JP3327802B2 - Liquid crystal image display device and multiplexing drive method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for displaying characters and images and a method of driving the same, and more particularly, to a matrix display device which performs display using two alignment states of liquid crystal and a multiplexing driving method thereof.

[0002]

2. Description of the Related Art In recent years, a flat panel display using liquid crystal, which is thinner, lighter, and consumes less power than a CRT display which has been widely used in the past, has attracted attention. However, even though the power consumption is lower than that of a CRT, it is necessary to realize further power consumption by using some method for effective use of resources.

[0003] Among liquid crystal display elements used for flat panel displays, ferroelectric liquid crystal elements having bistability and quick response to an electric field are expected as high-speed and memory-type display elements. Kaisho 56-10
No. 7216 has been proposed. A large number of driving methods for matrix driving have been proposed, such as Japanese Patent Application Laid-Open No. 2-281233. FIG. 10 shows an example of a conventional drive waveform. In FIG. 10, A is a scanning signal voltage waveform at the time of selection, B is a scanning signal voltage waveform at the time of non-selection, C is an information signal voltage waveform at the time of bright display, and D is an information signal voltage waveform at the time of dark display. . 1H is one horizontal scanning period for determining a display state of a pixel on one scanning electrode.

In a conventional ferroelectric liquid crystal device, when rewriting a display image, the information signal voltage waveforms shown in FIGS. 10C and 10D are always applied to the information signal electrode in order to increase the frame frequency. And applying the selected scanning signal voltage waveform to the scanning signal electrode to be rewritten,
Light and dark were written separately.

[0005]

However, as the screen size and definition of the display device have been increased, the driving load of the liquid crystal panel has increased, and not only the power consumption of the display device has increased, but also the liquid crystal display has been increased. The calorific value of the panel also increases,
The drive margin was reduced due to the influence of the temperature characteristics of the liquid crystal material, and the display quality was sometimes degraded particularly in the high temperature region of the liquid crystal panel at the time of full-screen white display. Also, JP-A-63
No. 155032 discloses a method of addressing two scan electrodes, but it has been difficult to suppress the flicker and the frame period.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a liquid crystal image display device capable of obtaining a higher quality display image with lower power consumption.

[0007]

According to the present invention, there is provided a liquid crystal panel having a scanning signal electrode, an information signal electrode, and a liquid crystal, and an information electrode drive for applying an information signal voltage waveform to the information signal electrode. Means and a scanning electrode driving means for applying a scanning signal voltage waveform to the scanning signal electrode, the information signal voltage waveform applied to the information signal electrode has first information (bright and dark) having a pulse width ΔT. (Selection) pulse and a first information signal voltage waveform (including one information signal electrode) having a polarity opposite to that of the first information pulse after the first information pulse and having a second information pulse having a pulse width ΔT. A case where the pixel at the intersection of the two scanning signal electrodes is bright and dark or dark and bright, and a second information signal voltage waveform including a third information pulse having a pulse width twice as large as ΔT (the pixel Display is light and light or dark and dark It from the case), the scanning signal voltage waveform applied to the scan signal electrodes, the first before the first write pulse and first writing pulse having a pulse width ΔT
A first scan signal voltage waveform including an erase pulse of
The pulse width ΔT shifted by ΔT from the scanning signal voltage waveform
, And a second scan signal voltage waveform including a second erase pulse before the second write pulse. The first and second scan signal voltage waveforms cause the liquid crystal A driving method of simultaneously scanning two scanning signal electrodes of the panel and applying the first or second information signal voltage waveform according to the display state to each of the information signal electrodes is employed.

[0008]

According to the present invention, two scanning lines are sequentially selected within one horizontal scanning period, and two scanning lines are selected for each information signal electrode.
Selection of the display of one pixel. Therefore, on the information electrode driving means side, the pulse width in the information signal voltage waveform, the width of the information pulse portion when two pixels on the same information signal electrode are displayed brightly or darkly (second information signal voltage waveform), etc. The frequency of the information signal voltage waveform can be reduced. As a result, the power consumption of the information electrode driving means can be reduced, and a reduction in driving margin due to a rise in the temperature of the liquid crystal panel and the like, and thus a reduction in display quality can be prevented. On the other hand, one horizontal scanning period is doubled, but since two scanning lines are sequentially scanned during one horizontal scanning period, the rewriting time (frame frequency) of one screen is not different from the conventional one. In addition, since the scanning electrode driving means simultaneously drives two scanning electrodes, the power consumption of the scanning electrode driving means itself doubles at first glance, but the actual power consumption is also lower than that of the conventional one due to the lower frequency of the driving waveform. In addition to being substantially equal, this scan electrode driving means drives two out of several hundred or more scan lines, so that the power consumption is limited to the information driving all information signal electrodes in each horizontal scanning period. The power consumption of the electrode driving means is only a few tenths or less, and even if the power consumption of the scanning electrode driving means is increased, it is negligible in view of the power consumption of the entire display device. This makes it possible to lower the power consumption and obtain a higher quality display image.

