JP3034536B2 - Liquid crystal display - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and in particular, to a liquid crystal driving method for obtaining a good display quality without a decrease in luminance due to a display pattern in a simple matrix liquid crystal display device. And its device.

[Conventional technology]

Conventionally, in a simple matrix type liquid crystal display device, the latest technology of liquid crystal, published by the Industrial Research Committee, P106-109
The driving is performed by the voltage averaging driving method as described in (1).
According to this method, a constant voltage is applied regardless of the display pattern on the liquid crystal display. However, depending on the type of display screen, the frequency component of the voltage waveform applied to the liquid crystal is different, and there is a problem that the luminance is reduced. The problems of the prior art will be described below with reference to FIGS.

FIG. 2 is a block diagram showing a configuration of a conventional liquid crystal display device, wherein 1 is display data having a 4-bit width, 2 is a data latch clock, 3 is a horizontal clock, and 1 of a horizontal clock 3 is shown.
In the cycle, the display data 1 synchronized with the data latch clock 2 is sent for one horizontal. That is, assuming that the number of horizontal display dots is 640 dots, the display data 1 is 160 times four bits at a time.
Will be sent. Reference numeral 4 denotes a head signal for instructing display of a head line of a display, and 5 denotes X driving means. The display data 1 is fetched for one horizontal line by a data latch clock 2 and thereafter output to the liquid crystal panel by one horizontal line by a horizontal clock 3. I do. 6 is X display voltage, 7 is X non-display voltage, X1 to X640
Is an X display signal. According to the content of each 640 dots of the display data 1 for one line fetched by the X drive means 5, when the data is "1" indicating display, the X display voltage 6 is not displayed. In the case of "[phi]", the X non-display voltage 7 is selected and output as X display signals X1 to X640. In this embodiment, a voltage of V _Xon is applied to the X display voltage 6 and a voltage of V _Xoff is applied to the X non-display voltage 7. 8 is a Y driving means, 9 is a Y selection voltage, 10 is a Y non-selection voltage, Y1 to Y200 are line selection signals, a V _Yon voltage is applied to the Y selection voltage 10, and a V _Yoff voltage is applied to the Y non-selection voltage 11. Voltage is applied. The Y driving means 8 captures the head signal 4 with the horizontal clock 3, sets the line selection signal Y1 to V _Yon which is a selection voltage, and sets the other line selection signals to V _Yoff . Next, when the horizontal clock 3 is input, the line selection signal Y1 becomes V
_Yoff next line selection signal Y2 is V _Yon, and the following repeat this, the line selection signal Y1, sequentially according to the horizontal clock 3 ～Y200, will turn the V _Yon. Reference numeral 20 denotes a liquid crystal panel, which forms dots to be displayed at intersections of line selection signals Y1 to Y200 and X display signals X1 to X640, and performs display and non-display based on the effective value difference of the voltage at each intersection.

FIG. 3 is a block diagram of an example of the configuration of the X driving means 5, wherein 21 is X data shifting means, 22 is shift data,
The data shift means 21 takes in the display data 1 for one horizontal (640 dots) at the falling edge of the data latch clock 2 and outputs it as shift data 22. Reference numeral 23 denotes data latch means, and reference numeral 24 denotes latch data. The data latch means 23 takes in the shift data 22 at the falling edge of the horizontal clock 3 and outputs it as latch data 24. Reference numeral 25 denotes X voltage selection means, which is "1" and "φ" indicated by each data of 640 dots of the latch data 24, and is "1" for X _Xon and "φ" of the X display voltage 6. Is V _Xoff of X non-display voltage 7
Is selected and output as X display signals X1 to X640. 4th
The figure is a block diagram of an example of the configuration of the Y driving means 8. Reference numeral 26 denotes a Y data shift means which captures the "1" state of the head signal 4 at the falling edge of the horizontal clock 3 and changes the shift output YO1 to "1".
And then shift output YO in order according to horizontal clock 3.
2, YO3… and “1” shift. Reference numeral 27 denotes a power selection means, which is a shift output YO1 to YO200. For each output "1", V _Yon of the Y selection voltage 9 and for Y, the Y non-selection voltage 10
Select the V _Yoff, respectively output as a line selection signal Y1～Y200.

FIG. 5 is a diagram showing a display pattern of a part of the liquid crystal panel 20. In FIG.
X1 to X3, a dot at the intersection of the line selection signal Y1~Y3 L _11, L ₁₂
... it is indicated by L _31. FIG. 6 is a timing chart showing the driving waveforms of the X display signals X1 to X3 and the line selection signals Y1 to Y3 at the time of the display shown in FIG. 5, and FIG. 7 is a dot chart at the time of the display shown in FIG. FIG. 6 is a diagram showing voltage waveforms applied to L11, L12, and L13. FIG. 8 is a diagram showing an effective voltage ratio applied to each dot of the liquid crystal and a luminance characteristic.

