JPH08271920A - Liquid crystal device - Google Patents

Abstract

(57) [Abstract] [Purpose] A structure of a metal electrode for improving display uniformity and contrast in a large-screen and high-definition display device using a liquid crystal display having a metastable memory effect. [Structure] On a transparent electrode (6) having a stripe pattern formed on a glass substrate, two layers of a first metal having a good bonding property with the transparent electrode and a second metal having a specific resistance smaller than that of the first metal are formed. Form a metal electrode. The metal electrodes are arranged at both ends of the transparent electrode and at positions where they cover the space between the transparent electrodes on the counter substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using a liquid crystal, and more particularly to a liquid crystal device driven by a simple matrix using bistable switching.

[0002]

2. Description of the Related Art Liquid crystal devices currently in practical use as display devices for OA equipment are twisted nematic (T).
N) type liquid crystal or super twist nematic (S
A TN) type liquid crystal is used. For example, M.Schadt and WH
elfrich: Appl. Phys. Lett. 18 (1971) 127, or T.
J. Scheffer and J. Nehring: Appl. Phys. Lett. 45 (1984)
Since these display methods shown in 1021. do not have a memory effect, they are driven by a simple matrix driving method by a voltage averaging method or an active matrix driving method in which an active element such as a transistor is provided in each pixel.

Besides this, although it has not been put to practical use yet,
Various methods have been studied. For example, Japanese Patent Publication 1-51818
And USP 4,239,345, Japanese Examined Patent Publication No. 3-26368, JP-A-59-58420.
Discloses a method using bistable switching.

Regarding an operation mode having bistability or a plurality of stable states, it is suitable for high-definition display with a large number of scanning lines when it is possible to selectively switch between these states with an appropriate voltage waveform. Each has its own problems.

For example, Japanese Patent Publication 1-51818 and USP 4,239,34
Since the technology disclosed in 5 has bistability,
Information that has been written can be retained for a long time without using an active element. However, since switching between the two stable states is basically performed by abrupt cutoff of the applied voltage and a slow drop for about 1 second, it is not suitable for simple matrix driving, and the writing speed is very slow. In fact, Japanese Patent Publication No. 1-51818 only describes the switching principle, and does not disclose a simple matrix driving method.

A technique for realizing switching between two stable states by simple matrix driving is disclosed in, for example, Japanese Patent Laid-Open No.
No. 230751. The technique disclosed in Japanese Patent Laid-Open No. 6-230751 is φr in the initial state before voltage is applied.
In a liquid crystal device including a chiral nematic liquid crystal having a twist angle of, the initial state and the two metastable states in which the twist angle is approximately (φr + 180 °) and approximately (φr−180 °) for causing the Freedericksz transition And a reset pulse for applying a voltage equal to or higher than a threshold value, and a threshold value for causing either of the two metastable states to shift the liquid crystal after application of the reset pulse to one of the two metastable states. And a selection pulse selectively applied as.

[0007]

In the mode of operation having bistable or multiple stable states as described above and as applied to the present invention, the switching between the two metastable states is basically a pulse response. Therefore, it strongly depends on the driving waveform. Therefore, a large screen and high-definition display are
If only the TO (Indium Tin Oxide) electrode is used, there is a problem that the driving waveform becomes dull and uniform display becomes difficult.

Further, in an element which performs switching between two metastable states, there is a problem that light leakage occurs between pixels because of a state other than the two metastable states, resulting in a reduction in contrast.

The present invention is intended to solve the above problems, and an object thereof is to provide a high-definition liquid crystal device capable of high-quality display which can be realized by a simple matrix system.

[0010]

In order to solve the above-mentioned problems, the liquid crystal device of the present invention has the following problems. (1) Scan electrode groups and signal electrode groups made of transparent electrodes are arranged in a matrix, and pixels are arranged at the opposite portions thereof. A liquid crystal panel configured by sandwiching a liquid crystal having a memory effect between substrates to be formed, means for applying a drive voltage signal to electrodes, means for controlling a drive voltage signal for selecting a memory state exhibited by the liquid crystal, A liquid crystal device comprising a means for injecting polarized light into the liquid crystal panel and a polarizer arranged to identify light transmitted through the panel according to a selected storage state, comprising a metal electrode on the transparent electrode, It is characterized in that the metal electrodes are arranged at both ends of the transparent electrode and at positions covering the transparent electrodes on the counter substrate.

