JPS6329726A - Liquid-crystal display element - Google Patents

Abstract

PURPOSE:To obtain a liquid-crystal display element which is wide in the visual angle range and has an excellent display quality, by making angles formed by the polarizing axis of each polarizing plate and the rubbing direction, by which arrangement of liquid crystal molecules is controlled, acute in the twisted direction of the liquid crystal molecules. CONSTITUTION:A liquid crystal cell which is formed by putting nematic liquid crystal 3, which is oriented to have an twisted angle of 180 deg., between electrode base plates 2 and 4 which are faced to each other, is formed and this display element is a yellowish-color polarizing plate which is used for, at least, one of a pair of deflecting plates 1 and 5 provided on both sides of the liquid crystal cell. The product DELTAn.d of the refractive index anisotropy DELTAn of the nematic liquid crystal of this display element and the thickness (d) of the liquid crystal layer is set at <=0.93. Moreover, the angle (a) formed by the polarizing axes 1a and 5a of the pair of polarizing plates 1 and 5 in the visual angle direction of the display element is set at 70 deg.<a<110 deg. and the angles b and b' formed by the polarizing axes 1a and 5a and rubbing directions 2a and 4a in the twisted direction of liquid crystal molecules are set to acute angles.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a liquid crystal display element, and more particularly to a liquid crystal display element in which the twist angle of twisted oriented liquid crystal is 1800 and utilizes the birefringence effect thereof.

<Prior Art> Liquid crystal display elements generally consist of a glass substrate, on which an electrode pattern made of tin oxide or indium oxide is formed, and a metal oxide film or organic polymer film on which the liquid crystal is aligned. Two sheets are placed facing each other with a spacer interposed between them, liquid crystal is injected into the gap, and the peripheral portion is sealed with a sealing material to form a liquid crystal cell. Polarizing plates are placed on both the upper and lower sides of this liquid crystal cell to provide electro-optic properties. Furthermore, liquid crystals are given a twisted orientation, and this twisted orientation can be achieved by, for example, rubbing the surface of an alignment film such as a metal oxide film or an organic polymer film on a substrate in one direction with a cloth or the like;
This is done by a so-called rubbing method. That is, the twisted alignment of the liquid crystal is created by placing two substrates that have been aligned by a rubbing method so that their respective rubbing directions, that is, the twisted alignment directions, intersect at 90 degrees. At this time, the liquid crystal molecules adopt a molecular arrangement in a spiral structure rotated by 90'' between the opposing electrode substrates.A liquid crystal display element with such a configuration is called TN (Twisted
This is called a nematic type liquid crystal display element.

However, in the TN type liquid crystal display element, the response with respect to liquid crystal molecule rearrangement was not good, that is, the response was poor in steepness, and as a result, the time division characteristics were extremely poor.

In order to solve this problem, a liquid crystal display element that utilizes the birefringence effect of liquid crystal has been proposed. In other words, the birefringence effect of the liquid crystal is enhanced by further twisting the twisted orientation of the liquid crystal by 90'' or more.
er-twisted BirefringenceE
This is called a ffect) type liquid crystal display element, and because the liquid crystal has excellent steepness, the time division characteristics are significantly improved.

However, in this SBE type liquid crystal display element, due to its birefringence effect, the refractive index anisotropy Δn of the liquid crystal and the thickness d of the liquid crystal layer
A slight difference in the product Δn-d results in a markedly different color tone. For this reason, the display is made into a negative display, which is then inverted to a positive display on the circuit side. For example, in a transmission type SBE type liquid crystal display element, at least one of a pair of polarizing plates is a yellow color polarizing plate, and the absorption axis or polarization axis of the polarizing plate is set so as to obtain a negative display. . At this time, the display will be yellow on a brown background, but by inverting the display on the circuit side and displaying brown on a yellow background, the color tone change peculiar to SBE type liquid crystal elements can be prevented. can.

<Problems to be Solved by the Invention> However, in the SBE type liquid crystal display element as described above, there may be differences in the appearance of color tone unevenness, angular dependence of color tone, viewing angle range, etc. depending on the setting conditions of each part. Therefore, there was a problem in that it was difficult to stably obtain good display quality.

Means for Solving the Problems〉 As a result of intensive research aimed at solving the above-mentioned problems in SBE type liquid crystal display elements, the present inventor has discovered that SBE type liquid crystal display elements
When at least one of the polarizing plates arranged on both sides of a liquid crystal cell is a yellow color polarizing plate, the product Δn of the refractive index anisotropy Δn of the liquid crystal in the liquid crystal cell and its thickness d
The value of -d, the crossing angle between the polarizing axes of a pair of polarizing plates toward the viewing angle direction, and the angle between the polarizing axis of each polarizing plate and the rubbing direction are related to the angle dependence of one color tone and the degree of unevenness in tone. The present invention was achieved by discovering that this has a large effect on the viewing angle range.

That is, the present invention is shown in FIG. 1 corresponding to the embodiment.

As shown in FIG. 2, electrode substrates 2.
A liquid crystal cell is formed by sandwiching an oriented nematic liquid crystal 3 with a twist angle of 180'' between 4, and at least one of a pair of polarizing films 5 disposed on both sides of the liquid crystal cell is yellow. In a display element that is a system color polarizing plate, the product Δn-d of the refractive index anisotropy Δn of the nematic liquid crystal 3 and the thickness d of the liquid crystal layer is set to 0.93 μm or less.

The crossing angle a of the polarizing axes 1a and 5a of the pair of polarizing plates 1.5 toward the viewing angle direction of the display element is more than 70° and less than 110°, and in the twisting direction of the liquid crystal molecules, It is characterized by the fact that the angles b' formed by the polarization axes 1a and 5a and the rubbing direction (arrows 2a and 4a in FIG. 2) are acute angles.