In FIG. 2, the X driving means 5 has the configuration shown in FIG. 3, and the X data shift means 21 converts the display data 1 into one line 64 at the falling edge of the data latch clock 2.
0 dots are captured, and at the falling edge of the horizontal clock 3 thereafter, the captured data of 640 dots for one line is latched by the data latch means 23, and "1" and "φ" of each data are read.
, The voltage of V _Xon or V _Xoff is output to the X voltage selection means 25 as the X display signals X1 to X640. At this time, the data of the next line is fetched by the X data shift means 21, and the output of the X drive means 5 includes the X display signals X1 to X6 one line at a time in accordance with the falling edge of the horizontal clock 3.
The content will be output to 40. Y driving means 8
4, the X driving means 5 outputs the contents of the first line data to the X display signals X1 to X640 at the falling edge timing of the horizontal clock 3, and the Y data shifting means 26 The “1” state of the top signal 4 is latched and Y
The voltage selection means 27 _{sets the} line selection signal Y1 to V _Yon . Thereafter, at the same time as the X driving means 5 sequentially outputs the second and third lines in accordance with the horizontal clock 3, the Y driving means 8 changes the "1" state from the shift output YO1 by the Y data shifting means 26. Since the voltages are sequentially shifted from YO2 and YO3, the voltage of V _Yon is also sequentially shifted from the line selection signal Y1 to Y2 and Y3. By repeating the above scanning, one screen is displayed. Therefore, as shown in FIG.
Dots L11, L21, L3 in the first column to which the display signal X1 is connected
Each dot of 1 ... repeats display and non-display, X display signal X
If all the dots in the second column L12, L22, L32 ... connected to 2 are displayed, and all the dots L13, L23, L33 ... in the third column connected to the X display signal X3 are hidden, The X display signals X1 to X3 and the line selection signals Y1 to Y3 output from the X driving means 5 and the Y driving means 8 have timings according to the horizontal clock 3, as shown in FIG. Now, with reference to the V _Yoff, When _{V Xon = V Yoff + V a} V Xoff = V Yoff -V a V Yon = V Yoff -V Y, and has a display state of FIG. 5. The voltage waveform shown in FIG. 7 is applied to the dots L11 and L12 and the dot L13 in the non-display state. Since the liquid crystal operates at the effective value of the applied voltage, each dot is The effective value is applied at the effective voltage ratio shown by. As shown in FIG. 8, when the effective value ratio is V _on , the display of 100% brightness, V
_{When off,} the display is in a non-display state with 10% brightness.

As described above, the display or non-display of a dot is applied even when other dots are displayed or not displayed when the line selection signal of the line where the dot exists is V _Yoff of the Y non-selection voltage 10. Since the absolute value of the voltage is the same, it is determined by the voltage value of the X display signal when the line selection signal is V _{Yon of the} Y selection voltage 9.

[Problems to be solved by the invention]

The above prior art does not consider the frequency component of the voltage waveform applied to the dot. For example, the seventh
Effective voltage value ratio applied to the L11, L12 figure is identical to V _on, as described above, in the liquid crystal panel, as shown in FIG. 9, a high frequency component of the voltage waveform applied to the dots It happens when the effective voltage ratio - the brightness characteristic is shifted, even compared with the luminance of L12 in effective voltage ratio of the same V _on, L11
There is a problem that the brightness of the image is reduced.

An object of the present invention is to provide a liquid crystal display device capable of obtaining a good display without a decrease in luminance due to a display pattern.

[Means for solving the problem]

In order to achieve the above object, X voltage selector means for selecting a drive voltage to be applied to the X drive means, Y voltage selector means for selecting a drive voltage to be applied to the Y drive means are provided, and a horizontal retrace period is provided. By providing a new voltage to be applied to the liquid crystal panel during the flyback period, the difference between the frequency components of the applied voltage waveform depending on the display pattern is reduced.

