JPH051013A - Ester compound and liquid crystal composition, and liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide a novel ester compound having a low melting point, good compatibility with conventional liquid crystal materials and a large negative value of dielectric anisotropy, useful as a component for liquid crystal compositions providing liquid crystal elements capable of being driven at a low voltage. CONSTITUTION:A compound of formula I (R is 1-10C alkyl; (m), (n) are an integer, respectively satisfying m>=1, n>=0 and m+n<=8), e.g. 3-(4'- propylbenzoyloxy)-6-allyloxyphthalonitrile. The compound is produced according to reaction scheme; i.e., esterifying a 4-allyloxybenzoic acid chloride of formula V with 3,6-dihydroxyphthalonitrile of formula IV in pyridine and subsequently alkoxylating the produced 3-(4'-alkylbenzoyloxy)-6-hydroxynitrile of formula VII with an alkene-1-ol of formula VIII in the presence of diethyl carboxylate and triphenyl phosphine in THF. The employment of a liquid crystal composition containing the compound to liquid crystal elements of vertically oriented GH type, DAP type, etc., permits to lower the voltage for driving the liquid crystal elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound useful as a component of a liquid crystal composition used in a liquid crystal display device and having a very large dielectric anisotropy, a liquid crystal composition containing the compound and a liquid crystal composition thereof. The present invention relates to a liquid crystal display device using.

[0002]

2. Description of the Related Art A liquid crystal display element is an application of the electro-optical effect of liquid crystal in which the optical properties of a liquid crystal cell are changed by changing the alignment of liquid crystal molecules when an electric field is applied to the liquid crystal cell.

The electro-optical effect used in the liquid crystal display device includes a dynamic scattering type (DS type) and a twisted nematic type (T type).
N type), guest / host type (GH type), super twisted nematic type (STN type), birefringence control type (ECB type), ferroelectric type, thermal effect type, etc. Is a static drive system, a dynamic drive system,
There are an active matrix drive system and a dual frequency drive system.

There are three types of liquid crystal materials used for liquid crystal display devices, smectic liquid crystals, cholesteric liquid crystals and nematic liquid crystals. Each liquid crystal is a compound having a positive dielectric anisotropy (Δε). Negative compounds exist, △
Known liquid crystal materials having a negative ε include a DS type, a vertically aligned GH type, a DAP type, and a dual frequency driving type.

In the DS type, nematic liquid crystals having a negative Δε in which an ionic substance is dissolved are arranged horizontally or vertically, and when an electric field is applied, a vortex flow of the liquid crystal occurs, and when the voltage is further increased, a turbulent state is formed. The molecule becomes disordered. As a result, innumerable minute birefringence regions different from the surrounding arrangement can be formed, and the phenomenon that light is strongly scattered at the boundary surface between these regions and becomes a white turbid state is used.

The vertically aligned GH type uses a nematic liquid crystal or a chiral nematic liquid crystal having a negative Δε, to which a dichroic dye is added. The dichroic dye is arranged in parallel with the liquid crystal molecules, and when the arrangement of the liquid crystal molecules is changed by applying an electric field, the dichroic dye is also changed in conjunction with the phenomenon. It is colorless when no electric field is applied, and becomes darker with increasing voltage.

In the DAP method, nematic liquid crystals having a negative Δε are vertically arranged and arranged between orthogonal polarizers. When no electric field is applied, incident light does not undergo birefringence and therefore cannot pass through the second polarizer. When an electric field is applied, the liquid crystal molecules tilt, so the incident light changes to elliptically polarized light, and part of the light passes through the second polarizer, so the transmitted light is colored due to the interference effect. . Various colors can be displayed according to the magnitude of the voltage.

In the dual frequency drive system, a special nematic liquid crystal whose sign of Δε changes from positive to negative as the frequency of the applied voltage is increased is used to combine liquid crystal molecules with a low frequency and a high frequency. This is a driving method in which the arrangement is changed, and in order to take a large negative value of Δε at a high frequency, a liquid crystal material having a large negative Δε is required.

The threshold voltage (V _th ) 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, ε ₀ is the vacuum permittivity, and k ₃₃ is the elastic constant of the bend.) It can be seen that V _th decreases as the absolute value of Δε increases.

One of the characteristics of the liquid crystal display element is that the driving voltage is low. To reduce the driving voltage, however, a liquid crystal material having a negative Δε and a large value is required from the above equation. As a liquid crystal compound that meets such demands,

[Chemical 4] Have been proposed.

[0011]

Compound (II) in the above formula
Δε is relatively negative and has a large value, but its liquid crystal temperature range is higher than room temperature, so that if V _th of the base liquid crystal is sufficiently reduced, crystals are precipitated and the response speed becomes slow.

