JP2001042347A - Liquid crystal display device with wide viewing angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the liquid crystal molecules in a liquid crystal layer of a liquid crystal display device so as to have various alignment directions in a simple production process and to increase the viewing angle of the liquid crystal display device. SOLUTION: The device consists of an upper glass substrate 1, a lower glass substrate 2, a liquid crystal layer 5 held between the upper glass substrate 1 and the lower glass substrate 2, a plurality of pixel electrodes 3 arranged in a matrix on the upper glass substrate 1 side of the liquid crystal layer 5, a common electrode 4 on the lower glass substrate side 2 of the liquid crystal layer 5, one or plurality of protruding parts 6 made of a dielectric material and formed on each pixel electrode 3, a controlling electrode 8 formed on each protruding part 6 and electrically insulated from the pixel electrode 3, and an alignment layer 7 covering the common electrode 4 and covering the face formed by each pixel electrode 3, protruding part 6 and controlling electrode 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display having a wide viewing angle. In particular, a TFT active matrix (ac
tive matrix) liquid crystal display.

[0002]

2. Description of the Related Art Liquid crystal displays have many advantages (eg, small volume and light weight) over cathode ray tube (CRT) displays, but have significant disadvantages:
The viewing angle of a liquid crystal display is much narrower than a CRT display. In order to improve this point, various liquid crystal displays have been developed. For example, IPS (In-Plane Switching) mode. However, the IPS mode has a disadvantage that the optical transmittance is much lower than that of the conventional TN (Twisted Nematic) mode. For this reason, IPS mode is not suitable for portable computers only for desktop computer applications.

In order to widen the viewing angle of the liquid crystal display, as another method, the liquid crystal molecules have various alignment directions by changing the alignment direction of the liquid crystal molecules in the liquid crystal layer. It spreads.

For example, FIGS. 6A and 6B are partial cross-sectional views of a conventional liquid crystal display developed by Fujitsu Limited.
This liquid crystal display comprises an upper glass substrate 1 and a lower glass substrate 2
, Pixel electrode 3, common electrode 4, liquid crystal layer 5, projection 6
And an alignment layer 7. According to FIG. 6A, when no voltage is applied between the pixel electrode 3 and the common electrode 4, or when the applied voltage does not exceed a certain threshold, the liquid crystal molecules of the liquid crystal layer 5 are arranged in the same direction. (Vertical direction in the figure). According to FIG. 6B, when the voltage applied between the pixel electrode 3 and the common electrode 4 exceeds a certain threshold, some liquid crystal molecules of the liquid crystal layer 5 are on the pixel electrode 3 and the common electrode 4. The arrangement direction was changed by the influence of the convex portion 6. This is because the arrangement direction of the liquid crystal molecules near the convex portion 6 is substantially orthogonal to the alignment layer 7. As a result, the liquid crystal molecules have various arrangement directions, and the viewing angle of the liquid crystal display is widened.

FIGS. 7A and 7B are partial cross-sectional views of another conventional liquid crystal display device developed by IBM Corporation. This liquid crystal display includes an upper glass substrate 1, a lower glass substrate 2, a pixel electrode 3, a common electrode 4, a liquid crystal layer 5, and an alignment layer 7. Among them, since the common electrode 4 is provided with the concave groove 9, the common electrode 4 has discontinuous portions. As shown in FIG. 7A, when no voltage is applied between the pixel electrode 3 and the common electrode 4, or when the applied voltage does not exceed a certain threshold, the liquid crystal molecules of the liquid crystal layer 5 are arranged in the same direction. 6A and FIG. On the other hand, when the voltage applied between the pixel electrode 3 and the common electrode 4 exceeds a certain threshold value, a part of the liquid crystal molecules of the liquid crystal layer 5 causes a non-uniform electric field (indicated by an arrow) due to the discontinuity of the common electrode 4. As shown in the figure), the arrangement direction changed. This is because the arrangement direction of the liquid crystal molecules is orthogonal to the direction of the electric field. As a result, the liquid crystal molecules had various arrangement directions, and the effect of widening the viewing angle was obtained.

FIG. 8 is a partial cross-sectional view of yet another conventional liquid crystal display developed by IBM Corporation. This liquid crystal display has an upper glass substrate 1, a lower glass substrate 2, a pixel electrode 3, a common electrode 4, a liquid crystal layer 5, a convex portion 6, and an alignment layer 7. This prior art can be considered as a combination of the two prior arts. In detail, convex part 6
And the non-uniform electric field (as shown by the arrow) due to the end of the pixel electrode 3, the liquid crystal molecules have various arrangement directions. Therefore, the effect of widening the viewing angle of the liquid crystal display is provided.

