JPS597367B2 - Field effect liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device that utilizes the field effect of nematic liquid crystal.

In a conventional liquid crystal display device, as shown in FIG.
etc.) to create a sandwich-type structure,
The liquid crystal molecular axis (optical axis) of the liquid crystal layer 1 is aligned perpendicularly to the electrode plates 2 and 3 (homeotropic alignment).
DAP (t) which distorts the initial arrangement by applying an electric field.
DeformatlonofAlignedPhase
ofNematic method, and the liquid crystal molecular axis is aligned parallel to the electrode plate (homogeneous alignment method).
There is a TN (Twis ed Nematic) method in which the electrodes are twisted at 90 degrees between the two electrodes 2 and 3, and vertically aligned by applying an electric field.

However, in the sandwich structure shown in Figure 1, the TN
To use this method, the liquid crystal molecular axes must be aligned parallel to the electrode plates.

For this purpose, it is necessary to perform a treatment such as rubbing on the substrates sandwiching the liquid crystal layer and the electric plates provided on the substrates in advance. Further, in the case of the DAP method, it can be used with the liquid crystal molecular axis aligned perpendicularly to the electrode plate, but there is a drawback that only nematic liquid crystal having negative dielectric anisotropy can be used. This invention provides a nematic liquid crystal that has positive dielectric anisotropy and is homeotropically aligned when no electric field is applied.
In particular, the present invention provides a field effect liquid crystal display device that can be used in the DAP method.

Embodiments of a field effect liquid crystal display device according to the present invention will be described below with reference to the drawings.

In FIG. 2a, 11 is a nematic liquid crystal layer with positive dielectric anisotropy, and when no electric field is applied, liquid crystal molecules I
la is homeotropic orientation (homeotropic
alignment).

This homeotropic orientation can be achieved through treatments such as surfactant treatment. As a liquid crystal, for example, N=C0H
As C=NΦRR, C3H7, C4H9, C5H17
, C6H13, 5C7H15, OCH3, OC.

H5, OC3H7, as R', C2H5, C3H7,
C4H,,C5H,,C6Hl39C7Hl5? C8
Hl7POC4H9pOC5H,l,OC6Hl3,O
C7Hl5,OOCCH3OOcc2H5,OOcc3
H,,n-00cc4H,,n-00cc5H11,n
-00cc6H13RI, C3H7, C4H9,
A single component such as C, Hll, C6Hl3PC7HlaPC8Hl7, or a mixed nematic liquid crystal containing two or more of these (which may also include cholesteric liquid crystal or smectic liquid crystal) is used.

Reference numeral 5 designates transparent parallel electrodes in which two electrodes are formed on a transparent substrate 4 such as glass or plastic stick, facing each other in parallel with an interval of approximately 3 μm to 100 μm.

6 is a DC or AC (10 Hz to 100 KHz) power supply, and 7 is a switch, which is interposed between both electrodes 5a and 5b of the electrode 5.

When the switch 7 is open and no electric field is applied to the liquid crystal layer 11, the liquid crystal molecules 11a exhibit a homeotropic orientation as shown in FIG. Then, the alignment of the liquid crystal molecules 11a becomes an alignment rotated by 90 degrees in a plane perpendicular to the substrate 4, as shown in FIG. 2c. Arrows 11b shown in FIGS. 2B and 2C indicate the dipole moment direction. As shown in Figure 3a, the above device is sandwiched between orthogonal polarizing plates 8 and 9 (the ++ mark indicates the polarization direction horizontal to the plane of the paper, and the - mark indicates the polarization direction perpendicular to the plane of the paper). When opened, the natural light irradiated onto the polarizing plate 8 is polarized by the polarizing plate 8, and the liquid crystal layer 1 is polarized by the polarizing plate 8.
1 and is absorbed by the polarizing plate 9. Therefore, the display side of the polarizing plate 9 becomes dark. Further, as shown in FIG. 3b, when the switch 7 is closed and an electric field is applied to the liquid crystal layer 11,
Since the orientation of liquid crystal molecules changes as shown in Figure 2c,
When the light that has passed through the polarizing plate 8 passes through the liquid crystal layer 11, it becomes elliptically polarized light, and only light of a certain wavelength passes through the polarizing plate 9. Therefore, the display side becomes brighter. For example, the temperature is 25°C, the electrode spacing is 101tm, the liquid crystal layer is 20μm thick, and the liquid crystal used is ~1--11.
~---1' mixed liquid crystal, power supply 6 is 6
Assuming an alternating current voltage of 0 Hz, the characteristics of the transmitted light intensity (arbitrary unit) with respect to the applied voltage (Vrms) are shown in FIG. 3c.

Note that a high reflectance material (A
A reflective plate made of I, Au, MgO, etc.) may be arranged to form a reflective type. As described above, the present invention
When no voltage is applied, homeotropic orientation is induced,
This method does not generate retardation between normal light and abnormal light, causes hybrid orientation when voltage is applied, and generates retardation suitable for color display.

Furthermore, it is also possible to create a "darkness" state by making two polarizers perpendicular to each other. That is, it is possible to provide a field-effect liquid crystal display device with extremely high contrast in both color display and black-and-white display.

[Brief explanation of drawings]

Figure 1 is a diagram schematically showing the structure of a conventional liquid crystal display device.
FIG. 2a is a perspective view schematically showing the structure of the first embodiment of the field effect liquid crystal display device according to the present invention, and FIG.
C is a diagram showing the alignment state of liquid crystal molecules when the switch is open and closed in a plane perpendicular to the electrode plane shown in Figure 2a;
Figures a to c illustrate the display function and characteristics of the device shown in Figure 2a. In the figure, 11... Nematic liquid crystal layer having positive dielectric anisotropy, 5... Parallel electrodes, 6...
・Power, 7... Switch.

Claims (1)

[Claims] 1. A liquid crystal layer made of a nematic liquid crystal having positive dielectric anisotropy and in which liquid crystal molecules are homeotropically aligned when no electric field is applied, and two substrates sandwiching the liquid crystal layer;
A voltage is applied between a plurality of parallel electrodes arranged in parallel to each other that are formed on the inner surface of only one of the two substrates and not formed on the inner surface of the other substrate, and the parallel electrodes that are adjacent to each other. A field effect liquid crystal display device comprising: a voltage applying means for changing the orientation of the liquid crystal molecules; and a polarizing device for visualizing the changed state of the orientation of the liquid crystal molecules.