JPH05307196A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device having a high responding speed, and a wide visual field and having a high image-quality without the irregularity in the display by precisely forming a cell gap value up to a required arbitral level and reducing the dispersion of the values within the surface and further reducing the drop of a voltage applied to the liquid crystal and reducing the dispersion of the varistor voltages. CONSTITUTION:A smooth layer 20 transparent at least in the visible region is provided on an entire surface except for a varistor element part 13 and an electrode terminal part 11 on a lower side glass substrate 10 and the thickness of the smooth layer 20 is kept in the region more than the difference between the thickness of the varistor element 13 and the prescribed cell gap value (d) and preferably a pixel electrode part 12 is divided into the upper and lower parts in the electrically connected state and a pixel forming part side is provided on the transparent smoothing layer 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device, and more particularly to a liquid crystal display device in which a sintered body varistor element formed by a printing method is used as a two-terminal element.

[0002]

2. Description of the Related Art The structure of a liquid crystal display device is roughly classified into a simple matrix system and an active matrix system. In the simple matrix system, pixel electrodes are formed at the intersections of a pair of strip-shaped electrode groups (scan electrode group and signal electrode group) provided at right angles, and a predetermined voltage is applied to these electrode groups by a drive circuit. The liquid crystal in the pixel portion is operated by applying the voltage. This method has the advantage that the system can be realized at a low price because of its simple structure, but since crosstalk occurs between each pixel, the contrast is low,
When displaying a high-definition image on a liquid crystal television or the like, deterioration in image quality is unavoidable.

On the other hand, in the active matrix system, a switching element is provided for each pixel to hold the voltage, and the liquid crystal in the pixel section holds the voltage when the liquid crystal display device is driven in a time division manner. Therefore, the display capacity can be increased, the characteristics relating to image quality such as contrast are excellent, and high image quality display of a liquid crystal television can be realized. However, the active matrix method has a drawback that the structure is complicated, the yield is low, and the manufacturing cost is high. For example, in the TFT type using a thin film transistor as a switching element, it is difficult to increase the product yield because it is necessary to stack five or more thin films in the manufacturing process and finely process the thin film into a predetermined shape. There is a definite disadvantage in increasing the size of.

From the above, it is desired to realize a low cost liquid crystal display device having good characteristics relating to image quality such as contrast and having a simple structure, and as a method for fulfilling such a demand. A two-terminal element type liquid crystal display device using a varistor element is promising.

The two-terminal element type liquid crystal display device is improved as shown in FIG. 10 by improving the simple matrix system.
A liquid crystal 14 and a sintered varistor element 13 that conducts at a predetermined threshold voltage are electrically connected in series between the scanning electrode 11 and the signal electrode 16, and as shown in FIG. The non-linear current-voltage characteristic of the varistor element 13 is used. Here, the threshold voltage of the varistor element is represented by Vc.

FIG. 11 shows the structure of a general two-terminal element type active matrix. As shown here, a large number of pixel electrodes 12 are provided for each scan electrode 11.
Are provided with a predetermined distance (varistor gap) D, and the scanning electrode 11 and the pixel electrode 12 are connected to each varistor element 1
3 is connected with a constant threshold voltage Vc.
As shown in detail in FIG. 6, the sintered varistor element 13 includes varistor particles 13a in which the surface of ZnO single crystal particles 131 is coated with an inorganic insulating film 132 of Mn, Co oxide, or the like (see FIG. 5). ), The varistor particles 13a are fused with a glass frit 13b.

As shown in FIG. 10, the pixel electrode 12 made of a transparent conductive film such as ITO is formed on the lower glass substrate 10.
The scanning electrodes 11 are formed by the photolithography method. Further, 25 parts by weight of glass frit and ethyl cellulose (viscosity 50 c are added to varistor particles classified so as to be as monodisperse as possible within a particle size range of 2 to 10 μm.
10 parts by weight of ps) to form a paste using carbitol as a solvent, and the paste is sintered on the glass substrate 10 by silk screen printing so as to straddle the varistor gap between the scanning electrode 11 and the pixel electrode 12. A body element is formed by a printing method, and this is baked at 480 ° C. for 30 minutes to obtain a varistor element 13.

