JPH02286784A - Ferroelectric liquid crystal composition - Google Patents

Abstract

PURPOSE:To prepare a ferroelectric liquid crystal compsn. which exhibits chiral smectic C phase over a wide temp. range including room temp. and is excellent in the orientation and rapid response by adding a chiral dopant comprising an optically active compd. to a liquid crystal compsn. exhibiting chiral smectic C phase and contg. a medium-temp. range liquid crystal, a reduced viscosity liquid crystal, and a specific high-temp. liquid crystal. CONSTITUTION:A ferroelectric liquid crystal compsn. is prepd. by adding a chiral dopant comprising an optically active compd. (e.g. a compd. of formula VI or formula VII) to a liquid crystal compsn. which exhibits chiral smectic C phase and contains a medium-temp. range liquid crystal [e.g. a compd. of formula I (wherein R1 and R2 are each 1-18C alkyl)], a reduced viscosity liquid crystal [e.g. a compd. of formula II (wherein R1 and R2 are each 1-12C alkyl)], and a high-temp. liquid crystal contg. a compd. of formula III [wherein R<a> and R<b> are each 1-18C alkyl, or alkoxyl; and groups of formula IV and formula V are each (fluorine-substd.) p-phenylene, and at least one of them is p- phenylene].

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a novel liquid crystal composition useful as an electro-optical display material, and in particular provides a liquid crystal material having ferroelectricity, which is different from conventional liquid crystal compositions. The present invention provides a liquid crystal material that can be used in liquid crystal display devices, particularly in response and memory performance, compared to liquid crystal materials.

[Prior art]

Currently, the liquid crystal display elements in wide use are mainly of the TN type, which utilizes nematic liquid crystals, and although they have many advantages, their responsiveness is not as good as CI. Compared to light-emitting display systems such as T, the major drawback was that it was much slower. Many liquid crystal display systems other than the TN type have been studied, but improvements in their responsiveness have not yet been achieved.

However, in liquid crystal devices using ferroelectric smectic liquid crystals, the 100 to 10
It has recently been revealed that because it is capable of a 00 times faster response and has bistability, it can retain the display even when the power is turned off (memory effect). For this reason, light shade 7
It has great potential for use in printers, printer heads, flat-screen televisions, etc., and research and development is currently underway in various fields to put it into practical use.

The liquid crystal phase of ferroelectric liquid crystals belongs to the tilted chiral smectic phase, and among these, the one that is practically desirable is chiral smectic C (hereinafter abbreviated as "sc"), which has the lowest viscosity. This is called a phase.

[Problem to be solved by the invention]

Liquid crystal compounds exhibiting "sc" phase (hereinafter referred to as "SC2 compounds") have been studied so far, and many compounds have already been synthesized. However, these
``The compound alone must meet the following conditions for use as an optical switching element for ferroelectric liquid crystal displays: (a) It must exhibit ferroelectricity over a wide temperature range including room temperature, and (b) It must have an appropriate phase at high temperatures. Having a series (c) Particularly chiral nematic (hereinafter abbreviated as "N").

) exhibiting a long helical pitch in the phase; (d) having an appropriate tilt angle; (e) having low viscosity; (f) having a large value of spontaneous polarization above a certain level. No material has been known that satisfies all of the following: (1), (2), (2), and (3) exhibit good orientation.

Therefore, at present, liquid crystal compositions exhibiting an "sc" phase (hereinafter referred to as "SC" liquid crystal compositions) are currently being used for research purposes.

In order to obtain good orientation, for example, JP-A-61-1
As shown in Japanese Patent No. 53623 and the like, in liquid crystals having an N1 phase in the high temperature range of the SC''' phase, a method of increasing the helical pitch length of the N8 phase is generally effective.

In this case, if the smectic A (hereinafter abbreviated as SA) phase is present in the intermediate temperature range between the S09 phase and the N1 phase, the orientation will be better, and in order to increase the helical pitch, optical It is also known that an active substance may be used in combination with an optically active compound that produces right-handed helix. (It is already a known technique to adjust the helical pitch to an arbitrary length by adding an optically active substance to a nematic (abbreviated as N) liquid crystal.) However, some of these techniques do not provide good results. Although orientation can be obtained,
High-speed response could not be obtained.

