JPH07291941A - Optically active fluorine compound, ferroelectric liquid crystal compound and liquid crystal composition - Google Patents

Abstract

PURPOSE:To obtain the novel low-viscosity composition having high spontaneous polarization, and capable of raising the phase transition temperature Tc of the liquid crystal composition therefrom. CONSTITUTION:The optically active 2,3-difluoroalkyloxy compound of the formula I (R<1> is a 3-13C alkyl or an alkoxyl; R<2> is a 1-10C straight chain alkyl; cyclic groups A, B and C each is 1,4-phenylene or 2,5-pyrimidin-diyl of the formula II or III; where, at least one of them being 2,5-pyrimidin-diyl group), e.g. 2-[4'-{(2 R,3R)-2,3-difluorohexyloxy}-4-biphenyl]-5-octylpyrimidine. The compound of the formula I is obtained, for example, by using a tricyclic hydroxy compound of the formula IV as starting material and according to the reaction formula such as conducting, e.g. Mitsunobu reaction of a (2S,3S)-2,3-epoxyalkyl alcohol of the formula V.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to novel optically active compounds 2, 3
-Difluoroalkyloxy compounds and their uses. More specifically, it relates to a ferroelectric tricyclic optically active 2,3-difluoroalkyloxy liquid crystal compound containing a pyrimidine ring, and a liquid crystal composition using the liquid crystal compound.

[0002]

2. Description of the Related Art At present, a TN (twisted nematic) type display system is most widely used as a liquid crystal display device. The TN liquid crystal display has many advantages such as low driving voltage and low power consumption. However, in terms of response speed, it is inferior to light emitting display devices such as cathode ray tubes, electroluminescence, and plasma displays. Although a new TN type display device having a twist angle of 180 to 270 ° has been developed, the response speed is still inferior. As described above, various efforts have been made, but a TN type display element having a high response speed has not been realized yet.

However, in a new display method using a ferroelectric liquid crystal, which is under study, there is a possibility of significantly improving the response speed (Clark et al., Applied Phy).
s. Lett., 36, 899 (1980)). This method is a method utilizing a chiral smectic phase such as a chiral smectic C phase (hereinafter abbreviated as SC ^* phase) exhibiting ferroelectricity.

Although many properties are required for the ferroelectric liquid crystal material used in the ferroelectric liquid crystal display device actually used, at present, these properties cannot be satisfied by one compound. First, it is necessary to use a ferroelectric liquid crystal composition obtained by mixing some liquid crystal compounds or non-liquid crystal compounds.

Further, not only a ferroelectric liquid crystal composition consisting of only a ferroelectric liquid crystal compound, but also a compound or composition exhibiting an achiral smectic C, F, G, H, I phase, etc. It has been reported that one or a plurality of compounds exhibiting a ferroelectric liquid crystal phase can be mixed with each other to form a ferroelectric liquid crystal composition as a whole (JP-A-61-19518).
(Gazette No. 7). Furthermore, a compound or composition that exhibits a phase such as SC is used as a basic substance, and one or more compounds that are optically active but do not exhibit a ferroelectric liquid crystal phase are mixed to make a whole ferroelectric liquid crystal composition. There is also (Clark et al.,
Mol, Cryst. Liq. Cryst., 89, 327 (1982)).

From these facts, it is understood that one or more optically active compounds can be mixed with a basic substance to form a ferroelectric liquid crystal composition.

The storage temperature range of the liquid crystal material required for practical use is about −30 to 85 ° C.
Most of the ferroelectric liquid crystal materials reported to date are S
Since the temperature range of the C ^* phase is about 60 to -10 ° C, development of a material showing the SC ^* phase in a wider temperature range is required in order to prevent orientation change due to phase transition and to obtain storage stability. There is.

