JPH0694439B2 - Optically active liquid crystalline compound, liquid crystal composition containing the same, and liquid crystal device using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel liquid crystal compound, a liquid crystal composition containing the same, and a liquid crystal device using the liquid crystal composition.

BACKGROUND ART Conventional liquid crystal elements include, for example, M.Scatter (M.Sc
hadt) and W. Helfrich, "Abride Fijix Redders", Vol. 18, Vol.
Issue ("Applied Physics Letters") (published on February 15, 1971), p127-128, "Voltage Dependent Optical Activity of" Twisted Nematic Liquid Crystal "
a Twisted Nematic Liiquid Crystal ")
(Twisted nematic) A liquid crystal is known. However, this TN liquid crystal has a problem in that cross-talk occurs during time-division driving using a matrix electrode structure having a high pixel density, and thus the number of pixels is limited. Further, since the electric field response is slow and the viewing angle characteristic is poor, the use as a display is limited.

Further, there is known a display element of a system in which a switching element formed of a thin film transistor is connected to each pixel, and each pixel is switched.However, the step of forming the thin film transistor on the substrate is extremely complicated, and a large area display element is used. There are problems that are difficult to create.

The use of bistability-type liquid crystal elements is known as Clark (Cl
ark) and Lagerwall (JP-A-56-107216, US Pat. No. 4,367,924, etc.). As a liquid crystal having bistability, a chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) is generally used.
A ferroelectric liquid crystal having is used.

This ferroelectric liquid crystal has a very fast response speed due to its spontaneous polarization, and can express a bistable state with a memory property. Moreover, it has a large viewing angle characteristic and thus has a large capacity and a large capacity. Suitable as a screen display.

Since the material used as the ferroelectric liquid crystal has asymmetric carbon, it is used not only as the ferroelectric liquid crystal utilizing its chiral smectic phase but also as the following optical element. be able to.

1) Utilizing the cholesteric / nematic phase transition effect in the liquid crystal state (JJWysoki, A. Adams and WH
aas; Phys.Rev.Lett., 20,1024 (1968)), 2) Utilizing the white Taylor type guest-host effect in the liquid crystal state (DLWhite and GNTaylor;
J.Appl.Phys., 45 , 4718 (1974)) and the like are known.

Although detailed description of each method is omitted, it is important as a display element or a modulation element.

In such a method using the electric field response optical effect of liquid crystal, it is said that it is preferable to introduce a polar group in order to enhance the response of the liquid crystal. Especially in ferroelectric liquid crystals, it is known that the response speed is proportional to the spontaneous polarization,
It is desired to increase the spontaneous polarization for speeding up. From such a point, P. Keller et al. Showed that by introducing a chlorine group directly into the asymmetric carbon, the spontaneous polarization can be increased and the response speed can be increased (CRAcad.Sc.Paris,
282 C.639 (1976)). However, the chlorine group introduced into the asymmetric carbon is chemically unstable and has a drawback that the stability of the liquid crystal phase is deteriorated due to its large atomic radius, and improvement thereof is desired. There is.

On the other hand, a functional material required for an optical element characterized by having optical activity is often synthesized through an optically active intermediate itself, but as an optically active intermediate used conventionally, 2 -Methyl butanol, secondary octyl alcohol, secondary butyl alcohol, p- (2-methylbutyl) benzoic acid chloride, secondary phenethyl alcohol, amino acid derivatives, camphor derivatives, cholesterol derivatives, etc. Almost no polar group was introduced into the intermediate. For this reason, the method of increasing spontaneous polarization by directly introducing a polar group into an asymmetric carbon atom has not been effectively used.

OBJECT OF THE INVENTION The present invention has been made in view of the above points. That is, the present invention contains a liquid crystal compound in which the polarity is improved by directly introducing a stable and large dipole moment fluorine atom into an asymmetric carbon atom, and at least one kind of the liquid crystal compound It is an object to provide a liquid crystal composition.

In the present invention, it is easy to change the length of the alkyl group, and as a result, as shown in H. Arnold, Z. Phys. Chem., 226, 146 (1964), the type and temperature of the liquid crystal phase developed in the liquid crystal state. An object of the present invention is to provide a liquid crystal compound capable of controlling the range, a liquid crystal composition containing the compound as at least one compounding component, and a liquid crystal device having the liquid crystal composition.