In order to exhibit high-speed responsiveness, for example, low viscosity smectic C (hereinafter abbreviated as SC) is used, as shown in the special lecture at the 12th Liquid Crystal Conference (Proceedings of the same conference P, 98). ) phase (hereinafter referred to as SC matrix liquid crystal) has a spontaneous polarization (hereinafter abbreviated as P).

) A method of adding a compound with a large SC* is superior.

According to this method, the proportion of the optically active compound that produces the helix is small, so the helical pitch is relatively long. need to be,
Therefore, there was a problem in that the spontaneous polarization became too small, making it impossible to obtain high-speed response.

Furthermore, those that have been used hitherto as SC matrix liquid crystals are described in, for example, Japan Display 86 Lecture Proceedings (from page 352) or Japanese Patent Application Laid-open No. 1983-583.

RO÷COO-@-OR' (R, R' represent an achiral alkyl group) (R,
R' is the same as above. ), the compound itself or its homologues are limited to those exhibiting an SC phase, or compositions in which a liquid crystal compound is added that exhibits a strong dipole (polarization) in the direction perpendicular to the long axis of the molecule. However, if the temperature range of the SC phase is kept wide, the viscosity increases, and if the viscosity is decreased, the temperature range of the SC phase becomes narrow.

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

The problem to be solved by the present invention is to provide a ferroelectric liquid crystal composition that is fully satisfactory in both high-speed response and orientation.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a liquid crystal composition containing a medium temperature range liquid crystal, a reduced viscosity liquid crystal, and a high temperature liquid crystal and exhibiting a smectic C phase (hereinafter referred to as the SC matrix liquid crystal used in the present invention). A ferroelectric liquid crystal composition comprising a chiral dopant comprising an active compound, in particular a high temperature liquid crystal containing at least one of the compounds represented by the following general formula (A).
A ferroelectric liquid crystal composition containing a species and exhibiting an sc'' phase over a wide temperature range including room temperature is provided.

In the formula, R' and Rb each independently have 1 to 18 carbon atoms.
represents a straight-chain or branched alkyl group or alkoxyl group, but a straight-chain alkyl group, a straight-chain alkoxyl group,
Branched alkoxyl groups are preferred.

It is preferable that there be.

The SC base liquid crystal used in the present invention has a phase sequence of (a) I (isotropic liquid) phase → N phase → SA phase → SC phase on the high temperature side of its SC phase when the temperature is lowered (b) Either of the following: (c) having a phase sequence of I phase → SA phase → SC phase; or (d) having a phase sequence of ■ phase → SC phase. Although those having a certain series are used, the selection of (a) to (d) differs depending on the chiral dopant used at the same time. The most commonly used method is (a), in which the nematic property of the chiral dopant (when added to the SC matrix liquid crystal, N
If there is a strong tendency to widen the temperature range of the phase and narrow the temperature range of the SA phase, use (b) as a chiral dovan 1-
smectic A property (when added to SC matrix liquid crystal,
(c) when there is a strong tendency to widen the temperature range of the SA phase and narrow the temperature range of the N'' phase, or when the SC property is weak and the temperature range of the N1 phase or SA phase tends to be widened. It is most suitable to use (d).What is important is the phase series when it is an SC* liquid crystal composition, and for boat fishing, the phase series of I→N3→SA−+SC” is important. A phase series is advantageous in terms of orientation. On the other hand, depending on the orientation control method, the I−+N”→sc” phase series may also show better orientation, and since it is easier to obtain a large tilt angle, guest
It is suitable for host methods.

As the SC base liquid crystal used in the present invention, a composition consisting of a compound exhibiting an SC phase as conventionally used can be used, but in order to obtain faster response, the composition shown below can be used. is more preferable.

That is, (I) a composition (hereinafter referred to as medium-temperature liquid crystal) consisting of a compound having a two-ring structure and exhibiting an SC phase at a temperature close to room temperature, or a homolog thereof (a compound that differs only in the alkyl chain).
(■) A compound with a two-ring structure, few polar groups in the molecule, and low viscosity (hereinafter referred to as viscosity-reducing liquid crystal) is added to lower the viscosity, and (I[) viscosity-reducing liquid crystal is added. In order to increase the upper limit temperature of the SC phase, which has been lowered by
A composition (hereinafter referred to as
It is a composition made by adding high-temperature liquid crystal).

