JPS6130278B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device using liquid crystal. More specifically, the present invention relates to a structure and method capable of correcting defects in MIM elements coupled to each display pixel of a liquid crystal display arranged in a matrix.

With the increase in capacity of liquid crystal display devices, matrix display systems are entering the period of practical use. This matrix display method attempts to display characters at the intersections of many electrodes arranged in the X and Y directions.
Time-division driving is performed by sequentially scanning lines in the X or Y direction. When an arbitrary timing line is selected, a signal for turning on or off display pixels is simultaneously applied to all electrodes connected to the data line on the electrodes connected to the timing line. At this time, if the effective voltage applied to the intersection point is sufficiently larger than the Vth of the liquid crystal, it will turn on, and if the opposite is the case, it will turn off. However, as the number of timing lines increases, the ratio of the non-selection period to the selection period increases, and the ratio of the effective voltage during selection (on) and non-selection (off) becomes smaller. Therefore, if the drive voltage is constant, the on level will be low and sufficient contrast will not be obtained. Although it depends on the type of liquid crystal, the practical limit is about 1/16 duty. Conventionally, in order to increase the duty, a nonlinear element and a display pixel were combined. FIG. 1 shows its equivalent circuit, which includes a timing line 101, a data line 102, a display pixel 103, and a nonlinear element (MIM element) 104. One electrode of the display pixel is an electrode connected to the timing line,
One electrode of the MIM element 104 is an electrode connected to a data line. Next, FIG. 2 shows the static characteristics of the MIM element. According to this current-voltage characteristic, if the absolute value of the voltage is small, the impedance between the MIMs is very large, but the absolute value of the voltage increases. The impedance therefore decreases exponentially.

To briefly explain the basic operation, by scanning the timing line at a constant cycle, a selected or non-selected voltage is applied to the electrodes sequentially connected to the timing line. When an arbitrary timing line is selected, a signal for selecting the on or off state of the liquid crystal is simultaneously applied to the data lines (on the MIM element side) corresponding to the line (on the liquid crystal side) to all lines. At this time, the on/off state of the liquid crystal is determined by the level of the signal.
Electric charge is charged from the MIM element to the liquid crystal. When the timing line is deselected, the impedance of the MIM element increases, the discharge of stored charge decreases, and data is retained. When the liquid crystal is on, the duty can be increased until the effective voltage drops to about Vsat of the liquid crystal.

Since the liquid crystal display device described above is a dot matrix display, it does not contribute to display.
Making the area of the MIM element extremely small,
In order to improve the performance of the MIM device by improving the capacitance ratio with the liquid crystal layer and the current-voltage characteristics, it is necessary to make the tantalum pentoxide film, which is an insulator, extremely thin. Although it varies somewhat depending on the capacity, size, and resolution of the display, the size of the MIM element is several microns. Although a photolithography process is used to form such small elements on a glass substrate or the like, it is extremely difficult to etch the remaining portions except for a line width of several micrometers. Furthermore, since the entire display has a large area ranging from a few centimeters to more than ten centimeters, it is difficult to uniformly etch the display. In addition, the tantalum pentoxide film is only a few hundred micrometers thick and is easily susceptible to pinholes, foreign matter adhesion, and scratches.
MIM element shorts and disconnects. Since pixel defects due to the above-mentioned defects or process defects usually occur at several locations on a single panel, it is desirable to have an MIM element with a structure that allows the defects that occur to be corrected, as well as a simple correction method.

The present invention eliminates the above-mentioned drawbacks and its purpose is to provide a structure with which it is possible to correct the defects that have occurred, and also to provide a method for such correction.

The present invention will be explained in detail below based on examples.

FIG. 3 is an equivalent circuit for realizing an embodiment according to the present invention. 301 to 304 in the figure are the same as in FIG. 1 and are omitted. In the figure, 305 is a display pixel of the same size as 303, and 306 is an MIM element of the same size as 304.