In the first and third prior arts, in order to control the direction in which liquid crystal molecules are arranged in the vicinity of the convex portion 6, the dielectric material forming the convex portion 6 needs to satisfy certain conditions. The rate, permittivity, shape, etc. are all limited.
In the second conventional technique, a concave groove 9 needs to be formed in the common electrode 4, so that the manufacturing process is complicated.

[0008]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a convex portion on a pixel electrode or a common electrode by a simple manufacturing process, a control electrode on the convex portion, and a control electrode for the control electrode. A wide-viewing-angle liquid crystal display characterized by controlling an arrangement direction of liquid crystal molecules in the vicinity of the convex portion by applying an appropriate voltage. As an advantage, there is no particular limitation on the characteristics of the dielectric material constituting the projection. In addition, the non-uniform electric field generated by the edge of the pixel electrode is used to control the direction in which liquid crystal molecules are arranged near the edge of the pixel electrode.

[0009]

As shown in FIG. 1, a wide viewing angle liquid crystal display according to a first embodiment of the present invention comprises an upper glass substrate 1, a lower glass substrate 2, and an upper glass substrate 1. A liquid crystal layer 5 sandwiched between the lower glass substrate 2, a pixel electrode 3 located on the upper glass substrate 1 side of the liquid crystal layer 5, and a common electrode 4 located on the lower glass substrate 2 side of the liquid crystal layer 5;
A convex portion 6 provided on the pixel electrode 3 and made of a dielectric material, a control electrode 8 provided on the convex portion 6 and electrically insulating the pixel electrode 3, a common electrode 4, and An alignment layer 7 covering a surface formed by the pixel electrode 3, the projection 6, and the control electrode 8.

Due to the shape of the convex portion 6, the voltage applied to the control electrode 8, and the non-uniform electric field (as indicated by the arrow) due to the end of the pixel electrode 3, various types of liquid crystal molecules in the liquid crystal layer 5 are formed. The control of having the arrangement direction controls the viewing angle of the liquid crystal display.

As shown in FIG. 2, a wide-viewing angle liquid crystal display according to a second embodiment of the present invention comprises an upper glass substrate 1, a lower glass substrate 2, and an upper glass substrate 1 and a lower glass substrate 2. A liquid crystal layer 5 interposed therebetween, a pixel electrode 3 located on the upper glass substrate 1 side of the liquid crystal layer 5, a common electrode 4 located on the lower glass substrate 2 side of the liquid crystal layer 5, and a The projection 6 is provided in an area corresponding to the pixel electrode 3 (an area surrounded by a broken line in FIG. 2) and is made of a dielectric material.
A control electrode 8 provided on the convex portion 6 and electrically insulating the common electrode 4 from the common electrode 4;
An alignment layer 7 covering a surface formed by the projections 6 and the control electrodes 8 together.

Due to the shape of the convex portion 6, the voltage applied to the control electrode 8, and the non-uniform electric field (as indicated by the arrow) due to the end of the pixel electrode 3, various types of liquid crystal molecules in the liquid crystal layer 5 are formed. The control of having the arrangement direction controls the viewing angle of the liquid crystal display.

[0013]

Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a detailed semiconductor structure of the convex portion 6 and its vicinity in the first embodiment. The protrusion 6 is made of a dielectric material, and is arranged on the pixel electrode 3. The control electrode 8 is formed by growing a conductor on the protrusion 6. 3 shows the amorphous silicon thin film transistor 13 including the passivation 131, the second first metal 32, the n ⁺ area 133, the amorphous silicon 134, the gate insulator 135, and the second first metal 36.

The overall structure shown in FIG. 3 requires six mask steps. On the other hand, the amorphous silicon thin film transistor 13 shown on the left side of FIG. 3 requires five mask steps. In the former case, there is one more mask than the latter, and the mask is formed on the insulator (convex portion) 6 by the conductor (control electrode) 8.
To grow.

