JPH03134623A - Liquid crystal electrooptical element - Google Patents

Abstract

PURPOSE:To eliminate the inverting regions of the liquid crystal electrooptical element and to widen the visual angle thereof by forming the element in such a manner that the retardation of an optically anisotropic body has a fluctuation in a very small region. CONSTITUTION:An upper polarizing plate 101, a liquid crystal cell 102, the optically anisotropic body 103, a lower polarizing plate 104, and a reflecting plate 105 are provided. This liquid crystal cell 102 consists of a transparent substrate 121 which is formed with transparent electrodes 122 consisting of ITO having a prescribed film thickness on the surface and has extremely good flatness, an oriented layer 123 and a liquid crystal 124. The liquid crystal of DELTAn=0.15 is used for the liquid crystal 24 and is twist-oriented at 210 deg. counterclockwise from the upper substrate of the cell having 6.0mum cell gap d toward the lower substrate. The retardation DELTAnd of this time is 0.90mum. On the other hand, the optically anisotropic body 103 is formed by pressing a uniaxially stretched polycarbonate film having a prescribed thickness with a metallic plate having fine ruggedness and has 0.957mum retardation DELTAnd in average and the fluctuation in the very small region; therefore, the inversion of the liquid crystal electrooptical element is eliminated.

Description

[Detailed description of the invention] [Industrial use ￥V] The present invention relates to a liquid crystal electro-optical device.

[Conventional technology] Conventional new twisted nematic mode (hereinafter referred to as NT
(referred to as N mode) eliminates the display coloration characteristic of the conventional super twisted nematic mode.
As proposed in Japanese Patent Application No. 62-121701, a liquid crystal cell (hereinafter referred to as a display cell) for performing display and an optically anisotropic body are provided between a pair of polarizing plates.

Figure 3 shows a cross-sectional view of a conventional liquid crystal electro-optical element. In the figure, 301 is an upper polarizing plate, 302 is a liquid crystal cell (display cell), 303 is an optically anisotropic compensation film), and 304 is a lower polarizing plate. The liquid crystal cell 302 has a film thickness of 100 mm on the surface.
A transparent substrate 321 with extremely excellent flatness on which a transparent electrode 322 of 0A ITO is formed, an alignment layer 323, and a liquid crystal 324.
fM is constructed from . The liquid crystal 324 used is one with Δn=0.15, and the cell gap d is 6.0 μm.

The twisted orientation of At this time, the retardation Δnd
becomes 0.90μm. On the other hand, the optically anisotropic body 303 is
The retardation Δnd was set to 0.57 μm for a uniaxially stretched polycarbonate film having a thickness of 120 μm.

FIG. 4 shows a relationship diagram of each axis of a conventional liquid crystal electro-optical element. An angle 420 formed by the polarization axis (absorption axis) direction 410 of the upper polarizing plate and the rubbing direction 411 of the upper substrate of the display cell
45° to the left, twist angle 421 of the display cell to 210° to the left
The angle 422 formed by the rubbing direction 412 of the lower substrate of the display cell and the stretching direction 413 of the compensation film is 90 @ The stretching direction 413 of the compensation film is the polarization axis (absorption axis) of the lower polarizing plate.
The angle 423 formed with 414 was set to 45° to the left.

A conventional liquid crystal electro-optical element manufactured under the above conditions exhibits electro-optic characteristics with extremely little coloration when observed from a direction perpendicular to the panel surface.

[Problems to be Solved by the Invention] However, the conventional liquid crystal electro-optical device using the NTN mode has a problem that the viewing angle range (hereinafter simply referred to as viewing angle) in which the display can be recognized well is narrow. Figure 6 shows the viewing angle characteristics of a conventional liquid crystal electro-optical element.The center of Figure 6 is perpendicular to the panel surface, and the outer circles, starting from the inside, are each tilted at an angle of 10° 20'' from the vertical direction. 30
″ indicates the direction of 40° 50° 60°. Also,
The four directions of top, bottom, left and right in the figure correspond to the four directions shown in FIG. Here, 601, 602, and 603 are equal contrast lines with a contrast ratio of 5.10.20, respectively. Further, a shaded area 604 is an area where the contrast ratio becomes 1 or less and the display is inverted.

As described above, the conventional liquid crystal electro-optical element using the NTN mode has a narrow viewing angle, especially in the upward direction, because the amount of light when not selected changes greatly depending on the viewing angle direction, causing display inversion. This inversion of the display is a major factor in psychologically making the viewing angle seem narrower.

The present invention is intended to solve these problems, and its purpose is to provide a liquid crystal electro-optical element with a wide viewing angle.

[Means for Solving the Problems] The liquid crystal electro-optical device of the present invention includes a liquid crystal cell comprising a twistedly oriented liquid crystal sandwiched between two electrode substrates facing each other, and at least one optically anisotropic layer other than the liquid crystal. A liquid crystal electro-optical element comprising a polarizing plate and a pair of polarizing plates disposed on both sides of the polarizing plate, characterized in that the polarization Δnd of the optically anisotropic body has variations in a minute region. .

Further, the display device is characterized in that a reflecting plate is provided on the outside of one of the pair of polarizing plates, and the display is used in a reflective display mode.

[Function] It has been common practice to construct fishing gear using a rectangular beam tarp zone Δnd with excellent uniformity. In the NTN mode, the elliptical polarization of the display cell is returned to circular polarization using an optical anisotropic body to enable black and white display, so complete compensation cannot be achieved unless the Δnd of the display cell and the optical anisotropic body match. . For this reason, if there is a variation in Δnd in the display cell or the optically anisotropic body, leakage light occurs during non-selection and the contrast ratio decreases. Figure 7 shows how the contrast ratio in the vertical direction of the panel changes when a variation in Δnd is generated in a minute area of an optically anisotropic object.
In the figure, 701, 702, 703, and 704 are equal contrast lines with a contrast ratio of 2.5, 10.20, respectively. Further, a shaded area 705 is an area where the contrast ratio becomes 1 or less and the display is inverted. As can be seen from this figure, the larger the dispersion of retardation Δnd in the minute region of the optically anisotropic object, the lower the contrast ratio when observed from near perpendicular to the panel surface. The larger the dispersion of the tarpaulin Δnd, the narrower the area to be inverted.
When the variation in retardation Δnd is ±50 nm or more, there is no region where the display is inverted at all. Therefore, if the compensation film has a variation in the tarpaulin Δand of ±50 nm or more in a minute region, a liquid crystal display element with a wide viewing angle in which the display is not inverted even when viewed from above can be obtained. However, the contrast ratio decreases due to variations in the tardsilon Δnd, making it impractical as a transmissive display element.Therefore, a reflective plate is placed on one side of the liquid crystal electro-optical element, and this liquid crystal display element is The 0 reflective display mode used in the reflective display mode is
Since the incident light on the liquid crystal panel passes through the liquid crystal electro-optic element twice through the reflection plate, a contrast ratio that is approximately the square of the contrast ratio obtained in the transmissive display mode is obtained. That is, when a liquid crystal electro-optical element having a contrast ratio of 5 when used in a transmission type is used in a reflection type, the contrast ratio is improved to about 25. Even this wide-viewing-angle liquid crystal electro-optical element, which has a low contrast ratio due to variations in the tarpaulsion Δnd in the minute regions of the compensation film, can still provide a sufficient contrast ratio if used as a reflective type.

Hereinafter, the details of the present invention will be shown by examples.

[Example] (Example 1) In Figure 1, which shows a cross-sectional view of a liquid crystal electro-optical element manufactured as an example of the present invention, 101 is an upper polarizing plate;
2 is a liquid crystal cell (display cell), 103 is an optically anisotropic body (compensation film), 104 is a lower polarizing plate, and 105 is a reflecting plate. The liquid crystal cell 102 has an ITO film with a thickness of 1000A on the surface.
It is composed of a transparent substrate 121 with extremely excellent flatness on which a transparent electrode 122 is formed, an alignment layer 123, and a liquid crystal 124. The liquid crystal 124 used had Δn=0.15, and was twisted counterclockwise by 210° from the upper substrate to the lower substrate of the cell with a cell gap d of 6.0 μm. At this time, the retardation Δnd becomes 0.90 μm. On the other hand, the optically anisotropic body 103 was produced by pressing a uniaxially stretched polycarbonate film with a thickness of 120 μm with a metal plate having fine irregularities. The optically anisotropic beam tarpion Δnd is 0.57 μm on average, and has a variation of about ±50 nm in a micro region.

FIG. 2 shows a relationship diagram of each axis of the liquid crystal electro-optical element of the present invention. An angle 22 formed by the polarization axis (absorption axis) direction 210 of the upper polarizing plate and the rubbing direction 211 of the upper substrate of the display cell
0 to the left 45” Display cell torsion angle 221 to the left 210°
The angle 222 formed by the rubbing direction 212 of the lower substrate of the display cell and the stretching direction 213 of the compensation film is 90 @ The angle 223 formed by the stretching direction 213 of the compensation film and the polarization axis (absorption axis) 214 of the lower polarizing plate is left 45 °.

The liquid crystal display element having a diagonal of 10 inches thus manufactured exhibits viewing angle characteristics as shown in FIG.

In the figure, 501, 502, and 503 are equal contrast lines with a contrast ratio of 5.10.20, respectively.

The four directions of top, bottom, left and right in the figure correspond to the four directions shown in FIG. Since this liquid crystal display element has no display reversal, it was possible to display images with a wide viewing angle.

[Effects of the Invention] As described above, according to the present invention, there is no region where the liquid crystal electro-optic element is inverted, and the viewing angle is widened.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a liquid crystal electro-optical element in one embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the respective axes of a liquid crystal electro-optic element in one embodiment of the present invention. FIG. 3 is a cross-sectional view of a conventional liquid crystal electro-optical element. FIG. 4 is a diagram showing the relationship between the axes of a conventional liquid crystal electro-optical element. FIG. 5 is a diagram showing viewing angle characteristics of a liquid crystal electro-optical element in an embodiment of the present invention. FIG. 6 is a diagram showing viewing angle characteristics of a conventional liquid crystal electro-optical element. FIG. 7 is a diagram showing the variation in Δnd in a minute area of the compensation film and the viewing angle characteristics in the vertical direction. 101, upper polarizing plate 102, liquid crystal cell (display cell) 103, optical anisotropic body (compensation film) 104, lower polarizing plate 105, reflection plate 121, transparent substrate 122. Transparent electrode 123, alignment layer 124, liquid crystal 210, polarization axis (absorption axis) 211 of the upper polarizing plate, rubbing direction 212 of the upper substrate of the display cell, rubbing direction 213 of the lower electrode substrate of the display cell, stretching direction of the compensation film 214, the angle 221 between the polarization axis (absorption axis) 220 of the lower polarizing plate, the polarization axis (absorption axis) 210 of the upper polarizing plate and the rubbing direction 211 of the upper substrate of the display cell, the twist angle 222 of the display cell, the display Rubbing direction 212 of the lower electrode substrate of the cell
angle 223 between the stretching direction 213 of the compensation film and the polarization axis (absorption axis) 214 of the lower polarizing plate 301, upper polarizing plate 302, liquid crystal cell (display cell) 303, optical anisotropic body (compensation film) 304, lower polarizing plate 321, transparent substrate 322, transparent electrode 323, alignment layer 324, liquid crystal 410, polarization axis (absorption axis) 411 of upper polarizing plate, rubbing of upper substrate of display cell The direction 412, the rubbing direction 413 of the lower electrode substrate of the display cell, the stretching direction 414 of the compensation film, the polarization axis (absorption axis) 420 of the lower polarizer, and the polarization axis (absorption axis) 410 of the upper polarizer are the display cells. An angle 421 with the rubbing direction 411 of the upper substrate, a twist angle 422 of the display cell, a rubbing direction 412 of the lower electrode substrate of the display cell
An angle 423 between the stretching direction 413 of the compensation film and the polarizing axis (absorption axis) 414 of the lower polarizing plate 501° 502° 503° 601° 602° 603° 604° 701° 702° 703° 704° 705° Isocontrast line with contrast ratio 5 Isocontrast line with contrast ratio 10 Isocontrast line with contrast ratio 20 Isocontrast line with contrast ratio 5 Isocontrast line with contrast ratio 10 Isocontrast line with contrast ratio 20 Area where the display is reversed Isocontrast lines with a contrast ratio of 2 Isocontrast lines with a contrast ratio of 5 Isocontrast lines with a contrast ratio of 10 Isocontrast lines with a contrast ratio of 20 Areas where the display is inverted and above

Claims (2)

[Claims] (1) A liquid crystal cell consisting of a twistedly oriented liquid crystal sandwiched between two opposing electrode substrates, at least one layer of optically anisotropic material other than the liquid crystal, and a pair of liquid crystal cells disposed on both sides with the liquid crystal interposed therebetween. In a liquid crystal electro-optical element equipped with a polarizing plate,
A liquid crystal electro-optical element characterized in that the retardation Δnd of the optically anisotropic body has variations in a minute region. (2) The liquid crystal electro-optical device according to claim 1, wherein a reflective plate is provided on the outside of one of the pair of polarizing plates and used in a reflective display mode.