KR20050036393A - Liquid crystalline compound having modified coumarin moiety and liquid crystalline composition comprising the same - Google Patents

Abstract

The present invention relates to a liquid crystal compound having a negative dielectric anisotropy by introducing a coumarin structure into a core group and a liquid crystal composition comprising the same, and more particularly, to a modified liquid crystal having a stronger dipole moment. The present invention relates to a novel liquid crystal compound and a liquid crystal composition using the same, which exhibit a sufficiently large negative dielectric anisotropy by introducing a coumarin structure, which can be effectively applied to a VA (vertical alignment) method, which is one of liquid crystal display modes. In the case of the compound according to the present invention, it has a large negative dielectric anisotropy, has a relatively high Tni value, has a fast response speed, suitable for various physical properties such as threshold voltage, voltage holding ratio, and stability, and includes VA, OCB, and IPS. It can be usefully used as a liquid crystal medium to operate in the electro-optic display of various modes.

Description

Liquid crystal compound having a modified coumarin structure and a liquid crystal composition comprising the same {Liquid Crystalline Compound having Modified Coumarin Moiety and Liquid Crystalline Composition comprising the Same}

The present invention relates to a liquid crystal compound comprising a modified coumarin structure and a liquid crystal composition comprising the same. More particularly, the modified coumarin structure is introduced into a core group to exhibit a sufficiently large negative dielectric anisotropy and is one of the liquid crystal display modes. The present invention relates to a novel liquid crystal compound that can be effectively applied to a VA (vertical alignment) method and a liquid crystal composition using the same.

As the modern industrial society develops into a high information age, the importance of the electronic display as a medium for transmitting various information is increasing day by day. The most common electronic display used so far is a cathod ray tube (CRT). In order to overcome the shortcomings of CRT such as large volume, heavy weight and high power consumption, various flat display devices such as liquid crystal display (LCD), field emission display (FED), plasma display panel (PDP), and electro luminescent display (ELD) Panel displays are being developed, and liquid crystal displays are emerging as the leader among them.

The liquid crystal display, which combines liquid crystal and semiconductor technology, is thin, light, and has low power consumption. Therefore, the scope of application of the liquid crystal display is rapidly expanding to the aircraft control room, medical equipment, navigation device, and measurement device, starting with the monitor of the notebook computer. However, the liquid crystal display has disadvantages such as slow response speed, narrow viewing angle, color reproducibility, and low luminance. Therefore, these disadvantages must be solved for a large screen liquid crystal display (eg, a liquid crystal TV) for video. The viewing angle here refers to an abnormal display when the notebook computer's screen is viewed from the side or bottom, which is the most problematic in the TN (twist nematic) mode used in the early liquid crystal display. To improve this, new modes such as vertical alignment (VA), inplane switching (IPS) and optically controlled birefringence (OCB) have been developed. Among them, VA, which can be vertically or horizontally aligned by the state of the electric field applied by the liquid crystal molecules, has an advantage of widening the viewing angle because one pixel may be divided into several domains. The liquid crystal for VA uses a phenomenon in which a polar substituent is substituted on the side of the molecule, so that the liquid crystal, which is standing vertically or slightly inclined while the electric field is off, applies a voltage.

The liquid crystal for VA uses the phenomenon that the liquid crystal standing in the off state is laid down when voltage is applied to the liquid crystal, which has a polar substituent, and the viewing angle can be wider than in the conventional TN mode, but the Tni falls due to the side ring and the response speed is reduced. The disadvantage is that it is slow. Large liquid crystal TVs have to use higher back light units (BLUs) than notebook computers because of their high brightness. In this case, the liquid crystal materials for TVs need to have high Tni due to the heat generated from the BLU. However, in the liquid crystal mixture, the response speed and the transition temperature generally have a trade-off relationship, so when the response speed is increased, the transition temperature tends to decrease.

Recently published US Pat. No. 6,376,030, and US Patent Publication No. 20030017279, disclose a VA made from a three-ring liquid crystal material consisting of two cyclohexane rings and one 2,3-difluorophenyl ring. The liquid crystal mixture is described. These mixtures have a negative dielectric anisotropy of -3 to -5 and have a Tni of 80 to 90 ° C, which is more successful than conventional liquid crystal mixtures for VA. The liquid crystal compound which has a thing is calculated | required.

The present inventors have diligently studied to solve the above problems, and in the case of a novel liquid crystal compound in which a modified coumarin structure is introduced into a core moiety, the present invention exhibits sufficiently large negative dielectric anisotropy, resulting in fast response in VA mode. In addition, the driving voltage is low and has a sufficiently large Tni, which is suitable for a large screen panel, and the production of the liquid crystal is relatively simple and the liquid crystal manufacturing price can be lowered.

After all, the present invention is to provide a novel liquid crystal compound having a relatively large negative dielectric anisotropy and Tni, the response speed is fast, suitable for moving picture implementation, and can be advantageously used in a large screen panel.

According to an aspect of the present invention for achieving the above object, there is provided a liquid crystal compound represented by the following formula (1):

Wherein R ₁ and R ₂ are each independently -C _n H _{2n + 1} , C _n H _{2n + 1} O-, C _n H _{2n + 1} S-, -C _n H _2n-1 (n is 1 to 15 a), -F, -Cl, -Br, -CN, -COOH, -OH, -SH, -NH 2, -NO 2, -NCS, -NC, -SF 5, -CH 2 CF 2 CH ₂ CF ₂ CH ₃ , -CH ₂ CFHCH ₂ CFHCH ₃ , --CH ₂ CF ₂ CH ₂ CFHCH ₃ or -CH ₂ CFHCH ₂ CF ₂ CH ₃ ; A ₁ and A ₂ are each independently 1,4-cyclo Hexylene group (1,4-cyclohexylene group), 1,4-phenylene group (1,4-phenylene group), cyclohexene-1,4-diyl group, 1,3 Dioxane-2,5-diyl group, pyridine-1,4-diyl group, pyrimidine-2,5 -Pyrimidine-2,5-diyl group, tetrahydropyran-2,5-diyl group or 1-sila-1,4-cyclohexylene group (1- sila-1,4-cyclohexylene group), wherein one or more hydrogen atoms in the functional group may be substituted with halogen atoms; Z ₁ and Z ₂ are each independently a single bond, -O-, -O OC-, -OCF _2- , -CF ₂ O-, -COO-, -OCO-, -CH ₂ CH _2- , -CH ₂ O-, -OCH _2- , -CH ₂ NH-, -NHCH _2- , -CH ₂ CO-, -COCH _2- , -NN-, -NON-, -CONH-, -NHCO-, -CH = CH-, or -C≡C-; X is -F, -Cl, -Br, -NCS, -CN, -OCF ₃ , or -SCF ₃ ; m and n are each independently an integer of 0 to 2, and m and n are not zero at the same time.)

According to another aspect of the present invention, there is provided a liquid crystal composition comprising the liquid crystal compound.

In the following, the present invention is described in more detail.

In the present invention, by introducing a modified coumarin moiety to the core group of the liquid crystal compound, the dielectric anisotropy is greatly increased compared to the conventional invention, and the refractive index anisotropy and Tni are also greatly increased due to the rigidity and thermal stability of the coumarin structure. Improvements were made.

In the related art, a phenyl ring or a cyclohexane ring is applied as a core group of a liquid crystal compound, and halogen atoms, such as fluorine, cyano groups, and nitro groups are introduced into the liquid crystal compound. Although dielectric anisotropy was improved, in the present invention, a coumarin derivative including a lactone ring having a dipole moment has been introduced to have a large dielectric anisotropy. In fact, the dipole moment is 3.9D for benzonitrile in which cyano groups are substituted, whereas it is increased to 4.48D for coumarin.

In addition, due to coumarin's physical properties such as rigidity, polarity, and thermal stability, refractive index anisotropy and Tni have also been greatly improved.

Preferred examples of liquid crystal compounds according to the invention include:

Although not particularly limited, the liquid crystal compound represented by Chemical Formula 1 is prepared through a synthetic route as follows.

In addition, the present invention includes a liquid crystal composition comprising the compound represented by Chemical Formulas 1 to 3. The liquid crystal composition may include a basic liquid crystal compound in addition to the compound represented by Chemical Formula 1 to appropriately adjust physical properties and various optical parameters of the liquid crystal composition. Examples of the basic liquid crystal compound that can be used in the composition of the present invention include the compounds shown in Table 1 below. The content of each component of the liquid crystal composition according to the present invention may vary in accordance with the intended use.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are only for illustrating the present invention and are not intended to limit the protection scope of the present invention.

EXAMPLE

Synthesis Example

1. Synthesis of 2-amino-4-bromotoluene

10 g (0.046 mol, 1 eq) of 4-bromo-2-nitrotoluene was dissolved in 100 ml of ethanol, 4.45 g (0.138 mol, 3 eq) of hydrazine was added, and 1 g of Pd / C was added thereto. After stirring for 4 hours at 50 ℃ extracted with ether. After drying over MgSO ₄ , the solvent was removed by filtration. The compound was obtained by recrystallization from ethanol.

2. Synthesis of 4-bromo-2-hydroxytoluene

7.5 g (0.04 mol, 1 eq) of 2-amino-4-bromotoluene was added to a solution in which 7 ml of sulfuric acid was diluted in 20 ml of water, followed by stirring. After gradually lowering the temperature to 5 ° C., a solution of 3.33 g (0.047 mol) of sodium nitrite diluted in 9 ml of water was slowly added using a dropping funnel. Next, cold water was added to the solution, followed by stirring. In another flask, 15 g of anhydrous sodium sulfate, 20 g of concentrated sulfuric acid, and 10 ml of water were added and stirred, and the solution was added and refluxed at 130 to 135 ° C. for 3 hours. Extract with ether and 10% NaHCO ₃ and again add 10% NaOH solution. Acidified with concentrated hydrochloric acid solution and extracted with ether and water. After drying over MgSO ₄ filtered to remove the solvent. This was distilled to obtain the compound.

3. Synthesis of 4-bromo-3-fluoro-2-hydroxytoluene

10 g (0.05 mol, 1 eq) of 4-bromo-2-hydroxytoluene was added to 100 ml of methylene chloride, and 16.3 g (0.064 mol, 1.2 eq) of a fluorine agent was added thereto and stirred at room temperature for 4 hours. After the reaction, the mixture was extracted with methylene chloride and washed three times with water. After drying over MgSO ₄ filtered to remove the solvent. The compound was obtained by column chromatography.

4. Synthesis of 4-bromo-3-fluoro-2-hydroxybenzyl bromide

5 g (0.025 mol, 1 eq) of 4-bromo-3-fluoro-2-hydroxytoluene was dissolved in 50 ml of ether, and 6.51 g (0.036 mol, 1.5 eq) of anhydrous NBS was added thereto, followed by stirring for 4 hours. Next, the mixture was extracted with ether and water. After drying over MgSO ₄ , the solvent was removed by filtration. The compound was obtained by column chromatography.

5. Synthesis of 7-bromo-8-fluoro-3-propylcoumarin

5 g (0.017 mol, 1 eq) of 4-bromo-3-fluoro-2-hydroxybenzyl bromide was dissolved in 50 ml of 1,4-dioxane, followed by 4.27 g (0.02 mol, 1.2 eq) and KOH of diethylpropyl malonate. 3.33 g (0.05 mol, 3.5 eq) was added thereto and refluxed for 5 hours. After the reaction, 10 ml of 20% H ₂ SO ₄ solution was added and extracted with ether. The solvent was washed with NaHCO ₃ solution, dried over MgSO ₄ and filtered. The compound was obtained by column chromatography.

6. Synthesis of 7-bromo-2,2,8-trifluoro-3-propylcoumarin

5 g (0.017 mol, 1 eq) of 7-bromo-8-fluoro-3-propylcoumarin under nitrogen was dissolved in 40 ml of CH ₂ Cl ₂ , and DAST was slowly added dropwise at −78 ° C., followed by stirring for 2 days. 100 ml of a 5% NaOH solution was added to the product, an organic layer was washed three times with a 5% HCl solution, and washed with distilled water until neutral. After drying the obtained organic layer with anhydrous MgSO ₄ , the solvent was removed to obtain 7-bromo-2,2,8-trifluoro-3-propylcoumarin.

7. Synthesis of 4-propyl-1- (2,2,8-trifluoro-3-propylcoumarin-7-yl) -cyclohexanol

3 g (0.0097 mol, 1 eq) of 7-bromo-2,2,8-trifluoro-3-propylcoumarin under nitrogen were dissolved in 200 ml of THF and cooled to −80 ° C. using an acetone-liquid nitrogen bath. Here, 9.1 mL of n-butyllithium (0.014 mol, 1.5eq; 1.6 M n-butylithium diluted in hexane) was carefully added so as not to exceed -70 ° C. After stirring at −80 ° C. for 10 minutes, 1.96 g (0.014 mol, 1.5 eq) of 4-propylcyclohexane was dissolved in 20 m 1 of THF, and added at 20 ° C. or lower over 20 minutes. After addition, the mixture was allowed to stand at room temperature and then the reaction product was extracted with 0.1 N HCl, distilled water and ether, dried over anhydrous MgSO _4, and distilled under reduced pressure to obtain a yellow substance.