CI) Medium-temperature liquid crystal The medium-temperature liquid crystal used in the present invention is such that the liquid crystal compound constituting it is optically inactive, has a two-ring structure, and has an S
A compound exhibiting C phase or the number of carbon atoms in its alkyl chain,
It consists of homologs that differ only in shape, and at least one compound in the homologues has a
It is a compound that exhibits an SC phase, which may be monotropic, in a temperature range of C or higher.

Typical compounds used as medium-temperature liquid crystals are listed below. However, in the general formula shown below, R+
, Rt each independently represents an alkyl group having 1 to 18 carbon atoms.

(I a) (I b) (I C) (I d) (II) Reduced viscosity liquid crystal The reduced viscosity liquid crystal used in the present invention is a low viscosity liquid crystal compound or composition, and the constituent low viscosity compounds has a two-ring structure and does not exhibit an SC phase alone, but when added to a medium-temperature liquid crystal, it contributes to improving responsiveness.
At least one of both chains is an alkyl group, particularly preferably a compound in which both chains are an alkyl group, and the compound is characterized in that the number of ester bonds contained in the molecule is one or less.

Typical compounds used as viscosity-reducing liquid crystals are listed below. However, in the general formula shown below, R+,
Each Rz independently represents an alkyl group having 1 to 12 carbon atoms.

(■ b) (n-c) (■ d) (■ e) Among the above compounds, the formula (1
-a) and the compound represented by the formula (1-b) are preferred, and the compounds represented by the formula (I-a-1), the formula (1-a2), and the formula (I-a-5
), formula (1-a-6), formula (1-a-41), formula (1-
a-42) and compounds represented by formula (Tb-1) are particularly preferred. As the viscosity-reducing liquid crystal, compounds represented by formula (ff-a) and formula (TI-b) are preferred;
II-a-1), formula (II-a-6) and formula (I[-b
A compound represented by -1) is particularly preferred.

(III) High-temperature liquid crystal The high-temperature liquid crystal used in the present invention is an optically inactive compound having a three- or four-ring structure, or a composition thereof, and each compound is an S
The upper limit temperature of C phase (hereinafter abbreviated as Tc) is 50 to 6
When mixed at 10% in a composition at 0°C, its Tc is 2°
Preferably, at least two rings are aromatic rings (L4-phenylene, pyrimidine-2,5
-diylpyrazine-2,5-diyl, pyridine-2,5
- diyl or its fluorine-substituted product), and has a Tc of 90°C or higher and a SC phase temperature range of 1.5°C or higher, or a compound with an alkyl group in its side chain. They are homologs that differ in the number of carbon atoms or their shapes, and are particularly characterized by containing at least one compound represented by formula (A) above as a constituent element.

- Representative compounds represented by formula (A) and their phase transition temperatures are shown in Tables 1 to 3.

Table (Continued) Table (Continued) Table (Continued) (Continued) In the above table, Cr is crystalline phase, SA is smectic A phase, SB
is smectic B phase, SC is smectic C phase, S3.
34 and Ss each represent an unidentified smectic phase, N represents a nematic phase, and ■ represents an isotropic liquid phase.

Among the compounds represented by general formula (A), - formula (A-
The compound represented by 1) is effective because it does not cause other smectic phases to appear even at low temperatures. Further, in order to maintain a wide temperature range of the N phase, a compound represented by formula (A-3) is effective. The compounds represented by formulas (A-2) and (A-3) are excellent in terms of good compatibility with other liquid crystal compositions, lowering the melting point of the composition, and preventing precipitation of the compound.

The compounds represented by the above-mentioned formulas (A-1) to (A-3) are added to a liquid crystal composition (hereinafter referred to as base liquid crystal (A)) that exhibits an SC phase and is composed of the following two-ring pyrimidine compound. When added in weight%, all had the effect of increasing the Tc (upper limit temperature of the SC phase) by 2 to 4°C or more.

0CHz, CO3, SCO, CHz-Cth
The transition temperature (°C) of a liquid crystal composition that represents C3C-2 or a single bond and exhibits this SC phase is as follows.

As the high-temperature liquid crystal, a compound represented by the following general formula (D) can be used in combination with a compound represented by the above-mentioned formula (A).

Represents a hydrogen atom substituted with a fluorine atom, preferably,
X! and at least one of X2 is a single bond, and in the formula, R' and R' each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, and xl and =o-,-co.

