JPH0430125A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To reduce the asymmetry of a switching element due to parasitic capacity, and to reduce flicker or burning by avoiding the overlap in point of a pattern of an electrode to execute serial connection and the electrode on an opposite substrate, and reducing the parasitic capacity. CONSTITUTION:First metal 31 made of Ta and an insulating film 32 made of TA2O5 are formed on an insulating substrate 30, and a display picture element electrode 33 made of an ITO film is formed. First wiring 34 made of Cr, second metal 35 incorporated into one body with it, and a second metal electrode 36 connected to 33 are formed. Thus, a first non-linear resistance element 37 and a first substrate 40 are obtained. On the other hand, wiring 42 intersecting the wiring 34 nearly at right angles is formed on the insulating substrate 41, and a second substrate 43 is obtained. The substrates 40 and 43 are opposed to each other, and a liquid crystal 44 is put between them.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention provides display using a switching element such as a nonlinear element (hereinafter referred to as an MIM element) having a metal-insulating film-metal structure. The present invention relates to an active matrix liquid crystal display device having a pixel electrode array.

(Prior Art) Regarding display devices using liquid crystals, active matrix type liquid crystal display devices with large capacity and high density are being actively developed and put into practical use for use in television displays, graphic displays, and the like. In such display devices, semiconductor switches are used as means for driving and controlling each pixel so that high contrast display without crosstalk can be performed. As the semiconductor switch, an MIM element or the like formed on a transparent insulating substrate is used because it is capable of transmissive display and can easily be made large in area.

FIG. 3 is a projection diagram of one pixel pattern onto a display pixel electrode array substrate in a conventional active matrix liquid crystal display device using MIM. In FIG. 3, a second metal electrode 3 is formed on the array substrate so as to overlap a first metal electrode 2 that is integrated with the signal wiring 1, and an insulating film is formed between the first and second metal electrodes 2 and 3. interposed therebetween, and constitutes a switching element 4 as an MIM element. The second metal electrode 3 is connected to the display pixel electrode 5.

On the other hand, a scanning electrode 6 is formed on the counter substrate in a direction perpendicular to the signal wiring 1, and is configured to drive the liquid crystal present in the gap between the scanning electrode 6 and the display pixel electrode 5.

FIG. 4 is an equivalent circuit diagram of one pixel in the MIM type liquid crystal display device whose planar structure is shown in FIG. 3.

In FIG. 4, the MIM element is expressed as a parallel connection of a nonlinear resistance RHIM and a capacitor CMIM, and the first metal electrode 2 of the MIM element is connected to the signal wiring 1, and the second metal electrode 3 and the display pixel electrode 5 are connected. .

A liquid crystal capacitor CLC is formed by the display pixel electrode 5, the scanning electrode 6, and the liquid crystal layer 10.

Next, a method of driving this type of liquid crystal display device will be described. That is, during the period (switching period) in which the selection voltage (voN) is applied to the scan electrode 6, the display pixel electrode 5 is set to a potential corresponding to the signal wiring potential, and the non-selection voltage (Vo, P) is applied to the scan electrode 6. ) is applied (holding period), the display pixel electrode 5 holds this potential. As a result, a potential difference corresponding to the video signal voltage is applied to the liquid crystal layer 10 sandwiched between the display pixel electrode 5 and the scanning electrode 6.

Then, by changing the arrangement state of the liquid crystal layer 10 in accordance with this potential difference, the light transmittance of this portion also changes, and an image is displayed.

Incidentally, the capacitance ratio between CLc and CMIM is a design element that influences the image quality of the MIM type liquid crystal display device.

When the value of CMIM/CLc is large, the high resistance region of the nonlinear resistor RHIH becomes the operating region due to a decrease in the voltage applied to the MIM element during the switching period due to capacitance division. As a result, the ability to write signal potentials to display pixel electrodes is reduced, leading to a reduction in contrast ratio. Furthermore, during the holding period, variations in the display pixel electrode potential corresponding to changes in the signal potential increase due to capacitive coupling between the signal wiring and the display pixel electrode via the CMIM, which leads to an increase in crosstalk. However, making the HIM value small and uniform is not easy to deal with due to limitations in the manufacturing process, especially in the minimum processing dimension accuracy.

