JPH05117206A - 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 positive and large dielectric anisotropy, high birefringence and high clear point and useful as a liquid crystal material capable of forming a TN-type or STN-type liquid crystal display element having high response speed and drivable by highly time-shared driving method at a low voltage. CONSTITUTION:The ester compound of formula I (R<1> is 1-10C alkyl; X is F, CN, SR<2> or group of formula II; Y is H or F; R<2> and R<3> are 1-10C alkyl; A is single bond or CH2CH2CH2), e.g. 4-cyanophenyl 2'-fluoro-4'-methylbenzoate. The compound can be produced by esterifying a compound of formula III (R is R<1>) with a compound of formula IV in chloroform in the presence of triethylamine. The compound of formula III can be obtained from a compound of formula V by nitration, catalytic reduction, cyanidation, hydrolysis and chlorination. The above compound has high dielectric anisotropy when X is F or CN, high birefringence when X is SR<2> and high clear point when X is group of formula II.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ester compound useful as a component constituting a liquid crystal composition used in a liquid crystal display device, a liquid crystal composition containing the compound, and a liquid crystal display device using the liquid crystal composition.

[0002]

2. Description of the Related Art There are known types of liquid crystals, such as nematic liquid crystals, cholesteric liquid crystals, and smectic liquid crystals.
Liquid crystal display devices utilizing the electro-optical effect of these liquid crystals have been widely used. Display systems used for liquid crystal display devices include dynamic scattering type, guest-host type, twisted nematic type (TN type), birefringence control type, super twisted nematic type (STN type), super twisted birefringence type, etc. There are a static driving method, a time division driving method, an active matrix driving method, a dual frequency driving method and the like as driving methods for operating these liquid crystal display elements.

A liquid crystal display element represented by a TN type or an STN type is easily (1) smaller, thinner and lighter than a light emitting type display element such as an LED, an EL or a CRT. (2) The driving voltage is low and the power consumption is very small. (3) Compatibility with LSI is good, and the drive circuit can be simplified. (4) Since it is a light-receiving element, it is easy to see even in direct sunlight, and even if it is used for a long time, the eyes do not get tired easily. And so on.

Therefore, taking advantage of these characteristics, a TN type liquid crystal display element mainly using a time-division drive system is used for a digital watch, a calculator, an audio device, a game, an automobile dashboard, a camera, a telephone, a household electric appliance. ,
Widely applied to the display of other various measuring devices,
It is expected that its application fields will further expand in the future.
Further, as the application field expands, it is required to increase the display capacity, but it has become clear that the TN type liquid crystal display element has a limit of 200 scanning lines. STN type and active matrix drive type TN type liquid crystal display elements have been developed as a large display system of STN type. Currently, STN type is being applied to word processor and personal computer displays, and active matrix drive type TN type is being applied to liquid crystal color TV. Is attracting attention as a display element to replace the CRT.

Next, the characteristics required for the liquid crystal materials used for these liquid crystal display elements are variously changed depending on the display system, the driving system, the application field, etc. It is indispensable in the device. (1) It is not colored and is stable to heat, light, electricity, and chemicals. (2) The liquid crystal temperature range should be near room temperature and as wide as possible. (3) The threshold voltage of the applied voltage-light transmittance characteristic (V-I ₀ characteristic) is low and its temperature dependence is small. (4) The steepness of the V-I ₀ characteristic is good. (5) The visual angle dependence of the V-I ₀ characteristic should be as small as possible. (6) The electro-optical response speed is fast.

[0006]

Among these various properties, a large number of liquid crystal compounds or liquid crystal analog compounds satisfying (1) have been synthesized, but (2) liquid crystal compounds satisfying the following properties with a single component. Has not been obtained so far. Therefore, as a means for satisfying these characteristics, a liquid crystal composition in which a plurality of liquid crystal compounds or liquid crystal analog compounds are mixed is used. When the liquid crystal temperature range of the liquid crystal composition is divided into its upper limit and lower limit, the lower limit can be lowered by bringing the mixing ratio of each component close to the ratio of the eutectic mixture, and the upper limit is the addition of a liquid crystal compound having a high clearing point. It is possible to raise it by doing. The threshold voltage (Vth) of the V-I ₀ characteristic is, for example, in the case of the TN type.