Represents oco-, -s-, or a single bond, and Zl and also 1
This is the case where (φX) is represented.

SC containing the medium temperature range liquid crystal, reduced viscosity liquid crystal and high temperature liquid crystal
In the base liquid crystal, the blending ratio of medium temperature range liquid crystal is 1 to 90.
% by weight is preferred, and 5 to 75% by weight is particularly preferred. The blending ratio of the thinning liquid crystal is preferably 1 to 50% by weight, and 5 to 4% by weight.
Particularly preferred is 0% by weight. The blending ratio of high temperature liquid crystal is 1 to 7.
0% by weight is preferred, and 5-60% by weight is particularly preferred.

In the high temperature liquid crystal, the compound represented by formula (A) above is 1
It is preferably contained in an amount of 0% by weight or more, particularly 50% by weight or more.

/ Chiral dopants used in the present invention include (1) S
A compound exhibiting a C" phase, (2) a compound exhibiting only a liquid crystal phase other than the SC" phase, or (3) a compound exhibiting no liquid crystallinity at all can be used; however, in the case of (3), the SC matrix In order to prevent the tendency for the liquid crystallinity of the sc" liquid crystal composition obtained by adding it to liquid crystal to decrease, it is preferable to use a compound having a skeleton similar to that of liquid crystal.

Among the various physical properties that the chiral dopant brings to the S01 liquid crystal composition, the important ones are the helical pitch it induces, the direction and magnitude of spontaneous polarization, and these are determined by the optically active sites of each compound constituting the chiral dopant. most affected.

Typical optically active groups in optically active compounds that have been used as chiral dopants, SC2 compounds, or additives to nematic liquid crystals are listed below.

/ (■ CH3 (-C11□-)-i-CH-R3 C) +3 CI+-0-R5 CH3 II 0-C-CH-oR.

CH30 *11 0-C)I-C-0-R5 CI+, 0 Yu II CH-C-0-R5 CI(.

(TV-57) C.I. OCHz CHRs C1h OCHz CHCHI C0R5 CH3 0CI CH20COR5 C.I.

CH-CHz(CHz)rOCORs H3 CH2-CI-(CI2h-OCOR5 In each of the above formulas, m represents an integer of 1 to 4, n represents an integer of 1 to 10, and R3 has a carbon atom number of 3 to 8. R4 represents an alkyl group having 2 to 10 carbon atoms, R3 represents an alkyl group having 1 to 10 carbon atoms, and R
5 represents an alkyl group having 1 to 4 carbon atoms.

Optically active compounds containing only the optically active groups represented by formulas (IV-1) to (IV-22) as optically active groups exhibit spontaneous reaction induced when added to the SC base liquid crystal to form an S08 liquid crystal composition. Polarization is often small (sc"
Even when phases are shown, most of them are only 1 Onc/cm" or less.

On the other hand, as optically active groups, formulas (IV-31) to (■91
) Many of the optically active compounds containing the optically active group represented by () have a large spontaneous polarization induced when added to an SC base liquid crystal to form an S01 liquid crystal composition, and when exhibiting an SC1 phase alone, the spontaneous polarization is 300 nC. There are some that show large values of /cm'' or more.

Typical basic skeletons of optically active compounds having such an optically active group at the end are listed below.

■ ■ ■ In each of the above basic skeletons, the benzene ring or one-striped cyclohexane ring has a fluorine atom, a chlorine atom, a bromine atom, a methyl group, a methoxy group, a cyano group, or a nitro group (each substituted basic skeleton can also be used.

The optically active compound having the chiral group bonded to one or both sides of the basic skeleton as described above can be effectively used as a constituent component of a chiral dopant. In particular, the general formula (B) Ql-Z Ql" in which the chiral groups are bonded to both sides, Q" and Q" are mutually different optically active groups, and each optically active group has at least one asymmetric At least one of Q''' and Q'' has a carbon atom, and the asymmetric carbon atom is oxygen, iodine, nitrogen, fluorine,
It has a structure directly connected to chlorine or 10- or -C=-N. Z represents a structure in which any one or two hydrogen atoms on these rings are substituted with a fluorine atom or a cyan group; however, in a structure in which the above hydrogen atoms are substituted with a fluorine atom or a cyano group, and Y2 are each independently a single bond, -COO--OC
(1--CH20-1OCHg CHiCHz
--c = c --cos- or -5CO-, but a single bond, -COO--0CO--coto- or -
〇CHx- is preferable, and when m=1,
It is preferable that at least one of Yl and Y2 is a single bond. ) represents the central skeleton (core) part of a liquid crystal molecule. ] Optically active compounds represented by these are preferred.

- In the optically active compound represented by formula (B), especially at least one optically active group is defined by the above (IV-31).
It is desirable that it be any of the groups represented by -(IV-91).

As described above, the following points can be cited as advantages of using an optically active compound in which different chiral groups are bonded to both sides of the basic skeleton.

(1) It can exhibit stronger spontaneous polarization than a compound having a chiral group on only one side.

That is, a chiral group selected from the groups represented by (TV-31) to (IV-91) above and (IV-1) to (IV-2
A compound having a chiral group selected from the groups represented by 2) on both sides of the basic skeleton, and a compound having the same basic skeleton with a chiral group selected from the groups represented by (IV-31) to (■91) Compounds that have only one group and an achiral group on the other side are added to the SC matrix liquid crystal, and when the spontaneous polarization is determined as an extrapolated value, the compound that has chiral groups on both sides is 10 to 30 nC/ cm" or more. Since the spontaneous polarization derived from the groups represented by (IV-1) to (IV-22) is at most about 10 nC/cm2, it is larger than the simple sum of the spontaneous polarization due to the chiral groups on both sides. You can see that it is happening.

Furthermore, in a compound that is a group selected from the groups represented by (TV-31) to (IV-91) and has different chiral groups on both sides of the basic skeleton, the spontaneous polarization due to both chiral groups is Polar ((S)-2-methylbutyl b-decyloxybenzylidene aminophenyl cinnamate (DOBAMBC), a well-known ferroelectric liquid crystal)
The polarity of is determined as e. ), a very large spontaneous polarization can be obtained.

In this case, a larger spontaneous polarization of 100 nC/c+n2 or more can be obtained than the simple sum of the spontaneous polarizations due to the chiral groups on both sides.

As a chiral dopant, the larger the spontaneous polarization that can be induced, the smaller the amount of chiral dopant needed to be used.
The proportion of C matrix liquid crystal can be increased, and as a result, S
09 It becomes possible to lower the viscosity of the liquid crystal composition. as a result,
This leads to improved responsiveness.

(2) It is possible to adjust the helical pitch, such as compounds with very long helical pitches and compounds with very short helical pitches induced in the N'' phase or sc'' phase.

As mentioned above, in order to obtain good orientation, it is important that the helical pitch in the N'' phase or sc'' phase is long. It is only necessary that the helical pitch of the chiral dopant is adjusted as a whole, and this is not necessarily necessary for each individual compound, but it is easier to adjust the helical pitch if the main component of the chiral dopant has a somewhat longer helical pitch. It is. Further, in the case of a compound added primarily for the purpose of adjusting the helical pitch, the shorter the helical pitch, the more convenient the amount added can be suppressed.

In order to lengthen the helical pitch, the directions of the helical pitch due to the chiral groups on both sides should be opposite to each other, but (IV-31
) to (IV-91), it is preferable that the polarities of their spontaneous polarizations be the same.

(3) Particularly (IV-31) ~ which can show large spontaneous polarization
Chiral groups selected from the groups represented by (IV-91) obtained by chemical methods such as asymmetric synthesis and optical resolution often do not have 100% optical purity; It is quite difficult to purify these to 100%. However, (S) obtained from natural products
-When combined with a chiral group derived from 2-methylbutanol or a chiral group with extremely high optical purity such as those obtained by microbial engineering techniques, these become diastereomers, which can be easily separated by chromatography or recrystallization. Therefore, the optical purity can be brought close to 100%.

It is effective to use the compound of general formula (B) in an amount of 10% or more, preferably 30% or more, particularly preferably 50% or more as a constituent component of the chiral dopant.

Among the compounds of general formula (B), compounds having particularly preferable combinations of basic skeleton and chiral group are shown below.

In the above formula, R4 and R41 each independently represent an alkyl group having 2 to 10 carbon atoms, R7 and R5' each independently represent an alkyl group having 1 to 10 carbon atoms,
R7 is a linear alkyl group having 2 to 10 carbon atoms, a branched alkyl group having 3 to 10 carbon atoms, or an optically active group having at least one asymmetric carbon having 4 to 10 carbon atoms. represents an alkyl group, l represents an integer of 0 to 5,
Y is a single bond, -o-, -oco-, -coo-, or -
ocoo represents -, W is chlorine fluorine or -〇
CH3 is represented by Z'.

