JPH04315130A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display element which lessens the unequalness display and has a high grade by specifying the specific resistance of spacers and the specific resistance of a liquid crystal layer. CONSTITUTION:Oriented films 3 which are formed by providing films of polyimide, polyamide, etc., and subjecting the surfaces of the films to rubbing or diagonal vapor deposition of SiO, etc., are provided on the surfaces of substrates 1 consisting of plastic, glass, etc., provided with transparent electrodes 2 patterned to desired patterns. A liquid crystal layer 4 consisting of a liquid crystal formed by adding dichromatic dyes at need to a nematic liquid crystal, ferroelectric liquid crystal, etc., is crimped together with the spacers 5 between a pair of the substrates 1 with above-mentioned transparent electrodes 2. The spacers 5 are sprayed on the substrate 1 with the transparent electrodes and two sheets of the electrode surfaces are disposed to face each other. The substrates are then sealed by a sealing material 6. Further, the specific resistance P5 of the spacers 5 and the specific resistance PLC of the liquid crystal layer 4 are specified to the relation expressed by equation I.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display element.

0002

2. Description of the Related Art In recent years, liquid crystal display devices have been increasingly used because they are capable of displaying large areas at low voltages. A liquid crystal display element usually has a structure in which a liquid crystal layer is sandwiched between substrates provided with electrodes and a spacer for maintaining a distance between the substrates.

0003

SUMMARY OF THE INVENTION In such a liquid crystal display element, it is important to suppress display unevenness. One of the causes of this display unevenness is that the voltage threshold (Vth) at which the liquid crystal rises within the plane varies within the display plane.

The present invention aims to suppress variations in Vth within the display surface and to obtain a liquid crystal display element with less display unevenness.

[0005]

[Means for Solving the Problems] The present invention provides a liquid crystal display element comprising a pair of substrates with electrodes and a liquid crystal layer sandwiched between the substrates together with a spacer for maintaining a distance between the substrates. The relationship between the specific resistance ρs of the pacer and the specific resistance ρLC of the liquid crystal layer is 0.1≦ρs/ρLC≦
The present invention provides a liquid crystal display element characterized in that:

[0006] Conventionally, spacers are often made of insulating materials such as glass beads or fibers, and if the specific resistance of the spacer is higher than that of the liquid crystal, an electric charge is generated in the spacer part due to driving the liquid crystal, etc. It tends to concentrate, and its charge tends to attract ionic impurities from inside and outside the liquid crystal or liquid crystal display element, leading to their concentration. For this reason,
Substantially, the specific resistance of the liquid crystal layer varies depending on the location within the plane, and this is one of the causes of variation in Vth.

In the present invention, the specific resistance value of the spacer is approximately the same as the specific resistance value of the liquid crystal. By doing so, it is possible to prevent local concentration of ionic impurities and to suppress variations in the specific resistance of the liquid crystal layer. For this purpose, the specific resistance of the spacer ρs
The relationship between and the specific resistance ρLC of the liquid crystal layer is 0.1 ≦ρs/
It is desirable that ρLC≦10.

[0008] Such a spacer has a relatively low resistivity.
For example, it can be obtained by using a mixture of an insulating material and a substance with a resistivity closer to a semiconductor than an insulator as the main material, or by coating the spacer surface with a material having a relatively low resistivity. Examples of materials having resistance values close to or comparable to semiconductors include surfactants, field transfer complexes, organic semiconductors, and conductive polymers.

[0009] Such a material may be coated on the surface of commonly used insulating spacers such as glass beads or glass fibers. Coating methods include dip method,
Examples include spray method, vapor phase growth method, MOCVD method, and vapor deposition method.

The structure of the liquid crystal display element of the present invention will be explained below.

FIG. 1 is a sectional view of a liquid crystal display element according to the present invention. ITO (In
A film of polyimide, polyamide, etc. is provided on the surface of a substrate 1 made of plastic, glass, etc. on which a transparent electrode 2 of SnO2 (2O3-SnO2), SnO2, etc. is provided, and this surface is rubbed, or SiO2, etc. is deposited obliquely. The formed alignment control film 3 is provided, and a liquid crystal layer 4 made of a liquid crystal obtained by adding a dichroic dye to a nematic liquid crystal, a ferroelectric liquid crystal, etc. as necessary, is placed between the pair of substrates with transparent electrodes. pacer 5
so that it is held together with the Specifically, spacers 5 are sprinkled on the substrate with transparent electrodes, the electrode surfaces of the two substrates with transparent electrodes face each other, the periphery is sealed with sealant 6, liquid crystal is injected and sealed, and the liquid crystal layer is formed. form 4.

An example of an electrode pattern is one in which a large number of electrodes are formed in rows and columns. For example, there is one in which 640 striped electrodes are formed on one substrate, and 400 striped electrodes are formed perpendicularly to this on the other substrate.

