JPH02105111A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To decrease dependency on visual angles and to improve display quality by providing a double refractive layer to at least either of between a liquid crystal layer and both polarizers and forming the double refractive layer in such a manner that the refractive indices in any directions within the plane thereof are nearly equal and satisfy the specific relations. CONSTITUTION:The liquid crystal layer 30 is held crimped between both upper and lower substrates 12, 23 formed with transparent electrodes 12, 22 and ori ented films 11, 21 and is isolated from the outside world by a sealing material 31, by which the liquid crystal cell is formed. The double refractive layer 32 is provided to at least either of between the liquid crystal cell and the two polarizers 14, 24. The liquid crystal display element is so constituted that the refractive indices in any directions within the plane of this double refractive layer 32 are nearly equal and satisfy the relations 0.11mum<(nz-nxy)l<0.55mum (where nxy, nz and l are respectively the refractive index of the intra-surface direction of the double refractive layer, the refractive index in the thickness direction and the thickness). The dependency on the visual angles is drastically decreased by the simple method in this way and the liquid crystal display ele ment having the excellent display quality is obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a liquid crystal display element, and in particular to an ECB (elect
rically controlled birefr
The present invention relates to an ingenca type liquid crystal display element.

[Conventional technology]

So-called EC using electrically controlled birefringence effect
B-type liquid crystal display elements are already known, and in this type of liquid crystal display element, the magnitude of birefringence of the liquid crystal layer is changed by applying a voltage to perform optical modulation. The publication discloses a DAP type ECB type liquid crystal display element that performs light modulation by applying a voltage to a vertically aligned liquid crystal layer and changing the magnitude of birefringence of the liquid crystal layer.

[Problem to be solved by the invention]

However, in conventional HCB type liquid crystal display elements, the distance within the liquid crystal layer through which the observed light actually passes changes depending on the viewing angle, and the magnitude of the apparent birefringence varies between the alignment direction of liquid crystal molecules and the viewing angle direction. There is a problem in that the visual angle dependence of the display is extremely large due to changes depending on the angle, and the angle range that can be confirmed is extremely small.

An object of the present invention is to eliminate such drawbacks of the prior art and to provide an ECB type liquid crystal display element with significantly reduced visual dependence and excellent display quality.

[Means and effects for solving the problem] In order to achieve the above object, according to the present invention, a liquid crystal layer having positive dielectric anisotropy is sandwiched between a pair of substrates having electrodes so as to be homogeneously aligned. In a liquid crystal display element comprising a liquid crystal cell and a pair of polarizers arranged to sandwich the liquid crystal layer, a birefringent layer is provided at least on one side between the liquid crystal cell and both polarizers. provided, the birefringent layer has substantially the same refractive index in any in-plane direction, and 0.11. um<(nz-nzy)Q<0.5511m
(However, nZ9.nZ and Ω are the refractive index in the in-plane direction, the refractive index in the thickness direction, and the thickness of the birefringent layer, respectively.) Provided is a liquid crystal display element that satisfies the following relational expression: be done.

In the present invention, the viewing angle dependence of the ECB type liquid crystal display element is reduced to 1.
The in-plane refractive index (ny) is isodirectional, but the thickness (Q)
This is achieved by using a birefringent layer whose refractive index (nz) in the direction is greater than nZ.

In this case, the relationship between nχJ'+nZ and p is 0.11μm<(nz-nzy)Q<0.55μ+s as described above.
The relationship is more preferably 0.22. um<(nz-n
zy) Q<0.44 μm.

If the value of (nz-nz,y)ff is larger than 0.55 μm, the viewing angle dependence will be the same as or higher than that without a birefringent layer, and if it is smaller than 0.11 μm, there will be no birefringence. It has the same degree of viewing angle dependence as .

Such a birefringent layer is realized, for example, by a polymer layer placed between the liquid crystal layer and at least one of the polarizers. Alternatively, at least one of the two substrates may have birefringence so that the birefringent substrate satisfies the above relational expression. In this way, viewing angle dependence can be reduced without increasing the number of steps and without increasing the cell thickness.

Further, at least one of the pair of polarizers has 711
It may be made to have Fft1 folding property. Specifically, for example, a polarizer is constructed of two polarizer substrates, a dichroic polarizing film is sandwiched between them, and the polarizer substrate on the liquid crystal layer side is made to have birefringence. Make it. Even in this case, the viewing angle dependence can be reduced without increasing the number of steps as described above and without increasing the cell thickness.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the liquid crystal display element of the present invention. A liquid crystal layer 30 is sandwiched between upper and lower substrates 13.23 on which transparent electrodes 12.22 and alignment films 11 and 21 are formed, and is isolated from the outside world by a sealing material 31 to form a liquid crystal cell. The liquid crystal molecules of the liquid crystal layer 30 are aligned substantially horizontally to the substrates 13.23 due to the orientation fill, 21, and are homogeneously aligned between the substrates 13.23. Note that, if necessary, a spacer may be mixed into the liquid crystal layer 30 or the sealing material 31 in order to keep the thickness of the liquid crystal layer 30 constant.

A polarizer 1 is placed on the outermost side of the liquid crystal cell formed as described above.
4.24, but in this example, the upper polarizer 2
A birefringent Rj32 that satisfies the above-mentioned conditions was placed between the upper substrate 4 and the upper substrate 23.

Here, in order to explain the effects of the birefringent layer 32, angles will be defined as shown in FIG. That is, the angle between the direction perpendicular to the liquid crystal cell plane CP and the incident light IL is θ, the orientation direction of the liquid crystal molecules in the liquid crystal layer 30 is h, and the angle between the direction of the projection of the incident light direction onto the substrate plane is φ. shall be.

The color when the liquid crystal cell is viewed from the front (θ = 0°) and when viewed from an oblique direction (θ = 40°, φ = 0° and θ = 40°
.

The color of The relationship is shown in Figure 3.

(nz-nzy)jl=0 corresponds to the absence of the birefringent layer 32. From the same figure, (nz-nZ,)Q=0.
It can be seen that the viewing angle dependence of color is small when the value is 66μ or less.

Various organic polymers can be used as the material constituting the birefringent layer 32.

FIG. 4 is a sectional view showing another embodiment of the liquid crystal display element according to the present invention. In the figure, elements similar to those in FIG. 1 are designated by the same reference numerals. As shown in FIG. 4, this embodiment has a structure similar to that of a conventional liquid crystal display element in appearance, but the polarizer 14
．． The structure of 24 is different from the conventional one. That is, as shown in FIG. 5, the polarizers 14 and 24 have a structure in which a dichroic polarizing film 40 is sandwiched between two polarizer substrates 41 and 42.

By using a polymer layer having the same birefringence as described above for the substrate on the liquid crystal layer 30 side among these two polarizer substrates 41 and 42, the same effects as described above can be obtained.

In addition, in the configuration shown in FIG. 4, the polarizer 14.24 is the same as the element shown in FIG. The same effect as described above can also be obtained by using a polymer layer having a birefringence of .

〔Effect of the invention〕

As described in detail above, according to the present invention, a birefringent layer that satisfies the above relationship is provided on at least one of the liquid crystal layer and both polarizers, so that viewing angle dependence can be easily reduced. By this method, it is possible to provide a liquid crystal display element with excellent display quality.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the liquid crystal display element of the present invention;
Figure 2 is a diagram showing the definition of angles to explain the effects of the birefringent layer in the liquid crystal display element of the present invention, and Figure 3 is a diagram showing the colors when the liquid crystal display element is viewed from the front and when viewed from an oblique direction. FIG. 4 is a cross-sectional view showing another embodiment of the liquid crystal display element of the present invention, and FIG. FIG. 3 is a cross-sectional view showing the structure of a polarizer. 11.21...Alignment film 12,22...Transparent electrode 13.23...Substrate 14, 24...Polarizer 30...Liquid crystal feI31...Seal material 32...
・Birefringent layer patent applicant Riko Co., Ltd. - Representative patent attorney Toshiaki Ikeura (one person) Figure 2 Figure 4 40 = Nishiki Shikikoran 41. 42-4 Flea reversal for flattened roundlets

Claims (1)

[Claims] (1) Equipped with a liquid crystal cell in which a liquid crystal layer having positive dielectric anisotropy is sandwiched between a pair of substrates having electrodes so as to be homogeneously aligned, and a pair of polarizers arranged to sandwich the liquid crystal layer. In a liquid crystal display element configured as a liquid crystal display element, a birefringent layer is provided at least on one side between the liquid crystal layer and both polarizers, and the birefringent layer has substantially the same refractive index in any in-plane direction. , and 0.11 μm<(nz−nχy)l<0.
55 μm (where nχy, nz, and l are the refractive index in the in-plane direction, the refractive index in the thickness direction, and the thickness, respectively, of the birefringent layer).