JPS62160424A - Ferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE:To eliminate the stepping on a substrate surface by providing flattening films consisting of an insulator between adjacent transparent electrodes. CONSTITUTION:The flattening films 4 consisting of the insulators are provided between the transparent electrodes 2b contg. adjacent auxiliary conductive wires 3 formed on the substrate 1b to eliminate the stepping on the substrate 1b surface and to flatten said surface. As a result, a liquid crystal is oriented to a uniform monodomain and adequate driving characteristic is obtd. even if a ferroelectric liquid crystal 5 is used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to liquid crystal elements used in liquid crystal display elements, liquid crystal light shutters, etc., and more specifically, to liquid crystal element cells using ferroelectric liquid crystal. This relates to the electrode configuration on the substrate.

[Summary of the Disclosure] This specification and drawings describe the relationship between adjacent electrodes of a stripe-shaped transparent electrode in which a conductive film is electrically connected along the longitudinal direction of the stripe in a liquid crystal element using ferroelectric liquid crystal. By placing a flattening film made of an insulator on the substrate, it is possible to eliminate the level difference on the substrate surface, and as a result, the liquid crystal can be aligned in a uniform monodomain, and the proper driving characteristics of the ferroelectric liquid crystal element can be obtained. This is what I did.

[Prior Art] In recent years, liquid crystal elements using ferroelectric liquid crystals have been considered for application to high-definition large displays because of their high-speed response and memory properties. As the electrode structure of such a display device, a so-called simple matrix method is generally used in which a group of scanning electrodes and a group of signal electrodes formed in a stripe shape intersect in a plane, and the intersections are used as pixels.

In liquid crystal devices using this simple matrix method, as the resolution increases, the width of the electrodes becomes narrower and the resistance value per line of electrodes increases.As a result, variations occur in the voltage value even within one line, making it difficult to drive. There was a problem in that the necessary appropriate voltage was not applied to each pixel. Therefore, a method has been considered in which an auxiliary conductive line made of a conductor such as metal is provided along one end of the striped transparent electrode. According to this method, the resistance value per electrode line decreases,
Voltage variations can be eliminated.

[Problems to be solved by the invention] Currently, the most practical ferroelectric liquid crystal is chiral smectic C phase (Sac-
), 1 phase (1 Sm, G phase (S+eG gloss, H phase (S layer H
・). This liquid crystal phase is likely to cause alignment defects if there are steps in the substrate holding the liquid crystal, making it impossible to obtain uniform monodomains. When auxiliary conductive lines are provided, steps are created on the substrate, and when ferroelectric liquid crystal is used, uniform monodomains are not formed, resulting in failure to obtain appropriate drive characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ferroelectric liquid crystal element that eliminates the drawbacks of the prior art described above and can obtain appropriate driving characteristics.

[Means for Solving the Problems] The present invention provides a ferroelectric liquid crystal that has a pair of substrates, a striped transparent electrode formed on each of the pair of substrates, and a ferroelectric liquid crystal disposed between the pair of substrates. In the dielectric liquid crystal element, a conductive film in which a striped transparent electrode formed on at least one of the pair of substrates is electrically connected along the longitudinal direction of the striped shape is disposed, and This is a ferroelectric liquid crystal element characterized by having a flattening film formed of an insulator between adjacent stripe-shaped transparent electrodes.

As the auxiliary conductive wire in the present invention, a metal film such as aluminum, chromium, silver, etc. can be used, and it can be electrically connected and wired along the longitudinal direction of the striped transparent electrode.

In the present invention, as the flattening film disposed between adjacent striped transparent electrodes, for example, polyvinyl alcohol, polyimide, luminescent polyimide, or an insulator such as 5i02 can be used.

Further, the ferroelectric liquid crystal in the present invention includes a chiral smectic liquid crystal having at least two stable states,
Preferably, bistable smectic liquid crystals can be used.