As a base liquid crystal suitable for practical use, a liquid crystal mixture having an SC phase in a wide temperature range including room temperature is particularly desired. As the component of the base liquid crystal, some of liquid crystal compounds such as phenylbenzoate type, Schiff base type, biphenyl type, phenyl-pyrimidine type and phenyl-pyridine type liquid crystal are used, and exhibit a ferroelectric liquid crystal phase. One or more chiral compounds are added.

However, the addition of the ferroelectric chiral compound usually increases the viscosity and narrows the temperature range of the smectic C (SC) phase of the host liquid crystal.

As a chiral compound having spontaneous polarization and low viscosity, the following formula (II)

[Chemical 5] Attention has been paid to compounds represented by (US Pat. No. 5,051,
No. 506, Ferroelectrics, 1991, Vol121, pp213-218
).

Those with a high spontaneous polarization often have a short helical pitch. In a display system using a ferroelectric liquid crystal, it is necessary to have two stable states (bistable states) on the electrode surface. In order to obtain a liquid crystal display device with this bistable state and high-speed response, it is necessary to make the cell gap d smaller than the helical pitch p (d <p) and unwind the helix as suggested by Clark et al. (Mol. C
ryst. Liq. Cryst., 89, 327 (1982)). Also, in order to improve the alignment of the liquid crystal, cholesteric (Ch)
It is necessary to lengthen the helical pitch of the phase and the chiral smectic C (SC ^* ) phase. Therefore, it is necessary to add a pitch adjusting agent for extending the pitch to a dopant having a short pitch.

However, the addition of various compounds to the host liquid crystal lowers the transition temperature (Tc point) of the smectic C (SC) phase → smectic A (SA) phase or the like below the practical temperature range. For this reason, a tricyclic phenylpyrimidine compound (Japanese Patent Laid-Open No. 2-232292) or the like has been added as a compound for further increasing the Tc point (high temperature agent). However, the addition of various compounds, chiral dopants, pitch adjusters, high temperature agents, etc. to the base crystal will further increase the viscosity. For this reason, a viscosity reducing agent that further lowers the viscosity is added (Japanese Patent Laid-Open No. 2-279786), but the composition becomes more complicated.

Therefore, the object of the present invention is to have a high spontaneous polarization, a low viscosity, and a phase transition temperature Tc of a liquid crystal composition.
It is to provide a novel dopant for liquid crystal capable of increasing the point.

[0014]

DISCLOSURE OF THE INVENTION As a result of intensive studies, the present inventors have found that a specific tricyclic optically active 2,3-difluoroalkyloxy compound having at least one 2,5-pyrimidinediyl group. Has a high spontaneous polarization (that is, it has ferroelectricity), has a low viscosity, and has an effect of not only lowering the Tc point when added (used) to a liquid crystal composition, but also having an effect of increasing it, and further has a low viscosity. It was confirmed that the compound has excellent compatibility with a known phenylpyrimidi-based base liquid crystal, which is known to be extremely useful, and completed the present invention.

That is, the present invention includes 1) the general formula (I)

[Chemical 6] (In the formula, R ¹ is a linear or branched chain having 3 to 13 carbon atoms,
It is an alkyl or alkoxy group, and R ² has 1 to 1 carbon atoms.
10 linear alkyl groups, the three cyclic groups A, B and C may be the same or different, and each is a 1,4-phenylene group, or

[Chemical 7] Is a 2,5-pyrimidinediyl group represented by. However, at least one of the cyclic groups A, B and C is a 2,5-pyrimidinediyl group. ), An optically active 2,3-difluoroalkyloxy compound represented by the formula (2), and 2) the general formula (I)

[Chemical 8] (Wherein R ¹ , R ² , A, B and C have the same meanings as described in 1 above), and 3) the ferroelectric liquid crystal compound described in 2 above is phenyl. Provided is a liquid crystal composition characterized by being blended with a pyrimidine-based base liquid crystal.

