JP2764172B2 - Ferroelectric liquid crystal composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel liquid crystal composition useful as an electro-optical display material, and more particularly to a liquid crystal material having ferroelectricity. An object of the present invention is to provide a liquid crystal material which has excellent responsiveness and memory properties and can be used for a liquid crystal display device as compared with a liquid crystal material.

(Prior art)

Currently, the widely used liquid crystal display element is a so-called TN type using mainly nematic liquid crystal, and although it has many advantages and advantages, its responsiveness is a light emitting type such as a CRT. As compared with the display method, there is a significant disadvantage that the display method is much slower. Many liquid crystal display systems other than the TN type have been studied, but their responsiveness has not been improved.

However, a liquid crystal device using a ferroelectric smectic liquid crystal can respond 100 to 1000 times faster than a conventional TN type liquid crystal display element and has multi-stability. The gain (memory effect) was recently revealed. For this reason, the possibility of application to optical shutters, printer heads, thin-screen televisions, and the like is extremely high, and research and development are currently being conducted in various fields toward practical use.

The ferroelectric liquid crystal belongs to a tilt-type chiral smectic phase as a liquid crystal phase. Among them, a practically desirable one is chiral smectic C having the lowest viscosity (hereinafter abbreviated as SC ^* ). It is called a phase.

[Problems to be solved by the invention]

Liquid crystal compounds exhibiting the SC ^* phase (hereinafter referred to as SC ^* compounds) have been studied so far, and many compounds have already been synthesized. However, these SC
^{* The} compound alone must be used under the following conditions to be used as an optical switching element for ferroelectric liquid crystal display: (a) exhibit ferroelectricity over a wide temperature range including room temperature; (C) exhibit a long helical pitch, especially in a chiral nematic (hereinafter abbreviated as N ^* ) phase (d) have an appropriate tilt angle (e) have low viscosity (f) spontaneous polarization (G) show good orientation as a result of (b) (b) and (c). (H) show fast response as a result of (e) and (f). Nothing was known to be all satisfactory.

Therefore, at present, a liquid crystal composition exhibiting an SC ^* phase (hereinafter, referred to as an SC ^* liquid crystal composition) is used for examinations and the like.

In order to obtain good orientation, for example, JP-A-61-15
As disclosed in Japanese Patent No. 3623 and the like, in a liquid crystal having an N ^* phase in a high temperature region of the SC ^* phase, a method of increasing the length of the helical pitch of the N ^* phase is generally effective. In this case
When a smectic A (hereinafter, abbreviated as SA) phase is present in a temperature range between the SC ^* phase and the N ^* phase, the orientation becomes better. It is also known that a substance may be used in combination with an optically active compound that produces a right helix. (It is a known technique to adjust the helical pitch generated by adding an optically active substance to a nematic (hereinafter abbreviated as N) liquid crystal to an arbitrary length.) Although orientation was obtained, high-speed response was not necessarily obtained.

In order to show high-speed response, for example, as shown in a special lecture at the twelfth liquid crystal discussion meeting (preprints of the discussion meeting, p. 98), low-viscosity smectic C (hereinafter abbreviated as SC). An excellent method is to add a SC ^* compound having a large spontaneous polarization (hereinafter abbreviated as Ps) to a base liquid crystal composition exhibiting a phase (hereinafter referred to as SC base liquid crystal). According to this method, the helical pitch is relatively long because the proportion of the optically active compound that causes the helix is small, but the amount of the optically active compound added is small when trying to increase the helical pitch as the orientation becomes better. Therefore, there has been a problem that spontaneous polarization becomes too small and high-speed response cannot be obtained.

What has been used as the SC matrix liquid crystal so far is, for example, Japan Display '86 proceedings (3.
52) or JP-A-62-583.

