JPS60244936A - Liquid-crystal display element - Google Patents

Abstract

PURPOSE:To increase a visual angle and to prevent unevenness of coloring by adding a small amount of P type dichroic pigment to a liquid-crystal element which has polarizing plates between two electrode substrates and contains a charged nematic liquid-crystal compound. CONSTITUTION:Maximum light transmission directions 2a and 2b and maximum light absorption directions 1a and 1b of the polarizing plates 3a and 3b are set perpendicularly to each other and liquid-crystal molecules 5 having the axial direction twisted by 90 deg. and P type dichroic pigment 7 are arrayed. A reflecting plate 6 is arranged under the polarizing plate 3b. When an electric field is applied to electrode substrates 4a and 4b, light in a direction A1 is absorbed partially by the pigment 7 and transmitted partially. Almost all light in a direction B1, on the other hand, is absorbed because the pigment 7 slants and part of it transmitted, so the light is seen black when viewed in the direction B1 and almost all light in a direction C1 is transmitted. Consequently, the visual angle is increased and unevenness of coloring is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a liquid crystal display element that displays characters, images, and the like.

Background technology Conventional, TN-FEM type (twisted nematic field effect type)
In liquid crystal display elements, two polarizing plates are used above and below the cell, so the viewing angle of the display section is narrow. Furthermore, since the liquid crystal layer is twisted by 90 degrees and the light leaks out, optical rotational dispersion occurs, resulting in coloring and uneven coloring.

FIG. 1 shows an off state in which no electric field is applied to the electrode substrates 4a and 4b, and FIG. 2 shows the electrode substrate 4a.

4b shows an on state in which an electric field is applied. Polarizing plate 3
The arrow 1aVi of a indicates the direction of the maximum absorption axis of light of the polarizing plate 3a, and the arrow 2a of the polarizing plate 3a indicates the direction of the maximum transmission axis of light of the polarizing plate 3a. Between the electrode substrate 4a and the electrode substrate 4b, liquid crystal molecules 5 are arranged with their axial directions twisted by 90 degrees. The arrow 1b of the polarizing plate 3b indicates the direction of the maximum light absorption axis of the polarizing plate 3b, and the arrow 2b indicates the direction of the maximum light transmission axis of the polarizing plate 3b. Reflecting plates 6 are arranged at intervals on the lower surface of the polarizing plate 3b.

When an electric field is applied to the electrode substrates 4a and 4b,
The liquid crystal molecules 5 are arranged as shown in FIG. In such an on state, the electrode substrate 4a.

Due to the limitation of the duty drive of the signal applied to the electrode substrates 4b and the influence of the anchoring effect of the interface, the liquid crystal molecules 5 generally have regions where their molecular axes are not perpendicular to the electrode substrates 4a, 4b. Therefore, as shown in FIG. 2, when observing the polarizing plate 3a in direction A and direction B, the display is visible in direction A, but not in direction B.

As described above, in the conventional liquid crystal display element, the viewing angle is narrow and coloring 2 occurs.

Purpose An object of the present invention is to solve the above-mentioned technical problems and provide a liquid crystal display element with a wide viewing angle and less uneven coloring.

Embodiment FIG. 3 is a sectional view of a TN-FEM type liquid crystal display element according to an embodiment of the present invention. A transparent conductive film 13 serving as a scanning electrode is arranged on the upper surface of the liquid crystal 14 by alignment treatment of the electrode surface. Further, on the lower surface of the liquid crystal 14, a transparent conductive film 15, which is a signal electrode, is oriented by an alignment process. A glass substrate 12 is provided on the top surface of the transparent conductive film 13, and a polarizing plate 11 is provided on the top surface of the glass substrate 12. A glass substrate 16 is provided on the lower surface of the transparent conductive film 15, and a polarizing plate 17 is provided on the lower surface of the glass substrate 16. On the lower surface of the polarizing plate 17, reflective plates 18 are provided at intervals. Note that the cell is formed from glass substrates 12 and 16, transparent conductive films 13 and 15, and liquid crystal 14.

This will now be explained with reference to FIGS. 4 and 5.

FIG. 4 shows an off state in which no electric field is applied to the electrode substrates 4a and 4b, and FIG. 5 shows the electrode substrate 4a.

4b shows an on state in which an electric field is applied. The electrode substrate 4a includes a transparent conductive film 13 and a glass substrate 12 shown in FIG.
It consists of The electrode substrate 4b consists of a transparent conductive film 13 and a glass substrate 16 shown in FIG. The liquid crystal molecules 5 and the P-type dichroic dye shown in FIG. 4 are included in the liquid crystal 14 shown in FIG. The composition of this liquid crystal 14 is different from conventional ones, and when designing the optimal cell, consider the concentration of dichroic dye, dichroic ratio, absorption spectrum, cell thickness, and degree of polarization or transmittance of the Δn1 polarizing plate of the liquid crystal. There is a need to.

For example, the cell thickness is about 7μm1 polarizing plate LC2-82-18 (
(Product name manufactured by Royal Electric Machinery Co., Ltd.) was used, and the black pigment was about 3% of a mixed yarn of anthraquinone yarn and azo yarn, and host liquid crystal E12 was used.
0 (BDH). The refractive index Δn of the host liquid crystal molecules is 0.15, and when multiplex driving was performed using this mixed system, a wider viewing angle than the conventional TN-FEM type liquid crystal display element was obtained.

Returning to FIG. 4, the arrow 1a of the polarizing plate 3a indicates the maximum absorption axis direction of the light of the polarizing plate 3a, and the arrow 2a indicates the maximum transmission axis direction of the polarized light &3a. Inside the liquid crystal between the electrode substrate 4a and the electrode substrate 4b, liquid crystal molecules 5 and P dichroic dye 7 are arranged with their axial directions twisted by 90 degrees. The arrow 1b of the polarizing plate 3b indicates the direction of the maximum light absorption axis of the polarizing plate 3b, and the arrow 2b indicates the direction of the maximum light transmission axis of the polarizing plate 3b. Reflecting plates 6 are arranged at intervals on the lower surface of the polarizing plate 3b. However, the polarizing plates 3a and 3b correspond to the polarizing plates 11 and 17 in FIG. 3, respectively. Further, the reflector 6 has a third
This corresponds to the reflecting plate 18 in the figure.

When an electric field is applied between the electrode substrates 4a and 4b,
The liquid crystal molecules 5 and the P total dichroic dye 7 are arranged as shown in FIG. This arrangement is, for example, as shown in FIG.

Next, referring to FIGS. 7 and 8, P total dichroic dye 7
I will explain about it. Figure 7 shows the arrangement of the P total dichroic dye 7 in the off state, and Figure 8 shows the arrangement of the P total dichroic dye 7 in the on state.
shows the array of As shown in FIG. 7, most of the light in direction A in the off state is absorbed by the P total dichroic dye 7. Arrow A indicates the electric field vector of light.

When on, as shown in FIG. 8, the light in the direction A1 is partially absorbed by the P dichroic dye 7 and partially transmitted. Also direction B
Most of the light No. 1 is absorbed because the P-type dichroic color layers 7 are arranged at an angle, and a portion of the light is transmitted. Therefore direction B1
When viewed from above, it appears black and the lighting display is confirmed. Direction C
Most of the light of 1 is transmitted through the P total dichroic dye 7.

Note that the dye concentration of P total dichroic dye 7 is a small amount (approximately 1 to 5%
). If the dye concentration is less than about 1%, the dye absorbs less light when on, and the black color in the blind area of the liquid crystal becomes lighter. Also, if the amount is more than about 5%, the black color becomes noticeable when off. Furthermore, by appropriately adjusting the mixing ratio of the black pigment, the coloring caused by the optical rotation of the liquid crystal can be made into an achromatic color or a color that is desirable to the eye.

By mixing the black P-type dichroic dye with the liquid crystal in this manner, the dichroic dye is similarly aligned in the alignment direction of the liquid crystal molecules. When the liquid crystal molecules tilt toward the perpendicular direction of the electrode substrate due to the electric field, the dye molecules also tilt.

In the display of a TN-FEM type liquid crystal display element, when this liquid crystal display element is viewed from the direction A shown in Fig. 2, which corresponds to the blind area of the viewing angle, the coloring of the pigment is visible, and the lit display part is visible even from direction A. can do. In addition, in the off state, the absorption axis of the polarizing plate and the absorption axis of the dichroic dye near the interface on the electrode substrate side that is in contact with the polarizing plate are parallel, and most of the light in the direction of the absorption axis is absorbed by the polarizing plate. As a result, the absorption effect of dichroic dyes is reduced, and the color is almost the same as without dyes. However, due to factors such as optical rotation and the degree of order of the dye, the dye becomes slightly colored.

Effects As described above, according to the present invention, the viewing angle is widened and uneven coloring is eliminated.

[Brief explanation of drawings]

Figures 1 and 2 show liquid crystal molecules 5 of a conventional liquid crystal display element.
FIG. 3 is a cross-sectional view (3) of a liquid crystal display element according to an embodiment of the present invention, and FIGS. 4 and 5 are diagrams showing the liquid crystal molecules 5 and P-type dichroism of the embodiment. 6 is an enlarged view of the liquid crystal molecule 5 shown in FIG. 5 and the P-type dichroic dye 7 near the reference mark 6A, and FIGS. 7 and 8 are P-type. FIG. 7 is a diagram illustrating a dichroic dye 7. 3 a, 3 b, 11, l 7 - polarizing plate, 4
a, 4b...electrode substrate, 5...liquid crystal molecule, 7...
P-type dichroism, 12.16...Glass substrate, 13.
15...Transparent conductive film, 14...Liquid crystal agent Patent attorney Kei Nishi Part 1 Figure 2 Figure 3

Claims (1)

[Claims] In a liquid crystal display element formed by including a cell formed by injecting a nematic liquid crystal composition between two electrode substrates and polarizing plates arranged on both sides of the cell, a small amount of the nematic liquid crystal composition is added to the nematic liquid crystal composition. A liquid crystal display characterized in that a P-type dichroic dye is added to make the long sleeve direction of the dye molecules at the electrode substrate interface parallel to the light absorption axis direction of the polarizing plate in contact with the electrode substrate. element.