JPH07225400A - Production of liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device which eliminates the asymmetry of the current-voltage characteristics of nonlinear resistance elements which is the cause for a burn and with which display of high image quality is obtainable. CONSTITUTION:The nonlinear resistance element part is constituted by forming a first conductor 19, forming a nonlinear resistor 20 consisting of an oxidized film of the first conductor 19 on the surface part of the first conductor 19 and forming second conductors 21a, 21b of two pieces of the nonlinear resistance elements on this nonlinear resistor 20 in the process or producing the liquid crystal display device in which the nonlinear resistance element part consisting of two pieces of the nonlinear resistance elements consists of a laminated structure of the first conductor/nonlinear resistor/second conductor with the first conductor used as a common conductor. This nonlinear resistance element part is heat treated at a temp. at which the ratio X of the max. electrostatic capacity of the pixel part of the liquid crystal layer and the electrostatic capacity of the nonlinear resistance elements and a heat treatment temp. Y( deg.C) satisfy a relation Y>=8.2XX+45 after the formation of the second conductors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal display device, and more particularly to a method of manufacturing a matrix type liquid crystal display device having a non-linear resistance element made of an MIM element as a switching element.

[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 displaying large-capacity information in personal computers, word processors, terminal equipment such as office automation equipment, and image display devices for TV, 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 resistor / conductor) element is practically used as a two-terminal nonlinear resistance element having a simple structure and easy to manufacture. Has been converted.

As shown in FIG. 4 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,
It is composed of a second conductor 4 formed of a Cr thin film formed on the opposing surface of the substrate 1 so as to partially overlap the nonlinear resistance film 3.

A transparent conductive film 5 (pixel electrode) for driving a liquid crystal is provided on the opposite surface of the one glass substrate 1 so as to partially overlap the second conductor 4 of the MIM element.

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 evaporation method, and then 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 portion of the Ta thin film is oxidized by, for example, anodic oxidation using a citric acid aqueous solution to form the non-linear resistance film 3 made of a Ta oxide film on the first conductor 2.
Further, a Cr thin film is formed on the non-linear resistance film 3 by a thin film forming method and patterned by a photo etching method to form a second conductor 4 which is the other electrode of the MIM element. After that, a transparent conductive film is formed by a sputtering method and patterned by a photoetching method to form a second film.
It is manufactured by forming a transparent conductive film 5 for driving a liquid crystal on the opposite surface of the glass substrate 1 so as to partially overlap the conductor 4.

A basic manufacturing technique of this MIM element is disclosed in Japanese Patent Publication No. 55-161273, and an improved technique thereof is disclosed in Japanese 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 from the viewpoint 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. In other words, even if positive and negative symmetrical drive voltages are applied, the voltage applied to the liquid crystal becomes positive and negative asymmetric, and the offset voltage (D
C component) remains, causing flicker and image sticking.

The cause is not necessarily clear, but the mechanism of current generation depends on the physical properties of the bulk of the oxide film (nonlinear resistance film 3), and it is thought that 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. 144584/1982 discloses a method described in 2
It is shown that it is preferable that the MIM elements are connected in series with opposite polarities to form a switching element.

When two MIM elements are connected in series with opposite polarities as described above, the required driving voltage is doubled, and the symmetry of the current-voltage characteristic is improved by the increase of the driving voltage, and the operation starts. It is possible to sufficiently reduce flicker and image sticking in the initial stage. However, even if two MIM elements are connected in series with opposite polarities in this way, the symmetry of the current-voltage characteristics may be lost after a long time operation, and seizure may occur. Further, due to the increase in the driving voltage, the withstand voltage of the IC of the driving circuit is exceeded, which makes it difficult to drive the liquid crystal display device and there is a problem that sufficient contrast cannot be obtained.

Therefore, in order to eliminate such a problem, it is necessary to reduce the driving voltage and thin the non-linear resistance film of the MIM element so that sufficient contrast can be obtained.

On the other hand, as a method of manufacturing a liquid crystal display device in which one MIM element is arranged for each pixel, a method of performing heat treatment after forming the first conductor and the nonlinear resistance film of the MIM element and before forming the second conductor is special. JP-A-58-52680, JP-A-6-62
It is disclosed in Japanese Patent Laid-Open No. 2-62333, Japanese Patent Laid-Open No. 63-50081, and the like.

[0015]

SUMMARY OF THE INVENTION As described above, the MIM
A liquid crystal display device having an element as a switching element,
Even if a positive and negative symmetrical AC voltage is applied, the first and second MIM elements,
Due to the difference in the material of the second conductor and the difference in the interface state between the first and second conductors and the non-linear resistance film, positive and negative symmetry may not occur, and flicker or image sticking may occur, resulting in deterioration of image quality. There is.

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, even if the two MIM elements are connected in this way, the symmetry of the current-voltage characteristics after long-term operation is broken, and flicker or burn-in occurs. In addition, the drive voltage rises and the drive circuit IC
There is a problem that the liquid crystal display device is difficult to drive due to exceeding the withstand voltage and the sufficient contrast cannot be obtained. Therefore, in order to eliminate such a problem, it is necessary to reduce the driving voltage and thin the non-linear resistance film of the MIM element so that sufficient contrast can be obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to obtain a liquid crystal display device which does not cause image sticking not only at the beginning of operation but also after operation for a long time.

[0018]

A pair of substrates facing each other with a liquid crystal sandwiched between them has a wiring section, a liquid crystal driving transparent electrode, and a non-linear resistance element section composed of two non-linear resistance elements. Formed, and each of the nonlinear resistance elements has a first
It is formed in a laminated structure of a first conductor / a non-linear resistor made of an oxide film of the first conductor / a second conductor having a conductor as a common conductor, and the second conductor of one of the non-linear resistance elements is connected to a wiring portion, and the other In a method for manufacturing a liquid crystal display device in which a second conductor of a non-linear resistance element is connected to a liquid crystal driving transparent electrode, a step of forming a non-linear resistance element portion on a facing surface of one substrate, A step of oxidizing a surface portion of one conductor to form a non-linear resistor made of an oxide film of the first conductor; a step of forming a second conductor of two non-linear resistance elements on the non-linear resistor; After the formation of two conductors, the ratio CLC / CMIM = X of the maximum capacitance CLC of the pixel portion of the liquid crystal layer to the capacitance CMIM of the non-linear resistance element and the heat treatment temperature Y (° C.) are Y ≧ 8.2 × X + 45 Heat treatment at a temperature that satisfies I chose

Further, the step of forming the first conductor on the opposing surface of the one substrate by the non-linear resistance element portion, and the oxidation of the surface portion of the first conductor to oxidize the first conductor having a film thickness of 400 to 900 angstroms. A step of forming a non-linear resistor made of a film, and a second step of forming two non-linear resistive elements on the non-linear resistor.
The step of forming a conductor, and Y ≧ 8.
The heat treatment is performed at a temperature satisfying the relation of 2 × X + 45.

[0020]

As described above, when the non-linear resistance element section is formed, especially after the second conductor is formed, the non-linear resistance element section is heat-treated at a temperature satisfying the relation of Y ≧ 8.2 × X + 45, for example, the liquid crystal material is changed. Even in the case, the asymmetry of the current-voltage characteristic of the non-linear resistance element, which is the cause of the image sticking, can be eliminated.

The thickness of the nonlinear resistance film is set to 400 to 900.
When the thickness is made thicker, it is possible to eliminate the fluctuation of the current-voltage characteristic of the non-linear resistance element, which is the cause of the image sticking, by driving the IC at a voltage lower than its withstand voltage.

[0022]

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

Example 1. FIG. 2 shows a sectional structure of a main part of a matrix type liquid crystal display device according to an embodiment of the present invention, and FIG. 3 shows a planar structure for one pixel formed on one of the substrates. This matrix type liquid crystal display device has a liquid crystal 1
On the facing surface of one glass substrate 11 facing each other across 0,
A nonlinear resistance element portion 12, a wiring portion 13, and a liquid crystal driving transparent electrode 14 (pixel electrode) are provided, and an alignment film (not shown) is further provided thereon. Further, a transparent electrode 16 and an alignment film (not shown) formed on the transparent electrode 16 are also formed on the opposite surface of the other glass substrate 15.

The non-linear resistance element section 12 includes two MIs.
It is composed of M elements 18a and 18b (non-linear resistance elements). Each of the MIM elements 18a and 18b has a first conductor 19 made of a Ta thin film formed on the opposing surface of one substrate 11 as a common conductor, and a nonlinear resistance made of a Ta oxide film covering the surface of the first conductor 19 is used. The film 20 and two second thin films made of a Ti thin film formed on the opposite surface of the one glass substrate 11 so as to partially overlap the non-linear resistance film 20.
It is composed of conductors 21a and 21b, one second conductor 21a of which is connected to the wiring portion 13 and the other second conductor 21b of which is connected to the liquid crystal driving transparent electrode 14.

Therefore, in the liquid crystal display device having the non-linear resistance element section 12, a drive voltage is supplied from the wiring section 13 to the liquid crystal drive transparent electrode 14 through the two MIM elements 18a and 18b connected in series with opposite polarities. To be done.

The wiring portion 13 has a Ta thin film and the Ta thin film.
It consists of a Ta oxide film covering the thin film and a Ti film formed on this Ta oxide film. The transparent electrodes 14 and 16 are each made of an ITO (Indium Tin Oxide) thin film.

Next, a method of manufacturing this liquid crystal display device will be described.
It will be described with reference to FIG. 1 which is a cross-sectional view taken along the line AA of FIG.

First, as shown in FIG.
On the opposite surface of one glass substrate 11 of 7 mm, for example, Si
An alkali protection film (not shown) made of O ₂ is formed, and a Ta thin film 22 having a film thickness of 3000 angstrom is formed on the alkali protection film by a sputtering method.
Then, as shown in (b), the Ta thin film 22 is patterned into a predetermined shape by a known photoetching method. The patterning of the Ta thin film 22 can be effectively performed by plasma etching using a mixed gas of CF ₄ and O ₂ .

Next, the entire surface of the Ta thin film 22 patterned into the above-mentioned predetermined shape is oxidized, and a film thickness of 5 is formed on the surface thereof.
Uniform Ta oxide film 23 having a thickness of 00 to 800 angstroms
To form. The Ta oxide film 23 is formed by the Ta thin film 2
2 as an anode, a Pt-plated Ti mesh as a cathode, and a 1 wt% ammonium borate aqueous solution as an electrolytic solution. Specifically, by applying a voltage of 30 to 48 V between the positive and negative electrodes,
A uniform Ta oxide film 23 having a film thickness of 500 to 800 angstrom can be formed.

Next, as shown in FIG.
A Ta thin film having a predetermined shape on which an oxide film is formed is etched by a photo-etching method to remove the Ta thin film and the T film on the surface thereof.
The wiring 24 having a predetermined shape made of an a-oxide film and the element portion 25 having a predetermined shape made of the first conductor 19 made of a Ta thin film and the nonlinear resistance film 20 made of a Ta oxide film on the surface thereof are divided. The etching for dividing the wiring 24 and the element portion 25 can be performed by the same method as the etching for patterning the Ta thin film into a predetermined shape.

Next, a Ti thin film 26 having a film thickness of 1200 angstrom is formed by sputtering on the entire surface of the glass substrate 11 on which the wiring 24 and the element portion 25 are formed, facing each other. Then, as shown in (d), two second conductors 21a and 21b are separated by a predetermined distance on the nonlinear resistance film 20 of the element portion 25 by photoetching.
At the same time as forming the film, on the Ta oxide film of the wiring 24,
Wiring 2 made of a Ti thin film of a predetermined shape, which is connected to the side surface of the Ta thin film therebelow and is connected to one of the second conductors 21a.
Form 7. The second conductor 21a made of this Ti thin film,
The patterning of 21b and the wiring 27 is carried out at room temperature with an etching solution in which 9 g of EDTA (ethylenediamine tetraacetic acid), 400 cc of water and 3 ml of ammonia water are mixed.

Next, the glass substrate 11 is connected to the maximum capacitance CLC of the pixel portion of the liquid crystal layer and the capacitance CMIM of the MIM element.
CLC / CMIM = X and the heat treatment temperature Y (° C.) satisfy the relation of Y ≧ 8.2 × X + 45 for about 1 hour, and as shown in FIG. 2 and FIG. No. 1 on the opposite side of 11
The conductor 19, the nonlinear resistance film 20, and the second conductors 21a and 2a
A non-linear resistance element section 12 including two MIM elements 18a and 18b composed of 1b, and one of the MIM elements 1
The wiring portion 13 connected to the second conductor 21a of 8a is formed.

Thereafter, a transparent conductive film made of ITO having a film thickness of 1000 angstrom is formed on the opposing surface of the glass substrate 11 on which the non-linear resistance element portion 12 and the wiring portion 13 are formed, by a sputtering method. Then, the transparent conductive film is patterned into a predetermined shape by photoetching to form the liquid crystal driving transparent electrode 14.
The patterning of the transparent electrode 14 for driving the liquid crystal can be performed with an etching solution in which water, hydrochloric acid and nitric acid are mixed in a volume ratio of 1: 1: 0.1.

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 12 and the liquid crystal driving 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 liquid crystal driving transparent electrode of the one glass substrate, and the polyimide resin is further applied and fired for orientation. Form a film.
Then, the array substrate is rubbed in a direction twisted by about 90 °. Next, the long axis direction of the liquid crystal molecule is 2
5-1 both boards so that they twist about 90 ° between different types of boards
Bonding is performed with a space of 0 μm, and liquid crystal is injected between both substrates to form a liquid crystal cell. 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 non-linear element portion 12 including the two MIM elements 18a and 18b connected in series with opposite polarities is formed by the above method, a liquid crystal display free from image sticking not only at the beginning of operation but also after a long operation. A large-scale, high-definition matrix type liquid crystal display device having high image quality and high reliability can be realized.

That is, in the conventional liquid crystal display device in which two MIM elements are connected in series with opposite polarities, there is no effect on burn-in after a long time operation, but as in the above manufacturing method, Ta
A non-linear resistance film 20 made of a Ta oxide film is formed on a first conductor 19 made of a thin film, and a second conductor 2 made of Ti is further formed.
After forming 1a and 21b, the ratio X of the maximum capacitance CLC of the liquid crystal layer pixel portion and the capacitance CMIM of the MIM element and the processing temperature Y are about a temperature at which the relation Y ≧ 8.2 × X + 45 is satisfied. The heat treatment for 1 hour can eliminate the seizure at the beginning of the operation and the seizure after the long operation. For example, in a conventional liquid crystal display device in which two MIM elements are connected in series with opposite polarities, when the liquid crystal display device is driven for 1 hour and then turned off, image sticking occurs for several minutes. In the display device, the image sticking can be set to 30 seconds or less.

In the above manufacturing method, if the heat treatment is carried out under the condition of Y <8.2 × X + 45, a sufficient effect cannot be obtained and seizure occurs.

Example 2. In Example 1, in forming a Ta oxide film on the surface of a Ta thin film having a predetermined shape formed on a glass substrate by an anodic oxidation method, specifically, a voltage of 30 to 48 V was applied between the positive and negative electrodes. The case where the Ta oxide film having a film thickness of 500 to 800 angstroms is applied to form a Ta oxide film having a film thickness of 500 angstroms is explained by applying a voltage of 42 V between the positive and negative electrodes by the anodic oxidation method. After that, as in the first embodiment, at a temperature at which the ratio X of the maximum capacitance CLC of the pixel portion of the liquid crystal layer and the capacitance CMIM of the MIM element and the heat treatment temperature Y satisfy the relationship of Y ≧ 8.2 × X + 45. A heat treatment for about 1 hour can eliminate the image sticking at the beginning of operation and the image stick after a long time of operation, and realize a large-scale and high-definition matrix display device with high image quality and high reliability. You can

That is, in the conventional liquid crystal display device in which two MIM elements are connected in opposite polarities, there is no effect on burn-in after a long time operation, and the withstand voltage of the IC of the drive circuit is exceeded due to the rise of the drive voltage. Since it is difficult to drive the liquid crystal display device and sufficient contrast cannot be obtained, it is necessary to reduce the drive voltage so that sufficient contrast can be obtained. To
If the film thickness of the Ta oxide film is set to 700 angstrom and then heat treatment is performed for about 1 hour at a temperature satisfying the relation of Y ≧ 8.2 × X + 45, the current flows well even though the Ta oxide film is thick. Thus, with a drive voltage equal to or lower than the withstand voltage of the IC of the drive circuit, it is possible to eliminate the image sticking at the beginning of the operation and the image sticking after the long operation. For example, in a conventional liquid crystal display device in which two MIM elements are connected in series with opposite polarities, after being driven for 1 hour and turned off, burn-in for about several minutes occurred.
In the liquid crystal display device manufactured by the method of this example, the image sticking can be set to 30 seconds or less.

As for the image sticking, the higher the heat treatment temperature, the greater the reduction effect. The effect depends on the ratio X of the maximum capacitance CLC of the pixel portion of the liquid crystal layer and the capacitance CMIM of the MIM element. Be different. Further, in this manufacturing method, if the heat treatment temperature Y is set to Y <8.2 × X + 45, a sufficient effect cannot be obtained. Further, excessive heat treatment temperature deteriorates other display performance. In order for the heat treatment temperature Y to obtain a sufficient effect against seizure and to achieve both without deteriorating other display performance, Y ≧ 8.2 × X + 45 + (5 to 10) is satisfied. It is desirable to set.

The thickness of the Ta oxide film is 40
0 to 900 angstrom is preferable, and if it is less than 400 angstrom, it is too thin to obtain sufficient current-voltage characteristics. If it exceeds 900 angstroms,
The drive voltage exceeds the withstand voltage of the IC of the drive circuit, which makes it difficult to drive the liquid crystal display device.

[0042]

EFFECT OF THE INVENTION Two non-linear resistance elements are formed on the opposing surfaces of one of the substrates facing each other with a liquid crystal interposed therebetween, and a non-linear resistance film made of an oxide film of the first conductor is formed on the surface of the first conductor. After further forming the second conductor on the non-linear resistance film, if heat treatment is performed at a temperature satisfying the relation of Y ≧ 8.2 × X + 45, the liquid crystal display device can be driven within the withstand voltage range of the IC, causing the burn-in. A certain current −
It is possible to eliminate the fluctuation of the voltage characteristics, and it is possible to eliminate the seizure at the beginning of the operation and the seizure after the operation for a long time.

Even when the non-linear resistance film made of the oxide film of the first conductor is formed to have a large film thickness of 400 to 900 angstroms, the current flows well, and the drive voltage is equal to or lower than the withstand voltage of the IC of the drive circuit. Thus, it is possible to eliminate the image sticking at the beginning of the operation and the image sticking after the operation for a long time, so that the liquid crystal display device can stably obtain a high-quality display.

[Brief description of drawings]

1A to 1D are views for explaining a method of manufacturing a matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of a matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a planar structure for one pixel similarly formed on one of the substrates.

FIG. 4 is a diagram showing a configuration of a main part of a conventional matrix type liquid crystal display device.

[Explanation of symbols]

 11 ... One glass substrate 12 ... Non-linear resistance element part 13 ... Wiring part 14 ... Liquid crystal drive 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 ... Ta thin film 23 ... Ta oxide film 24 ... Wiring 26 ... Transparent conductive film 27 ... Wiring

Continuation of front page (72) Inventor Miyuki Watanabe 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Incorporated company Toshiba Yokohama Office

Claims (2)

[Claims] 1. 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 opposing surface of one of the pair of substrates facing each other across the liquid crystal. Each non-linear resistance element is formed in a laminated structure of a first conductor / a non-linear resistance body made of an oxide film of the first conductor / a second conductor having the first conductor as a common conductor, and the second conductor of one of the non-linear resistance elements is In the method of manufacturing a liquid crystal display device, wherein the second conductor of the other non-linear resistance element is connected to the wiring part and is connected to the liquid crystal driving transparent electrode, the non-linear resistance element part is provided on the opposite surface of the one substrate. A step of forming the first conductor, a step of oxidizing a surface portion of the first conductor to form a non-linear resistor made of an oxide film of the first conductor, and the two non-linear resistors on the non-linear resistor. Forming the second conductor of the element After the second conductor is formed, the ratio CLC / CMIM = X of the maximum capacitance CLC of the liquid crystal layer pixel portion and the capacitance CMIM of the nonlinear resistance element and the heat treatment temperature Y (° C.) are Y ≧ 8. And a step of performing heat treatment at a temperature satisfying the relationship of 2 × X + 45. 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 pair of substrates facing each other across the liquid crystal. Each non-linear resistance element is formed in a laminated structure of a first conductor / a non-linear resistance body made of an oxide film of the first conductor / a second conductor having the first conductor as a common conductor, and the second conductor of one of the non-linear resistance elements is In the method of manufacturing a liquid crystal display device, wherein the second conductor of the other non-linear resistance element is connected to the wiring part and is connected to the liquid crystal driving transparent electrode, the non-linear resistance element part is provided on the opposite surface of the one substrate. A step of forming the first conductor, a step of oxidizing the surface portion of the first conductor to form a nonlinear resistor made of an oxide film of the first conductor having a film thickness of 400 to 900 angstroms, and a step of forming the nonlinear resistor on the nonlinear resistor. The above two A step of forming a second conductor of the non-linear resistance element, and after forming the second conductor, a ratio CLC / CMIM = X of the maximum capacitance CLC of the pixel portion of the liquid crystal layer and the capacitance CMIM of the non-linear resistance element and heat treatment. Temperature Y (℃)
And a step of heat-treating at a temperature satisfying the relation of Y ≧ 8.2 × X + 45.