Means and Actions for Achieving the Purpose The present invention has been made to achieve the above-mentioned objects, and has the general formula (I) Wherein, R ₁ is a straight chain or branched alkyl group having 1 to 18 carbon atoms, R ₂ represents an alkyl group having 1 to 16 carbon atoms, C ^* denotes an asymmetric carbon atom. ] An optically active liquid crystalline compound represented by the above and a liquid crystal composition containing the compound as at least one compounding component are provided.

The present invention also provides a liquid crystal device using such a liquid crystal composition.

The optically active liquid crystalline compound represented by formula (I) of the present invention is preferably the following synthetic route from the optically active 2-fluoro-1-alkanol described in the specification of Japanese Patent Application No. 60-232886. Is synthesized by.

(Wherein R ₁ and R ₂ are as defined above) The liquid crystal composition of the present invention contains at least one optically active liquid crystalline compound represented by the above general formula (I) as a blending component. It is a thing.

Among the above compositions, those containing a ferroelectric liquid crystal as represented by the following formulas (1) to (13) as a blending component are capable of increasing spontaneous polarization and further decreasing the viscosity. Together, it is possible to improve the response speed, which is preferable. In such a case, 0.1% of the liquid crystal composition which can obtain the optically active liquid crystalline compound of the present invention represented by the general formula (I) is used.
It is preferable to use it in a proportion of about 99% by weight, particularly 1 to 90% by weight.

Further, by blending with a smectic liquid crystal which is not chiral as shown in the following formulas 1) to 5), a composition usable as a ferroelectric liquid crystal can be obtained.

In this case, the optically active liquid crystalline compound of the present invention represented by the general formula (I) is preferably used in an amount of 0.1 to 99% by weight, especially 1 to 90% by weight of the obtained liquid crystal composition.

Here, the symbols indicate the following phases, respectively. Cryst: crystalline phase, SmA: smectic A phase, SmB: smectic B phase, Sm
C: smectic C phase, N: nematic phase, Iso: isotropic phase.

Further, the optically active liquid crystalline compound of the formula (I) is effective in preventing the generation of the reverse domain in the TN type cell by adding it to the nematic liquid crystal.

FIG. 1 is a schematic drawing of an example of a cell for explaining the operation of the ferroelectric liquid crystal. 11a and 11b are In
A substrate (glass plate) covered with a transparent electrode made of a thin film such as ₂ O ₃ , SnO ₂ or ITO (Indium-Tin Oxide), in which the liquid crystal molecular layer 12 is oriented so that it is perpendicular to the glass surface. Liquid crystal of SmC ^* phase or SmH ^* phase is enclosed.
A thick line 13 represents a liquid crystal molecule, and this liquid crystal molecule 13 has a dipole moment (P
⊥) 14 When a voltage higher than a certain threshold is applied between the electrodes on the substrates 21 and 11b, the helical structure of the liquid crystal molecules 13 is unraveled, and the dipole moment (P⊥) 14 is entirely oriented in the electric field direction. Can be changed. The liquid crystal molecule 13 has an elongated shape and exhibits refractive index anisotropy in the major axis direction and the minor axis direction thereof. Therefore, for example, if crossed Nicols polarizers are placed above and below the glass surface, the voltage It is easy to understand that the liquid crystal optical modulator has optical characteristics that change depending on the applied polarity.

The liquid crystal cell preferably used in the optical modulator of the present invention can be made sufficiently thin (for example, 10 μm or less). Thus, it is difficult to make the liquid crystal layer thin, and as shown in FIG. 2, the helical structure of the liquid crystal molecules is unwound even when no electric field is applied, and its dipole moment Pa or Pb is directed upward (24a) or downward (24a). Take either of the conditions of 24b). As shown in FIG. 2, an electric field Ea or Eb having a polarity equal to or higher than a certain threshold is applied to such a cell by the voltage applying means 21.
Given by a and 21b, the dipole moment is the electric field Ea
Or 24a upward or 2 downward corresponding to the electric field vector of Eb
4b, and the liquid crystal molecules are aligned in either the first stable state 23a or the second stable state 23b accordingly.

