JPH03196018A - Liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a liquid crystal display that has no crosstalk and can display in either a backlight method or a reflective method depending on the brightness of external light. Regarding equipment.

[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 thousands to hundreds of thousands of pixels, without defects or with almost the same characteristics.There is little variation in characteristics and it is possible to form 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, conventional liquid crystal display devices are limited to display using either a backlight method or a reflection method. Therefore, in the case of the backlight method, it can be seen well when it is dark outside, such as at night, but it is difficult to see under sunlight, while in the case of the reflection method, it can be seen well under sunlight, but it is difficult to see well when it is dark outside.

[Means for solving problems]

An object of the present invention is to provide a liquid crystal display device comprising a polymer-dispersed liquid crystal layer that solves the above-mentioned 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 substrate, and a polymer dispersed liquid crystal layer filled between the first substrate and the second substrate, the first substrate is consisting of a transparent substrate, and a first
The present invention relates to a liquid crystal display device characterized in that it has a light source on the back of a substrate.

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

FIG. 1 is a partially enlarged vertical sectional view showing one embodiment of a liquid crystal display device l 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 semi-transparent first substrate 2. FIG. 3 is a partially enlarged vertical cross-sectional view of another embodiment of the liquid crystal display device 1.

In the embodiment shown in FIG. 1, the first substrate 2 is a transparent substrate 2A.
Although it has a structure in which the transparent substrate 2A is stacked with the semi-transparent substrate 2B, by directly depositing metal such as aluminum on the transparent substrate 2A,
It is also possible to use a semi-transparent substrate 2 consisting of two substrates.

During the day when external light is strong, the incident light is transmitted through the semi-transparent substrate 2A.
On the other hand, at night when external light is weak, by lighting up the light source 9 provided on the back of the first substrate 2, a backlight type display can be performed.

As shown in Figure 1, the optical sensor measures the amount of external light.
10 and in combination with the lighting control device 11 to turn on and off the light source, it is also possible to automatically select the backlight method and the reflection method for display.

Semi-transparent substrates used in the present invention include aluminum-deposited glass substrates and silver-coated film substrates obtained by vacuum-depositing or coating aluminum, silver, etc. on substrates such as glass and plastic films. Preferred examples include the following substrates.

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 spaced apart from each other, and are electrically coupled by a varistor 5. Generally, the distance between the pixel electrode 3 and the signal electrode 4 is 5~
It is 400 μm.

Further, the thickness of the varistor 5 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 layer 8 is sandwiched between the first substrate 2 and the second substrate 6.

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 in 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 μm, preferably 0.2 to 30 μm.
．． 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 doctor blade and dried to form a polymer-dispersed liquid crystal layer 8 (thickness: 17 μm).

On the other hand, as shown in FIG. 2, a varistor element is printed between the signal electrode 4 made of a transparent electrode and the pixel electrode 3 (distance between the signal electrode 4 and the pixel electrode 3 = 100 μm) on the substrate 2A. No. 12 (varistor layer thickness: 12 μm) was formed.

Next, the second substrate 2A and the polymer-dispersed liquid crystal layer 8 are formed.
and the substrate 6 were bonded together.

Next, a semi-transparent substrate 2B obtained by vacuum-depositing aluminum on a glass substrate in advance was bonded to the back surface of the substrate 2A.

This liquid crystal display device is placed in a dark room, the fluorescent lamp 9 provided on the back of the first substrate 2 is turned on, and a multiplex drive (duty ratio 1/12B), the desired pixel area could be lit brightly (contrast ratio ~20) without crosstalk. Next, when the liquid crystal display device was placed under sunlight and multiplex driving was performed in the same manner as above, it was possible to light up brightly (contrast ratio ~20) without crosstalk.

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.

Furthermore, color display can be performed by disposing R, G, and B color filters between the first substrates 2A and 2B so as to correspond to each pixel electrode.

〔Effect of the invention〕

The liquid crystal display device of the present invention has no crosstalk and can display by switching between a backlight method and a reflection method depending on the brightness of external light, so it can display advertisements outdoors depending on whether it is day or night. It can be carried out suitably without any problems.

[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. 2: first substrate, 2A: transparent substrate, 2B semi-transparent substrate, 3: pixel electrode, 4: signal electrode, 5: varistor, 6:
Second substrate, 7: Scanning electrode, 8: Polymer dispersed liquid crystal layer, 9: Light source

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.
A liquid crystal display device comprising a substrate and a polymer-dispersed liquid crystal layer filled between a first substrate and a second substrate, wherein the first substrate is a semi-transparent substrate, and the first substrate is a semi-transparent substrate. A liquid crystal display device characterized by having a light source on the back of the device.