JPH0439626A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display element capable of applying uniform and vertical orientation and indicating uniform display free from irregular threshold voltage by rubbing the surface of a vertical orientation film in a direction approximately rectangular to a displaying band electrode. CONSTITUTION:Insulating transparent films 6, 7 are formed on the surfaces of substrates 2, 3 on which displaying band-like transparent electrodes 4, 5 are formed exclusing seal parts and pad parts and vertical orientation layers 8, 9 are formed on the surfaces of the films 6, 7. A liquid crystal component 10 is held between both the substrates 2, 3 so as to be contacted with the layers 8, 9 to form the liquid crystal display element 1. In said constitution, the surfaces of the layers 8, 9 are rubbed by cotton cloth in the direction rectangular to the electrodes 4, 5. Thus, the liquid crystal display element 1 having uniform vertical orientation and indicating uniform display free from irregular threshold voltage can be obtained.

Description

[Detailed Description of the Invention] CObject of the Invention] (Industrial Application Field) The present invention relates to a voltage-controlled birefringence effect type liquid crystal display element,
In particular, the present invention relates to a liquid crystal display element in which the long axis direction of liquid crystal molecules is oriented so as to be inclined in a certain direction at a uniform angle with respect to the normal line of a substrate.

(Prior art) In general, as liquid crystal display elements using a liquid crystal composition having negative dielectric anisotropy, there are voltage-controlled birefringence effect type liquid crystal display elements and guest-host type liquid crystal display elements mixed with dichroic dyes. . In these liquid crystal display elements, when no voltage is applied, the long axis direction of the liquid crystal molecules must be aligned perpendicular to the substrate surface (vertical alignment), but when a voltage is applied, Uniform display performance cannot be obtained unless the direction of rotation of the liquid crystal molecules is constant. Therefore, even when no voltage is applied, the vertical alignment is slightly tilted in a certain direction, that is, the long axis direction of the liquid crystal molecules is aligned with the substrate direction. An orientation tilted at a small angle in a certain direction with respect to the line is required.

Generally, the inclination directions of the liquid crystal molecules are configured to differ by 180 degrees ζ6 between the two substrate surfaces, as shown by the arrows in FIG.

The angle formed between the long axis direction of the liquid crystal molecules and the normal line of the substrate (hereinafter referred to as the tilt angle) is closely related to the display contrast when voltage is applied, and in order to obtain high contrast, the smaller the tilt angle, the better.

In general, a method for forming a vertical alignment layer is to apply a vertical alignment treatment agent to the substrate surface, then leave the substrate at room temperature or heat it to evaporate the solvent or polymerize the alignment agent, thereby creating a vertical alignment layer. There is a method of forming a vertical alignment layer, and a method of forming a vertical alignment layer by rotating oblique evaporation of an inorganic material such as SiO. When constructing a liquid crystal display element, this vertical alignment layer is applied to the part of the substrate surface that comes in contact with the adhesive (hereinafter referred to as the sealing part) and the part where the voltage introduction electrode terminals are arranged (hereinafter referred to as the pad part). It is more preferable in terms of the reliability of the liquid crystal display element that no . There is a rubbing method.

(Problem to be solved by the invention) However, in the method of forming a vertical alignment layer by rotating oblique evaporation of an inorganic material such as SiO, it is difficult to uniformly obtain vertical alignment slightly tilted in a certain direction over a large area. is difficult.

On the other hand, the orientation of liquid crystal molecules by the rubbing method is
Although it can be easily applied to devices with a large display area, many experiments by the present inventors have shown that when driving a liquid crystal display element, there is a problem that streak-like threshold voltage unevenness occurs parallel to the rubbing direction. Ta.

The present invention solves the above-mentioned conventional problems and provides a liquid crystal display element that provides uniform vertical alignment and exhibits uniform display performance without threshold voltage unevenness.

[Structure of the Invention] (Means for Solving the Problems) The liquid crystal display element of the present invention includes a liquid crystal composition having negative dielectric anisotropy between two electrode substrates having a plurality of display strip electrodes. In a liquid crystal display element in which a vertical alignment layer is formed on at least the surface of the electrode substrate in contact with the liquid crystal composition, the surface of the vertical alignment layer is in a direction substantially perpendicular to the display strip electrode. Further, if necessary, the liquid crystal composition having negative dielectric anisotropy has a helical pitch.

(Function) According to many experiments conducted by the present inventors, the slit-like threshold voltage unevenness parallel to the rubbing direction corresponds to the electrode group of the pad portion of the electrode substrate. It was found that the effect was due to the electrode group on the pad part at the beginning of contact with the cloth.