The compound (III) has Δε of -20 or more, but its melting point is so high that the ratio of the compound (III) that can be added to the mother liquid crystal is limited and V _th cannot be sufficiently reduced.

Compound (IV) is an improvement over the drawbacks of compound (III), has a fairly low melting point, and Δε is -1.
It is as large as 7 to -18, and it is possible to considerably reduce the Vth of the mother liquid crystal.

However, the melting point of the compound (IV) is 80 ° C. or higher, and the addition ratio is increased to such an extent that Vth can be sufficiently lowered as a component of a practical liquid crystal composition which must maintain the liquid crystal state at −20 ° C. Was difficult.

Therefore, an object of the present invention is to provide a novel ester compound having a low melting point, good compatibility with conventional liquid crystal materials, and a large Δε value being negative. Another object of the present invention is to provide a liquid crystal composition containing the compound and maintaining a liquid crystal phase at low temperature and having a large negative Δε. Another object of the present invention is to provide a liquid crystal display device using the liquid crystal composition, which can be driven at a low voltage.

[0016]

The present invention has the general formula

[Chemical 5] (Here, R is an alkyl group having 1 to 10 carbon atoms, m
And n are integers satisfying m ≧ 1, n ≧ 0, and m + n ≦ 8. And a liquid crystal composition containing the compound, and a liquid crystal display device using the liquid crystal composition.

The compound (I) has a Δε value of -19 to -21.
Is very large with a negative value, and the melting point is as low as 60-90 ° C.
By mixing this compound with a conventional liquid crystal compound,
It is possible to obtain a liquid crystal composition having a sufficiently large ε.

By using the liquid crystal composition for a GH type or DAP type liquid crystal display element, a liquid crystal display element having a very low driving voltage can be obtained.

Examples of the mother liquid crystal component to which the compound (I) is added include the following liquid crystal compounds.

[Chemical 6] (Here, R and R'represent an alkyl group or an alkoxy group, and X represents F or Cl.) When compound (I) is added to these mother liquid crystals, addition of only one component is effective. It is more effective to add several components in an appropriate combination. In that case, the addition ratio can be in the range of 1 to 30% by weight, but the range of 1 to 20% by weight is preferable in consideration of the compatibility with the mother liquid crystal and the size of Δε.

Next, one example of the method for producing the compound (I) will be explained by the scheme shown in Table 1.

[Table 1] (Here, R is an alkyl group having 1 to 10 carbon atoms, m
And n are integers satisfying m ≧ 1, n ≧ 0, and m + n ≦ 8. ) Step 1 4-Alkylbenzoic Acid Chloride (V)
And 3,6-dihydroxyphthalonitrile (VI) are esterified in anhydrous pyridine to give 3- (4'-alkylbenzoyloxy) -6-hydroxyphthalonitrile (VII)
To get

Step 2 Compound ((VII) and alkene-
1-ol (VIII) was alkoxylated in anhydrous tetrahydrofuran with diethyl azodicarboxylate (DEAC) and triphenylphosphine (TPP) to give 3
-(4'-Alkylbenzoyloxy) -6-alkenyloxyphthalonitrile (I) is obtained.

[0022]

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 described in more detail with reference to Examples. [Example 1] (Production of compound) A method for producing 3- (4'-propylbenzoyloxy) -6-allyloxyphthalonitrile.

Step 1 Dissolve 16.0 g of 3,6-dihydroxyphthalonitrile (manufactured by Aldrich Co.) in 500 cm ³ of anhydrous pyridine and stir it on an ice-water bath with stirring 4-
Propylbenzoic acid chloride (18.3 g) was added dropwise over 30 minutes, and the mixture was stirred overnight at room temperature. The reaction product is 1500 cm ³ of water.
The mixture was poured into the above, the precipitated crystal was filtered, and washed thoroughly with water.
The crystals were recrystallized from 500 cm ³ of toluene and further recrystallized from a mixed solvent of methanol and water to obtain 20 g of 3- (4′-propylbenzoyloxy) -6-hydroxyphthalonitrile.

Step 2 3.1 g of 3- (4'-propylbenzoyloxy-6-hydroxyphthalonitrile,
0.9 g of allyl alcohol, 3.9 g of triphenylphosphine and 50 cm ³ of anhydrous tetrahydrofuran are dissolved,
2.6 g of diethyl azodicarboxylate was added dropwise to this solution while stirring on an ice-water bath, and the mixture was stirred overnight at room temperature. Tetrahydrofuran in the reaction solution was distilled off, and the residue was recrystallized from methanol to give 3- (4'-propylbenzoyloxy) -6-allyloxyphthalonitrile (2.1 g).
Got

The phase transition temperature of this compound was measured by DSC (diffusion temperature difference; 5 ° C./MIN) and the results were as follows.

[Equation 2] [Examples 2 to 6] (Production of compound) The following compounds were produced by the same production method as in Example 1.

3- (4'-propylbenzoyloxy)
-6- (trans-2 "-butenyloxy) phthalonitrile (Example 2)

[Equation 3] 3- (4'-Propylbenzoyloxy) -6- (trans-2 "-hexenyloxy) phthalonitrile (Example 3)

[Equation 4] 3- (4'-butylbenzoyloxy) -6- (3 "-
Butenyloxy) phthalonitrile (Example 4)

[Equation 5] 3- (4'-Butylbenzoyloxy) -6- (trans-3 "-hexenyloxy) phthalonitrile (Example 5)

[Equation 6] 3- (4'-Butylbenzoyloxy) -6-allyloxyphthalonitrile (Example 6)

[Equation 7] [Example 7] (Liquid crystal composition and liquid crystal display element) The liquid crystal compositions shown in Table 2 have Δε of -1.3 and N-I.
The point was 72 ° C., and no crystal precipitation was observed even when stored at −20 ° C. This liquid crystal composition was used as a mother liquid crystal, and 0.9 g of the liquid crystal composition was mixed with 0.1 g of 3- (4′-propylbenzoyloxy) -6-allyloxyphthalonitrile of Example 1 to prepare a liquid crystal composition. This liquid crystal composition was enclosed in a liquid crystal cell subjected to vertical alignment treatment, and Δε was measured to obtain −3.15.
Got The Δε of the compound of Example 1 was −20 by extrapolation.
Was asked.

Further, the dichroic dye D- was added to the liquid crystal composition shown in Table 1.
35 (manufactured by BDH) was added as a guest in an amount of 1 wt%, and the liquid crystal composition was sealed in a vertically aligned liquid crystal cell having a thickness of 9 μm and the voltage-light transmittance characteristics were measured. The saturation voltage was 75V and the saturation voltage was 6.2V.

A liquid crystal composition prepared by mixing 0.1 g of the compound of Example 1 and 1 wt% of D-35 with 0.9 g of the liquid crystal composition shown in Table 2 was sealed in a liquid crystal cell in the same manner as above, and voltage-light was applied. When the transmittance characteristic was measured, the threshold voltage was 2.0.
V and the saturation voltage were 3.1v.

[Table 2] [Example 8] (Liquid crystal composition and liquid crystal display element) When the liquid crystal compositions shown in Table 3 were prepared and the dielectric constant-frequency characteristics were measured at 25 ° C, the crossover frequency was about 4 kHz, and in the low frequency region. Δε was 6.0, and Δε in the high frequency region was −2.0.

Next, the same measurement was performed on a liquid crystal composition obtained by mixing 0.9 g of the liquid crystal composition shown in Table 3 with 0.1 g of the compound of Example 3, and found that the crossover frequency was 2.5 k.
Δε in the Hz, low frequency region and high frequency region were 5.0 and −4.5, respectively.

[Table 3]

[0030]

As described above, it was revealed that the ester compound of the present invention has a very large Δε value and is very large. In addition, the compound of the present invention has good compatibility with other liquid crystal compositions, and the obtained liquid crystal composition does not show crystal precipitation at low temperatures and is used for GH type or DAP type liquid crystal display devices. As a result, it was confirmed that a low-voltage driven liquid crystal display device was obtained.

Therefore, the liquid crystal composition containing the compound of the present invention is very effective in lowering the driving voltage of the liquid crystal display device of GH type, DAP type, and dual frequency driving type.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miho Yuzaka             Seiko, 3-3-5 Yamato, Suwa City, Nagano Prefecture             Epson Corporation

Claims (3)

[Claims] 1. A general formula: (Here, R is an alkyl group having 1 to 10 carbon atoms, m
And n are integers satisfying m ≧ 1, n ≧ 0, and m + n ≦ 8. And an ester compound represented by the formula: 2. A general formula: (Here, R is an alkyl group having 1 to 10 carbon atoms, m
And n are integers satisfying m ≧ 1, n ≧ 0, and m + n ≦ 8. ) A liquid crystal composition comprising at least one ester compound represented by the formula (1). . 3. A general formula: (Here, R is an alkyl group having 1 to 10 carbon atoms, m
And n are integers satisfying m ≧ 1, n ≧ 0, and m + n ≦ 8. A liquid crystal display device comprising a liquid crystal composition containing at least one ester compound represented by the formula (1).