8. Synthesis of 2,2,8-trifluoro-3-propyl-7- (4-propylcyclohexenyl) coumarin

Dissolve 3 g (0.0081 mol, 1 eq) of 4-propyl-1- (2,2,8-trifluoro-3-propylcoumarin-7-yl) -cyclohexanol in 100 ml of toluene and add p-toluene sulfonic acid ( 0.16 g (0.0008 mol, 0.1eq) of p-toluenesulfornic acid, 1-hydrate) was added and refluxed for 3 hours. After confirming completion of the reaction by TLC, the mixture was extracted with saturated NaHCO ₃ solution, toluene and distilled water, dried over anhydrous MgSO ₄ , and distilled under reduced pressure to obtain a brown substance.

9. Synthesis of 2,2,8-trifluoro-3-propyl-7- (4-propylcyclohexyl) coumarin

Dissolve 2.5 g (0.0071 mol, 1 eq) of 2,2,8-trifluoro-3-propyl-7- (4-propylcyclohexenyl) coumarin in 100 mL of toluene and 100 mL of ethanol and add 0.5 g of 10% activated Pd / C was added and then stirred at room temperature for 12 hours under a hydrogen pressure of 5 atm. After the reaction was completed, Pd / C was filtered through celite, and the solvent was distilled off under reduced pressure to obtain a brown substance. The obtained material was subjected to column chromatography (hexane: EA = 10: 1) and recrystallization (Ethanol) to obtain colorless crystals.

Liquid crystal characteristic evaluation

The dielectric anisotropy (Δε) and refractive index anisotropy (Δn) of the conventional liquid crystal compounds shown in Table 1 and the liquid crystal compounds according to the present invention shown in Tables 2 and 3, respectively, are obtained, and the results are shown in Tables 1 and 2, respectively. It was.

The above formulas (I) to (VI) have structures as indicated below.

In the case of the compound according to the present invention, it has a large negative dielectric anisotropy, has a relatively large Tni value, has a low viscosity, has a fast response speed, and has various properties such as threshold voltage, voltage holding ratio, and stability, and various modes including VA. It can be usefully used as a liquid crystal medium in.

Claims (3)

Liquid crystal compounds represented by the following formula (1) to (3): [Formula 1] [Formula 2] [Formula 3] Wherein R ₁ and R ₂ are each independently -C _n H _{2n + 1} , C _n H _{2n + 1} O-, C _n H _{2n + 1} S-, -C _n H _2n-1 (n is 1 to 15 a), -F, -Cl, -Br, -CN, -COOH, -OH, -SH, -NH 2, -NO 2, -NCS, -NC, -SF 5, -CH 2 CF 2 CH ₂ CF ₂ CH ₃ , -CH ₂ CFHCH ₂ CFHCH ₃ , --CH ₂ CF ₂ CH ₂ CFHCH ₃ or -CH ₂ CFHCH ₂ CF ₂ CH ₃ ; A ₁ and A ₂ are each independently 1,4-cyclo Hexylene group (1,4-cyclohexylene group), 1,4-phenylene group (1,4-phenylene group), cyclohexene-1,4-diyl group, 1,3 Dioxane-2,5-diyl group, pyridine-1,4-diyl group, pyrimidine-2,5 -Pyrimidine-2,5-diyl group, tetrahydropyran-2,5-diyl group or 1-sila-1,4-cyclohexylene group (1- sila-1,4-cyclohexylene group), wherein one or more hydrogen atoms in the functional group may be substituted with halogen atoms; Z ₁ and Z ₂ are each independently a single bond, -O-, -OO C-, -OCF _2- , -CF ₂ O-, -COO-, -OCO-, -CH ₂ CH _2- , -CH ₂ O-, -OCH _2- , -CH ₂ NH-, -NHCH _2- , -CH ₂ CO-, -COCH _2- , -NN-, -NON-, -CONH-, -NHCO-, -CH = CH-, or -C≡C-; X is -F, -Cl, -Br, -NCS, -CN, -OCF ₃ , or -SCF ₃ ; m and n are each independently an integer of 0 to 2, and m and n are not zero at the same time.) A liquid crystal composition comprising the liquid crystal compound according to claim 1. A liquid crystal display of VA, OCB or IPS method using the liquid crystal composition according to claim 2.