JPS63286821A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To uniformize the luminance on both surfaces, by respectively providing an upper and lower electrodes on the upper and lower ends of counter electrodes and respectively applying an AC voltage of a prescribed amplitude and a prescribed DC voltage across one end and the other end of the counter electrodes. CONSTITUTION:Since an upper electrode 72 is connected with a connecting point P1, a voltage of 0Vp-p is always applied across the electrode 72 and, since a lower electrode 73 is connected with a connecting point P2 at the time of an odd field and another connecting point P3 at the time of an even field, a voltage of 4Vp-p in amplitude is applied across the electrode 73. Therefore, the voltage is divided in a transparent electrode 71 by means of equivalent resistances in a column direction and a voltage gradient is produced in the electrode 71 and, as a result, voltage waveforms of different amplitudes are applied across at every row. Therefore, even when the potential across the counter electrodes fluctuates while the voltage waveform impressed upon a liquid crystal cell 1 is maintained, the mean values of the effective values of voltages VP1, VP2,...VPN applied across the liquid crystal cell 1 of each row become almost equal to each other in the column direction and the luminance at the lower sections of both surfaces is not reduced, since the amplitude of the counter electrodes is made larger as going to lower rows. Therefore, the luminance on both surfaces becomes uniform.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a liquid crystal display device such as a liquid crystal TV device.

- Conventional technology Conventionally, as a method for driving an active matrix type liquid crystal panel, for example, Japanese Patent Publication No. 61-34612 () (
There is a method in which the video signal and the common electrode potential are inverted for each field, as described in U.S. Patent No. 4NS/66).

The method will be explained in detail below.

Figure 4 shows an IJ type liquid crystal display device, (1)
(2) is an FET connected to one electrode of each liquid crystal cell (1), (31 is an FET (2) for each column of the matrix)
(4) is a plurality of Y electrodes commonly connected to the gates of FETs (21) for each row of the IJ. Also, (5) is a Y electrode (
4) is a Y driver that sequentially applies set meal pulses; (6) is a video signal that is sampled and held to convert one line of video signals into parallel video signals of X number of electrodes, and is applied to X electrodes (3). This is an X driver. (7) is a counter electrode commonly connected to the other electrode of all liquid crystal cells (1).

Next, the operation of the liquid crystal display device will be explained with reference to FIG.

In Fig. 5, VD is the video number 18 whose polarity is inverted every field, VGI, VO2...VGll are the gate signals applied to the Y electrodes (4) (4)... of each row,
VPl, VF6...VPN are the liquid crystal cells (1
) is the voltage maintained by The FET (21) is turned on during the high period of the gate signal, and at this time, the voltage of the sampled video signal is applied to the liquid crystal cell (1), and after the FET (2) is turned off, it is held for one field period. be done.

However, in the first row, the timing of the gate signal and the switching timing of the counter electrode are synchronized, but in the second and subsequent rows, the two timings do not match, and the potential of the counter electrode changes while the voltage is held, so that CVP2 ．． V.P.
N) There is a drawback that the effective value of the voltage applied to the liquid crystal cell (1) decreases, and the brightness at the lower part of 15WJ decreases.

el Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned points, and an object of the present invention is to equalize the brightness on the screen.

B) Means for Solving the Problems The present invention provides an upper electrode at the upper end of the opposing electrode and a lower electrode at the lower end, and applies an AC voltage of a predetermined amplitude to one and a predetermined DC voltage to the other. Become.

(e) Effect: Since a voltage gradient is generated in the column direction of the counter electrode by the above-described means, the effective value of the voltage applied to the liquid crystal cell does not substantially change in the column direction.

(f) Example Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a counter electrode in this example.

The counter electrode (to) that is neglected in this embodiment is an IT electrode with relatively high resistance.
It consists of a transparent electrode (2) made of a transparent electrode (2), an upper electrode (2) made of Au-Cr and a lower electrode (2) formed on the upper and lower ends of the transparent electrode outside the effective display range, respectively.

The upper electrode surface and the lower electrode (to) are respectively connected to a voltage setting circuit (8) to be described later.

Next, FIG. 2 is a circuit diagram of a liquid crystal display device using the counter electrode shown in FIG. 1, and the same parts as in FIG. 4 are given the same reference numerals, and the explanation thereof will be omitted.

As described above, the upper electrode □□□ and the lower electrode ▪ of the counter electrode in this embodiment are connected to the voltage setting circuit (8). This voltage setting circuit consists of resistors (R1) to (R5)
The analog switch (S1) (S2) is controlled by a switching signal that is inverted for each field or its inverted signal, and an inverter (INV) that inverts the switching signal.

The voltage divider (8a) has a terminal (VH) connected to +5 V, a terminal (VL) connected to -5 V, and resistors (R1) to
The voltages at each connection point (PIXP2XP3) between (R5) are set to V, -1-2V, and -2V, respectively.Next, the operation of the device of this embodiment will be explained with reference to FIG. .

The switching signal is, for example, high in an odd field and low in an even field; the analog switch (Sl) is turned on in an odd field, and the analog switch (S2) is turned on in an even field.

Since the upper electrode surface is connected to the connection point (Pl), the amplitude is always OV pp, but the lower electrode surface is connected to the connection point (R2) during the operative number field, and at the even number field.
Since the connection points (R3) are connected to each other, a voltage with an amplitude of 4Vp-p is applied. That is, since different voltages are applied to the upper electrode (2) and the lower electrode (2) provided at both ends of the transparent electrode (2), which is represented by the equivalent resistance 1rl, the transparent electrode (2) has an equivalent resistance of 1rl in the column direction. The voltage is divided to create a voltage gradient, and each row has a different amplitude, for example, oVp-p (VTl) in the first row, and GCgi 0.2 in the second row.
Vp-p (VT2), Nth row kcc4. OVp
-p (VT!1) (7) An amplitude chisel pressure waveform is applied.

Therefore, even if the potential of the counter electrode changes while the voltage waveform applied to the liquid crystal cell (1) is maintained, the amplitude of the counter electrode is made larger as the number of rows increases. , the voltage (VP
1, VP2...VPII) are almost the same in the column direction, and no reduction in brightness occurs at the bottom of the screen.

In the above embodiment, the voltage of the upper electrode is set to Ov, but depending on the video signal and the set value of the voltage applied to the f section electrode, the voltage of the upper electrode may be set to another predetermined DC voltage value. You can also do it.

(G) Effects of the Invention As described above, according to the present invention, there is no low brightness at the F part of the screen, and the brightness on the screen is uniform, so it is possible to realize a high-quality LCD television monitor device. .

Furthermore, in order to generate a voltage gradient in the column direction of the opposing electrodes, the configuration is such that AC voltage is applied to one electrode while DC voltage is applied to the other electrode, which simplifies the voltage setting circuit.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a counter electrode in an embodiment of the present invention, FIG. 2 is a circuit diagram of the device of this embodiment, FIG. 3 is a waveform diagram thereof, and FIG. 4 is a circuit of a conventional liquid crystal display device. FIG. 5 is a waveform diagram thereof. (1)...Liquid crystal cell, (2)...FET, (31.
...X[8i, (41...Y electrode, (to)...Counter electrode, (2)...Transparent electrode, (2)...Upper electrode,
關...upper electrode, (8)...voltage setting circuit. Yamato Sanyo Electric Co., Ltd. agent Patent attorney Takuji Nishino (removed) Figure 1 Figure 3 VTI
QFigure 4Figure 5

Claims (1)

[Claims] (1) Liquid crystal cells arranged in a matrix, a field effect transistor provided for each liquid crystal cell and connected to one electrode of each liquid crystal cell, and an input electrode of the field effect transistor for each column of the matrix. a plurality of X electrodes that are commonly connected to and to which a video signal that is inverted at a predetermined period is applied;
Each row of the matrix has a plurality of Y electrodes that are commonly connected to the gates of the field effect transistors, and a counter electrode that is connected to the other electrode of the liquid crystal cell and to which a voltage that changes at the predetermined period is applied. In the liquid crystal display device, an upper electrode is provided at the upper end of the directional electrode, and a lower electrode is provided at the lower end, and an alternating current voltage of a predetermined amplitude is applied to one of the electrodes, and a predetermined direct current voltage is applied to the other electrode. A liquid crystal display device.