JP2004325563A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element which is inexpensive and of which the viewing angle characteristics are simply and comparatively arbitrarily controlled with a simple structure. <P>SOLUTION: Electrodes 2a, 2b are disposed on mutually confronting surfaces of upper and lower substrates 1a, 1b interposing a liquid crystal layer 5 in between. The upper electrode 2a is made to be a transparent electrode and the lower electrode 2b is made to be a transparent electrode or a metal electrode. Opening parts (slits) 3a, 3b are arranged on the respective electrodes 2a, 2b. With respect to placement of the opening parts 3a, 3b, they are set up in such a way that respective distances between an opening part on one substrate and a plurality of opening parts on the other substrate adjacent to the opening part on the one substrate are not equal to one another. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention particularly relates to a liquid crystal display device having improved display contrast characteristics.
[0002]
[Prior art]
The liquid crystal display element realizes a uniform display basically by a uniform alignment treatment on the substrate surface. For this reason, in many cases, the display has a so-called viewing angle dependency, in which the appearance of display changes depending on the direction in which the element is observed. In most cases, the liquid crystal molecules represented by the TN mode are switched between upper and lower substrates to give an optical change.
[0003]
As a method of removing the above viewing angle dependency, a “multi-domain alignment method” has been proposed in which the liquid crystal molecule alignment inside the liquid crystal element is set to a plurality of directions. Various methods have been proposed as specific methods for realizing the alignment control method. The simplest method has been proposed in which an oblique electric field is generated between upper and lower substrates and the alignment is controlled by the electric field. I have.
[0004]
FIG. 7 shows an example of an element structure when two alignment directions are formed in a liquid crystal element. In the figure, reference numerals 1a and 1b denote upper and lower substrates made of glass or plastic, which have electrodes 2a and 2b on opposing surfaces, and each of the electrodes 2a and 2b is provided with openings 3a and 3b. 4a and 4b are alignment films, 5 is a liquid crystal layer, and 6a and 6b are polarizing plates.
[0005]
If openings 3a and 3b are provided in a part of the electrodes 2a and 2b, and the openings 2a and 2b are alternately arranged at certain intervals, a good two-part orientation can be obtained. In this case, it is particularly effective to use the vertical alignment mode as the liquid crystal operation mode.
[0006]
As an example of such improvement of the viewing angle, it has been proposed to widen the viewing angle range using an oblique electric field generated by providing a slit (opening) in an electrode (for example, see Patent Documents 1 and 2).
[0007]
[Patent Document 1]
Japanese Patent No. 3108768 [Patent Document 2]
Japanese Patent No. 3324926
[Problems to be solved by the invention]
By the way, the above-mentioned multi-domain method is characterized in that a good display state can be obtained even when the element is observed from any direction. However, depending on the application, it may be sufficient to observe only a certain direction. In the case of such an application, an element structure in which the above-described electrode openings are arranged at regular intervals cannot be used.
[0009]
In addition, even with the conventional mono-domain alignment treatment by substrate surface treatment, only a specific viewing angle characteristic can be formed, and it is considered that it is theoretically difficult to form an arbitrary viewing angle characteristic.
[0010]
The present invention has been made in view of the above-described problems, and has as its object to provide a liquid crystal display device that can control the viewing angle characteristic relatively easily and arbitrarily with an inexpensive, simple structure.
[0011]
[Means for Solving the Problems]
A liquid crystal display element according to the present invention is an upper and lower substrate having electrodes on opposing surfaces, and a liquid crystal display element having a liquid crystal layer sandwiched between the upper and lower substrates, wherein the electrodes are alternated between the upper and lower substrates. The slits are arranged such that the intervals between the slits on one substrate and a plurality of adjacent slits on the other substrate are not equal.
[0012]
The interval between adjacent slits on one substrate is 180 μm or less, preferably 120 μm or less. Further, the slit on one substrate is formed by dividing two adjacent slits on the other substrate by A: It is arranged at a position where it is divided by the ratio of B, and the ratio A: B is 5: 5 to 10: 0, preferably 6: 4 to 9: 1.
[0013]
The liquid crystal operation mode is a vertical alignment mode in which the pretilt angle of the central layer of the liquid crystal is 90 ° or a TN mode in which the pretilt angle of the central layer of the liquid crystal is 0 °. , In the plane, or not in the plane.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
The present invention provides a structure of a liquid crystal display element that can obtain relatively arbitrary viewing angle characteristics, has a high degree of freedom, and can be easily realized. In the conventional example, the openings formed in the upper and lower electrodes are arranged at regular intervals. However, in the present invention, it is possible to arbitrarily control the viewing angle characteristics by arranging the intervals at uneven intervals. I have to.
[0016]
FIG. 1 is a cross-sectional view showing a basic structure of a liquid crystal display device according to the present invention. The same components as those in FIG.
[0017]
In the figure, reference numerals 1a and 1b denote upper and lower substrates made of glass or plastic, having electrodes 2a and 2b on opposing surfaces, an upper electrode 2a being a transparent electrode, and a lower electrode 2b being a transparent electrode or metal. It is an electrode. Also, openings (slits) 3a, 3b are provided in each of the electrodes 2a, 2b. The openings 3a and 3b are arranged such that the intervals between the slits on one substrate and a plurality of adjacent slits on the other substrate are not equal. 4a and 4b are alignment films, 5 is a liquid crystal layer sandwiched between upper and lower substrates 1a and 1b, and 6a and 6b are polarizing plates.
[0018]
In the liquid crystal display device of the present embodiment, the openings 3a, 3b of the upper and lower electrodes 2a, 2b are arranged not at a fixed interval but at a bias as compared with the configuration of FIG. Then, the viewing angle characteristic can be arbitrarily controlled by the ratio between the intervals A and B shown in the figure.
[0019]
Here, the interval between adjacent openings on one substrate is 180 μm or less, preferably 120 μm or less. The opening on one substrate is arranged at a position where two adjacent openings on the other substrate are divided at a ratio of A: B, and the ratio A: B is 5: 5 to 10: 0, Preferably it is 6: 4 to 9: 1.
[0020]
The liquid crystal operation mode is a vertical alignment mode in which the pretilt angle of the central layer of the liquid crystal is 90 ° or a horizontal alignment mode in which the pretilt angle of the central layer of the liquid crystal is 0 °.
[0021]
Further, the ratio of A: B should be uniform in the plane or not uniform in the plane.
[0022]
Hereinafter, a simulation result of verifying whether or not the above-described viewing angle characteristic can be controlled will be described. This simulation was performed using a liquid crystal optical element simulator LCD MASTER 5 manufactured by Shintec Corporation.
[0023]
(1) Vertical alignment mode First, a description will be given of a simulation result when the liquid crystal operation mode is the vertical alignment mode. The structure of the liquid crystal display element was as shown in FIG. A 45-degree compensation viewing angle film (VAC-C180) 7 is inserted between the upper substrate 1a and the polarizing plate 6a. This viewing angle compensation film 7 is assumed to be VAC-C180 manufactured by Sumitomo Chemical.
[0024]
The upper and lower substrates 1a and 1b are glass substrates, the electrodes 2a and 2b are transparent electrodes, the opening directions of the openings 3a and 3b are from 90 ° to 270 °, and the alignment films 4a and 4b are vertical alignment films (central molecular pretilt angle of 90 °). ), The liquid crystal of the vertically aligned liquid crystal layer 5 used was Δε <0. The product Δnd of Δn of this liquid crystal and cell thickness was set to 0.6 μm. The upper polarizing plate 6a is a 45 ° polarizing plate (G1220DU), and the lower polarizing plate 6b is a 135 ° polarizing plate (G1220DU), which is assumed to be G1220DU manufactured by Nitto Denko.
[0025]
FIG. 3 is a graph showing an isoluminance curve in the vertical alignment mode. When the applied voltage at which the maximum contrast is obtained is assumed when 1/8 duty multiplex driving is assumed, the brightness when the interval A: B changes. 3 shows an equal luminance curve at the time of display. In the case of (a) where A: B was 5: 5, the luminance in the front was the highest and the symmetry in the left-right direction was good. It can be seen that, as this is changed to 7: 3 and 9: 1 as in (b) and (c), the maximum luminance viewing angle moves to the left direction in the figure.
[0026]
(2) TN mode Next, a description will be given of a simulation result when the liquid crystal operation mode is the TN mode. The structure of the liquid crystal display device was as shown in FIG.
[0027]
The liquid crystal of the liquid crystal layer 5 is a 90 ° TN liquid crystal. This liquid crystal material is assumed to be ZLI-4792 manufactured by Merck, and Δnd is set to about 0.49 μm. The pretilt angle is set so that the central molecule of the liquid crystal layer 5 is 0 °. Other configurations are the same as those in FIG.
[0028]
FIG. 5 is a diagram showing an isocontrast curve in the TN mode. When １ ／ duty multiplex driving is assumed, the voltage is set so that the transmittance when the front observation is OFF is 95% or more of the maximum transmittance. 3 shows an equal contrast curve when the interval A: B changes. In the case of (a) where A: B was 5: 5, the contrast in the vicinity of the front was the highest, and the symmetry in the left-right direction was good. It can be seen that the contrast distribution moves to a specific azimuth as this is changed to 7: 3, 9: 1, and 10: 0 as in (b), (c), and (d).
[0029]
As described above, it is clear that a favorable viewing direction can be changed by the ratio of the slit intervals A: B.
[0030]
Although the vertical alignment mode and the TN mode have been described above, the present method is applicable to all operation modes in which the pretilt angle of the liquid crystal layer center molecule is 90 ° or 0 °.
[0031]
Here, when real liquid crystal display elements of the vertical alignment mode and the TN mode are realized by the above-described method, it is important how to set the interval between the openings 3a and 3b of the electrodes 2a and 2b. That is, when the division ratio A: B is 5: 5, the upper and lower slit periods need to be 90 μm or less, preferably 60 μm or less, as already proposed in the above-mentioned document. Regarding this, it has been confirmed that when the ratio of A: B is changed, if A + B is set to 180 μm or less, preferably 120 μm or less, a good display state in appearance can be obtained. The same applies to the slit width, and it is desirable to set the slit width to 30 μm or less, preferably about 10 to 20 μm in consideration of the electrode aperture ratio.
[0032]
Since the aperture ratio when the slit width was set to 10 μm was about 80%, it was confirmed that the transmittance was not significantly reduced as compared with the case of the conventional mono-domain structure without using the slit structure.
[0033]
Also, in one liquid crystal display element, in the element structure as shown in FIG. 6, it is possible to set A: B to 5: 5 in the area G and to set 7: 3 in the area F by forming the electrode structure. Obviously, it can be implemented very simply.
[0034]
As described above, in the related art, relatively arbitrarily controlling the viewing angle characteristics has not been studied on the liquid crystal cell side, but has been performed by controlling the illumination angle of the backlight. In this method, the structure was complicated, and a film for controlling the light (such as 3M BEF) was expensive. However, as in the present embodiment, it is possible to control the viewing angle characteristic relatively easily and arbitrarily without any change in the other structure only by devising the electrode structure.
[0035]
Further, a plurality of areas having different viewing angle characteristics in the liquid crystal display element can be easily realized only by devising the electrode structure. Although a conventional method is possible, it will be apparent to those skilled in the art that the method of the present invention can realize such an element at the lowest cost.
[0036]
The present invention is applicable to all liquid crystal display elements (segment display, simple matrix drive dot matrix, active matrix liquid crystal display element including TFT drive, etc.).
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a liquid crystal display element that can control the viewing angle characteristics relatively arbitrarily and easily with an inexpensive, simple structure.
[0038]
That is, it is possible to control the viewing angle characteristics relatively easily and arbitrarily arbitrarily without changing the other structures at all only by devising the electrode structure.
[0039]
Further, a plurality of areas having different viewing angle characteristics in the liquid crystal display element can be easily realized only by devising the electrode structure.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a basic structure of a liquid crystal display device according to the present invention. FIG. 2 is a cross-sectional view showing a device structure in a vertical alignment mode. FIG. 3 is a diagram showing an equal luminance curve in a vertical alignment mode. FIG. 4 is a cross-sectional view showing an element structure in a TN mode. FIG. 5 is a view showing an equal contrast curve in a TN mode. FIG. 6 is a cross-sectional view showing another element structure in an embodiment. Sectional view showing structure [Description of reference numerals]
1a substrate 1b substrate 2a electrode 2b electrode 3a opening 3b opening 4a alignment film 4b alignment film 5 liquid crystal layer 6a polarizing plate 6b polarizing plate 7 viewing angle compensation film

Claims (7)

Upper and lower substrates provided with electrodes on opposing surfaces, and a liquid crystal display element having a liquid crystal layer sandwiched between the upper and lower substrates, wherein the electrodes are provided with slits arranged alternately between the upper and lower substrates, The liquid crystal display device according to claim 1, wherein the slits are arranged such that a distance between a slit on one substrate and a plurality of adjacent slits on the other substrate is not equal. 2. The liquid crystal display device according to claim 1, wherein an interval between adjacent slits on one substrate is 180 μm or less, preferably 120 μm or less. The slit on one substrate is arranged at a position that divides two adjacent slits on the other substrate at a ratio of A: B, and the ratio A: B is 5: 5 to 10: 0, preferably 6: 5. 3. The liquid crystal display device according to claim 1, wherein the ratio is 4 to 9: 1. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal operation mode is a vertical alignment mode in which a pretilt angle of a central layer of the liquid crystal is 90 degrees. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal operation mode is a TN mode in which a pretilt angle of a central layer of the liquid crystal is 0 °. 6. The liquid crystal display device according to claim 1, wherein the ratio of A: B is uniform in a plane. 6. The liquid crystal display device according to claim 1, wherein the ratio of A: B is not uniform in a plane.

Images