JPH083560A - Ferroelectric liquid crystal composition and optical switching element using the same - Google Patents

Abstract

PURPOSE:To obtain the stable composition, containing several specific kinds of compounds, having a wide temperature range assuming a chiral smectic C phase, excellent in contrast and high-speed responsiveness and useful for display devices, light valves, etc. CONSTITUTION:This liquid crystal composition contains (A) at least one kind of compound of formula I or II (R1 to R4 are each an alkyl; Z1 is O or a single bond); (B) at least one kind of compound of formula III (R5 and R5 are each an alkyl; X1 is O or a single bond; Y1 is H or F; C* indicates asymmetric carbon) and (C) at least one kind of compound of formula IV (R7 and R8 are each an alkyl; X2 is OCO, O or a single bond; Y2 is OCO or a single bond; Z2 is O or OCO). Furthermore, (D) at least one kind of compound of formula V (R9 and R10 are each an alkyl) is preferably contained therein. The amounts of the contained components are preferably 10-95wt.% component (A), 2-35wt.% component (B), 0.1-35wt.% component (C) and 2-30wt.% component (D).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a strong ferroelectric liquid crystal state and is useful as a material for optoelectronic-related elements used for displays such as liquid crystal televisions, optical printer heads, and light valves. The present invention relates to a dielectric liquid crystal composition and an optical switching device.

[0002]

2. Description of the Related Art In recent years, a display device utilizing the optical switching phenomenon of a ferroelectric liquid crystal has been proposed by NA Clark and ST Lagerwall [Applied Phys.
t.), 36 , 899 (1980)]. This device using the ferroelectric liquid crystal has bistability, and is superior in optical response to the order of μsec compared with the conventional liquid crystal device of the display type called TN type or STN type. It has features. In order to use these ferroelectric liquid crystal materials as actual device materials, various characteristics are required. Among them, the basic ones are to exhibit a chiral smectic C (Sc ^* ) phase in a wide temperature range including room temperature and to have a high-speed response. In addition to this, ferroelectric liquid crystal materials are required to have many physical properties and characteristics, but at present, these physical properties and characteristics requirements cannot be satisfied by a single compound. Therefore, it is necessary to use a ferroelectric liquid crystal composition in which some compounds are mixed. To obtain the ferroelectric liquid crystal composition, it is not always necessary to mix only the ferroelectric liquid crystal composition. If an optically active compound is added to a liquid crystal composition (base liquid crystal) which is a non-chiral compound and shows a smectic C (Sc) phase and is composed of a single liquid crystal compound or a plurality of compounds, a ferroelectric liquid crystal composition is obtained. You can get things. Conditions required for such a liquid crystal composition to satisfy good display characteristics are: (1) having a liquid crystal temperature range that covers a wide practical temperature range (2) having excellent electro-optical response (3) ) It has optical and electrical properties that give good visibility when the device is constructed.

The present inventor has previously found and proposed that the following liquid crystal composition can be used in a wide temperature range, exhibits high-speed response, and becomes a good display device (Japanese Patent Application No. 4).
-235854).

[0004]

Embedded image

In the above formula, R _{1 to} R ₆ and R _{9 to} R ₁₀ are alkyl groups, X ₁ is --O-- or a single bond, Y ₁ is a hydrogen atom or a fluorine atom, and Z ₁ is --O-- or a single bond. , C ^* represents an asymmetric carbon having optical activity.

[0006]

However, as a result of further research by the present inventor, even such a ferroelectric liquid crystal composition is not yet sufficiently satisfactory in terms of contrast, and there is room for further improvement. It turns out. The present invention is intended to solve the above problems, and provides a ferroelectric liquid crystal composition having a wide operating temperature range, high-speed response, and good contrast, and an optical switching element using the composition. To provide.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that when a specific compound having biphenyl or phenyl benzoate as a core is added to a ferroelectric liquid crystal composition as described above. The inventors have found that even if the addition amount is small, the tilt angle of the liquid crystal composition can be made small and the contrast can be remarkably improved, and the present invention has been completed.

That is, the ferroelectric liquid crystal composition according to the present invention comprises at least one compound represented by the following general formula (I) or (II) and a compound represented by the following general formula (III). It contains at least one kind of compounds and at least one kind of compounds represented by the following general formula (IV). The present invention also relates to an optical switching element having the ferroelectric liquid crystal composition as a constituent element.

[0009]

[Chemical 4]

In the above formula, R ₁ , R ₂ , R ₃ , R ₄ ,
R ₅ , R ₆ , R ₇ and R ₈ are alkyl groups, X ₁ is —O—
Or a single bond, Y ₁ is a hydrogen atom or a fluorine atom, Z ₁
Is -O- or a single bond, X ₂ is -OCO -, - O- or a single bond, Y ₂ is -OCO- or a single bond, Z ₂ is -O
-Or-OCO-, C ^* represents an asymmetric carbon to which optical activity is imparted.

As the composition of the liquid crystal composition, 10 to 9 of at least one kind of the compound represented by the general formula (I) is used.
5% by weight, 2 to 35% by weight of at least one compound of the general formula (III) and 0.1 to 30% by weight of at least one compound of the general formula (IV) It is preferable that Alternatively, 10 to 95% by weight of at least one compound represented by the general formula (II),
2 to 35 at least one of the compound species represented by (III)
It is preferable to contain 0.1% to 30% by weight and at least one kind of the compound represented by the general formula (IV). Further, 10 to 95% by weight of at least one of the compound species represented by the general formula (I), 10 to 95% by weight of at least one of the compound species represented by the general formula (II),
2 to 35 at least one of the compound species represented by (III)
It is preferable to contain 0.1% to 30% by weight and at least one kind of the compound represented by the general formula (IV).

Further, the liquid crystal composition is preferably a liquid crystal composition further containing a compound species represented by the following general formula (V). However, in the general formula (V), R ₉
And R ₁₀ represents an alkyl group. Further, this composition has 10 to 95% by weight of any one of the compound species represented by the general formula (I) and the compound species represented by the general formula (II).
2 to 35% by weight of at least one compound represented by formula (I), 0.1 to 30% by weight of at least one compound of formula (IV) and represented by formula (V) It is preferable that at least one kind of the compound is contained in an amount of 2 to 30% by weight. Furthermore, 10 to 95% by weight of at least one compound species represented by general formula (I), 10 to 95% by weight of at least one compound species represented by general formula (II),
At least one of the compounds represented by the general formula (III) is 2
To 35% by weight, 0.1 to 30% by weight of at least one compound of the general formula (IV) and 2 to 30% by weight of at least one compound of the general formula (V). Preferably.

[0013]

Embedded image

In the above general formulas (I) to (V), R _{1 to} R ₁₀
The carbon number of the alkyl group represented by is not particularly limited,
From the viewpoint of production or practical use such as availability of raw materials, an alkyl group having 18 or less carbon atoms, particularly 2 to 12 carbon atoms is preferable.

The liquid crystal composition of the present invention may contain, as the base liquid crystal, both the compound species of the general formula (I) and the compound species of the general formula (II), or only one of them. May be. However, when only one of the compound species of the general formula (I) and the compound species of the general formula (II) is used alone and contained in the liquid crystal composition and a chiral dopant is added thereto, Although the ferroelectric liquid crystal composition has a high response speed, it tends to exhibit the chiral smectic C phase only within a relatively narrow temperature range. However, by mixing the compound of the general formula (II) with the above general formula (I),
The response speed of the ferroelectric liquid crystal composition can be increased, and at the same time, the temperature range for taking the chiral smectic C phase can be widened. Therefore, the liquid crystal composition used in the present invention preferably contains both the compound species of the general formula (I) and the compound species of the general formula (II).

The compound represented by the general formula (I) is
Zaschke method [Journal of Prakt. Chem. 317, 617 (1
975)], and can be synthesized from a commercially available reagent according to the following scheme. However, in the following formulas, R _{1 and} R ₂ represent the same alkyl groups as in the general formula (I).

[0017]

[Chemical 6]

Representative examples of the compounds represented by the general formula (I) are shown in Table 1 together with their phase transition temperatures. In addition,
In the table, "Cr" is a crystal, "Sc" is a smectic C phase,
S _A is a smectic A phase, N is a nematic phase, S _X is a smectic X phase, Ch is a cholesteric phase, and I is a liquid phase (the same applies to each table below).

[0019]

[Table 1]

The compound of the general formula (II) is, for example, an intermediate 2- (4-hydroxyphenyl) -5-alkylpyrimidine or 2- (, which is obtained according to the synthetic method of the compound of the general formula (I). 4-hydroxyphenyl)
It can be obtained by condensing -5-alkyloxypyrimidine with alkanoic acid to esterify it.
Z ₁ of the compound of the general formula (II) can be substituted between —O— and a single bond, and those having any group have the same function as described above. However, a compound in which Z ₁ is a single bond has a low melting point and is therefore more preferable. Representative examples of the compound of the general formula (II) are shown in Table 2 together with their phase transition temperatures.

[0021]

[Table 2]

The compound of the general formula (III) is a compound having a function as a chiral dopant, and is extremely superior to the base liquid crystal composed of the compound of the general formula (I) and / or the compound of the general formula (II). Good compatibility. By adding the compound of the general formula (III) to such a base liquid crystal, a ferroelectric property is imparted to the liquid crystal composition, and a stable ferroelectric liquid crystal composition having a fast response speed in a wide temperature range. Can be obtained.

X ₁ of the compound of the general formula (III) is --O.
-Can be substituted with a single bond, and Y ₁ can be substituted with hydrogen and fluorine, and those having any group can achieve the same effect. However, in particular, a compound in which X ₁ is —O— and Y ₁ is fluorine is more preferable because it has the effect of stabilizing the cholesteric phase when added to the liquid crystal composition.

Among the compounds of the above general formula (III), compounds in which Y ₁ in the formula is hydrogen, that is, 5- [4- (2-
Fluoro-2-methylalkanoyloxy) phenyl]
2- (4-alkyloxyphenyl) pyrimidine or 5- [4- (2-fluoro-2-methylalkanoyloxy) phenyl] -2- (4-alkylphenyl) pyrimidine is, for example, 5- (4-hydroxy). Phenyl)
2- (4-alkyloxyphenyl) pyrimidine or 5- (4-hydroxyphenyl) -2- (4-alkylphenyl) pyrimidine is converted into optically active 2-fluoro-
2-methylalkanoic acid or optically active 2-fluoro-
It can be obtained by esterification with 2-methylalkanoic acid chloride (JP-A-3-15136).
No. 8).

Further, among the compounds of the above general formula (III),
A compound in which Y ₁ in the formula is fluorine, that is, 2- (2
-Fluoro-4-alkyloxyphenyl) -5- [4
-(2-Fluoro-2-methylalkanoyloxy) phenyl] pyrimidine or 2- (2-fluoro-4-alkylphenyl) -5- [4- (2-fluoro-2-methylalkanoyloxy) phenyl] pyrimidine is For example, 2- (2-fluoro-4-alkyloxyphenyl) -5- (4-hydroxyphenyl) pyrimidine or 2- (2-fluoro-4-alkylphenyl) -5-
(4-Hydroxyphenyl) pyrimidine can be obtained by esterification with optically active 2-fluoro-2-methylalkanoic acid in the presence of a dehydration condensing agent such as dicyclohexylcarbodiimide (Japanese Unexamined Patent Publication No. Hei 4- (1994)
290875). Representative examples of the compound represented by the general formula (III) are shown in Table 3 together with their phase transition temperatures.

[0026]

[Table 3]

The compound of the general formula (IV) is a compound having biphenyl or phenyl benzoate as a core. Although this compound has a wide temperature range in which it takes a smectic A phase by itself, it has the above general formula (I) and / or (II)
By adding it to the ferroelectric liquid crystal composition containing the compound of formula (1) and the compound of formula (III), the tilt angle of the chiral smectic C phase can be reduced to make the contrast clear and the response time can be improved. It has a remarkable function that it can be speeded up.

This compound species exerts a remarkable effect when added in an extremely small amount, that is, in an amount of 0.1% by weight or more. However, if the addition amount of this compound exceeds 30% by weight, the range of the smectic A phase of the ferroelectric liquid crystal composition is widened and the cholesteric phase disappears, so that the orientation is deteriorated and the response time is deteriorated. Tend. Therefore,
The addition amount of the compound species is preferably 30% by weight or less, and particularly preferably 1 to 5% by weight.

X _{2 in} the compound of the general formula (IV) is --OCO.
-, -O- or a single bond, Y ₂ is -OCO- or a single bond, and Z ₂ is each substitutable between -O- or -OCO-, and those having any group are the same as above. Have a function. However, in particular, X ₂ is —OCO—, Y
_The compound in which ₂ is a single bond and Z ₂ is —O— is more excellent in the above-mentioned functions such as improvement in contrast and improvement in response speed.

Among the compounds represented by the general formula (IV),
4-alkyloxy-4′-alkyloxycarbonylbiphenyl, which is a compound in which X ₂ is —OCO—, Y ₂ is a single bond, and Z ₂ is —O—, is a compound in which 4,4′-hydroxybiphenylcarboxylic acid is converted into an alkaline compound. It can be obtained by alkoxylating with an alkyl halide in the presence and then esterifying this with an alkanol.

