JPH0764116A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To easily produce the liquid crystal display device free from flickering and seizure by simple stages by executing required connection by using the same transparent conductive films as the transparent conductive films constituting transparent electrodes for liquid crystal driving. CONSTITUTION:The first conductor and second conductor of a wiring part 13 and the second conductor 21a and wiring part 13 of one MIM element 18a are connected by the same transparent conductive film 22 as the transparent conductive film constituting the transparent electrode 14 for liquid crystal driving and are connected to the second conductor 21b of another MIM element 18b by the transparent conductive film 22 constituting the transparent electrode 14 for liquid crystal driving. Then, the liquid crystal display device having a nonlinear resistance element part 12 is supplied with a driving voltage to the transparent electrode 14 from the wiring part 13 via two pieces of the MIM elements 18a, 18b connected in series to reverse polarities. The number of times of thin film formation and etching is decreased by such constitution and the high-grade liquid crystal display device free from the flickering and seizure is obtd.

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 a method for manufacturing the same, and relates to a MIM as a switching element.
And a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, a display device using a liquid crystal display has been
It has come to be used for the display of large dose information in personal computers, word processors, terminal equipment of office automation equipment, image display devices for TV, etc., and accordingly higher quality image display is required. .

A matrix type liquid crystal display device having a switching array formed of a plurality of switching elements arranged in a predetermined array is used for displaying the large dose information. Various types of switching elements are already known as the switching element, but a MIM (conductor / nonlinear resistance film / conductor) element is particularly preferable as a two-terminal nonlinear resistance element having a simple structure and easy to manufacture. It has been put to practical use.

As shown in FIG. 3 for one pixel of the matrix type liquid crystal display device, this MIM element is a Ta thin film formed on the facing surface of one glass substrate 1 facing each other with a liquid crystal (not shown) in between. A first conductor 2 made of, a non-linear resistance film 3 made of a Ta oxide film covering the surface of the first conductor 2, and a Cr thin film provided on the opposite surface of the substrate 1 so as to partially overlap the non-linear resistance film 3. And a transparent conductive film 5 for driving liquid crystal (pixel electrode) on the opposite surface of the glass substrate 1 so as to partially overlap with the second conductor 4.
Are formed.

In the method of manufacturing an array substrate having a plurality of MIM elements, a Ta thin film is formed on the opposite surface of the glass substrate 1 by a thin film forming method such as a sputtering method or a vacuum vapor deposition method, and patterned by a photo etching method. , The first conductor 2 which is one electrode of the MIM element is formed together with the wiring. Next, the surface of the Ta thin film is oxidized by, for example, anodic oxidation using an aqueous solution of citric acid,
A non-linear resistance film 3 made of an oxide film of Ta is formed on the conductor 2. Further, a second conductor 4 which is the other electrode of the MIM element made of a Cr thin film is formed on the nonlinear resistance film 3 by a thin film forming / processing method. Then, a transparent conductive film 5 for driving a liquid crystal is formed on the facing surface of the glass substrate 1 by sputtering and photoetching so as to partially overlap the second conductor 4.

The basic manufacturing technique of this MIM element is disclosed in Japanese Examined Patent Publication No. 55-161273, and its improved technique is disclosed in Japanese Unexamined Patent Publication No. 58-178320.

By the way, the MIM formed as described above
The matrix type liquid crystal display device having elements has a problem that flicker or image sticking occurs due to the asymmetry of the current-voltage characteristics of the MIM element and the image quality is deteriorated.

That is, the matrix type liquid crystal display device is generally driven by an alternating current in terms of reliability, that is, driven by a positive and negative symmetrical alternating voltage, and voltages having different polarities are periodically applied to the MIM element. In this case, the non-linear resistance of the MIM element is positive / negative symmetrical due to the difference in the materials of the first and second conductors 2 and 4 and the difference in the interface state between the first and second conductors 2 and 4 and the non-linear resistance film 3. There are cases where it does not become. That is, even if positive and negative symmetric drive voltages are applied, the voltage applied to the liquid crystal becomes positive and negative asymmetric, and an offset voltage (DC component) remains in the liquid crystal, causing flicker and burn-in.

The cause of this is not necessarily clear, but it is considered that the current generation mechanism depends on the physical properties of the bulk of the oxide film (nonlinear resistance film 3), and the film quality of the oxide film is not uniform or changes with time. Conceivable.

As a means for avoiding the above-mentioned problem of the MIM element, for example, Japanese Patent Laid-Open No. 57-144584 discloses that
It is shown that it is preferable that the MIM elements are connected in series with opposite polarities to form a switching element. As shown in FIG. 4, this switching element includes a first conductor 2 formed in a predetermined pattern made of Ta or a nitrogen-doped Ta thin film formed on the opposite surface of one glass substrate 1, and this first conductor. 2, a non-linear resistance film 3 made of a Ta oxide film or a Ta-oxide film doped with nitrogen, and two pieces made of Cu, Al, etc. formed on both sides of the non-linear resistance film 3. Liquid crystal driving transparent electrode 5 made of SnO ₂ , In ₂ O ₃ or the like is formed on the facing surface of one substrate 1 so as to partially overlap the second conductor 4a and 4b. Has been done.

When the MIM elements are serially connected in reverse polarity to form a switching element, the required driving voltage is doubled, and the symmetry of the current-voltage characteristics is improved due to the increase of the driving voltage, and flicker or burning is caused. It can reduce sticking.

However, in manufacturing a liquid crystal display device in which the MIM elements are connected in series with opposite polarities as switching elements, the first conductor 2 is patterned, the non-linear resistance film 3 is patterned, and the second conductors 4a and 4b are patterned. Patterning, patterning of the liquid crystal driving transparent electrode 5, thin film formation and etching four times are required, and the manufacturing process is complicated.

[0013]

SUMMARY OF THE INVENTION As described above, the MIM
In a liquid crystal display device using an element as a switching element, even if a positive and negative symmetrical alternating voltage is applied, the material difference between the first and second conductors of the MIM element and the interface state between the first and second conductors and the nonlinear resistance film In some cases, due to the difference, etc., positive and negative symmetry may not occur, and flicker or image sticking may occur, resulting in a problem of deterioration of image quality.

As a means for avoiding the problem of the MIM element, it is known that two MIM elements may be connected in series in reverse polarity to form a switching element. However, this liquid crystal display device requires the patterning of the first conductor, the patterning of the non-linear resistance film, the patterning of the second conductor, the patterning of the liquid crystal driving transparent electrode and the four thin film formations and etchings in the manufacturing process. There is a problem that the manufacturing process is complicated.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to easily manufacture a liquid crystal display device free from flicker and image sticking in a simple process.

[0016]

A wiring portion, a liquid crystal driving transparent electrode, and a non-linear resistance element portion composed of two non-linear resistance elements are formed on the facing surface of one substrate facing each other across a liquid crystal, and each non-linear resistance thereof is formed. The element is formed in a laminated structure of a first conductor / a non-linear resistance film composed of an oxide film of the first conductor / a second conductor with the first conductor as a common conductor, and the second conductor of one of the non-linear resistance elements is connected to a wiring portion. In the liquid crystal display device in which the second conductor of the other non-linear resistance element is connected to the liquid crystal driving transparent electrode, the wiring portion is formed in a laminated structure of the first conductor / oxide film of the first conductor / second conductor. , The first of this wiring part
The conductor and the second conductor, and the wiring portion and the second conductor of the one non-linear resistance element are connected by the same transparent conductive film as the transparent conductive film forming the liquid crystal driving transparent electrode, and the other non-linear resistance element second conductor. The liquid crystal driving transparent electrode was connected by the same transparent conductive film as the transparent conductive film forming the liquid crystal driving transparent electrode.

As a method of manufacturing the liquid crystal display device,
A step of forming a laminated structure layer of a first conductor / an oxide film of the first conductor / a second conductor on the opposite surface of one substrate, a step of forming the laminated structure layer in a predetermined pattern, and a laminated structure of the predetermined pattern A step of oxidizing a side surface portion of the first conductor of the layer to form an oxide film of the first conductor on the side surface portion; and a step of forming a laminated structure layer having a predetermined pattern in which the oxide film is formed on the side surface portion of the first conductor. Divided into an element portion having a laminated structure of 1 conductor / a non-linear resistance film made of an oxide film of a first conductor / a second conductor and a wiring portion made of a laminated structure of a first conductor / an oxide film of a first conductor / a second conductor And the step of forming a transparent conductive film, and connecting the first conductor and the second conductor of the wiring part and one of the divided second conductors of the wiring part and the element part, and at the same time, forming the transparent electrode by the transparent conductive film. And the transparent electrode and the other divided second conductor of the element part A step of connection, and so as to form the wiring portion, a transparent electrode and a non-linear resistance element portion for driving the liquid crystal by a step of the second conductor to form two second conductor is divided into two of the element portion.

[0018]

When the liquid crystal display device is constructed as described above, the number of times of thin film formation and etching is reduced as compared with the conventional manufacturing of a liquid crystal display device in which two MIM elements are connected in series with opposite polarities to form a switching element. It is possible to reduce the number, and it is possible to obtain a high-quality liquid crystal display device without flicker or image sticking. In addition, the connection between the conductive layers becomes good, and the wiring resistance can be reduced, which is effective for practical application of a large-sized high-definition liquid crystal display device.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 1 (a) is a schematic view of a matrix type liquid crystal display device according to an embodiment of the present invention formed on one substrate 1.
The plane structure of the pixel is shown in the same section (b) as the BB section and in the same section (c) as the CC section. In this liquid crystal display device, a non-linear resistance element section 12, a wiring section 13, and a liquid crystal driving transparent electrode 14 (pixel electrode) are further aligned on the facing surface of one glass substrate 11 which faces the liquid crystal 10 in between. A film (not shown) is provided, and a transparent electrode 16 and an alignment film (not shown) thereon are also provided on the opposite surface of the other glass substrate 15 to form a structure.

The non-linear resistance element section 12 includes two MIs.
It is composed of M elements 18a and 18b. Each M
In the IM elements 18a and 18b, the first conductor 19 made of a Ta thin film formed on the opposing surface of the one substrate 11 is used as a common conductor, and the nonlinear resistance film 20 made of a Ta oxide film covering the surface of the first conductor 19 is used. , And two second conductors 21a made of a Ti thin film formed separately on the nonlinear resistance film 20.
, 21b. In addition, the wiring unit 13
Similar to the MIM elements 18a and 18b, a first conductor made of a Ta thin film, a Ta oxide film covering the surface of the first conductor, and a second thin film made of a Ti thin film formed on the Ta oxide film.
It is composed of a conductor. In addition, the transparent electrode for driving the liquid crystal 1
4 is composed of a transparent conductive film made of ITO (Indium Tin Oxide).

In this liquid crystal display device, the first conductor and the second conductor of the wiring portion 13 and one MIM
The second conductor 21a of the element 18a and the wiring portion 13 are connected by the same transparent conductive film 22 as the transparent conductive film forming the liquid crystal driving transparent electrode 14, and the second conductor 21b of the other MIM element 18b and the liquid crystal driving The transparent electrode 14 is connected to the transparent electrode 14 by the transparent conductive film 22 that constitutes the transparent electrode 14 for driving the liquid crystal.

Therefore, the liquid crystal display device having the non-linear resistance element section 12 has two Ms connected in series with opposite polarities.
A drive voltage is supplied from the wiring portion 13 to the transparent electrode 14 via the IM elements 18a and 18b.

Next, a method of manufacturing this liquid crystal display device will be described.
This will be described with reference to FIGS. 2 (a) to (c) and (f) are shown in FIG.
It is the figure shown by the BB line disconnection of (a), and (d) and (e) are each the top views of the same vicinity.

First, as shown in FIG.
On the opposite surface of one glass substrate 11 of 7 mm, for example, SiO
_An alkaline protective film (not shown) consisting of ₂ is formed, and a film thickness of 3 is formed on the alkaline protective film by sputtering.
A Ta thin film 23 of 000 angstrom is formed. Next, the entire surface of this Ta thin film 23 is oxidized to form a uniform Ta oxide film 24 on the surface thereof. This Ta oxide film 24
Can be formed by anodic oxidation using the Ta thin film 23 as an anode, a Pt-plated Ti mesh as a cathode, and a 1 wt% ammonium borate aqueous solution as an electrolytic solution. As an example, a voltage of 24 V can be applied between the positive and negative electrodes to form a uniform Ta oxide film 24 having a film thickness of 400 angstrom. In this case, a portion of the surface of the Ta thin film 23 having a thickness of 160 Å becomes the Ta oxide film 24 having a thickness of 400 Å. Next, this Ta oxide film 2 is formed by a sputtering method.
Ti thin film 2 with a thickness of 1200 Å on the entire surface of 4
5 is formed.

Next, for example, a positive type photosensitizer is applied to the entire surface of the Ti thin film 25, exposed and developed using a photomask on which a predetermined pattern is formed, and then, as shown in FIG. The resist film 27 is formed. Then, the resist film 27 is formed by wet etching.
The Ti thin film in the portions where the resist film 27 is not formed is removed, and then the portions where the resist film 27 of the Ta oxide film 24 and the Ta thin film 23 is not formed are removed by chemical dry etching. The wet etching is carried out by keeping an etching solution obtained by mixing 9 g of EDTA (ethylenediamine-tetraacetic acid), 400 cc of water and 3 ml of ammonia water at room temperature. The chemical dry etching is performed by plasma etching using a mixed gas of CF ₄ and O ₂ .

Next, as shown in (c), while the resist film 27 remains, the side surface of the Ta thin film 23 formed by the above etching is oxidized to form a Ta oxide film 24a. The formation of the Ta oxide film 24a is similar to the case where the Ta oxide film is formed on the entire surface of the Ta thin film.
a thin film 23 is used as an anode, Pt-plated Ti mesh is used as a cathode, and 1% by weight ammonium borate aqueous solution is used as an electrolytic solution for anodic oxidation. In this case, in particular, in comparison with the case where a Ta oxide film is formed on the entire surface of the Ta thin film, the voltage applied between the positive and negative electrodes is increased to
The oxide film is formed thick. Specifically, a voltage of 100 V is applied between the positive and negative electrodes to form a Ta oxide film 24a having a film thickness of 1600 angstroms.

Thereafter, the resist film 27 is removed,
As shown in (d), after forming a pattern (planar shape) in which the wiring portion 13 and the element portion 29 are connected, for example, a positive type photosensitizer is applied to the entire surface of the glass substrate on which the pattern is formed, Exposure and development are performed using a photomask to form a resist film having a predetermined pattern. Then, similar to the etching of the Ti thin film, the Ta oxide film, and the Ta thin film, the Ti thin film is etched by wet etching, and then the Ta oxide film and the Ta thin film are etched by chemical dry etching, as shown in (e). , A first conductor made of Ta thin film and a non-linear resistance film made of Ta oxide film, and Ta thin film and T
a The wiring portion 30 made of an oxide film is divided. in this case,
The side surface 30 of the Ta thin film and the Ti thin film is exposed at the divided portion.

Next, a transparent conductive film made of ITO having a film thickness of 1000 angstrom is formed on the entire surface of the glass substrate on which the element portion 29 and the wiring portion 13 are formed by a sputtering method. Further, for example, a positive type photosensitizer is applied on the transparent conductive film, exposed and developed using a photomask to form a resist film having a predetermined pattern. Then, an etching solution prepared by mixing hydrochloric acid, nitric acid and water in a volume ratio of 1: 0.1: 1 is heated to 30 ° C. to perform etching to remove the transparent conductive film in the portion where the resist film is not formed. As shown in (f), the transparent electrode 14, the transparent conductive film 22 of a predetermined pattern that connects the wiring portion 13 and one of the two conductor forming portions of the element portion 29 formed of the Ta thin film, and the transparent electrode 14 and the element portion 29. The transparent conductive film 22 having a predetermined pattern is formed so as to connect to the other second conductor forming portion made of the Ti thin film. The transparent conductive film 22 that connects the wiring portion 13 and the element portion 29 is the Ta thin film 23 of the wiring portion 13.
And the wiring portion 13 is also formed on the exposed side surface of the Ti thin film 25.
The Ta thin film 23 and the Ti thin film 25 are connected by the transparent conductive film 22 formed on this exposed side surface.

Next, using the transparent conductive film 22 as a resist pattern, the exposed portion between the two second conductor forming portions of the element portion 29 is removed by wet etching similar to the etching of the Ti thin film, and the element portion 29 is removed. Two second conductors 21a and 21b are formed on the above to form a non-linear resistance element section.

After manufacturing the liquid crystal display device, a polyimide is formed on the surface of the array substrate formed as described above on which the nonlinear resistance element portion, the wiring portion 13 and the transparent electrode 14 are formed (opposing surface of one glass substrate). A resin is applied and baked to form an alignment film. Then, the rubbing for controlling the alignment direction of the liquid crystal is performed. On the other hand, on the opposite surface of the other glass substrate 15, the transparent electrode 16 is formed by the same method as the method for forming the transparent electrode of the above one glass substrate, and then a polyimide resin is applied and baked to form an alignment film. . Then, the array substrate is rubbed in a direction twisted by about 90 °. Next, the two substrates are bonded together with a space of 5 to 10 μm so that the major axis direction of the liquid crystal molecules is twisted about 90 ° between the above two types of substrates, and liquid crystal is injected between the two substrates to form a liquid crystal cell. Form. After that, a polarizing plate is arranged on the outer surface of the liquid crystal cell in such a manner that the polarization axis is twisted by about 90 ° to form a liquid crystal display device.

By the way, when the liquid crystal display device is constructed as described above, the number of times of thin film formation and etching is different from that in the conventional manufacture of a liquid crystal display device in which two MIM elements are connected in series in opposite polarities to form a switching element. Less once,
A liquid crystal display device can be manufactured by forming a thin film three times and etching, and a high-quality liquid crystal display device without flicker or image sticking can be easily obtained. Further, the connection between the conductive layers becomes good and the wiring resistance can be reduced, so that it is possible to obtain effects such as being effective for practical application of a large-sized high-definition liquid crystal display device.

[0033]

EFFECTS OF THE INVENTION A wiring portion, a transparent electrode for driving a liquid crystal, and a non-linear resistance element portion composed of two non-linear resistance elements are formed on opposite surfaces of one substrate, and each non-linear resistance element uses the first conductor as a common conductor. It is formed in a laminated structure of a non-linear resistance film / a second conductor composed of a first conductor / an oxide film of the first conductor, a second conductor of one non-linear resistance element is connected to a wiring portion, and a second non-linear resistance element of the other non-linear resistance element is connected. In a liquid crystal display device in which a conductor is connected to a liquid crystal driving transparent electrode, a wiring portion is formed in a laminated structure of a first conductor / an oxide film of the first conductor / a second conductor,
The first conductor and the second conductor of this wiring portion and this wiring portion and the second conductor of the one non-linear resistance element are connected by the same transparent conductive film as the transparent conductive film forming the liquid crystal driving transparent electrode, and the other non-linear resistance is connected. When the second conductor of the element and the transparent electrode for driving the liquid crystal are connected by the same transparent conductive film as the transparent conductive film that also constitutes the transparent electrode for driving the liquid crystal, two conventional MIM elements are connected in series in opposite polarities to form a switching element. The liquid crystal display device can be manufactured by reducing the number of thin film formations and etchings as compared with the manufacturing of the liquid crystal display device described above, and a high-quality liquid crystal display device without flicker or image sticking can be easily obtained. . Also, the connection between the conductive layers is good,
Since the wiring resistance can be reduced, it is possible to obtain effects such as being effective in putting a large-sized high-definition liquid crystal display device to practical use.

[Brief description of drawings]

1A is a diagram showing a planar structure for one pixel formed on one substrate of a matrix type liquid crystal display device according to an embodiment of the present invention, and FIG. FIG. 1C is a sectional view taken along line B-C of FIG. 1B.

FIGS. 2A to 2F are views for explaining a method of manufacturing a matrix type liquid crystal display device which is an embodiment of the present invention.

FIG. 3 is a diagram showing a main part configuration of a conventional matrix type liquid crystal display device.

FIG. 4 is a diagram showing a main part configuration of a matrix type liquid crystal display device in which two MIM elements of the related art are connected in series with opposite polarities.

[Explanation of symbols]

 11 ... One glass substrate 12 ... Non-linear resistance element portion 13 ... Wiring portion 14 ... Liquid crystal driving transparent electrode 15 ... Other glass substrate 16 ... Transparent electrodes 18a, 18b ... MIM element 19 ... First conductor 20 ... Non-linear resistance Films 21a, 21b ... Second conductor 22 ... Transparent conductive film 23 ... Ta thin film 24 ... Ta oxide film 25 ... Ti thin film 27 ... Resist film

Claims (2)

[Claims] 1. A non-linear resistance element section comprising a wiring section, a liquid crystal driving transparent electrode and two non-linear resistance elements is formed on the facing surface of one of the substrates facing each other across the liquid crystal, and each of the non-linear resistance elements is the first. 1st conductor with conductor as common conductor
It is formed in a laminated structure of a non-linear resistance film / a second conductor made of an oxide film of a first conductor, the second conductor of one of the non-linear resistance elements is connected to the wiring portion, and the second conductor of the other non-linear resistance element is the above-mentioned. In a liquid crystal display device connected to a liquid crystal driving transparent electrode, the wiring portion is formed in a laminated structure of a first conductor / an oxide film of the first conductor / a second conductor, and the first conductor and the second conductor of the wiring portion are formed. The conductor and this wiring portion and the second conductor of the one non-linear resistance element are connected by the same transparent conductive film as the transparent conductive film forming the liquid crystal driving transparent electrode, and the second conductor of the other non-linear resistance element and the above A liquid crystal display device, wherein the liquid crystal driving transparent electrode is connected by the same transparent conductive film as the transparent conductive film forming the liquid crystal driving transparent electrode. 2. A non-linear resistance element section composed of a wiring section, a liquid crystal driving transparent electrode and two non-linear resistance elements is formed on the facing surface of one of the substrates facing each other with the liquid crystal interposed therebetween, and each of the non-linear resistance elements is the first. 1st conductor with conductor as common conductor
It is formed in a laminated structure of a non-linear resistance film / a second conductor made of an oxide film of a first conductor, the second conductor of one of the non-linear resistance elements is connected to the wiring portion, and the second conductor of the other non-linear resistance element is the above-mentioned. In a method for manufacturing a liquid crystal display device connected to a liquid crystal driving transparent electrode, a step of forming a laminated structure layer of a first conductor / an oxide film of the first conductor / a second conductor on the opposite surface of the one substrate, A step of forming the laminated structure layer in a predetermined pattern; a step of oxidizing a side surface portion of the first conductor of the laminated structure layer in the predetermined pattern to form an oxide film of the first conductor on the side surface portion; A layered structure layer having a predetermined pattern in which an oxide film is formed on the side surface of the conductor is provided with an element portion composed of a layered structure of a first conductor / a non-linear resistance film composed of an oxide film of the first conductor / a second conductor 1
A step of dividing the conductor into an oxide film / a wiring part having a laminated structure of a second conductor; and forming a transparent conductive film to form the first conductor and the second conductor of the wiring part, and the wiring part and the element part. A step of connecting one of the divided second conductors and at the same time forming a transparent electrode by the transparent conductive film, and connecting the transparent electrode and the other divided second conductor of the element part; And a step of forming two second conductors by dividing the second conductor into two, the wiring portion, the liquid crystal driving transparent electrode, and the non-linear resistance element portion are formed.