JPH03210532A - Two-terminal element - Google Patents

Abstract

PURPOSE:To prevent the generation of electric field concentration and to prevent the deterioration of element characteristics by forming the intersected parts of picture element electrodes and driving electrodes as an electrode shape and rounding the terminal parts of either or both of these electrodes. CONSTITUTION:Plural pieces of the picture element electrodes 12 are formed on a substrate 11 of the two-terminal elements provided in a liquid crystal display device used for the display of a liquid crystal television set, etc. The intersected parts of the picture element electrodes 12 and the driving electrodes 13 are formed by overlapping the respective semicircular parts of the projecting parts of the picture element electrodes 12 and the driving electrodes 13 on each other. The shape of the projecting parts is so formed to such a structure in which angled parts are eliminated. The electric field concentration is substantially obviated in this way, by which the deterioration in the two-terminal elements characteristics is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention is applicable to liquid crystal display devices used in display panels of measuring instruments, automobile instrument panels, image display devices of personal computers, displays of liquid crystal televisions, etc. The present invention relates to a two-terminal device.

[Summary of the invention]

This invention provides a two-terminal element in which a nonlinear resistance film is provided between a pixel electrode and a drive electrode, in which the shape of the electrode at the intersection of the pixel electrode and the drive electrode is rounded at the end of one or both electrodes. The purpose of the present invention is to provide a two-terminal element that can prevent electric field concentration from occurring when driving the two-terminal element, prevent deterioration of element characteristics, and greatly improve reliability.

[Background Art] Liquid crystal display devices have advantages over other display devices as small, lightweight, thin, and low power consumption display devices, and have been put into practical use in recent years. In order to increase the amount of information displayed on this type of display device, three-terminal active matrix liquid crystal display devices using thin film transistors, etc., and ZnO
So-called M consisting of varistor and metal-insulating film-metal structure
Two-terminal active matrix liquid crystal display devices such as nonlinear resistance elements using Si-rich nitride films, oxide films, or the like in the edge film of IM type non-shape linear resistance elements are being studied.

Compared to three-terminal devices, two-terminal devices have the following characteristics: fewer films are formed, and the patterning accuracy can be fairly rough.
Application to low-cost, large-area display devices is possible.

FIG. 3(a) is an X-Y matrix panel circuit diagram of a two-terminal active matrix liquid crystal display device using non-linear resistance elements, and FIG. 3(b) is a one-row partial cross-sectional view showing the structure. Usually about 100 to 1000 liquid crystal drive electrodes 1 and column liquid crystal drive electrodes 2 are formed on each of the substrate B and the counter substrate A. The x-Y intersection has a pixel electrode 42 and a nonlinear resistance film 41, and a nonlinear resistance element 4 connected to the column electrode 2.
is provided. A liquid crystal 3 is held between the substrates A and B. FIG. 2 is a plan view and a sectional view showing a conventional two-terminal element using a Si-rich silicon nitride film or the like as a nonlinear resistance element.

After selectively forming a pixel electrode 22 (for example, ITO) on a transparent substrate 21, a nonlinear resistor IJI 24 (for example, silicon nitride) and a driving electrode 23 (for example, Cr) are deposited, and each of them is selectively etched to form a structure. It has become.

Driving of this type of liquid crystal display device is carried out as follows. That is, a large number of row electrodes 1 in FIG. At this time, in order to display with sufficient contrast, the effective voltage applied to the liquid crystal at the selected point must be greater than the saturation voltage of the liquid crystal, and the effective voltage applied to the liquid crystal at non-selected points must be It needs to be lower than the threshold voltage of the liquid crystal. When the nonlinear resistance film 41 is used, at one selection point, the nonlinear resistance film 4
The resistance of the nonlinear resistive film 41 becomes low, making it easier to inject charges into the liquid crystal 3, and during the holding period (when low voltage is applied), the resistance of the nonlinear resistive film 41 becomes higher, making it easier to hold the charges injected into the liquid crystal 3. In this way, the effective voltage applied to the liquid crystal 3 can be kept higher than the saturation voltage of the liquid crystal 3. Furthermore, at non-selected points, the resistance of the nonlinear resistance film 41 does not become so low during writing, and not much charge is injected into the liquid crystal 3, so the effective voltage applied to the liquid crystal 3 is kept relatively small. The threshold voltage can be kept lower than the threshold voltage of the liquid crystal 3. In this way, high contrast can be obtained even if the number of divisions is made considerably large. In the nonlinear resistance element, the composition and structure of the film are determined so that the nonlinear resistance 11Ji41 has a desired resistance value during each of the writing period and the holding period. Furthermore, in order to obtain a sufficient drive margin when displaying with such a liquid crystal display device, the ratio between the capacitance CLC of the liquid crystal section and the capacitance C1 of the nonlinear resistance element section in each pixel must be made sufficiently large. is also necessary. (At least CLC
/Cl≧5. ) Problems to be solved by the invention C] As described above, in a liquid crystal display device using a nonlinear resistance element,
Although it is possible to increase the display capacity, when selected, the nonlinear resistance element has a low resistance, and a large amount of current flows through the nonlinear resistance film to charge the liquid crystal. In particular, areas with extremely high current density are created at the corners of the electrode where electric field concentration is likely to occur. Therefore, with repeated use, the nonlinear resistance film in those areas deteriorates and the voltage range that can be driven is reduced. Shifts are inevitable and pose a problem in terms of reliability. Therefore, an object of the present invention is to provide a two-terminal element having a structure that does not cause extreme electric field concentration.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention devises the shape of the electrode at the intersection of each pixel electrode and each driving electrode. That is, at each intersection, the ends of the projections of one or both of the pixel electrode and the drive electrode are rounded, and both electrodes intersect at the end.