Furthermore, since liquid crystals are usually driven by alternating current voltages with positive and negative symmetry, voltages with different polarities are also periodically applied to the MIM element. On the other hand, the nonlinear resistance of RHIH may not be symmetrical in positive and negative directions due to differences in the materials of the first and second electrodes, or differences in the interface state between the insulating film and the first and second electrodes. In that case, even if the input voltage is symmetrical in positive and negative directions, the voltage applied to the liquid crystal becomes asymmetrical in positive and negative directions, causing flicker and burn-in.

(Problems to be solved by the invention) As a means to avoid these problems, for example,
As described in Japanese Patent No. 144584, a method has been proposed in which two MIM elements are connected in series with opposite polarities and used as a switching period.

FIG. 5 is a projection diagram of one pixel pattern onto a display pixel electrode array substrate in such an MIM type liquid crystal display device. In FIG. 5, an isolated first
A second metal electrode 20 integrated with the signal wiring 1 and another second metal electrode 21 connected to the display pixel electrode 5 separated from this are formed so as to overlap the metal electrode 2. Also, a first metal electrode 2 and two second metal electrodes 20.
An insulating film is interposed in the gap 21, and a switching element 4 is constituted by two MIM elements 22 and 23 connected in series with opposite polarity by a first metal electrode 2. On the other hand, scanning electrodes 6 are provided on the counter substrate in a direction perpendicular to the signal wiring 1.
is formed to drive the liquid crystal present in the gap between the display pixel electrode 5 and the display pixel electrode 5.

FIG. 6 is an equivalent circuit diagram of one pixel in the MIM type liquid crystal display device whose planar structure is shown in FIG.

In FIG. 6, except for the structure of the switching element 4, the structure of the fourth
It has the same configuration as the figure. However, in the case of this structure, it is necessary to consider the capacitance Cx between the first metal electrode 2 and the scanning electrode 6 that connect the two MIM elements 22 and 23 in series.

Here, the potential difference between the scanning electrode 6 and the signal wiring 1 is V8. When , the voltage applied to the MIM element 22 whose second metal electrode 20 is connected to the signal wiring 1 is vMo, and MI where the second metal electrode 21 is connected to the display pixel electrode 5.
If the voltage applied to the M element 23 is vM2, the following values are obtained.

V − (C*C+(C+C)ICx)MI
LCHIM LCHIM* V sp/ (C
LC* CMIN” (etc + CMIM)
*(CMIN + CX) l・・・・・・■vM2
″″CLC*CMIM*vSP/(CLC*CMIM1
(C+C)*(C,,M+Cx)I LCHIM...■ Therefore, a voltage higher than that of the MIM element 23 is always applied to the MIM element 22. 2 to reduce the value of CMIM/CLo or cancel the characteristic asymmetry.
When MIM elements 22 and 23 are connected in series with opposite polarities, characteristic asymmetry occurs due to the effect of Cx, which causes problems such as flicker and burn-in.

This invention was made in view of such conventional circumstances.

[Structure of the Invention] (Means for Solving the Problems) This invention reduces the capacitance CMIN of an MIM element.
Alternatively, the present invention relates to an active matrix liquid crystal display device that uses two MIM elements connected in series with opposite polarities as switching elements in order to offset the asymmetry in characteristics of a single MIM element. The electrodes connecting the two MIM elements in series and the scanning electrodes are configured so as not to face each other with the liquid crystal layer in between, thereby reducing the parasitic capacitance between these electrodes and the scanning electrodes.

(Function) In active matrix type liquid crystal display devices using MIM, to reduce CMIM, which causes a decrease in contrast ratio and crosstalk, or to reduce the asymmetry of the characteristics of a single M1M element, which causes flicker and burn-in. In order to cancel this out, two MIM elements connected in series with opposite polarities may be used as a switching element. In this case, characteristic asymmetry occurs due to the presence of parasitic capacitance between the electrode connecting the two MIM elements in series and the scanning electrode, and flicker and burn-in may occur due to this. In order to prevent this, the present invention reduces the parasitic capacitance between the electrodes used for this series connection and the scanning electrodes.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a projection view and a sectional view showing an embodiment of the present invention, FIG. 1(a) is a projection view of one pixel button onto a display pixel electrode array substrate, and FIG. A in Figure 1 (a)
-A- represents a firewood plan corresponding to the cross section. To explain the manufacturing process in FIG. 1, first, a Ta film is formed in a predetermined shape on the entire surface of an insulating substrate 30 made of, for example, glass, and then the Ta film is anodized to form an anodized film. Then, by further patterning the Ta film, a first metal 31 made of Ta and an insulating film 32 made of Ta205 are formed.