In the general formula (I), the alkyl group having 3 to 13 carbon atoms represented by R ¹ is n-propyl,
Examples thereof include n-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and tridecyl groups. Examples of the alkoxy group having 3 to 13 carbon atoms represented by R ¹ include n-propyloxy, n-butyloxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy. Groups. Examples of the linear alkyl group having 1 to 10 carbon atoms represented by R ² include methyl, ethyl, n-propyl and n-
Examples include butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl groups.

Further, among the compounds represented by the general formula (I), particularly the following general formula (IA) or (IB)

[Chemical 9] (In the formula, R ¹¹ is a linear alkyl or alkoxy group having 7 to 10 carbon atoms, R ²¹ is a linear alkyl group having 1 to 5 carbon atoms, and the configuration at the 2-position and 3-position is (2R, 3R) or (2S, 3S)) is preferred.

Specific examples of the compound represented by the general formula (I) include 1) 2- [4 '-{(2R, 3R) -2,3-difluorohexyloxy} -4-biphenyl] -5-octyl. Pyrimidine, 2) 2- [4 '-{(2S, 3S) -2,3-difluorohexyloxy} -4-biphenyl] -5-octylpyrimidine, 3) 2- [4'-{(2R, 3R) -2,3-Difluorohexyloxy} -4-biphenyl] -5-nonylpyrimidine, 4) 2- [4 '-{(2R, 3R) -2,3-difluorohexyloxy} -4-biphenyl] -5 -Decylpyrimidine, 5) 2- [4 '-{(2R, 3R) -2,3-difluoroheptyloxy} -4-biphenyl] -5-octylpyrimidine, 6) 2- [4'-{(2S, 3S) -2,3-diful Roheptyloxy} -4-biphenyl] -5-octylpyrimidine, 7) 2- [4 '-{(2R, 3R) -2,3-difluorooctyloxy} -4-biphenyl] -5-octylpyrimidine, 8 ) 2- [4 '-{(2R, 3R) -2,3-difluorohexyloxy} -4-biphenyl] -5-octyloxypyrimidine,

9) 2- (4-octylphenyl) -5-
[4-{(2R, 3R) -2,3-difluorohexyloxy} phenyl] pyrimidine, 10) 2- (4-octylphenyl) -5- [4-
{(2S, 3S) -2,3-Difluorohexyloxy} phenyl] pyrimidine, 11) 2- (4-heptylphenyl) -5- [4-
{(2R, 3R) -2,3-Difluorohexyloxy} phenyl] pyrimidine, 12) 2- (4-hexylphenyl) -5- [4-
{(2R, 3R) -2,3-Difluorohexyloxy} phenyl] pyrimidine, 13) 2- (4-octylphenyl) -5- [4-
{(2R, 3R) -2,3-difluorononyloxy}
Phenyl] pyrimidine, 14) 2- (4-octylphenyl) -5- [4-
{(2R, 3R) -2,3-difluorodecyloxy}
Phenyl] pyrimidine, 15) 2- (4-octyloxyphenyl) -5- [4
-{(2R, 3R) -2,3-difluorohexyloxy} phenyl] pyrimidine, 16) 2- [4-{(2R, 3R) -2,3-difluorohexyloxy} phenyl] -5- (4- Octylphenyl) pyrimidine, 17) 2- [4-{(2R, 3R) -2,3-difluorohexyloxy} phenyl] -5- (4-octyloxyphenyl) pyrimidine,

18) 2- (4'-octyl-4-biphenyl) -5-{(2R, 3R) -2,3-difluorohexyloxy} pyrimidine, 19) 2- (4'-octyl-4-biphenyl) ) -5
{(2S, 3S) -2,3-Difluorohexyloxy} pyrimidine, 20) 2- (4'-octyloxy-4-biphenyl)
-5-{(2R, 3R) -2,3-difluorohexyloxy} pyrimidine, 21) 2- (4'-heptyl-4-biphenyl) -5-
{(2R, 3R) -2,3-difluorohexyloxy} pyrimidine, and 22) 2- (4'-hexyl-4-biphenyl) -5-
{(2S, 3S) -2,3-difluorooctyloxy} pyrimidine.