Xl and X4 each independently represent a hydrogen atom, a fluorine atom or a cyano group, Xl represents a hydrogen atom or XI,
X3 represents a hydrogen atom;

The above chiral dopant is present in the SC matrix liquid crystal at 1 to 60%.
It is appropriate to add it in a proportion of 2% by weight and use it as an SC* liquid crystal composition, but it is more preferable to add it in a proportion of 2 to 50% by weight. When the addition ratio of the chiral dopant is more than 60% by weight, the spontaneous polarization increases, but since the chiral dopant itself has a much higher viscosity than the base liquid crystal, the viscosity of the SC9 liquid crystal composition increases, resulting in high speed This is not preferable because it tends to adversely affect responsiveness. Further, an increase in the amount of chiral dopant added tends to shorten the helical pitch, which tends to adversely affect the orientation, which is not preferable. On the other hand, if the proportion of the chiral dopant added is less than 1% by weight, the spontaneous polarization becomes too small and high-speed response cannot be expected.

The spontaneous polarization value of the “sc” liquid crystal composition is 3 to 30 nC/c.
It is preferable to adjust the addition ratio of the chiral dopant so that it is in the range of m In the case of a chiral dopant that induces spontaneous polarization, the addition ratio of the chiral dopant is preferably in the range of 10 to 40% by weight, and 300nC/
In the case of a chiral dopant exhibiting strong spontaneous polarization of cm2 or more, the addition ratio of the chiral dopant is preferably in the range of 2 to 25% by weight. The more the spontaneous polarization induced by the chiral dopant becomes stronger, the more desirable its addition ratio decreases, but in the case of the chiral dopant made of the optically active compound exemplified, the addition ratio never falls below 1% by weight.

When the S01 liquid crystal composition of the present invention is cooled from an isotropic liquid state, it undergoes a phase transition from the N1 phase to the SA phase to the S01 phase. (hereinafter referred to as the N''-3A point), the N''' = SA
It is more preferable to use an SC" liquid crystal composition in which the pitch of the spiral appearing in the N9 phase up to one degree higher than the point is 3 μm or more, and the pitch of the spiral is 10 μm or more, and the N"-3A
Particularly preferred are SC" liquid crystal compositions in which the pitch of the helix increases divergently as the point approaches the point.

-Among the optically active compounds of formula (B), in compounds where the directions of the helices induced in the N'' phase by the chiral groups R1'' + R1'' on both sides are opposite to each other, the induced helical pitch is quite long. Therefore, when using such a compound as the main component of a chiral dopant, adjusting the helical pitch is often unnecessary or easy; however, for boat fishing, the helical pitch can be lengthened as follows. Can be adjusted.

N′″ of sc”liquid crystal composition containing multiple optically active compounds
The pitch P (μm) of the helix appearing in the phase is determined by Ci representing the concentration of each optically active substance and Pi representing the pitch of the helix per unit concentration of each optically active substance.
(μm) (Here, the right-handed spiral pitch is positive and the left-handed spiral pitch is negative.) Using this, SC
* P' at 5A-N'' point T0 of the liquid crystal composition is Pl・
When , Ci should be selected 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.

In reality, To changes depending on each Ci, but it can often be inferred fairly accurately from the change in the 5A-N" point when each optically active compound is added to the SC matrix liquid crystal at a concentration of ΣCi. If the value T.' differs greatly from the T. of the composition selected using it, the measurement may be performed again using T. instead of T0r.

The temperature range in which the SC “liquid crystal composition of the present invention exhibits the N” phase is as follows:
A range of 3 degrees or more and less than 30 degrees is preferable.

If the temperature range in which the N9 phase is exhibited is less than 3 degrees Celsius, the phase transition to the SA phase will occur immediately upon cooling down, which tends to make it difficult to fully align liquid crystal molecules in the N1 phase, which is not preferable. Furthermore, if the temperature range showing the N" phase is 30 degrees or higher, the clearing point of the SC* liquid crystal composition becomes high, which tends to have an adverse effect on workability in the process of filling the cell with liquid crystal material, etc. Undesirable.

A chiral dopant is one that tends to (1) expand the temperature range in which it exhibits the N'' phase when added to the SC matrix liquid crystal, regardless of whether the chiral dopant itself has liquid crystallinity or not, or (2) an N'' phase. Each has unique properties, such as those that tend to narrow the temperature range in which they exhibit a phase. S0 of the present invention
9. In order to adjust the temperature range in which the liquid crystal composition exhibits the N'' phase to the above-mentioned preferred range, in the case of (1), the SC base liquid crystal exhibits a narrow temperature range in which it exhibits the N phase, or it does not exhibit the N phase. S
A C base liquid crystal may be used, and in the case of (2), an SC base liquid crystal that exhibits an N phase over a wide temperature range may be used. This method can be applied not only to the N9 phase but also to the SA phase and the SC" phase. For example, the chiral dopant expands only the SA phase of the SC9 liquid crystal composition, and the N" phase and the SC* phase. When scaling down the SC phase, the upper limit temperature of the SC phase is high and the temperature range of the N phase is wide (,
In addition, it is sufficient to use one having a phase sequence of SC phase→N phase→■ phase, or one having a narrow SA phase temperature range and having a phase sequence of SC phase→SA phase→N phase→■ phase.

This tendency of chiral dopants can be seen in 5011, which is obtained by adding a certain amount of chiral dopants to the SC host liquid crystal.
By measuring the change in phase transition temperature of the liquid crystal composition,
It is easy to know. From this result, the temperature range in which each phase in the S01 liquid crystal composition exhibits, particularly the N'' phase, can be easily adjusted.

The chiral dopant used in the present invention is required to induce a certain level of spontaneous polarization (hereinafter abbreviated as P) by adding it to a certain amount of SC host liquid crystal.

As mentioned above, for the SC" liquid crystal composition, the amount of the chiral dopant to be added may be adjusted so that the value of P is in the range of 3 to 30 nC/cm2, especially near room temperature. However, if the chiral dopant is If the value of induced P is small, the amount added will be large relative to the SC base liquid crystal, and the viscosity of the S01 liquid crystal composition will increase accordingly, making it impossible to obtain high-speed response. Therefore, the chiral dopant used in the present invention is preferably one that can induce P of 1.OnC/am" or more when added to the SC base liquid crystal in an amount of 10% by weight; 0,5 nC7 when added
Particularly preferred are those that can induce P of cm2 or more.

〔Example〕

The present invention will be specifically explained below with reference to Examples, but the gist and scope of the present invention are not limited by these Examples. In addition, in the examples, "%" represents weight %. The phase transition temperature of the composition can also be measured using a polarizing microscope equipped with a temperature control stage and a differential scanning calorimeter (D
SC) was used in combination.

Example 1 As a medium-temperature range liquid crystal, from the compound represented by the formula (I-a-1), 12.4% 9.2% As a reduced viscosity liquid crystal, the compound represented by the formula (II-a-6) Therefore, as a high temperature liquid crystal of the formula, an SC matrix liquid crystal (hereinafter referred to as matrix liquid crystal (B)) consisting of 18.0% of the compound Ntl (A-3-1).

) was prepared.

The phase transition temperature of this base liquid crystal (B) was as follows.

39°C63°C74,5°C 3C,==nib5A4==2 When added to the base liquid crystal exhibiting 22-phase IN phase and SC phase, as a compound whose helical pitch induced in the N1 phase is right-handed. , the formula: this chiral dopant 20% and the above matrix liquid crystal (B) 80
A S08 liquid crystal composition was prepared consisting of %.

The phase transition temperature of this sc'' liquid crystal composition is as follows.

It is called the compound 1). )73% and the helical pitch induced in the N1 phase is left-handed, which is referred to as a compound of formula-1. ) A chiral dopant consisting of 27% was prepared.

This SC* liquid crystal composition did not crystallize even when left at low temperature (approximately 0°C) for a long time, and its melting point was not clear.

This SC9 liquid crystal composition was filled into a cell with a thickness of approximately 2 μm consisting of two glass transparent electrodes subjected to alignment treatment by polyimide coating and rubbing, and an isotropic liquid (1) was formed.
The phase was slowly cooled to room temperature. The orientation was good and a uniform SCI phase monodomain was obtained.

When a rectangular wave of 50 Hz and an electric field strength of 10 VP/μm was applied to this cell and its electro-optical response speed was measured, a high-speed response of 45 μsec at 25° C. was confirmed.

