JPH07103314B2 - Liquid crystal display element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a specific anthraquinone compound, and more particularly to a liquid crystal display device using a liquid crystal composition containing an anthraquinone dichroic dye.

[0002]

2. Description of the Related Art At present, calculators and watches using twisted nematic liquid crystal display elements are commercialized. However, those using twisted nematic liquid crystal display elements use a polarizing plate to prevent ambient light. In the case of a reflective type color display using a color polarizing plate, there are drawbacks such as a dark display and a narrow viewing angle. Further, since a display element utilizing a guest-host effect in which a dichroic dye is added to liquid crystal does not necessarily require a polarizing plate, bright reflective color display is possible, and a variety of display colors can be obtained by selecting a dye to be added, It has a wide viewing angle, and
It is a display element that can adapt to the recent market diversities, such as a display with higher brightness and higher contrast if an internal illumination type (transmission type) using a polarizing plate is possible. The properties required for the dyes used in these applications include high dichroic ratio, high solubility in liquid crystals, and stability against light and electricity. In particular, a high dichroic ratio is required to improve display quality.

[0003]

However, the present situation is that it is difficult to obtain a display element having a good display quality because there are few dichroic dyes having a high dichroic ratio and a large solubility. An object of the present invention is to provide a liquid crystal display device filled with a liquid crystal composition containing a dye having a high dichroic ratio necessary for obtaining a liquid crystal display device with good display quality.

[0004]

According to the present invention, at least one of the pair of transparent electrode substrates has a structure represented by the general formula (I).

[0005]

[Chemical 2]

[Wherein one of X and Y represents a hydroxyl group and the other represents an amino group, and R represents an alkyl group which may be substituted with a hydroxyl group or a lower alkoxy group or a lower alkyl group or a lower alkoxy group. Represents a good benzyl group. Z represents an R-S- group, and is further substituted at the ortho position of the hydroxyl group among the substituents of X and Y. ] A liquid crystal display device comprising a liquid crystal composition containing one or more anthraquinone compounds represented by the formula [1]. The compound used in the liquid crystal display device of the present invention is generally synthesized as follows. That is, as shown in the following reaction formula, a compound represented by the general formula (II) is reacted with a mercaptan represented by the general formula (III) in the presence of a deoxidizing agent to give the compound represented by the general formula (I). The compound is obtained.

[0007]

[Chemical 3]

[In the formula, X, Y and R have the above-mentioned meanings, and the bromine atom is assumed to be substituted at the ortho position of the hydroxyl group. R in the general formula (I) is a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group and a dodecyl group, a hydroxyethyl group, a methoxyethyl group, ethoxy. Examples thereof include substituted alkyl groups such as ethyl group and β-ethoxypropyl group, benzyl group, and substituted benzyl groups such as methylbenzyl group, methoxybenzyl group, ethylbenzyl group and butylbenzyl group.

Next, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of a transmissive liquid crystal display device containing a liquid crystal display element of the present invention, and FIG. 2 is a sectional view of a liquid crystal display device containing a reflective liquid crystal display element of another embodiment of the present invention. It is a schematic diagram. 1 and 2, 1 is a transparent glass substrate, 2 is a transparent electrode such as indium oxide provided inside the transparent glass substrate, and 3 is a spacer made of, for example, a Teflon film, so that the cell thickness is 10 It is adjusted to ˜20 μm. Reference numeral 4 is a nematic liquid crystal composition containing a dichroic dye, and 5 is a power supply applied to the device, which uses direct current or alternating current. 6 is incident light, 7 is a viewer's eye, 8 is a polarizing plate,
9 is a light scattering plate. In this device, the surface of the transparent electrode is surface-treated by rubbing it in one direction with cotton cloth or by oblique vapor deposition of silicon oxide so that the liquid crystal and the dichroic dye are aligned parallel to the transparent electrode surface. ing.

The nematic liquid crystal exhibiting positive dielectric anisotropy used in the present invention has a general formula:

[0011]

[Chemical 4]

[0012]

[Chemical 5]

[In the formula, one of R ₂ and R ₃ represents a cyano group, and the other represents an alkyl group, an alkoxy group, an alkylphenyl group or an alkoxyphenyl group. ] A single substance or a mixture of the substances shown by Although a transmissive display device is shown in FIG. 1, a reflective display device as shown in FIG. 2 may be used. In this case, the light scattering plate 9 is provided behind the panel.

