JPH0368921A - liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display device having high brightness and less crosstalks by providing insulating means between the varisters on a 1st substrate and the electrodes on a 2nd substrate. CONSTITUTION:Picture element electrodes 14 and signal lines 13 are parted from each other and are disposed on the 1st substrate 11. These electrodes and liens are electrically coupled by the varisters 12. The spacings are 10 to 400mum. The insulating means 32, such as SiO2 films, are formed on the surfaces of the varister films. Scanning electrode 22 are disposed to face the picture element electrodes 14 on the 2nd substrate 21. The polymer dispersion type liquid crystal layer 32 is crimped between the substrates 11 and 21 and the layer thickness thereof is specified to 5 to 50mum. The flow of currents to the scanning electrode lines 22 via the varisters 14 from the signal lines 13 is obviated even if the polymer dispersion type liquid crystal layer is formed thin in order to decrease the driving voltage according to this constitution. The normal matrix circuit of the liquid crystal with the varisters 12 is thus formed and the display with the high brightness and high contrast is executed.

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, the portability and thinness of the devices have increased.
With the growing demand for miniaturization, liquid crystal display elements are beginning to be adopted as display elements to replace CRTs. In order to display kanji in the above information processing device, wristwatches,
The number of pixels is much larger than in applications such as calculators, and the driving method for liquid crystal display devices is usually a simple matrix drive circuit in which electrodes intersect in an X-Y pattern. 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 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. 63-240658. The liquid crystal display device proposed above can perform display with almost no crosstalk and can reduce driving voltage.

C. Purpose of the Present Invention The applicant has researched the above-mentioned proposed device and has discovered the following facts. That is, when forming the thin liquid crystal display device shown in FIG. 4, since the surface portion of the varistor film 44 on the first substrate 41a and the scanning line electrode 45 on the second substrate 41b are close to each other, Current can easily flow from the signal line 43 provided on the first substrate 41a to the scanning line electrode 45 provided on the second substrate 41b via the varistor film 44, or from the pixel electrode 42 to the varistor film 44. The pixel electrode 42 formed on the first substrate 41a and the scanning vA
A problem arises in that the voltage between the display and the electrode 45 decreases, making it impossible to obtain display with desired brightness. This phenomenon is LCD Ji
This becomes more noticeable as 46 becomes thinner.

It is an object of the present invention to solve these problems and provide a liquid crystal display device with high brightness and less crosstalk.

[Means for solving problems]

The present invention provides a first substrate having a pixel electrode, a signal line 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 line; A second electrode is provided facing the second electrode.
In a liquid crystal display device comprising a substrate and a polymer-dispersed liquid crystal layer filled between a first substrate and a second substrate, a varistor disposed on the first substrate and a varistor disposed on the second substrate The present invention relates to a liquid crystal display device characterized in that an insulating means is provided between arranged electrodes.

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

FIG. 1 is a partially enlarged longitudinal sectional view of a liquid crystal display device in which an insulating means 32 such as an insulating film is provided on the surface of the varistor 12 of the present invention. FIG. 2 is a plan view showing the relationship between the pixel electrode 14, the signal line 13, and the varistor 12 provided on the first substrate 11, and FIG.
FIG. 3 is a plan view showing the upper electrode 22;

A pixel electrode 14 and a signal line 13 are arranged on the first substrate ll. The pixel electrode 14 and the signal line 13 are spaced apart from each other, and are electrically coupled by a varistor 12. The interval between the pixel electrode 14 and the signal line 13 is generally 10 to 400 μm. In FIG. 1, an insulating means 32 such as a silicon oxide film is provided on the surface of a varistor film formed on a first substrate. A scanning line electrode 22 is arranged on the second substrate 21 so as to face the pixel electrode 14 . First substrate 11 and second substrate 2
1, a polymer-dispersed liquid crystal layer 31 is sandwiched therebetween. The thickness of the polymer-dispersed liquid crystal layer 31 is generally 5 to 5.
It is 50 μm.

As the above-mentioned insulating means, for example, an insulating film may be provided between both substrates.

The material for forming the insulating film is not particularly limited, and any material having insulating properties may be used. Specific examples include organic materials such as polyimide, polyamide, polyethylene, polypropylene, polyethylene terephthalate, polyurethane, polyacrylate, silicon oxide, titanium oxide,
Inorganic materials such as argonium oxide and glass can be mentioned.

