JPH10333121A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device suitable for multi-level display. SOLUTION: A rectangular pixel area 11 is formed by arranging a scanning electrode member 5 which has scanning electrodes 3 and an orientation film 4 formed in order on a transparent substrate 1 and a signal electrode member 6 which has signal electrodes 9 and an orientation film 10 formed in order on a transparent substrate 7 opposite each other across chiral nematic liquid crystal 12 so that those scanning electrodes 3 and signal electrodes 9 cross each other. This chiral nematic liquid crystal 12 initially has a twist structure and is applied with a voltage which causes Frederics dislocation in the initial state to have two metastable states which are different from the initial state because of the difference of a voltage which is applied afterward and further the thickness of the scanning electrodes 3 and/or signal electrodes 9 is varied in the pixel area 11 to make cell gas partially different.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory-type bistable liquid crystal display device including a chiral nematic liquid crystal capable of gradation display.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 6-34965 proposes a memory-type bistable liquid crystal display device using a chiral nematic liquid crystal, and has an initial alignment condition, two metastable states, and switching between the two. Describes a practical driving method. Also, JP-A-6-23075
No. 1 discloses a specific structure of a liquid crystal cell.

The above-mentioned memory-type bistable liquid crystal display device comprises:
In this method, ON (white) display and OFF (black) display are performed by switching between two metastable states. That is, switching between black display and white display is performed by the difference between the selection voltages applied after the reset voltage, and when the selection voltage is set smaller than the threshold value Vth1, a 360 ° state (φ ₀ + π)
On the other hand, when the selection voltage is set higher than the threshold value Vth2, the 0 ° state (φ ₀ −π) is realized.

Further, it is necessary to realize gradation display in order to perform color display. However, by setting a selection voltage between Vth1 and Vth2, a display in which both states are mixed becomes possible, and gradation display is possible. Becomes

[0005]

However, Vth1
There is a problem that it is difficult to control the mixing ratio of the two states by appropriately setting the voltage value between Vth2 and Vth2.

In addition, a region where both states coexist is close to each other,
When it spreads, there is also a problem that an unstable state of a stripe shape unrelated to a required display image is developed.

Accordingly, the present invention has been completed in view of the above circumstances, and an object thereof is to provide a liquid crystal display device suitable for gradation display.

Another object of the present invention is to provide a highly reliable liquid crystal display device in which a striped unstable state is not developed.

[0009]

According to the present invention, there is provided a liquid crystal display device comprising: a scanning electrode member in which a scanning electrode pattern in which a large number of scanning electrodes are arranged on a transparent substrate;
A signal electrode pattern in which a number of signal electrodes are arranged on a transparent substrate and a signal electrode member in which an alignment film is sequentially formed, and a chiral nematic liquid crystal is formed so that the scanning electrode pattern and the signal electrode pattern intersect. The chiral nematic liquid crystal has a twisted structure in an initial state, and a voltage that causes a Freedericks transition in the initial state is applied, and then applied. Different from the initial state due to the difference in voltage
A memory-type bistable type having two metastable states, wherein the thickness of the scanning electrode and / or the signal electrode in the pixel region is changed to partially change the cell gap. And

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A bistable liquid crystal display device according to the present invention will be described with reference to FIGS. 1A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention, and FIG. 1B is an enlarged plan view of a main part of a pixel region of the liquid crystal display device of the present invention.

In the liquid crystal display device of the present invention, 1 is a transparent substrate made of glass or the like, 2 is an insulating film made of SiO ₂ coated on the transparent substrate 1, 3 is a scanning electrode made of ITO or the like, and 4 is an alignment film. The scanning electrode member 5 is constituted by these components. In the other signal electrode member 6, 7 is a transparent substrate made of glass or the like, 8 is an insulating film made of SiO ₂ coated on the transparent substrate 7, 9 is ITO or the like. The signal electrode 10 is an alignment film. The alignment films 4 and 10 are made of polyimide, and the films are subjected to an alignment treatment by rubbing or the like.

