JP3102037B2 - Electro-optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-optical device such as a liquid crystal display. More specifically, the present invention relates to an electro-optical device in which pixel electrodes and non-linear elements connected to the pixel electrodes are arranged, for example, in a matrix on one of a pair of substrates sandwiching a liquid crystal layer.

[0002]

2. Description of the Related Art FIGS. 7 and 8 show an example of a conventional liquid crystal display device as an electro-optical device having a pixel electrode and a nonlinear element connected thereto on one substrate as described above. FIG. 7 is a perspective view of a part of a conventional liquid crystal display device, and FIG. 8 is a plan view of a part of a substrate having a non-linear element.

In FIG. 1, reference numerals 1 and 2 denote a pair of upper and lower substrates sandwiching a liquid crystal layer 3. One of the substrates 1 is provided with a counter electrode 4 made of ITO or the like, and the other substrate 2 is provided with an IT
A large number of pixel electrodes 5 made of O or the like are formed in a matrix. Reference numeral 6 denotes a first conductor made of Ta (tantalum) or the like, 7 denotes an insulator made of TaOx (tantalum oxide) or the like, 8 denotes a second conductor made of Cr (chromium) or the like, and these first conductors. The body 6, the insulator 7 and the second conductor 8 serve as a non-linear element for driving a pixel.
1, hereinafter abbreviated as MIM).

In particular, the illustrated MIM uses a so-called lateral MIM structure in which only the side surface of the first conductor 6 is used as a nonlinear element. The lateral MIM covers the surface other than the side surface of the first conductor 6, that is, the surface other than the portion constituting the MIM with the thick insulator 7 b as a barrier layer, thereby reducing the electric resistance of that portion to the side surface constituting the MIM. This is made higher than the thin insulator 7a so as not to function as an MIM element. With such a structure, the area of the MIM element can be made very small, which is effective in increasing the density and the definition of an electro-optical device such as a liquid crystal display device using the MIM element as a nonlinear element. Technology.

[0005]

However, the above-mentioned conventional electro-optical device has a configuration in which one non-linear element is provided for one pixel (pixel electrode) as shown in FIG. If a defect occurs, there is no way to correct it, and that pixel becomes undisplayable,
There has been a problem that the entire electrode substrate cannot be used as an electro-optical device such as a liquid crystal display device.

The present invention has been proposed in view of the above problems. Even if a non-linear element is defective, it is possible to display the pixel of the non-linear element, which is sufficient for an electro-optical device such as a liquid crystal display device. It is intended to be usable.

[0007]

In order to achieve the above object, an electro-optical device according to the present invention has the following arrangement.

That is, a pair of substrates disposed opposite each other, a liquid crystal layer disposed between the pair of substrates, a counter electrode disposed on one of the pair of substrates, and a liquid crystal layer disposed on the other substrate. An electric device comprising a pixel electrode, a two-terminal element having a non-linear current-voltage characteristic connected to the pixel electrode, and a pixel constituted by the counter electrode, the pixel electrode, and a liquid crystal layer sandwiched therebetween. In the optical device, 1
The two-terminal element connected to the two pixel electrodes is divided into a plurality of the two-terminal elements, and
By correcting the area of the one pixel electrode according to the number of defective two-terminal elements, the ratio of the capacitance of the pixel to the capacitance of the two-terminal element is corrected to 2 to 8. It is characterized by.

As described above, the two-terminal element connected to one pixel electrode is divided into a plurality of two-terminal elements, and the number of defective two-terminal elements among the plurality of divided two-terminal elements is Accordingly, by correcting the area of the one pixel electrode, the ratio of the capacitance of the pixel to the capacitance of the two-terminal device is corrected to 2 to 8, so that the nonlinear element Even if some of the pixels become defective, it is possible to prevent the pixels from becoming unable to display, and to maintain the capacitance ratio at an appropriate value even after correction.

If a mark for correction is provided on the pixel electrode, the area of the pixel electrode can be easily corrected based on the mark, and a notch for correction is formed in the pixel electrode. If so, the area of the pixel electrode can be more easily corrected.

Each of the above-mentioned nonlinear elements may be a so-called lateral MIM in which an insulator is formed on at least a side surface of the first conductor and the insulator formed on the side surface is used as an insulator constituting the nonlinear element. Or other configurations.

