JPH06281962A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which is improved in contrast ratio and does not generate an increase in wiring capacitance and degradation in spot defect yield. CONSTITUTION:This liquid crystal display device has plural signal electrodes 18 which are formed on substrate 10 and extend in parallel with each other, plural pixel electrodes 20 which are disposed apart with prescribed intervals on the substrates along these signal electrodes 18 and plural nonlinear resistance elements 22 which have laminated lower metals, insulators and upper metals and connect respective display electrodes and the signal electrodes 18. Plural light shielding bodies 24 which are electrically isolated from the signal electrodes 18 and the pixel electrodes 20 are formed between the adjacent pixel electrodes. These light shielding bodies 24 are formed by patterning metallic layers and insulator layers constituting the signal electrodes 18 and the lower metals and insulators of the nonlinear resistance elements 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using a metal-insulator-metal (hereinafter referred to as MIM) element as a switching element and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used for relatively large devices such as clocks and calculators, personal computers, word processors, OA terminal devices, and large-capacity display devices such as TV image displays. Has been done. Conventionally, in a liquid crystal display device, it is general to use a multiplex drive system of matrix display, that is, a so-called simple matrix system. However, this method has a drawback that it is not suitable for large-scale matrix display because the contrast ratio between the display portion and the non-display portion deteriorates as the number of scanning lines increases.

Therefore, as one means for solving this drawback, a method of driving each pixel by a switching element, that is, an active matrix method has been developed. Although a thin film transistor or a non-linear resistance element is used as the switching element, a non-linear resistance element having two terminals and a simple structure is advantageous in terms of manufacturing cost. Various types of nonlinear resistance elements have been developed, but among them, an element having a metal-insulator-metal (MIM) structure has been put into practical use at present.

Since the active matrix type liquid crystal display device using the two-terminal element is most characterized by low manufacturing cost, a so-called black matrix (hereinafter referred to as BM) which shields the non-modulation region when performing monochrome display. ) Is often not provided. This is different from the fact that the practically used amorphous silicon thin film transistor requires such light shielding in order to prevent photoleakage. However, in reality, without the BM, when using a so-called normally white mode in which white is displayed in a cell structure in which no voltage is applied, a good contrast ratio can be obtained because the brightness of black display when a voltage is applied does not sufficiently decrease. May cause problems such as difficulty.

Therefore, as one method for solving such a problem, for example, as shown in JP-A-61-140982, a wiring electrode is used to fill a gap between adjacent pixel display electrodes. A simple BM method has been proposed.

Such a liquid crystal display device is manufactured by the following steps. First, a thin film of a first metal layer made of Ta is formed on a glass substrate by a sputtering method, and then the lower metal of the MIM element and a wiring electrode are patterned by using a first photolithography process. At this time, a wiring electrode acting as a light shield is also provided in a portion corresponding to a gap between adjacent pixel display electrodes. Next, an oxide film serving as an insulating film of the MIM element is formed on the surface of the first metal layer by using an anodic oxidation method or the like. After that, a second metal layer, which will be the upper metal of the MIM element, is formed into a thin film on the entire surface by a sputtering method. Subsequently, the second photolithography process is used to pattern the upper metal of the MIM element. Finally, a thin film of ITO is formed on the entire surface, and then the pixel display electrode (15) is patterned by the third photolithography process to complete the process.

[0007]

As described above, the contrast ratio can be improved without increasing the number of steps by extending a part of the wiring electrode between the adjacent pixel electrodes to form a light shield. However, the liquid crystal display device manufactured by such a manufacturing method has the following problems.

First, since the light shield is formed integrally with the wiring electrode, the area of the wiring electrode is increased by the area of the light shield and the wiring capacitance is increased. Further, when patterning the pixel display electrodes, a pattern having a conventional structure does not cause a display defect.
Even if a defective turning occurs, the pixel electrode and the light shield are electrically connected to each other, resulting in a point defect. Therefore, it causes a decrease in yield.

The present invention is intended to solve the above problems, and an object thereof is to improve the contrast ratio and to prevent an increase in wiring capacitance and a decrease in point defect yield and a liquid crystal display device and its manufacture. The purpose is to provide a method.

[0010]

In order to achieve the above object, a liquid crystal display device of the present invention comprises a plurality of wiring electrodes formed on a substrate and extending substantially parallel to each other, and a plurality of wiring electrodes spaced apart from each other by a predetermined distance. A plurality of pixel electrodes arranged on the substrate along with, a lower metal layer laminated with an insulator,
A plurality of non-linear resistance elements each having an upper metal and connecting each of the pixel electrodes and a wiring electrode, and a plurality of light-shielding members electrically independent from the wiring electrode and the display electrode between adjacent pixel electrodes. Are formed.

According to the liquid crystal display device of the present invention,
The light shield is formed of the same metal as one of the lower metal and the upper metal of the nonlinear resistance element, or the same laminated body as the laminated body of the lower metal and the insulator of the nonlinear resistance element.

A method of manufacturing a liquid crystal display device according to the present invention comprises a step of forming a lower metal film on a substrate, a step of forming an insulating layer on the lower metal layer by a first anodic oxidation, and a step of forming the lower layer. By laminating a metal film and an insulating layer, a lower metal-insulator of a non-linear resistance element, a wiring electrode composed of a lower metal-insulator laminate connected to the non-linear resistance element, and a lower metal-insulator laminate structure. A step of forming a light shield electrically independent of the nonlinear resistance element and the wiring electrode, and performing a second anodic oxidation on the lower metal-insulator and the wiring electrode of the nonlinear resistance element, A step of forming an insulator layer on the side surface,
The method includes a step of forming an upper metal of the nonlinear resistance element and a step of forming a pixel electrode on the upper metal.

[0013]

According to the liquid crystal display device of the present invention, between the adjacent pixel electrodes, at least one of the upper metal and the lower metal forming the non-linear resistance element is formed and the electrically isolated island shape is formed by the wiring electrode and the pixel electrode. Is provided with a light shield. Therefore, the light leaking from the non-pixel portion can be reduced and the contrast ratio can be improved without increasing the manufacturing process. Since the light shield is electrically independent, the wiring capacitance of the wiring electrode does not increase, and if the pattern defect is such that it does not cause a defect in the conventional structure, it does not become a point defect. Compared with the case where no light shield is provided. And the yield does not decrease. To manufacture a liquid crystal display device having such a configuration,
The light-shielding metal layer used in the manufacturing process may be left in an island shape between the adjacent pixel display electrodes in the patterning process.
Therefore, it can be easily formed without increasing the number of manufacturing steps.

When the light shield is made of a laminated body similar to the lower metal and the insulator of the nonlinear resistance element,
It is very effective because it can prevent the coupling between the light shield and the surrounding electrodes. That is, when the pixel pitch becomes smaller, the light shield may cause coupling between the peripheral pixel electrode and the counter electrode via the liquid crystal layer, and flicker or an afterimage may be observed on the screen display. In the future, some kind of ingenuity will be required to develop a large-capacity, high-definition screen. The cause of flicker, etc. is the pulse-like potential fluctuation of the surrounding electrodes, and it suffices to provide a layer capable of absorbing this on the light shielding body. As this layer, the insulator used in the nonlinear resistance element section is used. It was confirmed to be effective.

Therefore, according to the present invention, an oxide film serving as an insulating film of the non-linear resistance element is formed on the surface of the lower metal layer by using an anodic oxidation method or the like, and a laminate of the lower metal layer and the insulating layer is formed. A light shield is formed by a part. In this case, first, a lower metal film is formed on the substrate, and then an insulator layer is formed on the substrate by the first anodic oxidation, and then the lower metal-insulator of the nonlinear resistance element and the lower metal-insulator connected to the lower metal-insulator are connected. A wiring electrode having a laminated structure and a light shielding body having an isolated lower metal-insulator laminated structure are patterned.
Then, the second anodization is performed on the wiring electrode having the laminated structure of the lower metal-insulator of the non-linear resistance element and the lower metal-insulator connected to the non-linear resistance element under the same conditions as the first time, and the side surface of the lower metal is insulated. Is formed. After that, a pattern of an upper metal and a pixel electrode is formed to form an array substrate. Although the second anodic oxidation increases compared to the conventional one, it is effective in preventing a short circuit between the upper and lower electrodes of the nonlinear resistance element.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIGS. 1 and 2, in the liquid crystal display device according to this embodiment, an array substrate 12 having a substrate 10 made of glass, and a counter substrate arranged to face the array substrate at a predetermined interval. 14 and a liquid crystal layer 16 enclosed between these substrates. A large number of signal electrodes 18 as wiring electrodes are formed on the substrate 10 of the array substrate 12.
And a large number of transparent pixel electrodes 20 are formed along each signal electrode at a predetermined distance from each other.

Each pixel electrode 20 is connected to the corresponding signal electrode 18 via an MIM element 22 as a non-linear resistance element. The MIM element 22 has a lower metal 22a made of Ta extending from the signal electrode 18, an insulating film 22b formed on the lower metal, and an upper metal 22c made of Ti formed on the insulating film. There is. The pixel electrode 20 is I
It is made of TO and is formed on the substrate 10 so as to partially overlap the upper metal 22c.

A light shield 24 is formed on the substrate 10 between two adjacent pixel electrodes 20. Each light shield 22 is provided in an island shape electrically independently from the signal electrode 18 and the pixel electrode. An alignment film 26 made of polyimide resin is formed on the substrate 10 so as to overlap the signal electrode 18, the MIM element 22, the pixel electrode 20, and the light shield 24.

On the other hand, the counter electrode 14 has a substrate 28 made of glass, and a large number of scanning electrodes 30 made of ITO are formed on the inner surface of the substrate and extend in the direction orthogonal to the signal electrodes 18. An alignment film 32 made of polyimide resin is formed on the inner surface of the substrate 28 so as to overlap the scanning electrodes 30. The polarizing film 34 is provided on the outer surfaces of the substrates 10 and 28.
Are formed respectively.

Next, a method of manufacturing the liquid crystal display device having the above structure will be described. First, a lower metal layer made of Ta is formed as a thin film on the substrate 10 made of glass by a sputtering method, and then an oxide film as an insulating layer is formed on the surface of the lower metal layer by an anodic oxidation method. Subsequently, the lower metal layer and the oxide film are patterned by the first photolithography process, and as shown in FIG.
Lower metal-insulators 22a, 22 of the nonlinear resistance element 22
b, the wiring electrode 18, and the light shield 24 are formed.

Next, the wiring electrode 1 is formed by the second anodic oxidation.
8 and lower metal-insulators 22a, 2 of the non-linear resistance element
An oxide film is formed again on the laminated body composed of 2b, and the oxide film is formed on the metal surface on the side surface of the wiring electrode and the side surface of the laminated body exposed at the time of the patterning. After that, an upper metal layer made of Ti or the like is formed on the entire surface of the substrate 10 by a sputtering method, and then the upper metal layer is patterned by a second photolithography process. As shown in FIG. The upper metal 22c of 22 is formed.

Subsequently, a transparent conductive film made of ITO is formed on the substrate 10 by a sputtering method, and then the pixel display electrode 20 is patterned by using a third photolithography process as shown in FIG. ,
The array substrate 12 is completed.

Next, after the alignment film 26 made of polyimide resin is formed on the element formation surface of the array substrate 12, the alignment direction of the liquid crystal is regulated by rubbing. Counter substrate 1
In 4 as well, the scanning electrode 30 made of ITO and the alignment film 32 made of polyimide resin are formed by the same steps as described above. The above-mentioned two types of substrates are held opposite to each other with a predetermined space therebetween, and liquid crystal is sealed between these substrates to form a liquid crystal cell. Then, the outer surface of the liquid crystal cell, that is, the substrates 10, 28.
The liquid crystal display device is completed by forming the polarizing films 34 on the outer surfaces of the respective.

The liquid crystal display device configured as described above is provided with the electrically independent island-shaped light shield 24 which is composed of the signal electrode 18 and the pixel electrode 20. Therefore, light leaking from the non-pixel portion can be reduced and the contrast ratio can be improved. Since the light shield 24 is electrically independent, the wiring capacitance of the signal electrode does not increase, and if the pattern defect is such that it does not cause a defect in the conventional structure, it does not cause a point defect, and the light shield is not provided. The yield does not decrease in comparison.

Further, according to the above structure, the light shield 24 is
It is formed by a part of a laminated body of a lower metal layer and an insulating layer. Therefore, it is possible to prevent the coupling between the light shield 24 and the surrounding electrodes, and it is possible to prevent the occurrence of flicker or an afterimage on the screen display.

Further, according to the manufacturing method described above, the nonlinear resistance element 22 is formed on the surface of the lower metal layer by using the anodic oxidation method or the like.
An oxide film serving as an insulating film is formed, and the laminated body of the lower metal layer and the insulating layer is patterned to form the signal electrode 18, a part of the nonlinear resistance element, and the light shield 24. . The lower metal of the nonlinear resistance element 22
The signal electrode 18 having the laminated structure of the insulator and the lower metal-insulator connected to the insulator is subjected to the second anodic oxidation to form the insulator on the side surface of the lower metal. Therefore, it is possible to manufacture a liquid crystal display device having a high contrast ratio and effectively prevent a short circuit between the upper and lower electrodes of the non-linear resistance element 22 simply by increasing the second anodic oxidation as compared with the conventional case. .

The present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention. For example, the light shield 24 may be formed of only the same metal as the lower metal or the upper metal of the nonlinear resistance element 22. In this case, the light shield is formed simultaneously with the patterning of the lower metal layer or the upper metal layer. Thus, even when the light shield is made of only metal, light leakage from the non-display area can be effectively prevented, and the contrast ratio can be improved. Further, the second anodic oxidation is not required, and the manufacturing process can be simplified.

[0029]

As described above, according to the present invention, it is possible to provide a liquid crystal display device and its manufacturing method which can easily improve the contrast ratio without affecting the wiring capacitance and the yield. it can.

[Brief description of drawings]

FIG. 1 is a plan view schematically showing a pixel portion of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG.

FIG. 3 is a plan view showing a state in which a signal electrode and a light shield are formed.

FIG. 4 is a plan view showing a state in which an upper metal is formed.

[Explanation of symbols]

18 ... Signal electrode, 20 ... Pixel electrode, 22 ... Specific linear resistance element, 22a ... Lower metal, 22b ... Insulator, 22c ... Upper metal, 24 ... Light-shielding body.

Claims (4)

[Claims] 1. A plurality of wiring electrodes formed on a substrate and extending substantially parallel to each other, and a plurality of pixel electrodes spaced apart from each other by a predetermined distance and arranged on the substrate along the wiring electrodes. A plurality of non-linear resistance elements each having a lower metal, an insulator, and an upper metal connected between the display electrodes and the wiring electrodes, and electrically connected from the wiring electrodes and the pixel electrodes formed between the adjacent pixel electrodes. A liquid crystal display device comprising: a plurality of independent light shields. 2. The liquid crystal display device according to claim 1, wherein each of the light shields is made of the same metal as one of a lower metal and an upper metal of the nonlinear resistance element. 3. The liquid crystal display device according to claim 1, wherein each of the light shields is formed of the same laminate as a laminate of a lower metal and an insulator of the nonlinear resistance element. 4. A step of forming a lower metal film on a substrate, a step of forming an insulator layer on the lower metal layer by a first anodic oxidation, and a patterning of the lower metal film and the insulator layer. The lower metal-insulator of the non-linear resistance element, the wiring electrode composed of the lower metal-insulator laminated body connected to the non-linear resistance element, the lower metal-insulator laminated structure consisting of the non-linear resistance element and the wiring electrode A step of forming an electrically independent light shield, and a step of performing a second anodic oxidation on the lower metal-insulator of the nonlinear resistance element and the wiring electrode to form an insulator layer on the side surface of the lower metal. A method for manufacturing a liquid crystal display device, comprising: a step of forming an upper metal of the nonlinear resistance element; and a step of forming a pixel electrode on the upper metal.