JPH0440412A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a bright display, to eliminate its coloration, and to prevent the display from being seen double by forming picture element electrodes on a reflecting film, provided on the liquid-crystal side surface of a substrate, across an insulating layer, and using liquid crystal and an orientation distribution which obtain nearly linearly polarized light when light made incident on a liquid crystal cell reaches a reflecting film. CONSTITUTION:The polyimide orienting film 13 is formed by coating on a glass substrate 11 where an ITO transparent electrode 12 is formed to obtain one substrate, and the reflecting film 18, an insulating layer an ITO transparent electrode 12, and an orienting film 13 are laminated in order to obtain the other substrate. Both the substrates are adhered together through a seal member 15 and the liquid crystal 14 is heated and sealed to obtain the element. Then, the liquid crystal and orientation distribution which obtain nearly linearly polarized light when the light made incident on the liquid crystal cell reaches the reflecting film are employed. Consequently, the display is bright, colored a little, and not seen double.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a reflective liquid crystal display element.

[Prior Art] Reflective TN mode and STN mode liquid crystal display elements have low power consumption and are therefore widely used in display devices such as portable personal computers and word processors. A conventional reflective liquid crystal display element consists of a liquid crystal cell, two polarizing plates placed on both sides of the liquid crystal cell, and a reflecting plate provided outside the polarizing plates.

[Problems to be Solved by the Invention] However, conventional liquid crystal display devices using reflective TN mode or STN mode have problems such as dark display and double images depending on the angle.

Particularly in the reflective STN mode, coloring of the display was also a problem.

The present invention is intended to solve the above problems, and its purpose is to introduce a new reflective liquid crystal mode and further optimize the cell structure to achieve brightness, no coloring, and a reflective display that does not cause double viewing. The purpose is to provide a type liquid crystal display element.

[Means for Solving the Problems] In order to solve the above problems, the liquid crystal display element of the present invention has the following features: (1) a liquid crystal cell formed by sandwiching twisted oriented nematic liquid crystal between two substrates having electrodes; In a liquid crystal display element equipped with two polarizing plates and one reflective film, the reflective film is provided on the liquid crystal side surface of a substrate constituting a liquid crystal cell,
A pixel electrode is formed on the reflective film via an insulating layer, and the liquid crystal and orientation distribution are used such that the light incident on the liquid crystal cell becomes almost linearly polarized light when it reaches the reflective film.

(2) In the liquid crystal cell, the twist angle of the liquid crystal molecules is 0.
degree or more and 70 degrees or less, the absolute value of the product of the birefringence index of the liquid crystal and the cell gap is 0.2 μm or more and 0.7 μm or less, and the direction of the polarization axis (absorption axis or transmission axis) of the polarizing plate is similar to that of the polarizing plate. It is characterized in that the angle formed between the substrate interface on the side in contact with the polarizing plate and the long axis direction of the liquid crystal molecules is 35 degrees or more and 115 degrees or less, with the twist direction of the liquid crystal molecules being positive.

(3) In the liquid crystal cell, the twist angle of the liquid crystal molecules is 1
The angle is 70 degrees or more and 270 degrees or less, and the absolute value of the product of the birefringence index of the liquid crystal and the cell gap is 0.4 μm or more and 1.0 μm or less.

(4) At least one of the two substrates constituting the liquid crystal cell has a step difference of 0° or more than 1 μm on the liquid crystal side surface.
It is characterized by providing unevenness of μm or less.

[Example] (Example 1) FIG. 1 is a sectional view of a liquid crystal display element according to an embodiment of the present invention.

One side of the substrate is a glass substrate 11 with an ITO transparent electrode 12 formed thereon and a polyimide alignment film 13 applied thereto, and the other substrate is a glass substrate 11 with a reflective film 18, an insulating layer 17, an ITO transparent electrode 12 and A structure in which alignment films 13 were sequentially laminated was used. Both types of plates were adhered via a sealing member 15, and a liquid crystal 14 was heated and sealed to obtain an element. Reflective film 18
is a thin aluminum film formed by sputtering on the surface of ground glass with an uneven surface of 0.5 μm.
It has reflective characteristics with little directivity.

