JPH0713166A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To fix the points where discrination lines are generated by slit parts and to stabilize the generation of the boundary lines for orientation to different liquid crystal orientation states by providing the slit parts along the boundary parts of the different liquid crystal orientation states in respective pixels to at least one of the first electrode and the second electrode. CONSTITUTION:Lower electrodes 55 of a lower substrate 54 are rectangular and the boundaries b0 of the liquid crystal orientation state of a lower oriented film 60 are formed in the prescribed positions bisected in a longitudinal direction. Namely, the regions of the different orientation states shifting the rubbing direction by 180 deg. are formed within one pixel P. The running orientation regions shifting the rubbing directions b1 and c1 by 180 deg. with the boundary b0 bisecting the one pixel P as a boundary are similarly formed on the upper oriented film 53 on an upper substrate 51 as well. Further, the slit parts 61 are formed by each one pixel along the boundaries b0 of the different orientation states on the common electrode 52 of the upper substrate 51. On the other hand, black matrix layers 62, 59 are formed on the lower substrate 54 surface on the rear side of the lower electrodes 55 corresponding to the slit parts 61.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices mainly use nematic liquid crystal and can be roughly classified into two types of display systems, a birefringence mode and an optical rotation mode.

A birefringence mode display type liquid crystal display device using twisted nematic liquid crystal has a molecular arrangement twisted by 90 ° or more (called ST type) and has steep electro-optical characteristics, so that each pixel is Even if there is no switching element (thin film transistor or diode) for each, a large capacity display can be easily obtained by time-division driving.

On the other hand, a liquid crystal display element of the optical rotation mode is called a TN type, which has a molecular arrangement twisted by 90 ° and has a high response ratio of several tens of milliseconds and a high contrast ratio. By providing a switching element for each pixel, it is possible to realize a liquid crystal display element having a large display capacity and a high contrast and a high display property, for example, a TFT type display element.

In recent years, this TFT-liquid crystal display element performs gradation display, but when observed obliquely, such phenomena as display inversion, blackout, and white spots occur.

As a means for solving these problems, TDTN (two-region TN) is used by a method of improving the viewing angle dependency by using a liquid crystal display element in which two regions in which the rising directions of liquid crystal molecules are different by 180 ° are provided in one pixel. Has been proposed (see, for example, JP-A-64-88520). In addition, a splay alignment is used for the liquid crystal molecule alignment, and a DDTN (region division TN) that achieves the same effect as the above TDTN is obtained.
(Y.Koike, et, al., 1992, SID, p798) have been proposed. The purpose of these is to virtually eliminate the above-mentioned phenomenon by setting two regions, in which the viewing angle dependence of the applied voltage-transmittance characteristic is different, as one pixel.

In DDTN and TDTN, since a disclination line appears at the boundary of pixel orientation division at least when a voltage is applied, this may significantly deteriorate the display quality. Therefore, it is necessary to provide a light-shielding area such as a black matrix at the position where the disclination line appears to maintain the display quality. This disclination line basically appears at the alignment boundary, but the appearance position and width are often indefinite when a voltage is applied.

That is, FIGS. 5 and 6 conceptually show the alignment of liquid crystal molecules when a voltage is applied to the alignment boundaries in DDTN and TDTN. DD as shown in FIGS.
In the TN structure, the transparent electrode 2 is formed on the upper substrate 1, the low pretilt angle alignment film 3 is attached to the entire surface thereof, and the high pretilt angle alignment film 5 is further provided in a half region of each pixel p. Similarly, the lower substrate 6 is also provided with the transparent electrode 7, the low pretilt angle alignment film 8 and the high pretilt angle alignment film 9, and when the substrates 1 and 6 are opposed to each other, the low pretilt alignment film 3 and the high pretilt alignment film 3 are formed in a region of one pixel p. The pretilt angle alignment film 9 faces each other.

Both the high and low pretilt angle alignment films have the same rubbing direction (indicated by an arrow a, the twist is omitted for explanation). Therefore, when the liquid crystal is aligned, the both pretilt angle alignment films cause the liquid crystal alignment state which is just inverted in the region of one pixel. Here, the drawing conceptually shows the alignment state of the liquid crystal molecules M in a voltage applied state.