FIG. 4 shows a semiconductor structure of a conventional liquid crystal display, and its left side 13 'is similar to the left side 13 in FIG.
The description is omitted. Referring to the right side 14 of FIG. 4, the first metal 15, the second metal 16, and the gate insulator 17 form a storage capacitor. By slightly modifying the semiconductor structure shown in FIG. 4, the structure of the projection and the control electrode of the present invention can be obtained. Referring to FIG. 5, ITO layer 24 functions as control electrode 8. The first metal 21, the second metal 22, the gate insulator 23, and the passivation 25 below the ITO layer 24 together form a convex portion. The semiconductor structure shown in FIG. 5 has two advantages: (1) the first metal 21, the second metal 22, and the gate insulator 23 have a common storage capacitor; (2) the number of masks required is five. Thus, the manufacturing cost can be reduced as compared with the semiconductor structure shown in FIG. 3 (the number of necessary masks is six).

In the above two embodiments, the thin film transistors 13 (FIG. 3) and 24 (FIG. 5) function as switches for driving the pixel electrodes. Further, the voltage applied to the control electrode 8 is the same as the voltage applied to the common electrode 4.

[Brief description of the drawings]

FIG. 1 is a diagram showing a partial cross-sectional view of a wide viewing angle liquid crystal display according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a partial cross-sectional view of a wide viewing angle liquid crystal display according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of the semiconductor structure in the first embodiment, showing a convex portion and an area in the vicinity thereof.

FIG. 4 is a cross-sectional view of a conventional semiconductor structure of a liquid crystal display having a convex portion.

FIG. 5 is a cross-sectional view of a semiconductor structure having protrusions according to a preferred embodiment of the present invention.

FIG. 6A is a partial cross-sectional view of a conventional liquid crystal display.

FIG. 6B is a partial cross-sectional view of a conventional liquid crystal display.

FIG. 7A is a partial cross-sectional view of another conventional liquid crystal display.

FIG. 7B is a partial cross-sectional view of another conventional liquid crystal display.

FIG. 8 is a partial sectional view of yet another conventional liquid crystal display.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper glass substrate 2 Lower glass substrate 3 Pixel electrode 4 Common electrode 5 Liquid crystal layer 6 Convex part 7 Alignment layer 8 Control electrode

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[Procedure amendment]

[Submission date] March 27, 2000 (2003.
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadamitsu Wei No.1 Xinxiang Township Road, Tainan Science and Technology Park, Tainan County, Taiwan HA04 HA07 JA26 JA34 JB57 JB69 KA05 NA01 NA27 PA02

Claims (4)

[Claims] A first substrate, a second substrate, a liquid crystal layer sandwiched between the first substrate and the second substrate, and a liquid crystal layer positioned on the first substrate side of the liquid crystal layer and arranged in a matrix. A plurality of pixel electrodes to be arranged, a common electrode located on the second substrate side of the liquid crystal layer, a plurality of convex portions provided on each of the pixel electrodes and made of a dielectric material, A plurality of control electrodes provided on and electrically insulated from each of the pixel electrodes;
An orientation layer covering the common electrode, and a surface formed by the respective pixel electrodes, the respective protrusions, and the respective control electrodes.The shape of each of the protrusions and a voltage applied to each of the control electrodes. Voltage and the non-uniform electric field due to the end of each pixel electrode,
A wide-viewing angle liquid crystal display, wherein the liquid crystal molecules in the liquid crystal layer are controlled to have various kinds of arrangement directions, thereby widening the viewing angle of the liquid crystal display. 2. The wide viewing angle liquid crystal display according to claim 1, wherein a voltage applied to each of the control electrodes is the same as a voltage applied to the common electrode. 3. A first substrate, a second substrate, a liquid crystal layer interposed between the first substrate and the second substrate, and a liquid crystal layer positioned on the first substrate side of the liquid crystal layer, the liquid crystal layer being arranged in a matrix. A plurality of pixel electrodes, a common electrode positioned on the second substrate side of the liquid crystal layer, and provided in each area on the common electrode corresponding to each pixel electrode, and formed of a dielectric material. A plurality of protrusions, provided on each of the protrusions,
A plurality of control electrodes that are electrically insulated from the common electrode, and an alignment layer that covers each of the pixel electrodes, and covers a surface that the common electrode, each of the protrusions, and each of the control electrodes form together. By the shape of each projection, the voltage applied to each control electrode, and the non-uniform electric field due to the end of each pixel electrode,
A wide-viewing angle liquid crystal display, wherein the liquid crystal molecules in the liquid crystal layer are controlled to have various kinds of arrangement directions, thereby widening the viewing angle of the liquid crystal display. 4. The wide viewing angle liquid crystal display according to claim 3, wherein a voltage applied to each of the control electrodes is the same as a voltage applied to the common electrode.