[Action]

X voltage selector means, in the horizontal retrace period, then X display voltage, the X non-display voltage both the same voltage value V _B, the display period,
It is assumed that the X display voltage is V _Xon and the X non-display voltage is V _Xoff . Similarly, in the Y voltage selector means, the Y selection voltage, Y
Non-selection voltage both the V _B of the same voltage as the X-side, V _Yon the Y selection voltage during the display period, to operate the Y non-selection voltage to the V _Yoff, horizontal retrace period is applied to the dot Voltage becomes "φ", and the voltage waveform becomes a waveform that always returns to "φ" every horizontal. Therefore, its frequency component hardly changes depending on the display pattern. Further, since the applied voltage during the horizontal blanking period is "φ", the effective value of the voltage applied to the dot is not changed, so that the contrast is not changed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1, 10 to 14. FIG. 1 is a block diagram of an embodiment of the present invention, wherein 1 to 10, 20 are the same as those in FIG. 2, 11 is a horizontal retrace signal indicating a horizontal retrace period of "1", and 12 is a horizontal retrace signal. The X voltage selector, 13 is an X on voltage, 14 is an X off voltage, 15 is an X retrace voltage, and the X voltage selector 12 sets the X retrace voltage 15 to X when the horizontal retrace signal 11 is "1". The display voltage 6 and the X non-display voltage 7 are output.
Then, the X-off voltage 14 is output to the X non-display voltage 7. 16 is Y
A voltage selector, 17 is a Y on voltage, 18 is a Y off voltage, 19 is a Y retrace voltage, and a Y voltage selector 16 is a horizontal retrace signal.
When 11 is "1", the Y return voltage 19 is output to the Y selection voltage 9 and the Y non-selection voltage 10, and when "11", the Y on voltage 17 is changed to the Y selection voltage 9 and the Y off voltage 18 is changed to the Y selection voltage 9. Output to Y non-selection voltage. In this embodiment, the voltages V _Xon , V _Xoff , V _Yon , and V _Yoff are applied to the X on voltage 13, the X off voltage 14, the Y on voltage 17, and the Y off voltage 18, respectively. , to the Y retrace voltage 19, a voltage of V _B both have been applied.

FIG. 10 is a timing chart showing the relationship among input display data 1, data latch clock 2, horizontal clock 3, horizontal retrace signal 11, and top line signal 4, and FIG. 11 is a display pattern on the liquid crystal panel 20. , And the dots at the intersections of the X display signals X1 to X3 line selection signals Y1 to Y3 are indicated by L11, L12... L32, L33.

FIG. 12 shows a line selection signal Y1 output from the Y driving means 8.
FIG. 13 is a diagram showing output waveforms of Y3 to Y3. FIG. 13 shows X display signals X1 to X3 output from X driving means 5 for displaying the display pattern of FIG.
FIG. 14 is a diagram showing the output waveform of X3. FIG. 14 shows a dot selection signal L1 in each output waveform of the line selection signal of FIG. 12 and the X display signal of FIG.
FIG. 3 is a diagram illustrating voltage waveforms applied to 1, L12, and L13.

In FIG. 1, the display data 1 is synchronized with the data latch clock 2 as shown in FIG.
160 data is transmitted in 4-bit units during one cycle of the data latch clock 2, and is captured by the X driving means 5 at the falling edge of the data latch clock 2, and the captured 640 dots (4 × 160 = 4 × 160 =
640) is simultaneously taken into the latch means in the X drive means 5 at the falling edge of the horizontal clock 3, and according to the value of the data, the X display voltage 6 when "1" and the X display voltage 6 when "φ". The X non-display voltage 7 is output as X display signals X1 to X640. At this time, the X driving means 5 takes in the data of the next line, and changes the X display voltage 6 or the X non-display voltage 7 according to the data at the falling edge of the next horizontal clock 3 according to the data.
Output to ~ X640. Therefore, the X driving means 5 outputs the X display voltage 6 or the X non-display voltage 7 to the X display signals X1 to X640 in synchronization with the falling edge of the horizontal clock 3 and sequentially according to the data of one line. Become. Further, the X driving means 5 applies a voltage according to the data to the liquid crystal panel 20 at the falling edge of the horizontal clock 3 after fetching the data of the first line. As shown in the figure, at the falling edge of the next horizontal clock 3 to which the data of the first line is input, the "1" state of the head signal 4 is latched, and the line selection signal Y1 is changed to the Y selection voltage 9
And other line selection signals Y2 to Y200 are Y non-selection signals.
Assume 10 Thereafter, the value of the Y selection voltage 9 is sequentially shifted to the line selection signals Y2, Y3... Y200 at the falling edge of the line clock 3.

By the operations of the X driving means 5 and the Y driving means 8 described above, the output voltage of the line selection signals Y1 to Y200 becomes Y.
The X driving means outputs a voltage according to the data of the line of the liquid crystal panel 20 having the selection voltage 9, and this operation is sequentially performed by 1
One screen is displayed by repeating from the line to the 200th line.