When no voltage is applied, the liquid crystal molecule alignment is almost the same all over the surface, so that the disclination line does not appear, which is not a problem.
When a voltage is applied, the disclination line d appears because the rising direction of liquid crystal molecules differs for each alignment region. In TDTN, as shown in FIGS. 6A and 6B, the rubbing process (arrows b and c) with the 180 ° -shifted direction is applied to the alignment film 12 on the same pixel p. In TDTN having a boundary in the liquid crystal molecule arrangement, the position where the disclination line d appears becomes a problem.
Here, in order to make the alignment process different in the pixel for both TDTN and DDTN, two kinds of alignment films are used, or in the rubbing process, a mask is provided as a cover for providing a region in which the pixel is not rubbed, As shown in the region DL2 of FIG. 5B, a step corresponding to the alignment film thickness is generated or a step corresponding to the mask thickness is generated, and the region D of FIG.
Like L4, the alignment force tends to weaken near the alignment boundary. Therefore, when the voltage is applied, the position where the disclination line d appears, that is, the liquid crystal molecule M
Boundary portions having different rising directions become indefinite due to weakening of the alignment force in the vicinity of the alignment treatment boundary portion, and appear at various positions, which is a problem.

In both DDTN and TDTN, an alignment treatment boundary portion between the upper and lower substrates (in the case of DDTN, the boundary of the alignment film type, in the case of TDTN, the boundary in the rubbing direction).
5A and FIG. 6 also when misalignment occurs in
As shown in the regions DL1 and DL3 of (a), the position where the disclination line d appears, that is, the boundary where the rising direction of the liquid crystal molecules is different is undefined, and appears at various positions, which is a problem. .

Further, even when a spacer is arranged near the boundary of the alignment treatment, the alignment of liquid crystal molecules in the vicinity of the spacer is disturbed. Therefore, especially when a voltage is applied, the position where the disclination line appears, that is, the liquid crystal molecule. Borders with different rising directions became indefinite and appeared at various positions, which was a problem.

[0013]

As described above, in the conventional liquid crystal display element, when performing gradation display, the viewing angle such as display inversion phenomenon due to the extreme value of the applied voltage-transmittance characteristic exists. There was a dependency. In addition, as a means for solving these problems, the rising direction of liquid crystal molecules is set within two pixels.
It has been proposed to eliminate the extreme value by providing more than one direction, but when voltage is applied, the position where the disclination line appears, that is, the boundary where the rising direction of the liquid crystal molecule is different becomes indefinite and various Appeared at the location, causing problems.

The present invention solves these inconveniences, and proposes a novel cell structure in which a position where the disclination line appears, that is, a boundary where liquid crystal molecules rise in different directions can appear at a predetermined position. It is a thing.

[0015]

The present invention is directed to a first electrode and a second electrode which are arranged to face each other so as to form a plurality of pixels, and a dielectric anisotropy which is arranged between these electrodes. In a liquid crystal display element comprising a liquid crystal layer made of a positive nematic liquid crystal and an alignment film provided on the electrode and aligning the liquid crystal layer into a plurality of different liquid crystal alignment states, at least a first electrode and a second electrode are provided. One is to obtain a liquid crystal display element having a slit portion along the boundary portion between the different liquid crystal alignment states in each pixel.

Further, the first electrode is a common electrode, the second electrode is a plurality of pixel electrodes having a switching element for each pixel, and a second electrode forming each pixel electrode of the first electrode. To obtain an active matrix drive liquid crystal display element having a slit portion at a position facing to.

Further, in the present invention, the black matrix layer is formed on the surface of at least one substrate corresponding to the slit portion.

[0018]

The operation of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 3 shows a DDTN device with a transparent stripe electrode 2
2, an upper substrate 21 provided with a low pretilt angle alignment film 23 and a high pretilt angle alignment film 24 that divide one pixel into two, a transparent stripe electrode 25, a low pretilt angle alignment film 26 and a high pretilt angle that divides one pixel into two. The lower substrate 28 provided with the alignment film 27 is opposed at an interval of 10 μm or less, and the liquid crystal layer 29 is sandwiched in this interval. The arrow a indicates the orientation direction, but the twisted state is omitted for simplicity of description.

In the electrode 22 of the upper substrate, a slit portion 30 having no conductive portion is formed along the boundary portion 24a of the high and low pretilt angle alignment films 23 and 24 in a region of one pixel of the upper substrate, for example, with a width of 5 μm. There is. Therefore, both electrodes 22, 25
When a voltage is applied between them, a horizontal component is generated in the electric field in the vicinity of the slit portion 30, and an oblique electric field is formed around the slit portion 30, and the electric force line e bends as shown in the figure. That is, the rising direction of the liquid crystal molecules M is different with the slit portion as the center. The figure shows an arrangement state in which the liquid crystal molecules M rise differently due to the oblique electric field.

