JPH08271921A - Liquid crystal device and its production - Google Patents

Abstract

PURPOSE: To provide a high precision liquid crystal device which attains a high quality display by a simple matrix method by flattening a step between a transparent electrode and a metal auxiliary electrode by using a transparent film. CONSTITUTION: A metal film is formed on an ITO electrode 6 having a specified electrode pattern on a glass substrate 7 and a photoresist is applied on it. The photoresist is exposed to light for the pattern of a metal auxiliary electrode and developed to obtain an etching resist 201. Then the metal is etched to form a metal auxiliary electrode 5. Further, a SiO2 film as a transparent film having almost same thickness as that of the metal auxiliary electrode 5 is formed on the substrate 7, and the etching resist 201 is peeled. In this process, the SiO2 film 202 on the etching resist 201 is also peeled with the etching resist 201, so that the step between the ITO electrode 6 and the metal auxiliary electrode 5 is flattened in the obtd. electrode 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.

In the operation mode having bistable or a plurality of stable states as applied to the above and the present invention, the switching between the two metastable states is basically a pulse response and therefore strongly affects the driving waveform. Dependent. Therefore, in order to maintain a drive waveform in order to perform a large screen and high-definition display, it is necessary to lower the resistance of the electrodes, and the ITO (Indium TFT)
inOxide) a method of forming a metal auxiliary electrode on the electrode has been adopted.

[0008]

When the metal auxiliary electrode (5) is formed on the ITO electrode (6) as shown in FIG.
A step having a thickness of the metal auxiliary electrode of about 100 to 200 nm is formed between the TO electrode (6) and the metal auxiliary electrode (5). When a liquid crystal panel is formed by using the substrate provided with these metal auxiliary electrodes, the ITO electrode-ITO is formed on the portion forming the pixel.
Between electrodes (d1), between ITO electrode and metal auxiliary electrode (d
2), three types of cell gaps are formed between the metal auxiliary electrode and the metal auxiliary electrode (d3). Therefore, the gap material maintains the cell thickness at the portions where the metal auxiliary electrodes face each other, and there is a floating gap material that does not contribute to maintaining the cell thickness in the pixel. There is a problem that the domain as the core is generated and the display quality is degraded.

Further, if the area of the portions where the metal auxiliary electrodes maintaining the cell thickness face each other becomes small, there arises a problem that it becomes difficult to control the cell thickness.

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

[0011]

In order to solve the above-mentioned problems, the liquid crystal device of the present invention comprises: (1) a scanning electrode group and a signal electrode group consisting of transparent electrodes and metal auxiliary electrodes on the transparent electrodes arranged in a matrix. A liquid crystal panel configured by sandwiching a liquid crystal having a memory effect between substrates arranged to form a pixel at an opposite portion thereof, for applying a drive voltage signal to electrodes, for selecting a memory state exhibited by the liquid crystal. A liquid crystal device comprising means for controlling a drive voltage signal, means for injecting polarized light into the liquid crystal panel and a polarizer arranged to identify light transmitted through the liquid crystal panel according to a selected storage state. It is characterized in that the step between the electrode and the metal auxiliary electrode is flattened.

(2) In the method of manufacturing the liquid crystal device,
After forming a metal film on the transparent electrode on which a predetermined pattern is formed, the metal film is etched by an etching resist to a predetermined pattern of the metal auxiliary electrode, and then the same thickness as the metal auxiliary electrode is formed on the substrate. After the transparent film is formed, the etching resist is peeled off.

(3) In (2), the transparent film having substantially the same thickness as the metal auxiliary electrode is an insulating film.

(4) In the above (2), the transparent film having substantially the same thickness as the metal auxiliary electrode is a conductive film.

(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 the 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.

[0016]

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 (6), a metal auxiliary electrode (5), a leveling layer (4), an insulating layer (3) and an alignment film (2) are laminated on a glass substrate (7), and a rubbing treatment is performed on the surface. They were applied and placed facing each other. When the liquid crystal (1) is enclosed between the substrates, the director vector (9) 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 example, a liquid crystal composition exhibiting a nematic phase at room temperature (ZLI-332 manufactured by E. Merck).
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.