[Equation 1] (Where d is the thickness of the liquid crystal phase, K ₁₁ , K ₂₂ and K ₃₃ are the elastic constants of the spray, twist and bend, respectively,
ε ₀ indicates a vacuum permittivity, and Δε indicates a dielectric anisotropy. ). Therefore, in order to lower Vth, it is sufficient to add a compound having a small elastic constant and a large Δε value. Since the temperature dependence of Vth is derived from the elastic constant, it is necessary to select a compound having a small temperature dependence of the elastic constant. The steepness (β) of the V-I ₀ characteristic is defined by the following equation.
Also, β is approximate

[Equation 2] (Here, Vth is a threshold voltage, Vsat is a saturation voltage, and generally Vth is a voltage at a light transmittance of 10%, Vth
sat is the voltage when the light transmittance is 90%. ) To

[Equation 3] (Here, Δn is the birefringence, and λ is the wavelength of the incident light.)
It is represented by. Therefore, to improve β, K
_The highest steepness is obtained when ₃₃ / K ₁₁ and Δε / ε⊥ are made as small as possible and the cell condition is set to Δn · d / 2λ = 1. The viewing angle dependence (α) is a characteristic peculiar to the TN type and the STN type, and is said to be caused by a pretilt generated between the surface subjected to the alignment treatment and the liquid crystal molecule, which makes the liquid crystal layer thin or the liquid crystal composition. This can be improved by reducing the Δn of the product. The rising response speed τ _R of the liquid crystal display element is

[Equation 4] (Where V is the applied voltage, η _i is the viscosity, and K _ii is the elastic constant). Therefore, the response speed can be increased by adding a compound having a small η _i / K _ii .

By the way, many liquid crystal compounds have been conventionally synthesized for improving these characteristics, but in reality, a compound satisfying each characteristic has not been obtained.

Therefore, an object of the present invention is to provide a liquid crystal compound or a liquid crystal analog compound which can further improve the above-mentioned various characteristics. Another object of the present invention is to provide a liquid crystal composition in which the above-mentioned various properties are improved by mixing the compound with another liquid crystal compound or a liquid crystal composition. Further, another object of the present invention is to improve the above-mentioned various characteristics by using the liquid crystal composition, and consequently to use a TN type or STN type of low voltage driving and high speed response and high time division driving.
Type liquid crystal display device.

[0009]

The present invention has the general formula

[Chemical 13] An ester compound represented by the formula (1), a liquid crystal composition containing the compound, and a liquid crystal display device using the liquid crystal composition.

The compounds of the present invention include the following three types of compounds. I.e.

[Chemical 14]

[Chemical 15]

[Chemical 16] (Here, R ¹ , R ² and R ³ have 1 to 1 carbon atoms.
An alkyl group of 0, Y is H or F, Z is F or CN, and A is a single bond or CH ₂ CH ₂ . The compound (A) has a large positive dielectric anisotropy, and the liquid crystal composition containing this compound can lower the threshold voltage of V-I ₀ characteristics. By using this liquid crystal composition, A low-voltage driven liquid crystal display device can be obtained. The compound (B) has a relatively large birefringence and can control the magnitude of birefringence of a conventional liquid crystal composition, so that a liquid crystal display device in which cell conditions are adjusted to optimum values can be obtained. The compound (C) has a relatively high clearing point and is about 140 ° C. when A is CH ₂ CH ₂ , and 170 to 180 when A is a single bond.
It is possible to increase the clearing point by mixing with another liquid crystal composition, and it is possible to reduce the viscosity of the liquid crystal composition because it has an effect and a small viscosity. Use of the liquid crystal composition containing this compound As a result, a liquid crystal display device having a high response can be obtained. Further, the compounds (A), (B), (C)
By using a liquid crystal composition in which one or more kinds of the above are appropriately mixed with a conventional liquid crystal compound or a liquid crystal composition, a driving voltage is low, and a TN type or ST capable of high-speed response and high time-division driving.
An N-type liquid crystal display device can be obtained.

Further, the ester compound of the present invention has good compatibility with other liquid crystal compounds and liquid crystal compositions, and the proportion to which this compound can be added is in the range of 1 to 50% by weight, and more preferably. Is in the range of 1 to 30% by weight, and it is effective to use each of the compounds (A), (B) and (C) as a single component or a plurality of components, but two or three types of single components or a plurality of components are used. The effect is greater when the components are used in combination, and the liquid crystal display device using the liquid crystal composition can be applied to a wider range of application fields.