FIG. 4 is an external view of the first embodiment according to the present invention. In the figure, 401 is a timing line (electrode)
This is the portion drawn with dotted lines and is formed in the column direction on one side of the substrate. On the other hand, in the direction of each row for each column, there are two data lines 402,
A MIM element (non-linear switching element) 403 and two liquid crystal drive electrodes 401 are formed on the other substrate. Two MIM elements are formed on any one timing line (electrode), and a liquid crystal drive electrode is divided into two and coupled to each of the MIM elements. The two MIM elements are connected to the same data line, and one liquid crystal display is composed of a display pixel and two MIM elements. After forming the liquid crystal drive electrode, the data line and one
Measure the current-voltage characteristics of the liquid crystal drive electrode connected to the MIM element and check for defects. A method for correcting defects will be explained next with reference to FIG.

FIG. 5 differs from FIG. 4 in that the timing electrodes are not attached, but the rest is the same. A circle 501 in the figure is a portion cut from the data line by a laser repair device due to a defect occurring in the MIM element at that location. Next, circle mark 5
02 is two pieces forming one liquid crystal display.
Since one of the MIM elements and the liquid crystal drive electrodes connected to each MIM element is defective, the defective liquid crystal drive electrode is connected to the other good liquid crystal drive electrode. Although connections are made at three locations in this embodiment, the connection is not limited thereto. Also, one liquid crystal display body is formed.
The space between the MIM element and the liquid crystal drive electrode is narrowed,
By widening the space between the liquid crystal display body and other liquid crystal display bodies, it becomes easier to connect the NESA electrodes, and it becomes easier to distinguish one set of MIM elements. Next, a method of connecting the liquid crystal drive electrodes will be described, but this is one method and is not limited thereto.

Figure 6 shows a pattern of high melting point metals (Cr, Ta, Ni, Fe, Mo, etc.) on a glass substrate 601 as shown in the figure.
602 is formed.

FIG. 7 is a simple schematic diagram of the connection method. In the figure, 701 and 702 are liquid crystal drive electrodes, and 703 is a sixth electrode.
A high melting point metal film formed in the pattern shown in the figure,
4 is each glass substrate. Adjust the high melting point metal film so that it is on the liquid crystal drive electrode that you want to connect as shown in the figure, and then use the laser beam 7 of the laser repair device.
When 05 is irradiated onto the liquid crystal drive electrode from the back side of the high-melting point metal film, the high-melting point metal film evaporates in an instant and can be deposited on the NESA electrode below.
Even if there is a disconnection between the MIM element and the data line, it can be corrected by using the connection method described above.

According to the present invention, even if a defect occurs in an MIM element, another MIM element of the same liquid crystal display can be used.
Since the liquid crystal can be driven, a defect-free liquid crystal display device can be easily realized.

As described above, the present invention has a liquid crystal sealed in a pair of substrates, one of which has a plurality of liquid crystal drive electrodes arranged in a matrix, and the other substrate has a plurality of band-shaped timing electrodes. In the liquid crystal display device, each of the liquid crystal driving electrodes has a non-linear switching element, and each row corresponding to each column of the strip timing electrodes has a plurality of liquid crystal driving electrodes and a plurality of non-linear switching elements. Since linear switching elements are arranged, even if a defect occurs in any one of the plurality of non-linear switching elements, the defective non-linear switching element is cut and removed and the plurality of liquid crystal drive electrodes are made conductive. By connecting with the material, it is possible to completely prevent the occurrence of pixel defects.

[Brief explanation of the drawing]

FIG. 1 shows an equivalent circuit of a conventional liquid crystal display device. FIG. 2 shows an example of the current-voltage characteristics of an MIM element. FIG. 3 is an equivalent circuit of an embodiment according to the present invention. FIG. 4 is an external view of an embodiment according to the present invention. FIG. 5 is an explanatory diagram of an embodiment according to the present invention. FIG. 6 is an external view of an example in which a high melting point metal film is patterned on a glass substrate. FIG. 7 is a schematic diagram of an example of a method of connecting liquid crystal drive electrodes.

Claims (1)

[Claims] 1 A liquid crystal is sealed in a pair of substrates, one of which has a plurality of liquid crystal drive electrodes arranged in a matrix, and the other substrate has a plurality of band-shaped timing electrodes formed in a column direction. In the liquid crystal display device, each of the liquid crystal drive electrodes has a nonlinear switching element, and a plurality of liquid crystal drive electrodes and a plurality of nonlinear switching elements are arranged in each row corresponding to each column of the strip timing electrode. A liquid crystal display device characterized by: