JPH0625307B2 - Cyanobiphenyl type dichroic azo dye for liquid crystal display - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel dichroic dye of yellow to blue type used for liquid crystals, a liquid crystal composition containing the dye, and a display using this composition. It relates to the device.

Problems to be Solved by Conventional Techniques and Inventions In recent years, liquid crystal display devices have been widely used from the viewpoint of energy saving and miniaturization. Most of the liquid crystal display elements currently in use utilize the electro-optical effect of twisted nematic liquid crystal, and display is made with the requirement of combining two polarizing plates. The reality is that there are many restrictions. As an alternative liquid crystal display method, a so-called guest-host type liquid crystal display utilizing the electro-optical effect of a colored liquid crystal composition in which a dichroic dye is dissolved in nematic liquid crystal has been studied, and some of them have already been considered as watches and home appliances. It has begun to be used as a display element in products and industrial instruments.

The principle of this guest-host liquid crystal display system is that the dichroic dye molecules that are guests are aligned and arranged according to the arrangement of the liquid crystal molecules that are hosts. That is, when an external stimulus, which is usually an electric field, is applied, the liquid crystal molecules change their alignment direction from the “off” state to the “on” state, but at the same time, the dichroic dye molecules also change their alignment direction. Based on the principle that the degree of light absorption by dye molecules in both states changes, and display is performed.

The dichroic dye used here has (1) sufficient coloring ability even in a small amount, (2) has a large dichroic ratio, and shows a large contrast when no voltage is applied. ) Basically, it must have sufficient compatibility with liquid crystal, (4) excellent durability, stability, and not deteriorate the performance of the device even if it is used for a long time. It is necessary.

Various dichroic dyes have been proposed to meet the above conditions, and some have already begun to be used in digital clocks, meters, etc., but those exhibiting a large dichroic ratio have poor durability. At present, there are many drawbacks that need to be improved, such as excellent durability, but lacking dichroism for practically clear display.

Means for Solving the Problems The inventors of the present invention have taken these circumstances into consideration, and as a result, have conducted extensive studies, to find a novel dichroic dye having a large dichroic ratio and excellent durability. I arrived.

That is, the present invention, as a liquid crystal dye, the general formula (I) [In the formula, X is a hydrogen element, alkoxy, (R ₁ represents a hydrogen atom or a lower alkyl group, R ₂ represents a lower alkyl group or a benzyl group which may be substituted at the p-position with a phenyl group.) Or Is.

(Here, R ₃ , R ₄ , and R ₅ are each a hydrogen atom, a lower alkyl group, or a phenyl group.) Ar and Ar ′ are Or Is.

(Wherein _Y 1, _{Y 2} is a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group.) W is, = N-or = is CH-.

m represents an integer of 1 or 2, and when m is 2, Ar may be different. ] The present invention provides an azo-based dichroic dye having a new yellow to blue cyanobiphenyl skeleton.

The feature of the dichroic dye of the present invention is that a 4-cyanobiphenyl skeleton is introduced at the terminal of the molecular long axis of a disazo or trisazo polyazo compound or an azo compound having an azomethine group. Dichroism and durability are significantly improved compared to dichroic dyes.

The above X in the general formula (I) for liquid crystal dyes according to the present invention
Specific examples _{of, -H, -N (CH 3)} 2, -N (C 2 H 5) 2, -N
_{(C 3 H 7) 2,} -N (C 4 H 9) 2, _{-OCH 3, -OC 2 H 5,} -O (CH 2) 3 CH 3, -O (CH 2) 7 CH 3, -OC 2
_{H 4 OC 2 H 5, -OC} 2 H 5 CH (CH 3) CH 2 C (CH 3) 3, -O (CH 2) 11 CH 3, And so on.

Also indicated by Ar and Ar ' Specific examples of Y ₁ and Y ₂ include —H, —CH ₃ , and —C
_{2 H 5, -OCH 3, -OC} 2 H 5, -Br, -C, -F, -I, -
OH, —CN, etc., and specific examples of Ar and Ar ′ are: However, it is particularly preferable that both Y ₁ and Y ₂ are hydrogen atoms because the dichroic effect is large, and it is advantageous from the viewpoint of the purity of the reaction product and the manufacturing cost of raw materials.