Therefore, by performing a rubbing process in a direction substantially perpendicular to the display band-shaped electrodes, the influence of the electrode group of the pad portion can be avoided. Here, if the rubbing direction is approximately perpendicular to the display band-shaped electrode, the tilt direction of the liquid crystal molecules when constructing a liquid crystal display element is 90 degrees between the two substrates as shown in FIG.
With a difference of 0 degrees, liquid crystal molecules take a so-called twisted orientation when a voltage is applied.

Therefore, in order to further stabilize the orientation of liquid crystal molecules when voltage is applied, it is effective to give the liquid crystal composition a helical pitch, if necessary.

(Embodiment) FIG. 1 shows a sectional view of an X-Y matrix type liquid crystal display element according to an embodiment of the present invention. The liquid crystal display element 1 has two substrates 2 and 3 made of transparent glass arranged facing each other.
．． A transparent electrode 4.5 is formed on each surface of the substrate 2.3, and an insulating transparent coating 6, 7 is formed on the surface of the substrate 2.3 on which the transparent electrodes 4, 5 are formed, except for the seal portion and the pad portion. A vertical alignment layer 8 is formed on the surface of the insulating transparent coating 6.7.
9 is formed. A liquid crystal composition 10 is sandwiched between these substrates 2 and 3 in contact with vertical alignment layers 8 and 9 to form a liquid crystal display element 1. Note that 11 is a substrate 2. A gap material 11 is used to control the gap between the substrates 2 and 3, and 11 is an adhesive for bonding the substrates 2 and 3 together. This liquid crystal display element 1 was manufactured as follows.

First, a glass substrate 2 with an outer diameter of 205 mm x 200 mm
, 3 by a normal method and etched it to a width of 0.85 mm and a pitch of 0.70 mm.
00 strip-shaped transparent electrodes 4.5 were formed. Next, the surface of the substrate 2.3 on which the electrode 4゜5 was formed, excluding the sealing part and pad part, was coated with a solution NHC (a product manufactured by Nissan Chemical Co., Ltd.) in which a film containing 5i02 as the main component was formed after film formation. Product name) was applied by printing method and heated at 250℃3 in air.
After baking for 0 minutes, an insulating transparent film 6°7 was formed. Next, octadecyltriethoxysilane was applied by dipping onto the surfaces of the substrates 2 and 3 on which the insulating transparent coating 6.7 had been formed, and then heat-treated at 150°C for 30 minutes in a nitrogen atmosphere to form a vertical alignment layer of 8°. 9 was formed.

Next, the surfaces of the vertical alignment layers 8 and 9 were rubbed with a cotton cloth in a direction perpendicular to the strip electrodes, and then plastic beads with a particle size of 10 μm were uniformly scattered on the surface of the vertical alignment layer 8 of the substrate 2 as a gap material 11. Furthermore, an epoxy adhesive was printed as the adhesive 12 on the surface of the vertical alignment layer 9 of the substrate 3.

Next, the substrates 2 and 3 were arranged so that the vertical alignment layers 8°9 faced each other, and the adhesive was cured by heating to bond the substrates 2 and 3 together. Next, EN-18 (manufactured by Chisso) is injected as the liquid crystal composition 12 through the injection port (not shown) in a usual manner, and then the injection port is sealed with an ultraviolet curable resin to form the liquid crystal display element 1. was created.

The liquid crystal display element 1 manufactured as described above exhibited uniform display performance without threshold voltage unevenness.

[Effects of the Invention] According to the present invention, it is possible to obtain a liquid crystal display element that has uniform vertical alignment and exhibits uniform display performance without threshold voltage unevenness.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a liquid crystal display element of the present invention, FIG. 2 is a diagram showing the rubbing direction of the liquid crystal display element of the present invention, and FIG. 3 is a diagram showing the rubbing direction of a conventional liquid crystal display element. 1...Liquid crystal display element 2.3...Glass substrate 4.
5...Transparent electrode 6.7...Insulating transparent coating 8.9...Vertical alignment layer 11...Gap material 10...Liquid crystal composition 12...Adhesive agent Patent attorney Nori Chika Ken Yudo Takehana Kikuo Rabbit Game Box Figure 1 Figure Figure

Claims (2)

[Claims] (1) An electrode substrate having a plurality of display strip electrodes, and a liquid crystal composition having negative dielectric anisotropy sandwiched between at least two of the electrode substrates; On the surface in contact with the liquid crystal composition,
A liquid crystal display element provided with a vertical alignment layer, wherein the surface of the vertical alignment layer is rubbed in a direction substantially perpendicular to the display strip electrode. (2) A liquid crystal display element, wherein the liquid crystal composition having negative dielectric anisotropy according to claim 1 has a helical pitch.