JPH03219288A - Liquid crystal display device and its driving method - Google Patents

Abstract

PURPOSE:To obtain high picture quality by connecting a transfer gate and a reset switch to each column of signal lines by insertion, transferring an image signal which is held by a horizontal sample holding circuit to each unit liquid crystal picture element through a signal line in a specific period of horizontal blanking time and making liquid crystal opaque at other times. CONSTITUTION:A capacity element 2 which holes a video signal temporarily is connected to a terminal Is where the video signal inputted. The transfer gate 3 is interposed between an analog switch 1 and a signal line 4 and the reset switch 8 is connected to the signal line 4. The transfer gate 3 is connected to a driving terminal phiT, the reset switch 8 is connected to a driving terminal phiR, and then the signal line 4 is connected to a terminal VR for applying a potential or pulse voltage which makes liquid crystal on the signal line 4 'opaque'. The signal 4 is applied with a potential or pulse which makes the liquid crystal on the signal line 'opaque' except for the specific period of horizontal blanking period. Consequently, a display irregularity can be eliminated at the border of a picture element display part.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device having a display section with two-dimensionally arranged pixels, and a method for driving the same.

Conventional technology The conventional active matrix type liquid crystal display device is
The pixel portion has a configuration as shown in the cross-sectional view of FIG.

In FIG. 5, glass substrates 2 facing each other with an interval are shown.
On each opposing surface of 1.22, a pixel electrode 23 and a signal line 24 made of, for example, an indium tin oxide film (ITO) are provided on one side, and a common electrode 2 made of, for example, ITO is provided on the other side.
5 is provided, and a black matrix 26 is provided on the surface of the common electrode 25 on the other glass substrate 22 facing the signal line 24. A liquid crystal 27 is filled between the opposing glass substrates 21 and 22. Note that a deflection plate 2 is provided on the outer surface of the glass substrates 21 and 22.
8.29 is installed.

Problems to be Solved by the Invention However, in a conventional active matrix type liquid crystal display device, for example, as shown in FIG. , the B area above and below the A area is affected by leakage light or smear (fake) light (hereinafter simply referred to as leakage light) due to Talostalk, and the black display in the B area is not sufficient for a sufficient black display like the C area. However, there is a problem that the image becomes a neutral gray color.

The reason for this is that when a signal is transferred to the A area, a voltage is applied to the signal line 24 as shown in FIG. Due to the influence of voltage 24, a part of the liquid crystal becomes translucent,
The problem is that leakage light a is generated. Here, we will omit a strict explanation of the polarization of the TN liquid crystal, and if we consider the liquid crystal as a simple light valve switch and express it as "transparent" when a voltage is applied and "non-transparent" when no voltage is applied, the common electrode 25 and the signal 1124 The liquid crystal 27 between the two is transparent as a light valve switch. In addition, when displaying black, the fifth
The pixel electrode 23 shown in the figure is set to the same potential as the common electrode 25 so that the liquid crystal 27 becomes opaque.

The present invention solves the above problems, and aims to provide a liquid crystal display device that does not generate leakage light and a method for driving the same.

Means for Solving the Problems In order to solve the above problems, the liquid crystal display device of the present invention includes:
A transfer gate and a set switch are inserted and connected to the signal line of each column, and when driving this liquid crystal display device, this transfer gate is used to connect an analog switch and a capacitive element during a predetermined period of horizontal blanking time. The image signal held in the horizontal sample and hold circuit consisting of the ), a predetermined potential or pulse is applied to this signal line.

Effect With the above configuration, by applying a potential or a pulse to the signal line such that the liquid crystal on the signal line becomes "non-transparent" except for a predetermined time during the horizontal blanking period, the signal line becomes opaque. The liquid crystal in the vicinity can be made opaque.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a liquid crystal display device according to an embodiment of the present invention. In Figure 1, terminal I inputs a video signal.
A capacitive element 2 for temporarily holding a video signal is connected to s via an analog switch 1. The transfer gate 3 is interposed between the analog switch 1 and the signal line 4. The drive circuit of the display section is connected to the pixel switch 5.
and a pixel capacitor 6, a signal line 4 and a gate signal line 7.
Each of these signal lines 4.7 is cross-connected to each other near the intersection. Reset switch 8 is connected to signal line 4 . The vertical scanning circuit 9 outputs a pulse signal to the gate signal line 7.

A horizontal scanning circuit 10 drives an analog switch 1.

The liquid crystal pixel 20 is connected to the signal line 4 and a common electrode terminal (2) on the opposite substrate surface. Which to drive between. Transfer gate 3 is drive terminal φ
A, the reset switch 8 is connected to the driving terminal φ8, and the signal line 4 is connected to the terminal V for applying a potential or pulse voltage that makes the liquid crystal on the signal line 4 "opaque".
R, respectively. Note that the capacitance value of the capacitive element 2 is set to be sufficiently larger than the distributed capacitance value of the signal line 4.

FIG. 2 is a waveform diagram showing drive pulse timing waveforms of a so-called IH inversion method in which the liquid crystal display device of FIG. 1 is driven by inverting the image signal every horizontal scanning period. In FIG. 2, 1. is the waveform of the IH inversion video signal input from the input terminal Is, and φ8. ．． φ)la+1 is the waveform of each pulse that drives the m-column and m+1-column analog switches 1 created by the horizontal scanning circuit 10, φ7 is the waveform of the pulse applied to the terminal φ7, and φV is the waveform of the pulse created by the vertical scanning circuit 9. The waveform of the pulse that drives the n rows of pixel switches 5, φ
8 represents the waveform of a pulse applied to the terminal φ8 for driving the reset switch 8, respectively.

Next, the operation of this liquid crystal display device will be explained. First, at time t1, analog switches 1 in m columns are turned on by pulse φ1, and the potential of video signal Is at the same time t1 is held in capacitive elements 2 in that column.

Next, at time t2, the pulse φ of the horizontal scanning circuit 10
□, +1 turns on the analog switch 1 in the m+1 column, and similarly, the video signal 1 . The potential of is maintained. Similarly, the potential of the video signal 1 at each time is sequentially held in all the capacitive elements 2 by sequential pulses φH from the horizontal scanning circuit 10.

During the horizontal blanking period within one horizontal scanning period (IH period), for example at time t3, the transfer gate 3 is turned on by the pulse φ7, and the signal line 4 of each column is turned on by capacitance distribution.
The potential becomes the potential of the video signal held in the capacitive element 2 of each column. In order to perform this capacitance distribution as desired, it is necessary to set the capacitance value of the capacitive element 2 to be sufficiently larger than the value of the stray capacitance of the signal line 4.According to experience, the capacitance value of the signal line 4 is At approximately IOF, the capacitance value of the capacitive element 2 is suitably 3 to 10 p[.

Furthermore, at the same time t as the output of the transfer gate driving pulse φ7
3, for example, by applying a pulse φV from the vertical scanning circuit 9 to the gate signal line 7 of the n row, the pixel switch 5 of the n row is turned on, and the potential of the video signal is applied to the pixel capacitor 6 of each pixel. It is transferred from the signal line 4 by capacitance distribution.

At time t4, pulse φ9. Accordingly, pixel switch 5
is turned off, and the potential of the video signal remains (until the next write).
(after one field or frame). At the same time, the transfer gate 3 is also turned off by the pulse φ7, and the signal line 4 and the capacitive element 2 are electrically disconnected.

At time t5, the reset switch 8 is turned on by the pulse φ8, and a voltage or pulse is applied to the terminal VR to all the signal lines 4 so that the liquid crystals on all the signal lines 4 become opaque. For example, when driving a normally black liquid crystal display device, the potential of each signal line 4 is made equal to the potential of the common electrode provided on the surface of the opposing glass substrate. 4 becomes all black as a display, and there is no leakage light near each signal line 4. On the other hand, when driving a normally white liquid crystal display device, each signal line 4 is connected to a reset potential terminal v8. Alternate pulses of about twice the potential of the common electrode, for example, about 12V (P-P), centered around zero potential (Ov), are applied through the electrodes.

As a result, each signal line 4 can be sufficiently "white displayed" and display unevenness at the boundary with the pixel display section can be eliminated.

Furthermore, by repeating the same operation during the next IH period (63 μs), the next video signal can be written into the pixel capacitor 6 of the n+1 row.

At this time, at times other than a specific period in the blanking period of the IH period (that is, the period in which pulse φ1 is active), the signal line 4 has a potential that makes the liquid crystal section on the signal line 4 "opaque". , or apply a pulse that makes the same group "transparent."

FIG. 3 is a schematic cross-sectional view showing a pixel portion of a liquid crystal display device according to an embodiment of the present invention. In FIG. 3, reference numerals 11 and 12 indicate a glass substrate, 13 a pixel electrode, 15 a common electrode, 17 a liquid crystal, and 18.19 a polarizing plate. In FIG. .27, 28, and 29, respectively. However, here:
By applying a voltage that makes the liquid crystal 17 on the signal line 4 completely opaque, the potential of the signal line 4 can be adjusted to eliminate the conventional problem near the signal line 24 as shown in FIG.
This shows a state in which leakage light a is not generated.

Therefore, as shown in FIG. 4, black display (area C)
Even if a white display (area A) is displayed in a part of the area, in areas B above and below area A, the reset switch 8 is turned on by the pulse φ8 that drives the reset switch 8.
Through this, a potential is applied from the terminal 8 to the corresponding signal line 4 so that the liquid crystal 17 on that signal line becomes opaque. At this time, the leakage light is reduced to a duty ratio of pulse φ shown in FIG. 2, that is, approximately 1/1.
It is possible to reduce it to 0 to 1/100.

Therefore, conventionally, in order to suppress this leakage light,
As shown in FIG. 5, a black matrix 26 (light shielding layer) made of, for example, CI-metal was provided on the surface of the common type @25, but in the liquid crystal display device of the present invention, such a black matrix is almost completely absent. Necessary leakage light can be suppressed.

In the embodiments of the present invention, a method for driving a liquid crystal display device using an IH inversion method has been described, but other well-known driving methods for liquid crystal display devices, such as a 1-inversion method or a 1-pixel inversion method, may also be used. Similar actions and effects can be obtained by forming a reset potential pulse corresponding to this.

Effects of the Invention As described above, according to the present invention, leakage light caused by the potential of a signal line can be suppressed, and it is extremely effective in improving the image quality of a liquid crystal display device.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a drive pulse waveform diagram of the liquid crystal display device of the same embodiment, and FIG. 3 is a diagram of the pixel portion of the liquid crystal display device of the same embodiment. FIG. 4 is a schematic cross-sectional view of a display example of a conventional liquid crystal display device, and FIG. 5 is a schematic cross-sectional view of a pixel portion of a conventional liquid crystal display device. 1... Analog switch, 2... Capacitive element, 3...
・Transfer gate, 4... Signal line, 5... Pixel switch, 6... Pixel capacitor, 7... Gate signal line, 8...
Reset switch, 9... Vertical scanning circuit, 10...
Horizontal scanning circuit, φ〒... Transfer gate drive terminal, φR
...Reset switch drive terminal, 7th generation...Reset potential terminal, 13...Pixel electrode, 15...Common electrode, 17...Liquid crystal.

Claims (1)

[Claims] 1. A display section in which liquid crystal pixels are arranged in rows and columns, a vertical scanning circuit, a horizontal scanning circuit, and a signal line that is commonly connected to the liquid crystal pixels of each column and transfers an image signal. , a capacitive element connected to one end of the signal line via a transfer gate, an analog switch that connects the capacitive element to the input terminal of the image signal, and a potential that sets the signal line and the signal line to a predetermined potential. A liquid crystal display device equipped with a reset switch interposed between a supply terminal and a reset switch. 2. A liquid crystal display device having a display section in which liquid crystal pixels are arranged in rows and columns, and a signal line commonly connected to the liquid crystal pixels in each column, during a blanking period of one horizontal scanning period,
The liquid crystal is characterized in that a signal is transferred from the signal line to the liquid crystal pixel line by line, and a predetermined potential that causes the display section to display black is applied to the signal line except at least during the signal transfer period. A method of driving a display device. 3. The liquid crystal display device according to claim 2, wherein the potential of the signal line is made equal to the potential of the common electrode of the display section, except for a predetermined period during which the image signal is transferred to the liquid crystal pixels during a horizontal blanking period. driving method. 4. The liquid crystal according to claim 2, wherein the signal line is driven with a pulse potential that causes the liquid crystal on the signal line to display black, except for a predetermined period during which an image signal is transferred to the liquid crystal pixels during a horizontal blanking period. A method of driving a display device.