JPS58173720A - Liquid crystal color display body - Google Patents

Abstract

PURPOSE:To enable negative type color display with high sharpness and contrast in spite of low voltage driving, by applying an orientation treatment of a small tilt angle on one of substrates and applying an orientation treatment of a large tilt angle on the other. CONSTITUTION:An orientation model of a liquid crystal molecule 5 and a dichromatic dye component under no voltage when an orientation film 2 by 85 deg. vapor deposition is applied on an upper substrate 1 and an orientation film 4 by rubbing is applied on a lower substrate 3 is formed by using a liquid crystal compsn. consisting of a nematic liquid crystal having positive dielectric anisotropy, a dichromatic dye and a cholesteric liquid crystal. The orientation control force of the liquid crystal molecule when an orientation treatment of a small tilt angle is applied is weaker than the force at a large tilt angle, and the liquid crystal which is increased in the twist angle by application of the orientation treatment of a small tilt angle by rubbing on both upper and lower substrates decreases contrast by inducing a light scattering state even if no voltage is applied thereto. Therefore, if the orientation treatment of a large tilt angle by 85 deg. vapor deposition is applied on one of the substrates, the orientation controlling force increases and the generation of the light scattering state is difficult even if the twist angle is increased.

Description

Detailed Description of the Invention The present invention provides a liquid crystal composition comprising a nematic liquid crystal with positive dielectric anisotropy and a dichroic dye, or a cholesteric liquid crystal in the liquid crystal composition, between opposing electrodes, at least one of which is transparent. The present invention relates to a guest-host effect type liquid crystal color display in which an added liquid crystal composition is interposed.

A general method for producing a negative type display on a guest-host effect type liquid crystal color display is the White-Taylor method. In this method, a liquid crystal composition consisting of a nematic liquid crystal with positive dielectric anisotropy, a dichroic dye, and a cholesteric liquid crystal is interposed between substrates with electrodes that have been subjected to parallel alignment treatment on both sides or vertical alignment treatment on both sides. This method produces a negative type display by causing a cholesteric-nematic phase transition upon application of an electric current, and is capable of producing a high-contrast liquid crystal display without a polarizing plate compared to conventional systems.

Conventionally, the method for parallel alignment treatment on both sides is SiO oblique evaporation (hereinafter referred to as 85°) with an incident angle of 85° on both sides.
(referred to as evaporation) or by rubbing both sides.
However, in the case of double-sided 85° evaporation, light scattering is difficult to occur (and the threshold voltage is low, but the coloring state is weak when no voltage is applied).In the case of double-sided rubbing, The coloring state is strong when no voltage is applied, but when the twist angle is increased, a light scattering state tends to occur (and the threshold voltage also becomes high).

In order to solve these drawbacks, the present invention has developed a liquid crystal composition consisting of a nematic liquid crystal with positive dielectric anisotropy, a dichroic dye, and a cholesteric liquid crystal, which is heated to a high temperature by 85° vaporization etc. on one side of the substrate. Tilt angle distribution processing is applied, and the incident angle is 60° on the other side.
By injecting it into a liquid crystal cell that has been subjected to low tilt angle alignment treatment such as SiO oblique evaporation and rubbing to make the twist angle of the liquid crystal molecules 90° or more, a clear and high contrast negative color display can be achieved even when driven at low voltage. This is what made it possible.

FIG. 1 shows a liquid crystal composition consisting of a nematic liquid crystal with positive dielectric anisotropy, a dichroic dye, and a cholesteric liquid crystal according to the present invention, and an alignment film 2 formed by 85° vapor deposition on an upper substrate 1. , is an alignment model of liquid crystal molecules 5 and dichroic dye molecules 6 when no voltage is applied when an alignment film 4 is applied to the lower substrate B by rubbing. 7 is a transparent conductive film. The ability to control the alignment of liquid crystal molecules when subjected to a low tilt angle alignment treatment is weaker than that of a high tilt angle one, so the twist angle is increased by applying a low tilt angle alignment treatment to both the upper and lower substrates by rubbing. In this case, C also causes a light scattering state without applying a voltage, resulting in a decrease in contrast in appearance. In the liquid crystal display having the structure according to the present invention shown in FIG. 1, since one of the substrates is subjected to alignment treatment with a high tilt angle by 85° vapor deposition, the alignment control force of the liquid crystal molecules on the substrate is strong, and the twist angle is Even if the value is increased, light scattering is less likely to occur.

In FIG. 2, the horizontal axis represents the applied voltage and the vertical axis represents the transmittance, and the transmittance of the liquid crystal display is plotted against the voltage applied to the display. In Figure 2, one of the substrates shown by curve (a) was subjected to high tilt angle alignment treatment by 85° vapor deposition, while both the upper and lower substrates shown by curve (b) in the same figure were subjected to low tilt angle alignment treatment by rubbing. Compared to those subjected to alignment treatment, the threshold voltage is lower and low voltage driving becomes possible.

Figure 6 plots the tilt angle on the horizontal axis and the transmittance on the vertical axis, and plots the transmittance of the liquid crystal display against the pretilt angle of the liquid crystal molecules, and shows the liquid crystal display when no voltage is applied. It represents the transmittance. The one in which both upper F substrates were evaporated at 85° has a pre-tilt angle as shown in the figure ( ), which makes it difficult to cause light scattering, or because it has a considerable tilt angle when no voltage is applied. As shown in the middle (d), the coloring is weak and the display has low contrast.The display according to the present invention in which one substrate is subjected to alignment treatment with a low tilt angle by rubbing, In the figure (e
), and compared to the case where both the upper and lower substrates are vapor-deposited at 85°, the coloring is stronger when no voltage is applied, and the display ability with high contrast is achieved, as shown in (f) in the figure.

As described above, the present invention eliminates the drawbacks of the conventional White-Taylor type guest-host effect type liquid crystal color display and enables clear negative color display. It can be widely used as a display for calculators, various instruments, etc.

[Brief explanation of the drawing]

FIG. 1 is a molecular orientation model of a guest-host effect type liquid crystal color display based on the present invention, and FIG. 2 is a diagram showing the relationship between applied voltage and transmittance of a guest-host effect type liquid crystal color display. FIG. 6a is a diagram showing the relationship between the pretilt angle of liquid crystal molecules and the transmittance of a guest-host effect type liquid crystal color display. 1.6... Glass substrate, 2... Alignment film by 85° vapor deposition, 4... Alignment film by rubbing, 5... Liquid crystal molecules, 6... Dichroic dye molecules, 7... transparent conductive film, a
...Curve of a liquid crystal display with 85° vapor deposition on one side of the substrate and rubbing on the other, b-...Curve of a liquid crystal display with rubbing on both substrates, C...Curve of a liquid crystal display with rubbing applied to both substrates. 85
Tilt angle of liquid crystal display body with ° vapor deposition, transmittance of liquid crystal display body at tilt angle of d#・aC, e... of liquid crystal display body with 85° vapor deposition on one side of the substrate and rubbing on the other side Tilt angle, transmittance of the liquid crystal display at a tilt angle of f...e. ---,,,,,,,,,,,-/ Toshi 20 01t! 345 Ep force otL (Vl Q / (112030 chitl, 1 angle (degrees)

Claims (1)

[Scope of Claims] (1) In a liquid crystal display using a color liquid crystal composition comprising a nematic liquid crystal having a positive dielectric anisotropy between opposing electrodes, at least one of which is transparent, and a dichroic dye, 1. A liquid crystal color display, characterized in that one of the two is subjected to a high tilt angle (5 to 45°) alignment treatment, and the other is subjected to a low tilt angle (0 to 5°) alignment treatment. (2) A liquid crystal display using a color liquid crystal composition consisting of a nematic liquid crystal with positive dielectric anisotropy between opposing electrodes, at least one of which is transparent, a dichroic dye, and a cholesteric liquid crystal. A liquid crystal color display body characterized in that one of the sides is subjected to a high tilt angle alignment process and the other side is subjected to a low tilt angle alignment process. (31%, W, +Claim 1 or 2 A liquid crystal color display according to claim 1, characterized in that vapor deposition is used for high tilt angle alignment treatment, and rubbing is used for low tilt angle alignment treatment. (4) Scope of Claim 1. Or, the liquid crystal color display according to claim 2, characterized in that vapor deposition is used for alignment treatment for both high tilt angle and low tilt angle. (5) Claim 6 or 7. A liquid crystal color display body characterized in that the liquid crystal color display body according to item 4 is characterized in that the twist angle of the liquid crystal molecules is 90° or more.