As described above, there are two advantages of using such ferroelectricity as an optical modulation element.

The first is that the response speed is extremely fast, and the second is that the alignment of the liquid crystal molecules has bistability. The second point will be further explained with reference to FIG. 2, for example. When an electric field Ea is applied, the liquid crystal molecules are aligned in the first stable state 23a, but this state is stable even when the electric field is cut off. When an electric field Eb in the opposite direction is applied, the liquid crystal molecules are in the second stable state 23b.
The molecules are oriented to change the direction of the molecules, but they remain in this state even when the electric field is cut off. Further, unless the applied electric field Ea or Eb exceeds a certain threshold value, the previous orientation state is maintained. In order to effectively realize such a high response speed and bistability, it is preferable that the cell is as thin as possible, and generally 0.5 μ to 20 μ, particularly 1 μ to 5 μ is suitable.

Next, a specific example of the driving method of the ferroelectric liquid crystal will be described with reference to FIGS.

FIG. 3 is a schematic diagram of a cell 31 having a matrix electrode structure in which a ferroelectric liquid crystal compound (not shown) is sandwiched in the middle. Reference numeral 32 is a scan electrode group, and 33 is a signal electrode group.
First, the case where the scan electrode S ₁ is selected will be described. FIGS. 4 (a) and 4 (b) show scanning signals, which are electric signals applied to the selected scanning electrode S ₁ and the other scanning electrodes (non-selected scanning electrodes) S ₂ and S, respectively. ₃ , S ₄ ...
Shows an electric signal applied to. 4 (c) and 4 (d) show information signals which are electric signals applied to the selected signal electrodes I ₁ , I ₃ , I ₅ and the unselected signal electrodes I ₂ , I ₄ , respectively. Shows.

4 and 5, the horizontal axis represents time and the vertical axis represents voltage. For example, when displaying a moving image, the scan electrode groups 32 are sequentially and periodically selected.
Now, a threshold voltage for giving a first stable state of a liquid crystal cell having bistability with respect to a predetermined voltage application time t ₁ or t _{2 is set} to −V _th1, and a threshold value for giving a stable state of 2 is set. When the voltage is + V _th2 , the electrode signal given to the selected scan electrode 32 (S ₁ ) is 2 V at phase (time) t _{1 and} phase (time) t at phase (time) t ₁ as shown in FIG. 4 (a). _{At 2} , the alternating voltage is −2V. When electric signals having a plurality of phase intervals different from each other in voltage are applied to the selected scan electrodes in this way, the liquid crystal is switched between the first and second stable states of the liquid crystal corresponding to the optical “dark” or “bright” state. An important effect is that the state change of can be promptly caused.

On the other hand, the other scan electrodes S _{2 to} S ₅ ... Are in the ground state as shown in FIG.
Is. The electric signal applied to the selected signal electrodes I ₁ , I ₃ , and I ₅ is V as shown in FIG. 4 (c),
The electrical signal applied to the signal electrode I _2, I ₄ which are not selected is -V as shown in FIG. 4 (d). In the above, each voltage value is set to a desired value that satisfies the following relationship.

V <V _th2 <3V −3V <−V _th1 <−V Among the respective pixels when such an electric signal is given, for example, the voltage waveforms applied to the pixels A and B in FIG. 5 is shown in FIGS. That is, as is clear from FIGS. 5A and 5B, in the pixel A on the selected scanning line, the voltage exceeding the threshold V _th2 at the phase t ₂ is reached.
3V is applied. In addition, the pixels B existing on the same scanning line
At −3, a voltage −3V exceeding the threshold −V _th1 is applied at phase t ₁ . Therefore, in the case where the signal electrode is selected on the selected scanning electrode line depending on whether the signal electrode is selected,
The liquid crystal molecules are aligned in the first stable state and, if not selected, in the second stable state.

On the other hand, as shown in FIGS. 5 (c) and 5 (d), the voltage applied to all pixels is V
Or, it is -V, and neither exceeds the threshold voltage. Therefore, the liquid crystal molecules in each pixel other than on the selected scanning line maintain the orientation corresponding to the signal state at the time of the previous scanning without changing the orientation state. That is, when the scan electrode is selected, the signal for one line is written, and the signal state can be held until the end of one frame and the next selection. Therefore, even if the number of scanning electrodes is increased, the substantial duty ratio remains unchanged, and the contrast is not deteriorated at all.

Next, let us consider the problems that may actually occur when driving as a display device. In Figure 3,
Of the pixels formed at the intersections of the scan electrodes S _{1 to} S ₅ ... And the signal electrodes I _{1 to} I ₅ ..., the shaded pixels are in the “bright” state, and the pixels shown in white are the “dark”. It corresponds to the state.
Now, paying attention to the display on the signal electrode I _{1 in} FIG. 3, the pixel (A) corresponding to the scan electrode S ₁ is in the “bright” state, and the other pixels (B) are all in the “dark” state. Is. As an example of the driving method in this case, FIG. 6 shows the scanning signal, the information signal applied to the signal electrode I ₁ and the voltage applied to the pixel A in time series.

For example, when driven as shown in FIG. 6, the scanning signal S ₁
Is scanned, at time t ₂ , pixel A has a threshold V _th2
Since a voltage of 3 V exceeding 10 V is applied, the pixel A is transferred (switched) to a stable state in one direction, that is, a "bright" state regardless of the previous history. After that, as shown in FIG. 6, the voltage of −V is continuously applied while scanning S _{2 to} S ₅ ...
Since this does not exceed the threshold value −V _th1 , the pixel A should be able to maintain the “bright” state, but in reality, one signal electrode (corresponding to “dark” in this case) corresponds to one signal electrode. ) Is displayed continuously, the number of scanning lines is extremely large, and the inversion phenomenon occurs when high-speed driving is required. However, the above-mentioned specific liquid crystal compound or a liquid crystal composition containing it. By using, such inversion phenomenon is completely prevented.

Further, in the present invention, in order to prevent the above-mentioned inversion phenomenon, it is preferable to provide an insulating film formed of an insulating material on at least one of the counter electrodes constituting the liquid crystal cell.

The insulating material used at this time is not particularly limited, but silicon nitride, silicon nitride containing hydrogen, silicon carbide, silicon carbide containing hydrogen, silicon oxide, boron nitride, hydrogen. Containing boron nitride, cerium oxide, aluminum oxide, zirconium oxide, inorganic insulating materials such as titanium oxide and magnesium fluoride, or polyvinyl alcohol, polyimide, polyamide imide, polyester imide, polyparaxylene, polyester, An organic insulating material such as polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, acrylic resin or photoresist resin is used as the insulating film. The thickness of these insulating films is 5000 Å or less, preferably 100 Å ~ 1
000Å, especially 500Å ~ 3000Å are suitable.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Synthesis of 4 '-[4 "-(2-fluorooctyloxy) phenyl] phenyl nonanoate (1) 4- [4'-(2" -fluorooctyloxy)
Synthesis of phenyl] phenol 20 g of 2-fluorooctanol was dissolved in 90 ml of pyridine, and 30 g of p-toluenesulfonic acid chloride was added thereto.
It was added in an ice-water bath at 0 ° C or lower for 20 minutes. After stirring at room temperature for 7 hours, the mixture was poured into 600 ml of ice water, acidified with a 6N aqueous hydrochloric acid solution, and extracted with methylene chloride. After washing the organic layer with water,
The extract was dried over magnesium sulfate, the solvent was distilled off, and the residue was purified by silica gel chromatography to obtain 39.9 g of 2-fluorooctyl-p-toluenesulfonate.

p, p′-biphenol 19.7 g 85% KOH 13.6 g ethanol 30
0 ml was added and refluxed. Under reflux, 39.9 g of the above 2-fluorooctyl-p-toluenesulfonate was added dropwise over 50 minutes. After refluxing for further 10 hours, the mixture was allowed to cool, poured into ice water 1 and acidified with concentrated hydrochloric acid (pH-1), extracted with ethyl acetate, washed with water, and dried over anhydrous magnesium sulfate. After distilling off the solvent, methylene chloride was added to remove the dissolved matter, and 4- [4 '-(2 "-fluorooctyloxy) was obtained as an insoluble matter.
7.37 g of phenyl] phenol was obtained.