In the first information signal voltage waveform,
Since the first information pulse and the second information pulse have opposite phases and the same pulse width, the average voltage of the information pulse portion becomes zero. Therefore, in the first information signal voltage waveform,
The first and second auxiliary pulses for increasing the drive margin by making the average value of the information signal voltage waveform substantially zero can be omitted. If these auxiliary pulses are omitted, power consumption can be further reduced.

[0010]

【Example】

(First Embodiment) Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 shows a first embodiment of a drive waveform according to the present invention. FIG. 1 shows a first scanning signal voltage waveform (hereinafter referred to as COM1) at the time of selection, a second scanning signal voltage waveform (hereinafter referred to as COM2), a scanning signal voltage waveform at the time of non-selection, and a first information signal voltage. Waveform (hereinafter referred to as SEG1), second information signal voltage waveform (hereinafter referred to as SEG2), third information signal voltage waveform (hereinafter referred to as SEG3), and fourth information signal voltage waveform (hereinafter referred to as SEG4).
Is shown. 1H indicates one horizontal scanning period, and ΔT indicates a selection (light / dark selection) period. These are the same as reference numerals 1H and ΔT in FIG. 10 showing a conventional drive waveform. The three types of scanning signal voltage waveforms at the time of selection in FIGS. 1 and 10 basically have substantially the same properties. Black (dark) erasing (writing) is performed at the first V1 level (erasing pulse), and V2 With the level (write pulse), selection of light and dark (white and black) is performed by the V3 and V4 levels (selection pulse) of the information signal voltage waveform.

The first 1H portion of each scanning signal waveform is for surely erasing pixels on the scanning electrodes to which the waveform is applied. Therefore, if sufficient erasing can be performed with the first V1 pulse of 1H in the latter half, 1
The H pulse is not required. The V5 level correction pulse applied as necessary is disclosed in Japanese Patent Application Laid-Open No. 2-28123.
3 to improve the drive margin.

As can be seen from FIG. 1, the phase of the erase pulse, the write pulse and the correction pulse of COM2 is shifted by ΔT with respect to COM1, and COM1 has the VC level (reference potential) and COM2 after the correction pulse. Is provided with a VC level (reference potential) before the erase pulse. Although it depends on the optical axis direction of the polarizing plate of the liquid crystal panel, by giving the V3 level of the information signal voltage waveform during each writing pulse period (period of V2) of this scanning signal voltage waveform, a bright display is obtained, and the V4 level is given. This results in a dark display.
That is, in the combination of COM1 and SEG1 shown in FIG. 1, dark display is performed, and in the combination of COM2 and SEG1, bright display is performed. COM
1, the opposite is true for COM2 and SEG2. SE
In G3, the bright display is always performed since it is at the V3 level in both the selection pulse periods COM1 and COM2. The opposite is true for COM1, COM2 and SEG4, and the display is always dark. FIG. 2 shows a case where two non-adjacent scanning signal electrodes of the matrix panel are simultaneously selected and driven by each scanning signal voltage waveform and information signal voltage waveform of the first embodiment of the present invention shown in FIG. This shows the light and dark display results. As shown here, according to the driving waveform of this embodiment, even if two scanning signal electrodes are simultaneously scanned, “bright and dark” (SEG2) and “dark and bright” are applied to the pixels on each information signal electrode. (SEG1),
4 for “bright, bright” (SEG4) and “dark, dark” (SEG3)
Pixel combinations of different combinations can be displayed.

Here, the waveform of the first embodiment of the present invention shown in FIG. 1 is compared again with the conventional driving waveform shown in FIG. Assuming that the time width of the selection period ΔT is equal, 1H (one horizontal scanning period) of the waveform of the first embodiment shown in FIG. 1 is twice as long as the driving waveform of FIG. . That is, according to the waveform of the first embodiment of the present invention, the time for rewriting the pixel on one scanning signal electrode is twice as long as the time for rewriting the pixel on one scanning signal electrode by the driving waveform of FIG. Will be. However, according to the waveform of the first embodiment of the present invention, 2
Since the pixels on the scanning signal electrodes can be rewritten within the same 1H period, the time for rewriting one screen of the display device and the frame frequency are the same as in the case of displaying an image using the driving waveform of FIG. Become. And as mentioned above,
Since one horizontal scanning period is doubled, the frequency of the information signal voltage waveform always applied to the information signal electrode may be １ ／, so that the load of driving the liquid crystal panel greatly depending on the frequency of the information signal voltage waveform is reduced. Decrease. For example, in the case of full-screen white display in which the image display quality has been degraded due to an increase in load, the power consumption can be reduced to almost half, and the calorific value of the liquid crystal panel itself also decreases. Thus, a sufficient driving margin can be obtained even in a high temperature range of the liquid crystal panel, and a high-quality display image can be obtained.

FIG. 3 is a block diagram of an image display device according to an embodiment of the present invention. In the figure, reference numeral 307 denotes a graphic controller, and data with an address transmitted from the graphic controller 307 is a drive control circuit 3 having a frame memory.
05 is input. The drive control circuit 305 converts the data on the scan line for display into address data and display data, respectively, and sends them to the scan signal control circuit 304 and the information signal control circuit 306. The scanning signal application circuit 302 generates a scanning signal voltage waveform according to the address data,
The voltage is applied to the scanning signal electrode of the image display unit 301. The information signal application circuit 303 generates an information signal voltage waveform according to the display data and applies the information signal voltage waveform to the information signal electrode of the image display unit 301.

(Second Embodiment) A drive waveform according to a second embodiment of the present invention will be described below. FIG. 4 shows a waveform according to the second embodiment of the present invention. This waveform is shown in FIG.
The auxiliary pulse of the second information signal voltage waveform has a VC level. According to this waveform, compared to the case where the information signal electrode is driven by using the waveform of the first embodiment, the power consumption is further reduced by the V3 and V4 levels of the auxiliary pulse being the VC level. Become. Other configurations are
This is the same as the first embodiment.

(Third Embodiment) FIG. 5 shows the application timing of a signal applied to a scanning electrode used in a liquid crystal display according to a third embodiment of the present invention. The scan selection signal is the same as that of the first embodiment, and is indicated by a relative potential based on the voltage VC applied to the scan electrode at the time of non-selection. In this embodiment, the pixel of the image display unit is 1280 ×
Since the number is 1024, the number of horizontal scanning lines, that is, the scanning electrodes are S1, S2, S3, S4,.
There are 24 1024 lines. In the first embodiment, the first and second scan selection signals are simultaneously applied to two non-adjacent scan electrodes. In this embodiment, two adjacent scan electrodes (S1, S2) are applied. , (S3, S4), ‥‥‥,
(S1023, S1024) are configured to simultaneously apply the scan selection signal. In addition, the scanning electrodes (S1, S
2) A pulse for erasing the pixel on the next selected scanning electrode (S3, S4) rises during the 1H period that determines the display state of the upper pixel, and erasing is performed during this period.

Although not shown, the scanning electrodes (S
An erase pulse is applied to the scan electrodes (S5, S6) during the 1H period that determines the display state of the pixel on (3, S4). That is, a pulse for erasing is applied to the (n + 2) and (n + 3) th scan electrodes at the same time as the scan selection signal is applied to the (n) and (n + 1) th scan electrodes. As the information signal, the same voltage waveform as that shown in FIG. 1 or FIG. 4 can be used.

(Fourth Embodiment) FIG. 6 shows the application timing of signals applied to the scanning electrodes of a liquid crystal display according to a fourth embodiment of the present invention. In the example of FIG. 6, unlike the example of FIG. 5, the first half of the scan selection signal applied to a certain scan electrode does not temporally overlap with the second half of another scan selection signal.

(Fifth Embodiment) FIG. 7 is a table showing the application timing of a scan selection signal used in a liquid crystal display according to a fifth embodiment of the present invention. FIG.
Is an example in which first and second scan selection signals (COM1, COM2) are simultaneously applied to two adjacent scan electrodes. The application timing is such that one frame for forming one screen is composed of four field scanning periods, and in the first field, the scanning signals (COM1, COM1) are sequentially applied to the 8n + 1-th and 8n + 2-th scanning electrodes. CO
M2) is applied.

Similarly, in the second field, two scanning electrodes (8n + 5th and 8n + 6th) not adjacent to the scanning electrode selected in the previous field are sequentially selected. Next, in the third field, the 8n + 3rd and 8n + 4th scanning electrodes are used, and in the fourth field, the 8n + 7th and 8th + 8th scanning electrodes are used.
The (n + 8) th scanning electrode is selected. This method is shown in FIG.
The flicker suppression effect is superior to the above method.

As shown in FIG. 5, the first half of the scan selection signal applied to the later-selected scan electrode and the latter half of the scan selection signal applied to the previously selected scan electrode are compared with each other. If the scanning electrodes are selected in the order shown in FIG. 7 while overlapping, the one-frame scanning period is further reduced, and the flicker becomes less noticeable.

(Sixth Embodiment) FIG. 8 is a table showing the application timing of a scan selection signal used in a liquid crystal display according to a sixth embodiment of the present invention. FIG.
Is an example in which the first and second scan selection signals (COM1, COM2) are simultaneously applied to two scan electrodes that are not adjacent to each other. The application timing is such that one frame for forming one screen is composed of four field scanning periods, and in the first field, 8n + 1 and 8n + 1
The scan selection signal (C
OM1, COM2).

Similarly, in the second field, two scan electrodes (8) adjacent to the scan electrode selected in the previous field are used.
n + 2 and 8n + 6) are sequentially selected. Then the third
In the field, the 8n + 3rd and 8n + 7 scanning electrodes are used, and in the fourth field, the 8n + 4th and 8n + scanning electrodes are used.
The eighth scanning electrode is selected.

(Seventh Embodiment) FIG. 9 is a table summarizing the application timing of a scan selection signal used in a liquid crystal display according to a seventh embodiment of the present invention. FIG.
Is an example in which the first and second scan selection signals (COM1, COM2) are simultaneously applied to two scan electrodes that are not adjacent to each other. The application timing is such that one frame for forming one screen is composed of four field scanning periods, and in the first field, 8n + 1 and 8n + 1
The scan selection signal (C
OM1, COM2).

Similarly, in the second field, two scanning electrodes (8n + 3rd and 8n + 7th) not adjacent to the scanning electrode selected in the previous field are sequentially selected. Next, in the third field, the 8n + 4th and 8n + 8 scanning electrodes are used, and in the fourth field, the 8n + 2nd and 8n scanning electrodes are used.
The + 7th scanning electrode is selected. This method is superior to the methods shown in FIGS. 7 and 8 in flicker suppression effect.

Also, as shown in FIG. 5, the first half of the scan selection signal applied to the later selected scan electrode and the latter half 1H of the scan selection signal applied to the previously selected scan electrode are compared. If they are overlapped and the scanning electrodes are selected in the order shown in FIG. 7, the one-frame scanning period is further reduced, and the flicker becomes less noticeable.

As described above, according to each embodiment of the present invention, a liquid crystal panel in which a scanning signal electrode and an information signal electrode are arranged on a matrix with each other and a liquid crystal is sandwiched between the scanning signal electrode and the information signal electrode. In a liquid crystal image display device having driving means for applying an information signal voltage waveform to a signal electrode and driving means for applying a scanning signal voltage waveform to a scanning signal electrode, the information signal voltage waveform applied to the information signal electrode has a pulse width. The first information (light / dark selection) pulse of ΔT and the first information pulse after the first information pulse have opposite polarities and a pulse width ΔT.
, A first auxiliary pulse having a polarity opposite to that of the first information pulse before the first information pulse and shorter than or equal to ΔT, and a second information pulse of the second information pulse. A first information signal voltage waveform composed of a second auxiliary pulse having a polarity opposite to that of the subsequent second information pulse and shorter than or equal to ΔT and having a pulse width twice as large as ΔT; A third information pulse, a third auxiliary pulse having a pulse width of ΔT having a polarity opposite to that of the third information pulse before the third information pulse, and a third information pulse after the third information pulse. And a second information signal voltage waveform composed of a fourth auxiliary pulse having a pulse width of ΔT having a polarity opposite to that of the second information signal. The scanning signal voltage waveform applied to the scanning signal electrode has a pulse width Δ
A first scan signal voltage waveform composed of a first write pulse of T and a first erase pulse before the first write pulse is different from a first scan signal voltage waveform by a pulse width ΔT having a phase shift of ΔT. A second write pulse, and a second scan signal voltage waveform composed of a second erase pulse before the second write pulse. The first and second scan signal voltage waveforms cause The driving method of simultaneously scanning the two scanning signal electrodes and applying the first or second information signal voltage waveform according to the display state to each of the information signal electrodes to reduce power consumption. A high-quality display image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a drive signal waveform used in an image display device according to one embodiment of the present invention.

FIG. 2 is a diagram showing a state of a pixel displayed by a driving signal of FIG. 1;

FIG. 3 is a block diagram of a control system of the image display device according to the embodiment.

FIG. 4 is a diagram showing a drive signal waveform used in an image display device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an application timing of a scan selection signal used in an image display device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing an application timing of a scan selection signal used in an image display device according to a fourth embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between application timing of a scan selection signal and field scanning used in an image display device according to a fifth embodiment of the present invention.

FIG. 8 is a diagram illustrating a relationship between application timing of a scan selection signal and field scanning used in an image display device according to a sixth embodiment of the present invention.

FIG. 9 is a diagram illustrating a relationship between application timing of a scan selection signal used in an image display device according to a seventh embodiment of the present invention and field scanning.

FIG. 10 is a diagram showing a drive signal waveform used in a conventional display device.

[Explanation of symbols]

COM1, COM2: scan selection signal, SEG1 to SEG
4: information signal, 1H: one horizontal scanning time, V1: erase pulse, V2: write pulse, V3: bright information pulse or auxiliary pulse, V4: dark information pulse or auxiliary pulse, V
5: auxiliary pulse, ΔT: pulse width of write pulse, V
C: reference potential, 301: image display unit, 302: scanning signal application circuit, 303: information signal application circuit, 304: scanning signal control circuit, 305: drive control circuit, 306: information signal control circuit, 307: graphic controller.

Continuation of the front page (56) References JP-A-62-175714 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/133 560 G09G 3/36

Claims (11)

(57) [Claims] A liquid crystal panel having a scanning signal electrode, an information signal electrode, and a liquid crystal; an information electrode driving means for applying an information signal voltage waveform to the information signal electrode; and a scan for applying a scanning signal voltage waveform to the scanning signal electrode. In a liquid crystal image display device having an electrode driving unit, the scanning electrode driving unit includes a first scanning signal voltage including a first writing pulse having a pulse width ΔT and a first erasing pulse before the first writing pulse. The second scan signal voltage including a second write pulse having a pulse width ΔT and a second erase pulse before the second write pulse, wherein the waveform and the first scan signal voltage waveform are out of phase by ΔT. Generating a waveform and sequentially selecting two scanning signal electrodes of the liquid crystal panel in the same scanning period according to the first and second scanning signal voltage waveforms, wherein the information electrode driving means has a pulse width ΔT. No. A first information signal voltage waveform including a second information pulse having a polarity opposite to that of the first information pulse and a second information pulse having a pulse width ΔT and a pulse width twice as large as ΔT. And a second information voltage waveform including the third information pulse. 2. The device according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal. 3. A liquid crystal panel having a scanning signal electrode, an information signal electrode, and a liquid crystal, wherein a first writing pulse having a pulse width ΔT is applied to a first scanning electrode of the liquid crystal panel during a first period. A pulse width Δ is applied to a second scan electrode during a second period following the first period.
A second write pulse of T is applied to the information electrode of the liquid crystal panel during the first and second periods, and an information signal is applied to the information electrode of the liquid crystal panel. In a multiplexing driving method for a liquid crystal image display device that determines a display state of a pixel on a scanning electrode, one of four signals is selected as the information signal according to the display state of the pixel, and the information signal is supplied to the information electrode. The four types of signals are different in polarity between the first period and the second period and have different phases from each other, and the first and second voltage waveforms are different from each other in the first period and the second period. A multiplexing driving method, comprising third and fourth voltage waveforms having the same polarity and opposite polarities. 4. The method according to claim 3, wherein the write pulse is applied to another two scan electrodes during a next horizontal scanning period. 5. The method according to claim 3, wherein application of an erase pulse to two other scan electrodes is started during one horizontal scan period. 6. The method according to claim 3, wherein non-adjacent scan electrodes are simultaneously selected during the one horizontal scan period. 7. The method according to claim 3, wherein pairs of scanning electrodes that are not adjacent to each other are sequentially selected in two consecutive horizontal scanning periods. 8. The two pixels selected during one horizontal scanning period
4. The method according to claim 3, wherein an erase pulse is applied to one of the scan electrodes simultaneously. 9. The first and second voltage waveforms each having a polarity opposite to that of the information voltage before the first period and having a shorter pulse width than ΔT or the same pulse width. 9. A pulse according to claim 3, comprising a pulse and a second auxiliary pulse having a polarity opposite to that of the information voltage after the second period and shorter than .DELTA.T or having the same pulse width. the method of. 10. The method according to claim 9, wherein portions of the first and second voltage waveforms corresponding to the first and second auxiliary pulses are reference potentials. 11. The method according to claim 9, wherein the first period and the second period are continuous.