JPH01923A - liquid crystal element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a liquid crystal element using ferroelectric liquid crystal and a thin film transistor as a switching element.

"Prior Art J" A liquid crystal element using a ferroelectric liquid crystal exhibiting a chiral smectic C phase is characterized in that the ferroelectric liquid crystal has a bistable state.
Because it has display memory properties and high-speed response, it is being applied to memory-type displays, high-speed shutters, etc., especially large-capacity displays that have a matrix pixel structure and require a large display area. It is suitably used for.

It is assumed that In a liquid crystal element that requires such a large display area, a thin film transistor is usually formed as a switching element for each pixel.

By the way, in such liquid crystal elements, in addition to making the spacing between the substrates (hereinafter referred to as cell gap) uniform, the cell gap is It is necessary to have a narrow gap of about 2 μm. As a means for forming a narrow gap of about 2 μm, it is conceivable to scatter spacers such as plastic beads or glass fibers with a diameter of about 2 μm between the substrates, thereby obtaining a desired cell gap.

"Problems to be Solved by the Invention" However, in the above-mentioned liquid crystal element, when a narrow gap of a predetermined thickness is formed between the substrates using spacers such as plastic beads, the diameter of the spacer itself is uneven and the distribution due to scattering. Due to the non-uniformity of the spacer, there is a possibility that gap unevenness may occur, which may adversely affect the display characteristics.Furthermore, there is a possibility that the spacer overlaps the thin film transistor and destroys the thin film transistor.

This invention was made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal element having a cell gap capable of ensuring bistable driving characteristics of a ferroelectric liquid crystal and having good display characteristics. It is.

"Means for Solving the Problems" In the present invention, a means for solving the above problems is to use a thin film transistor as a spacer between substrates, thereby making the cell gap a predetermined thickness.

Therefore, in the liquid crystal element of the present invention, since the thickness of the thin film transistor is formed with high accuracy, the cell gap becomes uniform over the entire area of the liquid crystal element, and the thickness of the thin film transistor can be set to a predetermined thickness. As a result, the cell gap becomes a narrow gap of, for example, 2 μm, which can ensure the bistable driving characteristics of the ferroelectric liquid crystal.

Hereinafter, the liquid crystal element of the present invention will be explained by its manufacturing method. Note that the liquid crystal element described here has a large number of pixel components each consisting of a pixel electrode and a thin film transistor formed in a matrix, and is applied to large-capacity displays and the like.

First, as shown in FIG. 1, a glass substrate 1 is
, 2 are formed with transparent electrodes 3 and pixel electrodes 4, 4, . . . made of ITO or the like, respectively.

In this case, as the glass substrates 1 and 2, polished glass plates with high flatness are usually used, but the present invention is not particularly limited thereto, and inexpensive unpolished glass plates may be used. Further, the pixel electrodes 4, 4, . . . are formed and arranged in a matrix.

Next, the glass substrate 2 on which the pixel electrodes 4.4...
Thin film transistors 5.5, . . . are formed on the inner surface of the pixel electrodes 4, 4, .

These thin film transistors 5, 5, . . . have a well-known configuration, and as shown in FIG. a first insulating film 7 formed covering
and a semiconductor film 8 formed on this first insulating film 7,
A source electrode 9 and a drain electrode IO formed on this semiconductor film 8, and these source electrode 9 and drain electrode! It consists of a second insulating film 11 formed to cover O, and a write shield 12 formed on the second insulating film 11 at a position directly above the gate electrode 6.

To fabricate such a thin film transistor 5, first, a gate electrode 6 made of molybdenum, chromium, etc. is formed, and then a film made of silicon nitride (SiNx) or the like is formed on the glass substrate 2 to cover the gate electrode 6. An insulating film 7 of No. 1 is coated. Next, a semiconductor film 8 such as hydrogenated amorphous silicon is formed to cover the first insulating film 7, and a source electrode 9 and a drain electrode 1O are further formed on this semiconductor film 8. After that, a second insulating film such as silicon nitride is applied to cover the source electrode 9 and drain electrode 10!
A thin film transistor 5 is obtained by forming a light shield 12 directly above the gate electrode 6. Here, each element constituting the thin film transistor 5.5... is formed with high precision in thickness or shape, and therefore the thin film transistor 5.5... formed by stacking these elements is uniform throughout. It has a thickness of In addition, these thin film transistors 5.5...
For example, the thickness of the first insulating film 7 is about 330 nm, the thickness of the semiconductor film 8 is about 250 nIl, the thickness of the source electrode 9 and the drain electrode 10 is about 560 r+ff+, and the thickness of the second insulating film 11 is about 550 nm. The thin film transistor 5 as a whole has a predetermined thickness of about 2 μm.