X ₂ is --O--, Y ₂ is a single bond, and Z ₂ is --O.
4-alkyloxy-4′-alkyloxybiphenyl, which is a compound consisting of −, is 4-alkyloxy-4 ′
It can be obtained by alkylating hydroxybiphenyl or 4-alkyl-4'-hydroxybiphenyl in the presence of an alkyl halide and an alkali such as potassium hydroxide. X ₂ and Y ₂ are single bonds, Z ₂
4-alkyl-4′-alkyloxybiphenyl, which is a compound consisting of —O—, is 4-alkyloxy-4 ′.
It can be obtained by alkylating hydroxybiphenyl or 4-alkyl-4'-hydroxybiphenyl in the presence of an alkyl halide and an alkali such as potassium hydroxide. Among the compounds represented by the general formula (IV), the above compounds in which Y ₂ is —OCO— are esterified with a benzoic acid derivative and a phenol derivative each having a predetermined substituent at the para-position in the presence of a dehydration condensation agent. It can be obtained.

Representative examples of the compounds represented by the general formula (IV) are shown in Table 4 together with their phase transition temperatures.

[0033]

[Table 4]

The compound of the general formula (V) deteriorates the response speed when added to the ferroelectric liquid crystal composition of the above general formula (I) and / or (II), (III), (IV). Without changing the phase sequence of the liquid crystal composition to Iso-Ch-
It can be S _A -Sc ^* , and the temperature range on the high temperature side where the chiral smectic C phase is taken can be widened. In general, the phase sequence when the ^{_{Iso-Ch-S A -Sc *}} , can be aligned with good ferroelectric liquid crystal composition. Therefore, the above general formula (I) and / or (I
By mixing the compound species of (I) and (III), (IV) and (V) respectively, the response speed is fast, the contrast is clear, the orientation is good, and the ferroelectricity can be used at a wide temperature range. A liquid crystal composition can be obtained.

The compound of the general formula (V) is prepared by converting 2- (4-alkyloxyphenyl) -5-hydroxypyridine into 4-
It can be obtained by condensing with alkylbenzoic acid. In addition, 2- (4-alkyloxyphenyl) -5
-Hydroxypyridine is obtained by alkylating the phenolic hydroxyl group of 4-bromophenol, metallizing it, and then reacting it with 2,5-dibromopyridine in the presence of a palladium catalyst to give a phenolpyridine derivative, and the remaining bromine is lithiated. It can be obtained by converting the compound to a boron derivative through oxidation and oxidizing with a hydrogen peroxide (JP-A-4-3).
38375). Representative examples of the compound represented by the general formula (V) are shown in Table 5 together with their phase transition temperatures.

[0036]

[Table 5]

In the present invention, the operating temperature range is wide,
In order to obtain a good contrast while having a high-speed response and good orientation, at least 10% by weight of the compound represented by the general formula (I) and at least one compound represented by the general formula (II) are used. 10 to 95% by weight, general formula (II
2-3% by weight of at least one compound of I), 0.1-35% by weight of at least one compound of general formula (IV) and 2-3 of at least one compound of general formula (V).
A mixture of 0% by weight added and mixed is particularly preferable.

[0038]

【Example】

(Example 1) Ferroelectric liquid crystal composition A was prepared by mixing the respective compounds (represented by the compound numbers in Tables 1 to 5 above) in the proportions (expressed by weight%) shown in Table 6. . Table 7 shows the phase transition temperature (° C.) of the liquid crystal composition A.

[0039]

[Table 6]

[0040]

[Table 7]

The physical properties of this liquid crystal composition A at 25 ° C. were spontaneous polarization of 12 nC / cm ² and inclination angle of 23.0 °. Next, this liquid crystal composition A was injected into a cell having a thickness of 2 μm and made of glass with a transparent electrode which was coated with polyimide and rubbed, and an electric field was applied with a chiral smectic C phase, and observation was performed under a crossed Nicols polarization microscope. I just did
A clear switching behavior was observed.

Further, using this cell, the 2-pulse method (2
When observed at 5 ° C., non-bias, pulse applied voltage: ± 30 V, duty: 400, burst: 2), the contrast value was 7 and the minimum pulse width was 500 μsec. However, the contrast value was measured using a polarizing microscope set under crossed nicols, with light entering the liquid crystal element, and measuring the intensity of the emitted light when a voltage was applied using a photomultiplier. Is the light intensity ratio between
The minimum pulse width is the shortest pulse width required for a clear switching operation.

A liquid crystal composition B was prepared by adding 2 parts by weight of the compound represented by the general formula (IV-I) in Table 4 above to 98 parts by weight of the above liquid crystal compound A. Table 8 shows the phase transition temperature (° C.) of the liquid crystal composition B.

[0044]

[Table 8]

The physical properties of the liquid crystal composition B at 25 ° C. were spontaneous polarization of 12 nc / cm ² and inclination angle of 20.0 °. Further, as a result of injecting this composition B into the same cell as above and observing by the same operation, a clear switching operation was observed, the contrast value was 17, and the minimum pulse width was 100 μsec. From this, it is clear that the addition of the compound represented by the general formula (IV) can enhance the contrast without deteriorating other physical properties.

Example 2 96 parts by weight of the liquid crystal compound A purified in Example 1 was added to the compound of the general formula (IV-I) used in Example 1.
4 parts by weight of the compound represented by
Was prepared. Table 9 shows the phase transition temperatures (° C.) of the liquid crystal composition C.

[0047]

[Table 9]

The physical properties of this liquid crystal composition C at 25 ° C. were spontaneous polarization of 10 nC / cm ² and tilt angle of 18.0 °. Further, as a result of injecting this composition C into the same cell as above and observing by the same operation, a clear switching operation was observed, the contrast value was 13, and the minimum pulse width was 200 μsec. From this, it is clear that the addition of the compound represented by the general formula (IV) can enhance the contrast without deteriorating other physical properties.

(Example 3) To 98 parts by weight of the liquid crystal compound A prepared in Example 1, 2 parts by weight of the compound represented by the general formula (IV-2) shown in Table 4 above was added to give a liquid crystal composition D. Prepared. The phase transition temperature (° C.) of this liquid crystal composition D is shown in Table 10.
It was shown to.

[0050]

[Table 10]

The physical properties of this liquid crystal composition D at 25 ° C. were spontaneous polarization of 10 nC / cm ² and inclination angle of 22.0 °. Further, as a result of injecting this composition D into the same cell as above and observing by the same operation, a clear switching operation was observed, the contrast value was 14, and the minimum pulse width was 180 μsec. From this, it is clear that the addition of the compound represented by the general formula (IV) can enhance the contrast without deteriorating other physical properties.

Example 4 To 98 parts by weight of the liquid crystal compound A prepared in Example 1, 2 parts by weight of the compound represented by the general formula (IV-4) shown in Table 4 above was added to obtain a liquid crystal composition E. Prepared. The phase transition temperature (° C.) of this liquid crystal composition E is shown in Table 11.
It was shown to.

[0053]

[Table 11]

The physical properties of this liquid crystal composition E at 25 ° C. were spontaneous polarization of 10 nC / cm ² and inclination angle of 22.0 °. Further, as a result of injecting this composition E into the same cell as above and observing by the same operation, a clear switching operation was observed, the contrast value was 15, and the minimum pulse width was 110 μsec. From this, it is clear that the addition of the compound represented by the general formula (IV) can enhance the contrast without deteriorating other physical properties.

Example 5 Ferroelectric liquid crystal composition F was prepared by mixing the respective compounds (indicated by the compound numbers in the above Tables 1 to 5) in the proportions shown in Table 12. Table 13 shows the phase transition temperature (° C.) of the liquid crystal composition F.

[0056]

[Table 12]

[0057]

[Table 13]

With respect to the physical properties of this liquid crystal composition F at 25 ° C., the spontaneous polarization is 7.5 nC / cm ² , and the tilt angle is 23.5 °.
Met. The 2-pulse method (25 ° C, bias; 1/5,
As a result of observation with a pulse applied voltage of ± 30 V, duty of 400, burst of 2), the contrast value was 2 and the minimum pulse width was 50 μsec. The above liquid crystal compound F98
A liquid crystal composition G was prepared by adding 2 parts by weight of the compound represented by the general formula (IV-I) shown in Table 4 to the parts by weight.
Table 14 shows the phase transition temperatures (° C.) of the liquid crystal composition G.

[0059]

[Table 14]

The physical properties of this liquid crystal composition G at 25 ° C. are spontaneous polarization of 6.9 nC / cm ² and inclination angle of 20.5 °, and the contrast value in the two-pulse method under the same conditions as above is 7 and the minimum pulse The width was 30 μsec. From this, it is clear that the addition of the compound represented by the general formula (IV) can enhance the contrast without deteriorating other physical properties.

Example 6 Ferroelectric liquid crystal composition H was prepared by mixing the respective compounds (represented by the compound numbers in Tables 1 and 3 above) in the proportions shown in Table 15. Table 16 shows the phase transition temperature (° C.) of the liquid crystal composition H.

[0062]

[Table 15]

[0063]

[Table 16]

With respect to the physical properties of this liquid crystal composition H at 25 ° C., the spontaneous polarization is 7.0 nC / cm ² , and the tilt angle is 21.7 °.
Met. The 2-pulse method (25 ° C, bias; 1/5,
As a result of observation with a pulse applied voltage of ± 30 V, duty of 400, burst of 2), the contrast value was 2 and the minimum pulse width was 63 μsec. The above liquid crystal compound H98
A liquid crystal composition I was prepared by adding 2 parts by weight of the compound represented by the general formula (IV-I) shown in Table 4 above.
Table 17 shows the phase transition temperature (° C.) of the liquid crystal composition I.

[0065]

[Table 17]

The physical properties of this liquid crystal composition I at 25 ° C. are as follows: spontaneous polarization 6.0 nC / cm ² , tilt angle 17.8 °.
Then, the contrast value in the two-pulse method under the same conditions as above was 7, and the minimum pulse width was 40 μsec. From this, it is clear that the addition of the compound represented by the general formula (IV) can enhance the contrast without deteriorating other physical properties.

Example 7 Ferroelectric liquid crystal composition J was prepared by mixing the respective compounds (represented by the compound numbers in Tables 2 and 3 above) in the proportions shown in Table 18. Table 19 shows the phase transition temperatures (° C.) of the liquid crystal composition J.

[0068]

[Table 18]

[0069]

[Table 19]

The physical properties of this liquid crystal composition J at 25 ° C. are as follows: spontaneous polarization: 5.0 nC / cm ² , tilt angle: 23.5 °
Met. The 2-pulse method (25 ° C, bias; 1/5,
As a result of observation with a pulse applied voltage of ± 30 V, duty of 400, burst of 2), the contrast value was 3 and the minimum pulse width was 30 μsec. The above liquid crystal compound J98
A liquid crystal composition K was prepared by adding 2 parts by weight of the compound represented by the general formula (IV-I) shown in Table 4 to the parts by weight.
Table 20 shows the phase transition temperatures (° C) of the liquid crystal composition K.

[0071]

[Table 20]

The liquid crystal composition K had physical properties at 25 ° C. of spontaneous polarization of 4.0 nC / cm ² , tilt angle of 20.8 °, and contrast value of 10 by the 2-pulse method under the same conditions as above.
The minimum pulse width was 18 μsec. From this,
It is clear that the addition of the compound represented by the general formula (IV) can enhance the contrast without deteriorating other physical properties.

[0073]

As described above, the ferroelectric liquid crystal composition of the present invention has a wide temperature range in which it takes a chiral smectic C phase,
It is stable and excellent in high-speed response and contrast, and is excellent as a material for optical switching elements such as display devices, optical printer heads and light valves, and is extremely useful.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G02F 1/13 500

Claims (3)

[Claims] 1. A compound represented by the following general formula (I) or (II), at least one compound represented by the following general formula (III), and a compound represented by the following general formula (IV): )
A ferroelectric liquid crystal composition containing at least one kind of compound represented by Embedded image (In the above formula, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ and R
₇ and R ₈ are alkyl groups, X ₁ is —O— or a single bond,
Y ₁ is a hydrogen atom or a fluorine atom, Z ₁ is —O— or a single bond, X ₂ is —OCO—, —O— or a single bond, Y ₂
Is -OCO- or a single bond, Z ₂ is -O- or -OC
O- and C ^* represent asymmetric carbons to which optical activity is imparted) 2. At least one compound represented by general formula (I) is 10 to 95% by weight, at least one compound represented by general formula (II) is 10 to 95% by weight, and
At least one compound represented by formula (III) is represented by 2 to 35% by weight, at least one compound represented by general formula (IV) is represented by 0.1 to 35% by weight and represented by the following general formula (V). 2. The ferroelectric liquid crystal composition according to claim 1, containing 2 to 30% by weight of at least one of the compounds described above. Embedded image (In the above formula, R ₉ and R ₁₀ represent an alkyl group) 3. An optical switching device comprising the ferroelectric liquid crystal composition according to claim 1 or 2 as a constituent element.