JPH03154030A - Ferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain a panel which can control the oriented state of a ferroelectric liquid crystal of an inter-picture element and has a high display quality being free from a flaw such as roughness, etc., on a screen by making surface roughness of the inter-picture element rougher than that of a picture element part of an opposed substrate and making it asymmetrical. CONSTITUTION:In the ferroelectric liquid crystal which is provided with a ferroelectric liquid crystal, a pair of substrates opposed by arranging the ferroelectric liquid crystal therebetween, and two sets of opposed electrode groups 3 which are formed on a pair of substrates so that each electrode crosses and opposes each other and applies a voltage to the ferroelectric liquid crystal and drives it, and in which the surface average roughness of the electrode of a picture element part being an intersection part of each electrode is <=60Angstrom , the surface average roughness of the substrate part between picture elements having no electrode is 60 - 200Angstrom , and the average pitch of its roughness is 200 - 5,000Angstrom . According to this constitution, an orientation between the picture elements can be controlled, therefore, the display quality is improved. Also, since the inter-picture element is brought to etching in a state that a resist used at the time of forming the electrode is left as it is, the patterning process is omitted, and also, the undesirable influence exerted on the surface of residual gas, etc., is eliminated, as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a chiral smectic liquid crystal element (ferroelectric liquid crystal element), and particularly to a ferroelectric liquid crystal element with improved visibility.

[Prior art] Clark (
C1ark) and Lagerwal (C1ark) and Lagerwal (C1ark)
1) (U.S. Pat. No. 4,367,934).
specification, US Pat. No. 4,639,089, etc.). The chiral smectic liquid crystal used in this display element generally has a chiral smectic C phase (sm*c) or H phase (Sm*H) in a specific temperature range, and in this state, it responds to an applied electric field. It has the property of taking either the first optically stable state or the second optically stable state and maintaining that state when no electric field is applied, that is, it has bistability, and also has bistability, and is resistant to changes in the electric field. It also has a quick response, and is expected to be widely used in high-speed and memory-type display devices.

This display element is equipped with a matrix electrode composed of a scanning electrode and a signal electrode for multiplexing driving a chiral smectic liquid crystal.A scanning signal is sequentially applied to the scanning electrode, and the signal electrode is An information signal is applied to.

[Problems to be Solved by the Invention] However, in such conventional technology, when applying multiplexing drive to an applied chiral smectic liquid crystal, although the switching of the liquid crystal within a pixel is good, depending on the distance between pixels, under certain conditions This causes the liquid crystal between the pixels to be driven (normally not), resulting in irregularities between the pixels, or because they are originally oriented unevenly, the display screen may appear rough or have a certain pattern. There was a problem that .

An object of the present invention is to provide a liquid crystal element that solves the problems of the prior art.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a ferroelectric liquid crystal, a pair of substrates facing each other with the ferroelectric liquid crystal disposed therebetween, and electrodes that intersect and face each other. The ferroelectric liquid crystal is formed on a pair of substrates and has two opposing electrode groups for applying voltage to drive the ferroelectric liquid crystal. In a strong current reading liquid crystal device, the average surface roughness of the substrate portion between pixels without electrodes is 60 to 200, and the average pitch of the roughness is 20.
0 to 5,000 people).

The electrode group is usually formed by etching using a photoresist, and the roughness of the substrate portion between the pixels is determined by etching the substrate between the pixels while leaving the photoresist used for etching.
Formed by dry etching the part.

Chiral smectic liquid crystal is usually used as the ferroelectric liquid crystal, and its film thickness is set to be thin enough to control the formation of the inherent helical structure in the bulk state. The hairpin defect tends to generate a hairpin defect and a lightning defect, or the hairpin defect generates a lightning defect. As shown in FIG. 3, the roughness pitch means the distance between minimum roughness values.