The insulating film can be formed, for example, by dissolving a polymer in a solvent and applying it on the varistor disposed on the first substrate, or
It can be manufactured by coating a portion of an electrode disposed on a substrate facing a varistor. The insulating film is
In addition to the above, it can be formed by various methods depending on the materials used, for example (1)? By applying an 8-melting polymer on the varistor or scanning line, (2) in the case of polyimide, silicon oxide, etc., by applying and baking a precursor, and (3) in the case of low-melting materials such as glass. (4) In the case of a high point material such as aluminum oxide, it can be formed by vapor deposition or sputtering. When using a material such as silicon oxide or polyimide that is transparent and has a high insulating effect, it may be applied to the entire surface of the 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 in particle size, the varistor dark value voltage between each pixel electrode and the signal line becomes almost constant, resulting in a clear display. . The particle size of barista powder is generally 1 to 30 am, preferably 2 to 20 am.
It is μm.

As the polymer-dispersed liquid crystal used in the present invention, NCA
Examples include those in which a large number of capsule-shaped liquid crystals (not limited to spherical ones) are dispersed in a polymer matrix such as P liquid crystal. In addition, as another polymer 2-dispersed liquid crystal, 7. Chem proposed by Kaj iyama et al.
Examples include a liquid crystal composite film in which a liquid crystal is contained as a continuous phase in the voids in a polymer having a network structure, as described in Istry Letters, 679 (1979).

〔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, 5 g of liquid crystal, and 0.0 g of black dichroic dye were placed on the scanning electrode 22 side of the substrate 21 having the transparent scanning electrode 22 shown in FIG.
An emulsion containing 2 g was applied using a 100 μm doctor blade and dried to form a polymer-dispersed liquid crystal layer 31 (thickness: 15 μm).

On the other hand, as shown in Fig. 2, the signal line 1 made of transparent electrode
3 and the pixel electrode 14, a varistor element 12 (0.5an x 0.5nm, thickness 11μm±3μ
m, varistor voltage 80V±2V).

Next, a liquid made of an organosilicon compound was applied to the surface of the varistor formed on the first substrate and baked at 500° C. to form a silicon oxide film 32 of about 1 μm on the surface of the varistor.

Next, the first substrate on which the silicon oxide film 32 was formed and the second substrate on which the polymer dispersed liquid crystal layer 31 was formed were bonded together.

When multiplex driving (duty ratio 1/400) was performed with an AC voltage of ±140 V between the signal line 13 and the scanning line electrode 22 of this liquid crystal display device, the desired pixel portion was bright without crosstalk (contrast ratio ~30 ) could be lit.

Production Example 2 A photosensitive polyimide precursor is applied onto the second substrate on which the scanning line electrodes 22 are patterned, and through the steps of exposure using a photomask, development, and baking, the photosensitive polyimide precursor is applied to the portion facing the varistor. A polyimide insulating film with a thickness of 2 μm was formed.

Next, a polymer-dispersed liquid crystal layer was formed by the same method as in Production Example 1, and then bonded to a first substrate on which a varistor as shown in FIG. 2 was disposed. AC voltage ±140
■ Multiplex drive (duty ratio 1/400)
As a result, the desired pixel area was able to be lit brightly (contrast ratio ~28) without crosstalk.

In the explanation, the signal electrodes on the second substrate are assumed to be scanning line electrodes, but they are not necessarily limited to this.
The signal line on the first substrate may be scanned during driving.

〔Effect of the invention〕

According to the present invention, even when the thickness of the polymer-dispersed liquid crystal layer is reduced in order to reduce the driving voltage, current does not flow from the signal line 13 to the scanning line electrode 15 via the varistor 14, and the liquid crystal A normal matrix circuit is formed with the varistor 12, allowing 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 of pixel electrodes, signal lines, and varistors on the first substrate, and FIG. 3 is a diagram showing the scanning line electrodes on the second substrate. FIG. 4 is a partial vertical sectional view of a conventional liquid crystal display device.

Claims (1)

[Claims] (1) A first substrate having a pixel electrode, a signal line 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 line; In a 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, A liquid crystal display device characterized in that an insulating means is provided between the provided varistor and the electrode provided on the second substrate.