JPS63110280A - Dichroic dyestuff for liquid crystal display - Google Patents

Abstract

NEW MATERIAL:A compound formula I [R1 is alkyl, halogen-substituted alkyl, alkoxyalkyl, (alkyl or alkoxy-substituted)cyclohexyl or (alkyl or alkoxy- substituted)benzyl]. EXAMPLE:1, 5-Diamino-2-cyano-4, 8-dihydroxy-3-[4-(3,5,5-trimethylhexyloxy)phe nyl]anthraquinone shown by formula II. USE:A blue dyestuff for liquid crystal display. PREPARATION:A 1,5-diamino-4,8-dihydroxy-3-(4-R1-oxyphenyl)anthraquinone compound shown by formula III is cyanated with sodium prussiate in dimethyl sulfoxide by the use of ammonium bicarbonate as a catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel blue dichroic dye used in liquid crystals, a liquid crystal composition containing the dye, and a method using this composition. This invention relates to display devices.

BACKGROUND OF THE INVENTION In recent years, liquid crystal display devices have come into widespread use from the viewpoints of energy saving and miniaturization. Most of the liquid crystal display elements currently in use utilize the electro-optic effect of twisted nematic liquid crystals, and display requires a combination of two polarizing plates, which imposes many restrictions on use. The reality is what we are receiving. As an alternative liquid crystal display method, a so-called guest-host type liquid crystal display that utilizes the electro-optical effect of a colored liquid crystal composition in which a dichroic dye is dissolved in a nematic liquid crystal is being considered, and some of these are already being used in watches and home appliances. , and are beginning to be used as display elements in industrial instruments and the like.

The principle of this guest-host type liquid crystal display system is that the guest dichroic dye molecules are aligned and arranged according to the alignment of the host liquid crystal molecules. In other words, by applying an external stimulus, usually an electric field, the liquid crystal molecules change their orientation from the "off" state to the "on" state, and at the same time, the dichroic dye molecules also change their orientation. This is based on the principle that the degree of absorption of light by dye molecules in both states changes to produce a display.

The dichroic dye used here has sufficient coloring ability with a small amount of fill, (2) exhibits large contrast, (3) has sufficient compatibility with liquid crystal, and (4)
) The minimum requirements are that the device has excellent durability, is stable, and does not deteriorate the performance of the device even after long periods of use.

Various dichroic dyes have been proposed as meeting the above conditions, and some have already begun to be used in digital clocks, meters, etc., but those that exhibit a large dichroic ratio lack durability, Although they have excellent durability, they currently have many drawbacks that still need to be improved, such as not having enough dichroism to provide clear display for practical use.

5. In order to solve the problem, the inventors of the present invention conducted intensive studies based on the above situation, and as a result, they discovered a new blue dichroic dye that has a large dichroic ratio and is excellent in durability. It was.

That is, the present invention provides dyes for liquid crystals having the formula ([) (wherein, R
1 is an optionally divided alkyl group, an alkyl group substituted with a halogen atom, an alkoxyalkyl group,
A novel blue-colored dichroic dye having an anthraquinone skeleton represented by a cyclohexyl group optionally substituted with an alkyl group or an alkoxy group, or a benzyl group optionally substituted with an alkyl group or an alkoxy group It provides:

The dichroic dye of the present invention is characterized by its anthraquinone skeleton.
A cyano group and a p-substituted phenyl group are introduced at the 3-position and 3-position, which increases the absorption intensity in the long wavelength region compared to similar known anthraquinone dichroic dyes.
Durability is significantly improved.

The liquid crystal dye according to the present invention is represented by the general formula (■), and specific examples of R in the general formula (I) include methyl, ethyl, n-pentyl, n-heptyl, n-octyl, n-nonyl, 3,5.5-trimethylhexyl, 4-chloro-n-methyl, 2-fluoroethyl, propyloxyethyl, ethoxyethyl, 4-ethyl-transcyclohexyl, cyclohexyl, 4-ethoxy-
transcyclohexyl, 4-ethylbenzyl, 4-n
-butylbenzyl, 4-ethoxyhensyl, 4-(3,
Examples include groups such as 5,5-trimethylhexyloxy)benzyl.

The dichroic dye of the present invention having general formula (I) can be easily synthesized using conventional methods.

That is, the 1,5-amino-4,8-dihydroxy-3-(4-R1-oxyphenyl)anthraquinone compound of general formula (n) (JP-A-55-123673 and JP-A-57-98581) etc.), (wherein, R1
The compound of the general formula (I) can be obtained by cyanating the same position as R4 (representing the A group) in the general formula (I) with sodium cyanide in dimethyl sulfoxide using ammonium bicarbonate as a catalyst. can..

The crude dye of general formula (I) thus obtained can be recrystallized,
A highly pure dye can be obtained by purification by column chromatography or the like.

Specific representative examples of the dichroic dye of the present invention are shown in Table-1.

The dichroic ratio shown in Table 1 is the characteristic value that most characterizes the usefulness of the novel dichroic dye of the present invention. The dichroic ratios shown in Table 1 are obtained by dissolving 1.0% of each dye in Merck liquid crystal (product number ZLI-1840), which is a typical nematic liquid crystal, and preparing a 10 μm thick sample that has been pretreated to achieve homogeneous alignment. After sealing it in a liquid crystal cell, it was placed in the optical path of a spectrophotometer, and the absorbance was measured by shining linearly polarized light parallel to the liquid crystal alignment (An), and the absorbance measured by shining linearly polarized light perpendicular to the liquid crystal alignment (8 people) ) was measured and calculated using the following formula dichroic ratio -□. All of the dichroic dyes of the present invention exhibit extremely high dichroic ratios.

The dichroic dye of the present invention can be incorporated into a liquid crystal and used as a liquid crystal composition for color display in a commonly used display device.

The liquid crystal used is, for example, 4-cyano-4°-n-
Pentylbiphenyl, 4-cyano-4'-n-propoxybiphenyl, 4-cyano-41-n-bentoxybiphenyl, 4-cyano-41,-octoxybiphenyl,
Cyano-biphenyl liquid crystal mixtures such as 4-cyano-4'-n-pentylterphenyl (e.g. Merck product code E-8), or trans-4-n-pro and
4-cyanophenyl)-cyclohexane, trans-4
-n-pentyl-(4-cyanophenyl)-cyclohexane, trans-4-n-hebutyl-(4-cyanophenyl)-cyclohexane, trans-4-n-pentyl-(41-cyanobiphenyl)-cyclohexane, etc. Examples include cyclohexane-based liquid crystal mixtures (for example, Merck & Co. product codes ZLI-1132 and ZLr-1840).

Furthermore, when an optically active substance such as cholesteryl nonanoate or optically active 4-cyano-4'-isopentylbiphenyl is added to the liquid crystal mixture and no electric field is applied, it is in a cholesteric phase state, and when an electric field is applied, the phase changes to a nematic phase state. It is also possible to use so-called chiral nematic liquid crystal mixtures. The liquid crystal is not limited to the above examples (other biphenyl liquid crystals, phenylcyclohexane liquid crystals, Schiff base liquid crystals, ester liquid crystals, pyrimidine liquid crystals, tetrazine liquid crystals, and other liquid crystals alone or in mixtures). Can be used as

The dyes according to the present invention may be used alone or in combination of two or more. The concentration of the dye to be used may be within the range where the dye can be dissolved in the liquid crystal and within the range where the dye molecules can be sufficiently controlled by the alignment of the liquid crystal molecules, but it is generally 0.01% with respect to the liquid crystal. It may be used at a concentration of ~10% by weight, preferably 0.01-5% by weight.

Further, it is also possible to mix the dichroic dye according to the present invention with other dichroic dyes or with a dye without dichroism and use the mixture to obtain a desired hue, and there are no limitations at all. The dichroic dye is dissolved in the liquid crystal by mixing a predetermined amount of the dye with the liquid crystal and stirring for a long time or by heating and stirring the liquid crystal to a temperature above which the liquid crystal becomes an isotropic liquid. It can be a liquid crystal composition.