The spontaneous polarization at this time is 12.4 nC7cm2,
The tilt angle was 18.5°, and the contrast was very good.

Example 2 A compound in which the helical pinch induced in the N'' phase is right-handed when added to a parent liquid crystal exhibiting an N phase and an SC phase,
A chiral dopant consisting of 32.5% of the compound of formula (R-1) used in Example 1 and 67.5% of the compound of formula (R-1) as a compound whose helical pinch induced in the N'' phase is left-handed was prepared.

20.1% of this chiral dopant and the mother liquid crystal (A)
54.4%, and as a reduced viscosity liquid crystal, the formula (If-
8.0% of the compound represented by a-1), and 17.5% of the compound of the formula (A-3-2) as high temperature liquid crystal.
An S01 liquid crystal composition was prepared.

This S04 liquid crystal composition exhibited an sc'' phase at temperatures below 62°C.

The electro-optical response speed measured in the same manner as in Example 1 was 25
The time was 55 μsec at °C.

Example 3 Formula (A3-2) used as high temperature liquid crystal in Example 2
An S, C'' liquid crystal composition was prepared in the same manner as in Example 2 except that the compound of formula (A-1-10) was used in place of the compound of formula (A-1-10).

This 5011 liquid crystal composition exhibited a 5011 phase at temperatures below 60°C, and the electro-optic response speed measured in the same manner as in Example 1 was 53 μsec at 25°C.

〔Effect of the invention〕

The ferroelectric liquid crystal composition of the present invention is a liquid crystal material that has excellent alignment properties and high-speed response, and can operate 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 liquid crystal devices using ferroelectric smectic liquid crystals.

Claims (1)

[Claims] 1. A ferroelectric liquid crystal composition obtained by adding a chiral dopant made of an optically active compound to a liquid crystal composition containing a medium temperature range liquid crystal, a reduced viscosity liquid crystal, and a high temperature liquid crystal and exhibiting a smectic C phase. The high temperature liquid crystal has the general formula (A) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R^a and R^b each independently represent the number of carbon atoms, 1
~ 18 linear or branched alkyl or alkoxyl groups, ▲ has mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ has mathematical formulas, chemical formulas, tables, etc. ▼ each independently represents ▲ mathematical formulas, chemical formulas, tables, etc. ▼ or its fluorine-substituted product, but at least one of ▲ has mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ has mathematical formulas, chemical formulas, tables, etc. ▼ ▲ has mathematical formulas, chemical formulas, tables, etc. ▼ represent. ) A ferroelectric liquid crystal composition exhibiting a chiral smectic C phase in a wide temperature range including room temperature. 2. The ferroelectric liquid crystal composition according to claim 1, wherein ▲There are mathematical formulas, chemical formulas, tables, etc.▼ is ▲There are mathematical formulas, chemical formulas, tables, etc.▼. 3. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and R^ 3. The ferroelectric liquid crystal composition according to claim 2, wherein a is a linear or branched alkoxyl group having 1 to 18 carbon atoms. 4. A claim in which ▲There are mathematical formulas, chemical formulas, tables, etc.▼ is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and R^a is a linear or branched alkyl group having 1 to 18 carbon atoms. 2. The ferroelectric liquid crystal composition according to 2. 5. The chiral dopant has the general formula (B) Q^1^*-Z-Q^2^* [In the formula, Q^1^* and Q^2^* are different optically active groups, and each The optically active group has at least one asymmetric carbon atom, and in at least one of Q^1^* and Q^2^*, the asymmetric carbon atom is oxygen, sulfur, nitrogen, or fluorine. , chlorine or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or has a structure directly connected to -C≡N. Z
is a general formula (C) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲Mathematical formulas,
There are chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ are each independently ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ , ▲ Mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
or represents a structure in which any one or two hydrogen atoms on these rings are substituted with a fluorine atom or a cyano group, and Y^1 and Y^2 each independently represent a single bond, -COO-, -OCO- , -CH_
2O-, -OCH_2-, -CH_2CH_2-, -C
≡C-, -COS- or -SCO-, and m represents 0 or 1. ) represents the central skeleton (core) part of a liquid crystal molecule. ] Claims 1, 2, containing an optically active compound represented by
5. The ferroelectric liquid crystal composition according to 3 or 4.