JPH01209424A - Liquid crystal electrooptic device - Google Patents

Abstract

PURPOSE:To improve the performance of field angle, response, and display by eliminating twist structure and specifying a value DELTAn.d, orienting molecules contacting upper and lower substrates so that pretilt angles are not in parallel, and making the axes of polarization of polarizing plates cross each other at right angles and setting the angle between the axes of polarization and liquid crystal molecule major axes to almost 45 deg.. CONSTITUTION:Liquid crystal molecules 105 have no twist structure and are oriented so that the angles (pretilt angle) between the substrates and liquid crystal molecule major axes are such angles that molecules nearby the two substrates 102 are not parallel. The product (DELTAn.d) of the thickness of the liquid crystal layer and the effective refractive index anisotropy to light incident on the substrate 102 vertically is set to 0.2-0.35mum. Further, the liquid crystal layer is formed between the two polarizing plates 101 which are arranged so as to have their axes of polarization at right angles to each other, and the angle between the polarization axis and the liquid crystal molecule major axis projected on the substrate 102 is set to about 45 deg.. Consequently, performance exceeding a TN system in terms of the field angle, response, and display is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal electro-optical device used in devices such as displays, light valves, and optical modulators, which are the applied fields of liquid crystal electro-optical devices.

[Conventional technology]

Conventional liquid crystal electro-optical devices mainly use the so-called TN system in which the liquid crystal layer has a twisted structure.

[Problem to be solved by the invention]

However, in such conventional liquid crystal electro-optical devices, the value of the product ΔnXd of the layer thickness d of the liquid crystal layer and the optical anisotropy Δn is set to a high value due to the dispersion characteristics resulting from the twisted structure. The viewing angle characteristics tend to be poor. Furthermore, when the pretilt angles are set in parallel, the viewing angle tends to become narrower.

Furthermore, if Δn-d is larger than 0.35 μm, the color characteristics change greatly depending on the viewing angle, thereby degrading the viewing angle characteristics.

In addition, when using an optical compensator, if it has a twisted structure, the allowable lower limit value of △nXd increases as the twist angle increases, so if the same liquid crystal material (material with the same △n) is used, the response is delayed.

Furthermore, for those with a twisted structure, a uniaxial optical compensator cannot completely compensate, and in order to obtain sufficient characteristics, it is necessary to stack multiple optical compensators or use a liquid crystal panel, which is costly. was rising.

An object of the present invention is to eliminate such conventional drawbacks and provide a liquid crystal electro-optical device with excellent viewing angle and response characteristics.

[Means to solve the problem]

The liquid crystal electro-optical device of the present invention eliminates the twisted structure and
n-ci is set between 0.2 μm and 0.35 μm,
In addition, the molecules in contact with the upper and lower substrates were oriented so that their bretil I angles were antiparallel, and the polarization axes of the polarizing plates were orthogonal, and the angle between this polarization axis and the long axis of the liquid crystal molecules was set to around 45". It is characterized by

This allows for a wider viewing angle and faster response. Furthermore, by installing a uniaxial optical compensator with the same ΔnXd as the operating panel to eliminate black light leakage and obtain high contrast when off, and by using a uniaxially stretched polymer film as the optical compensator, the cost is reduced. Moreover, the purpose is to provide this in an arbitrary shape.

〔Example〕

The configuration of the liquid crystal electro-optical device used in the present invention is shown in FIG. 1, where 101 is a polarizing plate, 102 is a glass substrate, and 10
3 is a transparent electrode, 104 is a sealing part for sealing in the liquid crystal and setting the cell thickness to a predetermined value, and 105 is a schematic representation of the arrangement of liquid crystal molecules. The long axes are oriented antiparallel. The alignment treatment was performed by covering the electrode 103 thinly with polyimide resin and rubbing it in one direction with a cloth. The pretilt angle was approximately 3°. By making the rubbing direction the same for the upper and lower substrates, an orientation in which the pretilt directions were antiparallel was obtained. 106 is a uniaxial optical compensation plate,
A stretched polymer film was used. FIG. 2 shows a liquid crystal panel 201 in which the optical compensator shown in FIG. 1 functions.

FIG. 3 shows the optical arrangement of the component parts used in the present invention, in which 301 and 302 are the polarization axes of the upper and lower polarizing plates, which are orthogonal or almost orthogonal to each other, and 303 is the polarization axis of the upper and lower polarizing plates. It represents the state in which the long axis direction of liquid crystal molecules is projected onto the substrate surface, and is approximately 4 degrees with respect to the polarization axes of 301 and 302.
It has a 5° configuration.

Furthermore, the direction of the optical axis when using an optical compensator is shown in FIG. 4, where 401 indicates the optical axis direction, and 303
It is arranged at a position perpendicular or almost perpendicular to the projection direction of the long axis of the molecule.

(Example-1) An example of the arrangement shown in FIG. 3 without using an optical compensation plate is shown.
A liquid crystal material with Δn of 0°095 and dielectric anisotropy of +5.3 at a wavelength of 550 nm was sealed in a liquid crystal panel with a cell thickness of 2.9 μm, and while installed in the optical arrangement shown in Fig. 3,
0Hz square wave 0■. -2 to 6 ■. The state of the optical change when changed to , is shown by the curve 501 in FIG.
In this case, it becomes a positive mode in which the color becomes black when an electric field is applied. At this time, the contrast ratio at a viewing angle tilted 60 degrees from the vertical direction of the panel is shown in Fig. 6 in all directions and compared with the conventional TN type. Here, 701 is the cell used in this experiment and 702 is the conventional TN type. 0, which is the positive mode of the type.
In the figure, the scale represents the contrast ratio, and the driving voltage is 15V each. -2.

The response speed of the present invention is 4 ms for both rise and fall when driven at room temperature with 6Vo-p, whereas the response speed of the present invention is about 5 times faster at 20 m5 each under the same conditions for the TN type.

(Example 2) Showing an example of the arrangement shown in FIG. 4 using an optical compensator, 4
For the optical compensator No. 01, a uniaxially stretched polymer film was used, and Δn×d at 550 nm was 0.28. The liquid crystal panel used in Example 1 was installed in the arrangement shown in Figure 4, and a 100 Hz rectangular wave was applied between the opposing electrodes. -3 to 6Vo- was applied. The transmittance change at that time is shown in the curve 502 of FIG. 5, in this case,
When an electric field is applied, it becomes a negative mode that appears white. The characteristics of the negative mode in the case of the TN type are shown in 504, and light leakage at the black level is observed when no electric field is applied. The cause of this is due to the wavelength dependence of the transmittance of the liquid crystal panel as shown in FIG. .70
4 shows the wavelength characteristics of the on-state, that is, white level, in the present invention and the TN type, respectively. As seen here T
In the N-type negative mode, light leakage occurs in the black level depending on the wavelength, whereas in the liquid crystal electro-optical device of the present invention, light is uniformly blocked over all wavelengths, resulting in a blacker black.

(Example 3) When two sets of liquid crystal panels used in Example 1 were used and arranged in the configuration shown in Figure 2, and only one panel was energized, exactly the same effect as Example 2 was obtained. .

(Example 4) FIG. 8 shows the display when the polymer-axially stretched film was partially installed in Example 2.

801 is a display without an optical compensation plate, and 802 is a display with an optical compensation plate, so that the display can be easily reversed from negative to positive.

〔Effect of the invention〕

As described above, by using the present invention, performance superior to the conventional TN system can be obtained in terms of viewing angle, response, and display performance.

[Brief explanation of the drawing]

1.2 is a diagram showing the configuration of a liquid crystal electro-optical device according to the present invention, FIG. 3.4 is a diagram showing the arrangement of optical elements of the liquid crystal electro-optical device according to the present invention, and FIG. FIG. 2 is a diagram showing voltage/transmittance characteristics of the present invention and a conventional TN system. FIG. 6 is a diagram showing the viewing angle characteristics of the device according to the present invention in comparison with a conventional TN system. FIG. 7 shows the wavelength characteristics of the transmittance of the liquid crystal electro-optical device according to the present invention.
The figure which shows comparison with the conventional TN system. FIG. 8 is a diagram showing the inversion of the display when an optical compensation plate is partially installed. Applicant Seiko Epson Co., Ltd. 20 = Engineering = = = Govlot +01 Figure 1 Figure 2 Figure 5 j] o. Figure 6 Bank & [η- Figure 7

Claims (3)

[Claims] (1) In a liquid crystal electro-optical device in which electrodes are provided on two opposing substrates and a liquid crystal material is sandwiched between the electrodes,
The arrangement of liquid crystal molecules in such a liquid crystal layer does not have a twisted structure, and the angle between the substrate and the long axis of the liquid crystal molecules (pretilt angle) has an alignment structure in which the molecules near each of the two substrates are not parallel to each other. In addition, the product of the thickness of the liquid crystal layer and the effective refractive index anisotropy for light incident perpendicular to the substrate is set to be between 0.2 μm and 0.35 μm, and the polarization axis is orthogonal. It is characterized by having a liquid crystal layer between two polarizing plates arranged to Liquid crystal electro-optical device. (2) The liquid crystal electro-optical device according to item 1, wherein the liquid crystal material used has positive dielectric anisotropy and a pretilt angle of 45° or less. (3) A uniaxial optical compensator that is perpendicular to the long axis direction of the molecules and has a value equal to or almost equal to the product of the liquid crystal layer thickness and effective optical anisotropy is attached to the liquid crystal layer and one of the polarizing plates. Between,
2. The liquid crystal electro-optical device according to claim 1, wherein the liquid crystal electro-optical device is installed over the entire screen or a portion of the screen, and is capable of switching the display mode from a black positive type when an electric field is applied to a white negative type when an electric field is applied.