Next, the voltage actually applied to each dot of the liquid crystal panel 20 will be described.

Now, in the liquid crystal panel 20, as shown in FIG. 11, the dots L11, L21, L31... Connected to the X display signal X1 have display and non-display repetitions connected to the X display signal X2. Dots are displayed only on the dots L12, L22, L32.
The dots L13, L23, L33,... Connected to 3 have a display pattern in which only non-display is performed.

_Assuming that V _Xon = V _Yoff + V _a V _Xoff = V _Yoff −V _a V _Yon = V _Yoff −V _Y V _B = V _Yoff −V _Y / 2 with _{respect to} V _Yoff , the liquid crystal panel 20 becomes the eleventh. In the case of the display pattern shown in the figure, the X display signal X output from the X driving means 5 and the Y driving means 8
The outputs of 1 to X640 and the line selection signals Y1 to Y200 are as follows.

The line selection signals Y1 to Y3 output from the Y driving means 8 are
As shown in FIG. 12, when the horizontal retrace signal 11 is "1", the Y voltage selector 16 sets the Y selection voltage 9 and the Y non-selection voltage 10 to Y.
Since the V _B of retrace voltage 19, V _B, and the horizontal blanking signal 11
Is “φ” during the display period, the Y voltage selector 16
The selection voltage 9 is V _{Yon of} the Y-on voltage 17, and the Y non-selection voltage 10 is
Since it becomes V _{Yoff of} Y off voltage 18, the line selection signal Y1
Is V _Yon for the first line, V _Yoff for the other lines, the line selection signal Y2 is V _{Yon for} the second line, V _Yoff for the other lines, and the line selection signal Y3 is the third line. At time V _Yon , V _Yoff at other lines. Also, X
As shown in FIG. 13, when the horizontal retrace signal 11 is "1", the X display signals X1 to X3 output from the driving means 5 are output by the X voltage selector 12 by the X display voltage 6, the X non-display voltage. 7, since the voltage V _B of X retrace voltage 15, X display signal X1~X3 both V _B, and the display period of the horizontal blanking signal 11 is "phi" is X display voltage 6, X oN Since V _{Xon of} the voltage 13 and X non-display voltage 7 become V _Xoff of the X off voltage 14, the X display signal is converted to V _Xon , by “1” and “φ” of the display data 1 captured by the X driving means 5.
In order to make V _Xoff , the X display signal X1 alternates V _Xon and V _Xoff line by line, and the X display signal X2 is all lines.
The V _Xon and X display signals X3 take the voltage values of all the lines V _Xoff .

At this time, the voltage waveform applied to each dot L11, L12, L13 of the liquid crystal panel 20 is as shown in FIG. 14, and the relative ratio of each voltage effective value is Which is the same as the value shown in the conventional example.

However, as is apparent from FIG. 14, a horizontal retrace period is provided, at which time the X display signals X1 to X640 and the line selection signal Y
And 1~Y200 co V _B, due to the voltage application "phi" to each dot of the liquid crystal panel 20, the frequency component of the voltage waveform applied to each dot is the same, regardless of the liquid crystal of the luminance characteristic to the display pattern It became possible to make it constant.

In the present embodiment, the selection of the driving voltage by the horizontal retrace signal 11 is provided outside the X driving means 5 and the Y driving means 8, but the selection function can be realized by providing the selecting function inside each driving means. Next, an embodiment of each driving means in this case will be described.

FIG. 15 is a block diagram of one embodiment of the X driving means 5 when the voltage selection by the horizontal retrace signal 11 is provided inside the driving means. Is the X return voltage
15 when the horizontal retrace signal 11 is “φ”, and according to each data of the 640 dot latch data 24, when the data is “1”, X
X voltage output means for outputting the display voltage 6 and the X non-display voltage 7 when the data is "φ", and the other components are the same as those in FIG.

FIG. 16 is a block diagram of an embodiment of the Y driving means 8 in the case where the voltage selection by the horizontal retrace signal 11 is provided inside the driving means. Reference numeral 31 denotes a case where the horizontal retrace signal 11 is "1". Is the Y return voltage
19, and when the horizontal retrace signal 11 is “φ”, the shift output YO1
For the output that is "1" for ~ YO200,
Y voltage output means for outputting the Y nonselection voltage 10 as the line selection signals Y1 to Y200 for the Y selection voltage 9 and the output of "φ", respectively. The other components are the same as those in FIG.

