JP2001072973A - Antiferroelectric liquid crystal composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal composition which can form a liquid crystal display element with a good low-temperature responsivity. SOLUTION: The titled antiferroelectric liquid crystal composition contains a base liquid crystal and a liquid crystal compound and is prepared by adding the liquid crystal compound to the base liquid crystal so that the ratio of an αobtained by using this composition to an α obtained by using only the base liquid crystal is 0.8 or lower, α being the inclination of Arrhenius plot in the temperature range lower than TAF-35 deg.C and TAF being the upper limit temperature of the transition from an antiferroelectric phase to another phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention has a small temperature dependence of response time, and can respond at high speed near room temperature.
Further, the present invention relates to a liquid crystal composition capable of forming a liquid crystal element having a wide operating temperature range.

[0002]

2. Description of the Related Art At present, display devices using liquid crystal compounds are:
From the viewpoints of low voltage driveability, low power consumption, and small size and thickness, they are used not only in watches and calculators but also in a wide range of fields such as OA equipment such as word processors and personal computers, and car navigation systems.

[0003] A liquid crystal display element generally widely used for such purposes utilizes a nematic phase.
Such a liquid crystal display element is usually provided with a TN (Twisted Nemati).
c) Drive in mode or STN (Super Twisted Nematic) mode.

[0004] However, the TN mode liquid crystal display element has a drawback that the drive margin becomes narrower as the number of scanning lines increases and a sufficient contrast cannot be obtained. Therefore, it is difficult to manufacture a large-sized display element using the TN mode. The use in the STN mode has been developed to improve the liquid crystal display element driven in the TN mode.
As the number of lines increases, the contrast decreases and the response time increases. At present, the display capacity of about 800 x 1024 lines is the limit.

On the other hand, a ferroelectric liquid crystal or an antiferroelectric liquid crystal changes the orientation of liquid crystal molecules due to the direct interaction between the spontaneous polarization (Ps) of the liquid crystal molecules and the electric field (E). Is the effective energy ("driving force"). Therefore, in the display element using these liquid crystals, a high-speed response in which the time required for the switching drive is reduced to the order of μ seconds can be realized.

[0006]

However, the following problems have been pointed out in display devices using ferroelectric liquid crystals.

The first is an afterimage phenomenon (switching failure) caused by spontaneous polarization. In other words, when an attempt is made to display using two uniform states, it is necessary to orient the dipole between the substrates of the cell and hold it for a certain period of time.
The internal electric field due to the polarization of the charge generated during this time prevents switching to another uniform state.

The second problem is poor stability against mechanical shock. Since a smectic liquid crystal is a one-dimensional crystal having a layer structure, unlike a nematic liquid crystal, it is basically difficult to repair a once-disordered orientation. In addition, it has been recognized that there are inherent problems such as a liquid crystal layer having a bent chevron structure and a twisted structure in which molecules are twisted in the cell, and high contrast and memory properties cannot be obtained. .

On the other hand, the antiferroelectric liquid crystal used for the display element has a double hysteresis characteristic and a stable alignment characteristic suitable for simple matrix driving. The operation mode of this liquid crystal is electric field induced phase transition switching.
When the electric field is zero, spontaneous polarization is zero because adjacent molecules adopt an antiferroelectric state in which dipoles are oriented in opposite directions to each other, and dipole moments cancel each other. When a voltage higher than a certain threshold is applied to such an antiferroelectric liquid crystal display element, two ferroelectric states are induced according to the polarity of the electric field. Therefore, the antiferroelectric liquid crystal can take three stable states of an antiferroelectric phase and two ferroelectric phases, and the tristable state switching by the electric field performed between these three states is antiferroelectric. It shows double hysteresis peculiar to dielectric properties and steep threshold characteristics.

In order to use such an antiferroelectric liquid crystal in a display device, it is necessary to optimize material characteristics such as an operating temperature range, a response time, and a display contrast. It is difficult to satisfy all of these characteristics with a single liquid crystal, and it is usually prepared by blending several types of liquid crystals.

However, when such an antiferroelectric liquid crystal display device is actually used, it is necessary to improve the response time on the low temperature side. That is, in such an antiferroelectric liquid crystal display element, a heater is attached in order to keep the inside of the display device at a certain temperature or higher, for example, because the response time on the low temperature side is not yet sufficient for displaying moving images. Ingenuity has been made.

The reason why the response time at the low temperature side of such an antiferroelectric liquid crystal display element is delayed is considered to be a phase transition and a viscosity increase. As a phase transition at low temperature, the presence of SmI _A ^* phase has been pointed out. Takanishi et a liquid crystal compound of the following formula has been reported to have SmI _A ^* phase (Takanishi et al., 22nd LCD Symposium Proceedings p.
313 (1996)).

[0013]

Embedded image

Here, the SmI _A ^* phase is an antiferroelectric phase in which the direction of molecules is reversed for each layer, like the SmC _A ^* phase. This SmI _A
X-ray diffraction has confirmed that the ^* phase has an optical apparent tilt angle that is almost the same as the low-temperature side of the SmC _A ^* phase, but the layer spacing is longer than that of the SmA phase (Y. Ta
kanishi et al. Ferroelectrics 149 135 (1993)).
Further, the SmI _A ^* phase has a hex tick order, it has been reported that the correlation length representing the degree of order within the layer becomes longer.

From the above, it is speculated that the response time on the low-temperature side is delayed because the viscosity of the liquid crystal molecules increases due to an increase in the orientational order of the liquid crystal molecules in the layer, and the liquid crystal molecules become difficult to move. it can.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems associated with the prior art, and particularly provides a liquid crystal composition capable of forming a liquid crystal display device having good low-temperature response. It is intended to be.

More specifically, the present invention provides a liquid crystal composition which has a small temperature dependence of response time, can respond at high speed near room temperature, and can form a liquid crystal element having a wide operating temperature range. It is intended to be.

[0018]

SUMMARY OF THE INVENTION The antiferroelectric liquid crystal composition of the present invention is an antiferroelectric liquid crystal composition containing a base liquid crystal and a liquid crystal compound, wherein a transition from an antiferroelectric phase to another phase is performed. The upper limit temperature is T _AF (when the other phase is a smectic A phase,
T _AF is equal to T _AC . Here, T _AC is the phase transition temperature between the smectic A phase and the smectic C phase), and the composition is used at a slope α of the Arrhenius plot in a temperature range of T _AF -35 (° C.) or less. A liquid crystal compound is added to the base liquid crystal such that the obtained α value is 0.8 or less of the α value when only the base liquid crystal is used.

The antiferroelectric composition preferably contains the above composition in an amount of 10 mol% to 60 mol%. Further, it is preferable that the base liquid crystal contains at least one compound selected from the group of compounds represented by the following formula [I].

[0020]

Embedded image

[Wherein, in the formula [I], R ¹ is ^one group selected from the group consisting of an alkyl group having 3 to 16 carbon atoms or a polyfluoroalkyl group (provided that R ¹ is One or two or more non-adjacent —CH ₂ — groups or —CF ₂ — groups may be replaced by —O— groups), X ¹ is a —O— group, —COO -Represents a group or a single bond, wherein A ¹ and B ¹ are each independently

[0022]

Embedded image

A group selected from the group consisting of
^{1 *} represents 4 to 20 carbon atoms having at least one asymmetric carbon
(A hydrogen atom bonded to a carbon atom constituting the optically active group may be replaced by a halogen atom). Further, in the base liquid crystal, R ¹ is H (CH ₂ ) _p O (CH ₂ ) _q
It is preferable that p is an integer of 1 to 3 and q is an integer of 6 to 14.

In the base liquid crystal, X ¹ is -COO-
It is preferably a group. In addition, the temperature dependence of the layer spacing during the phase transition between the smectic A phase and the smectic C phase of the smectic layer of the liquid crystal compound is expressed by the following formula [II], and T _AC -30 ( ℃) to T _AC −
In 10 (° C.) temperature range (T _AC is the phase transition temperature of the smectic A phase and smectic C phase), that the differential value of the change in the layer spacing of the said phase transition is a liquid crystal compound is a value greater than zero preferable.

[0025]

(Equation 2)

[In the above formula [II], L _SA represents the layer spacing in the smectic A phase, and L _SC represents the layer spacing in the chiral smectic C phase (including the ferroelectric phase or the antiferroelectric phase). .

Further, in the above antiferroelectric liquid crystal composition, a liquid crystal compound having the above-mentioned properties is contained in an amount of 10 mol% to 60 mol%.
Is preferably contained in an amount of Further, it is preferable that the liquid crystal compound is at least one compound selected from the group of compounds represented by the following formula [III].

[0028]

Embedded image

In the above formula [III], R ² represents an alkyl group having 1 to 16 carbon atoms or a polyfluoroalkyl group (provided that one or two non-adjacent groups are present in these groups) The above-mentioned —CH ₂ — group or —CF ₂ — group may be replaced by —O— group), A ² and B ² are each independently

[0030]

Embedded image

Represents a group selected from the group consisting of the following groups (however, the same group is not selected at the same time), and R ^{2 *} is an optically active group having 4 to 20 carbon atoms having at least one asymmetric carbon. A hydrogen atom bonded to a carbon atom constituting the optically active group may be replaced by a halogen atom), and X ²
Represents a -O- group, -COO- or a single bond, and Y ^{1 to} Y
⁴ is a group independently selected from the group consisting of H and F, and any one of Y ^{1 to} Y ⁴ is always F
Is].

