JP3744203B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly, to a structure of a liquid crystal element used therein.
[0002]
[Background]
In recent years, liquid crystal elements have been widely used as electronic devices such as televisions, electronic notebooks, personal computers, and mobile phones, particularly as display devices, as low power consumption and lightweight display devices. A two-terminal active matrix liquid crystal element using a non-linear resistance element such as an MIM element, a back-to-back diode element, a diode ring element, or a varistor element as a switching element, or a three-terminal type using a thin film transistor as a switching element. Active matrix liquid crystal devices are attracting attention due to their high performance (high contrast, high speed response). In particular, the two-terminal active matrix liquid crystal device provides a liquid crystal device at a low manufacturing cost because of its simple switch element structure. It is possible.
[0003]
Here, in the two-terminal active matrix liquid crystal element, a plurality of scanning electrodes are formed on one of a pair of substrates sandwiching a liquid crystal layer, and a plurality of signal electrodes are planar with the electrodes of the scanning electrodes on the other substrate. The non-linear resistance element and the pixel electrode are formed at each portion where the scanning electrode and the signal electrode intersect in a plane.
[0004]
Then, scanning electrodes are sequentially selected for a predetermined selection period to give a selection voltage, and in synchronization with this, driving is performed to give each signal electrode a signal voltage that is voltage-modulated according to the display pattern.
[0005]
[Problems to be solved by the invention]
By the way, in these active matrix liquid crystal elements, undesired display unevenness occurs.
[0006]
For example, the display unevenness that occurs in the vertical direction when a vertical bar is displayed (hereinafter referred to as vertical crosstalk) is an example of a two-terminal active matrix liquid crystal device in Journal of the SID, 2/2, 1994 p75-80. Therefore, explanations and countermeasures for the generation mechanism are proposed. According to this, since there exists a pixel capacitance (hereinafter referred to as Cp) formed by the signal electrode and the pixel electrode facing the signal electrode and a parasitic capacitance (hereinafter referred to as Cs) of the nonlinear element, it is applied to the signal electrode. When the voltage changes by ΔV, the voltage applied to the pixel capacitance (hereinafter referred to as pixel voltage) changes by ΔV · Cs / (Cs + Cp). Therefore, if the voltage waveform applied to each signal electrode differs according to the display pattern, the pixel voltage, and hence the effective voltage, will be different, causing vertical crosstalk. A method is proposed in which longitudinal crosstalk is reduced by applying a voltage-modulated signal voltage in a part of each selection period and applying the center voltage of the signal voltage to all signal electrodes in the remaining period. .
[0007]
However, these measures alone have not completely eliminated the vertical crosstalk.
[0008]
Therefore, as a result of intensive research and investigation by the present inventor, it was found that the following cause is one of the causes of the occurrence of vertical crosstalk.
[0009]
FIG. 4 is a schematic diagram showing the structure of a conventional two-terminal active matrix liquid crystal element.
[0010]
In FIG. 4, 11 is a two-terminal active matrix liquid crystal element, 1 and 2 are a pair of substrates sandwiching a liquid crystal layer (not shown), Y1 to Y5 are a plurality of scanning electrodes provided on the substrate 1, X1 ˜X5 are signal electrodes provided on the substrate 2.
[0011]
S is a non-linear resistance element, which is represented by a symbol representative of only one place in the figure, but is provided on the substrate 1 so as to be connected to the scan electrodes Y1 to Y5. As the non-linear resistance element S, an MIM element in which a thin insulating film is formed between metals is used here, but other elements having bidirectional diode characteristics may be used.
[0012]
P is a pixel electrode, which is represented by a symbol representatively in only one place in the figure, but is provided on the substrate 1 via a non-linear resistance element S with respect to the scanning electrodes Y1 to Y5.
[0013]
Here, the number of scanning electrodes Y1 to Y5 and the number of signal electrodes X1 to X5 is as small as five, but this is for the sake of simplifying the drawing and description, and in actual liquid crystal panels, each is usually composed of several hundreds or more. .