IR (KBr) cm ^-1 3450,2980,2940,2870,1620,1510,1260,825 (2) Synthesis of 4 '-[4 "(2-fluorooctyloxy) phenyl] phenyl] nonanoic acid 4- [] To 2 g of 4 '-(2 "-fluorooctyloxy) phenyl] phenol, 7 ml of pyridine was added and dissolved. 1.5 g of nonanoic acid chloride was added dropwise under ice cooling. After stirring overnight at room temperature, pour into ice water and acidify with 6N hydrochloric acid (pH-1)
And extracted with ethyl acetate. After washing with water, it was dried over anhydrous magnesium sulfate. After distilling off the solvent, the residue was purified by silica gel column chromatography (methylene chloride / hexane = 10/3) and recrystallized from ethanol ethyl acetate to give nonanoic acid-
1.16 g of 4 '-[4 "(2-fluorooctyloxy) phenyl] phenyl was obtained.

IR (KBr) cm ^-1 2980,2950,2880,1770,1620,1510,1230,1165,840 Phase transition temperature (S ^* : Chiral smectic phase other than chiral smectic C phase) Example 2 2-Methyl-n-valeric acid-4 '-[4 "-(2-fluorooctyloxy) phenyl] phenyl 2-methyl Add 8 ml of thionyl chloride to 1 ml of -n-valeric acid and add 3
After refluxing for an hour, excess thionyl chloride was distilled off. Benzene was added and further distilled off to obtain an acid chloride.

4- [4 '(2 "-fluorooctyloxy) phenyl] phenol 2g, pyridine 7ml, toluene 5ml were added,
The above acid chloride was added dropwise over 10 minutes under ice cooling. After the dropping, the mixture was stirred overnight at room temperature. After pouring into ice water, acidify with 6N hydrochloric acid (pH-
1) and extracted with ethyl acetate. After washing with water, it was dried over anhydrous magnesium sulfate. The solvent was distilled off, purified by silica gel column chromatography (methylene chloride / hexane = 10/3), and recrystallized from ethanol to give 2-methyl-n.
0.9 g of 4 '-[4 "(2-fluorooctyloxy) phenyl] -valeric acid were obtained.

IR (KBr) cm ^-1 2980,2950,2880,1755,1615,1515,1230,1145 Phase transition temperature (S ^* : Chiral smectic phase other than chiral smectic C phase) Example 3 trans-4-propylcyclohexanecarboxylic acid-4 ′
-[4 "(2-fluorooctyloxy) phenyl]
Synthesis of phenyl 4- [4 '(2 "-fluorooctyloxy) phenyl] phenol 2g, pyridine 6ml, toluene 6ml were added,
A solution of trans-4-propylcyclohexanecarboxylic acid chloride (1.4 g) in toluene (5 ml) was added dropwise under ice cooling. After the dropping, the mixture was stirred overnight at room temperature and poured into 90 ml of ice water. The mixture was acidified (pH-1) with 6N hydrochloric acid and extracted with ethyl acetate. It was washed with water, 5% aqueous sodium hydrogen carbonate solution and water in this order, and dried over anhydrous magnesium sulfate. The solvent was distilled off and the residue was recrystallized from ethanol-ethyl acetate to obtain 1.04 g of trans-4-propylcyclohexanecarboxylic acid-4 '-[4 "(2-fluorooctyloxy) phenyl] phenyl.

IR (KBr) cm ^-1 2980,2950,2870,1750,1615,1510,1220,1140 Phase transition temperature Example 4 A polyimide film (a polyamic acid resin composed of a combination of pyromellitic dianhydride and 4,4′-diaminodiphenyl ether) having a film thickness of 1000 Å was formed on each of opposite matrix electrodes formed of crossed strips of ITO. 5% by weight N-methylpyrrolidone solution was applied and formed by a ring closure reaction by heating at a temperature of 250 ° C.), and the surface of this polyimide film was rubbed in parallel with each other to form a cell having a cell thickness of 1 μm. Created.

