JPH10231437A - Dichroic pigment, liquid crystal composition containing the same and liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pigment having an improved affinity (e.g. solubility) for a fluorine-containing liquid crystal and being excellent in dichroism, solubility, light resistance and tinting power by forming an azo pigment containing a fluorine-substituted alkyl. SOLUTION: The pigment is represented by formula I [wherein R<1> is an alkyl substituted with at least three F atoms; R<2> is H, an alkyl or the like; X is H, an alkyl, an alkoxyl, or formula II (wherein R<3> is H or an alkyl); formula III is formula IV; Z<1> and Z<2> are each H or methyl or may be combined with each other to form an alicyclic group or an aromatic group or a nitrogen- containing aromatic group; and (n) is 0-1]. The pigment is mixed with a liquid crystal compound of a biphenyl, phenylcyclohexane, phenylpyrimidine, cyclohexylcyclohexane or like type represented by formula V (wherein V and W are each an alkyl, an alkoxyl, an alkoxyalkyl, cyano, a halogen or the like; and Y is H, a halogen, cyano or the like) to prepare a liquid crystal composition. A liquid crystal element excellent in contrast and durability is obtained by using the liquid crystal composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art At present, various display modes other than a twisted nematic (TN) type display mode and a super twisted nematic (STN) type display mode have been proposed as liquid crystal elements. Among them, a guest-host (GH) type display system using a dye dissolved in a liquid crystal is widely used as a display panel of an automobile or the like because of a feature such as a wide viewing angle.

[0003]

The characteristics of the dichroic dye used in the GH mode are required to be excellent in dichroism, solubility, light resistance and coloring power. On the other hand, the red to blue dichroic dyes necessary for forming a black liquid crystal composition with a large market need
Dyes having a structure having an alkyl group, a nitro group or a cyano group at the terminal are known.

[0004] However, conventional dyes having a nitro group or a cyano group have great disadvantages in light fastness and solubility, and dyes having an alkyl group tend to have a pale hue such as yellowish red and bluish red. However, it is difficult to obtain a deep color hue. Further, there is a problem that conventional dyes have insufficient affinity such as solubility with respect to fluorine-based liquid crystal used in recent TFT liquid crystal devices and the like. An object of the present invention is to provide a dichroic dye having less of the above-mentioned difficulties, a liquid crystal composition containing the same, and a liquid crystal device.

[0005]

The object of the present invention is to provide the following general formula:

[0006]

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(Wherein, R ¹ represents an alkyl group substituted with three or more fluorine atoms, and R ² represents a hydrogen atom, an alkyl group, or an alkyl group substituted with three or more fluorine atoms. X Represents a hydrogen atom, an alkyl group, an alkoxy group,

[0008]

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Wherein R ³ represents a hydrogen atom or an alkyl group.

[0010]

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Wherein Z ¹ and Z ² each represent a hydrogen atom or a methyl group, and may be linked to each other to form an aliphatic ring, an aromatic ring or a nitrogen-containing aromatic ring; Represents a number from 0 to 1. This is achieved by an azo dye having a fluorine-substituted alkyl group represented by the formula (1), a liquid crystal composition containing the azo dye, and a liquid crystal element.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The azo dichroic dye used in the present invention is, for example, a compound represented by the following formula [II]:

[0013]

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A compound represented by the following formula [III]:

[0015]

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(X in formulas [II] and [III], R ¹ ,
R ² , Z ¹ , Z ² ,

[0017]

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N has the same meaning as in the general formula [I]. ) Can be synthesized by applying a known diazotization coupling reaction. Specific examples of the alkyl group substituted by three or more fluorine atoms of R ^{1 in} the above general formula [I] include 2-
Fluoroalkyl-substituted alkyl groups such as (perfluorobutyl) ethyl group and 2- (perfluorohexyl) ethyl group; partially hydrogenated fluoroalkyl substitution groups such as 2,2,3,3-tetrafluoropropyl group Specific examples of R ² include a hydrogen atom; an alkyl group such as a methyl group and an ethyl group; an alkyl group substituted with three or more fluorine atoms described above; X represents a hydrogen atom; Alkyl group such as a group, ethyl group, linear or branched butyl group; alkoxy group such as methoxy group, ethoxy group, linear or branched propoxy group, butoxy group, heptyloxy group; butylphenyl Alkyl-substituted phenyl groups such as hexylphenyl and hexylphenyl groups; alkoxy-substituted phenyl groups such as propoxyphenyl and hexyloxyphenyl groups Group; propylcyclohexyl, butylcyclohexyl group, an alkyl substituted cyclohexyl group and octyl cyclohexyl group.

Z ¹ and Z ² are linked together to form an aliphatic ring such as a part of a tetralin ring, an aromatic ring such as a part of a naphthalene ring or a nitrogen-containing aromatic ring such as a part of a quinoline ring. It may be something. The liquid crystal composition of the present invention comprises a disazo dichroic dye represented by the general formula [I] shown above, and a liquid crystal device handbook; edited by the 142nd Committee of the Japan Society for the Promotion of Science (1989); ~ 7
It can be easily prepared by mixing various liquid crystal compounds or liquid crystal compositions such as biphenyl, phenylcyclohexane, phenylpyrimidine, and cyclohexylcyclohexane exhibiting a nematic or smectic phase described on page 22 by a known method. . Examples of the liquid crystal compound used in the present invention include the following.