(R and R 'represent an achiral alkyl group.) (R and R 'are the same as above.), The compound itself or its homologue is limited to those exhibiting the SC phase, or in addition, has a strong dipole (polarization) perpendicular to the molecular axis. This is a composition to which a liquid crystal compound is added as shown, and there has been a problem that if the temperature range of the SC phase is kept wide, the viscosity increases, and if the viscosity is reduced, the temperature range of the SC phase becomes narrow.

Therefore, it has been difficult to achieve good orientation and high-speed response at the same time with the prior art.

An object of the present invention is to provide a ferroelectric liquid crystal composition which can sufficiently satisfy both high-speed response and orientation.

[Means for solving the problem]

In order to solve the above problems, the present invention provides a liquid crystal composition exhibiting a smectic C phase (hereinafter referred to as an SC matrix liquid crystal used in the present invention). (1) When added to a liquid crystal material exhibiting a nematic phase, And (2) a composition comprising at least one optically active compound that produces a left-handed spiral when added to a liquid crystal material exhibiting a nematic phase, as a chiral dopant. A liquid crystal composition, which undergoes a phase transition to a chiral smectic C phase via a chiral nematic phase and then a smectic A phase upon cooling from an isotropic liquid state, and exhibits a chiral smectic C phase in a wide temperature range including room temperature. Provided is a liquid crystal composition.

The SC matrix liquid crystal used in the present invention has a phase sequence of (I) I (isotropic liquid) phase → N phase → SA phase → SC phase at the high temperature side of the SC phase when the temperature is lowered. One having a phase sequence of I phase → SA phase → SC phase (c) One having a phase sequence of I phase → N phase → SC phase or (d) One having a phase sequence of I phase → SC phase Although those having a phase series are used,
The choice of (a) to (d) depends on the chiral dopant used simultaneously. The most versatile is (a), in which the nematic nature of the chiral dopant (when added to SC matrix liquid crystals, tends to broaden the temperature range of the N ^* phase and narrow the temperature range of the SA phase). If (b) is strong, the smectic A property of the chiral dopant (when added to the SC matrix liquid crystal, the temperature range of the SA phase is likely to be widened and the temperature range of the N ^* phase is likely to be narrow), (C) and also SC
The use of (d) is most suitable when the properties are weak and the temperature range of the N ^* phase and the SA phase is easily widened. What is important is that when SC ^* liquid crystal composition is used, I → N ^* → SC → SC ^*
Is to show the phase sequence of

As the SC matrix liquid crystal used in the present invention, a composition comprising a compound exhibiting an SC phase as conventionally used can be used. Is more preferred.

That is, (I) a composition mainly composed of a compound having a bicyclic structure and exhibiting an SC phase at a temperature close to room temperature or a homolog thereof (a compound differing only in an alkyl chain) (hereinafter referred to as a medium temperature base liquid crystal). (II) It has a bicyclic structure, has a small number of polar groups in the molecule, and has a low viscosity by adding a low-viscosity compound (hereinafter referred to as a reduced viscosity liquid crystal). (III) It has been reduced by adding a reduced viscosity liquid crystal. In order to increase the maximum temperature of the SC phase, a composition comprising a compound having a high TC point (representing the maximum temperature of the SC phase or SC ^* phase) or a compound having a ring structure of three or more rings or a homolog thereof (hereinafter, referred to as a compound). (Referred to as high-temperature liquid crystal).

(I) Medium-Temperature-Range Base Liquid Crystal The medium-temperature-range host liquid crystal as used herein means that a liquid crystal compound constituting the liquid crystal is optically inactive, has a bicyclic or tricyclic structure, and has a tricyclic structure. Wherein at least one ring is a cyclohexyl ring and is composed of a compound exhibiting the SC phase or a homologue differing only in the number of carbon atoms and the shape of the alkyl chain thereof, and at least one compound in the homologue is at 10 ° C. It is a compound showing an SC phase which may be monotropic in the above-mentioned arbitrary temperature range of 1 ° C. or more. However, in the case of a three-ring structure, it is a liquid crystal in which the upper limit temperature of the SC phase is less than 90 ° C, and indicates an SC phase which may be monotropic at an arbitrary temperature range of 10 ° C to 80 ° C at an arbitrary temperature range of 10 ° C or more. is there.