[0014]
FIG. 5 is a diagram showing an electrical equivalent circuit relating to a certain scanning electrode (represented by Y1 here) of the liquid crystal element 11 of FIG. 4, and Cp is a pixel electrode P facing each of the signal electrodes X1 to X5. The liquid crystal layer is a dielectric in the pixel capacitance formed by the portion. Cs is a capacitance parasitic to the nonlinear resistance element S. Cpp is a capacitance between the pixel electrodes. In the figure, the pixel capacitance Cp, the parasitic capacitance Cs, and the inter-pixel capacitance Cpp are representatively given only at one place.
[0015]
Of course, the size of each capacitor depends on the size of each part of the liquid crystal element 11. For example, in a certain liquid crystal element, Cp = 75 fF, Cs = 20 to 40 fF, and Cpp = 6 to 10 fF. That is, the inter-pixel capacitance Cpp is about 10% of the pixel capacitance Cp.
[0016]
Here, when the voltage applied to a certain signal electrode changes by ΔV, the voltage of the pixel electrode facing this changes by ΔV · Cp / (Cs + Cp + 2 · Cpp).
[0017]
Further, the voltage of the adjacent pixel electrode changes by ΔV · Cp · Cpp / {(Cs + Cp) (Cs + Cp + 3 · Cpp)} due to the voltage change of the pixel electrode.
[0018]
Substituting the previous specific numerical value into this results in about 0.05 · ΔV. Therefore, considering that the voltage change ΔV of the signal electrode is several volts, a voltage change of about 100 mV occurs in the adjacent pixel electrode, in other words, the pixel voltage created by this pixel electrode, and the vertical crosstalk It will cause to generate.
[0019]
The present invention has been made in view of the above problems, and an object thereof is to provide a liquid crystal element that performs display without vertical crosstalk.
[0020]
[Means for Solving the Problems]
The liquid crystal display device according to the present invention includes a pair of substrates sandwiching a liquid crystal layer, a plurality of first electrodes formed on one of the substrates, and a plurality of second electrodes formed on the other substrate. Is formed so as to intersect the plurality of first electrodes in a plane, and a plurality of nonlinear resistance elements are connected to each of the second electrodes, and are connected to the second electrodes via the nonlinear elements. In the liquid crystal display device in which a plurality of pixel electrodes are formed, the liquid crystal display device is disposed on the other substrate in a gap between the adjacent pixel electrodes so as not to overlap with the pixel electrodes, and in plan view with the second electrode. A plurality of third electrodes intersecting each other are formed, the plurality of third electrodes are connected to each other, and the adjacent pixel electrodes are electrostatically shielded.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
[First Embodiment]
1 is a diagram showing a first embodiment of a liquid crystal element of the present invention, FIG. 2 is a diagram showing a configuration of a substrate 1 constituting the liquid crystal element 10 of FIG. 1, and FIG. 3 is a diagram of the liquid crystal element 10 of FIG. It is a figure which shows the electrical equivalent circuit regarding a scanning electrode.
[0023]
In FIG. 1, 10 is a two-terminal active matrix liquid crystal element, 1 and 2 are a pair of substrates sandwiching a liquid crystal layer (not shown), Y1 to Y5 are a plurality of electrodes provided on the substrate 1, X1 ˜X5 are electrodes provided on the substrate 2. Z1 to Z4 are electrodes provided on the substrate 1 and formed between the pixel electrodes P.
[0024]
S is a non-linear resistance element, and a symbol is given representatively in only one place in the figure, but it is provided on the substrate 1 so as to be connected to the electrodes Y1 to Y5. As the nonlinear resistance element S, an MIM element in which a thin insulating film is formed between metals is used in the present embodiment, but any element having bidirectional diode characteristics may be used. P is a pixel electrode, and in the figure, only one place is represented by a symbol, but is provided connected to electrodes Y1 to Y5 via a non-linear resistance element S.