On the other hand, ITO is formed on the upper glass substrate 17.
The signal electrode 16 is formed of a transparent conductive film such as. Next, an alignment film 15 made of alignment-treated polyimide is formed on the lower glass substrate 10 and the upper glass substrate 17.
In addition, the spacers are used so that the cell gap value matches the characteristics of the liquid crystal, and the gap (cell gap) d between the upper glass substrate 17 and the lower glass substrate 10 is kept at a predetermined value, and they are bonded together. In the meantime, the TN liquid crystal 14 is filled. The polarizing plate 18 is provided outside the cell.
Is installed.

By the way, the electro-optical characteristics of TN liquid crystals generally used in liquid crystal display devices depend on the cell gap d. For example, first, since the response time of a liquid crystal display device is proportional to the square of the cell gap d, in a liquid crystal display device such as a television image display or a display device for a personal computer which requires a high speed response, the cell gap d should be as thin as possible. There is a need to. Further, the viewing angle of the liquid crystal display device becomes wider as the cell gap d becomes narrower. From this point as well, it is desirable that the cell gap be thin. On the other hand, in order to increase the contrast of the liquid crystal display device, it is necessary to reduce the leaked light in the dark state as much as possible. Although the leakage light decreases as the cell gap d becomes thicker, this is contrary to the requirement for the cell gap d due to the problems of the response time and the viewing angle.

Further, since the leaked light intensity of the TN liquid crystal has wavelength dependence, the cell gap d is set so that the leaked light intensity at the wavelength λ = 550 nm, which is the maximum luminosity of human, is minimized. Set. Generally, wavelength λ = 5
The leak light intensity at 50 nm is Δ
Let n be the cell gap and d be the product Δnd of the two.
It becomes minimum when the value of (retardation) is about 0.5 or 1.0. The value of the refractive index anisotropy Δn of the TN liquid crystal is usually around 0.1. Therefore, the cell gap d of the liquid crystal display device using the TN liquid crystal is 5 to 10
It is set in the range of μm and is ± 0.
It is necessary to control with an accuracy of 3 μm or less.

However, when such a TN liquid crystal is used in a liquid crystal display device using a varistor element formed by a printing method, there are the following problems. That is, in FIG. 6, the varistor element 13 has an average particle size of 3
Glass frit 13b with varistor particles 13a of ~ 7 μm
In order to prevent variations in device characteristics, it is necessary to stack at least two layers of varistor particles. However, for example, when varistor particles having an average particle diameter of 5 μm are used, the thickness of the varistor element composed of the two layers becomes 10 μm or more, which causes a decrease in response speed and a decrease in viewing angle, and as a result, deterioration of display performance is unavoidable. Met.

In this case, in order to make the cell gap as narrow as possible, it was considered to use the varistor element itself as the spacer for maintaining the gap. However, there is a large variation in the thickness of the varistor element among the elements, Furthermore, because it is extremely difficult to control the thickness accurately,
Accurate control of the required cell gap is a difficult task, and large variations in cell gap do not occur, which is a major cause of display unevenness.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the above-mentioned conventional liquid crystal display device, and its object is to firstly describe a cell gap d of a liquid crystal display device using a varistor element. Can be accurately formed to a desired value smaller than the thickness of the varistor element, the variation of the cell gap d in the plane of the liquid crystal display device can be reduced, and further, the drop of the voltage applied to the liquid crystal can be reduced. By doing so, and by reducing the variation in the varistor voltage, it is possible to provide a liquid crystal display device having a high response speed, a wide viewing angle, and high image quality without display unevenness.

[0014]

The means provided by the present invention for solving the above-mentioned problems are as follows. That is, the varistor element serves as an active matrix element and connects the scanning electrode and the pixel electrode on the lower glass substrate. The liquid crystal layer is formed between the upper glass substrate and the lower glass substrate facing each other, and is transparent in at least the visible region in a liquid crystal display device driven through the varistor element. A smooth layer is provided on the entire surface of the lower glass substrate excluding the varistor element portion and the electrode terminal portion, and the thickness of the smooth layer transparent in the visible region is the thickness of the varistor element and the predetermined cell gap value. The liquid crystal display device is characterized by having a range not less than the difference.

Alternatively, the varistor element is formed as an active matrix element in a structure for connecting the scanning electrode and the pixel electrode on the lower glass substrate, and the liquid crystal layer is opposed to the upper glass substrate and the lower glass substrate. In a liquid crystal display device provided between a glass substrate and driven via the varistor element, the pixel electrode portion is divided into upper and lower parts in an electrically connected state, and is transparent and smooth at least in a visible region. A layer is provided on the entire surface of the lower glass substrate except a part of the electrode terminal portion and the varistor element portion, and the thickness of the smooth layer transparent in the visible region is the thickness of the varistor element and the predetermined cell gap value. And a part of the pixel electrode is provided on the smoothing layer.

In the liquid crystal display device, a portion of the pixel electrode to which the varistor element portion is connected is made of the same material as that of the scanning electrode.

More preferably, the liquid crystal display device is characterized in that the material of the smooth layer transparent at least in the visible region is a photosensitive polymer.

In another preferred embodiment, the liquid crystal display device is characterized in that the material of the smooth layer which is transparent in at least the visible region is SiO ₂ as a main component.

By the way, in order to form the transparent smooth layer, it is preferable to apply a photofabrication method. Further, it is preferable that the transparent smooth layer usually has an appropriate electric insulating property in order to prevent short circuit and crosstalk. Even when a smooth transparent layer containing SiO ₂ as a main component is formed, it can be formed relatively easily by applying the lift-off method, for example.

[0020]

In the present invention, the transparent smooth layer in the visible region is formed on the entire surface of the lower glass substrate excluding the varistor portion and the electrode terminal portion, and the transparent smooth layer is made of a photosensitive polymer. Film or SiO represented by glass
By using a film containing ₂ as a main component and forming a film with a film thickness equal to or larger than the difference between the varistor element thickness and a predetermined cell gap value, it can be manufactured for a predetermined cell gap value (manufactured to an extremely high precision diameter and commercially available. The cell gap can be maintained by using the cell gap maintaining spacer described in (1) above, and it is possible to easily secure an appropriate value of the cell gap and accurately control the cell gap.

Further, by providing the portion of the pixel electrode forming the pixel portion on the transparent smooth layer, it is possible to reduce the voltage drop applied to the liquid crystal.

Further, in the case where the pixel electrode portion is divided into the upper and lower portions as described above, the following convenient method is provided when forming a portion which is on the lower side of the pixel electrode and is in contact with the varistor element portion. You can get something. That is, when forming the scan electrode, by using a thin film made of the same material as the scan electrode in the portion in contact with the varistor element portion, and by performing the photolithography method at the same time, the varistor gap value is highly accurate. Thus, it becomes possible to manufacture a more uniform device among the elements.

[0023]

【Example】

<Embodiment 1> An embodiment of the liquid crystal display device according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a sectional view showing a liquid crystal display device according to the present invention, and FIG. 2 is a plan view of a part of the varistor element part. As shown in FIG. 1, a Cr film as a conductive thin film having a thickness of 1000 Å is formed on a lower glass substrate 10 made of soda glass coated with SiO ₂ as a base material by using a magnetron sputtering apparatus. The type of the conductive thin film is not limited to Cr, but various metals such as Al, Ta, Ni and Cu, and a transparent conductive film such as ITO can be used. The sheet resistance at this time was 2Ω / □. A resist pattern is formed on this by a photofabrication method, and the scanning electrode 11 is formed with a cerium ammonium nitrate-based etching solution. At this time, the line width of the scanning electrode 11 was 50 μm.

Next, an ITO transparent conductive film was formed using a magnetron sputtering device. At this time, the film thickness was 1000Å and the sheet resistance value of the film was 40 Ω / □. Further, a resist pattern is formed using the photofabrication method to form the pixel electrode 12.
At this time, the varistor gap D between the scan electrode 11 and the pixel electrode 12 formed previously is 20 μm, and the accuracy is ± 2.5.
It was within μm.

The threshold voltage of the varistor element 13 is
Since it is determined by the number of varistor particles existing between the varistor gaps D, the value of the varistor gap D controls the element threshold value. Therefore, the varistor gap D is 3 to 100 μm depending on the liquid crystal used and the driving conditions of the liquid crystal display device.
It is set in the range of. Further, it is necessary to control the dimensional variation range of the varistor gap D to be equal to or smaller than the grain size of the varistor particles used in order to suppress the variation in the threshold voltage of the element. In this example, since the varistor particle size is 5 μm, the accuracy is required to be within ± 2.5 μm.

Next, ZnO powder as the raw material after firing for 1 hour at 1200 ° C., which was pulverized in a ball mill with air classifier to form a ZnO single crystal powder having an average grain size of 5 [mu] m, this Co ₂ O ₃ to 0.5 mol% and MnCO ₃ to 0.5
Mol% was added and fired again at 1150 ° C. for 1 hour to obtain varistor powder having varistor characteristics. To this varistor powder, 25 parts by weight of glass frit and 10 parts by weight of ethyl cellulose (viscosity 50 cps) were added to form a paste using carbitol as a solvent, and the paste was used as the lower glass substrate 1
Sintered body element 13 using silk screen printing method
Print on the pattern. Then, the flattening process of the element thickness printed by the printing method was performed using the roll press apparatus. Further, the sintered body element 13 is completed by firing at 460 ° C. for 1 hour. At this time, when the thickness of the completed varistor element 13 was measured, the average film thickness was 11.0 μm.

Next, a photosensitive acrylic resin (manufactured by Fuji Yakuhin Kogyo Co., Ltd.) as a photosensitive polymer film transparent in the visible region (wavelength 400 to 700 nm) was formed on the lower glass substrate 10 on which the varistor element was formed. Product name FVR) was applied. The coating film thickness is 2.5 μm because the difference between the device thickness of the varistor device 13 of 11.0 μm and the set cell gap value of 8.5 μm is 2.5 μm.
Set to. Next, after exposure with an ultraviolet lamp through a mask, development and rinsing with an FVR developer (mixture of methyl ethyl ketone and isopropyl alcohol) were performed, and post baking was performed at 180 ° C. for 60 minutes to form an electrode terminal portion. The smoothing layer 20 was formed on the entire surface except the varistor element portion.

Examples of the photosensitive polymer film material applicable here include, in addition to the photosensitive acrylic resin, photosensitive epoxy resins, polyimide resins, natural protein resins such as casein and gelatin. However, it may be used properly according to the situation.

Thereafter, an aligning agent (product name: HL1110, manufactured by Hitachi Chemical Co., Ltd.) is applied to both the upper glass substrate 17 and the lower glass substrate 10 to a film thickness of about 700Å, and the rubbing directions are about 90 ° to each other. Rubbing is performed using a roller rubbing device so as to form an angle, and the alignment film 15 is formed. When a photosensitive polyimide resin is used as the material of the smoothing layer 20, it is possible to omit the application of the alignment material to the lower glass substrate 10 and use the smoothing layer 20 as the alignment film 15.

Next, on the upper glass substrate 17, a cell gap holding spacer 19 (made by Nippon Electric Glass,
Product name: Micro rod, product number PF-90, average particle size 9.00 ± 0.05 μm, standard deviation 0.16 μm or less)
An epoxy resin for sealing mixed with is printed by a silk screen printing method to form a sealing portion. At the same time, the gap holding spacers 19 are also scattered in the center of the cell. Furthermore, after accurately aligning the lower glass substrate 10, the cell was uniformly pressed and heated using a pressure jig to cure the sealing material. Pressurized pressure at this time is 1 kg / c
It was carried out at about m ² .

Finally, TN liquid crystal (manufactured by Merck Japan, trade name: ZLI-4472, where Δn = 0.1178) is injected, and polarizing plates 19 are attached to both outer surfaces of the cell to complete a liquid crystal display device.

When the completed liquid crystal display device was evaluated, the accuracy of the cell gap was 11 ± 10 when the conventional method was used.
According to the present invention, it was 8.7 ±.
It was significantly improved to 0.25 μm, that is, the variation was reduced. At the same time, the cell gap value was able to be greatly reduced toward an appropriate thickness as compared with the conventional one. From this, the response speed is 1.67 times faster than the conventional method, and the viewing angle is improved from the conventional left-right 35 ° to 45 °. That is, a liquid crystal display device having a high response speed, a wide viewing angle, and high image quality without display unevenness was obtained.

Example 2 As shown in FIG. 3 (FIG. 3), SiO
_A Cr film as a conductive thin film having a thickness of 1000 Å is formed on the lower glass substrate 10 whose base is soda glass coated with ₂ coats, by using a magnetron sputtering apparatus.
The type of the conductive thin film is not limited to Cr, but Al,
Various metals such as Ta, Ni and Cu and transparent conductive films such as ITO can be used. The sheet resistance at this time was 2Ω / □. A resist pattern is formed on this by a photofabrication method, and the scanning electrode 11 is formed with a cerium ammonium nitrate-based etching solution. At this time, the line width of the scanning electrode 11 was 50 μm.

Next, a transparent conductive film made of ITO was formed using a magnetron sputtering device. At this time, the film thickness is 1000Å and the sheet resistance value of the film is 40Ω / □.
Met. Further, a resist pattern is formed by using the photofabrication method to form the pixel electrode 12. At this time, the varistor gap value D between the scan electrode 11 and the pixel electrode 12 formed previously is 20 μm,
The accuracy was within ± 1 μm.

The threshold voltage of the varistor element 13 is
Since it is determined by the number of varistor particles existing in the varistor gap region, the varistor gap value D controls the threshold value of the device. Therefore, the varistor gap value D is 3 to 100 μm depending on the liquid crystal used and the driving conditions of the liquid crystal display device.
It is set in the range of m. Furthermore, the varistor gap value D
It is necessary to control the range of the dimensional variation of (1) to the particle size of the varistor particles to be used or less in order to suppress the variation of the threshold voltage of the device. In this embodiment, the varistor particle size is about 5 μm, so the accuracy is ± 2.5 μm.
Within m is required.

[0036] Next, ZnO powder as the raw material after firing for 1 hour at 1200 ° C., which was air-classified to form a ZnO single crystal powder having an average grain size of 5μm after pulverized by a ball mill, to which Co ₂ O 0.5 mol% of ₃ and 0.5 mol% of MnCO ₃ were added and fired again at a temperature of 1150 ° C. for 1 hour to obtain a varistor powder having preferable varistor characteristics. To this varistor powder, 25 parts by weight of glass frit and 10 parts by weight of ethyl cellulose (viscosity 50 cps) were added to form carbitol as a solvent into a paste, and this paste was sintered on the lower glass substrate 10 using a silk screen printing method. The pattern of the element 13 is printed. After that, flattening treatment of the element thickness printed by the printing method was performed using a roll press machine. Further, calcination at 460 ℃ for 1 hour,
The sintered body element 13 is completed. At this time, when the thickness of the completed varistor element 13 was measured, the average film thickness was 11.0.
was μm.

Next, on the lower glass substrate 10 on which the varistor element is formed, the visible light region (specifically, wavelengths 400 to 70).
A photosensitive acrylic resin (trade name: FVR manufactured by Fuji Yakuhin Kogyo Co., Ltd.) was applied as a transparent photosensitive polymer film having a thickness of 0 nm). The coating film thickness is the element thickness 11.0 of the varistor element 13.
The difference between μm and the set cell gap value of 8.5 μm is 2.5 μm
Since m is set to 3, m should be set to a value larger than 3.
It was set to 5 μm. Next, after exposing with an ultraviolet lamp through a photomask having a predetermined pattern, development with a FVR developing solution (mixture of methyl ethyl ketone and isopropyl alcohol) and rinsing are performed, and then 180
Post-baking is performed at 60 ° C. for 60 minutes to form a through hole 21 for conduction with the pixel electrode 12 on the varistor element forming portion 22 side in the pixel electrode, and at the same time smooth the entire surface except the electrode terminal portion and the varistor element portion. Layer 20 was formed.

Examples of the photosensitive polymer film material applicable here include, in addition to the photosensitive acrylic resin, photosensitive epoxy resins, polyimide resins, natural protein resins such as casein and gelatin. It is possible to use them properly according to the situation.

Next, a positive photoresist (manufactured by Shipley Far East, trade name: MP1400) is formed on the substrate.
A photoresist pattern for lift-off covering the entire surface of the substrate except the pattern portion of the pixel electrode was formed by a photolithography method using. Further, a transparent conductive film made of ITO was formed to a thickness of 1000Å using a magnetron sputtering device. At this time, the sheet resistance value of the transparent conductive film was 80 Ω / □. Further, this substrate was dipped in a remover for removing photoresist (manufactured by Shipley Far East, trade name: MP remover 140) to remove the photoresist and simultaneously form the pixel electrode portion 12.

Then, an aligning agent (Hitachi Chemical Co., Ltd., trade name: HL1110) is applied to both the upper glass substrate 17 and the lower glass substrate 10 in a film thickness of about 700Å, and the rubbing directions are about 90 ° to each other. Rubbing is performed using a roller rubbing device so as to form an angle, and the alignment film 15 is formed.

Next, on the upper glass substrate 17, a cell gap holding spacer 19 (made by Nippon Electric Glass,
Product name: Micro rod. An epoxy resin for sealing containing a product number PF-90, an average particle size of 9.00 ± 0.05 μm, and a standard deviation of 0.16 μm or less) is provided as a predetermined pattern by a silk screen printing method to form a seal portion. At the same time, the gap holding spacers 19 are also scattered in the center of the cell. Furthermore, after accurately aligning the lower glass substrate 10, the cell was uniformly pressed and heated using a pressure jig to cure the sealing material. The pressure applied at this time was about 1 kg / cm ² .

Finally, TN liquid crystal (manufactured by Merck Japan, trade name: ZLI-4472, Δn = 0.1178) was injected, and polarizing plates 19 were attached to both outer surfaces of the cell to complete a liquid crystal display device.

When the completed liquid crystal display device was evaluated, the accuracy of the cell gap value was 11 according to the conventional one.
According to the present invention, it was 8.7 ±.
It was significantly improved to 0.25 μm, that is, the variation was reduced. At the same time, the cell gap value was able to be greatly reduced toward an appropriate thickness as compared with the conventional one. From this, the response speed was 1.67 times faster than the conventional method, and the viewing angle was improved from 45 ° in the conventional method to 45 ° in the left and right. Further, since the effective voltage applied to the liquid crystal is increased, the contrast of the liquid crystal display device is improved from 40: 1 to 50: 1. That is, a liquid crystal display device having a high response speed, a wide viewing angle, and high image quality without display unevenness was obtained.

[0044]

According to the liquid crystal display device of the present invention,
Since the smooth layer that is transparent in the visible light region is provided as described above, the cell gap value can be reduced by using it together with a highly accurate (for example, commercially available predetermined cell gap value) cell gap holding spacer. It is possible to easily provide an appropriate thin value with high accuracy. Furthermore, by providing the pixel electrode on the smoothing layer, the drop of the voltage applied to the liquid crystal can be reduced, and the pixel electrode can be provided in the varistor formation part. When forming a structure in which the varistor formation portion side is formed with the scanning electrodes, it is possible to reduce variations in the varistor gap when forming a structure in which the varistor formation portion side is formed together with the scanning electrodes. Can be obtained. From these things, it was possible to provide a liquid crystal display device which has high image quality, a high response speed, a wide viewing angle, no display unevenness, and can be easily manufactured.

[0045]

[Brief description of drawings]

FIG. 1 is an explanatory view showing a sectional view of an embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is an explanatory diagram showing a plan view of one embodiment of the liquid crystal display device according to the present invention.

FIG. 3 is an explanatory view showing a sectional view of another embodiment of the liquid crystal display device according to the present invention.

FIG. 4 is an explanatory view showing a plan view of another embodiment of the liquid crystal display device according to the present invention.

FIG. 5 is an explanatory view showing an enlarged main part of a varistor element in a normal embodiment of a liquid crystal display device according to the present invention.

FIG. 6 is an explanatory view showing a cross section of varistor particles in a normal example of the liquid crystal display device according to the present invention.

FIG. 7 is an explanatory diagram showing an equivalent circuit diagram of a normal embodiment of a liquid crystal display device according to the present invention.

FIG. 8 is an explanatory view showing a varistor element part in a normal embodiment of the liquid crystal display device according to the present invention.

FIG. 9 is a graph showing a voltage-current characteristic of a varistor element in a normal example of a liquid crystal display device according to the present invention.

FIG. 10 is an explanatory diagram showing an example of a conventional liquid crystal display device using a cross-sectional view (portion AA in FIG. 11).

FIG. 11 is an explanatory diagram showing an example of a conventional liquid crystal display device using a plan view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Signal electrode group 2 ... Scanning electrode group 3 ... Varistor element 4 ... Liquid crystal 10 ... Lower glass substrate 11 ... Scanning electrode 12 ... Pixel electrode 13 ... Varistor Element 13a ... Varistor particle 13b ... Glass frit 14 ... Liquid crystal 15 ... Alignment film 16 ... Signal electrode 17 ... Upper glass substrate 18 ... Polarizing plate 19 ... Gap holding Spacer 20 ... Smoothing layer 21 ... Pixel electrode (through hole part) 22 ... Varistor element formation part side (pixel electrode) 131 ... ZnO single crystal particle 132 ... Inorganic insulating film d ... Cell gap D ... Varistor gap

Claims (5)

[Claims] 1. A varistor element is formed as an active matrix element in a structure for connecting a scanning electrode and a pixel electrode on a lower glass substrate, and a liquid crystal layer is opposed to an upper glass substrate and the lower glass substrate. In a liquid crystal display device provided between the glass substrate and driven via the varistor element, a smooth layer transparent at least in the visible region excludes the varistor element portion and the electrode terminal portion of the lower glass substrate. A liquid crystal display device, wherein the thickness of the smooth layer provided over the entire surface and transparent in the visible region is in a range of a difference between the thickness of the varistor element and a predetermined cell gap value. 2. A varistor element is formed as an active matrix element in a structure for connecting a scanning electrode and a pixel electrode on a lower glass substrate, and a liquid crystal layer is opposed to an upper glass substrate and the lower side. In a liquid crystal display device provided between the glass substrate and driven through the varistor element, the pixel electrode portion is divided in an electrically connected state, and at least a transparent smooth layer in the visible region is provided. The thickness of the smooth layer, which is provided on the entire surface of the lower glass substrate except for a part of the electrode terminal portion and the varistor element portion and is transparent in the visible region, is equal to the thickness of the varistor element and the predetermined cell gap value. A liquid crystal display device, wherein the liquid crystal display device has a difference or more and a part of the pixel electrode is provided on the smoothing layer. 3. The liquid crystal display device according to claim 2, wherein a portion of the pixel electrode to which the varistor element portion is connected is made of the same material as that of the scanning electrode.
The described liquid crystal display device. 4. The material of the smooth layer transparent in at least the visible region is a photosensitive polymer.
4. The liquid crystal display device according to any one of 3 to 3. 5. The liquid crystal display device according to claim 1, wherein the material of the smooth layer which is transparent in at least the visible region is one containing SiO ₂ as a main component.