JPH07247480A - Dichroic dye, liquid crystal composition containing the dye and liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain a dichroic dye exhibiting blue color, having high specific voltage retention and useful for active matrix liquid crystal display element, etc. CONSTITUTION:This dichroic dye is a compound having a trifluoromethoxyanilino group and expressed by formula I [A is a phenylene, trans-cyclohexylene, a (tetrahydro)naphthylene or trans-decahydronaphthylene; R is H, a halogen, an alkyl, an alkoxyalkyl, an alkoxy or a (substituted) cyclohexyl; (n) is 0 or 1], e.g. a compound of formula II. The compound of formula is produced e.g. by reacting 1-amino-4-bromoanthraquinone-2-carboxylic acid with trifluoromethoxyaniline in the presence of a copper catalyst and reacting the resultant compound of formula III with a compound of formula IV in the presence of an acid catalyst.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art At present, liquid crystal display devices have a twisted nematic (TN) type display mode and a super twist (S).
In addition to the TN) mode, various display modes have been proposed. Among them, the guest-host (GH) type display system in which a dye is dissolved in liquid crystal is widely used as a display panel for automobiles or the like because of its characteristics such as wide viewing angle.

The characteristics of the dichroic dye used in the GH mode are as follows: 1) dichroism 2) solubility 3) light resistance 4) excellent coloring power.

Further, in a liquid crystal display element driven by active matrix using a thin film transistor or the like,
The liquid crystal material must retain the accumulated charge between frame frequencies. Therefore, it is indispensable to use a liquid crystal material having a high ability to retain accumulated charges between frame frequencies, that is, a material having a high voltage retention rate. In these liquid crystal materials, instead of the conventional liquid crystal material containing a cyano group,
It has been practiced to use a fluorine-based liquid crystal material which is usually hard to contain ionic impurities. However, when a dichroic dye is added to these liquid crystal materials, there is often a problem that the voltage holding characteristic of the host liquid crystal is greatly impaired, and this makes practical use of an active matrix drive liquid crystal display device using a guest-host liquid crystal composition difficult. It was difficult.

Regarding the dichroic dye and the guest-host liquid crystal composition to which the dichroic dye is added, the factor impairing the voltage holding characteristic is the influence of the ionic impurities contained in the dye, or the molecule of the dye. The causal relationship between the voltage holding ratio and other parameters has not been clarified, for example, it is difficult to determine whether it is due to the structure.

[0006]

DISCLOSURE OF THE INVENTION The present invention is capable of solving the above-mentioned conventional problems, in particular, a blue dichroic dye having a high voltage holding ratio, a liquid crystal composition containing the same, and a liquid crystal using the composition. The purpose is to provide a device.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above-mentioned problem of impairing the voltage holding characteristics in a guest-host liquid crystal composition, and as a result, have a tri-type represented by the general formula [I]. The inventors of the present invention have found that an anthraquinone-based dichroic dye having a fluoromethoxyanilino group exhibits a high voltage holding ratio, and have reached the present invention. That is, the gist of the present invention is the following general formula [I]

[0008]

[Chemical 2]

(In the formula, A represents a phenylene group, a trans-cyclohexylene group, a naphthylene group, a tetrahydronaphthylene group or a trans-decahydronaphthylene group, and R represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group. An alkyl group, an alkoxy group, or a cyclohexyl group which may be substituted with an alkyl group, an alkoxyalkyl group, or an alkoxy group, and n represents a number of 0 or 1.). It exists in an anthraquinone type dichroic dye having a group.

The anthraquinone type dichroic dye of the present invention is, for example, the following anthraquinone obtained by reacting 1-amino-4-bromoanthraquinone-2-carboxylic acid with trifluoromethoxyaniline in the presence of a copper catalyst. Compound

[0011]

[Chemical 3]

And R- (A) n-OH (wherein R, A,
n has the same meaning as in the general formula [I] shown above. ) Is obtained by esterifying the compound represented by the formula (1) in the presence of an acid catalyst. Specific examples of R in the general formula [I] include a hydrogen atom; a halogen atom such as a fluorine atom, a chlorine atom and a bromine atom; a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group,
C1-C10 such as octyl group, nonyl group and dodecyl group
A linear or branched alkyl group;
A linear or branched alkoxyalkyl group having a total of 1 to 14 carbon atoms such as butoxymethyl group, methoxypropyl group, ethoxyethyl group, butoxyethyl group; methoxy group, ethoxy group, propoxy group, butoxy group, pentoxy group, C1-C10 linear or branched alkoxy group such as octoxy group; cyclohexyl group; propylcyclohexyl group, butylcyclohexyl group, pentylcyclohexyl group, hexylcyclohexyl group, octylcyclohexyl group, etc. A cyclohexyl group substituted with a chain or branched alkyl group; a methoxymethylcyclohexyl group, a butoxyethylcyclohexyl group,
Total carbon number 1 to 1 such as pentoxybutylcyclohexyl group
A cyclohexyl group substituted with a linear or branched alkoxyalkyl group of 4; a linear or branched alkoxy group having 1 to 10 carbon atoms such as a methoxycyclohexyl group, a propoxycyclohexyl group, an octoxycyclohexyl group Included are substituted cyclohexyl groups.

The liquid crystal material used in the present invention is a mixture of various liquid crystal compounds represented by the structures below, a fluorine atom, a fluoromethyl group such as trifluoromethyl group, a fluoromethoxy group such as trifluoromethoxy group, and the like. A fluorine liquid crystal material composition containing a liquid crystal compound having a substituent containing a fluorine atom as a main component and having a voltage holding ratio of 95% or more even at a high temperature of 100 ° C. is mentioned.

[0014]

[Chemical 4]

(In the formula, R'and X'are each an alkyl group,
Fluoromethyl groups such as alkoxyalkyl groups, alkoxy groups, alkylphenyl groups, alkoxyalkylphenyl groups, alkoxyphenyl groups, alkylcyclohexyl groups, alkoxyalkylcyclohexyl groups, alkylalkoxycyclohexylphenyl groups, halogen atoms, trifluoromethyl groups, trifluoro, etc. A fluoromethoxy group such as a methoxy group, an alkylphenylalkyl group, an alkoxyalkylphenylalkyl group, an alkylcyclohexylalkyl group, an alkoxyalkoxycyclohexylalkyl group, an alkoxyphenylalkyl group, an alkylcyclohexylphenylalkyl group, and an alkyl chain of each of the above groups The alkoxy chain may have an optically active center. The phenyl group or phenoxy group in R'and X'may be substituted with a halogen atom such as a fluorine atom or a chlorine atom, and the phenyl group in each formula is 1
Or two halogen atoms such as fluorine atom and chlorine atom may be substituted. ) The above liquid crystal compounds mainly have a positive dielectric anisotropy, but a known liquid crystal having a negative dielectric anisotropy is mixed with a liquid crystal having a positive dielectric anisotropy to form a positive liquid crystal material as a whole. Can be used. Further, even a liquid crystal having a negative dielectric anisotropy can be used as it is by using an appropriate element structure and driving method.

Further, the above liquid crystal compound may contain additives such as an optically active substance such as cholesteryl nonanoate, an ultraviolet absorber and an antioxidant. The liquid crystal composition of the present invention is easily adjusted by dissolving the anthraquinone dichroic dye having the trifluoromethoxyanilino group represented by the general formula [I] in the above liquid crystal compound by a known method. be able to.

The amount of the dye used is 0.1 to the liquid crystal material.
15% by weight (hereinafter, wt%), preferably 0.5 to 5w
t%. The obtained guest-host liquid crystal composition has a specific voltage holding ratio, that is, (voltage holding ratio of guest-host liquid crystal composition) / (voltage holding ratio of guest-host liquid crystal material) is 0.8 or more, preferably 0.9. That is all.

By sandwiching the thus-prepared liquid crystal composition between a pair of transparent electrode substrates, at least one of which is transparent, for example, “Liquid Crystal Device Handbook, Japan Society for the Promotion of Science, 142nd Committee, Nikkan Kogyo Shimbun Issued by the company, third
Heilm described in "Pages 15 to 329", etc.
eier mode guest host, phase transition mode guest host, twisted nematic (TN) mode guest host, "Liquid Crystal Device Handbook, Japan Society for the Promotion of Science, No. 142"
Committee edition, published by Nikkan Kogyo Shimbun, pages 367 to 37
It is possible to configure various display elements to which the guest host effect such as the polymer dispersed mode guest host described in "Page 0" and the like is applied.

As described above, various modes of the liquid crystal display device can be used in the present invention, but in the phase transition mode obtained by adding an optically active substance to the nematic liquid crystal composition, the normally used polarized light is used. Since the plate becomes unnecessary, the display becomes bright, which is preferable.

[0020]

EXAMPLES The present invention will now be described in detail with reference to examples, but the invention is not limited to the following unless the gist thereof is exceeded. Example 1 1-Amino-4-bromoanthraquinone-
2-carboxylic acid 3.5 g, sodium hydrogen carbonate 2.5 g
Was dissolved in 50 ml of water and 30 ml of isopropyl alcohol to give 5.3 g of p-trifluoromethoxyaniline.
0.5 g of cuprous iodide was added and the mixture was heated to 80 ° C. and reacted at the same temperature for 9 hours. After the reaction, hot filtration was performed to adjust the pH to 4 by adding hydrochloric acid to the filtrate, and the precipitate was filtered, washed with isopropyl alcohol and water, and dried to obtain a crude crystal of an anthraquinone compound having the following structural formula.

