JPH02253231A - Liquid crystal display device and its adjusting method - Google Patents

Abstract

PURPOSE:To obtain a high-definition image without after-image and sticking, etc., for a long time by inverting the polarity of picture element voltage every one field or every integer multiple of the field in such a driving system that the polarity of the picture element voltage is inverted every one horizontal scanning period or every integer multiple of the period. CONSTITUTION:A 1st cycle Ff from the 1st generation circuit 47 of a control signal generation circuit 41 which generates the cycle of every one field and a 2nd cycle F1 from the 2nd generation circuit 49 of the control signal generation circuit 41 which generates the cycle of every one horizontal scanning period are inputted in a counter electrode driving means 51 by connecting the circuit 47 and 49 to the driving means 51. Furthermore, a switching circuit 55 for switching the 1st cycle and the 2nd cycle is connected to a switching signal generation means 71. By inverting, driving and adjusting the polarity every one field or every integer multiple of the field in which deviation in adjustment is easy to be detected, the adjustment of a device is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a matrix type liquid crystal display device, and particularly to a liquid crystal display device in which an active element such as a thin film transistor is added to each pixel.

(Prior Art) Matrix type liquid crystal display devices that use nonlinear elements as switching elements, especially active matrix type liquid crystal display devices that use thin film transistors as nonlinear elements, do not perform static drive or static drive even when performing multi-line multiplex drive. It is used in a variety of fields because it can provide equally high-quality images.

Such a liquid crystal display device will be explained with reference to the drawings.

As shown in FIG. 4, this liquid crystal display device has a plurality of scan electrodes X1 (1-1,
2,..., n) and a plurality of signal electrodes Yj (j-1, 2,...,
A matrix wiring section is formed by (2) and a thin film transistor (12) is installed at each intersection.

As shown in FIG. 5, this thin film transistor (12)
The gate electrode (13) is connected to the scan electrode X1, and the drain electrode (
14) is connected to the signal electrode Yj, and the source electrode (1
5) is integrated with the pixel electrode (16) of the liquid crystal display device. A counter electrode (17) common to each pixel is provided on the side facing each pixel electrode (lli), and a liquid crystal (18) is sandwiched between each pixel electrode (16) and the counter electrode (17) to form a pixel. It has become a liquid crystal display device.

The operation of such an active matrix type liquid crystal display device will be explained with reference to FIG.

A clock signal XC1ock that oscillates at time intervals t and a drive voltage vX are input to the scan electrode drive means (21) from the control signal generation circuit. Each scanning line Xi has a gate voltage VGa shifted by a time t from the scanning electrode driving means (21).
tei are input sequentially. For example, at time 11, the scanning line Xi
At time t2, the gate voltage Vgate2 is inputted to the scanning line X2. Then, one field later, the gate voltage V Gatel is again input to the scanning line Xi at layer +1.

A video signal SY whose polarity is inverted every field, a clock signal YC1oek from a control signal generation circuit, and a drive voltage vY are input to the signal electrode drive means (23). The video signal SY is sampled at the timing of the clock signal YC1ock, and for example, the video signal voltage SY1 is input to the signal electrode Y1.

Further, a counter electrode voltage Cv whose polarity is inverted with respect to the center voltage every field is applied to the counter type 1 (17).

For example, regarding the pixel 21.1 formed at the intersection of the scanning electrode XI and the signal electrode yt, the gate voltage V gat
When et is applied to the scan electrode XI, the drain electrode (14) and source electrode (15) of the thin film transistor (12)
conducts. Then, the video signal voltage SY1 that has been applied via the signal electrode Yl is applied to the pixel electrode (1B) via the drain electrode (14) and source electrode (15).

At this time, since the counter electrode voltage Cv is applied to the counter electrode (17), the video signal voltage SYl and the counter electrode voltage C
V, that is, the pixel voltage ZV1. l is liquid crystal (1B)
is applied to This pixel voltage ZVI,l causes the liquid crystal (1
8) changes to produce an optical difference. This pixel voltage ZVI,1 is again the gate voltage V gatel
This voltage is maintained until -+1 for the time that is applied to the scan electrode Xi.

Similarly, for the pixel 22.1, the pixel voltage ZV2. l is applied and holds this voltage until the amount iJ divided by 2.

