JPH02284121A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To decrease the fluctuation in the varistor threshold voltage between respec tive picture element electrodes and signal electrodes and to uniformize the contrast of the respective picture elements by increasing the coating area of the varistors connecting the picture element electrodes and the signal electrodes. CONSTITUTION:The signal electrodes 4 are disposed on a 1st substrate 2 so as to have projecting parts 4a to be inserted by having a spacing between the picture element electrodes 3. The varistors 5 to connect the picture element electrodes 3 and the signal electrodes 4 are disposed by utilizing the projecting parts 4a. The varistors 5 are so applied that at least 50% of the length on the end side of the projecting parts 4a of the picture element electrodes 4 and the signal electrodes 4 are covered. On the other hand, scanning electrodes 7 are disposed on a 2nd substrate 6 and a polymer dispersion type liquid crystal layer 8 is held by the substrates 2 and 6. These substrates are so disposed that the electrode surfaces face each other and the varistors 5 and the scanning electrodes 7 do not overlap on each other. The fluctuation in the varistore threshold voltage between the respective picture element electrodes and the signal electrodes is decreased in this way and the contrast of the respective picture elements is uniformized, by which crosstalks are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid crystal display device using a polymer-dispersed liquid crystal with almost no crosstalk and high brightness.

[Prior art and its problems]

Liquid crystal display devices are thin, can be driven at low voltages, have low power consumption, and can be driven directly by ICs, so they have the advantage that they can be easily made small and thin. In particular, TN type liquid crystals are excellent in terms of low voltage and low power consumption, and have been widely used in wristwatches, calculators, and the like.

In recent years, with the spread of information processing devices such as word processors and personal computers, there has been a demand for portable, thin, and compact devices, and liquid crystal display devices have begun to be adopted as display devices in place of CRTs. In this case, in order to display kanji characters, the number of pixels is much larger than that used in wristwatches, calculators, etc., and the driving method for the liquid crystal display device is usually a simple matrix drive circuit in which electrodes cross in an X-Y pattern. However, in this case, since each pixel has an independent pixel electrode, a constant voltage is also applied to adjacent pixels, and the adjacent pixels are not completely hidden, resulting in a so-called cross Talk may occur.

In order to improve this crosstalk, there is a method of providing a nonlinear element such as a diode or a thin film transistor for each pixel.

However, it is difficult to arrange diodes, thin film transistors, etc. for each pixel, which number from several thousand to hundreds of thousands of pixels, without defects or with characteristics between the lines.There is little variation in characteristics and it can be formed over a large area. It has been desired to create a nonlinear element with

On the other hand, the development of liquid crystals used in large-area display devices has progressed, and in recent years, N CA P (Nematic Curv
A new liquid crystal technology called polymer-dispersed liquid crystals has been developed, including liquid crystals (ilinear aligned phase), liquid crystals dispersed in thermoplastic resins, and liquid crystals dispersed in polymers such as epoxy resins. It is a relatively large-area display device because it has characteristics such as easy control of the thickness of the liquid crystal layer, allowing for a large area, fast response time, no need for a polarizing plate, and wide viewing angle. It is expected that it will be suitably used in

However, while the operating voltage of the TN type liquid crystal is about 5V, the operating voltage of the above-mentioned polymer-dispersed liquid crystal is high, on the order of tens to hundreds of V, and as a nonlinear element, it has a higher withstand voltage than thin film elements etc. Motoko was desired.

The applicant filed a patent application for a liquid crystal display device using a film mainly made of varistor powder as a nonlinear element in Japanese patent application No. 63-1388.
I proposed it as No. 70. According to the liquid crystal display device proposed above, even when a polymer-dispersed liquid crystal having a high operating voltage is used as the liquid crystal, display with almost no crosstalk can be performed.

However, in the conventional example shown in FIG.
As the size of a pixel becomes smaller and the width of the varistor connecting the pixel electrode and the signal electrode becomes narrower, the variation in the varistor dark value voltage between each pixel electrode and the signal electrode becomes larger, and the contrast of each pixel becomes smaller. There were cases where it was uneven.

An object of the present invention is to provide a high-brightness, crosstalk-free liquid crystal display device that solves these problems.

[Means for solving problems]

The liquid crystal display device of the present invention includes a first substrate including a pixel electrode, a signal electrode disposed at a distance from the pixel electrode and sending a signal to the pixel electrode, and a varistor connecting the pixel electrode and the signal electrode. , an active matrix type liquid crystal display device comprising: a second substrate provided with an electrode to face the pixel electrode; and a polymer dispersed liquid crystal layer filled between the first substrate and the second substrate. The present invention relates to a liquid crystal display device characterized in that a varistor is coated so as to cover 50% of the edge of a pixel electrode and a signal electrode.

Particularly when the pixel size is as small as several centimeters, it is preferable that the varistor be applied so as to cover at least 80% of the length of the edge of the pixel electrode and the signal electrode.

The polymer-dispersed liquid crystal of the present invention includes N CA P in which small spheres of liquid crystal are dispersed in a polymer matrix.
(Nea+atic Curvilinear Ali
gned Phase (nematic curve aligned phase) liquid crystal, liquid crystal dispersed in thermoplastic resin, liquid crystal dispersed in polymer such as epoxy resin, or so-called polymer-dispersed liquid crystal, such as liquid crystal dispersed in a polymer such as epoxy resin, or a polymer with a three-dimensional network structure. Examples include liquid crystal filled in the communication hole.

The liquid crystal used in the present invention is not particularly limited, and suitable examples include nematic liquid crystal, smectic liquid crystal, and the like.

In addition, the polymers used as a medium in the present invention include:
Not limited in particular, polystyrene, polyvinyl chloride, polyvinyl alcohol, polycarbonate, butadiene rubber, polymethyl methacrylate, polybutyl methacrylate, polyvinyl pyrrolidone, ethyl cellulose, cyanoethyl cellulose, polyvinylidene fluoride, NBR (tolyl rubber), polysulfide rubber (thiokol), etc. can be preferably mentioned.

A known varistor can be used to form the varistor film. A composite oxide of indium and tin is conveniently used as the material for the transparent pixel electrode, signal electrode, and scanning electrode.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a partial vertical sectional view of an embodiment of an active matrix type liquid crystal display device 1 of the present invention. A transparent pixel electrode 3 and a signal electrode 4 are formed on the first substrate 2 by a known method such as patterning, and a varistor film 5 that connects the picture electrodes is formed by a known method such as screen printing. There is.

On the other hand, a scanning electrode 7 is disposed on the second substrate 6, and a polymer-dispersed liquid crystal layer 8 is sandwiched between the substrates 2 and 6 so that the electrode surfaces thereof face each other.

FIG. 2 is a partially enlarged perspective view of one embodiment showing the arrangement relationship of these components on the first substrate 2. FIG. As shown in the figure, the signal electrode 4 is disposed on the substrate 2 so as to have a protrusion 4a that is inserted between the pixel electrodes 3 at intervals, and the protrusion 4a is used to connect the pixel electrodes 3 to 3. A varistor 5 is provided to connect the signal electrode 4 and the signal electrode 4 .

FIG. 3 shows the pixel electrode 3, the signal electrode 4° 4a, the varistor 5 (the varistor part is shaded in the figure), when the first substrate and the second substrate shown in FIG. 2 are overlapped. Scanning electrode 7 (
FIG. 3 is a perspective plan view showing the arrangement relationship of the components (indicated by dotted lines in the figure). If the varistor and the scanning electrode overlap, crosstalk may occur, so it is desirable to arrange the varistor and the signal electrode so that they do not overlap, as shown in FIG.

FIG. 4 is a diagram showing the arrangement of electrodes and the like when the varistor 5 is applied in a linear manner instead of in a dotted manner as shown in FIG. 3. FIG.

FIG. 5 is a diagram showing another embodiment of the present invention, in which a varistor is applied to cover the pixel electrode and the signal electrode using both end surfaces of the pixel electrode.

FIG. 6 is a diagram showing another embodiment M of the present invention, in which the signal electrode 4 disposed on the first substrate has a bent portion 4b disposed at a distance between the pixel electrodes 3. A varistor 5 is provided that connects the pixel electrode 3 and the signal electrode 4 using the bent portion 4b.

FIG. 7 is a diagram showing another embodiment of the present invention.

The active matrix type liquid crystal display panel of the present invention can be manufactured using a known polymer-dispersed liquid crystal, for example, by the following method.

First, on the substrate 2, there is a pixel electrode 3 and a protrusion 4a that is disposed at a distance from the pixel electrode 3 and sends a signal to the pixel electrode 3.
A substrate (glass, PE
(T film, etc.) 2 is prepared. The electrodes can be easily provided on the substrate by a patterning method using ITO or the like.

Next, a paste containing a mixture of varistor powder, glass powder, and a binder is applied onto the substrate 2 by a printing method so that the pixel electrode 3 and the signal electrode 4 are connected to each other, and then heat-treated to form a paste on which the varistor film 5 is disposed. A substrate 2 of No. 1 is manufactured.

On the other hand, a polymer-dispersed liquid crystal layer is interposed between a transparent electrode-equipped substrate 6 (glass, PET film, etc.) on which predetermined scanning electrodes 7 have been patterned using ITO or the like, and the substrate 2 on which the pixel electrodes 3 are disposed. The liquid crystal display device of the present invention can be manufactured by forming the above.

〔Example〕

The present invention will be explained in more detail with reference to production examples below.

Manufacturing Example 1 An active matrix liquid crystal display device 1 was manufactured by the following method.

A paste was obtained by thoroughly mixing 10 g of barista powder, several grams of glass powder, several grams of binder, and several grams of solvent.

In advance, according to the usual method, the pixel electrode 2 and the protruding signal electrode 4a (distance between both electrodes 100 μm) and the number of pixels 400 (pixel size 5 ym) are formed using ITO or the like as shown in FIG.
The paste was printed through a predetermined screen onto a glass substrate with a transparent electrode patterned with X 5 rtrts, 1 pixel electrode spacing). The substrate 2 on which the varistor film 5 was disposed was fabricated by heat treatment at 300 to 500°C.

The varistor ON voltage was measured, and the variation in the varistor voltage was measured. The varistor ON voltage was 135v, and the standard deviation was 3.1v.

Next, 100 g of liquid crystal in which epoxy monomer, curing agent (total 30 g), and dichroic dye 3 g are dissolved (mixed) is applied onto the substrate 2 on which the varistor film 5 is disposed using a doctor blade. (thickness: 17 μm).Next, the substrate 6 with transparent electrodes (glass, PET film, etc.) on which a predetermined scanning electrode 7 was patterned in advance using ITO or the like and the substrate 2 on which the varistor film 5 was arranged were placed at a predetermined position. After bonding the substrates so that they fit together, the substrates were left to stand for 24 hours at room temperature.Then, the electrodes on the substrate and the lead wires were connected by soldering.

A drive circuit drive circuit was connected from the electrode lead wire extraction portion of the liquid crystal display panel 1 manufactured by the above method via a flexible printed wiring board. This liquid crystal display device is ±1
Active matrix drive at 80V (duty ratio 1)
/128), a clear display with a contrast ratio of 10 or more was obtained, and no variation in contrado of each pixel was observed.

On the other hand, as shown in FIG. 8, a substrate 2 with 400 pixels on which a varistor film connecting a pixel electrode 2 and a signal electrode 4 (distance between both electrodes 100 μm) is disposed, which is a conventional example, was created.
The varistor ON voltage was measured, and the variation in the varistor voltage was measured. The varistor ON voltage was 143v, and the standard deviation was as large as 9.5v.

According to this method, a large-screen liquid crystal display device using an active matrix drive method using nonlinear elements can be easily obtained, and since it has stable characteristics with little variation in film thickness, there is no difference in brightness between each panel. (It can be used as a large screen display device. Also, the varistor film is printed only between the pixel electrode and the scanning electrode instead of the entire substrate as in the conventional case.
By performing printing, transmissive display, which was previously impossible, can also be performed. In the above description, the signal electrode 4 and the scanning electrode 7 have been specifically explained, but the signal electrode may be used as the scanning electrode, and the scanning electrode may be driven as the signal electrode.

〔Effect of the invention〕

According to the present invention, when the size of one pixel becomes smaller and the width of the varistor connecting the pixel electrode and the signal electrode becomes narrower, by increasing the coating area of the varistor,
It is possible to provide a liquid crystal display device with small variations in varistor dark value voltage between each pixel electrode and a signal electrode, uniform contrast between each pixel, high brightness, and no crosstalk.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an active matrix driven liquid crystal display device of the present invention, and FIG. 2 is a partially enlarged perspective view showing the arrangement relationship of signal electrodes, pixel electrodes, and varistor films on a substrate in the liquid crystal display device. It is a diagram. 3 to 7 are plan views showing the arrangement relationship of signal electrodes, pixel electrodes, varistor films, and scanning electrodes on a substrate in a liquid crystal display device of the present invention. FIG. 8 is a plan view showing the arrangement relationship of signal electrodes, pixel electrodes, and varistor films on a substrate in a conventional liquid crystal display device. 1: Liquid crystal display device, 2.6 two substrates, 3: Pixel electrode, 4.
4a: Signal electrode, 5: Varistor film, 7: Scanning electrode, 8:
Polymer-dispersed liquid crystal layer patent applicant: Ube Industries, Ltd.

Claims (4)

[Claims] (1) A first substrate having a pixel electrode, a signal electrode disposed at a distance from the pixel electrode and sending a signal to the pixel electrode, and a varistor connecting the pixel electrode and the signal electrode; In an active matrix liquid crystal display device comprising a second substrate provided with electrodes facing each other, and a polymer-dispersed liquid crystal layer filled between the first substrate and the second substrate, the pixel electrode A liquid crystal display device characterized in that a varistor is coated so as to cover at least 50% of the length of an edge and a signal electrode. (2) The signal electrode is arranged to have a protrusion inserted between pixel electrodes with a gap, and a varistor is arranged to connect the pixel electrode and the signal electrode using the protrusion. A liquid crystal display device according to claim 1, characterized in that: (3) The signal electrode has a bent portion disposed with a gap between the pixel electrodes, and a varistor is provided that connects the pixel electrode and the signal electrode using the bent portion. A liquid crystal display device according to claim 1. (4) The liquid crystal display device according to claim 1, wherein the electrodes on the second substrate are arranged so as not to face the varistors arranged on the first substrate. .