Next, as shown in FIG. 1, the side of the glass substrate 1 on which the transparent electrode 3 is formed is placed to face the glass substrate 2, and the thin film transistors 5.5... are used as spacers to separate the thin film transistors 5.5... The above-mentioned glass substrate 1 is placed on top of the glass substrate 1, and the outer periphery of the substrate is sealed and fixed with a sealing material (not shown) made of Evoquin adhesive or the like, and both substrates are pasted together to form a cell. In this case, the cell gap (more precisely, the thickness of the transparent electrode 3, pixel electrode 4.4...) is a constant value determined by the thickness of the spacer, that is, the thin film transistor 5.5... I take the.

Thereafter, a ferroelectric liquid crystal exhibiting a chiral smectic C phase is injected into the cell made of the glass substrate 1.2 to form a liquid crystal section 13, and a polarizing plate (not shown) or the like is provided in this cell to form a liquid crystal element. do. Here, as the ferroelectric liquid crystal, MBFt-8, MORA-8 or O3-1
014 (trade name; manufactured by Chisso Corporation), etc. are used.

In the liquid crystal element thus obtained, the plurality of thin film transistors 5.5 formed and arranged corresponding to each pixel electrode 4.4 are used as spacers, so that each thin film transistor 5.5. 5... are formed with high precision, so that the cell gap becomes uniform over the entire area of the liquid crystal element. Further, by setting the thickness of the thin film transistor 5 to a predetermined thickness, the cell gap can be increased by, for example, 2.
The gap can be made narrow enough to ensure bistable driving characteristics of the ferroelectric liquid crystal, such as μm. Furthermore, since the thin film transistors 5.5... are uniformly distributed and arranged corresponding to each pixel electrode 4.4..., for example, an unpolished glass plate with low flatness and undulations can be used as the glass substrate 1. .2, these glass substrates 112 are forcibly deformed by a plurality of thin film transistors 5.5 uniformly distributed, the undulations are corrected, and the inner surfaces of the glass substrates 1 and 2 are Therefore, a highly accurate cell gap can be ensured.

"Effects of the Invention" As explained above, since the liquid crystal element of the present invention uses a thin film transistor as a spacer between substrates, the thickness of the thin film transistor itself can be formed with high precision, so that the entire area of the liquid crystal element can be covered. As a result, the cell gap becomes uniform, and therefore it is possible to prevent deterioration of display characteristics due to gap unevenness. Furthermore, by setting the thickness of the thin film transistor to a predetermined thickness, the cell gap can be set to a narrow gap of, for example, 2 μm, which can ensure the bistable driving characteristics of the ferroelectric liquid crystal, and therefore a large area display is required. It can also be suitably used for large-capacity displays.

Furthermore, since spacers such as plastic beads are not used, production costs can be reduced by eliminating the process of dispersing these spacers, and there is also the possibility of unforeseen accidents such as the spacer overlapping the thin film transistor and destroying the thin film transistor. It can also be prevented.

[Brief explanation of the drawing]

1 and 2 show a specific example of a liquid crystal element according to the present invention. FIG. 1 is a schematic diagram of the structure of the liquid crystal element, and FIG. 2 is a schematic diagram of the structure of a thin film transistor. 1.2...Glass substrate, 3...Transparent electrode, t...Pixel electrode, 5...Thin film transistor, 13...Liquid crystal layer .

Claims (1)

[Scope of Claims] A liquid crystal element in which ferroelectric liquid crystal is injected into a gap between a pair of opposing substrates, and a thin film transistor is formed on at least one of the substrates, characterized in that the thin film transistor is used as a spacer between the substrates. A liquid crystal element.