JPS6147192B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a composition for liquid crystal color display that utilizes electro-optic effects and is composed of a nematic liquid crystal and a dichroic dye. More specifically, the formula () is used in display devices that utilize the electro-optic effect of nematic liquid crystals. [In the formula (), R is an optionally branched alkyl group or cyclohexyl group having 1 to 15 carbon atoms, and X represents a hydrogen atom or an amino group.] The present invention relates to a composition for liquid crystal color display characterized by comprising a nematic liquid crystal. Color display devices using liquid crystals containing dichroic dyes as described above are well known in the field of liquid crystal technology as "guest-host" display devices, and are used for color displays on watches, calculators, televisions, etc. . The principle of this display device is that dichroic dye molecules are aligned in accordance with the orientation of liquid crystal material molecules. That is, by applying an external stimulus, usually an electric field, the liquid crystal molecules change and align from the "off" state to the "on" state, and along with this, the dichroic dye molecules also become aligned, and as a result, It is based on the principle that the degree of light absorption by dye molecules in both states changes, resulting in color display. This electro-optic effect is caused by the so-called guest-
This refers to a liquid crystal color display that utilizes the host effect. Currently, guest-host methods include methods using nematic liquid crystals with positive or negative dielectric anisotropy, and methods using liquid crystals that undergo a phase transition from a cholesteric phase to a nematic phase when an electric field is applied. The present invention is applicable to either case. Several dyes have been known as dichroic dyes that follow this principle. However, all of them are unsatisfactory in terms of practical performance.
This is one of the reasons that hinders the development and practical application of liquid crystal color display devices that apply this principle. In general, dichroic dyes used in liquid crystal color display devices that apply this principle have sufficient coloring ability in a small amount of 1°, have a large dichroic ratio of 2°, and can be used with or without voltage application. Conditions such as exhibiting large contrast due to addition, sufficient compatibility with 3° liquid crystal, and 4° being highly durable and stable, and not deteriorating the performance of the device even after long-term use. Basically, it is required to have the following. The present inventors have completed the present invention as a result of extensive studies aimed at developing a dichroic dye that satisfies such requirements. In the present invention, the dichroic dye that can be used is a combination of 3-amino-1,2-dihydroxyanthraquinone and the formula () R-COCl () [formula (in parentheses, R represents an optionally branched alkyl group or cyclohexyl group having 1 to 15 carbon atoms) is heated and reacted,
The nitrated product can be synthesized by nitration using nitric acid in sulfuric acid and reduction using a reducing agent such as sodium hydrosulfide, sodium sulfate or sodium hydrosulfite. In the nitration reaction, by increasing or decreasing the amount of nitric acid used and increasing or decreasing the reaction time, mononitrated products and dinitrated products can be obtained, and by reducing the respective nitrated products, mono- and diaminated products can be obtained. A dye for inventive use is obtained. An example is shown in Table 1. The synthesized crude dye often contains inorganic salts and other impurity components, and must be purified by conventional methods such as recrystallization with an organic solvent or column chromatography. Next, a synthesis example of the anthraquinone dye according to the present invention will be described. Synthesis example 1 Synthesis of compound of dye number 3 in Table 1 To 30 g of nitrobenzene, add 12 g of 3-amino-1,2-dihydroxyanthraquinone and 9.5 g of pivalic acid chloride, stir at 200°C or higher for 8 hours, then add 30 ml of methanol and cool. The precipitate was separated, washed with methanol and dried, and the 1′-
Hydroxyanthraquinonyl-[3′・2′:d]-2
-tert-butyloxazole was obtained. Dissolve 12g of this oxazolate in 60g of concentrated sulfuric acid and add 70% nitric acid.
3.7g was added and stirred at 20°C for 4 hours. It was drained into water, and the precipitate was separated and washed with water. Dissolve the lump in 250 g of monochlorobenzene and add 60% sodium sulfide to this.
A solution obtained by dissolving 17 g in 90 ml of water was added and reacted at 92°C for 5 hours. 75 g of 38% acidic sodium sulfite solution was added, and the contents were adjusted to pH 6 with hydrochloric acid. Monochlorobenzene is distilled out using steam, the precipitate is separated, washed with water, and dried.
10 g of crude dye was obtained. The product was recrystallized and purified using monochlorobenzene to obtain a reddish-brown plate-like compound of dye number 3. This is a bright red dye that exhibits a maximum absorption wavelength of 520 mμ in toluene solution. Synthesis Example 2 Synthesis of the compound of dye number 9 in Table 1 In the nitration reaction in Synthesis Example 1, 70% nitric acid
The reaction was carried out in the same manner except that the dinitro compound obtained by reacting at 50° C. for 5 hours using 8.7 g was reduced with 25 g of 60% sodium sulfide. Recrystallization was performed using monochlorobenzene to obtain the compound of dye number 9 in the form of dark purple platelets. This has a maximum absorption wavelength in toluene solution.
It is a reddish-purple dye with a diameter of 523 mμ. Other dichroic dyes used in the present invention can be synthesized in exactly the same manner by using various compounds represented by the above formula () in place of pivalic acid chloride. Table 1 shows the structural formulas of typical dichroic dyes.

【table】

[Table] The obtained dyes are all in toluene solution.
It is a vivid red to reddish-purple dye with maximum absorption wavelength around 520 to 530 mμ. The hue in a liquid crystal varies depending on the type of liquid crystal material used in combination, and the maximum absorption wavelength may be shifted by about 15 mμ. Next, the present invention will be explained in more detail using the drawings. 1 and 2 are schematic diagrams of a liquid crystal display device incorporating an electro-optical element according to the present invention. In the figure, a layer 1 is partially filled with a dye-colored nematic liquid crystal material and is sandwiched between two parallel glass slides 2,3. Slides 2 and 3 are spacers 4 that limit the lateral edges of layer 1.
are separated from each other by. Slides 2 and 3
has transparent electrodes 5 and 6 on each inner surface. The electrode 5 is connected to an external conductor 9 through a contact 7. Similarly, the electrode 6 is also connected to an external conductor 10 through a contact 8. electrodes 5 and 6
are rectangular in shape and are arranged facing each other. A voltage source 12 and a switch 11 connected in series with the voltage source are connected between external conductors 9 and 10. Voltage source 12 provides a direct current or low frequency alternating voltage sufficient to orient the liquid crystal molecules and dichroic dye molecules in layer 1 and place them on the inner surfaces of slides 2,3. Usually a voltage of 5 to 20 volts is sufficient. The nematic liquid crystal used in the present invention is
For example, 4-cyano-4'-n-pentylbiphenyl 43%, 4-cyano-4'-n-propoxybiphenyl 17%, 4-cyano-4'-n-pentoxybiphenyl 13%, 4-cyano-4'-n-pentoxybiphenyl 13%, A mixture of 17% cyano-4'-n-octoxybiphenyl and 10% 4-cyano-4'-n-pentylterphenyl can be mentioned. Furthermore, 5% of cholesteryl nonanoate or 3% of optically active 4-cyano-4'-isopentyl biphenyl is added to the liquid crystal mixture, and when no voltage is applied, it is in a cholesteric phase state, and when a voltage is applied, it is in a nematic phase state. It is also possible to use so-called chiral nematic liquid crystal mixtures which undergo a phase transformation. The nematic liquid crystal is not limited to the above examples, and those having a nematic liquid crystal phase exhibiting positive or negative dielectric anisotropy can be used alone or as a mixture. Furthermore, the dichroic dyes according to the present invention may be used alone or in combination of two or more kinds. The dichroic dye concentration may be within a range in which the dye molecules can be sufficiently controlled by the alignment of the liquid crystal molecules, but preferably 0.1 to
It is best to use it at a concentration of 3%. It is also possible to mix the dichroic dye according to the present invention with another dichroic dye or a dye without dichroism and use the mixture to obtain a desired hue, and there is no limitation at all. In addition, in producing such a liquid crystal display element,
Liquid crystal molecules and dichroic dye molecules are pretreated to align parallel or perpendicular to the surface of the transparent electrode. Treatment methods include simply rubbing the surface of the transparent electrode in a certain direction with a cotton cloth, etc., applying a silane compound, vapor depositing silicon oxide, etc., or applying a silane compound or vapor depositing silicon oxide and then rubbing it with a cotton cloth, etc. A method of friction in the direction, and others are mentioned. When a solution consisting of a nematic liquid crystal with positive dielectric anisotropy and the dichroic dye of the present invention is filled into a liquid crystal color display device which has been treated so that the liquid crystal and dye molecules are parallel to the surface of the transparent electrode, the display device This is a type of display device in which the red to reddish-purple color of the electrode portion disappears when a voltage is applied. In addition, in a liquid crystal color display device in which the liquid crystal and dye molecules are processed to be perpendicular to the surface of the transparent electrode,