The conventional liquid crystal compound or liquid crystal composition which can be mixed with the compound of the present invention is not limited, but for example, the following series of liquid crystal compounds or liquid crystal analogue compounds, and further liquid crystal compositions in which a plurality of series thereof are mixed are used. Mixing is possible.

[Chemical 17] Next, the ester compound of the present invention can be produced, for example, by the steps shown in Table 1. That is, in Step 1, 3-alkylfluorobenzene (E) is nitrated using a mixed solution to obtain 2-fluoro-4-alkylnitrobenzene (F). In step 2, compound (F) is catalytically reduced in ethanol using palladium-carbon as a catalyst to obtain 2-fluoro-4-alkylaniline (G). In step 3, compound (G) was diazotized with NaNO ₂ in hydrobromic acid and then Cu
Bromination with Br gives the 2-fluoro-4-alkylbromobenzene (H). In step 4, N-
Cyanation with CuCN in methyl-2-pyrrolidinone to give 2-fluoro-4-alkylbenzonitrile ((I). In step 5, compound (I) was hydrolyzed with dilute sulfuric acid to give 2- Fluoro-4-alkylbenzoic acid (J) is obtained, and in step 6, compound (J) is chlorinated with SOCl ₂ to give 2-fluoro-.
4-Alkylbenzoyl chloride (K) is obtained. In step 7, the substituted phenol (L) corresponding to the compound (K) is esterified with triethylamine in chloroform to obtain the ester compound (A) of the present invention.

[Table 1]

[0013]

EXAMPLES Hereinafter, the method for producing the ester compound of the present invention, the liquid crystal composition containing the compound and the liquid crystal display device using the liquid crystal composition will be described in more detail with reference to Examples. [Example 1] (Compound 1) 4- stirring dropwise concentrated sulfuric acid 160cm ³ at 10 ° C. below cyanophenyl 2'-fluoro-4'-producing method step 1 of concentrated nitric acid 160cm ³ of methyl benzoate in an ice-bath did. This solution was stirred on an ice bath with 3-alkylfluorobenzene 9
0 g was added dropwise at 5 to 10 ° C., and then the mixture was stirred on an ice bath for 1 hour and at room temperature for 1 hour. The reaction solution was poured into 500 g of ice, extracted with chloroform and washed with water. The residue was recrystallized from water-containing methanol to obtain 100 g of 2-fluoro-4-methylnitrobenzene.

Step 2 100 g of 2-fluoro-4-methylnitrobenzene was dissolved in 500 cm ³ of ethanol, 1.6 g of 5% palladium-carbon was added, and hydrogen gas was absorbed under vigorous stirring until the liquid temperature reached about 50 ° C. Rose. The reaction product was filtered to remove palladium-carbon, and ethanol in the filtrate was distilled off. The residual oily substance was distilled under reduced pressure (bp 71 ° C./10 mmHg) to obtain 73.5 g of 2-fluoro-4-methylaniline.

Step 3 48% hydrobromic acid 280 cm
³ to the solution diluted with water 280 cm ³ 2-fluoro-4
-Methylaniline 73.5 g was dissolved. A solution prepared by dissolving 42 g of NaNo _{2 in} 90 cm ³ of water was added to this solution at 5 ° C or lower on an ice bath. CuBr100 to 48% hydrobromic acid
The diazonium salt solution was added dropwise to the solution in which g was dissolved, with stirring, and then the mixture was stirred at room temperature overnight. The reaction solution was extracted with chloroform and washed with 48% hydrobromic acid and water. Chloroform was distilled off, and the remaining oily substance was distilled under reduced pressure (b.
p. 68 ° C./10 mmHg) to obtain 94 g of 2-fluoro-4-methylbromobenzene.

Step 4 70 g of 2-fluoro-4-methylbromobenzene and 40 g of CuCN were added to N-methyl-2.
-Hyrolidinone dissolved in 370 cm ³ and refluxed for 3 hours. The reaction solution was cooled to 60 ° C. and FeCl ₃ .6H ₂ O
A solution consisting of 200 g, concentrated hydrochloric acid 37 cm ³ and water 200 cm ³ was added and left at 60-70 ° C. for 1 hour. 200 cm ³ of water was added to the reaction product, extracted with a mixed solvent of hexane and chloroform, and washed with 10% hydrochloric acid and water. The solvent was distilled off, and the residue was distilled under reduced pressure (bp 130 ° C./47 mmH
g) and then 2-fluoro-4-methylbenzonitrile 40
g was obtained.