As described above, when the structure of the present invention is used, even if a slight vertical displacement of the alignment treatment boundary portion or a decrease in the alignment force near the alignment treatment boundary portion occurs due to the action of an obliquely applied electric field, liquid crystal molecules The boundary in the rising direction of the electric field is determined by the boundary in the direction of the electric line of force e of the electric field. Therefore, the position where the disclination line appears is the slit portion 30.
Since it appears stably centering around, if a slight light shielding layer is provided at this position, the display quality will not be impaired.

As is apparent from the figure, since the electric field is applied obliquely in two different directions, even if the alignment regulating force on the surface of each substrate that can determine the tilt direction of the liquid crystal molecules is slightly weak, the liquid crystal will naturally move in the desired direction. It also has the effect of promoting the rise of the molecule.

In order to shield the discriminative line generated in the slit portion 30, the electrode 2 on the lower substrate surface is shielded.
The black matrix layer 31 is formed in the lower layer facing the slit portion of No. 5.

The case of TDTN is shown in FIG. An upper substrate 34 in which an alignment film 33 having a stripe electrode 32 with 180 ° different orientation directions b and c is laminated, and a stripe electrode 35 with 180 ° different orientation directions b and c on one pixel. The lower substrate 37 on which the alignment film 36 having the above is laminated is made to face, and the liquid crystal layer 38 is arranged between them. The stripe-shaped upper electrodes 32 and the stripe-shaped lower electrodes 35 are arranged at 90 ° intersections.

Although the intersection region of these electrodes is one pixel p, as shown in the figure, a slit without an electrode, that is, a slit portion 39 is formed along the boundary where the alignment state in one pixel of the upper electrode changes. Electrodes on both sides of the slit are connected to both ends of the slit by a connecting portion.

When a voltage is applied, an oblique electric field is generated around the slit portion 39. The influence of the oblique electric field on the liquid crystal molecules M is symmetrically different from each other around the slit portion, and the liquid crystal molecules M are aligned so as to be along the electric force lines e. Therefore, the disclination line is narrowly and stably generated. The black matrix layer 41 is provided on either of the substrates at the position where the disclination line is generated to absorb the disturbance of the transmitted light.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1 and 2 show an embodiment in which the present invention is applied to an active matrix drive type liquid crystal display device.

In the figure, a glass upper substrate 51 has a transparent common electrode 52 made of ITO on one surface and a polyimide upper alignment film (trade name AL-1051, made by Japan Synthetic Rubber) 53 deposited thereon. It is provided. On the other hand, on the lower substrate 54 of the glass, pixel electrodes 55 forming one pixel p are arranged in a mosaic pattern on the surface facing the upper substrate 51, and a signal line 56 and a gate line 57 are wired between them. Each pixel electrode 55
Has a switching element 58 composed of a TFT,
It is connected to the signal line 56 and the gate line 57. Lower substrate 5
A black matrix layer 59 that shields light is arranged in a region where the signal line 56, the gate line 57, and the switching element 58 on 4 are located. Further, a polyimide lower alignment film (trade name AL-1) is formed on the entire surface of the lower substrate 54 including the pixel electrode 55 surface.
051, made of Japan Synthetic Rubber) 60 is attached.

The lower electrode 55 has a rectangular dimension of 330 μm × 110 μm, and forms a boundary b 0 of the liquid crystal alignment state of the lower alignment film 60 at the position of the center 165 μm in the longitudinal direction that divides the rectangle into two. . That is, this embodiment is a TDTN type device, and the region p1 of different liquid crystal alignment state in which the rubbing processing direction is shifted by 180 ° in one pixel p,
form p2. The arrow b2 indicates the rubbing orientation direction of one region p1 and the arrow c2 indicates the rubbing orientation direction of the other region p2, which are formed on the same orientation film by two rubbing processes using a mask pattern of photoresist.

Similarly, for the upper alignment film 53 of the upper substrate 51, a rubbing alignment region in which the rubbing directions b1 and c1 are deviated from each other by 180 ° is formed within a pixel p at a boundary b0 that divides the pixel into two. These directions are the rubbing directions b1 and c1 of the upper alignment film 53 and the rubbing directions b2 and c of the lower alignment film 60.
The upper and lower substrates are opposed to each other at an interval of 5 μm so that 2 and 90 intersect.

Further, in this embodiment, the common electrode 5 on the upper substrate is used.
2, a slit portion 61 having a length of 110 μm and a width of 5 μm without a conductive portion is formed for each pixel along the boundary b0 of the different alignment states.