Representative compounds used as a medium temperature parent are listed below. However, in the general formula shown below,
R ₁ and R ₂ each independently represent an alkyl group having 1 to 18 carbon atoms.

(II) Thinned liquid crystal The thinned liquid crystal referred to herein is a low-viscosity liquid crystal compound or composition, and the low-viscosity compound constituting the compound has a bicyclic structure and does not necessarily have to show an SC phase. By adding to the liquid crystal at a medium temperature range, it contributes to the improvement of the responsiveness. At least one of both side chains is preferably an alkyl group having 6 to 12 carbon atoms, and particularly preferably, both side chains have carbon atoms. A compound which is an alkyl group of the number 6 to 12,
It is characterized in that the number of ester bonds contained in the molecule is one or less.

Representative compounds used as the reduced viscosity liquid crystal are listed below. However, in the following general formula, R ₁ , R
₂ each independently represents an alkyl group having 1 to 12 carbon atoms.

(III) High-temperature liquid crystal The high-temperature liquid crystal referred to herein is a compound mainly consisting of a three-ring structure or a ring having more than three rings and showing an SC phase, which is not optically active, a homologue thereof, or a composition containing these compounds. The compound exhibiting the SC phase has an upper limit temperature of the SC phase of 90 ° C. or higher, and exhibits the SC phase in a temperature range having a temperature width of at least 5 ° C .; May be less than 90 degrees, the temperature range may be less than 5 degrees, or the SC phase may be monotropic. As a composition, the upper limit temperature of the SC phase is 90 ° C. or more. And shows the SC phase in a temperature range of at least 5 degrees or more.

Representative compounds used as high-temperature liquid crystals are listed below. However, in the general formula shown below, R ₁ , R ₂
Each independently represents an alkyl group having 1 to 18 carbon atoms.

Among the above compounds, the compounds represented by the formulas (Ia) and (Ib) are preferable as the medium temperature base liquid crystal, and the compounds represented by the formulas (Ia-1) and (Ia-5) And the formula (I
The compound represented by -b-1) is particularly preferred. As the reduced viscosity liquid crystal, compounds represented by the formulas (II-a) and (II-b) are preferable, and the compounds represented by the formulas (II-a-1) and (II-a-) are preferable.
Compounds represented by 6) and formula (II-b-1) are particularly preferred. As the high-temperature liquid crystal, compounds represented by the formulas (III-a), (III-b) and (III-c) are preferable, and the compounds represented by the formulas (III-a-1) and (III-a-2) are preferable. ), Formula (III-a-13), Formula (III-b-1), Formula (III-c-
Compounds represented by 1) and formula (III-c-3) are particularly preferred.

Among SC parent liquid crystals using these compounds, (I) a medium temperature host liquid crystal composed of a compound represented by the formula (Ia-1) or (Ib-1); a-6) or a thinned liquid crystal comprising a compound represented by the formula (II-b-1); and (III) a formula (III-a-1), a formula (III-a-2), or a formula (III-c-). Particularly preferred is a composition comprising a combination of a high-temperature liquid crystal comprising the compound represented by 1) or the formula (III-c-3).

The blending ratio of the medium temperature base liquid crystal is preferably from 1 to 90% by weight, particularly preferably from 5 to 75% by weight of the SC base liquid crystal. The compounding ratio of the reduced viscosity liquid crystal is preferably 1 to 50% by weight of the SC base liquid crystal, and particularly preferably 5 to 40% by weight. The compounding ratio of the high-temperature liquid crystal is preferably 1 to 70% by weight of the SC base liquid crystal, and particularly preferably 5 to 60% by weight.

In the case of a composition comprising the above particularly preferred combination as the SC base liquid crystal, 50 to 70% by weight of a medium temperature range base liquid crystal, 15 to 25% by weight of a thinned liquid crystal, and 15 to 25% by weight of a high temperature liquid crystal are mixed. Is particularly preferred.

The chiral dopant used in the present invention includes (1)
A compound exhibiting an SC ^* phase, (2) a compound exhibiting only a liquid crystal phase other than the SC ^* phase, or (3) a compound exhibiting no liquid crystal properties can be used. In the case of (3), an SC matrix liquid crystal is used. It is preferable to use a compound having a skeleton similar to a liquid crystal in order to prevent a tendency that the liquid crystallinity of the SC ^* liquid crystal composition obtained by adding to the liquid crystal composition is reduced.

The important properties of the SC ^* liquid crystal composition that the chiral dopant brings to the liquid crystal composition are the helical pitch induced, the direction of spontaneous polarization, and the magnitude thereof. These are the optically active sites of each compound constituting the chiral dopant. Most affected by

Representative examples of optically active groups in optically active compounds which have been used as additives to chiral dopants, SC ^* compounds or nematic liquid crystals are shown below.

In each of the above general formulas, m represents an integer of 1 to 4,
n represents an integer of 1 to 10, R ₃ represents an alkyl group having 3 to 8 carbon atoms, R ₄ represents an alkyl group having 2 to 10 carbon atoms, and R ₅ represents an alkyl group having 1 to 10 carbon atoms. R ₆ represents an alkyl group having 1 to 4 carbon atoms.

An optically active compound containing only optically active groups represented by formulas (IV-1) to (IV-22) as an optically active group is represented by SC
The spontaneous polarization induced when a SC ^* liquid crystal composition is added to a parent liquid crystal is very small, and even when an SC ^* phase alone is exhibited, most of the spontaneous polarization is only 10 nC / cm ² or less.

On the other hand, optically active groups represented by formulas (IV-31) to (IV-95)
An optically active compound containing an optically active group represented by
Spontaneous polarization is large to induce upon the SC ^* liquid crystal composition was added to the SC mother liquid crystal, in a case where solely showing the SC ^* phase
Some of them show a large value of 300 nC / cm ² or more.

Representative examples of the basic skeleton of the optically active compound having such an optically active group at the terminal are listed below.

Each basic skeleton in which the benzene ring of each of the above basic skeletons is substituted with a fluorine atom, a chlorine atom, a bromine atom, a methyl group, a methoxy group, a cyano group or a nitro group can also be used.

The chiral group is bonded to one side of the basic skeleton as described above, and the other side is an alkyl group, an alkoxyl group, an alkanoyloxy group, an alkoxycarbonyl group, an optically active compound bonded to an alkoxycarbonyloxy group, or the like. An optically active compound having the chiral group bonded to both sides can be effectively used as a component of the chiral dopant. In particular, in the optically active compound in which the chiral groups are bonded to both sides, it is desirable that each chiral group is not the same and the direction of the spontaneous polarization is the same, or that one side induces a much stronger spontaneous polarization with respect to the other. Further, a compound in which the twist directions of the spirals are opposite to each other is desirable.

Representative optically active compounds that are preferable as constituents of the chiral dopant comprising the chiral group and the basic skeleton are listed below.

(VI-a) a compound having an optically active group only on one side chain of the basic skeleton In the above general formula, ^Ra is an alkyl group having 1 to 20 carbon atoms,
Alkoxyl group, alkanoyloxy group, alkoxycarbonyl group, an alkoxycarbonyloxy group or an alkoxyalkyl, R ₄ represents an alkyl group having 2 to 10 carbon atoms, R ₅ represents an alkyl group having 1 to 10 carbon atoms , X represents a fluorine atom or a chlorine atom, and Z represents -CO
O -, - OCO -, - CH 2 O -, - OCH 2 - or a single bond.

(VI-b) Compound having optically active groups on both sides of basic skeleton In the above formula, R ₄ and R ₄ ′ each independently represent an alkyl group having 2 to 10 carbon atoms, and R ₅ and R ₅ ′ each independently represent an alkyl group having 1 to 10 carbon atoms. , L is 0-5
X represents a fluorine atom or a chlorine atom, and Y represents a single bond, -O-, -OCO-, -COO- or -OCOO.
- represents, Z is -COO -, - OCO -, - CH 2 O -, - OCH 2
— Or a single bond, and Z ′ is Represents

The above-mentioned chiral dopant is suitably added to the SC matrix liquid crystal at a ratio of 1 to 60% by weight and used as an SC ^* liquid crystal composition, but is more preferably added at a ratio of 2 to 50% by weight. Is preferred. When the addition ratio of the chiral dopant is more than 60% by weight, the spontaneous polarization increases, but the viscosity of the SC ^* liquid crystal composition increases because the chiral dopant itself is much more viscous than the parent liquid crystal, resulting in a higher viscosity. This is not preferable because it tends to adversely affect high-speed response. Also, an increase in the amount of the chiral dopant added is not preferable because the helical pitch is shortened, which tends to adversely affect the orientation. On the other hand, if the addition ratio of the chiral dopant is less than 1% by weight, the spontaneous polarization becomes too small, and high-speed response cannot be expected.

The value of the spontaneous polarization of the SC ^* liquid crystal composition, it is preferable to adjust the proportion of the added chiral dopant to be in the range of 3~30nC / cm ^2, when the chiral dopant for the SC ^* phase alone 100 nC / In the case of a chiral dopant exhibiting a spontaneous polarization of about ² cm or inducing a spontaneous polarization of a strength corresponding thereto, the addition ratio of the chiral dopant is preferably in the range of 20 to 40% by weight, and 300 n
In the case of a chiral dopant showing a strong spontaneous polarization of C / cm ² or more, the addition ratio of the chiral dopant is preferably in the range of 2 to 25% by weight. As the spontaneous polarization induced by the chiral dopant increases, the most desirable addition ratio decreases. However, the addition ratio of the chiral dopant composed of the exemplified optically active compound does not fall below 1% by weight.

SC ^* liquid crystal composition of the present invention, N ^* phase during cooling from the isotropic liquid state, then although the phase transition to the SC ^* phase via the SA phase, phase from that time N ^* phase to SA phase From the transition temperature (hereinafter referred to as the N ^* -SA point), the SC ^* liquid crystal composition in which the pitch of the helix appearing in the N ^* phase from the N ^* -SA point to the once higher temperature side is 3 μm or more is more preferable. An SC ^* liquid crystal composition in which the pitch of the helix is 10 μm or more and the pitch of the helix divergently increases as approaching the N ^* -SA point is particularly preferable.

As a chiral dopant, a single optically active compound or SC ^* liquid crystal composition when added to SC matrix liquid crystal to obtain N ^*
When the composition of the optically active compound having the same twist direction of the helix appearing in the phase is used, the pitch of the helix tends to be shorter in a practical range of the concentration of the chiral dopant. SC ^* liquid crystal compositions having a helical pitch in the preferred range are difficult to obtain. Therefore, in order to adjust the helical pitch to the above preferred range, at least an optically active compound in which helical directions appearing in the N ^* phase are opposite to each other when added to the SC matrix liquid crystal to form an SC ^* liquid crystal composition is used. It is desirable to add to one kind of chiral dopant.

The helical pitch P (μm) appearing in the N ^* phase of the SC ^* liquid crystal composition containing a plurality of optically active compounds represents the concentration of each optically active substance as Ci, and the helical pitch per unit concentration as Pi (μm).
Then (Here, the pitch of the helix is positive for the right-handed winding and negative for the left-handed winding), and is used to calculate the P at the SA-N ^* point T ₀ of the SC ^* liquid crystal composition. ⁱ the P _T ⁱ
When You can choose Ci so that Here, Pi can be measured by adding a unit concentration of each optically active compound to the SC matrix liquid crystal having an N phase. Actually, T ₀ changes depending on each Ci, but each optically active compound is contained in the SC matrix liquid crystal, Etc. Only the SA-N ^* points when adding changes, much can be inferred quite accurately, in the case where the T ₀ of the estimated value T ₀ 'and compositions chosen therewith are largely different T ₀ The measurement may be performed again using T ₀ instead of '.

The temperature range showing the N ^* phase of the SC ^* liquid crystal composition of the present invention is as follows:
A range of 3 degrees or more and less than 30 degrees is preferable. When the temperature range showing the N ^* phase is less than 3, the phase transition to the SA phase is promptly performed when the temperature is lowered, and the liquid crystal molecules tend not to be sufficiently aligned in the N ^* phase, which is not preferable. If the temperature range showing the N ^* phase is 30 ° C. or higher, the clear point of the SC ^* liquid crystal composition becomes high, which tends to adversely affect the workability in the step of filling the cell with the liquid crystal material. Not preferred.

The chiral dopant, when added to the SC matrix liquid crystal, regardless of the presence or absence of the liquid crystal property of the chiral dopant itself, has (1) a tendency to expand the temperature range showing the N ^* phase, or (2) N ^* phase Each has its own properties, such as those that tend to reduce the temperature range that indicates SC ^{* of the} present invention
In order to adjust the temperature range showing the N ^* phase of the liquid crystal composition to the preferable range described above, in the case of (1), the SC base liquid crystal having a narrow temperature range showing the N phase or the SC base liquid showing no N phase A liquid crystal may be used, and in the case of (2), an SC matrix liquid crystal having a wide temperature range showing the N phase may be used. This method can be applied not only to the N ^* phase but also to the SA phase and the SC ^* phase. For example, when the chiral dopant expands only the SA phase of the SC ^* liquid crystal composition and reduces the N ^* phase and the SC ^* phase, the SC matrix liquid crystal has a high maximum temperature of the SC phase, Temperature range is wide and SC phase → N phase → I phase, or SA phase has narrow temperature range and SC phase →
What has a phase series of SA phase → N phase → I phase may be used.

Such a tendency of the chiral dopant can be easily known by measuring a change in the phase transition temperature of the SC ^* liquid crystal composition obtained by adding a certain amount of the chiral dopant to the SC matrix liquid crystal. From this result, the temperature range showing each phase, particularly the N ^* phase in the SC ^* liquid crystal composition can be easily adjusted.

The chiral dopants used in the present invention, by adding a certain amount of the SC mother liquid crystal, a certain degree or more of the spontaneous polarization (hereinafter abbreviated. And P _s) it is necessary to induce.

As previously mentioned, the SC ^* liquid crystal composition, the value of the P _s may be adjusted the amount of the chiral dopant so particularly in the range of 3~30nC / cm ² at around room temperature. However, when the value of P _s chiral dopant induces is small, increases the addition amount relative to SC mother liquid, to which the viscosity of the SC ^* liquid crystal composition is increased so accompanied, as a result, high speed It is not preferable because responsiveness tends to be lost. Therefore, the chiral dopant used in the present invention is 1.0 nC / cm when 10% by weight is added to SC matrix liquid crystal.
It is preferably one that can induce a ^more P _s, and particularly preferably it can induce 0.5nC / cm ² or more P _s when added 5% by weight.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples.
The gist and scope of the present invention are not limited by these examples. In Examples, "%" represents% by weight.

Example 1 (Preparation of SC Base Liquid Crystal (1)) A compound of the formula (Ia-1) as a medium temperature base liquid crystal, a compound of the formula (II-a-6) as a low viscosity liquid crystal, and a high temperature liquid crystal An SC matrix liquid crystal was prepared using the compound of the formula (III-a-1) in the following ratio.

This SC matrix liquid crystal has a melting point of −3 ° C.
Phase, SA phase up to 65 ° C, N phase up to 76.5 ° C, 76.5 ° C
As described above, the composition was a low-viscosity composition that became the I phase.

Example 2 (Preparation of SC Base Liquid Crystal (2)) A compound of the formula (Ia-1) as a medium temperature base liquid crystal, a compound of the formula (II-a-6) as a low viscosity liquid crystal, and a high temperature liquid crystal An SC matrix liquid crystal was prepared using the compound of the formula (III-a-2) in the following ratio.

This SC matrix liquid crystal was a low-viscosity composition that exhibited an SC phase up to 53 ° C. and an SA phase up to 83.5 ° C., and became an I phase at 83.5 ° C. or higher.

Example 3 (Preparation of SC Base Liquid Crystal (3)) A compound of the formula (Ia-1) as a medium temperature base liquid crystal, a compound of the formula (II-a-6) as a low viscosity liquid crystal, and a high temperature liquid crystal An SC matrix liquid crystal was prepared using the compound of the formula (III-c-1) in the following ratio.

The SC matrix liquid crystal was a low-viscosity composition that exhibited an SC phase up to 56.5 ° C. and an SA phase up to 80.5 ° C., and became an I phase at 80.5 ° C. or higher.

Example 4 (Preparation of SC Base Liquid Crystal (4)) A compound of the formula (Ia-1) as a medium temperature base liquid crystal, a compound of the formula (II-b-1) as a low viscosity liquid crystal, and a high temperature liquid crystal SC mother liquid crystals were prepared using the compound of the formula (III-a-1) in the following ratio.

This SC matrix liquid crystal has an SC phase up to 47.5 ° C and SA up to 56.0 ° C.
The composition was a low-viscosity composition that exhibited a phase and an N phase up to 65.0 ° C. and became an I phase at 65.0 ° C. or higher.

Example 5 (Preparation of SC Base Liquid Crystal (5)) The compound of the formula (Ib-1) as a medium temperature base liquid crystal, the formula (II-a-1) as a low viscosity liquid crystal, and the above formula as a high temperature liquid crystal An SC parent liquid crystal was prepared using the compound of (III-a-1) in the following ratio.

This SC matrix liquid crystal was a low-viscosity composition that exhibited an SC phase up to 75.0 ° C. and an N phase up to 98.5 ° C., and became an I phase at 98.5 ° C. or higher.

Example 6 (Preparation of chiral dopant (1)) When SC ^* liquid crystal composition was added to SC matrix liquid crystal, N
^{* As} a compound that causes a right-handed spiral to appear in the phase, the formula (The pitch of the helix that appears in the N ^* phase when 10% of this compound is added to the SC matrix liquid crystal is 4.7 μm at 60 ° C.) (Pitch of the helix that would give the compound N ^* phase when added 10% SC mother liquid crystal is 11.9μm at 60 ° C..) By mixing the compound 27%, spiral to appear to N ^* phase A chiral dopant having a controlled pitch was prepared.

The value of the spontaneous polarization at 25 ° C. of the SC ^* liquid crystal composition obtained by adding 10% of this chiral dopant to the SC matrix liquid crystal obtained in Example 1 was 5.5 nC / cm ² .

Example 7 (Preparation of chiral dopant (2)) When SC ^* liquid crystal composition was added to SC matrix liquid crystal,
^{* As} a compound that causes a right-handed spiral to appear in the phase, the formula (The pitch of the helix that appears in the N ^* phase when 10% of this compound is added to the SC matrix liquid crystal is 1.3 μm at 60 ° C.). By mixing the compound of 50% (this compound is 1.3 .mu.m. In pitch 60 ° C. of the helix to be appearing in N ^* phase when added 10% SC mother liquid crystal), the spiral to appear to N ^* A pitch adjusted chiral dopant was prepared.

The value of the spontaneous polarization at 25 ° C. of the SC ^* liquid crystal composition obtained by adding 10% of this chiral dopant to the SC matrix liquid crystal obtained in Example 1 was 10 nC / cm ² .

Example 8 (SC ^* Preparation of liquid crystal composition (1)) SC mother liquid 80.0% by weight obtained in Example 1 to prepare a SC ^* liquid crystal composition consisting of the chiral dopant 20.0% by weight obtained in Example 6.

The SC ^* SC to the melting point is 50.5 ° C. at -26 ° C. The liquid crystal composition ^*
The phase, the SA phase up to 66 ° C., and the N ^* phase up to 71 ° C., respectively, became I phase at 71 ° C. or higher.

The helical pitch of this composition at 66.1 ° C. was 30 μm, and when it was filled in an alignment-treated cell and gradually cooled from the isotropic liquid phase, it showed extremely good orientation.

A 50 Hz rectangular wave with an electric field strength of 10 V _pp / μm was applied to this cell, and its electro-optical response was measured.
A high-speed response of 38 μs at ℃ was confirmed.

The spontaneous polarization at this time is 14.8 C / cm ² , and the tilt angle is 22.0
Was ゜.

We were prepared Example 9 (SC ^* Preparation of liquid crystal composition (2)) composed of chiral dopants 16.0% by weight was obtained in SC mother liquid crystal 84 wt% as in Example 6 obtained in Example 3 SC ^* liquid crystal composition.

This composition showed an SC ^* phase at a temperature of 62.5 ° C. or lower, and showed good orientation as in Example 8.

When the high-speed response was measured in the same manner as in Example 8, a high-speed response of 50 μsec at 25 ° C. was confirmed.

The spontaneous polarization at this time is 10.6 C / cm ² , and the tilt angle is 19.4
Was ゜.

It was prepared Example 10 (SC ^* Preparation of liquid crystal composition (3) consisting of a chiral dopant 16 wt% obtained in SC mother liquid crystal 84 wt% as in Example 6 obtained in Example 4 SC ^* liquid crystal composition.

This composition showed an SC ^* phase at 54.5 ° C. or lower, and showed good orientation as in Example 8.

When high-speed response was measured in the same manner as in Example 8,
A high-speed response of 50 μs at 25 ° C. was confirmed.

The spontaneous polarization at this time was 9.4 C / cm ² , and the tilt angle was 19 °.

〔The invention's effect〕

The ferroelectric liquid crystal composition of the present invention is a liquid crystal material having excellent alignment properties and high-speed response, and capable of operating in a wide temperature range including room temperature.

Therefore, the ferroelectric liquid crystal composition of the present invention is extremely useful as a material for a liquid crystal device using a ferroelectric smectic liquid crystal.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noboru Fujisawa 4-14-22 Namiki, Kawaguchi City, Saitama Prefecture (72) Inventor Takeshi Kuriyama 14549-1-301 Musaki, Sakura City, Chiba Prefecture (72) Inventor Kayoko Nakamura Chiba Prefecture 1-7-18-507 Kamagaya, Kamagaya City (56) References JP-A-2-695 (JP, A) JP-A-61-195187 (JP, A) JP-A-61-291679 (JP, A) JP-A-61-255323 (JP, A) JP-A-61-249022 (JP, A) Okano and Kobayashi, ed., “Liquid Crystal: Basics,” First Edition, Baifukan (November 1987) 178-P. 204

Claims (2)

(57) [Claims] A liquid crystal composition exhibiting a smectic C phase comprising a liquid crystal exhibiting a smectic C phase comprising a liquid crystal exhibiting a smectic C phase comprising a liquid crystal exhibiting a nematic phase, and a liquid crystal composition exhibiting a nematic phase. A liquid crystal composition comprising, as a chiral dopant, a composition comprising at least one compound and (2) at least one optically active compound which produces a left-handed helix when added to a liquid crystal material exhibiting a nematic phase. A liquid crystal composition which undergoes a phase transition to a chiral smectic C phase via a chiral nematic phase and then a smectic A phase upon cooling from an isotropic liquid state, and exhibits a chiral smectic C phase in a wide temperature range including room temperature. 2. A thinned liquid crystal comprising a compound having both ends of an alkyl group having 1 to 12 carbon atoms and at least one end being an alkyl group having 6 to 12 carbon atoms. The liquid crystal composition according to claim 1, wherein