JPH04328802A - Manufacture of sintered body varistor element substrate - Google Patents

Abstract

PURPOSE:To provide a method with which a varistor element substrate, having the correct position on the substrate, excellent shape, high quality being constant in each element. CONSTITUTION:The mixture of varistor particles and glass frit made into a suspension in advance is applied to a substrate using a doctor blade, a sping coater and the like, a patterning operation is conducted using a photolithographic method, then a calcination is performed, and a sintered varistor element 13 is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sintered varistor element substrate suitable for use as a nonlinear element in, for example, a two-terminal element type liquid crystal display device.

0002

2. Description of the Related Art Currently, image display devices for, for example, liquid crystal televisions are broadly classified into simple matrix type and active matrix type. In the simple matrix method, a plurality of liquid crystal pixels are arranged in a matrix and connected between a pair of band-shaped electrode groups (row electrode group and column electrode group) arranged at right angles. A predetermined voltage is applied by a drive circuit to operate the liquid crystal pixels. This method has the advantage of being able to realize a system at a low cost due to its simple structure, but crosstalk occurs in each LCD pixel, resulting in low pixel contrast and resulting in poor image quality when displaying images on an LCD TV. The decline was inevitable.

On the other hand, in the active matrix method, a switching element is provided for each liquid crystal pixel to maintain the voltage, and even if the liquid crystal display device is time-divisionally driven, the liquid crystal pixel maintains the voltage at the time of selection. Therefore, the display capacity can be increased, and characteristics related to image quality such as contrast are good, and high-quality display on liquid crystal televisions can be realized. However, the active matrix method has the disadvantage that the structure is complicated and the manufacturing cost is high. For example, in a TFT type device that uses a thin film transistor as a switching element, five or more layers of thin films are stacked in the manufacturing process, making it difficult to increase the product yield.

[0004] For the above reasons, there is a desire to realize a liquid crystal display device that has good image quality characteristics such as contrast, has a simple structure, and is low in cost. Two-terminal element type liquid crystal display devices using sintered varistor elements are attracting attention.

The two-terminal element type liquid crystal display device is an improvement on the simple matrix method, and as shown in FIG. The sintered varistor element 13 is electrically connected in series with the sintered varistor element 13, which conducts at .

FIG. 3 shows a general two-terminal element type liquid crystal display device. As shown here, a large number of pixel electrodes 12 are provided for each of the row electrodes 11 at a constant interval d, and the row electrodes 11 and the pixel electrodes 12 have a constant threshold value in each sintered body varistor element 13. It is connected with voltage VV. As shown in detail in FIG. 5, the sintered varistor element 13 includes varistor particles 13a in which the surface of a ZnO single crystal particle 131 is coated with an inorganic insulating film 132 such as Mn or Co oxide.
As shown in detail in FIG. 4, these varistor particles 13a are sintered with a glass frit 13b. For this reason, sintered varistor element substrates are usually made by adding glass frit and an organic binder to varistor particles to form a paste, creating a varistor stamp, and printing this onto a glass substrate with electrodes using a printing method such as screen printing. , and is then fired and formed.

[0007]

[Problem to be solved by the invention] In particular, two
In order to realize a terminal element type liquid crystal display device, sintered varistor elements must have high performance and stability, and the performance must be constant between elements. Further, the distance between the upper glass substrate and the lower glass substrate is required to be uniform over the entire surface. However, for example, when varistor particles are made into ink and elements are printed by screen printing, the essential problems of screen printing are plate elongation and distortion, which causes printing position shifts. In addition, changes in ink viscosity during printing,
Changes in printing conditions due to squeegee wear, etc.
It greatly affects the thickness etc. Therefore, the positional deviation of the varistor element on the substrate and the variation in thickness are large. This causes variations in electrical characteristics between varistor elements. For this reason, it is difficult to manufacture a liquid crystal display device with good characteristics regarding image quality such as contrast.

The present invention provides a varistor element substrate in which each varistor element is accurately positioned on the substrate, has small variations in thickness, can be manufactured into a good shape, and has high performance and whose performance is constant between elements. The purpose is to make it easy to manufacture.

[0009]

[Means for Solving the Problems] The present invention has been made in view of the above problems, and provides a method for manufacturing a sintered varistor element substrate, in which at least varistor particles, glass frit, and photosensitive resin are mixed. The problem was solved by forming a varistor particle layer by applying a suspension of the above on a substrate, patterning the varistor particle layer by photolithography, and firing it to form a sintered varistor element.

0010

[Operation] In the present invention, a suspension formed by mixing at least varistor particles, a glass frit, and a photosensitive resin is applied onto a substrate using a doctor blade, a spin coater, etc. to form a varistor particle layer. Since patterning is performed by photolithography, the position and shape of the sintered varistor element are determined by the original plate such as the film used in the photolithography method, resulting in good reproducibility.
High positional accuracy can be obtained. Further, the thickness of the sintered varistor element is determined by the thickness when applying the suspension (thickness of the varistor particle layer), so there is little variation.

As described above, since the position of the varistor element on the substrate is accurate, the variation in thickness is small, and the shape is good, it is possible to obtain a varistor element substrate with high performance and whose performance is constant between elements. make it easier.

In a specific example of the present invention, a suspension is prepared by adding at least varistor particles, glass frit, and a photosensitive resin made of polyvinyl alcohol or the like in advance.

The varistor particles are ZnO single crystal particles whose surfaces are coated with an inorganic insulating film of Mn, Co oxide, etc., and have a diameter of 1 to 10 μm. Since the glass frit must be melted during firing, it is preferable that the glass frit has a melting point of 350°C to 400°C. The photosensitive resin is preferably one that burns during firing, for example,
Examples include those made of polyvinyl alcohol and ammonium dichromate. The photosensitive resin has good workability since water can be used as a solvent.

The composition of the suspension is, for example, 10 to 40 parts by weight of varistor particles and 2 to 1 part by weight of glass frit.
5 parts of the photosensitive resin, 5 parts to 40 parts of the photosensitive resin, and 2 parts to 75 parts of the solvent.

[0015] The suspension is applied onto a substrate to a thickness of about 1 μm to 25 μm using a coating method such as a doctor blade or a spin coater, and then dried or semi-dried to form a layer of varistor particles. A sintered varistor element is formed by closely contacting an original plate such as a film having a transparent part in the shape of the element, exposing it to light, developing it (photolithography method) to pattern it, and then baking it at about 400°C for about 30 minutes to 2 hours. A substrate can be manufactured.

[0016] The above explanation is an example in which a negative-working photosensitive resin (the part exposed to light becomes insoluble in the developer), but a positive-working photosensitive resin (the part exposed to light becomes insoluble in the developing solution) is used. If solubilization) is used, it is necessary to use an original plate at the time of exposure that has a plurality of varistor element-shaped light shielding parts.

[0017]

[Example] The present invention will be explained in detail based on an example. 1 and 2 are process diagrams of a manufacturing method according to an embodiment of the present invention.

[Example 1] First, a varistor suspension is prepared. The varistor particles used here had ZnO as a main component and had a diameter of 1 to 2 μm. To 20 parts of varistor particles, 5 parts of glass frit, 20 parts of polyvinyl alcohol and 2 parts of ammonium dichromate as a photosensitive resin, and 40 parts of pure water as a solvent were added.
A suspension was prepared by mixing.

The row electrode 1 is coated using a spin coater.
1 and a pixel electrode 12 (hereinafter referred to as a substrate), the coating was applied to a thickness of 4 μm.
It was dried to form a varistor particle layer 15 (see FIG. 1).
.

A film original plate having a plurality of varistor element-shaped transparent parts in the varistor particle layer was exposed in close contact and patterned by spray development with warm pure water.

[0021] This substrate was fired by heating at 420°C for 1 hour. As a result, each sintered varistor element 13 was formed at the desired position, and a sintered varistor element substrate with little variation in thickness and good shape was obtained (see FIG. 2).

[Example 2] First, a barista suspension is prepared. The varistor particles used here had ZnO as a main component and had a diameter of 5 to 10 μm. To 15 parts of the varistor particles, 5 parts of glass frit, 10 parts of polyvinyl alcohol and 1 part of ammonium dichromate as a photosensitive resin, and 40 parts of pure water as a solvent were added and mixed to prepare a suspension.

[0023] Spread this onto the substrate using a doctor blade.
It was applied to a thickness of 5 μm and dried to form a varistor particle layer.

A film original plate having a plurality of varistor element-shaped transparent parts in the varistor particle layer was exposed in close contact and patterned by spray development with warm pure water.

[0025] This substrate was fired by heating at 420°C for 1 hour. As a result, each sintered varistor element was formed at the desired position, and a sintered varistor element substrate with little variation in thickness and good shape was obtained.

[0026]

According to the method of manufacturing a sintered varistor element substrate of the present invention, each sintered varistor element can be formed at a desired position, and the sintered varistor element has a good element shape with little variation in thickness. A substrate can be obtained. This makes it easy to obtain a varistor element substrate with high performance and whose performance is constant between elements, and it becomes possible to obtain a large-screen liquid crystal display device that achieves uniform and clear image display.

[0027]

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing, in order of steps, an embodiment of a method for manufacturing a sintered varistor element substrate of the present invention.

FIG. 2 is a cross-sectional view showing an embodiment of the method for manufacturing a sintered varistor element substrate of the present invention in the order of steps.

FIG. 3 is a plan view showing an example of a general two-terminal element type liquid crystal display device.

FIG. 4 is an enlarged view of a main part of a varistor element.

FIG. 5 is a cross-sectional view of a varistor particle.

FIG. 6 is an equivalent circuit diagram of a two-terminal element type liquid crystal display device.

FIG. 7 is a graph diagram showing voltage-current characteristics of a sintered varistor element.

[Explanation of symbols]

10 Glass substrate 11 Row electrode 12 Pixel electrode 13 Sintered varistor element 13a Varistor particles 13b Glass frit 131 ZnO single crystal particles 132 Inorganic insulation film 14 Liquid crystal 15 Varistor particle layer 16 Column electrode

Claims (1)

[Claims] 1. A method for manufacturing a sintered varistor element substrate, in which a suspension formed by mixing at least varistor particles, glass frit, and a photosensitive resin is applied onto a substrate to form a varistor particle layer; 1. A method for manufacturing a sintered varistor element substrate, comprising forming a sintered varistor element by patterning a varistor particle layer by photolithography and firing.