JPH0488321A - Active matrix substrate for liquid crystal display device - Google Patents

Abstract

PURPOSE:To allow the accurate printing of varistor elements and to obtain desired element characteristics by providing picture element electrodes and lead parts conducting to row electrodes of ITO and providing the varistor elements formed by a printing method between the picture element electrodes and the lead parts. CONSTITUTION:The picture element electrodes 12 and the lead parts 14 conducting to the row electrodes 11 are provided of the ITO and the varistor elements 3 formed by the printing method are provided between the picture element electrodes 12 and the lead parts 14. Then, the picture element electrodes 12 and the lead parts 14 conducting to the row electrodes 11 are provided of the ITO and, therefore, the wettability (contact angle of varistor ink and the ITO is about 4 deg.) of the parts where the varistor ink is printed is better than in the case of direct printing of the varistor ink on the row electrodes 11. Since the varistor elements are easily printable to desired shapes in this way, the desired element characteristics are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix substrate for a two-terminal element type liquid crystal display device (LCD) using a sintered varistor element as a nonlinear element.

[Prior 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 due to crosstalk occurring in each LCD pixel, the pixel contrast is low, resulting in a decrease in image quality when displaying images on an LCD TV. was inevitable.

On the other hand, in the active matrix method, a switch 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 can maintain the voltage at the time of selection. , it is possible to increase the display capacity,
It has good image quality characteristics such as contrast, and can realize high-quality image display on liquid crystal televisions.

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, it is difficult to increase the product yield because five or more photomasks are used in the manufacturing process to stack five or more thin film layers.

For the reasons mentioned above, 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 cost.As a method to achieve these requirements, a method using varistor elements is proposed. Two-terminal element type liquid crystal display devices 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. and a varistor element 3 that conducts at a predetermined threshold voltage.
The varistor element 3 is electrically connected in series and utilizes the nonlinear current-voltage characteristics of the varistor element 3 as shown in FIG.

In other words, in time-division driving using the simple matrix method, as shown in FIG.
%) Voltage ■,. The ratio γ (=■, ./V,

-(■1°+ΔV)/V,. ), the maximum allowable number of scanning lines Nwax without causing crosstalk between each liquid crystal pixel is Nmax-((T”+1)/(γ
"-1))", and the smaller the value of T, the greater the number of scanning lines, which is advantageous for liquid crystal television display.

On the other hand, in the two-terminal element type, the varistor element 3 applies a voltage equal to the threshold voltage Vv to the liquid crystal pixel 4, so that the operating voltage of the liquid crystal pixel when the varistor element is not provided is (see FIG. 10(a)) is increased by its threshold voltage Vv by providing a varistor element (see FIG. 10(b)). As a result, the T
The value of is ■,. /■1° to (Vv +V,.)/(Vv
＋'／＋. ), the maximum number of scanning lines N5ax can be increased by decreasing the γ value, and a high-quality liquid crystal display can be realized.

3 to 6 show a general two-terminal element type active matrix substrate for a liquid crystal display device.

Regarding liquid crystal pixels, as shown in FIGS. 3 and 4, a column electrode 11 and a pixel electrode 12 are provided on a lower glass substrate 10 with a predetermined distance d, and these column electrodes 11
and the pixel electrode 12 are connected by a varistor element made of zinc oxide (ZnO).

As shown in FIG. 6, the varistor element 13 is made of varistor particles 13 in which the surface of ZnO single crystal particles 131 having a predetermined particle size is coated with an inorganic insulating film 132 such as Mn or CoN compound.
As shown in FIG. 5, these varistor particles 13a are sintered with a glass frit 13b. In such a varistor element 13, the particle diameter is 5.
A threshold voltage of approximately 3 V per am varistor particle is obtained. Therefore, if the distance d between the column electrode 11 and the pixel electrode 12 is set to 25 μm, the column electrode 11 and the pixel electrode 12 will be connected through the five varistor grains 13a existing in series within this distance d. and these electrodes 11.1
A threshold voltage of 5 x 3V-15V is obtained between the two.

Next, an example of a general method for manufacturing the varistor element 13 will be described. After heating and sintering fine powder of zinc oxide to polycrystallize it, the sintered body is crushed and classified to obtain a zinc oxide single crystal particle powder, and the zinc oxide single crystal particle is heat-treated to be rounded. After that, the surface of the zinc oxide single crystal particles is coated with an inorganic insulating film such as an Mn or Co oxide insulating film to form a varistor particle powder, and a glass frit is added to the varistor particle powder.
It is obtained by adding an organic binder such as ethyl cellulose, making a paste using calpitol as a solvent, printing the paste on an insulating substrate, and then baking it.

Further, since the column electrode material of this substrate is required to have low resistance due to the large area, generally a metal material such as Cr having a low resistance value is used.

[Problem to be solved by the invention]

In the conventional actite matrix substrate using varistor elements, varistor elements are printed between column electrodes made of metal such as Cr and pixel electrodes made of transparent conductive film such as ITO (indium-tin-oxide). be.

However, due to poor wettability between the varistor ink and the metal material such as Cr that constitutes the column electrodes (the contact angle between the varistor ink and Cr is approximately 10 degrees), the desired shape of the varistor element cannot be printed. There was a problem that the device characteristics of - could not be obtained.

In view of the above-mentioned problems, the present invention has been made for the purpose of providing an active matrix substrate for a liquid crystal display device that can obtain desired element characteristics by printing varistor elements with high precision.

[Means for Solving the Problems] That is, the present invention provides an active matrix substrate for a liquid crystal display device using a varistor element as a nonlinear element, in which a pixel electrode and a lead portion electrically connected to a column electrode are made of ITO.
The above problem was solved by providing a varistor element which was provided by a printing method between the pixel electrode and the lead portion.

[Effect]

Since the pixel electrode and the lead part that conducts to the column electrode are provided with ITo, the part where the varistain marking is printed (
wettability (pixel electrode and lead part) (varistain adhesive and IT
The contact angle with O (approximately 4 degrees) is better than printing the barista ink directly on the column electrodes. Therefore, it is easy to print the varistor element in a desired shape.

〔Example〕

Embodiments of the present invention will be described in detail using the drawings. FIG. 1 is a plan view showing an active matrix substrate for a liquid crystal display device according to the present invention, and FIG. 2 is a sectional view taken along line AA' in FIG. After forming a Cr film on the glass substrate 10 by sputtering 1,500 people, etching is performed to form the column electrodes 11.
patterned.

Next, 1,500 pieces of ITO were sputtered and patterned to form lead portions 14 on the pixel electrodes 12 and column electrodes made of Cr.

Next, a ballistic pattern was printed between the pixel electrode and the lead portion using a screen printing method. The ballista ink used here was made by adding 25% by weight of glass frit and 10% by weight of ethyl cellulose to barista grains having a particle size of about 5 μm, and using calpitol as a solvent to form an ink.

Thereafter, the glass substrate was fired to form a sintered ZnO varistor element 13, thereby completing an active matrix substrate for a liquid crystal display.

〔Effect of the invention〕

In the active matrix substrate for liquid crystal display according to the present invention, the pixel electrode on which the varistor element is printed and the lead part that is electrically connected to the column electrode are provided with ITO. It is easy to print in a shape, so desired device characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an active matrix substrate for a liquid crystal display device according to the present invention, FIG. 2 is a cross-sectional view taken along line AA' in FIG. 1, and FIG. 3 is an active matrix substrate for a liquid crystal display device according to a conventional method. FIG. 4 is a sectional view taken along the line BB' in FIG. 3, FIG. 5 is an enlarged sectional view of the main part in FIG. 4, FIG. 7
The figure is a schematic configuration diagram of a two-terminal element type liquid crystal display device, Figure 8 is a voltage-current characteristic diagram of a varistor element, Figure 9 is an electro-optical characteristic diagram of a liquid crystal display device, and Figures 1O (a) and (b). FIG. 2 is an operational characteristic diagram of a liquid crystal pixel explaining the action of a varistor element. 1... Row electrode 2... Column electrode 3... Varistor element 4... Liquid crystal pixel 10... Glass substrate 11... Column electrode 12... Pixel electrode 13... Varistor element 13a. ...Varistor particles 13b...Glass lift 14...Lead portion 131...ZnO single crystal particles 132...Inorganic insulating film patent application Toppan Printing Co., Ltd. Representative Kazuo Suzuki Figure 1 Electric diagram diagram diagram diagram diagram diagram diagram

Claims (1)

[Claims] (1) An active matrix substrate for a liquid crystal display device using a varistor element as a nonlinear element, in which a pixel electrode and a lead part that conducts to a column electrode are provided with ITO, and printing is performed between the pixel electrode and the lead part. An active matrix substrate for a liquid crystal display device, characterized in that it is provided with a varistor element formed by a method.