A 5i02 film was used for the insulating layer 17. In this method, a transparent electrode is provided on a metal thin film through an insulator and patterned, and the twist angle is large because the insulating layer has the effect of alleviating surface irregularities.
This is particularly effective when the cell gap (p: spontaneous pitch of liquid crystal) is narrow.

The liquid crystal is Merck ZLI-4427 (△n-0,11
27), and the cell gap d was set to 6.6 μm. Retardation △nd=0. It is 74 μm. Polyimide RN-721 manufactured by Nissan Chemical Industries, Ltd. was used as the alignment film, and a pretilt angle of about 10 degrees was given to the liquid crystal molecules at the interface by rotational rubbing of a rayon flocked cloth.

FIG. 2 is a diagram showing the relationship between the respective axes of the liquid crystal display element of the present invention as viewed from the viewing direction. 23 is the polarization axis direction of the polarizing plate, 24
is the rubbing direction of the upper substrate, and 25 is the rubbing direction of the lower substrate. Further, 21 indicates the angle θ (the twist direction of the liquid crystal is a positive value) formed by 23 and 24, and 22 indicates the twist angle of the liquid crystal. Here, the angle 21 (θ) is 14 degrees, and the twist angle is 2
2 was set at 255 degrees to the left. The element thus obtained had a very good voltage reflectance characteristic steepness, and therefore exhibited a high contrast ratio of 1:18 even when multiplex driving was performed at a duty ratio of 1/480. By arranging the reflective film in the liquid crystal cell as described above, it is possible to solve the problem of double images peculiar to conventional reflective liquid crystal display elements. Furthermore, there is also the secondary effect that minute variations in the thickness of the liquid crystal layer average out the displayed colors and reduce coloration.

The reflective film may be made of any silver-white material other than aluminum, such as nickel or chromium, and the surface irregularities may be formed by polishing or chemical treatment.

[Effect of the invention J As described above, according to the present invention, by introducing a new reflective liquid crystal mode and optimizing the cell structure, a liquid crystal display that is bright, has little color change, and does not display double images can be created. element can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display element in Example 1 of the present invention. FIG. 2 is a diagram showing the positional relationship of the axes of each element in the liquid crystal display element of the present invention. Substrate Transparent electrode alignment film Liquid crystal layer Sealing member Polarizing plate Insulating layer Reflective film Angle θ between the polarizing axis direction of the polarizing plate and the rubbing direction of the upper substrate Twist angle of liquid crystal Direction of the polarizing axis of the polarizing plate Rubbing direction of the upper substrate Rubbing of the lower substrate Direction and above Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Kizobe Suzuki (1st name) Figure

Claims (4)

[Claims] (1) In a liquid crystal display element comprising a liquid crystal cell consisting of a twisted nematic liquid crystal sandwiched between two substrates having electrodes, one polarizing plate, and one reflective film, the reflective film is Provided on the liquid crystal side surface of the substrate that constitutes the liquid crystal cell,
A liquid crystal characterized by using a liquid crystal and an orientation distribution such that a pixel electrode is formed on the reflective film via an insulating layer, and the light incident on the liquid crystal cell becomes almost linearly polarized light when it reaches the reflective film. display element. (2) In the liquid crystal cell, the twist angle of the liquid crystal molecules is 0.
degree or more and 70 degrees or less, the absolute value of the product of the birefringence index of the liquid crystal and the cell gap is 0.2 μm or more and 0.7 μm or less, and the direction of the polarization axis (absorption axis or transmission axis) of the polarizing plate is similar to that of the polarizing plate. 2. The liquid crystal display according to claim 1, wherein the angle formed between the substrate interface on the side in contact with the polarizing plate and the long axis direction of the liquid crystal molecules is 35 degrees or more and 115 degrees or less, with the twist direction of the liquid crystal molecules being positive. element. (3) In the liquid crystal cell, the twist angle of the liquid crystal molecules is 1
2. The liquid crystal display element according to claim 1, wherein the angle is 70 degrees or more and 270 degrees or less, and the absolute value of the product of the birefringence index of the liquid crystal and the cell gap is 0.4 μm or more and 1.0 μm or less. (4) There is a step difference of 0.1 μm or more on the liquid crystal side surface of at least one of the two substrates constituting the liquid crystal cell.
2. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is provided with irregularities of .mu.m or less.