JPS6281483A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:To provide a liq. crystal compsn. which has a large spontaneous polarization value and a long spiral pitch and which comprises a smectic C* liq. crystal having an ester bond, a particular chiral substance, a thinner and a transition temp. elevating agent. CONSTITUTION:To a smectic C* liq. crystal (A) having an ester bond of formula I (wherein m is an integer of 1<=m; l is an integer of l<=2; R1-R2 are each an alkyl or alkenyl, provided that either of them have an asymmetric carbon atom; this compound is required to be optically active) are added 0.1-20wt% chiral substance (B) of formula II (wherein m is an integer of 6<=m<=14; l is an integer of 1<=l<=5; * is an asymmetric carbon; this compd. is required to be optically active), 1-80wt% thinner (C) of formula III (wherein m is an integer of 4<=m; and m' is an integer of m'<=14) and 0.1-50wt% transition temp. elevat ing agent (D) of formula IV (wherein R1-R2 are each a 4-14C alkyl). This leads to a liq. crystal compsn. having a high upper limit temp. of smectic C* liq. crystal phase.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a liquid crystal composition having a smectic C liquid crystal.

[Prior Art and its Problems] In recent years, high-speed optical switching devices that utilize smectic liquid crystals, especially smectic C* (hereinafter abbreviated as "SmC") liquid crystal phases characterized by twisted alignment, and that take advantage of their ferroelectric properties, have attracted attention. are collecting.

Compounds with an ester structure, such as DOBAMBC, are used as SmC" liquid crystals, but conventional
mC" liquid crystal has a spontaneous polarization (Ps) value of several nC/crn'
It was small. Generally, response time τ is determined by the following formula.

τ-η/(E·Ps) (E: electric field, η: liquid crystal viscosity) Therefore, the larger the Ps value, the faster the response speed.

In order to increase the Ps value, attempts have been made to create a liquid crystal composition by adding a chiral substance to SmC" liquid crystal, but
Conventional chiral substances have a weak Ps-increasing effect, and a satisfactory liquid crystal composition has not yet been obtained.

In addition, conventional "SmC" liquid crystals generally have a short torsional pinch, and most of them are less than I pLm, so it is necessary to make the cell camp sufficiently thin, for example, l pmm. It is technically extremely difficult to form cell gear amplifiers over a wide area, and it is accompanied by difficulties in the production of liquid crystal elements.

On the other hand, when used in high-temperature environments such as in automobiles, conventional SmC" liquid crystals are
Sometimes it could not be used because ff1 was low. Also,
The limit temperature of the SmC phase tends to decrease when chiral substances are added to increase the Ps value. For this reason, when a chiral substance is added, it may be disadvantageous for applications requiring high-temperature operation.

“Object of the invention” The object of the present invention is to solve the problems of the prior art described in 1-1 and
The s value is larger, the twist pitch is longer, and SmC
``The purpose of this invention is to provide a liquid crystal composition that can maintain a sufficiently high phase temperature limit.''

"Structure of the Invention" The liquid crystal composition of the present invention comprises a main ingredient consisting of a smectic C8 liquid crystal having an ester bond, a chiral substance represented by the following general formula [1], and a thin liquid crystal composition represented by the following general formula [2]. agent and the transition temperature represented by the following general formula [3]”-■
It is characterized by containing an agent.

(However, in the formula, m and fL are integers, and 6≦m≦1
4. It is in the range of 1≦cross≦5. Additionally, wood exhibits asymmetric carbon, and this compound is required to be optically active. ) (However, in the formula, m and m' are integers, and 4≦m,
It is in the range of m°≦14. ) (However, in the formula, R1 and R2 are alkyl groups having 4 to 14 carbon atoms.) In the present invention, the chiral substance represented by the general formula [1] in Section 111 is a compound in which oxygen is directly bonded to an asymmetric carbon. Therefore, it has high optical rotation. In addition, the central skeleton is a liquid crystal skeleton and has a biphenyl structure, and an asymmetric carbon indicated by a wooden seal that exhibits optical rotation is placed near the center, and an alkyl chain is placed at the end. It itself has liquid crystallinity, and when added to SmC'' liquid crystal, the liquid crystallinity does not deteriorate.

The chiral substance represented by the general formula [1] can be synthesized, for example, according to the following synthetic route.

(a) Synthesis of n-CmH2m, 10$C0OH (4'
-n-flukoxybiphenylcarboxylic acid) commercially available nCm
After refluxing R2m, 18 CN (4'-n-alkoxy 4-cyanobiphenyl) with potassium hydroxide in diethylene glycol, the reaction solution is added to a mixed solvent of methanol and concentrated hydrochloric acid = 2:1 and stirred. The formed crystals are filtered and recrystallized from ethanol.

(b) n Cm82m+10be◇←CxC0C1(7
) Synthesis (Acid chloride of (a) above) After refluxing the compound of (a) above with thionyl chloride,
Excess thionyl chloride is distilled off.