(2) The signal electrode is divided at a position slightly deviated from the center of the substrate to form a butt portion, and a light-shielding layer made of a metal electrode is provided at an end portion of the divided signal electrode. The width dimension of each layer is changed, and the abutting portion of the signal electrode substrate is shielded by a metal electrode provided along the scanning electrode of the opposing substrate.

(3) A first metal electrode and a second metal electrode having a resistance lower than that of the first metal are sequentially formed on the transparent electrode.

(4) The first metal electrode is Ni, Mo,
The second metal electrode is made of Cr or an alloy thereof, and the second metal electrode is made of Al, Cu or an alloy thereof.

(5) The liquid crystal having the memory effect has a twist angle of φr in the initial state before the voltage is applied, and the twist angle is approximately (φr + 180 °) in a relaxed state after the pulse voltage group is applied. ) And abbreviation (φr-180 °)
Is a liquid crystal having a property of having two metastable states.

[0015]

EXAMPLES The present invention will be described in detail below with reference to specific examples.

FIG. 1 is a schematic sectional view of a liquid crystal panel portion in the liquid crystal device of the present invention. A striped ITO transparent electrode (5), a metal auxiliary electrode (4), an insulating layer (3), and an alignment film (2) were laminated on a glass substrate (6), and the surfaces were subjected to a rubbing treatment to be opposed to each other. When the liquid crystal (1) is enclosed between the substrates, the director vector (8) is arranged with a constant pretilt angle (θ1, θ2) at the interface of the alignment film due to the effect of the alignment treatment. By adding an optically active substance to the liquid crystal, the liquid crystal molecules inside have a spiral structure having an axis in the direction normal to the substrate surface.

In this embodiment, a liquid crystal composition exhibiting a nematic phase at room temperature (ZLI-332 manufactured by E. Merck) is used.
9, Δn = 0.154) with an optically active additive (E. Mer
CK: S811) is added to add helical pitch p = 3.
It was adjusted to 5 μm. A polyimide alignment film was provided on the substrate interface, and the upper and lower substrates were subjected to rubbing treatment in the antiparallel direction (180 degrees) to obtain a gap d = 1.8 μm.
When the liquid crystal composition is enclosed, the interface pretilt angle becomes about 5 ° with the opposite sign in the vicinity of the upper and lower substrates, and p / 4 <d <
Since it is 3p / 4, the orientation of the liquid crystal molecules becomes a 180 ° twist state having a spiral axis in the substrate normal direction. The element of this structure produces two metastable states, that is, a substantially 0 ° twist (uniform) state and a substantially 360 ° twist state depending on the applied drive voltage waveform. Δn = 0.1 used in this example
Under the conditions of 54 μm and d = 1.8 μm, the uniform state has a molecular axis of about 45 due to a simple birefringence effect.
The main polarization axis of incident light polarized at an angle of 90 ° is rotated by about 90 ° and output. On the other hand, the 360 ° twist state is a state which can be regarded as being substantially optically isotropic, and therefore, the main polarization axis of the incident polarized light is transmitted while being retained.

FIG. 2 is a schematic view of the vicinity of the central portion of the panel of the metal electrode pattern of the embodiment of the present invention. FIG. 3A is a schematic view of a metal electrode pattern on a signal electrode substrate, and FIG. 3B is a schematic view of a metal electrode pattern on a scanning electrode substrate. The metal electrode is composed of both sides of the stripe-shaped transparent electrode and a portion that hides between the transparent electrodes of the counter substrate. The signal electrode is divided into two at a position slightly deviated from the center of the screen, and the metal electrode is also divided in the same manner. Further, as shown in FIG. 2A, the portion (202) of the metal electrode that hides the electrodes of the counter substrate is narrower than the portion (201) of the other electrodes that hides the electrodes of the other counter substrate at the divided positions. As shown in FIG. 2B, between the electrodes on the scanning electrodes at positions facing the divided signal electrodes (20
4) is narrower than between the other electrodes (203), and the metal electrode (206) along the transparent electrode is wider than the metal electrode (205) along the other transparent electrode. FIG. 3 shows a schematic view of these substrates arranged so as to face each other and viewed from above. Most of the pixels could be hidden, including the part where the signal electrode was divided.