Note that a SiO2 film or the like is provided under the electrode to prevent alkaline leaching from the substrate, and a TiO2 or S film is provided between the electrode and the alignment control film to prevent short circuit between the substrates.
Insulating films such as iO2 and Al2O3 are provided, base treatment films are used to improve the adhesion of alignment control films, low resistance lead electrodes such as Al, Cr, and Ti are added to transparent electrodes, and color filters are used. It may be laminated above or below the electrode.

[0014] Furthermore, these electrodes may have a two-layer structure with an insulating film interposed therebetween, or an active element such as a thin film transistor or a nonlinear resistance element may be formed.

A pair of polarizing plates is usually placed on both sides of this liquid crystal layer. This polarizing plate itself is generally placed outside the substrate that makes up the cell, but if performance permits, the substrate itself may be made up of a polarizing plate, or it may be provided as a polarizing layer between the substrate and the electrode. Good too.

[0016] Furthermore, if necessary, characters, figures, light-shielding films, color filters, etc. may be provided on the outer surface of the cell by a method such as printing, or a light non-reflection layer may be formed.

According to the present invention, driving means for applying a voltage to the electrodes of the liquid crystal cell having such a structure is connected to drive the liquid crystal cell.

The present invention can be applied to either a transmissive type or a reflective type, and has a wide range of applications. Note that when using a transmission type, a light source is placed on the back side. Of course, a light guide and a color filter may also be used together. When using a transmissive type, the background portion other than the pixels can be covered with a light-shielding film by printing or the like. In addition, along with using a light-shielding film,
It is also possible to drive in the opposite direction so as to apply a selection voltage to a portion that is not desired to be displayed.

In addition to the above, various techniques used in ordinary liquid crystal display elements can be applied to the present invention within a range that does not impair the effects of the present invention.

[0020]

【Example】

Example 1 As a first substrate, an ITO transparent electrode provided on a glass substrate was patterned into stripes, an insulating film made of SiO2 for short circuit prevention was formed by vapor deposition, and a polyimide overcoat was spun on this. A substrate on which an alignment control film was formed was prepared by coating and rubbing the coating.

[0021] As a second substrate, an ITO transparent electrode provided on a glass substrate was patterned into a stripe shape perpendicular to the first substrate, and an insulating film made of SiO2 for short circuit prevention was formed by vapor deposition. Thereafter, a polyimide overcoat was spin-coated on this, and this was rubbed to create a substrate on which an alignment control film was formed.

[0022] This first substrate has a specific resistance of about 1010Ω.
2 cm spacers are scattered, and the periphery of these two substrates is sealed with a sealing material to form a layer into which the liquid crystal cell will be injected.
This layer has positive dielectric anisotropy and a specific resistance of approximately 1010Ω・cm.
of nematic liquid crystal was injected and the injection port was sealed. Polarizing plates were arranged on both sides of this liquid crystal cell so that the polarization axes were parallel to each other to form a liquid crystal display element. The obtained liquid crystal display element had good appearance with little display unevenness.

Example 2 The specific resistance value of the spacer was set to about 1011 Ω·cm, and the specific resistance value of the liquid crystal was set to about 1011 Ω·cm.
When a liquid crystal display element was prepared in the same manner as above, a liquid crystal display element with less display unevenness was similarly obtained.

Example 3 The specific resistance value of the spacer was set to about 1012 Ω·cm, and the specific resistance value of the liquid crystal was set to about 1012 Ω·cm.
When a liquid crystal display element was prepared in the same manner as above, a liquid crystal display element with less display unevenness was similarly obtained.

Example 4 The specific resistance value of the spacer is approximately 1010Ω·cm to 1012
The specific resistance value of the liquid crystal is made to vary by Ω・cm and is approximately 10.
When the resistance was adjusted to 11 Ω·cm and a liquid crystal display element was produced in the same manner as in Example 1, a liquid crystal display element with less display unevenness was similarly obtained.

[0026]

Effects of the Invention According to the present invention, since local concentration of charges within the display surface can be prevented, local concentration of impurities can be suppressed, and V
A liquid crystal display element with high display quality and fewer ON/OFF defects due to variations in th can be realized. Furthermore, since the substantial specific resistance of the liquid crystal layer in the plane is made uniform, resistance to static electricity can also be improved.

[Brief explanation of drawings]

[Fig. 1] Cross-sectional view of a liquid crystal display element according to the present invention

[Explanation of symbols]

1 Board 2 Electrode 3 Orientation control film 4 Liquid crystal layer 5 Spacer

Claims (1)

[Claims] 1. A liquid crystal display element comprising a pair of substrates with electrodes and a liquid crystal layer sandwiched between the substrates together with a spacer for maintaining a distance between the substrates, in which specific resistance ρs of the spacer and The relationship between the specific resistance ρLC of the liquid crystal layer is
A liquid crystal display element characterized in that 0.1≦ρs/ρLC≦10.