[0017] Concentrated sulfuric acid Step 5 2-fluoro-4-methylbenzonitrile 150 cm ³ and water 150 cm ³
And stirring for 3 hours. The produced crystal was filtered and washed with water to obtain 44 g of 2-fluoro-4-methylbenzoic acid.

Step 6 2-Fluoro-4-methylbenzoic acid (44 g), SOCl _{2 (} 45 cm ³⁾ and N, N-dimethylformamide (1 drop) were refluxed for 3 hours. Excess SOCl
₂ was distilled off, and the remaining oily substance was distilled under reduced pressure (bp.
8 ° C./28 mmHg) to obtain 47 g of 2-fluoro-4-methylbenzoic acid chloride.

Step 7 4 to 10 cm ³ of chloroform
-Cyanophenol 1.2g was melt | dissolved and triethylamine 3.0g was dripped. While stirring this solution on an ice bath, 2-fluoro-4-methylbenzoic acid chloride 1.
A solution obtained by dissolving 7 g of chloroform in 10 cm ³ was added dropwise. Then, it was left at room temperature overnight. The reaction solution was washed with water, 10% hydrochloric acid, water, 10% aqueous NaOH solution, and water in this order, and chloroform was distilled off. The residue was recrystallized from water-containing methanol to obtain 2.2 g of 4-cyanophenyl 2'-fluoro-4'methylbenzoate. The results of measuring the melting point of this compound using DSC were as follows.

M. p. The following compound was produced at a temperature of 116.4 ° C. or lower by the same production method.

3-fluoro-4-cyanophenyl 2 '
-Fluoro-4'-methylbenzoate m. p. 136.1 ° C. 3-chloro-4-cyanophenyl 2′-fluoro-
4'-methylbenzoate m. p. 143.5 ° C. 4-Fluorophenyl 2′-fluoro-4′-methylbenzoate m.p. p. 87.5 ° C. 3,4-difluorophenyl 2′-fluoro-4′-
Methyl benzoate m. p. 71.5 ° C. [Example 2] (Compound 2) 4- (methylthio) phenyl 2′-fluoro-4′-
Method for producing methyl benzoate.

1.4 g of 4- (methylthio) phenol was dissolved in 10 cm ³ of chloroform, and 3.0 g of triethylamine was added dropwise. 1.7 g of 2-fluoro-4-methylbenzoic acid chloride obtained in Example 1 was added dropwise to this solution while stirring on an ice bath, and the mixture was allowed to stand at room temperature overnight.
The reaction solution is water, 10% hydrochloric acid, water, 10% NaOH aqueous solution,
It was washed with water in this order, and chloroform was distilled off. The residue was recrystallized from methanol and 4- (methylthio) phenyl
2.2 g of 2'-fluoro-4'-methylbenzoate was obtained. The results of measuring the melting point of this compound using DSC were as follows.

M. p. 68.5 ° C. [Example 3] (Compound 3) A method for producing 4- (trans-4′-propylcyclohexyl) phenyl 2 ″ -fluoro-4 ″ -methylbenzoate.

In the same manner as in Example 1, 4- (trans-
2.2 g of 4'-propylcyclohexyl) phenol and 2-fluoro-4'-methylbenzoic acid chloride 1.
Using 7 g, 2.1 g of 4- (trans-4'-propylcyclohexyl) phenyl 2 "-fluoro-4" -methylbenzoate was obtained.

C-N 127.0 ° C. N-I 185.5 ° C. The following compounds were produced by the same production method.

4- (trans-4'-butylcyclohexyl) phenyl 2 "-fluoro-4" -methylbenzoate C-N 89.4 ° C. NI -176.2 ° C. 4- (trans-4'-benzyl cyclohexyl) ) Phenyl 2 ″ -fluoro-4 ″ -methylbenzoate C—N 90.4 ° C. N—I 180.1 ° C. 4- [2 ′-(trans-4 ″ -butylcyclohexyl) ethyl] phenyl

[Outer 1] C—S 51.5 ° C. S—N 77.4 ° C. N—I 139.7 ° C. [Example 4] (Liquid crystal composition) 90% by weight of a commercially available nematic liquid crystal composition ZLI-1565 (manufactured by Merck). 10% by weight of the compound of the present invention
Table 2 shows the nematic-isotropic liquid phase transition temperature (NI point), dielectric anisotropy (Δε) and birefringence (Δn) of the liquid crystal composition obtained by mixing.