[0021]

[Chemical 5]

1.5 g of the above-mentioned anthraquinone compound and 2.0 g of trans-pn-heptylcyclohexanol were added to 0.3 ml of p-toluenesulfonic acid in 30 ml of monochlorobenzene and heated at 125 ° C. for 8 hours at the same temperature. It was made to react. After cooling, the mixture was diluted with methanol, the precipitate was filtered, washed with water, dried, and purified by column chromatography to obtain a target anthraquinone dye represented by the following structural formula.

[0023]

[Chemical 6]

This anthraquinone dye was used as ZLI-479.
2 (manufactured by E. MERCK) was dissolved at a concentration of 1 wt% in a fluorine-based liquid crystal mixture commercially available to prepare a blue guest-host liquid crystal composition. This was coated with a polyimide-based resin, cured, and rubbed, and a glass substrate with a transparent electrode was made to face it, and the glass substrate was sealed in a cell having a gap of 9 μ so that the liquid crystal was aligned in parallel.

The absorbance (A //) for the linearly polarized light parallel to the alignment direction and the absorbance (A⊥) for the linearly polarized light perpendicular to the alignment direction of this blue-colored cell were measured, and the absorption peak (λmax: 655 nm) was measured. The order parameter (S) in

## EQU1 ## S = 0.76 was obtained as a result of obtaining from S = (A // − A⊥) / (A / ++ 2A⊥).

After firing the cell at a constant temperature of 110 ° C. for 1 hour, a pulse signal having a frame frequency of 30 Hz, a voltage of 5 V and an ON time of 60 μsec was applied at 25 ° C. to measure the voltage holding ratio. The specific voltage holding ratio, that is, (voltage holding ratio of guest-host liquid crystal composition) / (voltage holding ratio of host liquid crystal material) was calculated to be 0.97. [Example 2] The reaction was performed and purified in the same manner as in Example 1 except that n-octyl alcohol was used instead of trans-pn-heptylcyclohexanol, and an anthraquinone dye having the following structural formula was obtained. . The dye was dissolved in a fluorine-based liquid crystal mixture commercially available as ZLI-4792 (manufactured by E. MERCK) in the same manner as in Example 1 to prepare a liquid crystal cell. The order parameter was 0.70 and the specific voltage holding ratio was 0.96.

[0027]

[Chemical 7]

Example 3 Anthraquinone of the following structural formula was obtained by carrying out the reaction and purification in the same manner as in Example 1 except that 4-n-butylphenol was used instead of trans-pn-heptylcyclohexanol. A dye was obtained. The dye was added to ZLI-4792 (E. MERCK) in the same manner as in Example 1.
(Manufactured by Mfg. Co., Ltd.) to prepare a liquid crystal cell. The order parameter was 0.71 and the specific voltage holding ratio was 0.96.

[0029]

[Chemical 8]

Reference Example A liquid crystal cell was prepared in the same manner as in Example 1 using the anthraquinone type dichroic dye of the following structural formula contained in JP-A-63-165483, and the results were evaluated. The parameter was 0.70 and the specific voltage holding ratio was 0.64.

[0031]

[Chemical 9]

Example 4 Order parameter (S) and specific voltage in ZLI-4792 (manufactured by E. MERCK), which is a fluorine-based liquid crystal mixture of anthraquinone compound obtained by the method according to Example 1. The retention rate and the hue are shown in Table 1.

[0033]

[Table 1]

[0034]

The dichroic dye having a high specific voltage holding ratio and the guest-host liquid crystal composition containing the same according to the present invention enable an active matrix liquid crystal display device and constitute a display device with improved viewing angle and color tone. can do.

Claims (3)

[Claims] 1. The following general formula [I]: (In the formula, A represents a phenylene group, a trans-cyclohexylene group, a naphthylene group, a tetrahydronaphthylene group, or a trans-decahydronaphthylene group, and R represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxyalkyl group, An alkoxy group, or an alkyl group, an alkoxyalkyl group, or a cyclohexyl group which may be substituted with an alkoxy group, and n represents a number of 0 or 1)), and has a trifluoromethoxyanilino group. Anthraquinone type dichroic dye. 2. A liquid crystal composition comprising a liquid crystal compound and the anthraquinone type dichroic dye having a trifluoromethoxyanilino group according to claim 1. 3. A liquid crystal device comprising a liquid crystal composition according to claim 2 sandwiched between substrates having at least one transparent electrode.