The scanning electrode 3 and the signal electrode 9 are patterned so as to intersect with each other, and each intersection is formed into a rectangular pixel area 11 (for example, 300 μm × 300 μm). 6 is a chiral nematic liquid crystal 12 (a liquid crystal composition exhibiting a nematic phase at room temperature [ZLI-1557, manufactured by E. Merck Ltd.]).
And an optically active additive [E. Merck S-811]
And the helical pitch P is adjusted to 2.7 μm).

A sealing member for enclosing the chiral nematic liquid crystal 12 is provided between the two members 5 and 6 around the display area. Polarizing plates 13 and 14 are provided outside the transparent substrates 1 and 7. Are arranged.

According to the liquid crystal display device having the above-described structure, the chiral nematic liquid crystal has a twisted structure in an initial state, and the chiral nematic liquid crystal has a twisted structure in the initial state. 2 different
It becomes a memory-type bistable type having two metastable states. For example, the twist angle φ ₀ (= 1 in the initial state)
When the polarizing plates 13 and 14 have a positional relationship (crossed Nicols) such that the twisted state of φ ₀ + π (= 360 °) with respect to 80 °) becomes a dark state, the twist angle φ ₀ in the bright state.
−π (= 0 °).

Further, by forming a groove-like pattern in the scanning electrode 3 and the signal electrode 9 in parallel in the longitudinal direction and providing a portion having a different cell gap in each pixel region 11, each portion having a different d / p can be obtained. Form. For example, if d1 <d2, the magnitude relationship of d / p is in the order of >>>, and d / p
If 1 = d2, then >>=>.

Incidentally, d = 1.45 μm and d1 = 0.0
In the case of 2 μm, d2 = 0.04 μm, and P = 2.64 μm, the part: cell gap = 1.52 μm, d / p = 0.
Part 576: cell gap = 1.49 μm, d / p = 0.
Part 564: cell gap = 1.47 μm, d / p = 0.
557: cell gap = 1.45 μm, d / p = 0.
549 Thus, according to the liquid crystal display device of the present invention, the two metastable states and the selection voltage d for the mixed state of these two states.
When the / p dependence is measured, if there is a portion where d / p is different in one pixel region, two metastable states and a mixed state of these two states are simultaneously displayed in the one pixel region depending on how the selection voltage is selected. Thus, by changing the ratio between the metastable state and the mixed state of the two states, the transmittance can be appropriately changed, and gradation display can be performed by utilizing the difference in the transmittance.

FIG. 2 shows the d / p dependence of the selection voltage, and FIG. 3 shows the scanning side waveform and the signal side waveform of the applied voltage. Table 1 shows the relationship between the selection voltage and the display state.

[0018]

[Table 1]

Next, another example of the liquid crystal display device of the present invention is shown in FIGS.
As shown in FIG. The same parts as those in the liquid crystal display device shown in FIG. In these liquid crystal display devices, the magnitude of d / p for each portion of the pixel region 11 is set in accordance with the d / p dependence of the selection voltage, and the area ratio of these portions enables uniform gradation display. It is determined as follows.

In the liquid crystal display devices shown in FIGS. 11 to 15, as described above, if the region where the two states coexist is close to each other and widens, the stripe-shaped unstable state which is not related to the required display image is obtained. It is configured to solve the problem that the state is expressed.

For example, in FIG. 11, in each pixel region 11, a portion where a mixed region of both states is developed is surrounded by a portion where only a metastable state is developed. Pixel regions in which a mixed state exists can be isolated by a metastable state, and as a result, a striped unstable state does not appear.
FIG. 16 shows the d / p dependence of the selection voltage, and FIG. 17 shows the scanning side waveform and the signal side waveform of the applied voltage. Table 2 shows the relationship between the selection voltage and the display state.

[0022]

[Table 2]

Further, as in the liquid crystal display device of FIG. 15, each pixel region 11 may be divided by a partition wall 15, whereby the occurrence of a striped unstable state can be particularly suppressed.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements may be made without departing from the scope of the present invention. For example, a color liquid crystal display device provided with a color filter has a similar effect.

[0025]

As described above, according to the liquid crystal display device of the present invention, by changing the thickness of the scanning electrode and / or the signal electrode in the pixel region, a portion having a different cell gap is formed, whereby A liquid crystal display device suitable for tone display can be provided. And it was able to be provided so as to be suitable for a color liquid crystal.

Further, according to the liquid crystal display device of the present invention, an unstable state of a stripe shape is not exhibited, whereby a margin of cells and driving conditions can be expanded, and as a result, high reliability and high reliability can be achieved. A high-performance liquid crystal display device could be provided. In addition, by stabilizing the display in the intermediate state, gradation display can be easily performed, thereby providing a liquid crystal display device capable of high-precision display.

[Brief description of the drawings]

FIG. 1A is an enlarged longitudinal sectional view of a main part of a liquid crystal display device of the present invention,
B is an enlarged plan view of a main part of the pixel region.

FIG. 2 is a diagram of a selection voltage with respect to d / p of the liquid crystal display device of the present invention.

FIG. 3 is a waveform diagram on a scanning side and a signal side of the liquid crystal display device of the present invention.

FIG. 4A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention,
B is an enlarged plan view of a main part of the pixel region.

FIG. 5A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention,
B is an enlarged plan view of a main part of the pixel region.

FIG. 6A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention,
B is an enlarged plan view of a main part of the pixel region.

FIG. 7A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention,
B is an enlarged plan view of a main part of the pixel region.

FIG. 8A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention,
B is an enlarged plan view of a main part of the pixel region.

9A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention, FIG.
B is an enlarged plan view of a main part of the pixel region.

10A is an enlarged vertical sectional view of a main part of the liquid crystal display device of the present invention, and FIG. 10B is an enlarged plan view of a main part of a pixel region thereof.

11A is an enlarged vertical sectional view of a main part of the liquid crystal display device of the present invention, and FIG. 11B is an enlarged plan view of a main part of a pixel region thereof.

12A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention, and FIG. 12B is an enlarged plan view of a main part of a pixel region thereof.

13A is an enlarged vertical sectional view of a main part of the liquid crystal display device of the present invention, and FIG. 13B is an enlarged plan view of a main part of a pixel region thereof.

14A is an enlarged longitudinal sectional view of a main part of the liquid crystal display device of the present invention, and FIG. 14B is an enlarged plan view of a main part of a pixel region thereof.

15A is an enlarged vertical sectional view of a main part of the liquid crystal display device of the present invention, and FIG. 15B is an enlarged plan view of a main part of a pixel region thereof.

FIG. 16 is a diagram of a selection voltage with respect to d / p of the liquid crystal display device of the present invention.

FIG. 17 is a waveform diagram on the scanning side and the signal side of the liquid crystal display device of the present invention.

[Explanation of symbols]

 1, 7 Transparent substrate 2, 8 Insulating film 3 Scan electrode 4, 10 Alignment film 5 Scan electrode member 6 Signal electrode member 9 Signal electrode 11 Pixel region 12 Chiral nematic liquid crystal 15 Partition

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiro Motomura 999-3 Hayato-cho, Aira-gun, Kagoshima Pref.

Claims (1)

[Claims] A scanning electrode member in which a plurality of scanning electrodes are arranged on a transparent substrate and an alignment film are sequentially formed; and a signal electrode pattern in which a large number of signal electrodes are arranged on a transparent substrate. An alignment film and a signal electrode member sequentially formed are arranged so that the scanning electrode pattern and the signal electrode pattern intersect with each other and through a chiral nematic liquid crystal, and each intersection is defined as a pixel region. This chiral nematic liquid crystal has a twisted structure in the initial state, and applies a voltage that causes the Freedericksz transition to the initial state. After that, two metastable states different from the initial state due to the difference in the applied voltage are applied. In the liquid crystal display device having the above structure, the thickness of the scanning electrode and / or the signal electrode in the pixel region is changed to partially change the cell gap. A liquid crystal display device characterized by the above-mentioned.