JPH0534731A - Color liquid crystal display element - Google Patents

Abstract

PURPOSE:To make the background color of the conventional color liquid crystal display element colorless. CONSTITUTION:A slight amt. of a dichromatic dye of such hue as to become the compensating color of a color polarizing plate 1 is incorporated into a liquid crystal 8 of the liquid crystal display element constituted by combining the conventional TN cell 2 and the color polarizing plate 1, by which the background color slightly colored heretofore to the color of the color polarizing plate 1 is made colorless and the display of red, blue or green on the bright white background is allowed. Multicolor display is possible as well if plural sheets of the liquid crystal cells 2 and the polarizing plates 1 are alternately laminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a color liquid crystal display device,
In particular, the present invention relates to a reflective type mono-color liquid crystal display element for watches, calculators, game machines and the like.

[0002]

2. Description of the Related Art A mono-color liquid crystal display device combining a twisted nematic (TN) mode and a color polarizing plate is known as SID 1973 SYMPOSIUM DIG.
EST p. 40, the liquid crystal display mode is well known in the past, as reported by Shunsuke Kobayashi et al.

As shown in FIG. 1, this color liquid crystal display device includes a color polarizing plate 1, a liquid crystal cell 2, a neutral color polarizing plate 3, an omnidirectional reflector 4, an upper substrate 5 of the liquid crystal cell,
It is composed of a lower substrate 6, a transparent electrode 7, and a nematic liquid crystal 8. As shown in FIG. 2, the relationship between the respective axes is that the polarization axis (absorption axis) direction of the color polarizing plate 1 is 11, the liquid crystal alignment direction of the upper substrate 5 of the liquid crystal cell is 12, and the liquid crystal of the lower substrate 6 of the liquid crystal cell. The alignment direction is 13, the polarization axis direction of the neutral polarizing plate 3 is 14, and the angle formed by 11 and 12 is 21, the nematic liquid crystal 8
If the twist angle of 22 is 14 and the angle formed by 14 is 13, the angles 21 and 23 are both set to about 0 degrees or about 90 degrees, and the angle 22 is set to about 90 degrees.

In the conventional color liquid crystal display device having the above structure, white is displayed when no voltage is applied or a non-selection voltage is applied, and a color corresponding to the color polarizing plate is displayed when a selection voltage is applied. For example, when a red polarizing plate is used, red is displayed on a white background.

[0005]

However, such a conventional color liquid crystal display device has a problem that the background color does not become a true white color but the color of the color polarizing plate is slightly colored. Especially in the case of a reflective display, the coloring of the background color was remarkable. For example, the display color when a red polarizing plate is used is shown in FIG. Reference numeral 41 is a spectral characteristic of the background when no voltage is applied, that is, 42 is a spectral characteristic of the display when a voltage is applied, that is, a display spectral characteristic. The background color 41 is faintly red. Due to this coloring, the color liquid crystal display device using the color polarizing plate does not have a high-class display quality and has not yet been accepted in the market.

The present invention is intended to solve such a problem. An object of the present invention is to mix a dichroic dye having a hue which is a complementary color of a color polarizing plate into a liquid crystal to obtain a bright white color. An object of the present invention is to provide a color liquid crystal display device capable of color display on the background.

[0007]

A liquid crystal display device of the present invention is a color liquid crystal display device comprising a liquid crystal cell in which a nematic liquid crystal is sandwiched between a pair of substrates, and at least one color polarizing plate, The nematic liquid crystal is mixed with a dichroic dye having a hue that is a complementary color of the color polarizing plate.

Further, the amount of the dichroic dye is 1% by weight or less of the amount of liquid crystal.

Further, the liquid crystal cell is characterized in that two or more layers are laminated through a polarizing plate to perform multicolor display.

[0010]

FUNCTION The spectral characteristics of the red color polarizing plate alone are schematically shown at 43 in FIG. This polarizing plate has the same function as a normal polarizing plate for blue and green, but has no polarizing ability for red. If the neutral polarizing plate and the polarization axis are stacked in parallel with each other, a flat spectral characteristic is originally expected, but in reality, a slightly reddish color as shown by 44 is obtained. This is because the color polarizing plate uses a dye having poor dichroism as its polarizing element, and when an attempt is made to obtain a degree of polarization of blue and green, the light amount of these two colors is reduced.