Further, the first conductor and the insulator and the second conductor
The area of the portion which becomes a non-linear element for driving the pixel electrode among the overlapping portions of the conductors, that is, the area ratio of the pixel electrode to the effective area of the non-linear element is from 1000 to 40
00. Alternatively, the ratio of the capacitance of a pixel driven by the non-linear element to the capacitance of a part serving as a non-linear element for driving a pixel electrode in a portion where the first conductor overlaps with the insulator and the second conductor is different. It is desirable to be in the range of 2 to 8.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on an embodiment shown in the drawings. FIG. 1 is a plan view of a part of a substrate on an element side showing an embodiment of a liquid crystal display device as an electro-optical device according to the present invention, and FIG. 2 is a cross-sectional view of a main part thereof. The same reference numerals are given to the same members, and the description will not be repeated.

In this embodiment, the nonlinear element in the conventional example shown in FIGS. 7 and 8 is divided into a plurality of pieces without changing the area ratio of the pixel electrode to the nonlinear element. The method of dividing the second conductor 8 is appropriate, but in the illustrated example, dividing the second conductor 8 is the simplest. Therefore, in this example, a plurality of second conductors 8 are provided so as not to change the effective area of the nonlinear element in FIG.
An example in which the connection is divided equally is shown. The number of divisions is arbitrary.

As shown in FIG. 2, the cross-sectional shape of each of the connection portions is formed in the same manner as in FIG. 7, and the side surface of the first conductor 6 and the insulator 7 and the second conductor at each connection portion. 8
Overlap constitute a nonlinear element (MIM element).

In general, when a non-linear two-terminal element such as an MIM is used in a liquid crystal display device, the ratio of the area of the pixel electrode to the non-linear element is an important factor affecting the performance of the liquid crystal display device. FIGS. 7 and 8 show that the sum of the effective areas of the divided nonlinear elements is equal to the effective area of the nonlinear elements in FIGS.
The same characteristics as in the case of can be obtained.

In addition, even if some of the plurality of elements become defective, they can be used as they are or by modifying the connection portions and pixels of the elements as necessary. An example of the correction method will be described with reference to FIG. For example, it is assumed that a non-linear element formed by the second conductor 8n in FIG. 3 becomes defective. First, a part of the second conductor 8n of the defective nonlinear element is cut off using a laser repair or the like and cut off from the pixel electrode 4. Since the ratio of the area of the pixel electrode 3 to the area of the non-linear element changes in this state, a portion 5n corresponding to one eighth of the pixel electrode 5 is cut off from the remaining pixel electrode 5 as shown in the figure. The pixel can be corrected by performing such processing.
The area of the pixel electrode to be cut off is determined according to the number (ratio) of defective elements. Electrode part 5 to be cut off
The shape of n is appropriate.

In some cases, the element may be disconnected when it is short-circuited, and may be used as it is when it is disconnected. In this case, although the capacitance ratio increases, the stability is higher than when the capacitance ratio decreases. Therefore, it is possible to use the pixel electrode without dividing the pixel electrode.

Further, as described above, the ratio of the area of the pixel electrode to the area of the non-linear element (hereinafter referred to as the driving area ratio) is an important factor for the liquid crystal display device. Ta, TaOx, and Cr are used as the conductor, the insulator, and the second conductor, respectively, and the relative dielectric constant of TaOx is about 27, and the driving area ratio when the film thickness is 50 nm is set to 1,000 to 4,000. It is desirable.

This is for the following reason. That is, if the driving area ratio is smaller than 1000 (the area of the nonlinear element becomes larger), a large write current flows when a pixel is selected, and a sufficient potential can be applied to the pixel electrode. A current is generated, and the potential of the pixel electrode cannot be sufficiently maintained. Therefore, when the pixel is selected and when it is not selected, the effective voltage decreases as the driving area ratio decreases.

On the other hand, when the driving area ratio is larger than 4000 (the area of the nonlinear element becomes smaller), the leakage current is small when the pixel is not selected, so that the potential of the pixel electrode can be sufficiently maintained, but the selection of the pixel is not performed. In some cases, a large writing current cannot be obtained, so that a sufficient potential cannot be applied to the pixel electrode. Therefore, when the pixel is selected and when the pixel is not selected, the effective voltage decreases as the driving area ratio increases.

For the above reasons, it is understood that there is an optimum driving area ratio, and there is a driving area ratio in which the change rate of the effective voltage of the pixel with respect to the change of the driving area ratio in the vicinity is zero. The driving area ratio is specifically about 2300 under the above conditions, and the driving area ratio is 1000 to 4
If it is set in the range of 2,000, more preferably in the range of 2,000 to 2,500, the change of the effective voltage applied to the pixel is gradual with respect to the change of the driving area ratio. Can be increased.