(C) Synthesis of the compound of general formula (1) A mixed solution of commercially available optically active 2-alkyl alcohol H CH3CM (CH2), CH3 and three equivalents of pyridine and toluene is heated and stirred, and the above compound (b) is added to the mixture. Gradually add an equivalent amount of

Thereafter, general acid-alkaline water washing is performed, toluene is distilled off, and the target product is recrystallized from ethanol.

In this way, the compound represented by the general formula [1] can be synthesized.

On the other hand, since the thinner represented by the general formula When added, the twisted structure is relaxed and the pitch can be expected to become longer as the amount added increases. Moreover, this thinner is excellent in that it does not have negative effects such as significantly changing other physical properties.

In addition, the transition temperature external cutting represented by the above general formula [3] has the effect of increasing the upper limit temperature of the Sac'' phase, and therefore can be made suitable for use under high temperature conditions. , this transition temperature agent A may be a 5rsC liquid crystal compound in which R1 and R2 do not have an asymmetric carbon in the general formula (3), or at least one of R1 and R2 has an asymmetric carbon. and optically active 5Llc”
It may also be a liquid crystal compound.

Further, the main material made of Sac" liquid crystal having an ester bond is not particularly limited, but for example, the following general formula
One or more of the compounds shown are preferably used.

(However, in the formula, ■ and s are positive integers, preferably 1≦
tn, l≦2, R, and R2 are alkyl or alkoxy groups, at least one of which has an asymmetric carbon, and the compound is required to be optically active. ) Among these, those represented by the following general formulas (〇) and (■) are particularly preferred.

(However, in the formula, n = an integer of 5 to 1O.) (However, in the formula, n = an integer of 4 to 12.) In the present invention, a main material consisting of a smectic C8 liquid crystal having an ester bond; A chiral substance represented by general formula [1],
The blending ratio of the thinner represented by the general formula [2] and the transition temperature outer cutting represented by the general formula [3] is not particularly limited, but for example, 0.1 to 20% chiral substance, the thinner 1
~80% by weight (more preferably 10-50% by weight),
It is preferable that the 91 agent is 0.1 to 50% by weight based on the transition temperature, and the remainder is the main agent. In this case, if the blending ratio of the chiral substance is less than 0.1% by weight, Ps(f4
is too small and there is a tendency for insufficient response to be obtained.
If the amount of the chiral substance is more than 20% by weight, a problem arises in that the twist pitch of the liquid crystal becomes too small, making cell production -1- difficult. In addition, if the blending amount of the eyelid agent is less than 1 mold part%, the twist pitch of the liquid crystal becomes too small, causing difficulties in cell manufacturing.If the blending amount of the thinning agent is greater than 80 heavy foil. The problem arises that the Ps value becomes small. Furthermore, if the content of agent A is less than 0% by weight on the transition temperature, the effect of increasing the critical temperature of the SmC phase will be weakened, and if the content of transition temperature increasing agent M is more than 50% by weight or 11%. The problem arises that the lower limit temperature of the SmC'' phase becomes high, making it unsuitable for use at room temperature.

"Examples of the Invention" Comparative Example 1 A compound represented by the following structural formula ■' (hereinafter abbreviated as compound A) and a compound represented by the following structural formula
(abbreviated as Compound B) were mixed at a ratio of 476.8/2 to prepare a liquid crystal composition. Further, a liquid crystal composition was obtained by further mixing a compound represented by the following structural formula (1) (hereinafter abbreviated as compound C) to the mixture of -1-compound A and the above-mentioned compound B. The mixture of Compound A and Compound C constitutes an example of the main ingredient in the present invention, and Compound C constitutes an example of the chiral substance in the present invention.

Maximum Ps value (nC/cm') of these liquid crystal compositions,
SmC8 temperature range ('O), twisting pinch (end 111)
The results of filling are shown in Table 1 (described later).

From this result, Ps
It can be seen that the value increases and the temperature range of Sac'' widens in the low temperature range.However, in all of these liquid crystal compositions, the twist pitch is short.Also, when the chiral substance of compound C is added As a result, the 1=limit temperature of the SmC'' phase becomes low, which is found to be disadvantageous for use under high temperature conditions.

Comparative Example 2 Main ingredient consisting of the compound A and the compound B (A/B=
4/8), 10 chiral substances consisting of the compound C
% by weight, and further added a compound represented by the following structural formula ■° (hereinafter abbreviated as compound) to obtain a liquid crystal composition. Note that this compound is an example of a thinner in the present invention.

(p-n-octyloxybenzoic acid p-octyloxyphenol ester) 10.
20.30. Liquid crystal compositions containing 50% by weight were prepared, and for these liquid crystal compositions, the maximum Ps value (commitment/Cm'), SmC' temperature range (℃), and twist pitch (pm) were determined at 711 constants. The results are shown in Table 2 (described later).

From this result, a liquid crystal composition with a large Ps value and a long twist pitch can be obtained by adding the chiral substance of Compound C to the main ingredient consisting of Compound A and Compound B, and further adding a thinning agent of Compound R. I understand. In addition,
The larger the amount of the compound added, the longer the twist pitch becomes. However, in all of these liquid crystal compositions, the -I; limit temperature of the SmC'' phase is low, making them unsuitable for use under high-temperature conditions.