In order to avoid this, a method of decreasing the polarization degree of blue and green to increase the amount of transmitted light and a method of decreasing the amount of red light by using a cyan color filter which is a complementary color of red are considered. Also deteriorates the red display when the selection voltage is applied. In the present invention, by adding a cyan dichroic dye to the liquid crystal, the background color is neutralized, and when the selection voltage is applied, the dye is aligned with the liquid crystal in the substrate normal direction and does not show a cyan color. The feature is that the red display is not damaged.

The purpose of the dichroic dye is to neutralize the faint coloration of the background, and the guest host (G
Since the display is not intended to be performed by the dichroic dye itself as in the H) mode, it is not necessary to add 3 to 5 wt% of the liquid crystal as in the normal GH mode. Normally 0.5 wt
%, Even if the cell gap is as thin as 5 μm, an amount of 1.0% or less is sufficient, and if it is added in excess, the background color is rather deteriorated.

[0013]

Example 1 As shown in FIG. 1, a color liquid crystal display device of the present invention comprises a color polarizing plate 1, a liquid crystal cell 2, a neutral polarizing plate 3, an omnidirectional reflector 4 and an upper substrate of a liquid crystal cell. 5, the lower substrate 6, the transparent electrode 7, and the nematic liquid crystal 8. As a color polarizing plate, a red polarizing plate NPF- manufactured by Nitto Denko Corporation
Q-10R (polarization degree 57.0%), and as a neutral polarizing plate and an omnidirectional reflector, a polarizing plate integrated polarizing plate NPF-G-3228M (polarization degree 9 also manufactured by Nitto Denko Corporation)
5.0%) was used. On the other hand, as the nematic liquid crystal 8,
TN liquid crystal ZLI-2309 (Δn = 0.
1188), cyan dichroic dye LSB-335 manufactured by Mitsubishi Kasei Co., Ltd. 0.50 wt% and chiral dopant S-811 manufactured by Merck Ltd. 0.05 wt% are added to obtain a gap of 10.9 μm. It was injected into the cell and used.

As shown in FIG. 2, the relationship between the respective axes is 11, the polarization axis (absorption axis) direction of the color polarizing plate 1, the liquid crystal alignment direction of the upper substrate 5 of the liquid crystal cell is 12, and the lower substrate of the liquid crystal cell. The liquid crystal alignment direction of 6 is 13, the polarization axis direction of the neutral polarizing plate 3 is 14, and the angle formed by 11 is 12, and the twist angle of the nematic liquid crystal 8 is 22, and the angle formed by 14 is 13 is 2.
If it is set to 3, the angles 21 and 23 are both set to about 0 degree or about 90 degrees, and the angle 22 is set to about 90 degrees.

FIG. 4 shows the display colors of the color liquid crystal display element in the first embodiment of the present invention having the above structure. Here, 41 is a spectral characteristic of the background when no voltage is applied, that is, 42 is a spectral characteristic of a display when a voltage is applied. The coloring of the background color 41 is remarkably reduced as compared with FIG. 6 showing the display color of the conventional color liquid crystal display element. In addition, although the brightness is also reduced by the amount of the pigment in the measurement, it actually feels brighter because there is no coloring in the eyes. On the other hand, with respect to the display color 42, due to the effect of the dichroic dye, if only a sufficient voltage is applied, excellent color purity and brightness which are not different from the conventional ones are exhibited.

(Example 2) The color liquid crystal display device of the present invention comprises a liquid crystal cell and a polarizing plate which are alternately laminated.
Multicolor display can also be performed.

As shown in FIG. 3, the liquid crystal display element in Example 2 includes a color polarizing plate 31, a first liquid crystal cell 32,
A first neutral polarizing plate 33, a second liquid crystal cell 34,
It is composed of a second neutral polarizing plate 35 and an omnidirectional reflector 36. As a color polarizing plate, a blue polarizing plate NPF-Q-10B (polarization degree 55.0%) manufactured by Nitto Denko Corporation, and as a first neutral polarizing plate, NPF-G1225DU (polarization degree 99. 5%) as the second neutral polarizing plate and the omnidirectional reflecting plate, which is also a polarizing plate integrated polarizing plate NPF-F-3 manufactured by Nitto Denko Corporation.
205 (polarization degree 96.5%) was used. To make the degree of polarization of the first polarizing plate higher than that of the second polarizing plate,
This is important for obtaining a bright and high-contrast display. On the other hand, as the nematic liquid crystal used for the first liquid crystal cell 32, TN liquid crystal ZLI-1844 (Δn =
0.181) and 0.75 wt% of yellow dichroic dye LSY-116 manufactured by Mitsubishi Kasei Co., Ltd. and 0.05 wt% of chiral dopant S-811 manufactured by Merck Ltd. are used, and a gap of 7. A 2 μm cell was twist-oriented to the left by 90 degrees. The second liquid crystal cell 34 has a T manufactured by Merck.
BD on the liquid crystal ZLI-1221 for N (Δn = 0.13)
Chiral dopant CB-15 manufactured by Company H is 0.07 wt.
% Added to a cell with a gap of 10.0 μm to the right 90
It was twisted in degrees.

In the color liquid crystal display device having the above-described structure according to the second embodiment of the present invention, the first liquid crystal cell displays blue and the second cell displays black on a white background. I can.

If the polarizing plate 35 is a color polarizing plate and a dichroic dye having a complementary color is added to the second cell, it is possible to display another color in the second cell. Also, by selecting a color polarizing plate and a dichroic dye so as to display cyan color in the first cell and yellow color in the second cell, it is possible to display four colors of green, yellow, cyan and white by subtractive color mixing. Become. In any case, the background color is pure white as in the TN mode using a normal neutral polarizing plate.

[0020]

As described above, according to the present invention, it is possible to display a color on a bright white background by mixing a dichroic dye having a hue which is a complementary color of the color polarizing plate into the liquid crystal. A color liquid crystal display device can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display element according to a first embodiment of the present invention and a conventional technique.

FIG. 2 is a relationship diagram of each axis of the liquid crystal display element according to the first embodiment of the present invention and the related art.

FIG. 3 is a cross-sectional view of a liquid crystal display element in Example 2 of the present invention.

FIG. 4 is a diagram showing display colors of the liquid crystal display element in Example 1 of the present invention.

FIG. 5 is a diagram showing display colors of a conventional liquid crystal display element.

FIG. 6 is a diagram showing spectral characteristics of a red polarizing plate.

[Explanation of symbols]

1 Color Polarizer 2 Liquid Crystal Cell 3 Neutral Polarizer 4 Omnidirectional Reflector 5 Upper Substrate 6 of Liquid Crystal Cell 2 Lower Substrate 7 of Liquid Crystal Cell 2 Transparent Electrode 8 Nematic Liquid Crystal 11 Polarization Axis Direction of Color Polarizer 1 12 Above Liquid Crystal Cell Liquid crystal alignment direction 13 of the substrate 5 Liquid crystal alignment direction of the lower substrate 6 of the liquid crystal cell 14 Polarization axis direction 21 of the neutral polarizing plate 3 11 angle 12 forms 22 Twist angle 23 14 of nematic liquid crystal 8 angle 13 forms 31 Color polarization Plate 32 First Liquid Crystal Cell 33 First Neutral Polarizing Plate 34 Second Liquid Crystal Cell 35 Second Neutral Polarizing Plate 36 Non-Directing Reflecting Plate 41 Spectral Characteristics When No Voltage Applied (Background) 42 When Selected Voltage Applied (Display 4) Spectral characteristics of a single red polarizing plate 44 Spectral characteristics when a red polarizing plate and a neutral polarizing plate are stacked in parallel

Claims (3)

[Claims] 1. A color liquid crystal display device comprising a liquid crystal cell in which a nematic liquid crystal is sandwiched between a pair of substrates, and at least one color polarizing plate, wherein a color complementary to the color polarizing plate is contained in the nematic liquid crystal. A liquid crystal display device characterized in that a dichroic dye having such a hue is mixed. 2. The color liquid crystal display element according to claim 1, wherein the amount of the dichroic dye is 1% by weight or less of the amount of the liquid crystal. 3. The color liquid crystal display element according to claim 1, wherein the liquid crystal cell is laminated in two or more layers with a polarizing plate interposed therebetween to perform multicolor display.