JPH02165126A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a sharp display and to improve the grade thereof by adding a guest dyestuff to a nematic liquid crystal, setting retardation small and setting the twist angle of the nematic liquid crystal in a specific range. CONSTITUTION:Oriented films 3, 4 consisting of polyimide films are deposited on the respective display electrodes of respective glass substrates 1, 2 and are respectively rubbed in 60 deg. directions A, B with each other. The nematic liquid crystal 5 formed by adding the guest dyestuff to a host liquid crystal is sealed between the oriented films 3 and 4. The guest dyestuff is added to the nematic liquid crystal and the twist angle of the nematic liquid crystal is set at 10 to 80 deg.. The retardation of the product DELTAn.d of the value DELTAn of the diffraction rate anisotropy of the nematic liquid crystal and the distance (d) of the spacing between two sheets of transparent substrates facing each other is set at 0.16 to 0.7. The dependency on visual angles is decreased in this way and in addition, the absorption of light is increased at the time of voltage off and the depen dency of the absorbancy on wavelength is decrease. The display grade is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a liquid crystal display device for displaying characters, figures, etc., and more specifically to the structure of a twisted nematic liquid crystal display device.

(b) Conventional technology Figure 5 is a schematic diagram of a conventional twisted nematic type liquid crystal display device.
A glass substrate on which display electrodes (not shown) made of O are formed is shown. Alignment films (13) and (14) are deposited on each display electrode of each glass substrate (i, 1) (i, 2), and rubbed in directions perpendicular to each other (directions E and F in Figure 5). has been done. A nematic liquid crystal (15) is sealed between the alignment films (13) and (14). Nematic liquid crystal (1
5) has a 90° twisted structure, and a small amount of cholesteric liquid crystal is added to the nematic liquid crystal (15) to prevent reverse tilt.

The outer surface of each glass substrate (11) (12) is provided with a polarizing plate (i
s) (t7) are provided, and polarizing plates (16) (17) are provided.
) are shown in FIG. 5G, 14, and are parallel to each other.

In a liquid crystal display device having such a configuration, transmitted light is blocked when the voltage is off, so a liquid crystal display device having such a configuration is called a normally C1ose.

(c) Problems to be solved by the invention Figure 6 shows 1. - The relationship between applied voltage and transmitted light intensity in the conventional liquid crystal display device as described in (hereinafter referred to as V-TItJ)
This is a graph showing the J line), and the graph (d) in the figure (
Graph (e) (shown with a dashed line) is the V-T curve in the direction of the preferred viewing angle of 30'', and the graph (f) is the V-T curve in the front direction (shown with a dashed line). ) show the V-T curves in the non-preferred viewing angle direction of 30°.As can be understood from Fig. 6, the V-T° concave curve characteristics are significantly different in the preferred viewing angle direction and the non-preferred viewing angle direction. (
(See FIGS. 6(e) and 6(f)), there is a problem in that the viewing angle dependence of the liquid crystal display device is large.

Furthermore, FIG. 7 is a graph showing the absorption spectrum when the electric field is turned off in a conventional liquid crystal display device.
It can be seen from the figure that the wavelength dependence of absorbance increases when the electric field is used as a factor, and as a result, conventional liquid crystal display devices have a problem of poor display quality.

The present invention was made in view of the above circumstances, and involves adding a guest dye to a nematic liquid crystal, setting the twist angle of the faceted nematic liquid crystal to 10° to 80°, and setting Δn-d (retardation) to 0. By setting the value between .16 and 0.712, viewing angle dependence can be reduced compared to conventional liquid crystal display devices, and the display quality is improved by increasing light absorption when the voltage is turned off and reducing the wavelength dependence of absorbance. The purpose of the present invention is to provide a liquid crystal display device that can perform the following functions.

(d) Means for Solving the Problems The liquid crystal display device according to the present invention comprises two transparent substrates each having a transparent electrode on the opposing inner surfaces, and a nematic film sealed between the two transparent substrates. In a liquid crystal display device having a liquid crystal and two polarizing plates, one of which is provided on the outer surface of each of the two transparent substrates, a guest dye is added to the nematic liquid crystal to increase the diffraction index difference of the nematic liquid crystal. Orientation value Δ
The product Δ of n and the distance d between the two opposing transparent substrates
Solve by setting nd to 0.16 to 0.7.

(Book) Function The liquid crystal display device of the present invention uses the guest-host effect and the twisted nematic effect to reduce viewing angle dependence and increase light absorption (good light shielding properties) when the voltage is turned off. reduce the wavelength dependence of

(F) Examples Hereinafter, the present invention will be specifically explained based on drawings showing examples thereof.

FIG. 1 is a schematic diagram showing an embodiment of a liquid crystal display device according to the present invention, and in the figure (1) and (2) are glass substrates on which display electrodes (not shown) made of ITO are formed. show. On each display electrode of each glass substrate (1) (2), an alignment film (3) < 4) made of a polyimide film is deposited, and the alignment film (3) < 4) is deposited on each of the display electrodes of each glass substrate (1) and (2), respectively, in a 60" direction (A, B direction in FIG. 1). It has been rubbed.

Between the alignment films (3) and (4), there is a host liquid crystal 5A-550.
A nematic liquid crystal (5) made by adding 5% of guest dye LCD-430 (manufactured by Nippon Kayaku Co., Ltd.) to No. 2 (manufactured by Chisso Corporation) is sealed. In addition, 0.3% of steryl nanoate was added to the nematic liquid crystal (5) in order to prevent reverse chill. The diffraction index anisotropy Δn of the nematic liquid crystal (5) is 0.060, and the layer thickness d is 6.1
μm, and the value of retardation Δn-d is 0.366
It is.

On the outer surface of each glass substrate (1) (2), a polarizing plate (6)
7) are provided respectively. The direction C of the absorption axis of the polarizing plate (6) on the incident light side and the direction of the absorption axis of the polarizing plate (7) are each set to be parallel to the rubbing direction B of the alignment film (4).

Next, the operation of the liquid crystal display device of the present invention having such a configuration will be explained.

In a twisted nematic liquid crystal display device, when the retardation Δn-d is reduced, the viewing angle dependence becomes smaller, but when Δn-d is set to 1 st, minimum (0,4
9) If the settings are below, the front contrast will decrease. Therefore, in the present invention, a guest dye is added to the nematic liquid crystal (5) in order to prevent this decrease.

Furthermore, when a guest dye is added to a twisted nematic liquid crystal display device in which Δn-d is L st,minimum or less, the absorption axis of one polarizing plate becomes the maximum when the voltage is off. Normally
The liquid crystal (
5) twist angle of 10° to 80° (60° in this example)
The alignment film treatment is performed so that Furthermore, in the present invention, the absorption axis directions C and D of the polarizing plates (6) and (7) are tfE O
In order to increase the brightness at the N time, they are arranged in parallel as in the conventional case. In addition, when Δn・d is large, the liquid crystal (5)
What is necessary is to increase the twist angle of .

FIG. 2 is a graph showing the V-7 curve in the liquid crystal display device of the present invention as described above, in which graph (a) (indicated by a broken line) is the V-7 curve in the front direction, and graph (b) is the V-7 curve in the front direction. (
Graph (C) (indicated by a two-dot chain line) is the V-7 curve in the direction of the preferred viewing angle of 30", and graph (C) (indicated by the two-dotted chain line) is the V-7 curve in the direction of the preferred viewing angle of 30".
The V-7 curves in the ° direction are shown, respectively. The liquid crystal display device of the present invention has less viewing angle dependence than the conventional one (see FIG. 6).

Moreover, FIG. 3 shows the absorption spectrum of the liquid crystal display device of the present invention when the voltage is turned off. The wavelength dependence of absorbance is small when the voltage is turned off.

FIG. 4 is a sectional view showing a display device for color display using the present invention.

FIG. 4 shows an active color display device, (21)
(22) is a glass substrate, (23) and (24) are color filters and counter electrodes formed on the glass substrate (21),
(25) is a pixel electrode that is formed on the glass substrate (22) and has an active element (not shown) and is fully arranged;
Although not shown in the drawings, alignment films are applied to each of the substrates (21) and (22) so that the twist angle of the liquid crystal (26) is 10'' to 80°.

If the present invention is applied to a color display device as shown in FIG. 4, it is possible to prevent light leakage, thereby providing a liquid crystal display device capable of realizing clear color display. In FIG. 4, (27) and (2B) are polarizing plates, and (26) is a liquid crystal.

Although the device for active color display has been described in FIG. 4, the present invention can also have similar effects when used in a device for simple matrix color display.

(G) Effects of the Invention As detailed above, in the liquid crystal display device of the present invention, a guest dye is added to a nematic liquid crystal, and the retardation Δ
Since the value of nd is set small, viewing angle dependence can be reduced, and the twist angle of the nematic liquid crystal is set between 10° and 80° according to the value of Δnd, so the wavelength of absorbance when the electric field is turned off can be reduced. Dependencies can be reduced, and as a result,
Contrast can be improved compared to the conventional method.

Moreover, if the present invention is used in a liquid crystal display device for color display, it is possible to provide a liquid crystal display device for color display with clearer color display and excellent quality.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the liquid crystal display device of the present invention, Fig. 2 is a graph showing the V-7 curve in the liquid crystal display device of the present invention, and Fig. 3 is a case where the voltage in the liquid crystal display device of the present invention is turned off. 4 is a cross-sectional view showing another embodiment using the present invention, FIG. 5 is a schematic diagram of a conventional liquid crystal display device, and FIG. 6 is a graph showing the absorption spectrum of a conventional liquid crystal display device. FIG. 7 is a graph showing an absorption spectrum when the voltage is turned off in a conventional liquid crystal display device. (1), (2)...Glass substrate, (3)...Alignment film, (5)...Nematic liquid crystal, (6), (
7)...Polarizing plate. Figure 1

Claims (1)

[Claims] 1. Two transparent substrates each having a transparent electrode on their opposing inner surfaces, a nematic liquid crystal sealed between the two transparent substrates, and each of the two transparent substrates. In a liquid crystal display device having two polarizing plates, one on each outer surface side, a guest dye is added to the nematic liquid crystal, and the two polarizing plates are opposite to the diffraction index anisotropy value Δn of the nematic liquid crystal. The product Δn·d of Δn·d with the interval dimension d of the transparent substrate is 0.16 to 0.
7, wherein the nematic liquid crystal has a twist angle of 10° to 80°. 2. The liquid crystal display device according to claim 1, wherein absorption axes of the two polarizing plates are arranged parallel to each other. 3. A color filter layer consisting of a plurality of R, G, and B filters is formed on the one transparent substrate, and a plurality of active elements corresponding to the plurality of R, G, and B filters are formed on the other transparent substrate. 2. The liquid crystal display device according to claim 1, wherein a predetermined color display is performed by turning on and off the active element. 4. The one transparent electrode formed on the one transparent substrate is formed in the column (or row) direction, and the other transparent electrode formed on the other transparent substrate is formed in the row (or column) direction. R is formed on one of the transparent substrates.
2. The liquid crystal display device according to claim 1, further comprising a color filter layer consisting of , G, and B.