Example 1 Base agent consisting of the compound A and the compound B (A/B=
4/6), 10 chiral substances consisting of the compound C
% by weight, and further a thinner consisting of the above compound 4
0 weight was added, and in addition to this, 0.1O1 of the compound represented by the structural formula (1) (hereinafter abbreviated as compound E) was added.
A liquid crystal composition was obtained by adding 24.50% by weight of Compound E (no base agent was used when Compound E was 50% by weight). Note that Compound E is an example of a transition temperature increasing agent in the wood invention.

((+)-p-2-methylbutoxyphenylbenzoicmp
”-hexyloxyphenol ester) For these liquid crystal compositions, the maximum Ps value (nC/cm
'), ,SmC'' temperature range (℃), twist pitch (
J-11) is shown in Table 3 (described later).

From Table 3, it can be seen that the upper limit temperature of the SmC' phase increases with the addition of acid as the transition temperature increasing agent of compound E. In addition, when 50% by weight of compound E is added, the upper limit temperature of the SmC' phase increases. The lower limit temperature rises to 28° C., resulting in a noticeable negative change in characteristics, but if the amount added is less than that, the lower limit temperature of the SmC'' phase does not change much. It is also seen that addition of compound E does not have any adverse effect on the Ps value or twist pitch. Therefore, the above liquid crystal composition to which Compound E is added,
It can be said that it is suitable for use under high temperature conditions.

The liquid crystal composition described in 1-2 containing compound E was applied to an LCD cell in which an alignment film made of polyimide was formed on the inner surface of one substrate, an alignment film made of aminosilane was formed on the inner surface of the other substrate, and the cell gap was set to 2 pL11. When implanted, all showed good uniform orientation.

Example 2 Instead of compound E used in Example 1, the following structural formula -
The compound represented by 2 (hereinafter abbreviated as compound F) is
A liquid crystal composition was obtained in the same manner as in Example 1, except that 4% by weight was added.

((+)-p-2-methylbutoxyphenylbenzoic acid p
'-Desyloxyphenol ester) In addition, in place of Compound E used in Example 1, 24% by weight of a compound represented by the following structural formula ■-3 (hereinafter abbreviated as Compound G) was added. A liquid crystal composition was obtained in the same manner as in Example 1.

(D)-p-octyloxyphenylbenzoic acid p°-2-
Methylbutyroxyphenol ester) Also in these liquid crystal compositions, the same effect of increasing the upper limit temperature of the 5yaC main phase as in Example 1 was obtained by adding Compound F and Compound G, which serve as transition temperature increasing agents. .

Example 3 Instead of compound E used in Example 1, the following structural formula -
The compound represented by 4 (hereinafter abbreviated as compound H) is converted into 2
A liquid crystal composition was obtained in the same manner as in Example 1, except that 4% by weight was added.

(p-Octyloxyphenylbenzoic acid p°-octyloxyphenol ester) Also, in place of Compound E used in Example 1, a compound represented by the following structural formula ■-5 (hereinafter abbreviated as Compound I) was used. A liquid crystal composition was obtained in the same manner as in Example 1, except that 24% by weight of .

(p-hexyloxyphenylbenzoic acid P'-7' siloxyphenol ester) Maximum Ps value (nC/crn') of these liquid crystal compositions,
The results of measuring the Sac'' temperature range (°C) and twist pitch (#Ls) are shown in Table 4 (described later), and it can be seen that the upper limit temperature of the !lfmc'' phase is high in both cases.

Furthermore, when these liquid crystal compositions were injected into LCD cells similar to those in Example 1, all exhibited good uniform alignment.

(Hereinafter, blank spaces) Table 1 Table 2 Table 3 Table 4 "Effects of the Invention" As explained above, according to the present invention, the general formula [1 ] A chiral substance represented by the general formula [2], a thinner represented by the general formula [3], and a transition temperature -1- represented by the general formula [3]
By adding the outer cutting, it is possible to obtain a Sac liquid crystal composition having a large Ps value, a long twist pitch, and a high upper limit temperature of the 5IIIC phase.

Claims (2)

[Claims] (1) A main agent consisting of a smectic C^* liquid crystal having an ester bond, a chiral substance represented by the following general formula [1], a thinner represented by the following general formula [2], and a thinner represented by the following general formula [3]. A liquid crystal composition comprising the following transition temperature increasing agent. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・[1] (However, in the formula, m and l are integers, and 6≦m≦14,
It is in the range of 1≦l≦5. In addition, * indicates an asymmetric carbon,
This compound is required to be optically active. ) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・[2] (However, in the formula, m and m' are integers, and 4≦m, m'
It is in the range of ≦14. ) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・[3] (However, in the formula, R_1 and R_2 are alkyl groups with 4 to 14 carbon atoms.) (2) In claim 1, the base material made of smectic C^* liquid crystal having an ester bond is
A liquid crystal composition which is a compound represented by the following general formula [4]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・［4］ (However, in the formula, m and l are positive integers, 1≦m, l≦2
R_1 and R_2 are alkyl or alkoxy groups, at least one of which has an asymmetric carbon, and this compound is required to be optically active. )