Then, the following composition A was injected into the above-mentioned cell under an isotropic phase by a vacuum injection method and sealed. After that, slowly cool (1
A liquid crystal cell of SmC ^* was prepared by (° C./hour).

Liquid crystal composition A A crossed Nicol polarizer and an analyzer were arranged on both sides of the liquid crystal cell, and a waveform signal shown in FIGS. 4 and 5 was applied between the opposing matrix electrodes. At this time, the scanning signal is an alternating waveform of +8 volts and -8 volts shown in FIG. 4 (a),
The writing information was +4 volt and -4 volt, respectively. Also, one frame period is set to 30 msec.

As a result, even if the liquid crystal device was subjected to the memory drive type time division drive described above, a normal moving image display was obtained without any inversion of the written state.

Comparative Example 1 Nonanoic acid-4'- represented by the above-mentioned general formula (I) in the liquid crystal composition used in preparing the liquid crystal element of Example 4 was used.
[4 ″ (2-Fluorooctyloxy) phenyl] The following comparative liquid crystal B omitting phenyl was prepared, and a liquid crystal element was prepared using the comparative liquid crystal. These liquid crystal elements were driven by the same method as described above. However, due to the inversion phenomenon, a normal video was not displayed.

Comparative liquid crystal B Example 4 5 parts by weight of the liquid crystalline compound of Example 1 was added to 95 parts by weight of p, p-pentylazoxybenzene to obtain a liquid crystal composition. TN cell (twisted
Nematic cells) were observed to have a significantly reduced reverse domain as compared to TN cells produced without the addition of this compound.

〔The invention's effect〕

The novel liquid crystal compound of the present invention or the liquid crystal composition having the liquid crystal compound is a liquid crystal compound or a liquid crystal composition that improves the response speed, and a liquid crystal device having these does not cause a reversal phenomenon even at high speed driving. It is a liquid crystal element that can display a normal moving image.

[Brief description of drawings]

1 and 2 are perspective views schematically showing a time-division driving liquid crystal element used in the present invention, FIG. 3 is a plan view of a matrix electrode structure used in the present invention, and FIGS. 4 (a) to 4 (d). ) Is an explanatory view showing an electric signal applied to a matrix electrode, FIGS. 5A to 5D are explanatory views showing a waveform of a voltage applied between the matrix electrodes, and FIG. 6 shows a liquid crystal device of the present invention. It is explanatory drawing of the time chart showing the electric signal to apply. 11a, 11b ... Substrate, 12 ... Liquid crystal molecular layer, 13 ... Liquid crystal molecule, 14 ... Dipole moment (P⊥), 23a ... First stable state, 23b ... Second stable state, 24a ...... Upward dipole moment, 24b …… Downward dipole moment, 31 …… Cell, 32 …… (S ₁ , S ₂ , S ₃ , ・ ・ ・) …… Scan electrode group, 33 …… (I ₁ , I ₂ , I ₃ , ・ ・ ・) …… Signal electrode group.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chieko Hioki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoko Yoko Yamada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation (56) References JP 63-22042 (JP, A) JP 63-99032 (JP, A) JP-B 5-33943 (JP, B2)

Claims (3)

[Claims] 1. The following general formula (I): [Here, R ₁ represents a linear or branched alkyl group having 1 to 18 carbon atoms, R ₂ represents an alkyl group having 1 to 16 carbon atoms, and C ^* represents an asymmetric carbon atom. ] The optically active liquid crystalline compound represented by these. 2. The following general formula (I) [Here, R ₁ represents a linear or branched alkyl group having 1 to 18 carbon atoms, R ₂ represents an alkyl group having 1 to 16 carbon atoms, and C ^* represents an asymmetric carbon atom. ] The liquid crystal composition containing at least 1 sort (s) of the compound represented by these. 3. The following general formula (I) [Here, R ₁ represents a linear or branched alkyl group having 1 to 18 carbon atoms, R ₂ represents an alkyl group having 1 to 16 carbon atoms, and C ^* represents an asymmetric carbon atom. ] A liquid crystal device comprising a liquid crystal composition containing at least one compound represented by the formula: