) It becomes like a formula.

[0111]

D / N = 252 ÷ 17 = 15 remainder 8 (= 17 / 2−0.5) = quotient (odd number) remainder M / 2−0.5 (9) Note that FIG. In FIG. 10, there are actually digits corresponding to the number of duties, but some of them are omitted in FIG.

Also in the example shown in FIG. 10, 5 and 8 indicating the switching point of the alternating signal (M) are shifted by one line in two frames, and therefore, the display screen of the liquid crystal display panel (LCD). The flicker that occurs on the screen cannot be recognized by human eyes, and the flicker that occurs on the display screen of the liquid crystal display panel (LCD) cannot be seen.

As is clear from FIG. 9 and FIG. 10, FIG. 9 and FIG.

Further, in the above formula (7) or formula (8), the quotient may be an even number, but N must be an odd number.

As described above, the duty number (D) of the display control device 101 and the count value (N, where N is a positive odd number) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted are set. Is the above formula (7) or the above formula (8)
When the relational expression is satisfied, the liquid crystal display panel (LC
The flicker that occurs on the display screen of D) becomes invisible.

That is, when the duty number (D) of the display control device 101 is divided by the count value (N) of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted, the quotient (even or odd). When the remainder is (N / 2 ± 0.5), the flicker that occurs on the display screen of the liquid crystal display panel (LCD) cannot be seen.

In the embodiments of the above inventions, the clock (CL) at which the voltage level of the alternating signal (M) is inverted.
The case where the count value (N) of 1) is 17 has been described, but the value of N is not limited to this, and the same effect can be obtained even when the value of N is 13, 19, 21 to 32. Play.

As described above, the invention made by the present inventor is:
Although specifically described based on the embodiments of the present invention, the present invention is not limited to the embodiments of the present invention, and it is needless to say that various modifications can be made without departing from the gist of the present invention. .

[0119]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, in the liquid crystal display device, the alternating signal (M) is supplied so as to satisfy a predetermined relational expression with respect to the number of output timing control clocks (CL1) in one frame. Since the number of clocks (CL1) for reversing the voltage level of is set, the timing at which the voltage level of the alternating signal (M) is reversed in each frame cycle is prevented from gradually moving in each frame cycle. Therefore, the flicker that the display unevenness generated on the display screen of the liquid crystal display panel moves up and down will not be recognized by human eyes.

(2) According to the present invention, in the liquid crystal display device, flicker does not occur on the display surface of the liquid crystal display panel, and the display quality of the display control device can be improved.

(3) According to the present invention, in the liquid crystal display device, it is not necessary to adjust the cycle of the alternating signal according to the duty number of the display control device.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a timing at which a voltage level of an alternating signal (M) is inverted in each frame in a STN type simple matrix type liquid crystal display device according to a first embodiment of the present invention. .

FIG. 2 is a schematic diagram showing a change point of a voltage level of an alternating signal (M) for each frame in one drain signal line in the STN type simple matrix type liquid crystal display device shown in FIG.

FIG. 3 is a schematic diagram showing an example of a change point of a voltage level of an alternating signal (M) for each frame in one drain signal line when a liquid crystal display panel (LCD) flickers.

FIG. 4 is a schematic diagram showing another example of the change point of the voltage level of the alternating signal (M) for each frame in one drain signal line when flicker occurs in the liquid crystal display panel (LCD). .

FIG. 5 is another example of the change point of the voltage level of the alternating signal (M) for each frame in one drain signal line in the STN simple matrix liquid crystal display device according to the first embodiment of the present invention. It is a schematic diagram which shows.

FIG. 6 is a diagram for explaining an example of the timing at which the voltage level of the alternating signal (M) is inverted in each frame in the STN simple matrix liquid crystal display device according to the second embodiment of the present invention. .

7 is a schematic diagram showing a change point of a voltage level of an alternating signal (M) for each frame in one drain signal line in the STN-type simple matrix type liquid crystal display device shown in FIG.

FIG. 8 is another example of the change point of the voltage level of the alternating signal (M) for each frame in one drain signal line in the STN type simple matrix liquid crystal display device according to the second embodiment of the present invention. It is a schematic diagram which shows.

FIG. 9 is a diagram showing an STN-type simple matrix type liquid crystal display device according to a third embodiment of the present invention, focusing on one arbitrary drain signal line and checking the voltage level of an alternating signal (M) for each frame. It is a schematic diagram which shows an example of a change point.

FIG. 10 shows a drain signal line 1 in an STN type simple matrix liquid crystal display device according to a third embodiment of the present invention.
It is a schematic diagram which shows the other example of the change point of the voltage level of the alternating signal (M) for each frame in this main part.

FIG. 11 is a block diagram showing a schematic configuration of a conventional STN type simple matrix liquid crystal display device.

12 is a diagram showing an example of an AC driving method in the conventional STN-type simple matrix type liquid crystal display device shown in FIG.

FIG. 13 is a diagram showing a timing chart of display data and display control signals sent from the display control device to each segment driver and each common driver.

FIG. 14 is an alternating signal (M) for each frame when the number of duty is 240 and the count number of the clock (CL1) at which the voltage level of the alternating signal (M) is inverted is 13;
FIG. 6 is a diagram for explaining the timing at which the voltage level of 1 is inverted.

[Explanation of symbols]

101 ... Display control device, 102 ... Power supply circuit, LCD ... Liquid crystal display panel (LCD), IC-U1 to IC-Un, I
C-L1 to IC-Ln ... Drain driver, IC-C1
-IC-C5 ... Common driver.

Claims (4)

[Claims] 1. A liquid crystal display panel having a plurality of pixels arranged in a matrix, a pixel drive means for applying a pixel drive voltage to the plurality of pixels, and a display control device for controlling the pixel drive means. A liquid crystal display device,
The display control device sends a clock for controlling and driving the pixel driving means to the pixel driving means, and also generates an alternating signal generating means for generating an alternating signal whose voltage level is inverted every time the clock is counted by a predetermined number. A liquid crystal having a pixel drive voltage value applied from the pixel drive means to the plurality of pixels in accordance with a high level or a low level of the alternating signal to invert the polarity of the voltage applied to the pixel. In the display device, the clock count value in the AC signal generation means is set so that the clock count value in the AC signal generation means and the number of clocks in one frame satisfy a predetermined relational expression. Liquid crystal display device. 2. The number of clocks in one frame is D, the count value of the clocks in the alternating signal generating means is N,
When no is a positive odd number and ne is a positive even number, D / N =
The liquid crystal display device according to claim 1, wherein no + 2 or D / N = ne + (N-2). 3. The number of clocks in one frame is D, and the count value of the clocks in the alternating signal generating means is N.
When no is a positive odd number and ne is a positive even number, D / N =
The liquid crystal display device according to claim 1, wherein no + 3 or D / N = ne + (N-3). 4. The number of clocks in one frame is D, and the count value of the clocks in the alternating signal generating means is N.
(However, N is a positive odd number), when n is a positive integer, D
The liquid crystal display device according to claim 1, wherein /N=n+(N/2)±0.5.