[Function] As mentioned above, variations between pixels seriously deteriorate the display quality, but in the present invention, the surface roughness between the pixels is made rougher than that of the pixel portion (electrode portion) of the opposing substrate to prevent asymmetry. Therefore, the alignment of liquid crystal between pixels is preferably controlled, and display quality is improved. For this reason, in the present invention, it is necessary to aggressively roughen the area between pixels and keep the opposing substrate less rough than this, so the surface roughness of the transparent electrode on the opposing substrate side is kept to a certain level. It is assumed that the The reason why the liquid crystal in the area between pixels is controlled by this asymmetry in surface roughness is not clear at present, but when the roughness of the electrode surface facing between pixels is 60 Å or more, the surface roughness between pixels is Even if it was made as coarse as possible within the manufacturable range, it was not possible to control between pixels. Therefore, the above-mentioned roughness is set to be 60 Å or less in terms of surface average roughness.

Dry etching is a known and simple method for controlling the pixel density, but in the present invention,
Since etching is performed between pixels while leaving the resist used when forming the electrodes, the patterning process for etching is omitted, and at the same time, there is no adverse effect on the surface due to etching residual gas, etc., and therefore the display quality is improved. A good panel (liquid crystal element) is provided.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a perspective view showing a substrate used in a liquid crystal element according to an embodiment of the present invention. In the figure, 1 is a substrate such as glass, 2 is a transparent electrode such as ITO, 3 is a metal electrode such as aluminum, chromium, molybdenum, tantalum, etc., and 4 is a space between dry etched pixels. Transparent electrode 2 is 500-2
The thickness of the metal electrode 3 is 400 to 3,000, preferably 600 to 1,500, although it varies depending on the characteristics of the liquid crystal.
000 people thick.

In addition, the average surface roughness of the electrodes in the pixel area, which is the intersection of each electrode, is 60 Å or less, and the average surface roughness of the substrate area between the pixels without electrodes is 60 to 200 Å. The pitch is 200-5000 people.

FIG. 2 is a sectional view of a part of a panel (liquid crystal element) constructed by injecting liquid crystal between such substrates. In the figure, 1 to 4 are between the substrate 1 and the pixel 4, 5 is an insulating film for preventing short circuit between the upper and lower electrodes of the panel, and 6
7 is an alignment film for aligning liquid crystal, and 7 is a chiral smectic liquid crystal.

The insulating film 5 is provided on at least one substrate, and preferably has a thickness of 500 to 1,500 wafers in view of panel characteristics and dielectric strength. Further, it is preferable that the alignment film 6 has a thickness of 50 to 200 layers. As the insulating film 5, 5i
Oz@, Ta2os film, TiO2 film, etc. can be used. Furthermore, a material composed of SrTiO3, TiO2, and SrO can also be used, in which case Sr
The composition ratio of T i O3 and TiO2 is 1.7 to 1.8, T
It is preferable that the composition ratio of iO2 and SrO is 6 to 20.

Further, as the alignment film 6, a polyvinyl alcohol film, a polyimide film, a polyimide film, a polyester film, a polyamide-imide film, a polyester-imide film, etc. can be used.

Hereinafter, an example actually manufactured will be explained.

A 1.1 mm thick blue plate glass was used as the substrate 1, an ITO film was formed on it to a thickness of 1,500 mm by sputtering, a resist was applied and buttered, and the resist was left on. C up to 2×1O-2torr atmosphere
By dry etching between pixels in a vacuum with F, the average surface roughness of the electrodes in the pixel part is 60 Å or less, the average surface roughness between pixels is 100, and the average pitch of the roughness is 2250. A transparent electrode 2 having a human shape was formed.

Next, on top of this, a 5i02 film was formed as an insulating film 5 by a sputtering method to a thickness of 500 ml, and further on this, a polyimide film was formed as an alignment film 6 to a thickness of 100 ml using a spinner method.

Next, using two substrates on which electrodes etc. were formed in this way, they were subjected to a rubbing treatment so that the liquid crystals were uniaxially aligned.
Two substrates are bonded together so that the scanning electrode (one transparent electrode 2) and the signal electrode (the other transparent electrode 2) cross to form a panel, and chiral smectic liquid crystal is injected into this panel to form a second A liquid crystal display element, the cross section of which is shown in the figure, was manufactured.