Here, if the angles and b' exceed 90 degrees, the display contrast will deteriorate and it cannot be used for practical use.
It has been found that when Δn-d exceeds 0.93 μm, other conditions for obtaining good display quality are satisfied and the width becomes narrow.

<Example> Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing the configuration of an embodiment of the present invention.
3 and 3 are explanatory diagrams showing the relationship between the polarizing axes 1a, 5a and the rubbing directions 2a, 4a, viewed from the upper polarizing plate 1 side.

A twisted oriented nematic liquid crystal 3 having a twist angle of 180° is sandwiched between upper and lower electrode substrates 2 and 3, forming a liquid crystal cell. On both sides of this liquid crystal cell, there is an upper polarizing plate 1 and a lower polarizing plate 5.
will be placed. A baffle light 6 is provided on this lower polarizing plate S side.

To manufacture a liquid crystal cell, first, an electrode pattern made of tin oxide and indium oxide is formed on a glass substrate, and then a polyimide-based organic polymer film for aligning the liquid crystal, that is, an alignment film is formed on this. The surface of this alignment film is subjected to alignment treatment by a rubbing method to produce electrode substrates 2 and 4. The angle formed by the rubbing directions of these electrode groups Fi2 and 4 is 180
When facing each other so that the distance is 0, the gap between them is 7 to 8 μm.
Attach them together with a spacer in between so that the distance between them is constant. Then, liquid crystal is injected and sealed into this gap. At this time, the liquid crystal to be injected has a product Δn-d of its refractive index anisotropy Δn and the liquid crystal layer thickness d after injection of 0.93 μm or less. shall be.

Yellow color polarizing plates are used for the upper and lower polarizing plates 1 and 5 disposed on both sides of the liquid crystal cell. or,
Only the upper polarizing plate 1 may be a yellow color polarizing plate, and the lower polarizing plate 5 may be a neutral gray polarizing plate.

In the above configuration, upper and lower polarizing plates 1 and 5
Experiments were conducted by variously changing the relationship between the polarization axes 1a and 5a of the electrode substrates 2 and 4 and the rubbing direction of the electrode substrates 2 and 4. That is, as shown in FIG. 2 or 3, the polarization axis 1
The angles in the liquid crystal twisting direction formed by rubbing directions 2a and 4a on the viewing angle side of a and 5a are b and b'
The intersection angle of each polarization axis 1a, 5a in the visual direction is a
As a result, color tone unevenness, color tone angular dependence, viewing angle range, and display quality were evaluated with the naked eye.

As a result, as mentioned above, good contrast could not be obtained unless the angle b' was an acute angle. The evaluation results of combinations that were able to obtain a certain level of display contrast are shown in the table. In addition,
In this [table], as shown in Fig. 2, the angle from the rubbing direction 2a toward the viewing angle direction to the polarization axis 1a is defined as positive, and when the arrangement is as shown in Fig. 3, it is defined as negative. It is shown in Similarly, the angle b' is positive in the arrangement shown in FIG. 2 and negative in the arrangement shown in FIG.

As for the evaluation results, O is good, Δ is slightly good, and × is poor.

〔table〕

As is clear from the table, when the angle a is more than 70'' and less than 110', good results were obtained for each item in combinations where b and b' are acute angles. However, the combination where b' is both +45° (a is 90°) gave the best result.

The combination in which both b and b' are 145'' (a is 90') showed basically the same results as the best combination described above, but the rubbing direction, that is, the alignment direction of liquid crystal molecules and the polarization axis of the polarizing plate, Due to the relationship between , and the incident direction of light (incident from the lower polarizing plate 5 side) in the case of a transmission type, there is a difference in viewing angle dependence, and the combination of +45'' for both b and b' has a better viewing angle direction. As a result, there is an advantage that there is a wide margin for setting the drive voltage.

<Effects of the Invention> As explained above, according to the present invention, there is provided an SBE type liquid crystal display element which has significantly better time-division characteristics than a TN type liquid crystal display element, has less color tone unevenness, and has a lower color tone angle. It is possible to obtain a display element having excellent display quality with less dependence and a wide viewing angle range.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the configuration of an embodiment of the present invention, and FIGS. 2 and 3 respectively show its polarization axis 1a. FIG. 5 is an explanatory diagram of the relationship between 5a and the rubbing direction. 1--Upper polarizing plate 1a-Polarizing axis 2.4--Electrode substrates 2a, 4a-Rubbing direction 3-Nematic liquid crystal 5-Upper polarizing plate 5a-Polarizing axis 6--Highlight patent applicant Sharp Corporation Agent Patent Attorney Nishi 1) Arata]

Claims (1)

[Claims] A liquid crystal cell is formed by sandwiching twisted oriented nematic liquid crystal having a twist angle of 180° between electrode substrates disposed facing each other, and a pair of polarizing plates are disposed on both sides of the liquid crystal cell. In a display element in which at least one of the polarizing plates is a yellow color polarizing plate, the product Δn·d of the refractive index anisotropy Δn of the nematic liquid crystal and the thickness d of the liquid crystal layer is set to 0.93 μm or less. and the crossing angle of the polarization axes of the pair of polarizing plates is more than 70° and less than 110° toward the viewing angle direction of the display element, and the polarization axis of each of the polarizing plates and the alignment of liquid crystal molecules are different from each other. 1. A liquid crystal display element characterized in that the angle formed with the regulating rubbing direction is an acute angle with respect to the twisting direction of liquid crystal molecules.