The general formula (I) compound of the azo dye having a cyanobiphenyl skeleton of the present invention can be synthesized by a conventional method. For example, in the general formula (I), the compound of m = 1 is represented by the general formula (II) The 4-amino-4'-cyanobiphenyl compound represented by the formula (III) or (IV) is diazotized by a conventional method. [Wherein, _{Y 1} and _{Y 2 Y 1} and Y in the general formula (I)
Represents the same meaning as ₂ . ] To the compound represented by the formula (VII) or (VIII) by hydrolysis followed by obtaining the compound of general formula (II) or diazotized compound of general formula (V) or (VI) [In the formula, Y ₁ and Y ₂ have the same meanings as in formula (I). ] To a compound represented by the general formula (V
II) or (VIII) [In formula, Y < ₁ >, Y < ₂ > represents the same meaning as general formula (I). ] The monoazo compound represented by this is obtained.

Next, this monoazo compound is further diazotized to give a compound of the general formula (I
X) [Wherein X'is a hydroxy group, an amino group, or Represent (where the same meanings as _R 1, _{R 2} of _R 1, _{R 2} is Formula (I)). ] The disazo dye can be obtained by coupling to the compound represented by

Further, when it is desired to obtain the compound of m = 2 in the general formula (I), after further diazotizing the compounds (VII) to (VIII), (III) to (I
Coupling may be repeated for compounds V) or (V)-(VI).

When X'in the general formula (IX) is a hydroxy group, after the coupling is completed, the compound is reacted with a desired alkylating agent or acylating agent to give a substituent corresponding to X in the general formula (I) compound. X'can be converted into a base.

Further, in the compound of the general formula (VII) or (VIII), the general formula (X) [In the formula, X has the same meaning as in formula (I). ] When the compound represented by the following formula is subjected to azomethine conversion, a compound of the general formula (I) in which W is a = CH- group can be obtained.

Further, when it is desired to obtain a compound in which X in the general formula (I) is H and a phenyl group, a diazotization decomposition reaction of the compound in which X in the general formula (I) is a -NH ₂ group may be carried out.

The crude dye of the general formula (I) thus obtained can be purified by recrystallization, column chromatography or the like to obtain a highly pure dye.

Table 1 shows specific representative examples of the dichroic dye of the present invention.

The dichroic ratio shown in Table 1 is a characteristic value that most characterizes the usefulness of the novel dichroic dye of the present invention. The dichroic ratio shown in Table 1 is 1.0% by weight of each dye, which is a typical nematic liquid crystal.
CK liquid crystal (Product No. ZLI-1840) dissolved and pre-treated for homogeneous alignment 10 μm thick
After being enclosed in the liquid crystal cell of No. 1, placed in the optical path of the spectrophotometer, the absorbance measured by applying linearly polarized light parallel to the liquid crystal array (A _‖ ) and the absorbance measured by applying linearly polarized light perpendicular to the liquid crystal array (A ⊥) is measured and It is calculated from Each of the dichroic dyes of the present invention exhibits an extremely high dichroic ratio.

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

Examples of the liquid crystal used include 4-cyano-4′-n-
Pentylbiphenyl, 4-cyano-4'-n-propoxybiphenyl, 4-cyano-4'-n-pentoxybiphenyl, 4-cyano-4'-n-octoxybiphenyl, 4-cyano-4 A cyano-biphenyl-based liquid crystal mixture such as ′ -n-pentylterphenyl (for example, Merck's product code E-8), trans-4-n-propyl- (4-cyanophenyl) -cyclohexane, trans-4-n-pentyl. A cyclohexane liquid crystal mixture such as-(4-cyanophenyl) -cyclohexane, trans-4-n-heptyl- (4-cyanophenyl) -cyclohexane, trans-4-n-pentyl- (4'-cyanobiphenyl) -cyclohexane (for example, Merck. Company product symbols ZLI-1132, ZLI-1840) and the like.

