JPS63110279A - Dichroic dyestuff for liquid crystal display - Google Patents

Abstract

NEW MATERIAL:A compound shown by formula I [R1 is alkyl, halogen- substituted alkyl, alkoxyalkyl, (alkyl-substituted)cyclohexyl or (alkyl-substituted) benzyl; R2 is H, halogen, alkoxy, aryloxyalkoxy or alkoxyalkoxy]. EXAMPLE:1, 5-Diamino-3-cyano-4,8-dihydroxy-2-[4-(n-nonyloxy)phenyl]anthraqui none shown by formula II. USE:A blue dyestuff for liquid crystal display. PREPARATION:A 1,5-diamino-4,8-dihydroxy-2-(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] Kubo fff [υ upper end t! The present invention relates to a novel blue dichroic dye used in liquid crystals, a liquid crystal composition containing the dye, and a display device using this composition.

Next 1'N1 and ■ will try to solve the problem. 1” In recent years,
Liquid crystal display elements have become widely used from the viewpoint 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 nematically dissolved in liquid crystal is being considered, and some of these have already been used for watches, watches, etc. It is beginning to be used as a display element in home appliances, industrial meters, etc.

The principle of this guest-host type liquid crystal display system is that dichroic dye molecules, which are guests, are aligned and arranged according to the arrangement of liquid crystal molecules, which are hosts; that is, by applying an external stimulus, usually an electric field. As a result, the liquid crystal molecules change their orientation from the "off" state to the "on" state, but at the same time, the dichroic dye molecules also change their orientation, resulting in a change in the degree of light absorption by the dye molecules in both states. It is based on the principle that the information is displayed.

The dichroic dye used here must (I) have sufficient coloring ability in a small amount, (2) exhibit large contrast, (3) have sufficient compatibility with liquid crystals, 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.

As a result of intensive studies based on these circumstances, the present inventors have discovered a new blue dichroic dye that has a large dichroic ratio and is excellent in durability. It has arrived.

That is, the present invention provides a liquid crystal dye having the formula (I) (wherein R
, is an optionally branched alkyl group, an alkyl group substituted with a halogen atom, an alkoxyalkyl group,
A cyclohexyl group which may be substituted with an alkyl group or an alkoxy group, or a benzyl group which may be substituted with an alkyl group or an alkoxy group, and R2 is a hydrogen atom, a halogen atom, an alkoxy group, an aryloxydialkoxy group, The present invention provides a dichroic dye having a novel blue-colored anthraquinone skeleton represented by an alkoxyalkoxy group.

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

Specific examples of R3 in -S formula (+) are methyl, ethyl, n-pentyl, n-heptyl, n-octyl, n
-nonyl, 3,5.5-trimethylhexyl, 4-chloro-n-butyl, 2-fluoroethyl, propyloxyethyl, ethoxyethyl, 4-ethyl-transcyclohexyl, cyclohexyl, 4-ethoxy-transcyclohexyl, 4 -ethylbenzyl, 4-n-butylbenzyl, 4-ethoxybenzyl, 4-(3,5,5-
)trimethylhexyloxy)benzyl, etc., and R2 in the -C formula (I) is a hydrogen atom, a chlorine atom, a bromine atom, ethoxy, butoxy, phenoxyethoxy, 4-ethylphenoxyethoxy, n
The general formula (I) of the dichroic dye of the present invention, which includes groups such as -butyloxyethoxy and ethoxyethyne, can be easily synthesized using conventional methods.

That is, the compound of general formula (I) has 1 of general formula (■)
,5-diamino-4,8-dihydroxy-2-(4-R
(dioxyphenyl) anthraquinone compound (Japanese Patent Application Laid-open No. 1983
-155054 and JP-A-59-68371, etc.) in dimethyl sulfoxide, using ammonium bicarbonate as a catalyst, and cyanating with sodium cyanide.

(In the formula, R and R2 are R2, R, in the general formula (+),
).

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 ratio shown in Table 1 is calculated by dissolving 1.0% by weight of each dye in Merck's liquid crystal (product number ZL [-1840), which is a typical nematic liquid crystal, and preparing a 10 μm thick sample that has been pretreated to achieve homogeneous orientation. The absorbance (Au) was measured by applying linearly polarized light parallel to the liquid crystal alignment, and the absorbance (A) was measured by applying linearly polarized light perpendicular to the liquid crystal alignment. ) and calculated from the following formula. 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-4'-n-pentoxybiphenyl, 4-cyano-4'-n-octoxybiphenyl, 4-cyano-4°-n- Cyano-biphenyl liquid crystal mixtures such as pentylterphenyl (for example, Merck & Co., Ltd. product code E-8), or trans-4-n-propyl-(4-cyanophenyl)-cyclohexane, trans-4-n-hentyl-(4 -cyanophenyl)-cyclohexane, trans-4-n-hebutyl-(4-cyanophenyl)-cyclohexane, trans-4-n-
Examples include cyclohexane-based liquid crystal mixtures such as pentyl-(4'-cyanobiphenyl)-cyclohexane (for example, Merck & Co. product symbols ZLI-1132 and ZLI-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 crystals are not limited to the above examples, and may include 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 as a mixture. Can be used.

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 distribution of the dye molecules can be sufficiently controlled by the orientation of the liquid crystal molecules, but - generally, the concentration is 0.0000% with respect to the liquid crystal. It is preferable to use it at a concentration of 0.01 to 10%, preferably 0.01 to 5%.

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.

A variety of dichroic dyes have been proposed for use in conventional guest-host liquid crystal display systems, but those that exhibit large dichroic ratios lack durability or lack durability. Although the dichroic dye of the present invention still has some drawbacks, such as not having enough dichroism to enable clear display for practical purposes, the dichroic dye of the present invention It is characterized by introducing a P-substituted phenyl group and a cyano group, respectively, and has a large dichroic ratio, an increase in absorption intensity in the long wavelength region, and a marked improvement in durability.

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

Overview ■ The synthesis side of the anthraquinone dichroic dye of the present invention is shown below, and Table 1 shows the groove structure of typical dyes, the dichroic ratio in liquid crystal, and the maximum in Merck's liquid crystal ZLI-1840. "Parts" in Examples, which indicate absorption wavelengths, indicate parts by weight.

Example-1 1,5-diamino-4,8-dihydroxy- represented by the following formula % formula %
24 parts of 2-[4-(n-nonyloxy)phenyl]anthraquinone, 12 parts of sodium cyanide, and 8 parts of ammonium bicarbonate were added to 270 parts of dimethyl sulfoxide, and the mixture was stirred at 90 to 95°C for 1 hour under a nitrogen atmosphere. was discharged into 1300 parts of water. To this was added 5 parts of ammonium persulfate, stirred at room temperature for 2 hours, filtered, washed with water, and dried to obtain a compound represented by the following formula, 1.5-diamino-3-cyano-4.
,8-dihydroxy-2-(4-(n-nonyloxy)
A crude product of phenyl]anthraquinone was obtained. This was dissolved in toluene and separated and purified by column chromatography using a column packed with silica gel.
A dye No. 1 was obtained.

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

The dichroic ratio of this purified dye was 12.7 at a maximum absorption wavelength of 657 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.

1,4-diamino-5,8-dihydroxy- shown in Example 2
2[4-(n-octyloxy)phenyl)-6-(2
- Phenoxyethoxyphanthraquinone was cyanated according to the same original method as in Example 1 to produce 1,4-diamino-3-cyano-5,8-dihydroxy-2-(4-(n-octyloxy) represented by the following formula. Phenyl]-6-(2-phenoxyethoxyphanthraquinone was obtained (4 dyes in Table 1). The dichroic ratio of this purified dye was 13.6 at the maximum absorption wavelength of 656 nllll.
In a 200 hour light 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.

(Hereafter, margin) 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,
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, and R_2 is hydrogen. A dichroic dye for liquid crystal display represented by an atom, a halogen atom, an alkoxy group, an aryloxyalkoxy group, or an alkoxyalkoxy group.