On the other hand, the lower electrode 5 corresponding to the slit portion 61
A black matrix layer 62 having a width of 20 μm is formed on the surface of the lower substrate 54 on the back side of No. 5 together with another black matrix layer 59.

The obtained upper and lower substrates 51 and 54 are sealed with a sealing agent to form a liquid crystal cell, and a nematic liquid crystal having positive dielectric anisotropy (trade name ZLI-2293, manufactured by Merck Japan Co., Ltd.) is used as a liquid crystal layer 63 between the substrates. The liquid crystal display device is obtained by arranging.

Using the liquid crystal display device of this embodiment, polarizing plates with crossed Nicols arrangement were placed on both sides, and the electro-optical characteristics were measured by changing the viewing angle. As a result, symmetrical and wide viewing angle characteristics were obtained, and the orientation was also improved. The disclination line generated at the boundary b0 is generated within the width of the inside of the slit portion, and the pattern of the black matrix layer having the minimum width can be sufficiently shielded to obtain good display quality.

Example 2 In the simple matrix type liquid crystal display device shown in FIG. 3, a device of DDTN type was formed.
When the element of this example was driven by multiplex and the electro-optical characteristics were measured by changing the viewing angle as in Example 1, a symmetrical and wide viewing angle characteristic was obtained as in Example 1, and the disclination line generated at the alignment boundary was obtained. Appeared only inside the slit portion, and good display quality was obtained.

(Comparative Example) A pixel alignment division type liquid crystal display device having a conventional structure in which the common electrode of the upper substrate has no slit portion in Example 1 was prepared, and a part of the pixels protruded from the black matrix layer. The disclination line was generated and the display quality was degraded.

[0037]

According to the present invention, in the pixel alignment division type liquid crystal display element, the occurrence position of the disclination line which appears is stably appeared at a desired position, and the display quality is not deteriorated. Further, even if the alignment regulating force is slightly weak, an alignment defect such as tilt reverse is less likely to occur.

It is needless to say that the present invention can obtain the same effect even if the switching element made of MIM is used, and the same effect can be obtained even if the display is colorized by using the color filters of the three primary colors. Not to mention getting it.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing an embodiment of the present invention.

FIG. 2 is a schematic sectional view for explaining the operation of the embodiment shown in FIG.

FIG. 3 is a schematic cross-sectional view of a TDTN element for explaining the operation of the present invention.

FIG. 4 is a schematic cross-sectional view of a DDTN element for explaining the operation of the present invention.

5A and 5B are schematic cross-sectional views illustrating a configuration of a conventional TDTN type liquid crystal display element and a disclination line generation position that appears.

6 (a) and 6 (b) are schematic cross-sectional views illustrating a configuration of a conventional DDTN type liquid crystal display element and an emerging disclination line generation position.

[Explanation of Codes] 51 ... Upper Substrate 52 ... Common Electrode 53 ... Upper Alignment Film 54 ... Lower Substrate 55 ... Pixel Electrode 58 ... Switching Element 59 ... Black Matrix Layer 60 ... Lower Alignment Film 61 ... Slit 62 ... Black Matrix Layer 63 ... Liquid crystal layer b0 ... Liquid crystal alignment state boundary

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Yamamoto 8 Shinsitada-cho, Isogo-ku, Yokohama, Kanagawa Stock company Toshiba Yokohama office (72) Inventor Ren Hato 8 Shinsugita-cho, Isogo-ku, Yokohama, Kanagawa Company Toshiba Yokohama Office

Claims (3)

[Claims] 1. A liquid crystal comprising a first electrode and a second electrode which are arranged to face each other so as to form a plurality of pixels, and a nematic liquid crystal which is arranged between these electrodes and has a positive dielectric anisotropy. A liquid crystal display element comprising a layer and an alignment film which is provided on the electrode and aligns the liquid crystal layer in a plurality of different liquid crystal alignment states, wherein at least one of the first electrode and the second electrode is in each pixel. 2. A liquid crystal display device having a slit portion along the boundary between the different liquid crystal alignment states. 2. A first electrode is a common electrode, a second electrode is a plurality of pixel electrodes having a switching element for each pixel, and a second electrode forming each pixel electrode of the first electrode. The slit portion is provided at a position facing the electrode.
The liquid crystal display element described in 1. 3. The liquid crystal display element according to claim 1, wherein a black matrix layer is formed on the surface of at least one substrate corresponding to the slit portion.