(Embodiment 1) FIG. 2 shows a schematic sectional view of Embodiment 1 of the present invention. A metal film was formed to a thickness of about 200 nm on an ITO electrode (6) having a predetermined electrode pattern on a glass substrate (7), and then a photoresist was applied. Then, the pattern shape of the metal auxiliary electrode was exposed and developed to obtain an etching resist (201). Then, the metal was etched in the formed metal etching solution to form a metal auxiliary electrode (5) to obtain the state of FIG. Furthermore, as a transparent film on the substrate (7), SiO having the same thickness as the metal auxiliary electrode (5) is formed.
After forming the two films (202) (FIG. 2B), the etching resist (201) was peeled off. At this time, the SiO2 film (202) on the etching resist (201) is peeled off together with the etching resist, and as a result, as shown in FIG.
As in (c), an electrode substrate in which the steps between the ITO electrode (6) and the metal auxiliary electrode (5) were flattened could be prepared.

When the above-mentioned liquid crystal panel was prepared using the substrate prepared as described above, a flattened SiO 2 film (20
It was possible to provide a liquid crystal device having improved display quality by suppressing the generation of domains centering on the floating gap material in the pixel, which was observed in the case where 2) was not formed. Further, since the inside of the pixel is flattened, the area for maintaining the cell thickness becomes large, and the cell thickness control can be facilitated. Further, since the flattened SiO2 film (202) is an insulating film, it is possible to obtain the effect of reducing the blunting of the drive waveform applied to the liquid crystal by about 15%.

(Embodiment 2) FIG. 3 is a schematic sectional view of Embodiment 2 of the present invention. In Embodiment 1, an ITO film (301) as a transparent conductive film is formed instead of the SiO 2 film. Similar to Example 1, the step between the ITO electrode and the metal auxiliary electrode could be flattened, and a liquid crystal device with improved display quality could be easily provided. Further, since the flattened ITO film is a conductive film, it is possible to obtain the effect of increasing the effective value of the voltage applied to the liquid crystal by about 10%.

[0022]

As described above, according to the present invention, the step between the transparent electrode and the metal auxiliary electrode on the glass substrate is formed by SiO2.
It is possible to supply a flat transparent electrode with a metal auxiliary electrode without using an insulating film such as ITO or a conductive film such as ITO, and prevent the deterioration of display quality due to the domain in the pixel that has been seen in the past, thus facilitating a better display. Could be provided to. 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.

[0023]

[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 cross-sectional view showing a method of manufacturing a liquid crystal device used in Example 1 of the present invention.

FIG. 3 is a sectional view showing a method of manufacturing a liquid crystal device used in Example 2 of the present invention.

FIG. 4 is a general cross-sectional view of a liquid crystal device in which a metal auxiliary electrode is provided on a transparent electrode.

[Explanation of symbols]

1 Liquid crystal molecule 2 Alignment film 3 Insulating layer 4 Leveling layer 5 Metal auxiliary electrode 6 Transparent electrode 7 Glass substrate 8 Polarizing plate 9 Director vector θ1, θ2 Pretilt angle of liquid crystal molecule at the interface 201 Etching resist 202 SiO2 film 301 ITO film d1 ITO Electrode-ITO electrode cell thickness d2 ITO electrode-metal auxiliary electrode cell thickness d3 Metal auxiliary electrode-metal auxiliary electrode cell thickness

Claims (5)

[Claims] 1. A liquid crystal having a memory effect is sandwiched between a substrate on which a transparent electrode and a scanning electrode group and a signal electrode group each comprising a metal auxiliary electrode on the transparent electrode are arranged in a matrix form, and pixels are formed in the opposing portion thereof. And a means for applying a drive voltage signal to the electrodes, a means for controlling the drive voltage signal for selecting a memory state exhibited by the liquid crystal, and a means for injecting polarized light into the liquid crystal panel. In a liquid crystal device composed of a polarizer arranged so as to discriminate light passing through the light source in accordance with a selected memory state, a step of flattening a step between the transparent electrode and the metal auxiliary electrode with a transparent film is characterized in that Liquid crystal device. 2. In the method for manufacturing a liquid crystal device, a metal film is formed on the transparent electrode having a predetermined pattern, and the metal film is etched into a predetermined pattern of a metal auxiliary electrode with an etching resist, Next, a method of manufacturing a liquid crystal device, characterized in that a transparent film having a thickness substantially the same as that of the metal auxiliary electrode is formed on a substrate, and then the etching resist is removed. 3. The liquid crystal device according to claim 1, wherein the transparent film having substantially the same thickness as the metal auxiliary electrode is an insulating film, and the manufacturing method according to claim 2. 4. The liquid crystal device according to claim 1, wherein the transparent film having substantially the same thickness as the metal auxiliary electrode is a conductive film, and the manufacturing method according to claim 2. 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, 2, 3, and 4, and a method for manufacturing the same, wherein the liquid crystal is a liquid crystal having two metastable states of approximately (φr−180 °).