JPS6059597B2 - Color liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color liquid crystal display device in which a plurality of liquid crystal cells containing dichroic dyes are interposed between a pair of polarizers to enable multicolor display.

Conventionally, color display devices have been known that combine one or more guest-host type single liquid crystal cells and one polarizer, but in this device, each liquid crystal in the single cell has a light color. , the base color, which is a mixture of those colors, becomes lighter,
The drawback was that the contrast between the pattern and the substrate was poor.

In order to improve the above-mentioned drawbacks, this invention inserts a plurality of twisted nematic liquid crystal cells containing dichroic dyes and having different hues between a pair of polarizers to change the background color by blocking light. It is an object of the present invention to provide a color liquid crystal display device that enables multicolor display with high contrast by providing a dark black color.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a color liquid crystal display device according to the present invention, in which Cl and Co are nematic phase guest-host liquid crystal substances L, L, L having positive dielectric anisotropy.
.

This liquid crystal cell is a translucent liquid crystal cell filled with Cl, C
2 includes spacers 5, 52 and these spacers 5, 5
A pair of glass plates G, ,G,',G holding 2 each. ,G
. ', and transparent electrodes E,,E,',E2,E arranged inside these glass plates. ', and the liquid crystal L mentioned above. In addition, one transparent electrode in each cell, for example E, E2, may be divided into multiple parts for pattern display, but to simplify the explanation, the transparent electrodes in each cell may be divided into a plurality of parts having the same shape and the same size as shown in FIG. It is formed into a rectangle.

Transparent electrode E,,E,',E. , E2' are respectively disposed on the glass plates G, and G, 'G2 and G. ', and the adjacent glass plates G and G. ' are aligned so that they are parallel, and the liquid crystals L, L2 have a nematic structure twisted at an angle of 90, for example, and the liquid crystal cells Cl
, C2. A pair of polarizers Hl and H2 are arranged on both sides of the liquid crystal cells Cl and C2, sandwiching these cells. It has a deflection direction perpendicular to . In addition, liquid crystals contain dichroic dyes; for example, liquid crystal L is red in the absence of an electric field and colorless in the presence of an electric field, and liquid crystal L2 is blue in the absence of an electric field and colorless in the presence of an electric field. be. In addition, SW is a switch, V is a DC power supply, and this DC power supply is connected to the transparent electrode E via a drive circuit Z.
Each element is connected so that the voltage is applied between E1 and E1'' and between E2 and E2''.

Next, the operation of the above configuration will be explained.

When light X is irradiated from the polarizer H1 side in the direction of arrow b, this light X is polarized by the polarizer H1, and its polarized light Y becomes
It has a polarization axis in the direction (see Figure 2). By the way, polarized light Y passes through the liquid crystal 1-1, I-, which has a twisted nematic structure.
When the liquid crystals Ll and L2 are sandwiched together, when there is no electric field between the electrodes (OFF), the polarization axis is 900
On the other hand, when an electric field is applied between the electrodes (ON), the twist of the liquid crystal is removed and the polarization axis no longer rotates.

Now, when cells Cl and C2 are both 0FF, as shown in FIG. 2A, the polarization axis of polarized light Y rotates by 90 cells each time it passes through each cell Cl and C2, and the polarization direction A of the polarizer mountain changes.
2, it cannot pass through this polarizer H2, and the display pattern cannot pass through the polarizer H2. No turns appear, and the substrate is dark black from light.

In this state, when cell C2 is turned ON, electrode E2
The liquid crystal facing the cell becomes colorless as soon as its twist is released, and the red color that has passed through cell C1! The polarized light Y passes directly through the cell C2 as shown in FIG. 2B, and passes through the polarizer H2 with its polarization axis parallel to the polarization direction A2 of the polarizer L.

Therefore, on the pattern display surface M, a pattern P1 of one vertical character is displayed on the dark base n, exhibiting the same red color as the liquid crystal L1 of the cell C1. In Figure 2C, C1
indicates a state where 0N1 Seno L/C2 is 0FF, and in this case as well, due to the same function as in the case of FIG. 2B, the liquid crystal L2 of cell C2 and the liquid crystal L2 of cell C2 are A pattern P2 of one vertical character in the same blue color is displayed.

Similarly, if both cells Q and C2 are turned 0N, the second
As shown in Figure D, no pattern is displayed on the display surface M. In other words, if two guest-host cells containing dichroic dye are sandwiched between polarizing plates whose polarization axes are perpendicular to each other, each cell can be colored on a dark background, but the mixed color Also, it is not possible to display patterns in transparent colors. In addition, when two guest host cells each containing blue and red dichroic dyes are sandwiched between two polarizing plates with parallel polarization axes, the background color other than the pattern electrode part is a mixture of blue and red. The color is purple, and on the purple background, there is a purple pattern (both blue and red are 0FF), a dark pattern (one of the blue and red is 0N), and a transparent pattern (
Both blue and red are displayed, but single colors cannot be displayed.

In any case, it is not possible to freely change the color of the pattern, whether it is a single color, mixed color, or transparent color of the cell.

In Figure 3, a colorless twisted nematic liquid crystal cell C3 is added between polarizing plates whose polarization axes are orthogonal, and Cl and C2 are 0N.
．． ．． C3 shows the state of 0FF, and at this time the polarized light Y
can pass through the polarizer H2, and a transparent pattern appears on a purple background.

Table 1 shows the drive of each cell and the color of the pattern in this case.As can be seen from Table 1, if the polarization axes are orthogonal, the ground color is a mixture of cells containing dichroic dyes. Since it is colored, the contrast with the pattern is poor.

To prevent this problem, change the polarization axis A2 of the polarizer to the polarizer H.
The polarization axis a1 may be parallel to the polarization axis a1 of No.1. This makes it possible to darken the background color and improve the contrast of the pattern. Table 2 shows the driving of each cell and the color of the pattern in this case.

That is, the transparent cell C3 only needs to be turned ON when the red cell C1 and the blue cell C2 are simultaneously ON or 0FF, and the pattern is such that the colors other than the cells turned ON are monochrome or mixed colors. Further, although the case where the liquid crystal cell has two colors has been described, a multicolored liquid crystal cell may be used.

Table 3 shows an example in which three primary colors are used in a liquid crystal cell disposed between two polarizers whose polarization axes are orthogonal to each other. In this case, the background color is dark black, so the contrast is extremely good.

In order to display color on a dark black background, multiple twisted nematic liquid crystal cells containing dichroic dyes and one twisted nematic liquid crystal cell (transparent) containing no dichroic dyes are required. If the total value of cells) is an odd number, the polarization axes of the pair of polarizers may be made parallel, and if the total value is an even number, the polarization axes may be made orthogonal. In the description of the present invention, a case has been described in which the alignment treatments formed on adjacent glass plates of the liquid crystal cell are parallel to each other, but of course the alignment treatments may be performed in orthogonal directions.

However, by aligning them in parallel, the light that enters the adjacent liquid crystal cell can be transmitted as it is without being rotated, so there is no loss of light, and the contrast of the liquid crystal cell can be further improved. As described in detail above, in this invention, when the number of liquid crystal cells sandwiched between a pair of polarizers is even, the polarization axes of the polarizers are orthogonal to each other, and when the number is odd, they are aligned parallel to each other. Therefore, the pattern can be displayed by making the base color of the pattern display area of the liquid crystal cell dark black, which increases the contrast between the base color and the color of the display pattern, and improves the visibility of the display pattern. A color liquid crystal display device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a liquid crystal display device according to the present invention, and FIGS. 2A to 2D are exploded perspective views for explaining the operation of the device.
FIG. 3 is an exploded perspective view showing another example for explaining the operation.

Claims (1)

[Scope of Claims] 1. A plurality of twisted nematic liquid crystal cells formed between two transparent substrates containing a dichroic dye, and pattern display portions on opposing surfaces of the two transparent substrates facing each other. a pair of transparent electrodes having the same shape and arranged to apply a voltage to a pattern display section that is a part of the liquid crystal cell; and a pair of polarizers arranged to sandwich the plurality of liquid crystal cells. and the deflection axes of the pair of polarizers are oriented perpendicularly to each other when the number of the liquid crystal cells is an even number, and parallel to each other when the number of the liquid crystal cells is an odd number, and the pattern display portion of the liquid crystal cell is A color liquid crystal display device characterized in that it is configured to display color on a dark background. 2. The color liquid crystal display device according to claim 1, wherein the polarization axes of the adjacent transparent substrates that constitute mutually adjacent liquid crystal cells are aligned in the same direction.