Although the display device of the type in which the color disappears when a voltage is applied has been described above, a display device which exhibits a color when a voltage is applied can be formed conversely. That is, a nematic liquid crystal exhibiting negative dielectric anisotropy is used as the liquid crystal, and the surface of the transparent electrode is a surface active agent such as N, N-dimethyl-N-octadecyl-3-aminopropyltrimethoxysilyl chloride, dimethyldichlorosilane or methyltrichlorosilane. Alternatively, the display device can be configured by aligning the liquid crystal and the dichroic dye perpendicularly to the surface of the transparent electrode by treating the liquid crystal or dichroic dye with an aligning agent such as cetyltrimethylammonium fluoride in the liquid crystal. In addition, when a small amount of cholesteric liquid crystal or chiral nematic liquid crystal is mixed with nematic liquid crystal, it becomes a display element by a so-called phase transition type (or also called white Taylor type) guest-host effect, and a polarizing plate is unnecessary and a reflective type is also available. High contrast can be obtained.

[0015]

The liquid crystal display device of the present invention is a liquid crystal display device which has a display quality with a good contrast and which meets market demands.

[0016]

EXAMPLES Next, the present invention will be described in more detail by way of examples. In the text, “part” means “part by weight”.

Example 1 4.2 parts of 1,8-diamino-4,5-dihydroxy-3,6-dibromoanthraquinone was added to 20 parts of dimethyl sulfoxide, and then 1.7 parts of caustic potash was added to obtain about 1 part. Stir for hours. 2.3 parts of i-propyl mercaptan was added to this at 30 ° C. or lower, and the mixture was stirred for 2 hours, and then at 50-60 ° C. for 1 hour.
Stir for hours. Then pour the reaction mass into 200 parts of water,
The precipitated product is filtered, washed with water and dried. The obtained crude product was purified by column chromatography using silica gel as a carrier, using chloroform as a separation solvent,
2.3 parts of 1,8-diamino-4,5-dihydroxy-3,6-bis (i-propylmercapto) anthraquinone were obtained. Melting point 208-210 ° C. The characteristics of the obtained compound were examined as follows. That is,
A liquid crystal cell, which was treated so that the liquid crystal and the dichroic dye were parallel to the transparent electrode, was added to ZLI-1840 [trademark (E.
Merck AG)]], 1,8-diamino-4,5
A liquid crystal composition containing 1% of -dihydroxy-3,6-bis (i-propylmercapto) anthraquinone was added. When a voltage of about 6 V is applied to this liquid crystal display element, the bluish green liquid crystal cell changes to almost colorless, and the dichroic ratio is 11.0.
Met. Λmax of the dye in this liquid crystal display device is 662
nm and 617 nm.

Example 2 A nematic liquid crystal E8 having a positive dielectric anisotropy [registered trademark (BDH ch
liquid crystal composition prepared by dissolving 1% of the dye obtained in Example 1 into a mixed liquid crystal prepared by adding 10% (by weight) of the cholesteric liquid crystal material cholesteryl chloride. In the configuration of FIG. 2, this liquid crystal display element is colored in bluish green when no voltage is applied, and becomes colorless when a voltage of about 15 V or more is applied, and a bright, high-contrast reflective display without using a polarizing plate. was gotten. As the cholesteric liquid crystal material used for the mixed liquid crystal, in addition to the above cholesteryl chloride, a cholesteryl derivative, a biphenyl or an ester type chiral nematic material can be similarly used.

Examples 3 to 14 The dyes shown in the following table were synthesized, and the dichroic ratio was measured in the same manner as in Example 1.

[0020]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a transmissive liquid crystal display device using a liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a reflective liquid crystal display device according to another embodiment of the present invention.

[Explanation of symbols]

 1 Glass Plate 2 Transparent Electrode 3 Spacer 4 Liquid Crystal Composition 5 Power Supply 6 Incident Light 7 Viewer 8 Polarizing Plate 9 Light Scattering Plate

Claims (1)

[Claims] 1. Between a pair of electrode substrates, at least one of which is transparent, a compound of the general formula (I): [Wherein, X and Y each represent a hydroxyl group and the other represents an amino group, and R represents an alkyl group which may be substituted with a hydroxyl group or a lower alkoxy group, or benzyl which may be substituted with a lower alkyl or a lower alkoxy group. Represents a group. Z represents an R-S- group, and is further substituted at the ortho position of the hydroxyl group among the substituents of X and Y. ] A liquid crystal display device comprising a liquid crystal composition containing one or more anthraquinone compounds represented by the formula [1].