The above-mentioned metal electrode is composed of two layers of metal. After forming an ITO electrode in a stripe shape as a transparent electrode on a glass substrate, Mo that has a good bonding property with the ITO electrode is formed.
Is deposited to a thickness of 100 nm, and then A having a smaller resistance value than Mo
l is deposited to 100 nm. After forming the metal film, an etching resist was formed and the above-mentioned metal electrode pattern was formed with a phosphoric acid-based etching solution.

When the above-mentioned liquid crystal panel was prepared using the substrate prepared as described above, the sheet resistance value of the electrode was IT.
It is possible to reduce the dullness of the drive waveform by reducing it from about 15Ω / □ for the O electrode only to about 2Ω / □. Furthermore, by concealing the pixels, the contrast is transmissive and the contrast is 30: 1 to 60: 1 for the ITO electrode only. It was possible to provide a liquid crystal device having improved display quality and excellent display quality.

[0021]

As described above, according to the present invention, the resistance value of the electrode is reduced and the light leakage between the pixels is reduced, so that the non-uniformity of the display and the deterioration of the contrast, which are seen in the conventional products, are reduced. It was possible to provide a liquid crystal device with improved display quality. The liquid crystal device of the present invention can support a high-definition display with a large number of scanning lines by simple matrix driving. It can be applied not only to direct-view type liquid crystal devices, but also to various light valves, spatial light modulators, and the like.

[0022]

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a liquid crystal device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing metal electrodes of a signal electrode and a scanning electrode according to an embodiment of the present invention.

FIG. 3 is a schematic view in which substrates of an embodiment of the present invention are arranged to face each other.

[Explanation of symbols]

1 Liquid crystal molecule 2 Alignment film 3 Insulating layer 4 Metal auxiliary electrode 5 Transparent electrode 6 Glass substrate 7 Polarizing plate 8 Director vector θ1, θ2 Pretilt angle of liquid crystal molecule at the interface

Claims (5)

[Claims] 1. A liquid crystal panel comprising a scanning electrode group and a signal electrode group made of transparent electrodes arranged in a matrix and sandwiching a liquid crystal having a memory effect between substrates facing each other to form pixels. A means for applying a drive voltage signal to the electrodes, a means for controlling the drive voltage signal for selecting the storage state exhibited by the liquid crystal, a means for injecting polarized light into the liquid crystal panel and a memory for selecting light transmitted through the panel A liquid crystal device composed of a polarizer arranged so as to be discriminated according to a state, wherein a metal electrode is provided on the transparent electrode, and the metal electrode covers both ends of the transparent electrode and between the transparent electrodes on a counter substrate. A liquid crystal device characterized in that it is arranged in. 2. The signal electrode is divided at a position slightly deviated from the center of the substrate to form an abutting portion, and a light shielding layer made of a metal electrode is provided at an end portion of the divided signal electrode, and two light shielding layers sandwich the abutting portion. The liquid crystal device is characterized in that the width dimension of the signal electrode substrate is changed and the abutting portion of the signal electrode substrate is shielded by a metal electrode provided along the scanning electrode of the opposing substrate. 3. A first metal electrode and the first metal electrode on the transparent electrode.
3. A liquid crystal device according to claim 1, wherein a second metal electrode having a resistance lower than that of the metal is sequentially formed. 4. The first metal electrode is made of Ni, Mo, Cr or an alloy thereof, and the second metal electrode is A.
l, Cu or their alloys,
The liquid crystal device according to claim 1. 5. The liquid crystal having the memory effect has a twist angle of φr in an initial state before a voltage is applied, and the twist angle is approximately (φr + 180 °) as a relaxed state after a pulse voltage group is applied. 5. The liquid crystal device according to claim 1, wherein the liquid crystal device has a property of having two metastable states of approximately (φr−180 °).