[0025]
Here, the number of electrodes Y1 to Y5 and the number of electrodes X1 to X5 and Z1 to Z4 is as few as 4 to 5, but this is for the sake of simplifying the drawings and explanations. It is configured.
[0026]
In such a liquid crystal element, a selection voltage for sequentially selecting the electrodes Y1 to Y5 for a predetermined selection period is supplied from a drive circuit (not shown), and a signal voltage that is voltage-modulated according to a display pattern in synchronization with the selection voltage. Is supplied to each of the electrodes X1 to X5.
[0027]
FIG. 2 is a diagram showing only the configuration of the substrate 1 of FIG. 1 for the sake of easy understanding.
[0028]
Here, the shapes of the electrodes Z1 to Z4 are formed so as to enter between the pixel electrodes P. In other words, the electrodes Z1 to Z4 are necessarily formed between the pixel electrodes P. The electrodes Y1 to Y5 and the electrodes Z1 to Z4 are insulated, and the electrodes Z1 to Z4 are all conductive at least at one place, and in FIGS.
[0029]
With the above configuration, as shown in FIG. 3, the electrical equivalent circuit relating to a certain scan electrode (here represented by Y1) of the liquid crystal element 10 of FIG. 5 is formed with a pixel capacitor Cp having a liquid crystal layer as a dielectric, and Cs due to the parasitic capacitance of the nonlinear resistance element S is formed. A capacitance is also formed between the electrodes Z1 to Z4 and the pixel electrode P, and this is represented as Cpc, and this is represented by one symbol as representative of the figure.
[0030]
The presence of the capacitance Cpc shown in the equivalent circuit can reduce the degree of voltage change that a voltage change of a certain pixel electrode gives to an adjacent pixel electrode. In other words, the electrodes Z1 to Z4 function as electrostatic shields. Accordingly, the voltage change of the adjacent pixel electrode, and hence the effective voltage change of the pixel capacitance formed by the adjacent pixel electrode is reduced. Therefore, the vertical crosstalk can be remarkably reduced.
[0031]
Although FIG. 1 shows a case where there is a gap between the electrodes Z1 to Z4 and the pixel, this gap is not necessary. For example, the electrodes Z1 to Z4 may be overlapped if they are insulated.
[0032]
Moreover, it can prevent that a liquid crystal element becomes dark by forming with a transparent conductive member, such as an indium oxide and a tin oxide, as a member of the electrodes Z1-Z4.
[0033]
1 and 2 show the case where the electrodes Z1 to Z4 are formed on the electrodes Y1 to Y5, they may be formed below the electrodes Y1 to Y5.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of a liquid crystal element constituting a liquid crystal display device of the present invention.
FIG. 2 is a diagram showing a configuration of a substrate 1 in the first embodiment of the present invention.
3 is a diagram showing an electrical equivalent circuit of the liquid crystal element 10 of FIG. 1. FIG.
FIG. 4 is a diagram illustrating a configuration example of a liquid crystal element of a conventional technique.
FIG. 5 is a diagram showing an electrical equivalent circuit of a liquid crystal element according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Substrate 10 ... Liquid crystal element X1-X5 ... Electrodes Y1-Y5 on substrate 2 ... Electrodes Z1-Z4 on substrate 1 ... Electrode S on substrate 1 ... Nonlinear resistance element P ... Pixel electrode

Claims (2)

A plurality of first electrodes formed on one of the substrates, and a plurality of second electrodes formed on the other substrate and the plurality of first electrodes. A plurality of non-linear resistance elements are connected to each of the second electrodes, and a plurality of pixel electrodes connected to the second electrode via the non-linear elements are formed. In liquid crystal display devices,
A plurality of third electrodes are formed on the other substrate so as not to overlap the pixel electrode, and are arranged in a gap between the adjacent pixel electrodes and intersecting the second electrode in a plane. The liquid crystal display device, wherein the plurality of third electrodes are connected to each other and electrostatically shield the adjacent pixel electrodes. The liquid crystal display device according to claim 1, wherein the plurality of third electrodes are formed of a transparent member.

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