JPH0559293A - Azo dye containing trifluoromethoxy group, liquid crystal composition containing same, and liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain the title dye which is novel, red and capable of providing a liquid crystal composition having a low threshold voltage and excellent dichroism, tinting power and light resistance by selecting a particular azo dye. CONSTITUTION:An azo dye of formula I wherein R1 and R2 are each an (alkoxy) alkyl, (substituted) aralkyl or fluoroalkyl and may combine with each other to form a nitrogenous alicyclic ring, or R1 and Z11 or R2 and Z12 may combine together to form a nitrogenous alicyclic ring; Z1 to Z12 are each H, a halogen, methyl or methoxy and two Zs on the same ring may combine together to form an alicyclic, aromatic or nitrogenous aromatic ring; and n is 0 or 1. It is prepared, for example, by subjecting a compound of formula II to v as the raw material to the known diazotization-coupling reaction in a usual manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel red azo type dichroic dye, a liquid crystal composition containing the same, and a liquid crystal device using the liquid crystal composition.

[0002]

2. Description of the Related Art At present, various display modes such as a twist nematic (TN) type display mode and a super twist (STN) type display mode have been proposed as liquid crystal display modes. Of these, the guest-host (GH) type display mode in which a dichroic dye is dissolved in liquid crystal is
Because of its wide viewing angle, it is widely used as a display panel for automobiles. The dichroic dye used in this GH type display mode is required to have excellent properties such as dichroism, solubility, light resistance and tinting strength.

On the other hand, azo dyes and anthraquinone dyes have hitherto been known as the red dichroic dyes necessary for forming a black liquid crystal composition which has a great market need. However, azo dyes generally have a problem in light resistance, and anthraquinone dyes having good light resistance have low coloring power, and dichroic dyes excellent in all of the above properties are rare.

Further, the GH type display mode has a drawback that the threshold voltage is generally higher than other display modes such as the TN type display mode, and this drawback is caused by increasing the dielectric anisotropy of the liquid crystal composition. It is desirable to reduce it. To form a liquid crystal composition having a high dielectric anisotropy, it is desirable to use a dichroic dye having a substituent having a large dielectric anisotropy. However, known dichroic dyes having a nitro group or a cyano group have a great difficulty in light resistance and solubility, and have a substituent having a large dielectric anisotropy and a highly practical red dichroic dye. Is almost unknown.

[0005]

DISCLOSURE OF THE INVENTION The present invention is to provide a dichroic dye excellent in practicability which can give a liquid crystal composition having a low threshold voltage.

[0006]

The object of the present invention is to provide the above-mentioned contract.
Anisotropy of dielectric constant represented by the general formula [1]
With a highly active trifluoromethoxy group, the end in the direction of the molecular axis
This is achieved by the azo dyes described in 1. Azo of general formula 1
The system dye is based on the compounds of the following "Chemical formula 2" to "Chemical formula 5".
As a material, a known diazotization-coupling reaction is carried out according to a conventional method.
It can be easily prepared by combining
It In the following "Chemical formula 2" to "Chemical formula 5", Z₁~
Z ₁₂And R₁, R₂Is the same as in general formula [1]
Have significance.

[0007]

[Chemical 2]

[0008]

[Chemical 3]

[0009]

[Chemical 4]

[0010]

[Chemical 5]

R ₁ and R ₂ in the above general formula [1]
Is, independently, methyl, ethyl, or a C _{1 to} C ₁₈ alkyl group such as linear or branched propyl, butyl, hexyl and octyl; and C ₂ such as ethoxymethyl, butoxymethyl, ethoxyethyl and butoxyethyl. ~ C
₁₈ alkoxyalkyl groups, benzyl, phenethyl, 4
And aralkyl groups which may have a substituent such as -butylbenzyl, 4-pentoxybenzyl, 4-chlorobenzyl, and fluoroalkyl groups such as perfluoroethylmethyl, perfluorobutylethyl, and perfluorohexylethyl. Further, R ₁ and R ₂ may be bonded to each other to form a nitrogen-containing aromatic ring such as a pyrrolidine ring, a piperidine ring or a morpholine ring. Furthermore, R ₁ and Z ₁₁ , R ₂
And Z ₁₂ may combine with each other to form a julolidine ring or a tetrahydroquinoline ring.

Z _{1 to} Z _{12 each} independently represent a hydrogen atom, a halogen atom, a methyl group or a methoxy group in addition to the combination of R ₁ and Z ₁₁ and R ₂ and Z ₁₂ to form a ring. .. Further, two Zs on the same ring may be bonded to each other to form an aliphatic ring portion of a tetralin ring, an aromatic ring portion of a naphthalene ring or a nitrogen-containing aromatic ring portion of a quinoline ring.

The liquid crystal composition of the present invention has the general formula [1] shown above.
The diazo-based dichroic dye represented by is described in "Liquid Crystal Device Handbook" [Japan Society for the Promotion of Science, 142nd Committee, (19)
89); p154 to p192, p715 to p722], known methods for various liquid crystal compounds or liquid crystal compositions such as biphenyl-based, phenylcyclohexane-based, phenylpyrimidine-based, cyclohexylcyclohexane-based exhibiting a nematic or smectic phase. It can be easily prepared by mixing with.

Further, the liquid crystal composition of the present invention may contain an optically active compound such as cholesteryl nonanoate, in which case these compounds may or may not exhibit a liquid crystal phase. The liquid crystal composition of the present invention may further contain various additives such as an ultraviolet absorber and an antioxidant. The liquid crystal element of the present invention can be formed by sandwiching the liquid crystal composition obtained as described above between, for example, at least one transparent substrate with electrodes. Regarding the device applying such a guest-host effect, "Latest Liquid Crystal Technology" [Shouichi Matsumoto, Ryo Tsunoda; Industrial Research Committee, 3
4 (1983)] and "SDI85 Digest"
[J. L. Fergason; 68 (1985)] and the like.

[0015]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples. In the examples below, the order parameter (S) was calculated as follows.

Product name ZL1-1565 [E. MERCK
The azo dye according to the present invention is dissolved to a concentration of 1 wt% in a phenylcyclohexane liquid crystal mixture that is commercially available as a company product to prepare a red guest-host liquid crystal composition. A glass substrate with a transparent electrode, which was rubbed after being coated with a polyimide resin and cured, was
A liquid crystal element is manufactured by encapsulating the above liquid crystal composition in a cell constituted by facing each other with an interval of m.

The absorbance (A //) of this element for linearly polarized light parallel to the orientation direction and the absorbance (A⊥) for linearly polarized light perpendicular to the orientation direction are measured. Absorption peak (λm
The order parameter (S) in ax) is calculated by S = (A // − A⊥) / (A // + 2A⊥).

Example 1 0.57 g of a monofluoro compound having a trifluoromethoxy group represented by the following structural formula [1-1] was added to 10 ml of acetic acid and 0.53 ml of 35% hydrochloric acid.
And dissolved in a solution of 10 ml of water and cooled to 0-5 ° C. To this, 0.14 g of sodium nitrite was added, and the mixture was reacted at this temperature for 2 hours, and then sulfamic acid 0.015 was added.
g was added to prepare a diazo solution.

A coupler solution was prepared by dissolving 0.35 g of the compound represented by the following structural formula [1-2] in 30 ml of methanol. The coupler solution was cooled to 0 to 5 ° C., and the diazo solution and 5% caustic soda aqueous solution were added alternately while stirring,
The diazo solution was added to the coupler solution while maintaining pH 4 to 5, and then the reaction was carried out at this temperature for 2 hours.

The precipitate is filtered, washed with water and dried to obtain a crude crystal, which is purified by column chromatography and then precipitated from a chloroform-methanol mixed solution to be represented by the following structural formula [1-3]. A disazo compound was obtained. S (λmax: 494 nm) = 0.75

[0021]

[Chemical 6]

[0022]

[Chemical 7]

[0023]

[Chemical 8]

Example 2 The reaction and post-treatment were carried out in the same manner as in Example 1 except that the compound of the following structural formula [2-1] was used as the coupler component.
A disazo compound represented by the following structural formula [2-2] was obtained.

S (λmax; 500 nm) = 0.75

[0026]

[Chemical 9]

[0027]

[Chemical 10]

Example 3 0.66 g of a monoazo compound having a trifluoromethoxy group represented by the following structural formula [3-1] was dissolved in a mixed solution of 7 ml of acetic acid, 4 ml of propionic acid and 1 ml of phosphoric acid, and 0 Cooled to ~ 5 ° C.
To this was added 0.71 g of 43% nitrosylsulfuric acid, the mixture was reacted at this temperature for 2 hours, and then 0.04 g of sulfamic acid was added to prepare a diazo solution.

A coupler solution was prepared by dissolving 0.69 g of the compound represented by the following structural formula [3-2] in 30 ml of methanol. The coupler solution is cooled to 0 to 5 ° C, and the diazo solution and a 5% caustic soda aqueous solution are alternately added to this while stirring to add the diazo solution to the coupler solution while maintaining the pH at 4 to 5, followed by reaction at this temperature for 2 hours. Let The precipitate was collected from the reaction solution by filtration, washed with water and dried to obtain crude crystals. The crude crystals were purified by column chromatography,
Further, it was precipitated from a chloroform-methanol mixed solution to obtain a disazo compound represented by the following structural formula [3-3].

S (λmax; 541 nm) = 0.71

[0031]

[Chemical 11]

[0032]

[Chemical formula 12]

[0033]

[Chemical 13]

Example 4 The reaction and post-treatment were carried out in the same manner as in Example 3 except that the compound of the following structural formula [4-1] was used as the coupler component, and the following structural formula [4- 2] Prepared compound.

S (λmax: 541 nm) = 0.71

[0036]

[Chemical 14]

[0037]

[Chemical 15]

Example 5 The compounds shown in Table 1 below were prepared according to Examples 1 to 4.
Table 1 shows order parameters and hues of these compounds.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

[0045]

[Table 7]

[0046]

[Table 8]

[0047]

[Table 9]

[0048]

[Table 10]

[0049]

The disazo dye according to the present invention is a red dye having high dichroism and coloring power and good light resistance. By using a liquid crystal composition containing this dye, a liquid crystal element such as a display element having excellent contrast and durability can be formed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid crystal element of the present invention in a state in which no voltage is applied.

FIG. 2 is a schematic cross-sectional view of a liquid crystal element of the present invention in a voltage applied state.

[Explanation of symbols]

 1 Observer 2 Transparent substrate 3 Transparent electrode subjected to parallel alignment treatment 4 Nematic liquid crystal molecule with positive dielectric anisotropy 5 Dichroic dye molecule 6 Incident polarization 7 Polarization direction of incident polarization 8 Polarizing light 9 Incident light

Claims (3)

[Claims] 1. The following general formula [1]:(In the formula, R₁And R₂Is an alkyl group,
Xyalkyl group, aralkyl which may have a substituent
Group or fluoroalkyl group, R₁And R ₂Are mutual
To form a nitrogen-containing aliphatic ring or R₁And Z
₁₁Or R₂And Z₁₂Combine to form a nitrogen-containing aliphatic ring
You may have. Z₁~ Z₁₂In addition to the above,
Is a hydrogen atom, a halogen atom, a methyl group or a methoxy group
, Two Zs on the same ring are bonded to each other
It may form an aliphatic ring, an aromatic ring or a nitrogen-containing aromatic ring.
Yes. n represents 0 or 1. ) Trifluo
An azo dye having a romethoxy group. 2. A liquid crystal composition containing the azo dye having a trifluoromethoxy group according to claim 1. 3. A liquid crystal device using the liquid crystal composition according to claim 2.