[Function] Since the flattening film is formed with a thickness substantially equal to the maximum step difference, when the maximum step difference is a transparent electrode, the step difference between adjacent striped transparent electrodes disappears and the alignment surface becomes flat. becomes. In this way, by flattening the alignment plane in contact with liquid crystal molecules, uniform monodomain alignment can be obtained.

〔Example] The basic configuration of the present invention will be explained with reference to FIGS. 1 and 2.

FIG. 1 is a plan view of a substrate of a ferroelectric liquid crystal device according to the present invention, and FIG. 2 is a cross-sectional view of a device manufactured by combining the substrates.

In Figures 1 and 2, la and lb are substrates made of glass or plastic, and 2a and 2b are ITO (Indium
The electrodes are striped transparent electrodes made of (+5-Tin-Oxide) or the like and are arranged to cross each other. 3 is a low-resistance auxiliary conductive wire formed of a metal film such as aluminum, chromium, silver, etc.; 4 is, for example, polyvinyl alcohol;
A flattening film made of an insulating film such as polyimide, photosensitive polyimide or 5i02, 5 is a ferroelectric liquid crystal, and 6 is a film made of polyimide, polyvinyl alcohol, polyamide, etc., which is subjected to uniaxial alignment treatment such as rubbing. This is the obtained orientation control film.

Next, examples of the present invention will be described in more detail.

Example 1 ITO was formed to a thickness of 1000 Å on the entire surface of the glass substrate 1 by EB evaporation. With this ITOIli,
In order to form a striped electrode 2 with a pitch of 250 gta and a width of 220 gra, 500 OA of photoresist was applied onto the ITO film, and after exposure for desired patterning, etching was performed to form a striped transparent electrode 2. At this point, 5000A of resist agent remained on the electrode.Next, 100A of aluminum was deposited on the upper layer by EB evaporation method, and the resist agent was lifted off with an etching solution to form the auxiliary conductive wire 3. Through the above steps, the difference in level between the transparent electrode 2 and the auxiliary conductive wire 3 is eliminated.

Next, in order to eliminate electrical conduction between adjacent electrodes, a flattening film 4 made of an insulator was formed between the electrodes as shown in FIG. First, the substrate 1 was patterned again using the photoresist method, and a portion of the auxiliary conductor 393 was removed. Subsequently, Si02 is vapor-deposited with the resist agent remaining on each electrode, and the resist agent is lifted off again in 0 or more steps to form the transparent electrode 2, the auxiliary conductive wire 3, and the flattening [i4
The difference in film thickness disappears, and the substrate becomes flat. A 50 OA polyimide film with liquid crystal orientation was formed on the upper layer of this substrate by spinner coating, and then subjected to rubbing treatment to form an alignment control film 6.

Next, the electrodes of these two substrates are orthogonal to each other in a plane,
The cells were assembled so that the rubbing directions were parallel to each other. Note that the liquid crystal layer thickness is uniformly adjusted to 1.0 mm using bead-shaped alumina spacers. The thickness was maintained at θILm. A ferroelectric liquid crystal consisting of the following tertiary components was sealed in the liquid crystal cell thus prepared.

From phase observation using a polarizing microscope, the S
The temperature range of the ac phase was 4-35°C. After filling and sealing this tertiary mixed liquid crystal in the liquid crystal cell, the temperature was raised to the tokiyoshi phase, and the liquid crystal was slowly cooled at 0.5° C. to perform an alignment treatment. When the liquid crystal cell was observed under a microscope, monodomains with very few alignment defects were obtained. Furthermore, the liquid crystal exhibited bistability with a first and second stable state at this cell thickness.

Further, when a conductive wire was drawn out from the end of the substrate of this cell and a pulse voltage was applied to each pixel to invert the two states, the inversion was achieved with a voltage of ±18 V in 1 sec.

In this way, each pixel was uniformly inverted with a constant voltage, and it was confirmed that there was practically no variation in voltage within one line.

Example 2 DOBAMBCH3 shown below was sealed as a liquid crystal material, and an experiment otherwise similar to that of Example 1 was conducted, and a sufficiently uniform monodomain alignment could be obtained. Also, the driving voltage required for one inversion is 15eC
The voltage was ±16 V, and good driving characteristics were obtained as in Example 1.

The substrate of the comparative liquid crystal cell was constructed as follows. That is, a transparent electrode 2 was formed on a glass substrate 1, and an auxiliary conductive wire 3 was formed at one end of the transparent electrode. 5i used in the above example
The planarization film 4 made of 02 was removed from the structure, and an alignment control film 6 was formed on the electrode and subjected to a rubbing treatment. This comparative example corresponds to the conventional example, and with such a configuration, the step difference on the substrate surface becomes noticeable, and alignment defects of liquid crystal tend to occur from the step portion. In this comparative example, a cell was fabricated from the above substrate, and the three-component mixed liquid crystal described above was sealed therein. Using this cell, we conducted an experiment similar to that of the previous example, and observed that a zigzag alignment defect ran from the step, and that the bistability collapsed from this defect and immediately returned to its original stable state after 1 reversal. It was done.

FIG. 3 shows another embodiment of the ferroelectric liquid crystal element of the present invention. In the device shown in FIG. 3, in order to ensure electrical connection between the auxiliary conductive wire 3 and the striped transparent electrode 2b, the auxiliary conductive wire 3 forms a laminated portion on a part of the striped transparent electrode 2b. formed and wired to connect there. For this reason, the level difference is larger than in the element shown in FIG. 2 described above, and alignment defects are more likely to occur.

Therefore, the present invention provides an auxiliary conductor &a3 on the transparent electrode 2b.
By forming the planarization layer 4 with a thickness substantially equal to the maximum step difference A due to the lamination of the substrate lb,
In-plane steps can be eliminated.

[Effects of the Invention] As explained above, according to the present invention, it is possible to eliminate the level difference on the substrate due to the auxiliary conductive wires, achieve uniform monodomain alignment, and achieve proper alignment even when using ferroelectric liquid crystal. drive characteristics can be obtained.

[Brief Description of the Drawings] Fig. 1 is a plan view of a substrate showing the basic configuration of the present invention, Fig. 2 is a sectional view of an element manufactured using this substrate, and Fig. 3 is another ferroelectric liquid crystal of the present invention. FIG. 3 is a cross-sectional view showing an aspect of the element. l...Substrate, 2...Striped transparent electrode, 3...
- Auxiliary conductive line, 4... Flattening layer, 5... Ferroelectric liquid crystal, 6... Orientation control film. Figure 2: Cross section of the element Figure 3

Claims (7)

[Claims] (1) In a ferroelectric liquid crystal element having a pair of substrates, a striped transparent electrode formed on each of the pair of substrates, and a ferroelectric liquid crystal disposed between the pair of substrates, A conductive film is arranged in which striped transparent electrodes formed on at least one of the substrates are electrically connected along the longitudinal direction of the striped shape, and an insulator is disposed between adjacent striped transparent electrodes. A ferroelectric liquid crystal element comprising a flattening film formed of. (2) Claim 1, wherein the conductive film is a metal film.
The ferroelectric liquid crystal element described in . (3) The thickness of the planarization film is substantially equal to the maximum step difference existing within the plane of the substrate.
The ferroelectric liquid crystal element described in . (4) The ferroelectric liquid crystal element according to claim 1, wherein the thickness of the flattening film is substantially equal to the thickness of the transparent electrode having the largest step difference. (5) The thickness of the flattening film is substantially equal to the thickness of the layered portion of the conductive film and the transparent electrode having the maximum step difference. Ferroelectric liquid crystal element. (6) The ferroelectric liquid crystal device according to claim 1, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal having at least two stable states. (7) The ferroelectric liquid crystal device according to claim 1, wherein the ferroelectric liquid crystal is a bistable chiral smectic liquid crystal.