In the liquid crystal display device as described above, the pixel voltage ZV1. applied to each pixel every field. Since the polarity of the counter electrode voltage Cv or video signal voltage SYj is inverted so that the polarity of
deterioration can be prevented.

However, in this way, the pixel voltage ZV1. applied to the liquid crystal (18) every field. When the polarity of j is reversed, the following problem occurs.

Since there is a parasitic capacitance CGS between the gate electrode (13) and pixel electrode (16) of each thin film transistor (12), for example, the literature (Pro, Japan Display)
'83. As shown in P412-414), a level shift voltage Vp is generated between the video signal voltage SYj and the pixel voltage ZVi,j when the gate voltage V Gatel is at the off level.

This can be expressed by the following formula.

Vp=VGate1. xCgs/ (C1c+Cgs
) Here, V Gatel is the gate voltage, and C1c is the liquid crystal capacitance.

Such level shift voltage Vp is equal to pixel voltage ZV1. during positive polarity driving. During negative polarity driving, the pixel voltage ZVI,j increases so that j decreases.

Therefore, the pixel voltage ZV during positive polarity driving and negative polarity driving
i and j must be adjusted in advance to provide a level difference by the level shift voltage Vp. This level shift voltage V
If the adjustment of p is not appropriate, an imbalance will occur between the positive and negative polarities of the liquid crystal, and a DC component will be applied to the liquid crystal (18).
Not only does the quality of the image deteriorate, but the unbalanced optical response appears as flicker to the human eye.

(Problem to be Solved by the Invention) As a solution to such a problem, for example, as shown in FIG. 7, the pixel voltage ZV! , j was considered to be driven by inverting the polarity of the counter electrode voltage C■ or the video signal voltage SYj.

When a liquid crystal display device is driven in this way, the counter electrode voltage C
level shift voltage V between v or video signal voltage SYj
Even if p is not properly adjusted and an optical imbalance occurs, the optical imbalance between adjacent scanning electrodes will not appear as flicker to the human eye.

However, since it is difficult for the human eye to recognize adjustment deviations, a DC component is applied to each pixel, which may cause afterimages and the like.

Further, if the adjustment deviation of the level shift Vp is large, it is necessary to perform the adjustment by introducing a new optical measuring instrument, which poses a problem that the process becomes much more complicated than the conventional adjustment by visual inspection.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a liquid crystal display device that can be easily adjusted without using an optical measuring device and that can provide good display over a long period of time, and a method for adjusting the same. Our goal is to provide the following.

[Structure of the Invention] (Means for Solving the Problems) The liquid crystal display device of the present invention includes a matrix wiring including a plurality of seven scanning electrodes and a plurality of signal electrodes, and a switching element arranged at the intersection of the matrix wiring. , a pixel electrode connected to the matrix wiring through the switching element, a counter electrode facing the pixel electrode, and a liquid crystal sandwiched between the pixel electrode and the counter electrode, and a voltage applied between the pixel electrode and the counter electrode. a first means for inverting the polarity of the pixel voltage applied to each field or an integer multiple thereof; a second means for inverting the polarity of the pixel voltage for each horizontal scanning period or an integer multiple thereof; 1
The present invention is characterized by comprising a switching means for selecting the first means and the second means.

Further, the method for adjusting a liquid crystal display device of the present invention includes a matrix wiring including a plurality of scanning electrodes and a plurality of signal electrodes, a switching element arranged at an intersection of the matrix wiring, and a connection to the matrix wiring through the switching element. a pixel electrode, a counter electrode facing the pixel electrode, and a liquid crystal sandwiched between the pixel electrode and the counter electrode,
A first means for inverting the polarity of the pixel voltage applied to the pixel electrode and the counter electrode every one field or an integer multiple field thereof; and inverting the polarity of the pixel voltage every one horizontal scanning period or an integer multiple thereof. A method for adjusting a liquid crystal display device comprising a second means, wherein the first means sets the polarity of the pixel voltage to a first state in which it is inverted every field or every integral multiple thereof; The pixel voltage is adjusted, and the polarity of the pixel voltage is set to a second state in which the polarity of the pixel voltage is inverted every horizontal scanning period or an integral multiple of the horizontal scanning period using the second means.

(Function) Therefore, in the present invention, an image is displayed by first inverting the polarity of the pixel voltage applied to each pixel every field or every field that is a positive multiple of this.

At this time, the level shift voltage Vp generated by the parasitic capacitance cgs
If the adjustment is not done correctly, flicker will be visible to the naked eye.

Therefore, for example, in order to minimize flicker, the counter electrode voltage or the signal electrode voltage is adjusted to the level shift voltage Vp.
Then, while maintaining this potential relationship, the polarity of the pixel voltage applied to each pixel is inverted every horizontal scanning period or every horizontal scanning period that is a positive multiple of this, and the image is displayed. Let's do it.

In this way, even if the polarity of the pixel voltage is inverted every horizontal scanning period or every positive multiple thereof, it is a drive that inverts the polarity of the pixel voltage every field or every positive multiple of this period, for example. By adjusting the level shift voltage Vp by visually observing flicker, the level shift voltage Vp can be easily controlled without introducing a new measuring device.

(Example) Hereinafter, as an example of the liquid crystal display device of the present invention, a liquid crystal display device that displays television images will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of the liquid crystal display device of this embodiment, which includes a liquid crystal panel (11) for displaying an image, a scanning electrode driving means (21) for driving this liquid crystal panel (11), and a signal electrode driving means. means (23), counter electrode driving means (51), and a control signal generation circuit (41) for controlling these driving means
, a video signal control circuit (31) that controls video signals input from the outside, and two types of signals that are connected to the counter electrode drive means (51) and the video signal control circuit (31) and input from the control signal generation circuit. The switching signal generating circuit (71) operates a switch circuit (not shown) provided in the counter electrode driving means (51) and the video signal control circuit (31) in order to select the signal.

Further, to explain this embodiment in detail, as shown in FIG. 4, the liquid crystal panel (11) has a plurality of scanning electrodes XI (1-1,
2, -, m) and a plurality of signal electrodes Yj (j-1, 2,
, n) constitute a matrix wiring, and a thin film transistor (12) is installed at each intersection.

As shown in FIG. 5, the scanning electrode Xi is connected to the gate electrode (13) of the thin film transistor (12), and the signal electrode Yj
is connected to the drain electrode (14), and further connected to the source electrode (
15) is connected to the pixel electrode (16). A liquid crystal panel (11) is constructed by sandwiching a liquid crystal (18) between each pixel electrode (1B) and a counter electrode (17) that commonly faces the pixel electrodes (16).

In this liquid crystal panel (11), in order to drive each pixel, a scan electrode drive means (21) is connected to the scan electrode XI, and a signal electrode drive means (23) is connected to Yj.

This scan electrode drive means (21) receives a drive voltage vX and a clock signal X from a scan electrode drive means control circuit (43).
C1ock is connected to the signal electrode drive means (23) so that the drive voltage VY and clock signal YC1ock from the signal electrode drive means control circuit (45) are input.

Further, the signal electrode driving means (23) is connected to receive a video signal SY from a video signal control circuit (31).

Also, the counter electrode voltage CV from the counter electrode drive means (51)
is connected to be input to the counter electrode (17) of the liquid crystal panel (11). This counter electrode driving means (51
) includes a first period Ff from a first generation circuit (47) of a control signal generation circuit (41) that generates a period for each field, and a control signal generation circuit that generates a period for each horizontal scanning period. the second from the second generating circuit (49) of the circuit (41).
A switch circuit (55) is connected to input the period Fl of
) (see FIG. 2) is connected to a switching signal generating means (71).

In this embodiment, one field period refers to the liquid crystal panel (11).
One horizontal scanning period is a period in which all pixels of one scanning electrode are displayed.

Alternatively, one field period may be a period in which all pixels of even or odd scan electrodes are displayed.

Next, referring to FIG. 2, this counter electrode driving means (51)
details.

The first period Ff and the second period from the first generation circuit (47) and second generation circuit (49) of the control signal generation circuit (41)
A first period input terminal (52) and a second period input terminal (53) to which the period F1 of is input are formed, and are connected to a switch circuit (55). This switch circuit (55)
constitutes a switching means in which the first period Ff and the second period Fl can be selected by inputting a switching signal from a switching signal generation circuit (71) via a switching terminal (70).

The first cycle Ff and second cycle Fl selected by the switch circuit (55) are transmitted to the video signal control circuit (31) via the transmission terminal (56), and the other is transmitted to the transistor (
57). The emitter of this transistor (57) is connected to a resistor R2 (59), and the collector is connected to a resistor R1 (58) connected to a drive power supply (58).
The amplification can be adjusted by adjusting the first adjustment knob (eo).

