JPH024886B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a guest-host type (abbreviated as GH type) liquid crystal display element that utilizes the electro-optical effect of liquid crystal in which a dichroic dye is dissolved.

The structure and principle of the GH type liquid crystal display element are as follows. Two horizontally aligned electrode substrates are stacked so that their alignment directions are parallel, and between them, two
A liquid crystal display is created by enclosing a nematic liquid crystal with a positive dielectric anisotropy containing a colored dye to a thickness of approximately 10 μm, and further arranging a linear polarizing plate so that its polarization axis is parallel to the orientation direction. The element is configured. The dichroic dye dissolved in the liquid crystal is aligned almost parallel to the liquid crystal molecules, and as the orientation of the liquid crystal molecules changes by applying a voltage, the orientation of the dye molecules also changes at the same time. Therefore, when there is no electric field, the polarization axis and the dye molecules are parallel, and the color of the dye is displayed.As the orientation of the liquid crystal molecules changes with voltage application, the angle between the polarization axis and the dye molecules changes depending on the electric field strength. The angle changes from 0° to 90°, and the display color changes from colored to colorless, so it is possible to display colorless or colored by turning the voltage on or off.

By the way, in practical terms, in order to bond and fix two substrates at regular intervals, two substrates that are horizontally aligned are used.
Adhesive is applied by screen printing around the surface of at least one of the two substrates, forming an airtight chamber to prevent liquid crystal material from leaking out or deteriorating the life of the liquid crystal display element due to the influence of outside air. is configured. When a linear polarizing plate is disposed on the liquid crystal display element obtained in this way, minute coloring unevenness (light colored spots) exists over the entire surface of the element, and the intensity of the coloring decreases when no voltage is applied. It was found that the contrast decreased. The cause of this is that the weave of the threads of the screen when printing the adhesive comes into contact with the oriented substrate surface and scratches the oriented layer, causing the liquid crystal alignment to be disrupted (defects) in this area, causing the dye to emit light. It turned out that this was due to decreased absorption. However, since there is currently no simple and reliable method for adhering and fixing substrates other than screen printing, there has been a desire for a means to eliminate the decrease in contrast caused by this disordered arrangement (defective arrangement).

The present invention addresses the drawbacks of the conventional GT type liquid crystal display elements described above. It is an object of the present invention to provide a highly practical liquid crystal display element that eliminates a decrease in contrast.

That is, the present invention provides a guest-host type liquid crystal display element in which a liquid crystal in which a dichroic dye is dissolved is held between two electrode substrates, in which the inner surface of at least one of the two electrode substrates is in contact with the liquid crystal. teeth,
An alignment treatment is applied to horizontally align liquid crystal molecules, and a linear polarizing plate is placed on the outer surface of the substrate with fewer defects in the alignment of liquid crystal molecules on the surface of the two substrates, so that its polarization axis is almost parallel to the alignment direction. The liquid crystal display element is characterized in that it is arranged so that the orientation direction of the other substrate is
This is a highly practical liquid crystal display device that displays uniform colors regardless of non-uniformity or disturbances in the alignment process and does not reduce contrast.

More specifically, one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the surface of a substrate 1, 1' having two transparent electrodes 2, 2' is rubbed in one direction with absorbent cotton to horizontally align it to form alignment layers 3, 3'. Then, epoxy adhesive 4 is applied by screen printing around the surface of the alignment layer 3' of the substrate 1', so that the alignment layers 3, 3' face each other, and the substrates 1, 1' are bonded together. The substrates are stacked so as to maintain an interval of about 10 μm, and the adhesive 4 is cured to fix the substrates to form a liquid crystal container. In this container, blue dichroic dye D
A nematic liquid crystal E-8 (manufactured by BDH, UK) with positive dielectric anisotropy in which 1 wt.% of 1 wt. The liquid crystal display element according to the present invention is formed by disposing it on the outer surface of the substrate 1, which has few defects. This liquid crystal display element exhibits a uniformly deep blue color when no voltage is applied, and changes to colorless when a 3V voltage is applied.
There were no light spots due to the texture of the screen, and good contrast was observed. Add this to the second
The principle will be explained using figures. Figure 2 a shows the board 1
FIG. 2B is a diagram schematically showing the molecular arrangement of the orientation treatment layer 3 of the substrate 1' in parallel lines, and is a diagram schematically showing the molecular arrangement of the orientation treatment layer 3' of the substrate 1' in FIG. Due to printing, alignment defects 7 are present in the areas where the screen textures have contacted each other. Therefore, although the arrangement of molecules in contact with substrate 1 and substrate 1' is different,
Due to the properties of liquid crystal, the alignment changes continuously in the thickness direction of the liquid crystal layer. For example, if both are parallel, the orientation of the molecules does not change in the thickness direction, and if both are perpendicular to each other, the orientation of the molecules is continuously twisted by 90° in the thickness direction. Therefore, if a linear polarizing plate 6 is disposed on the outer surface of the substrate 1 having a uniform alignment layer 3, no matter what direction the molecules on the substrate 1' side face, the orientation of the molecules on the substrate 1 side will be in a straight line. Since it is uniformly parallel to the polarization axis of the polarizing plate 6, no color unevenness occurs. On the other hand, it was found that when the linear polarizing plate 6 was disposed on the outer surface of the substrate 1', color unevenness occurred due to non-uniform orientation of the molecules.

As described in the embodiments above, the liquid crystal display element according to the present invention can be manufactured in exactly the same process as conventional elements, and is a practical element since it eliminates color unevenness and deterioration of contrast.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a cross section of a liquid crystal display element according to the present invention, and FIGS. 2a and 2b are diagrams showing molecular alignment in an alignment treatment layer of a substrate. 1, 1'...Substrate, 2, 2'...Transparent electrode, 3,
3'...Alignment treatment layer, 4...Adhesive, 5...Nematic liquid crystal, 6...Linear polarizing plate.

Claims (1)

[Claims] 1. In a guest-host type liquid crystal display element in which a liquid crystal in which a dichroic dye is dissolved is held between two electrode substrates, the inner surface of one of the two electrode substrates in contact with the liquid crystal has a horizontally aligned In addition to being treated, an adhesive is screen printed around it, and the inner surface of the other of the two electrode substrates in contact with the liquid crystal is subjected to horizontal alignment treatment,
The two electrode substrates are combined using the adhesive, and a linear polarizing plate is disposed on the outer surface of the other substrate so that its polarization axis is substantially parallel to the alignment direction. element.