When the X driving means 5 and the Y driving means 8 shown in FIG. 15 described above are used, the same effect as the liquid crystal display device shown in FIG. 1 can be obtained with the configuration shown in FIG. .

In FIG. 17, X display voltage 6 is V _Xon , X non-display voltage 7 is V _Xoff , X return voltage 15 is V _B , Y selection voltage 9 is V _Yon ,
It is assumed that a voltage of V _Yoff is applied to the Y non-selection voltage 10.

〔The invention's effect〕

According to the present invention, it is possible to make the frequency components of the voltage waveform applied to each dot of the liquid crystal panel the same regardless of the display pattern. No uniform display can be obtained.

[Brief description of the drawings]

1 is a block diagram of a liquid crystal display device according to one embodiment of the present invention, FIG. 2 is a block diagram of one embodiment of a conventional liquid crystal display device, FIG. 3 is a block diagram of one embodiment of X driving means, 4th
FIG. 5 is a block diagram of an embodiment of the Y driving means, FIG. 5 is an example of a display pattern in a liquid crystal panel, FIG. 6 is a timing chart of driving waveforms of a line selection signal and an X display signal, and FIG. FIG. 8 is a timing chart of a voltage waveform applied to the dot of FIG. 8, FIG.
FIG. 9 is a diagram showing a change in an effective value voltage ratio-luminance characteristic due to a difference in a frequency component of a voltage waveform applied to a dot of a liquid crystal panel, FIG. 10 is an input timing diagram to a liquid crystal display device, and FIG. FIG. 12 shows an example of a display pattern on a liquid crystal panel, FIG. 12 is a timing chart of an output waveform of a line selection signal, FIG. 13 is a timing chart of an output waveform of an X display signal, and FIG.
FIG. 15 is a timing chart of a voltage waveform applied to the dots of the liquid crystal panel. FIG. 15 is a block diagram of an embodiment of the X driving means.
FIG. 16 is a block diagram of one embodiment of the Y driving means, FIG. 17 is a diagram showing an example of the X driving means of FIG. 15, and the liquid crystal of one embodiment of the present invention employing the Y driving means of FIG. It is a block diagram of a display device. 1 ... display data, 2 ... data latch clock, 3 ...
... horizontal clock, 4 ... head signal, 5 ... X drive means,
6 ... X display voltage, 7 ... X non-display voltage, 8 ... Y driving means, 9 ... Y selection voltage, 10 ... Y non-selection voltage, 11 ...
Horizontal retrace signal, 12 X voltage selector, 13 X on voltage, 14 X off voltage, 15 X retrace voltage, 16 Y voltage selector, 17 Y on voltage, 18 ... Y off voltage, 19
... Y return voltage, 20... Liquid crystal panel, X1 to X640... X display signal, Y1 to Y200... Line selection signal, 21... X data shift means, 22... Shift data,. Means, 24 latch data, 25 X voltage selection means, 26 Y data shift means, YO1 to YO200 shift output, 27 Y voltage selection means, 29 X voltage output means, 31 ... Y voltage output means.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Onuma 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Within Hitachi Video Engineering Co., Ltd. (72) Toshio Futami 3300 Hayano Mobara-shi, Chiba Pref. Inside plant (72) Inventor Masaaki Kitajima 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-62-200397 (JP, A) (58) Fields investigated (Int.Cl) . ^7, DB name) G09G 3/36 G02F 1/133 G09G 3/20 H04N 5/66

Claims (1)

(57) [Claims] 1. A liquid crystal panel forming display dots between n X electrodes, m Y electrodes, X electrodes and Y electrodes, inputting display data, and applying a voltage according to the display data. In a display device comprising X driving means for driving the X electrode and Y driving means for driving the Y electrode, a horizontal retrace signal indicating a horizontal retrace period is input, and the input horizontal retrace signal is When instructing a horizontal blanking period, an X-ON voltage and an X-OFF voltage for displaying and hiding the display dots of the liquid crystal panel and a retrace voltage irrelevant to the display and non-display of the display dots of the liquid crystal panel X-voltage selecting means for selecting the retrace voltage from the control signal and outputting the signal to the X driving means, and a horizontal retrace signal indicating the horizontal retrace period. When instructing
Displaying the display dots of the liquid crystal panel, selecting the retrace voltage from a Y-on voltage for disabling display, a Y-off voltage, and a retrace voltage independent of display and non-display of the display dots of the liquid crystal panel; Y voltage selecting means for outputting to the Y driving means, wherein the potential of the driving voltage applied from the X driving means is equal to the potential of the driving voltage applied from the Y driving means during the flyback period. Liquid crystal display device.