[Table 2] [Example 5] (Liquid crystal display element) As shown in Fig. 1, transparent electrodes 3 made of ITO are formed on glass substrates 1 and 2, and an aligning agent made of polyimide is applied on the transparent electrodes 3 and rubbed with a face cloth. The orientation control layer 4
Formed. The glass substrates 1 and 2 are opposed to each other with an epoxy-based sealant 6 mixed with a gap agent,
The liquid crystal composition of the example was injected into the space between them to form a liquid crystal cell. The cell gap is 9 μm, and the twist angle is 90 degrees.
Table 3 shows the results of measuring the voltage-light transmittance characteristics at 0 ° C.
It was shown to.

[Table 3] Here, Vth is the voltage when the light transmittance is 10%, and the viewing angle dependence α and the steepness β are defined by the following equations, respectively. Note that φ is

[Equation 5] It represents the viewing angle and the front is 0 °.

In the above embodiment, the liquid crystal cell is T
Although an N-type cell was used, it was confirmed that the same effect could be obtained by using an STN-type cell.

[0028]

As described above, it was found that the compound (A) of the present invention has a large dielectric anisotropy, the compound (B) has a large birefringence, and the compound (C) has a high clearing point.
Further, it was confirmed that the driving voltage was low and high time division driving was possible by using the compound of the present invention. Therefore, the compound of the present invention and the liquid crystal composition obtained by mixing the compound of the present invention are very useful as a liquid crystal material for a TN-type or STN-type liquid crystal display device, and a liquid crystal display device using these liquid crystal materials is low. High time division driving can be performed with voltage.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a liquid crystal display element manufactured in an example of the present invention.

[Explanation of symbols]

 1, 2 glass substrate 3 transparent electrode 4 orientation control layer 5 polarizing plate 6 sealant

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C09K 19/42 6742-4H G02F 1/13 500 A 8806-2K

Claims (12)

[Claims] 1. A general formula: An ester compound represented by: 2. A general formula: A liquid crystal composition containing an ester compound, which comprises at least one ester compound represented by: 3. A general formula: A liquid crystal display device using a liquid crystal composition containing an ester compound, characterized by using a liquid crystal composition containing at least one kind of the ester compound represented by. 4. A general formula: (Here, R ¹ is an alkyl group having 1 to 10 carbon atoms,
Y represents H or F, and Z represents F or CN. ), The ester compound according to claim 1. 5. A general formula: (Here, R ¹ is an alkyl group having 1 to 10 carbon atoms,
Y represents H or F, Z represents F or CN. 3. A liquid crystal composition containing an ester compound according to claim 2, containing at least one kind of ester compound represented by the formula (1). 6. A general formula: (Here, R ¹ is an alkyl group having 1 to 10 carbon atoms,
Y represents H or F, and Z represents F or CN. 4. A liquid crystal display device containing an ester compound according to claim 3, wherein a liquid crystal composition containing at least one ester compound represented by the formula (4) is used. 7. A general formula: (Here, R ¹ and R ² each have 1 carbon atom
The alkyl groups of 10 are shown. ), The ester compound according to claim 1. 8. A general formula: (Here, each of R ¹ and R ² has a carbon atom number of 1 to
10 alkyl groups are shown. 3. A liquid crystal composition containing an ester compound according to claim 2, containing at least one kind of ester compound represented by the formula (1). 9. A general formula: (Here, each of R ¹ and R ² has a carbon atom number of 1 to
10 alkyl groups are shown. 4. A liquid crystal display device containing an ester compound according to claim 3, wherein a liquid crystal composition containing at least one ester compound represented by the formula (4) is used. 10. A general formula: (Here, R ¹ and R ³ each have 1 to 10 carbon atoms.
Alkyl group of 10, A represents a single bond or CH ₂ CH ₂ . ), The ester compound according to claim 1. 11. A general formula: (Here, R ¹ and R ³ each have 1 to 10 carbon atoms.
Alkyl group of 10, A represents a single bond or CH ₂ CH ₂ . 3. A liquid crystal composition containing an ester compound according to claim 2, containing at least one kind of ester compound represented by the formula (1). 12. A general formula: (Here, R ¹ and R ³ each have 1 to 10 carbon atoms.
Alkyl group of 10, A represents a single bond or CH ₂ CH ₂ . 4. A liquid crystal composition containing at least one ester compound represented by the formula 3) is used.
A liquid crystal display device containing the described ester compound.