This amplified output is added via a capacitor C1 (67) to the output voltage of a voltage divider circuit consisting of a resistor R3 (62) and a resistor R4 (E13) connected in series to this resistor R3 (62). be done. Then, by the second adjustment knob (67) that can adjust the voltage division ratio of the resistor R3 (55),
The added voltage can be adjusted.

Further, the differential amplifier (65) is connected to be inputted to the counter electrode (17) via the output terminal (6B).

The operation and adjustment method of such a liquid crystal display device are shown in FIG.
This will be explained with reference to FIG.

The first period Ff', which is reversed every frame period, is generated by the counter electrode driving means (51) and the video signal control circuit (31).
), the switching signal generation circuit (71)
switch circuit (55) via the switching terminal (70) at
is driven to select the first period generating circuit (47).

A predetermined voltage is added to this first period Ff by the counter electrode driving means (51), and the counter electrode (51) is amplified.
17) as a counter electrode voltage CV.

Further, this first period Ff' is the same as the counter electrode driving means (5
The video signal control circuit (3) is connected to the video signal control circuit (3) via the transmission terminal (56) of (1).
1), and the video signal control circuit (
31) is output as a video signal SY whose polarity is inverted in the first period Ff.

The scanning electrode driving means (21) includes a scanning electrode driving means control circuit (41) as shown in FIG.
43) A clock signal X C that oscillates at a time interval t from
1ock and drive voltage vX are input. Further, the signal electrode driving means (23) receives the video signal SY that is inverted at the first period Ff from the video signal control circuit (31), and the clock signal YCIock and drive voltage VY from the control signal generation circuit (41). be done.

First, at time 11, the gate voltage v gatei is manually applied to the scan electrode X1, and each gate electrode (
13), the drain voltage t5! of the thin film transistor (12) increases. (14) and the source electrode (15) are electrically connected.

At this time, the video signal SY inverts at the first period Ff sampled at the timing of the clock signal YC1ock.
becomes the video signal voltage SYj for each signal electrode Yj, and is inputted to the signal electrode Yj in parallel. For example, signal electrode Y
1, the video signal voltage SY1 is input.

For example, in pixel 21.1, the drain electrode (14) and source electrode (15) are electrically connected, so this video signal voltage SYI is input to the pixel electrode (16).

Then, the aforementioned counter electrode voltage CV is applied to the counter electrode driving means (5).
1) to the counter electrode (17), the potential difference between the video signal voltage SYI and the counter electrode voltage CV, that is, the pixel voltage ZVI, 1 is applied to the pixel 21.1. This pixel voltage ZV1.1 changes the liquid crystal (18) to produce an optical difference. The pixel voltage zvi,i is then held until time tn++1 when the next pixel 21.1 is selected.

Then, the time t m+1 when the next pixel Z 1,1 is selected
Then, the pixel voltage ZVI,1 applied to the pixel Z1,1
The polarity of is reversed and applied.

Similarly, to the adjacent pixel Z2,1, a pixel voltage ZV2,1 of the same polarity as that of the pixel Z1,1 is applied to the pixel Z2,1 at time t2, delayed from time tl, and at the next selected time t. (2) This pixel voltage ZV2,1 potential is held until +2.

If the counter electrode voltage Cv is poorly adjusted in such a state, it can be visually confirmed that a difference in brightness occurs every first period Ff.

In this state, by adjusting the second adjustment knob <84) to adjust the voltage added to the counter electrode voltage Cv, the level shift voltage Vp is adjusted and the flicker is eliminated.

By adjusting the first adjustment knob (80),
The brightness is adjusted by adjusting the amplitude of the counter electrode voltage Cv and controlling the amount of transmitted light passing through the liquid crystal panel (11).

After the occurrence of flicker is minimized in this way, the switching signal generating circuit (71) causes the switching circuit (
55) to connect the second period generating circuit (49), the video signal control circuit (81), and the counter electrode driving means (51). A second period Fl from a second period generation circuit (49) is input.

The second period Fl from the second period generation circuit (49) is
This is a signal that is inverted every horizontal scanning period, and as shown in FIG. 7, the video signal control circuit (
The video signal SY output from the counter 31) and the counter electrode voltage Cv output from the counter electrode drive means (51) are signals whose polarities are inverted every second period Fl.