The above-mentioned driving area ratio is directly determined by the ratio of the capacitance of the pixel to the capacitance of the non-linear element, that is, the ratio of the capacitance formed by the liquid crystal between the pixel electrode and the counter electrode (hereinafter, referred to as the capacitance).
Capacity ratio). That is, MI
The first conductor 6, the insulator 7, and the second conductor 8 constituting the M element are respectively composed of, for example, tantalum, tantalum oxide (500 angstrom film thickness), and chromium, and have a liquid crystal (liquid crystal thickness of 5 microns). In the case of a liquid crystal display device provided with a counter electrode sandwiching the
00 corresponds to approximately 2 to 8 in the capacity ratio. Therefore, when changing the capacitance of the liquid crystal or the nonlinear element, it is desirable to change the drive area ratio so that the capacitance ratio is set in the range of 2 to 8.

Further, in order to facilitate the above-mentioned correction, the pixel electrode 5 may be provided with an index or the like for cutting off the electrode in advance. FIG. 4 shows a configuration in which a mark 9 such as a small hole for correction is provided on the pixel electrode 5, and the mark 9 can accurately indicate the area of a portion cut out from the pixel electrode. FIG. 5 shows a case in which a notch 10 is formed in the pixel electrode 5 in advance. The notch 10 facilitates the correction, thereby reducing the work required for the correction and increasing the accuracy of the correction.

Further, the arrangement of the divided nonlinear elements is appropriate. For example, as shown in FIG. 6, if the divided nonlinear elements are arranged separately in one pixel,
It is possible to reduce the probability that a plurality of nonlinear elements become defective simultaneously in one pixel.

Although the above embodiment has been described by taking a liquid crystal display device as an example, the present invention can be applied to other various electro-optical devices having a liquid crystal layer.

[0027]

As described above, in the electro-optical device according to the present invention, the two-terminal element connected to one pixel electrode is divided into a plurality of two-terminal elements. By correcting the area of the one pixel electrode according to the number of defective two-terminal elements, the ratio of the capacity of the pixel to the capacity of the two-terminal element is set to 2 to
Since the correction is made to 8, even if one of the nonlinear elements in one pixel becomes defective, the display function of the pixel is maintained by the other nonlinear element, and it is possible to prevent the display from being disabled. At the same time, it is possible to maintain the corrected capacitance ratio (driving area ratio) at an appropriate value, not only to improve the pixel correction rate, but also to apply the area variation of the nonlinear element to the effective voltage of the pixel. The effect can be reduced. As a result, it is possible to improve the yield of an electro-optical device such as an electrode substrate having a non-linear element and, consequently, a liquid crystal display device. In particular, a large-screen electro-optical device in which a non-linear element must be uniformly formed over a large area is required. Yield can be greatly improved.

If a mark for correction is provided on the pixel electrode, the area of the pixel electrode can be easily corrected based on the mark, and a notch for correction is formed in the pixel electrode. This makes it possible to more easily correct the area of the pixel electrode, thereby reducing the work required for the correction and improving the accuracy of the correction.

[0029]

[Brief description of the drawings]

FIG. 1 is a plan view of a part of a substrate on a non-linear element side in a liquid crystal display device as an electro-optical device according to the present invention.

FIG. 2 is an enlarged sectional view taken along the line AA in FIG.

FIG. 3 is a plan view showing a correction procedure when one of the nonlinear elements becomes defective.

FIG. 4 is a plan view of an example in which a marker is provided on a pixel electrode on a substrate on a non-linear element side.

FIG. 5 is a plan view of an example in which a cutout groove is provided in a pixel electrode on a substrate on a non-linear element side.

FIG. 6 is a plan view of an example in which a non-linear element is arranged separately on a substrate.

FIG. 7 is a perspective view of a part of a conventional liquid crystal display device.

FIG. 8 is a plan view of a part of a substrate on a non-linear element side in a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 2 Substrate 3 Liquid crystal 4 Counter electrode 5 Pixel electrode 6 First conductor 7 Insulator 8 Second conductor

Claims (2)

(57) [Claims] A pair of substrates disposed opposite to each other; a liquid crystal layer disposed between the pair of substrates; a counter electrode disposed on one of the pair of substrates; and a liquid crystal layer disposed on the other substrate. An electric device comprising a pixel electrode, a two-terminal element having a non-linear current-voltage characteristic connected to the pixel electrode, and a pixel constituted by the counter electrode, the pixel electrode, and a liquid crystal layer sandwiched therebetween. In the optical device, the two-terminal element connected to one pixel electrode is divided into a plurality of two-terminal elements, and the two-terminal elements are divided into a plurality of two-terminal elements. An electro-optical device, wherein the ratio of the capacity of the pixel to the capacity of the two-terminal element is corrected to 2 to 8 by correcting the area of one pixel electrode. 2. The electro-optical device according to claim 1, wherein
An electro-optical device, wherein the pixel electrode is provided with a mark or cut for the correction.