[0020]

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(Wherein V and W are alkyl, alkoxy, alkoxyalkyl, alkylphenyl, alkoxyalkylphenyl, alkoxyphenyl, alkylcyclohexyl, alkoxyalkylcyclohexyl, alkylcyclohexylphenyl, Cyanophenyl group, cyano group, halogen atom,
Represents a fluoromethyl group, a fluoromethoxy group, an alkylphenylalkyl group, an alkoxyalkylphenylalkyl group, an alkylcyclohexylalkyl group, an alkoxyalkoxycyclohexylalkyl group, an alkoxyphenylalkyl group or an alkylcyclohexylphenylalkyl group; It may have an optically active center. Y is a hydrogen atom,
Represents a halogen atom or a cyano group;
The phenyl group or phenoxy group therein may be further substituted with a halogen atom such as a cyano group, a fluorine atom and a chlorine atom. Further, the phenyl group in each of the above structural formulas may be further substituted with one to four halogen atoms such as a fluorine atom and a chlorine atom, and a cyano group. )

The liquid crystal composition of the present invention may contain an optically active compound which may or may not show a liquid crystal phase, such as cholesteryl nonanoate, or various kinds of compounds such as an ultraviolet absorber and an antioxidant. An additive may be contained.
An element utilizing the guest-host effect by sandwiching the liquid crystal composition obtained in this way between substrates with at least one transparent electrode [Shoichi Matsumoto, Ichiyoshi Kakuda “Latest technology of liquid crystal” Association, 34 (1983); L. F
ergason, SID85Digest, 68 (19
85) etc.].

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 In 25 ml of N-methyl-2-pyrrolidone, 5.4 g (50 mmol) of N-methylaniline and 10.3 of potassium carbonate were used.
g, the temperature was raised to 75 ° C. with stirring, and 1H, 1H,
2H, 2H-perfluorohexyl iodide25.
0 g (66 mmol) was added and reacted at the same temperature for 19 hours. Then, 70 ml of water was added to the reaction mixture, the organic layer was extracted with toluene, and purified by column chromatography to obtain 11.5 g of the desired product [VI] having the following structure.

[0024]

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Next, a disazo compound represented by the following structural formula

[0026]

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1.63 g was dissolved in 60 ml of N-methyl-2-pyrrolidone, and 4 ml of 35% hydrochloric acid was added.
Then, 0.33 g of sodium nitrite dissolved in water was added, and the mixture was reacted at this temperature for 1 hour. Then, 0.1 g of sulfamic acid was added to prepare a diazo liquid. On the other hand, 2.0 g of the coupler of the structure [VI] was mixed with 100 ml of methanol and cooled to 5 ° C. or lower, and the above diazo solution was added to cause a coupling reaction. After the reaction, an aqueous sodium hydroxide solution was added for neutralization, and the resulting precipitate was collected by filtration and purified by column chromatography to obtain a dye having the following structural formula.

[0028]

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This azo dye was used under the trade name ZLI-4792.
A red-purple guest-host liquid crystal composition was prepared by dissolving in a fluorine-based liquid crystal mixture commercially available as (E. MERCK) at a concentration of 0.2% by weight. A glass substrate with a transparent electrode, which was coated with a polyimide resin, cured and rubbed, faced, and was sealed in a cell with a gap of 50 μm configured so that the liquid crystal was in parallel alignment. The absorbance (A //) of this red-violet colored cell with respect to linearly polarized light parallel to the orientation direction and the absorbance (A 垂直) with respect to linearly polarized light perpendicular to the orientation direction were measured, and the absorption peak (λmax: 531)
nm) is calculated by the following equation:

[0030]

S = (A // − A⊥) / (A // + 2A⊥)

As a result, S = 0.77. Examples 2-1 to 2-15 The azo compound Nos. 2-1
No. 2-15 was obtained. Table 1 shows the order parameter (S) and hue in a fluorine-based liquid crystal composition of each compound: ZLI-4792 (trade name, manufactured by E. MERCK).

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

According to the present invention, it is possible to provide a dichroic dye having a high dichroism and a high tinctorial strength and exhibiting a blue-red color excellent in solubility and light resistance. A liquid crystal element having excellent contrast and durability can be advantageously manufactured.

Claims (3)

[Claims] 1. A compound of the general formula (Wherein, R ¹ represents an alkyl group substituted with three or more fluorine atoms, R ² represents a hydrogen atom, an alkyl group, or an alkyl group substituted with three or more fluorine atoms. X represents a hydrogen atom , An alkyl group, an alkoxy group, And R ³ represents a hydrogen atom or an alkyl group. Embedded image Wherein Z ¹ and Z ² each represent a hydrogen atom or a methyl group, and may be linked to each other to form an aliphatic ring, an aromatic ring, or a nitrogen-containing aromatic ring; 1
Indicates the number of An azo dye represented by). 2. A liquid crystal composition comprising the azo dye according to claim 1. 3. A liquid crystal device using the liquid crystal composition according to claim 2.