JP2750914B2 - Novel fluorine-containing compound, liquid crystal composition containing the same, and optical switching element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention can take a stable thermotropic liquid crystal state, for example, for displays such as liquid crystal televisions, optical printer heads, optical Fourier transform elements, light valves, etc. The present invention relates to a novel fluorine-containing compound which can be used as a liquid crystal material useful as a material for an optoelectronics-related device utilizing liquid crystal or electrochemiomic, a liquid crystal composition containing the same, and an optical switching device.

[Conventional technology]

4- (4-n) synthesized by RBMeyer et al. In 1975
-Decyloxybenzylideneamino) cinnamic acid-2-methylbutyl ester (DOBAMBC) as a typical example, and a new display method proposed by NAClark et al. [Appl. Phys. 36, 899 (1980)] by a liquid crystal cell having a characteristic orientation does not change the liquid crystal molecules be cut high-speed response and the electric field of μsec order (memory characteristic) becomes possible. For this reason, many ferroelectric liquid crystal materials have been synthesized and proposed to date. In order to obtain this ferroelectric liquid crystal, it is necessary to introduce an optically active group into a compound that becomes a liquid crystal. As an asymmetric source of the optically active group, 2-octanol, 2-methylbutanol derivatives, etc. are exclusively used. Have been used.

By the way, recently, a ferroelectric liquid crystal using a fluorine-containing compound as an asymmetric source has been proposed. For example, [Jpn. J. Appl. Phys. 26 L77 (1987) and JP-A-63-3078]
No. 37] shows that the compound represented by the formula (6) at 5 ° C. below the phase transition point (T _AC ) of the smectic A phase → chiral smectic C phase:
It shows a spontaneous polarization of 0 nC / cm ² . Further, the same asymmetric source S-(−)-2-Fluoro-2-methylmalonic ac as in the present invention is used.
The following formula derived from id monoethyl ester [Jpn.J.Appl.Phys.26 L77 (1987) The compound represented by is a 5 ° C. under T _AC, shows the following spontaneous polarization 5 nC / cm ^2.

Although these two types of compounds both contain fluorine having a large dipole moment, they do not show particularly large values as compared with the previously reported compounds containing no fluorine. For example, Compounds represented by (WO 88/07518 Patent publication) is, T _AC
Shows a spontaneous polarization of 90 nC / cm ² at 5 ° C.

[Problems to be solved by the invention]

In view of the above situation, the present inventor has conducted intensive studies to reflect the electrical properties of fluorine in the physical properties of ferroelectric liquid crystals (particularly, an increase in spontaneous polarization). The chemical structure of the adjacent group has an important effect on the physical properties of the liquid crystal, and in particular, a group having a structure represented by the following formula, They have found that they greatly contribute to the physical properties of ferroelectric liquid crystals (especially, an increase in spontaneous polarization).

The present invention has been made based on such knowledge, and an object of the present invention is to provide a novel compound, a liquid crystal composition using the compound, and a light switching element which are useful as a display material or the like. is there.

[Means for Solving the Problems] The present invention provides a compound represented by the general formula (I): Wherein R ¹ and R ² each represent an alkyl group having 1 to 18 carbon atoms, and both alkyl groups may be the same or different, and A represents -O- or a single bond. , X is general formula _{(II) - (X 1)} p-B- (X 2) q- (II) ( wherein, p, q is denoted by 0, 1, or 2, B is a single bond, - COO -, - OCO -, - OCH 2 - or a divalent chain group selected from _{-CH 2 O-, X 1, X} 2 is And X represents a six-membered ring group represented by the formula: Wherein at least one of the above-mentioned general formula (I) is such that A is -O-
But, And a liquid crystal composition comprising the fluorine-containing compound represented by the general formula (I) or at least one of the fluorine-containing compounds represented by the general formula (I). And an optical switching element.

S-(-)-2-Fluoro-2-methylmaloni which is one of the raw materials necessary for synthesizing an adjacent group containing an asymmetric carbon and fluorine which is an intermediate of the compound of the above general formula (I)
c acid monoethyl ester has already been reported by Kitazume et al. using 2-Fluoro-2-methylmalonate as a raw material and asymmetric hydrolysis with Lipase-MY as an enzyme [J.
Org. Chem. 51, 1003 (1986)].
The higher the optical purity of the ester, the greater the spontaneous polarization is obtained. Desirably, the ester has an ee of 80% or more, but it may be lower.

Next, the core structure, that is, -X- of the above general formula (I)
As the structure of the group, Alternatively, the ester group shown below Can be exemplified.

Among the intermediates of this core structure, for example, H. Zaschke et al. [Z. Chem., 15 441 (1975) or J.
f. Prakt. Chem. 323 199 (1981)] and can be synthesized by the following scheme.

Also Can also be synthesized by the same means as in the above method.

On the other hand, among the intermediates in the core structure, the ester compound is Can be synthesized according to the following reaction scheme used for the synthesis of

The intermediate of the core structure thus obtained and the intermediate of the adjacent base containing asymmetric carbon and fluorine shown above are subjected to a usual esterification reaction, whereby the above-mentioned general formula (I) of the present invention is obtained. ) Can be synthesized.

 Specific compounds of the present invention are illustrated below.

Examples Example 1 4- (2- (4-hexyloxyphenyl) pyrimidinyl) phenyl ethyl-2-fluoro-2-methylmalonate (Synthesis method) 870 mg (2.5 mmol) of 2- (4-hexyloxyphenyl) -5- (4-hydroxyphenyl) pyrimidine synthesized by the method of H. Zaschke et al. And S-(−) obtained by the method of Kitazume et al. To 410 mg (2.5 mmol) of 2-fluoro-2-methylmalonic acid monoethyl ester, 510 mg of N, N'-dicyclohexylcarbodiimide (DCC) and 10 mg of dimethylaminopyridine were added, and the mixture was stirred in methylene chloride at room temperature for 2 hours. did. Further, under reflux of methylene chloride,
After stirring for an hour, insolubles were removed by filtration, and the filtrate was concentrated. The obtained concentrate was separated and purified by silica gel column chromatography using toluene / ethyl acetate = 10/1 as a developing solution to give 530 mg (1.1 mmol) of a compound having the following physicochemical properties. -(2- (4-Hexyloxyphenyl) pyrimidinyl) phenyl ethyl-2-fluoro-2-methylmalonate was obtained.

IR (KBr method, cm ^-1): (in _{CDCl 3, ppm) 1780,1760,1755,1600,1580,1430 NMR:} 8.95 (S, 2H), 8.40 (d, 2H) 7.65 (d, 2H), 7.25 (d, 2H), 7.00 (d, 2H) 4.40 (q, 2H), 4.05 (t, 2H), 1.95 (d, 3H) 1.90 to 1.30 (m, 11H), 0.93 (t, 3H) (Physical properties Evaluation) The phase transition behavior was measured by controlling the temperature of the above compound using a hot stage and observing the compound using a crossed Nicol microscope. The temperature was raised and lowered at a rate of 2 ° C. per minute. In the cooling process, the liquid changed from an isotropic liquid to a chiral smectic C phase at 101 ° C., and crystallized at 94 ° C. During the heating process, the crystals melted at 114 ° C and became an isotropic liquid.

The polyimide was applied, and the compound was injected into a 3 μm-thick cell made of glass with a transparent electrode that had been subjected to a rubbing treatment. When the magnitude of spontaneous polarization was measured by a triangular wave method, it was as large as 189 mC / cm ² at 97 ° C. The value was shown.

Example 2 4- (2- (4-butyloxyphenyl) pyrimidinyl) phenyl ethyl-2-fluoro-2-methylmalonic acid ester 2- (4-butyloxyphenyl) in the same manner as described in Example 1. -5- (4-hydroxyphenyl)
By condensing pyrimidine and S-(-)-2-fluoro-2-methylmalonic acid monoethyl ester, 4- (2- (4-butyloxyphenyl) pyrimidinyl) phenyl ethyl having the following physicochemical properties: 2
-Fluoro-2-methylmalonic acid ester was obtained.

IR (KBr method, cm ^-1): (in _{CDCl 3, ppm) 1780,1760,1755,1600,1580,1430 NMR:} 8.95 (S, 2H), 8.40 (d, 2H) 7.65 (d, 2H), 7.25 (d, 2H), 7.00 (d, 2H) 4.40 (q, 2H), 4.05 (t, 2H), 1.95 (d, 3H) 1.90 to 1.30 (m, 7H), 0.93 (t, 3H) The phase transition temperature was measured by the same method as in Example 1. As a result, the liquid crystallized from the liquid at 125.7 ° C. in the temperature decreasing process. In addition, during the temperature rise process, the crystal became an isotropic liquid at 137 ° C.

Reference Example 1 4- (4-octyloxybiphenyl-4'-carbonyloxy) phenyl ethyl 2-fluoro-2-methylmalonate (Synthesis method) A commercially available 4'-hydroxybiphenyl-4'-carboxylic acid is reacted with octyl bromide under alkaline conditions to obtain 4-octyloxybiphenyl-4'-carboxylic acid, which is treated with thionyl chloride to obtain an acid. After being converted to chloride, it was reacted with hydroquinone to obtain 4-hydroxyphenyl 4-octyloxybiphenyl-4'-carboxylate.

This compound was esterified by a method similar to that of obtaining monoethyl S-(-)-2-fluoro-2-methylmalonate of Example 1 to give 4- (having the following physicochemical properties: 4-octyloxybiphenyl-4'-carbonyloxyl) phenyl ethyl 2-fluoro-2
-Methylmalonic acid ester was obtained.

IR (KBr method, cm ^-1): (in _{CDCl 3, ppm) 1780,1765,1730,1600,1500 NMR:} 8.22 (d, 2H), 7.64 (m, 4H) 7.35~6.95 (m, 6H), 4.40 (q, 2H), 4.01 (t, 2
H), 1.95 (d, 3H), 1.90 to 1.30 (m, 15H), 0.93 (t, 3H) (Evaluation of physical properties) The phase transition temperature was measured in the same manner as in Example 1, At 147.5.degree. C., from a liquid to a smectic A phase, at 96.1.degree. C. to a chiral smectic C phase, and crystallized at 70.0.degree. In addition, 10
At 6.5 ° C, the solid changed to a smectic A phase.

The spontaneous polarization is 20.3 nC / cm at 91.1 and 52.3 nC / cm at 76.1 ° C.
It was cm ^2.

Example 3 4- (5-nonylpyrimidyl) phenyl ethyl-2-
Fluoro-2-methylmalonate 4-hydroxybenzamine hydrochloride and α-nonyl-β
-Dimethylaminoacrolein as raw material, H. Zaschk
According to the method of e et al. [Z. Chem. 15 441 (1975)], 5-nonyl-2- (4-hydroxyphenyl) pyrimidine was obtained. The pyrimidine compound thus obtained was converted to S-(-)
-2-fluoro-2-methylmalonic acid monoethyl ester was synthesized in the same manner as described in Example 1,
4- (5-Nonylpyrimidyl) phenyl ethyl-2-fluoro-2-methylmalonic acid ester having the following physicochemical properties was obtained.

IR (KBr method, cm ^-1): (in _{CDCl 3, ppm) 1790,1765,1750,1585,1545,1430 NMR:} 8.60 (s, 2H), 8.40 (d, 2H), 7.00
(D, 2H), 4.40 (q, 2H), 2.65 (t, 2H), 1.95 (d, 3H), 1.
90-1.30 (m, 17H), 0.95 (t, 3H) Example 4 4- (4-hexyloxyphenyl-4'-carbonyloxy) phenyl ethyl-2-fluoro-2-methylmalonate 4-Hydroxyphenyl 4- obtained by reacting commercially available 4-hexyloxybenzoic acid chloride with hydroquinone
Hexyloxybenzoate and S-(-)-2-fluoro-2-methylmalonic acid monoethyl ester were synthesized in the same manner as described in Example 1, and had the following physicochemical properties: (4-hexyloxyphenyl-
4'-carbonyloxyl) phenyl ethyl-2-fluoro-2-methylmalonate was obtained.

IR (KBr method, cm ^-1 ): 1780,1763,1740,1725,1680,1610,1
(In _{CDCl 3, ppm) 500 NMR:} 8.15 (d, 2H), 7.40~6.95 (m, 6
H), 4.40 (q, 2H), 4.01 (t, 2H), 1.95 (d, 3H), 1.90-
1.30 (m, 10H), 0.95 (t, 3H) Example 5 Preparation of Liquid Crystal Composition and Optical Switching Element On the other hand, a cholesteric phase was formed at 67 to 62 ° C, a smectic A phase was formed at 62 to 47 ° C, and 47 to 7 ° C. The base liquid crystal mixed with a non-chiral phenylpyrimidine-based compound having a smectic C phase in the above, and the 4- (2- (4-hexyloxyphenyl) pyrimidinyl) phenyl ethyl- obtained in Example 1
When 2-fluoro-2-methylmalonate was mixed at a weight ratio of 9: 1, the cholesteric phase was changed from 67.5 to 65.5 ° C at 65.5 to 50.6 ° C, and the smectic A phase was changed from 50.6 to 6.5 ° C.
As a result, a good ferroelectric liquid crystal composition having a chiral smectic C phase was obtained.

The liquid crystal composition thus obtained is coated with polyimide, injected into a 2.1 μm-thick cell made of rubbed glass with a transparent electrode, and the temperature of the isotropic liquid is gradually lowered, which is good. After obtaining the oriented chiral smectic C phase, an optical switching operation was observed when an electric field was applied to the cell while observing the cell with a crossed Nicol polarizing microscope.

The response time of this cell at 25 ° C. was 61.6 μsec.

Thus, the optically active groups of the compounds of the invention are similar,
It shows that spontaneous polarization is larger than that of other conventionally known fluorine-based compounds, and that a good liquid crystal composition can be formed particularly when added to a pyrimidine-based mixture.

4. Effects of the Invention As described above, the novel compound of the present invention and the liquid crystal composition containing the same, and further the switching element, reflect the electronic effect of fluorine atoms, respond quickly to an electric field, It is extremely useful as a display material for optoelectronics.

Claims (4)

(57) [Claims] 1. The compound of the general formula (I) Wherein R ¹ and R ² each represent an alkyl group having 1 to 18 carbon atoms, and both alkyl groups may be the same or different, and A represents a single bond or -O- , X is general formula _{(II) - (X 1)} p-B- (X 2) q- (II) ( wherein, p, q is denoted by 0, 1, or 2, B is a single bond, - COO -, - OCO -, - OCH 2 - or a divalent chain group selected from _{-CH 2 O-, X 1, X} 2 is And X represents a six-membered ring group represented by the formula: A fluorine-containing compound represented by the formula: 2. In the general formula (I) of claim (1),
Is -O-, and X is The novel fluorine-containing compound according to claim 1, wherein the compound is represented by the following formula: 3. A liquid crystal composition comprising the fluorine-containing compound represented by the general formula (I) according to claim 1. 4. An optical switching element comprising at least one fluorine-containing compound represented by the general formula (I) according to claim 1 as a constituent element.