When filled with a solution consisting of a nematic liquid crystal with negative dielectric anisotropy and a dichroic dye of the present invention, the display device is of a type in which the electrode portions are colored from red to reddish-purple by applying a voltage. becomes. Furthermore, although the display devices shown in FIGS. 1 and 2 are of a type in which transmitted light is viewed, the glass slide 2 may be replaced with an opaque reflective plate or the like, or a reflective plate may be placed after the glass slide 2. If a display device is manufactured that can be viewed from the front, the display device can be a reflective display device. As described above, there are a wide variety of liquid crystals and methods used in implementing the liquid crystal color display device using the dichroic dye according to the present invention, but essentially all of them utilize the electro-optic effect of nematic liquid crystals. This can be regarded as a guest-host display method. Although typical examples will be specifically explained below, the present invention is not limited to these examples in any way. Example 1 In the display device shown in FIGS. 1 and 2, silicone KF-99 (a silicone compound manufactured by Shin-Etsu Chemical Co., Ltd.) was coated on the surfaces of transparent electrodes 5 and 6.
Dye number 11 in Table 1 is applied to layer 1 of this display element.
0.1 part by weight and 38% of 4-cyano-4'-n-pentylbiphenyl, 8% of 4-cyano-4'-n-pentoxybiphenyl, 23% of 4-cyano-4'-n-heptylbiphenyl, 4-cyano-4'-heptoxybiphenyl 8%, 4-cyano-4'-n-octoxybiphenyl 10%, 4-cyano-4'-n-pentylterphenyl 10%, optical rotation 4-cyano Liquid crystal mixture consisting of 3% -4'-isopentyl biphenyl
9.9 parts by weight of colored liquid crystal solution was sealed. A plastic film with a thickness of 10 mm was used as the spacer 4. This display device appeared to be strongly colored reddish-purple when the switch 11 was open. When the switch 11 was closed and an AC voltage of 60 Hz and 20 V was applied, the portion where the transparent electrodes 5 and 6 faced each other became almost colorless. When the switch 13 was opened, the reddish-purple coloring state was shown again. When the display device was placed in the optical path of a spectrophotometer, the maximum absorption wavelength was 530 mμ, and at this wavelength, when the switch 13 was opened and closed, the absorbance ratio was 1:6, indicating good dichroism. Furthermore, when the display device was irradiated with visible light having a wavelength of 400 mμ or more for a long time, no change was observed in hue, absorbance, etc., and the display device had exactly the same performance as immediately after preparation.

[Brief explanation of the drawing]

FIG. 1 is a front view of a liquid crystal display device, and FIG. 2 is a cross-sectional view of the device along line a-a in FIG. DESCRIPTION OF SYMBOLS 1... Liquid crystal and dye layer, 2, 3... Glass slide, 4... Spacer, 5, 6... Transparent electrode, 7, 8... Contact, 9, 10... Conductive wire, 11...
...Switch, 12...Power supply.

Claims (1)

[Claims] 1 Formula () [In the formula (), R is an optionally branched alkyl group or cyclohexyl group having 1 to 15 carbon atoms, and X represents a hydrogen atom or an amino group.] A liquid crystal color display composition comprising a nematic liquid crystal.