[Example] Examples of the present invention will be described below based on the drawings. 1st
Figures (a) and (b) are diagrams showing a two-terminal element of the present invention. In FIG. 1, a plurality of pixel electrodes 12 are formed on a substrate 11. As shown in FIG. This can be formed, for example, by depositing ITO or the like by sputtering and selectively etching it. Here, the end of the protrusion of the pixel electrode 12 is connected to a zero-order nonlinear resistance film 14 (for example, Si-rich 5iNx) patterned in a semicircular shape and a driving electrode 1.
A two-terminal element is constructed by sequentially depositing 3 (for example, Cr) in this order and etching each layer successively. Here, the end of the projection of the driving electrode 13 is patterned in a semicircular shape. Furthermore, at the intersection of the pixel electrode 12 and the drive electrode 13 that constitute the nonlinear resistance element, the semicircular portions of the protrusion of the pixel electrode 12 and the protrusion of the drive electrode 13 overlap. The shape of the protrusion is such that there are no angular parts. In addition, by providing two intersections as shown in FIG. 1, even if there is some misalignment in the overlapping of the pixel electrode 12 and the drive electrode 13, the total intersection area of the element can be increased. (This can be done without any change. However, it is important that the total element area in this case be as close as possible to the area of one element in the conventional structure.

Figures 4 and 5 show the aging characteristics of a conventional two-terminal element and the two-terminal element of the present invention, respectively. In the conventional two-terminal element, the characteristics begin to shift from around 10' cycles. , I O"cycle, there is a shift of about half an order of magnitude at 20V, whereas in the driving method of the present invention, there is almost no shift in the characteristics even after I O"cycle is applied.

6(a), (b) and FIG. 7(a), (b) are diagrams showing other embodiments of the present invention. In these examples, only one of the pixel electrode 72 or the driving electrode 63 is semicircular to form an intersection. Even with such a structure, electric field concentration can be made difficult to occur. In addition, if the misalignment of the pixel electrode and drive electrode is not a big problem, if you want a high aperture ratio, or if you want to minimize the total element area, it is possible to have only one intersection. It is.

〔Effect of the invention〕

As explained above, according to the present invention, by rounding the shape of the element part of the two-terminal element and making it difficult for electric field concentration to occur, the characteristics of the two-terminal element can be prevented from deteriorating.
It is possible to stably drive liquid crystal display devices and other devices, greatly improving reliability.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a two-terminal element of the present invention, Fig. 1(a) is a plan view, Fig. 1(b) is a cross-sectional view, and Fig. 2 is a diagram showing a conventional two-terminal element. (a) is a plan view, FIG. 2(b) is a cross-sectional view, and FIG. 3(a) is an X-Y matrix panel circuit diagram of a two-terminal element active matrix liquid crystal display device using a nonlinear resistance element. (b) is a cross-sectional view of the device of the part including the nonlinear resistance element, FIG. 4 is a diagram showing the aging characteristics of a conventional two-terminal element, and FIG. 5 is a diagram showing the aging characteristics of the two-terminal element of the present invention. FIG. 6 shows the second terminal of the two-terminal element of the present invention.
FIGS. 6(a) and 6(b) are a plan view and a cross-sectional view, respectively, and FIG. 7 is a diagram showing a third embodiment of the two-terminal element of the present invention. (a) and FIG. 7(b) are a plan view and a sectional view, respectively. 1... Row liquid crystal drive electrode 2.13.23.63.73... Column liquid crystal drive electrode 3... Liquid crystal 4... Nonlinear resistance element 11.21.61, 71, B...Substrate 12.22.42.62.72...Pixel electrode 14.24.41.64.74...Nonlinear resistance film A...Counter substrate

Claims (1)

[Claims] Multiple pixel electrodes are arranged in a matrix on a transparent substrate,
In a two-terminal element consisting of the pixel electrode, a drive electrode, and a nonlinear resistance film, the shape of the intersection of the pixel electrode and the drive electrode constituting the nonlinear resistance element is the same as the shape of the protrusion of one or both electrodes. A two-terminal element characterized by having rounded ends and forming an intersection at the ends.