Functions and Effects Various dichroic dyes used in conventional guest-host liquid crystal display systems have been proposed, but those that exhibit a large dichroic ratio may have poor durability, or those that have excellent durability but Although it still has drawbacks such as not having enough dichroism to enable clear display for practical purposes, the dichroic dye of the present invention has a cyano group at the 2-position and a p-group at the 3-position of the anthraquinone skeleton. By introducing a -substituted phenyl group, it has a large dichroic ratio, and at the same time, the absorption intensity in the long wavelength region increases, and the durability is significantly improved.

As described above, this dye is extremely valuable in practice.

Below, examples of synthesis of the anthraquinone dichroic dye of the present invention are shown, and Table 1 shows the structure of typical dyes, the dichroic ratio in liquid crystal, and the maximum value in Merck's liquid crystal ZLI-1840. Indicates absorption wavelength. "Parts" in Examples indicate parts by weight.

Example-1 Compound represented by the following formula, 24 parts of 1,5-diamino-4,8-dihydroxy-3-(4-(3,5,5-)limethylhexyloxy)phenyl]anthraquinone, 12 parts of sodium cyanide and 8 parts of ammonium bicarbonate in 270 parts of dimethyl sulfoxide, stirred for 1 hour at 90-95°C under nitrogen atmosphere, and the reaction mixture was discharged into 1300 parts of water. Add 5 parts of ammonium persulfate to this and leave at room temperature for 2
After stirring for a period of time, it was filtered, washed with water, and dried to obtain a compound represented by the following formula, 1.5-diamino-2-cyano-4.
, 25 parts of a crude product of ,8-dihydroxy-3-(4-(3,5,5-trimethylhexyloxy)phenyl)anthraquinone was obtained. This was dissolved in toluene and subjected to column chromatography using a column packed with silica gel. The dye Nl11 in Table 1 below was obtained by separation and purification.

Next, place Merck's liquid crystal ZLI-18401 in a small beaker.
1 part of the above-mentioned dye was added to 0.00 parts and heated to about 80° C. to make a completely clear solution.Then, the contents were left to cool, and the colored liquid crystal was sealed in a liquid crystal display element under reduced pressure.

This display device showed a blue color when no voltage was applied, and only the electrode portions became colorless when a voltage was applied, showing good contrast. Further, the dichroic ratio was 13.1 at the maximum absorption wavelength of 655r+m.

Further, light irradiation was performed for 200 hours using a sunshine weather meter, but no change was observed and good light resistance was exhibited.

Example 2 1,5-diamino-3(4-(2-(ethoxy)ethoxy)phenyl l-4,8-dihydroxyanthraquinone represented by the following formula was prepared in exactly the same manner as in Example 1 above. Cyanated to produce 1,5-diamino-2-cyano-3(4-
(2-(Ethoxy)ethoxy]phenyl l-4,8-dihydroxyanthraquinone was obtained. (3 affected dyes in Table 1). The dichroic ratio of this purified dye was 12.8 at the maximum absorption wavelength of 655 nm. Also, Sunshine Weather
In a 200 hour light exposure test using a meter, no deterioration in performance was observed and good results were shown.

Example 3 1,5-diamino-3(4-(n-hexyl)benzyloxyphphenyl)-4,8-dihydroxyanthraquinone represented by the following formula was converted into cyanopropylene in exactly the same manner as in Example 1 above. 1,5-diamino-2-cyano-3-(4-
(4-(n-hexyl)benzyloxyphphenyl)-
4,8-dihydroxyanthraquinone was obtained. (Table-1
fish 7 pigment), the dichroic ratio of this purified pigment is the maximum absorption wavelength 6
It showed 13.2 at 55 nm. Further, in a 200-hour light exposure test using a sunshine weather meter, no deterioration in performance was observed and good results were shown.

Table 1 below shows the dichroic ratios of dyes synthesized and purified according to these methods.

(Margin below) Table-1

Claims (1)

[Claims] 1) Formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 is an optionally branched alkyl group,
represents an alkyl group substituted with a halogen atom, an alkoxyalkyl group, a cyclohexyl group optionally substituted with an alkyl group or an alkoxy group, or a benzyl group optionally substituted with an alkyl group or an alkoxy group). dichroic dye for liquid crystal display.