Furthermore, an optically active substance such as cholesteryl nonanoate or optically active 4-cyano-4'-isopentylbiphenyl was added to the liquid crystal mixture, which was in a cholesteric phase state when no electric field was applied, and was in a nematic phase when an electric field was applied. It is also possible to use so-called chiral nematic liquid crystal mixtures which undergo a phase transition to the state. The liquid crystal is not limited to the above examples, and other biphenyl liquid crystals, phenyl cyclohexane liquid crystals, schiff base liquid crystals, ester liquid crystals, pyrimidine liquid crystals, tetrazine liquid crystals and other liquid crystals as a single substance or a mixture. Can be used.

The dye 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 in which the dye dissolves in the liquid crystal and within the range in which the dye molecules can be sufficiently aligned and controlled by the alignment of the liquid crystal molecules, but generally 0.01 to the liquid crystal. 1
It may be used at a concentration of 0% by weight, preferably 0.01 to 5% by weight.

It is also possible to mix the dichroic dye according to the present invention with another dichroic dye or a dye having no dichroism to use as a desired hue, and there is no limitation. The dichroic dye is dissolved in the liquid crystal by mixing a predetermined amount of the dye with the liquid crystal and stirring the mixture for a long period of time or by heating the liquid crystal to a temperature above the temperature at which the liquid crystal becomes an isotropic liquid. It can be a composition.

The synthesis examples of the disazo dichroic dye of the present invention are shown below,
Next, Table 1 shows structures of typical dyes, dichroic ratio in liquid crystal, and maximum absorption wavelength in liquid crystal ZLI-1840 manufactured by Merck. "Parts" in the examples indicate parts by weight. % Means% by weight.

Example 1 Formula After adding 29 parts of the compound represented by the formula to 100 parts of N, N-dimethylformamide (DMF), 35% hydrochloric acid 40
Parts were added, cooled to 5 ° C. or lower, 150 parts of 10% aqueous sodium nitrite solution was added dropwise, and the mixture was stirred at the same temperature for 2 hours, and then sulfamic acid was added to obtain a diazotized solution. After making this diazotized solution PH = 4, 100 parts of a DMF solution in which 26 parts of α-naphthylamine was dissolved was added dropwise, and the mixture was stirred at 0 to 5 ° C. for 2 hours. The reaction solution was discharged into 3000 parts of ice water, washed with excess water and dried, 40 parts of a crude product of a monoazo dye represented by

The obtained monoazo compound (5 parts) was dissolved in N, N-dimethylformamide (300 parts), 35% hydrochloric acid aqueous solution (15 parts) was added, the mixture was cooled to 5 ° C or lower, and 10% sodium nitrite aqueous solution was added.
After adding dropwise, the mixture was stirred at the same temperature for 2 hours, and then sulfamic acid was added to obtain a diazotized solution.

A solution obtained by dissolving 4.0 parts of N, N-dimethylaniline in 10 parts of N, N-dimethylformamide was added dropwise to this diazotized solution, and the mixture was stirred at 0 to 5 ° C for 2 hours. After setting PH = 4,
Add 500 parts of ice water, wash with excess water, dry, formula 6.2 parts of a dinoazo dye represented by are obtained. This was dissolved in toluene, separated and purified by column chromatography using a column packed with silica gel, and the following Table-1N was used.
A disazo dye of o.16 was obtained.

Next, in a small beaker, Merck liquid crystal ZLI-1840 1
0 part and 0.1 part of the above dye were added and heated to about 80 ° C. to obtain a completely clear solution.

Then, after the contents were left to cool, the colored liquid crystal solution was sealed in the liquid crystal display element.

This display device exhibited a reddish purple color when no voltage was applied, and when the voltage was applied, only the electrode portions became colorless, showing good contrast. The dichroic ratio was 14.2 at the maximum absorption wavelength of 542 nm.

This display device was used with a xenon fade meter (manufactured by Suga Test Instruments Co., Ltd.) at a black panel temperature of 63 ± 2 ° C.
When a light resistance test was conducted by irradiation for 0 hours, the decrease in absorbance at the maximum absorption wavelength of 542 nm was only 3%. In other words, the light retention ratio was 97%, which was a good result.

Example 2 As in Example 1, the formula Diazotization of the compound represented by formula (9), coupling with phenol at PH = 8-9, A compound represented by 0.5 parts of this compound is N, N
-Heat-dissolved in 50 parts of dimethylformamide, pyridine 2.
0 parts and 0.8 parts of propionyl chloride were added, and the mixture was stirred at 80 ° C. for 3 hours. After cooling to room temperature, add 100 parts of water, wash with excess water and dry. 0.5 parts of the compound disazo dye represented by (Table-
1 No. 14 dye) The dichroic ratio of this purified dye is at the maximum absorption wavelength of 441 nm.
It showed 13.6.

When the light resistance test was conducted in the same manner as in Example 1, the light resistance retention rate was 98%, which was a good result.

Example 3 To a solution obtained by adding 7 parts of p-phenylbenzoic acid and 7.6 parts of N, N'-dicyclohexylcarbodiimide to 200 parts of chloroform and stirring for 1 hour was added the compound of the formula 150 parts of a toluene solution containing 4.5 parts of the compound shown in was added and heated to reflux for 4 hours. After the reaction, the solvent was distilled off under reduced pressure, 150 parts of methanol was added, and the mixture was washed with excess methanol.
Dried 5.1 parts of a compound represented by (Dye No. 13 in Table-1) The dichroic ratio of this purified dye is at the maximum absorption wavelength of 440 nm.
It showed 15.6.

When the light resistance test was conducted in the same manner as in Example 1, the light resistance retention rate was 98%, which was a good result.

Example 4 Similar to Example 1, the formula The compound represented by is diazotized and coupled with α-naphthylamine to obtain a compound of the formula A compound represented by Add 5 parts of this compound and 3 parts of p-phenylbenzaldehyde to 200 parts of toluene and add 5 parts.
Heated to reflux for hours. At that time, toluene was gradually distilled off to reduce the solution amount to about half. After the reaction, the solvent was distilled off under reduced pressure, 150 parts of ethanol was added, the mixture was washed with ethanol and dried,
formula 5.6 parts of the compound represented by (Dye No. 34 in Table-1) The dichroic ratio of this purified dye is at the maximum absorption wavelength of 521 nm.
It showed 16.7.

When the light resistance test was conducted in the same manner as in Example 1, the light resistance retention ratio was 97%, which was a good result.

Example 5 Formula The compound represented by Coupling with a compound of formula A compound represented by (Dye No. 33 in Table-1) The dichroic ratio of this purified dye is at the maximum absorption wavelength of 602 nm.
It showed 19.6.

When the light resistance test was conducted in the same manner as in Example 1, the light resistance retention rate was 96%, which was a good result.

Table 1 shows the dichroic ratio and light retention of the dyes obtained by synthesis and purification according to these methods.

Comparative Example 1 Formula When the dichroic ratio of the compound represented by 1 was measured in the same manner as in Example 1, the dichroic ratio at the absorption maximum wavelength of 468 nm was 8.6, and the light retention was 84%.

Comparative example 2 formula When the dichroic ratio of the compound represented by 1 was measured in the same manner as in Example 1, the dichroic ratio was 9.2 and the light retention was 81% at the maximum absorption wavelength of 519 nm.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display area // C09K 19/60 A 7457-4H

Claims (2)

[Claims] 1. A general formula (I) [In the formula, X is a hydrogen atom, alkoxy, (R ₁ represents a hydrogen atom or a lower alkyl group, R ₂ represents a lower alkyl group or a benzyl group which may be substituted at the p-position with a phenyl group.) Or Is. (Here, R ₃ , R ₄ , and R ₅ are each a hydrogen atom, a lower alkyl group, or a phenyl group.) Ar and Ar ′ are Or Is. (Wherein _Y 1, _{Y 2} is a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group.) W is, = N-or = is CH-. m represents an integer of 1 or 2, and when m is 2, Ar may be different. ] A dichroic azo dye for liquid crystal display represented by cyanobiphenyl. 2. The dichroic azo dye for liquid crystal display according to claim ₁ , wherein Y ₁ and Y ₂ of the compound of general formula (I) are hydrogen atoms.