JPH04270254A - Ester compound,liquid crystal composition containing the same and liquid crystal display element produced by using the composition - Google Patents

Abstract

PURPOSE:To provide a new ester compound having high compatibility and large negative dielectric anisotropy and keeping liquid crystal state at low temperature. CONSTITUTION:An ester compound or formula I (R is 1-10C straight-chain alkyl; m>=1; n>=0; m+n<=8; configuration of ethylene and cyclohexane ring is trans), e.g. 4-allyloxy-2,3-dicyanophenyl trans-4'-pentylcyclohexanecarboxylate. The compound of formula I can be produced by esterifying trans-4- alkylcyclohexanecarbonyl chloride with 2,3-dicyanohydroquinone in anhydrous pyridine and alkoxylating the resultant compound of formula II with trans- alken-1-ol of formula III in tetrahydrofuran. The objective liquid crystal composition having negative dielectric anisotropy contains 1-30wt.% of at least one kind of the compound of formula I. The composition is useful as a dynamic scattering or vertically oriented guest-host type liquid crystal display element, etc.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an ester compound having a very large negative dielectric anisotropy useful as a component of a liquid crystal composition used in a liquid crystal display element, a liquid crystal composition containing the same, and a liquid crystal composition thereof. This invention relates to a liquid crystal display element using.

0002

2. Description of the Related Art Liquid crystal display devices utilize the electro-optic effect of liquid crystals, in which the optical properties of the liquid crystal display device change when the arrangement of liquid crystal molecules is changed by the application of an electric field, resulting in light modulation. Electro-optic effects used in liquid crystal display devices include dynamic scattering type (DS type) and twisted nematic type (TN type).
type), guest-host type (GH type), birefringence control type (E
Display methods such as the CB type), supertwisted nematic type (STN type), supertwisted birefringence type (SBE type), ferroelectric type, and thermal effect type are known. Further, as driving methods for operating these liquid crystal display elements, a static driving method, a dynamic driving method, an active matrix driving method, a dual frequency driving method, etc. are used.

Next, there are three types of liquid crystals used in liquid crystal display elements: smectic liquid crystal, cholesteric liquid crystal, and nematic liquid crystal, and compounds with positive and negative dielectric anisotropy exist for each liquid crystal. .

Both liquid crystals with positive and negative dielectric anisotropy are used in liquid crystal display elements, but those using liquid crystals with negative dielectric anisotropy include the DS type, the vertically aligned GH type, and the vertically aligned GH type. An ECB type (DAP type) array and a dual frequency drive type are known.

In the DS type, nematic liquid crystals with negative dielectric anisotropy in which ionic substances are dissolved are arranged horizontally or vertically, and when a voltage is applied, a vortex is generated in the liquid crystal, and when the applied voltage is further increased, this vortex becomes turbulent. It becomes a flow state, and the arrangement of liquid crystal molecules shifts to a disordered state. As a result, countless fine birefringent regions different from the surrounding arrangement are generated, and light is strongly scattered at the interface between these regions, resulting in a cloudy state.

In the vertical alignment GH type, when a dichroic dye is added to a nematic liquid crystal or chiral nematic liquid crystal with negative dielectric anisotropy, the elongated molecules of the dichroic dye are aligned parallel to the liquid crystal molecules. When the alignment of the liquid crystal molecules is changed by applying an electric field, the molecular alignment of the dichroic dye also changes accordingly, and when no electric field is applied, it is colorless and becomes darker as the voltage is increased.

In the DAP method, nematic liquid crystals with negative dielectric anisotropy are vertically aligned and placed between orthogonal polarizers. When no electric field is applied, the incident light does not undergo birefringence and cannot pass through the second polarizer. When an electric field is applied, the liquid crystal molecules are tilted, so the incident light changes to elliptically polarized light, and some of the light passes through the second polarizer, so the transmitted light is colored due to the interference effect, and the magnitude of the applied voltage changes. Various colors are shown depending on the color.

The dual-frequency driving method uses a nematic liquid crystal in which the sign of dielectric anisotropy changes from positive to negative as the frequency of the applied voltage increases, and the liquid crystal is developed by appropriately combining low and high frequencies. This is a driving method that changes the arrangement of molecules.

The threshold voltage (Vth) of the liquid crystal display element as described above is, for example, in the case of a vertically aligned GH type or DAP type,

[Equation 1] (Here, ε0 is the vacuum permittivity, Δε is the dielectric anisotropy, and k3
3 represents the bend elastic constant. ) is given by In order to lower the threshold voltage of these liquid crystal display elements, it is required that the dielectric anisotropy has a large negative value. Materials that meet such demands include:

[C7] (Refer to Japanese Patent Application Laid-open No. 118450/1983)

[Chemical formula 8] (Refer to Special Publication No. 61-26898)

Compounds such as embedded image (see Japanese Patent Publication No. 61-26899) have been proposed.

0010

[Problems to be Solved by the Invention] Among these, compound (II) has a relatively large negative dielectric anisotropy, but because its liquid crystal temperature range is higher than room temperature, it is difficult to apply a threshold voltage to the mother liquid crystal. If it is added to a sufficiently low level, crystals will precipitate or the response speed will become slow. Also, the compound (
Compound (III) has a dielectric anisotropy of -20 or more, and the compound (II
) has a very large value compared to −4 of compound (II), but like compound (II), it has a high melting point, so the addition ratio cannot be increased much, and the threshold voltage cannot be lowered sufficiently. Compound (IV) has improved the above drawbacks, has a considerably low melting point, and has a dielectric anisotropy of -17.
It is possible to greatly increase the addition ratio to ~-18, and the threshold voltage can also be further lowered. However, compound (IV) has a melting point of 80°C or higher, and it has not been possible to increase its addition ratio to a level that is satisfactory for use as a component of a practical liquid crystal composition that must maintain a liquid crystal state at -20°C. Therefore, there is a limit to the negative value of dielectric anisotropy of a liquid crystal composition containing compound (IV).

[0011] Accordingly, an object of the present invention is to provide a novel ester compound which has good compatibility and has a large negative dielectric anisotropy value. Another object of the present invention is to provide a liquid crystal composition containing the ester compound that maintains a liquid crystal state at low temperatures and has a large negative dielectric anisotropy value. Furthermore, another object of the present invention is to provide a liquid crystal display element that uses the liquid crystal composition and can be driven at low voltage.

0012

[Means for Solving the Problems] The present invention provides the general formula

[Chemical 1
0] (Here, R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8, and the ethylene and cyclohexane rings have a trans configuration. ), a liquid crystal composition containing the compound, and a liquid crystal display element using the liquid crystal composition.

The ester compound of the present invention has a very negative dielectric anisotropy value of -15 to -17, and a melting point of 60 to 7.
It has characteristics as low as 0°C and can be obtained, for example, by the scheme shown in Table 1 below.

[Table 1] (Here, R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8, and ethylene and cyclohexane rings are ) Step 1 Trans-4-alkylcyclohexanecarbonyl chloride (V) and 2,3-dicyanohydroquinone (VI) are esterified in anhydrous pyridine to form 2,3-dicyano-4-hydroxyphenyl trans-4' -alkyl cyclohexane carboxylate (
VII) is obtained.

Step 2 Compound (VII) and trans-alken-1-ol (VIII) are alkoxylated using diethyl azocarboxylate and triphenylphosphine in tetrahydrofuran-free to obtain compound (I) of the present invention. .

In the case of DS type, vertically aligned GH type and DAP type liquid crystal display elements, the component of the base liquid crystal to which the compound (I) of the present invention is added has negative or positive dielectric anisotropy. Also small liquid crystal compounds, e.g.

[Chemical formula 11]

[Chemical formula 12]

[Chemical formula 13]

[Chemical formula 14] etc. are used.

[0016] Furthermore, the components of the base liquid crystal used in the dual-frequency drive type liquid crystal display element are as follows:

[Chemical formula 15]

[Chemical formula 16] etc. are used.

When compound (I) is added to these mother liquid crystals, it is possible to add only one component thereof;
It is more preferable to add several components in combination. Further, the addition ratio is in the range of 1 to 30% by weight, but in consideration of compatibility with the mother liquid crystal, the range of 1 to 20% by weight is preferable.

The liquid crystal composition obtained in this way has a large negative dielectric anisotropy compared to conventional liquid crystal compositions, and the liquid crystal composition using this liquid crystal composition is of the GH type, DAP type, etc. The display element can be driven at low voltage.

[0019]

EXAMPLES Hereinafter, the ester compound of the present invention, a liquid crystal composition containing the same, and a liquid crystal display device using the liquid crystal composition will be explained in more detail with reference to Examples. (Example 1) (Compound) 4-allyloxy-2,3-dicyanophenyl trans-4'-pentylcyclohexanecarboxylate (in general formula (I), R=
C5H11, m=1, n=0 compound).

Step 1: 500 cm3 of anhydrous pyridine
2,3-dicyanohydroquinone (manufactured by Aldrich)
16.0 g was dissolved, and 21.6 g of trans-4-pentylcyclohexanecarbonyl chloride was added dropwise over 30 minutes while stirring on an ice-water bath, followed by further stirring overnight at room temperature. The reaction product was poured into 1500 cm3 of water, and the precipitated crystals were filtered and washed with water. Add this crystal to 500 ml of toluene
Recrystallization from cm3 yields the by-product 1,4-bis(trans-4-pentylcyclohexanecarbonyloxy)-
After removing 2,3-dicyanobenzene, the residue was further recrystallized from a mixed solvent of methanol and water to obtain 22 g of 2,3-dicyano-4-hydroxyphenyl trans-4'-pentylcyclohexanecarboxylate.

Step 2 Dissolve 6.8 g of 2,3-dicyano-4-hydroxyphenyl trans-4'-pentylcyclohexanecarboxylate, 1.8 g of allyl alcohol, and 7.9 g of triphenylphosphine in 100 cm3 of anhydrous tetrahydrofuran, and dissolve this solution. While stirring on an ice water bath, diethyl azocarboxylate 5
．． 3 g was added dropwise, and the mixture was further stirred at room temperature overnight. Tetrahydrofuran in the reaction product was distilled off, and the remaining liquid was treated with a silica gel column using chloroform as a solvent. Chloroform in the effluent was distilled off, and the residue was recrystallized from methanol to give 4-allyloxy-2,3-dicyanophenyl.
5.0 g of colorless crystals of trans-4'-pentylcyclohexanecarboxylate were obtained. The phase transition temperature of this compound was measured using DSC and the results were as follows.

embedded image (Here, C indicates a crystal and I indicates an isotropic liquid.) (Examples 2 to 8) (Compound) The following compounds were produced by the same production method as in Example 1. In addition, the measurement results of the phase transition temperatures of these compounds are also listed.

4-(3'butenyloxy)-2,3-dicyanophenyl trans-4''-propylcyclohexanecarboxylate

embedded image 4-(trans-2'-hexenyloxy)-2,3-
Dicyanophenyl trans-4'-propylcyclohexanecarboxylate

embedded image 4-allyloxy-2,3-dicyanophenyl trans-4'-butylcyclohexanecarboxylate

[
4-(trans-2'-butenyloxy)-2,3-dicyanophenyl trans-4''-butylcyclohexanecarboxylate

embedded image (Here, S1 represents a smectic phase.) 4-(trans-3′-hexenyloxy)-2,3-dicyanophenyl trans-4″-butylcyclohexanecarboxylate

embedded image (Here, S1 and S2 represent a smectic phase.)
4-(trans-2'-butenyloxy)-2,3-dicyanophenyl trans-4''-pentylcyclohexanecarboxylate

embedded image 4-(3′-butenyloxy)-2,3-dicyanophenyl trans-4″-pentylcyclohexanecarboxylate

[C24] The phase transition temperatures of Examples 1 to 8 are summarized in Table 2.

[Table 2] (Example 9) (Liquid crystal composition and liquid crystal display element) The liquid crystal composition shown in Table 3 has a dielectric anisotropy of -1.3 and a nematic-isotropic liquid phase transition point (N- Point I) is 70.2℃,
Even when stored at -20°C, no crystal precipitation or phase change was observed. Using this liquid crystal composition as a base liquid crystal, its 0
．． A liquid crystal composition prepared by mixing 90 g of 4-allyloxy-2,3-dicyanophenyl trans-4'-pentylcyclohexanecarboxylate of Example 1 with 0.10 g was sealed in a vertically aligned cell and the dielectric anisotropy was measured. However, a value of -2.7 was obtained. By extrapolation, the dielectric anisotropy of the compound of Example 1 was found to be -16.

Dichroic dye D-3 was added to the liquid crystal composition shown in Table 3.
5 (manufactured by BDH Co., Ltd.) added as a guest at 1 wt% was sealed in a vertically aligned cell with a thickness of 9 μm, and the voltage -
When the light transmittance characteristics were measured, the threshold voltage was 3.
75V, and the saturation voltage was 6.2V. Here, the threshold voltage and the saturation voltage are voltages at which the light transmittance is 90% and 10% in the voltage-light transmittance curve.

Next, N of the liquid crystal composition prepared by mixing 0.90 g of the liquid crystal composition shown in Table 2 with 0.10 g of the compound of Example 1 was prepared.
-I point was 71.4°C. D-3 to this liquid crystal composition
When 1 wt% of 5 was added, the threshold voltage was 2.2V and the saturation voltage was 3.5V.

[Table 3] (Example 10) (Liquid crystal composition and liquid crystal display element) The liquid crystal compositions shown in Table 4 were prepared and the dielectric constant-frequency characteristics were measured at 25°C, and the crossover frequency was approximately 4K.
Hz, and the dielectric anisotropy in the low frequency region was 6.0 and that in the high frequency region was -2.0.

Next, as a result of measuring the dielectric constant-frequency characteristics of a liquid crystal composition obtained by mixing 0.90 g of the liquid crystal composition shown in Table 4 and 0.10 g of the compound of Example 1, the crossover frequency was about 2 KHz, which was low. Dielectric anisotropy in frequency domain is 5.0
, that in the high frequency region was -4.0.

[Table 4]

[0026]

[Effects of the Invention] As described above, it has become clear that the ester compound of the present invention has negative and large dielectric anisotropy. Furthermore, the compound of the present invention has good compatibility with other liquid crystal compositions, and by mixing the compound of the present invention and conventional liquid crystal compositions, a liquid crystal composition with negative and large dielectric anisotropy can be obtained. , vertically aligned GH type, DAP type, etc. liquid crystal display elements using this can be driven at low voltage, and dual frequency drive type liquid crystal display elements have negative dielectric anisotropy in the high frequency region. It was confirmed that this is possible.

Claims (6)

[Claims] Claim 1: General formula [Formula 1] (where R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8 (wherein the ethylene and cyclohexane rings are in trans configuration). Claim 2: General formula [Formula 2] (wherein, R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8 1. A liquid crystal composition comprising at least one ester compound represented by the following formula (wherein the ethylene and cyclohexane rings have a trans configuration). [Claim 3] General formula [Formula 3] (wherein, R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8 1. A liquid crystal composition containing 1 to 30 weight percent of at least one ester compound represented by the following formula (wherein the ethylene and cyclohexane rings are in trans configuration). [Claim 4] General formula [Formula 4] (where R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8 1. A liquid crystal composition comprising at least one ester compound represented by the following formula (wherein the ethylene and cyclohexane rings are in trans configuration) and having negative dielectric anisotropy. [Claim 5] General formula [Formula 5] (where R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8 A liquid crystal display element comprising a liquid crystal composition containing at least one ester compound represented by the following formula (wherein the ethylene and cyclohexane rings have a trans configuration). [Claim 6] General formula [Formula 6] (where R is a linear alkyl group having 1 to 10 carbon atoms, m and n are integers satisfying m≧1, n≧0, m+n≦8 (The ethylene and cyclohexane rings are in the trans configuration.) A liquid crystal composition containing at least one type of ester compound represented by A liquid crystal display element characterized in that it is used as a birefringence control type (DAP method) liquid crystal display element.