Subsequently, after forming an ITO film on the entire surface of the insulating substrate 30, the ITO film is patterned to form the display pixel electrode 33. Next, after forming a Cr film on the entire surface of the insulating substrate 30 , the Cr film is patterned to form a first wiring 34 , a second metal 35 integrated therewith, and a first wiring connected to the display pixel electrode 33 . 2 metal electrodes 36 are formed.

In this way, the first nonlinear resistance element 37 having the first metal 31-insulating film 32-second metal 35 structure and the first metal 31-
A switching element 39 is obtained in which second nonlinear resistance elements 38 having an insulating film 32 - second metal 36 structure are connected in series by the first metal 32 . Then, a first substrate 40 is obtained in which the switching element 39, the display pixel electrode 33, and the first wiring 34 are formed on the entire surface of the insulating substrate 30. On the other hand, a second substrate 43 is obtained by forming a second wiring 42 in a direction approximately perpendicular to the first wiring 34 on the entire surface of an insulating substrate 41 made of glass, for example. A liquid crystal 44 is sandwiched in a gap formed by combining the first substrate 40 and the second substrate 43 so that their surfaces face each other.

In this embodiment, the first and second nonlinear resistance elements 37 and 38 are connected in series in a portion of the first substrate 40 where the second wiring 42 is not present in a projected view on the whole surface thereof, for example, between adjacent second wirings 42. A first metal 31 is present. As a result, C in equation 0, which corresponds to the capacitance between the first metal 31 and the second wiring 42, is
The value of X decreases, and the first and second nonlinear resistance elements 37.3
Since the characteristic asymmetry of No. 8 is reduced compared to the conventional case, flicker, burn-in, etc. caused by this are less likely to occur.

FIG. 112 is a diagram showing another embodiment of the present invention, and shows a projected view of one pixel pattern on a display pixel electrode array substrate. This embodiment differs from the embodiment shown in FIG. 1 in the position of the switching element 39 and the shape of the second wiring 42. That is, the first and second nonlinear resistance elements 37.
38 are connected in series, the first metal 31 connects the first metal 38 in series to the portion where the second wiring 42 is not present, for example, the second
It exists in a slit portion 50 provided in the wiring 42.

Therefore, this embodiment is also '! Needless to say, this embodiment has the same effect as the embodiment shown in Fig. s1.

[Effects of the Invention] The present invention provides a liquid crystal display device having a configuration in which two MIM elements connected in series with opposite polarities are used as a switching element. By avoiding the overlap and reducing the parasitic capacitance in this part, it is possible to reduce the asymmetry in the switching element characteristics caused by this parasitic capacitance, and as a result,
An active matrix liquid crystal display device with less flicker and burn-in can be provided.

[Brief explanation of drawings]

FIG. 1 is a projection view and cross-sectional view of a display pixel electrode array substrate of one pixel pattern, which is an embodiment of the present invention, and FIG. 2 is a display pixel electrode of a one pixel pattern, which is another embodiment of the invention. FIG. 3 is a projection view of one pixel pattern onto the display pixel electrode array substrate in a conventional liquid crystal display device using a single MIM element as a switching element, and FIG. 4 is a projection view onto the array substrate. The equivalent circuit diagram of one pixel in the liquid crystal display device shown in FIG. The upward projection view, FIG. 6, is an equivalent circuit diagram of one pixel in the liquid crystal display device shown in FIG. 31... First metal, 32... Insulating film 33
...Display pixel electrode. 34... first wiring 35. 36... second metal 37... first nonlinear resistance element 38... second nonlinear resistance element 39... switching element 40... first substrate, 42. ...Second wiring 43
...Second substrate, 44...Liquid crystal (d) Fig. Fig. Fig. Fig.

Claims (1)

[Claims] First and second metals having a first metal-insulating film-second metal structure
a switching element in which nonlinear resistance elements are connected in series by the first metal; a first wiring connected to the second electrode of the first nonlinear resistance element; and the second wiring of the second nonlinear resistance element. A first substrate having a display pixel electrode connected to the electrode formed on one main surface; and a second substrate having a second wiring formed on one main surface in a direction substantially perpendicular to the first wiring. and a liquid crystal sandwiched between a gap obtained by combining the first and second substrates such that the one main surface side faces each other, wherein the one main surface side of the first substrate An active matrix type liquid crystal display device, characterized in that the first metal connecting the first and second nonlinear resistance elements in series is present in a portion where the second wiring is not present in a projected view onto a surface.