The alignment between the pixels of the panel produced as described above was controlled, and the panel had good display quality without being disturbed within the range of normal use.

As in Example 1, a 1.1 mm thick blue plate glass was used as the substrate 1, an ITO film was formed on it to a thickness of 600 mm by sputtering, and then a resist was applied and patterned. This was dry-etched in a vacuum with CF4 and H2 introduced to an atmosphere of lXl0-2 torr, and the average surface roughness of the electrode in the pixel area was 60 Å or less, and the average surface roughness between the pixels was determined by 75 people. The average pitch of Sa is 55
Transparent electrode 2 was formed using 0 people. Next, on top of this, a Ta205 film was formed to a thickness of 500 mm as an absolute mWA5 by a sputtering method, and further on this, a polyimide film was formed as an alignment film 6 to a thickness of 50 mm by a spinner method. Next, using two substrates with electrodes formed in this way, they are rubbed so that the liquid crystal is uniaxially aligned, and then the two substrates are bonded together so that the scanning electrode and signal electrode cross each other. A panel was formed, and chiral smectic liquid crystal was injected into the panel to produce a liquid crystal display element.

The alignment between the pixels of the panel produced as described above was controlled, and the panel had good display quality without being disturbed within the range of normal use.

In this example, the surface roughness was measured using a scanning tunneling microscope (ST).
M, Nahoscope 11, sold by Toyo Technica Co., Ltd.). The average surface roughness was determined based on the standard deviation value.

[Effects of the Invention] As explained above, according to the present invention, the average surface roughness of the electrode within the pixel is set to 60 Å or less, and the average surface roughness of the substrate portion between the pixels is set to 60 to 200 Å. By controlling the average pitch of 200 to 5,000 pixels, the alignment state of the ferroelectric liquid crystal between pixels is controlled, reducing screen roughness and
Defects such as the remains of previous display patterns can be eliminated, and a panel (liquid crystal element) with good display quality can be provided.

In addition, in order to form the surface roughness between the pixels, a resist is left after the electrode etching and this is used as a mask to perform dry etching between the pixels, thereby manufacturing the panel in a simple process without adversely affecting the pixels. be able to.

[Brief explanation of the drawing]

FIG. 1 is an enlarged perspective view of a part of a substrate used in a liquid crystal device according to an embodiment of the present invention, and FIG. 2 is a part of a panel constructed using the substrate shown in FIG. The cross-sectional view and FIG. 3 are surface profile diagrams when the glass substrate surface condition between pixels (an area without opposing electrodes, corresponding to a so-called non-pixel area) was measured using a scanning tunneling microscope. 1: Transparent substrate, 2: Transparent electrode, 3: Metal electrode, 4: Roughened pixel space, 5: Insulating film, 6: Alignment film, 7: Ferroelectric liquid crystal.

Claims (3)

[Claims] (1) A ferroelectric liquid crystal, a pair of substrates facing each other with the ferroelectric liquid crystal placed between them, and a voltage applied to the ferroelectric liquid crystal formed on the pair of substrates so that each electrode crosses and faces each other. In a ferroelectric liquid crystal device that is equipped with two pairs of opposing electrode groups for driving, and in which the average surface roughness of the electrodes at the pixel portion where each electrode intersects is 60 Å or less, the surface roughness of the substrate portion between the pixels without electrodes is A ferroelectric liquid crystal element having an average surface roughness of 60 to 200 Å and an average pitch of the roughness of 200 to 5000 Å. (2) The electrode group is formed by etching using photoresist, and the roughness of the substrate part between pixels is formed by dry etching the part of the substrate between pixels while leaving the photoresist used for etching. A ferroelectric liquid crystal device according to claim 1. (3) An insulating film is provided between the ferroelectric liquid crystal and the electrode group, and the composition of the insulating film is SrTiO_3, TiO_2, and SrO.
The composition ratio of SrTiO_3 and TiO_2 is 1.7.
~1.8, and the composition ratio of TiO_2 and SrO is 6 to 2.
2. The ferroelectric liquid crystal element according to claim 1, wherein the ferroelectric liquid crystal element is 0.