Of these, particularly preferred are: 2- (4-octylphenyl) -5- [4-{(2
R, 3R) -2,3-difluorohexyloxy} phenyl] pyrimidine and 2- [4 '-{(2R, 3R) -2,3-difluorohexyloxy} -4-biphenyl] -5-octylpyrimidine is there.

[0022]

Production Method The compound of the present invention represented by the above general formula (I) can be produced according to the following reaction scheme known per se.

[0023]

[Chemical 10] (All symbols in the formula have the same meanings as described above.)

The starting materials and respective reagents in the present invention are known per se or can be produced by known methods. Briefly explaining the reaction process formula,
The tricyclic hydroxy compound represented by the general formula (III) is
It can be produced by condensation of α-alkyl-β-dimethylaminoacrolein and an amidine compound.

[Chemical 11]

The compound of the general formula (III) can also be produced by condensation of a trimethine salt and an amidine compound (D. Demus, S. Diele, M. Klapperstruck, V.Link.
and H. Zaschke, Mol. Cryst. Liq. Cryst., 15 , 161 (19
71)).

[Chemical 12]

(2S, 3S) -2,3-of the general formula (IV)
Epoxyalkyl alcohols can be obtained by Sharpless oxidation of allyl alcohol (T.Katsuki and KBSharpless, J. Am. Chem. Soc.,
102, 5976 (1980)). Further, it can be obtained from a reagent company such as Aldrich as a reagent.

The reaction for producing the compound represented by the general formula (V) from the compound represented by the general formula (III) and the compound represented by the general formula (IV) is known as Mitsunobu reaction. That is, the compounds of the general formulas (IV) and (III) and triphenylphosphine are combined with dioxane, ethylene glycol dimethyl ether, tetrahydrofuran (TH
The solution obtained by dissolving F) or the like in a solvent is stirred, diethyl azodicarboxylate is added thereto little by little at a temperature of 0 to 30 ° C., and the mixture is allowed to stand for 2 to 10 hours, and the solvent is distilled off under reduced pressure. The obtained crystals are purified by a recrystallization method or the like.

From the compound of the general formula (V) (2S, 3R)
-2-Hydroxy-3-fluoroalkyl compound (VI)
The conversion to the compound is carried out by cooling the liquid obtained by dissolving the epoxy compound of the general formula (V) in an inert solvent such as benzene or methylene chloride, adding hydrofluoric acid-pyridine to the reaction, and distilling the solvent. It is removed and recrystallized from a suitable solvent (methylene chloride-hexane etc.).

From the 2-hydroxy-3-fluoroalkyl compound of general formula (VI) to (2R, 3R) of general formula (I)
The conversion to a 2,3-difluoroalkyloxy compound is performed by converting the hydroxy compound of the general formula (VI) into chloroform,
A solution dissolved in an inert solvent such as methylene chloride is -78 to
It was cooled to −20 ° C., and (C ₂ H ₅ ) ₂ NSF ₃ (diethylaminosulfur trifluoride; DAST) was added.
Is reacted by adding a solution of dichloromethane dissolved in dichloromethane to the reaction solution, washing the reaction solution with water, separating the target compound by column chromatography after distilling off the solvent, and recrystallizing from the solvent for purification. Be done.

The optically active 2,3-difluoroalkyloxy compound of the present invention has a high spontaneous polarization, has a low viscosity, and has an effect of increasing the Tc point without lowering it when added (used) to a liquid crystal composition, It has excellent compatibility with the low-viscosity phenylpyrimidine-based liquid crystal and can broaden the temperature range of the liquid crystal phase. Known low-viscosity phenylpyrimidine-based liquid crystals include, for example, 2- (4-hexyloxyphenyl) -5-heptylpyrimidine, 2- (4-nonyloxyphenyl) -5-heptylpyrimidine, 2- ( 4-hexyloxyphenyl) -5-nonylpyrimidine, 2- (4-nonyloxyphenyl) -5-nonylpyrimidine, 2- (4'-octyloxy-4-biphenyl) -5
-Octylpyrimidine and the like.

[0031]

The present invention will be described below with reference to examples.
The present invention is not limited to these. In the examples, the phase transition temperature was determined by observing the texture with a scanning differential calorimeter (DSC) and a polarizing microscope. Further, I is an isotropic phase, N is a nematic phase, Ch is a cholesteric phase, SA is a smectic A phase, SC ^* is a chiral smectic C phase, and Cr is a crystal.

Example 1: 2- (4-octylphenyl)
Synthesis of -5- [4-{(2R, 3R) -2,3-difluorohexyloxy} phenyl] pyrimidine (A)

[Chemical 13]

(1) 2- (4-octylphenyl) -5
Synthesis of-[4-{(2S, 3S) -2,3-epoxyhexyloxy} phenyl] pyrimidine

[Chemical 14]

2- (4-octylphenyl) -5- (4
-Hydroxyphenyl) pyrimidine 1 g, (2S, 3
S) -2,3-epoxyhexanol 0.45 g and triphenylphosphine 1.1 g tetrahydrofuran 20 ml
Dissolved in. Add diethyl azodicarboxylate 0.75 to this solution.
g was added little by little while stirring at room temperature. After standing overnight, the solvent was distilled off under reduced pressure and recrystallized twice with methanol to obtain about 1.0 g of the above compound.

(2) 2- (4-octylphenyl) -5
Synthesis of-[4-{(2S, 3R) -2-hydroxy-3-fluorohexyloxy} phenyl] pyrimidine

[Chemical 15]

Eposhikid 1.0 produced in Example 1 (1)
g was dissolved in 7 ml of dichloromethane and hydrogen fluoride was added under ice cooling.
2.6 ml of pyridine was added. After 30 minutes, return to room temperature and let stand overnight. Wash the reaction solution with aqueous sodium hydrogen carbonate solution,
The solvent was distilled off. The product was recrystallized from methylene chloride-hexane to obtain 0.85 g of the above compound.

(3) 2- (4-octylphenyl) -5
Synthesis of-[4-{(2R, 3R) -2,3-difluorohexyloxy} phenyl] pyrimidine

[Chemical 16]

0.56 g of the fluorohydroxy compound prepared in Example 1 (2) was dissolved in dichloromethane and cooled with a dry ice-methanol refrigerant. A solution prepared by diluting 0.2 ml of DAST with dichloromethane is gradually added dropwise. After 30 minutes from the completion of the dropping, the temperature is returned to room temperature, and after standing overnight, the reaction solution is washed with water,
After distilling off the solvent, the desired product was separated and purified by a silica gel column. Difluoro compound after recrystallization with methanol
0.15 g was obtained.

¹ H-NMR: δ 0.89 (3H, t), 1.00 (3H,
t), 1.2 to 1.4 (12H), 1.4 to 2.0 (4H, m), 2.68 (2H, t), 4.
26 (1H, t), 4.35 (1H, d), 4.6 ~ 5.0 (2H, m), 7.07 (2H, d),
7.31 (2H, d), 7.56 (2H, d), 8.36 (2H, d), 8.96 (2H, s).

Embedded image Phase transition temperature I → 194 ° C. → SA → 148 ° C. → SC ^* → 121 ° C. → C
r

Example 2: 2- [4 '-{(2R, 3R)
Synthesis of -2,3-difluorohexyloxy} -4-biphenyl] -5-octylpyrimidine (B)

[Chemical 18]

2- (4'-hydroxy-4-biphenyl) -5-octylpyrimidine was used as a starting material and the title compound (B) was synthesized by the same procedure as in Example 1 according to the following steps.

[0042]

[Chemical 19]

¹ H-NMR: δ 0.89 (3H, t), 1.01 (3H,
t), 1.2 to 1.4 (12H), 1.4 to 2.0 (4H, m), 2.64 (2H, t), 4.
25 (1H, t), 4.33 (1H, d), 4.6 ~ 5.0 (2H, m), 7.01 (2H, d),
7.61 (2H, d), 7.67 (2H, d), 8.47 (2H, d), 8.61 (2H, s).

Embedded image Phase transition temperature I → 168 ° C. → N → 161 ° C. → Ch → 143 ° C. → SC ^*
→ 105 ° C → Cr

Example 3 A base liquid crystal composition (X) was prepared by mixing the following various phenylpyrimidine compounds.

[Table 1]

To 93% by weight of this liquid crystal composition (X), 7% by weight of each of the compound (A) prepared in Example 1 and the compound (B) prepared in Example 2 was mixed and the phase transition temperature was measured. did. As a comparative example, the following formula

[0046]

[Chemical 21]

The bicyclic compound (C) represented by
The phase transition temperature was also measured for the composition mixed by weight. The results are shown in Table 2.

[0048]

[Table 2] Table 2 Liquid crystal composition Phase transition temperature (° C) IN SA Ch Cr X 76 72.5 57 RT> X + A 84 81 62 RT> X + B 81 74 61 RT> X + C 74 69 56 RT>

It can be seen from Table 2 that the compound of the present invention has an effect of increasing the phase transition temperature of the liquid crystal composition.

Example 4 A mixture of 93% by weight of the base liquid crystal (X) and 7% by weight of the compound (A) shown in Example 3 was heated to make an isotropic liquid, and then polyimide was applied thereto and subjected to rubbing treatment. It was poured into a thin cell with a transparent electrode (2.4 μ), and the cell was gradually cooled.
A triangular wave voltage of 48 Vpp and 50 Hz was applied to this cell to measure spontaneous polarization at 25 ° C. 24V in the same cell
The response speed at 25 ° C. was measured by applying a rectangular wave voltage of pp, 50 Hz. Base liquid crystal (X) by the same method
The measurement was also performed on a mixture of 93% by weight and 7% by weight of the compound (B). The measurement results are shown in Table 3.

[0051]

[Table 3]

[0052]

INDUSTRIAL APPLICABILITY The compound of the present invention is an optically active tricyclic difluoroalkyloxy compound having a high spontaneous polarization and a low viscosity, having at least one phenylpyrimidine ring, and having a phase with a phenylpyrimidis base liquid crystal. It is excellent in solubility and can raise the phase transition temperature Tc point of the base liquid crystal composition.

Claims (4)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R ¹ is a linear or branched chain having 3 to 13 carbon atoms,
It is an alkyl or alkoxy group, and R ² has 1 to 1 carbon atoms.
10 linear alkyl groups, the three cyclic groups A, B and C may be the same or different and each is a 1,4-phenylene group, or Represents a 2,5-pyrimidinediyl group represented by. However, at least one of the cyclic groups A, B and C is a 2,5-pyrimidinediyl group. ) An optically active 2,3-difluoroalkyloxy compound represented by 2. A compound represented by the general formula (I): (Wherein R ¹ , R ² , A, B and C have the same meanings as described in claim 1). 3. A liquid crystal composition comprising the phenylpyrimidine-based base liquid crystal compounded with the ferroelectric liquid crystal compound according to claim 2. 4. A compound represented by the general formula (IA) or (IB): (In the formula, R ¹¹ is a linear alkyl or alkoxy group having 7 to 10 carbon atoms, R ²¹ is a linear alkyl group having 1 to 5 carbon atoms, and the configuration at the 2-position and the 3-position is (2R, 3R) or (2S, 3S).) The ferroelectric liquid crystal compound according to claim 2.