Therefore, to explain the adjacent pixels 21.1 and 22.1 of the liquid crystal panel <11) as an example, in the above-mentioned driving that inverts every frame, the adjacent pixels 21.1 and 22.1 have the same Polarity pixel voltage ZV1.1 and pixel ZV2
．． 1 was applied, but here, pixel voltages Z, , V1 . l and pixel ZV2,1 are applied. Therefore, driving in which the polarity is reversed every second period Fl provides a better display image than driving in which the polarity is reversed every first period Ff.

When a liquid crystal display device is used in such a state, display without flickering or afterimages is possible.

As described in detail above, in the liquid crystal display device of this embodiment, even if the polarity of the voltage applied to the pixel is reversed every horizontal scanning period, it is easy to do so by visual inspection without the need for an optical adjustment device. The LCD display device can be adjusted to

Therefore, adjustment of the liquid crystal display device can be performed very easily, leading to improved productivity.

The counter electrode driving means of this embodiment is just one example, and various other circuit configurations are possible. Here, the flicker of the liquid crystal display device was suppressed by adjusting the center voltage of the counter electrode voltage Cv, but this may also be done by adjusting the video signal SY.

Further, an inverter may be provided inside the signal electrode driving means (23) to invert the polarity of the video signal SY.

[Effects of the Invention] As described above, according to the present invention, even in a liquid crystal display device that is driven by inverting the polarity of the pixel voltage every horizontal scanning period or every integer multiple thereof, misalignment in adjustment can be detected. By driving and adjusting by inverting every field or an integral multiple thereof, the adjustment can be made easier than in the past. Furthermore, by using such a liquid crystal display device, it is possible to obtain high-quality images without afterimages, burn-in, etc. over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention;
FIG. 2 is a schematic circuit diagram of the counter electrode driving means of this embodiment, and FIG. 3 is a waveform diagram 1 showing the waveforms of the first period and the second period.
, FIG. 4 is a schematic configuration diagram of a liquid crystal panel of a liquid crystal display device, FIG. 5 is an enlarged view of a thin film transistor portion of this liquid crystal panel, and FIGS. 6 and 7 are diagrams showing driving waveforms of the liquid crystal display device. (11)...Liquid crystal panel (12)...Thin film transistor (13)...Gate electrode (14)...Drain electrode (I5)...Source electrode (16)...Pixel electrode (17) ...Counter electrode (18) ...Liquid crystal (21) ...Scanning electrode drive means (23) ...Signal electrode drive means (31) ...Video signal control circuit (41) ...Control signal Generating circuit (51)...Representative of counter electrode driving means Patent attorney Noriyuki Chika Yudo Kikuo Takehana Figure V Figure 5

Claims (2)

[Claims] (1) A matrix wiring consisting of a plurality of scanning electrodes and a plurality of signal electrodes, a switching element arranged at the intersection of this matrix wiring, a pixel electrode connected to the matrix wiring via this switching element, and this pixel comprising a counter electrode facing the electrode, and a liquid crystal sandwiched between the pixel electrode and the counter electrode, and the polarity of the pixel voltage applied between the pixel electrode and the counter electrode is controlled every field or every integral multiple thereof. a first means for inverting the polarity of the pixel voltage; a second means for inverting the polarity of the pixel voltage every horizontal scanning period or an integral multiple thereof; and switching for selecting the first means and the second means. A liquid crystal display device comprising: means. (2) A matrix wiring consisting of a plurality of scanning electrodes and a plurality of signal electrodes, a switching element arranged at the intersection of this matrix wiring, a pixel electrode connected to the matrix wiring via this switching element, and this pixel a counter electrode facing the electrode, a liquid crystal sandwiched between the pixel electrode and the counter electrode, and a step that inverts the polarity of the pixel voltage applied to the pixel electrode and the counter electrode every one field or every integral multiple thereof. In the method for adjusting a liquid crystal display device, the method includes the first means and a second means for inverting the polarity of the pixel voltage every one horizontal scanning period or an integral multiple thereof, wherein the pixel voltage is adjusted by the first means. a first state in which the polarity of the pixel voltage is inverted every one field or every integer multiple field thereof, the pixel voltage is adjusted in the first state, and the second means causes the polarity of the pixel voltage to be inverted for one horizontal scanning period or The second inverts every integer horizontal scanning period.
A method for adjusting a liquid crystal display device, characterized by: