JPH03179324A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the display device consisting of polymer dispersion type liquid crystal which has small variance in contrast by making the interval between a picture element electrode and a signal electrode less than the thickness of a varistor. CONSTITUTION:A scanning electrode 7 is arranged on a 2nd substrate 6 so as to face the picture electrode 3 and a polymer dispersion type liquid crystal layer 8 is inserted between a 1st substrate 2 and the 2nd substrate 6. Then the interval l1 between the picture element electrode 3 and signal electrode 4 is made less than the thickness l1 of the varistor 5. Consequently, even when the scanning electrode 7 on the 2nd substrate 6 which faces the peak part of the varistor 5 arranged on the 1st substrate 2 comes close to the scanning electrode 7 on the 2nd substrate 6, any current does not flow from the signal electrode 4 to the scanning electrode 7 through the varistor 5. Consequently, a normal matrix circuit is composed of liquid crystal and the varistor 5 to make a high-brightness and high-contrast display.

Description

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

[Prior art and its problems]

Liquid crystal display devices can be driven at low voltages, have low power consumption, and can be directly driven by ICs, so they have the advantage that they can be easily made smaller and thinner.

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 order to display kanji characters in the information processing devices mentioned above, the number of pixels is much larger than that used in wristwatches, calculators, etc., and the driving method for liquid crystal display devices is usually a simple matrix drive in which electrodes intersect in an X-Y pattern. A circuit is used. In the simple matrix driving method, each pixel does not have an independent pixel electrode, so a constant voltage is also applied to adjacent pixels, and the adjacent pixels are not completely hidden, resulting in so-called crosstalk. This may occur.

In order to improve this crosstalk, there is a method of providing a nonlinear element such as a diode, thin film transistor, or varistor 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 almost the same characteristics.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 crystal, such as liquid crystal (ilinear aligned phase) liquid crystal, or liquid crystal composite film in which liquid crystal is contained as a continuous phase in the voids of a polymer matrix with a network structure, has been developed. ing. Polymer dispersed liquid crystal is
Since the thickness of the liquid crystal layer can be easily controlled, it is suitable as a liquid crystal material for large-sized display devices, and has characteristics such as fast response time, no need for polarizing plates, and wide viewing angle.

However, while the driving voltage of the TN type liquid crystal is about 5V, the driving voltage of the above-mentioned NCAP liquid crystal is high, on the order of tens to hundreds of volts. It was desired to reduce the development and drive voltage.

The present inventors proposed a liquid crystal display device comprising a polymer-dispersed liquid crystal layer using a film mainly composed of varistor powder as a nonlinear element in Japanese Patent Application No. 138870/1983. The liquid crystal display device proposed above can perform display with almost no crosstalk.

[Object of the present invention]

However, when a liquid crystal display device is manufactured by bonding a polymer-dispersed liquid crystal layer and a substrate on which a varistor layer is disposed by the method shown in the above proposal, the varistor layer disposed on the first substrate If the insulation between the top of the varistor and the opposing electrode on the second substrate is not sufficient, current may flow from the signal line to the electrode on the second substrate through the top of the varistor, resulting in some pixels Variations in the contrast may occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device made of a polymer-dispersed liquid crystal with little variation in contrast and which solves the above-mentioned problems.

[Means for solving problems]

The present invention provides 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 a liquid crystal display device comprising a second substrate provided with an electrode to face the pixel electrode and the signal electrode, and a polymer dispersed liquid crystal layer filled between the first substrate and the second substrate, the pixel electrode and the signal electrode The present invention relates to a liquid crystal display device characterized in that the distance between the varistors and the varistors is shorter than the thickness of the varistors.

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

FIG. 1 is a partially enlarged vertical cross-sectional view of a liquid crystal display device 1 of the present invention. FIG. 2 is a plan view showing the arrangement relationship of the pixel electrode 3, the signal electrode 4, and the varistor 5 provided on the first substrate 2. FIG. FIG. 3 is a partially enlarged vertical cross-sectional view of another liquid crystal display device 1 of type B.

On the first substrate 2, a pixel electrode 3 and a signal electrode 4 are arranged.The pixel electrode 3 and the signal electrode 4 are arranged with a gap 11 between them, and are electrically coupled by a varistor 5. ing. The interval lI between the pixel electrode 3 and the signal electrode 4 is generally 5 to 400 μm. Also, the thickness of the barista 5 is 12
is generally 5 to 500 μm. A scanning electrode 7 is arranged on the second substrate 6 so as to face the pixel electrode 3 .

A polymer dispersed liquid crystal N8 is sandwiched between the first substrate 2 and the second substrate 6. In the present invention, the distance II between the pixel electrode 3 and the signal electrode 4 is equal to the thickness 12 of the varistor 5.
It is shorter than . In the present invention, the thickness 2□ of the varistor 5 refers to the distance between the signal electrode 4 and the top of the varistor head. For example, in the case as shown in FIG. 3, the thickness of the varistor is indicated by 12 in the figure.

According to the present invention, the varistor 5 disposed on the first substrate
Even when the top of the head of the signal electrode 4 and the scanning electrode on the opposing second substrate are close to each other, the varistor voltage between the signal electrode 4 and the top of the varistor 5 is higher than the varistor voltage between the signal electrode 4 and the pixel electrode 3. Since it is large, no current flows from the signal electrode 4 through the top of the varistor 5 to the scanning electrode 7 on the second substrate.

Therefore, a normal matrix circuit of the liquid crystal and the varistor 5 is formed, and there is no variation in the contrast of each pixel. Preferably, the distance 13 between the pixel electrode 3 and the varistor top is set so that the varistor voltage between the pixel electrode 3 and the varistor top is greater than the voltage applied to the liquid crystal layer, and the distance 13 between the signal electrode 4 and the varistor top is The thickness of the varistor 5 is set so that the varistor voltage is greater than the driving voltage when driving the liquid crystal! ! , 2 is recommended. Further, in the case of the present invention, the top of the varistor 5 may be in contact with the scanning electrode 7 on the second substrate.

In the present invention, if the varistor is a varistor film mainly made of varistor powder, the varistor can be manufactured at any position and size on the substrate. Furthermore, if the varistor film is formed individually between the pixel electrode and the signal line by a printing method using a paste containing varistor powder as the main component, the manufacturing process will be faster than when using thin film formation technology. The method is simple and inexpensive, and it is possible to manufacture elements over a wide area at once, and it is possible to form stable varistor elements with little variation in characteristics.

When the varistor is a varistor film made mainly of varistor powder, by using varistor powder that is approximately spherical and has a uniform particle size, the varistor dark value voltage between each pixel electrode and the signal electrode becomes almost constant, resulting in a clear display. . The particle size of barista powder is generally 0.2 to 30 am, preferably 0.
．． It is 2 to 20 μm.

As the polymer-dispersed liquid crystal used in the present invention, NCA
So-called polymer dispersion, such as P-liquid crystal, in which a large number of capsule-shaped liquid crystals (not limited to spherical ones) are dispersed in a polymer matrix, and liquid crystal, which is dispersed in a polymer such as thermoplastic resin or epoxy resin. Examples include a type liquid crystal, or a liquid crystal composite film in which liquid crystal is contained as a continuous phase in voids in a polymer having a three-dimensional network structure.

〔Example] Hereinafter, the present invention will be explained in further detail by showing production examples.

Manufacturing Example 1 First, 20 g of an aqueous solution containing 2 g of polyvinyl alcohol dissolved on the scanning electrode 7 side of the substrate 6 having the transparent scanning electrode 7
, an emulsion consisting of 5 g of liquid crystal and 0.2 g of black dichroic dye was applied using a 120 μm doctor blade.
It was dried to form a polymer-dispersed liquid crystal layer 8 (thickness: 30 μm).

On the other hand, as shown in FIG. 2, a varistor element 12 (a varistor layer A thickness of 24 μm±3 μm) was formed.

Next, the first substrate 2 and the second substrate 6 on which the polymer dispersed liquid crystal N8 was formed were bonded together.

When multiplex driving (duty ratio 1/128) was performed with an AC voltage of ±140 V between the signal electrode 4 and the scanning electrode 7 of this liquid crystal display device, the desired pixel portion was bright without crosstalk (contrast ratio ~30). I was able to light it up. Also, no variation in contrast was observed.

Although the electrodes on the second substrate are used as scanning electrodes in the description, the invention is not necessarily limited to this, and the signal electrodes on the first substrate may be scanned during driving.

〔Effect of the invention〕

According to the present invention, the varistor 5 disposed on the first substrate
Even when the top of the head and the scanning electrode on the opposing second substrate are close to each other, no current flows from the signal electrode to the scanning electrode via the varistor, and a normal matrix circuit between the liquid crystal and the varistor is formed. This enables high brightness and high contrast display.

[Brief explanation of drawings]

FIG. 1 is a partial longitudinal sectional view of a liquid crystal display device of the present invention. FIG. 2 is a plan view showing the arrangement relationship of pixel electrodes, signal electrodes, and varistors on the first substrate. FIG. 3 is a partial longitudinal sectional view of a liquid crystal display device according to another embodiment of the present invention. 2.6: Substrate, 3: Pixel electrode, 4: Signal electrode, 5: Varistor, 7: Scanning electrode, : Polymer dispersed liquid crystal layer

Claims (1)

[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; A second electrode is provided to face the second electrode.
In a liquid crystal display device consisting of a substrate and a polymer-dispersed liquid crystal layer filled between a first substrate and a second substrate, the distance between the pixel electrode and the signal electrode is shorter than the thickness of the varistor. Characteristic liquid crystal display device.