Further, R ^{1 *} and R ^{2 *} in the above formulas [I] and [III] are

[0033]

Embedded image

(Where k is an integer of 2 to 5, m is 1 to 3)
And n is an integer of 2 to 8). According to the liquid crystal composition and the liquid crystal element using the same according to the present invention, the temperature dependence of the response time is monotonous, so that the response time near room temperature can be increased, and the operating temperature range is reduced. Various devices having excellent characteristics such as wide characteristics can be obtained.

[0035]

DETAILED DESCRIPTION OF THE INVENTION The antiferroelectric liquid crystal composition according to the present invention will be specifically described. First, the antiferroelectric liquid crystal composition of the present invention is an antiferroelectric liquid crystal composition containing a base liquid crystal and a liquid crystal compound.

In general, many liquid crystals exhibit temperature dependence such that the responsiveness of the phase transition deteriorates when the ambient temperature decreases. More specifically, in many liquid crystals, the response (speed, 1 / tr) of the electric-field-induced phase transition at a temperature between the temperature T _AF and a predetermined temperature, and the response of the electric-field-induced phase transition below this predetermined temperature. Responsiveness is significantly different. For example, 1 / tr
Taking an Arrhenius plot for −1000 / T gives
As shown in FIG. 1, the ratio between the change (slope) of the electric field-induced phase transition speed between the temperature T _AF and the predetermined temperature and the change (slope) of the electric field-induced phase transition speed below the predetermined temperature is: 1
Significantly larger than

This leads to a decrease in the response speed of the liquid crystal compound regarding the electric field-induced phase transition in a low temperature region. Therefore, it is preferable that the temperature dependence of the liquid crystal is low, that is, the value of the change (gradient) of the electric field-induced phase transition rate at a predetermined temperature or lower is small. It is possible to suppress a decrease in response speed related to metastasis.

As a result of extensive studies, the present inventors have found that the above-mentioned general liquid crystal compound is used as a base liquid crystal, that is, a host liquid crystal, and a liquid crystal compound having predetermined properties is added thereto to form a composition. It has been found that a liquid crystal composition having improved temperature dependence of the host liquid crystal in a low temperature region can be provided.

Accordingly, the antiferroelectric liquid crystal composition according to the present invention has a maximum temperature at which a transition is made from an antiferroelectric phase to another phase.
_{When AF} is used, the value α _B obtained by using the composition in the slope α of the Arrhenius plot in a temperature range of less than T _AF -35 (° C.) is obtained when only the base liquid crystal is used. is 0.8 or less percentage of values alpha _H, namely α _B / α _H is 0.8 or less, preferably 0.7 or less,
It is more preferably 0.6 or less.

In the present invention, it is important that the α _H value of the host liquid crystal and the α _B value of the liquid crystal composition obtained by adding a predetermined liquid crystal compound to the host liquid crystal have the above-mentioned relationship. In addition, when such a relationship is established, the liquid crystal compound has improved temperature dependence even in a low-temperature region where the response of the host liquid crystal deteriorates, so that good response can be obtained. Can be

Here, the liquid crystal composition of the present invention contains a base liquid crystal having general properties as described below as a host liquid crystal and a liquid crystal compound having the following specific properties as a guest liquid crystal. Is what you do.

That is, in such a guest liquid crystal, the temperature dependence of the layer interval during the phase transition between the smectic A phase and the smectic C phase of the smectic layer is expressed by the following formula [I
I], and the change in the layer spacing related to the phase transition is in a temperature range (T _AC -30 (° C.) to T _AC -10 (° C.).
_AC is a liquid crystal compound in which the differential value of the change in the layer interval related to the phase transition is greater than 0 at the phase transition temperature of the smectic A phase and the smectic C phase.

[0043]

(Equation 3)

In the above formula [II], L _SA represents a layer spacing in a smectic A phase, and L _SC represents a layer spacing in a chiral smectic C phase (including a ferroelectric phase or an antiferroelectric phase). .

The term "temperature dependence of the layer spacing" refers to a phenomenon in which the layer spacing changes when the smectic layer undergoes a phase transition between the smectic A phase and the smectic C phase. This is because, in the smectic A phase, the liquid crystal molecules are oriented such that the long axis is perpendicular to the layer, whereas in the smectic C phase, the liquid crystal molecules are oriented such that the long axis is inclined from the normal direction of the layer. This is a phenomenon caused by a phase transition between two phases having different layer intervals.

The base liquid crystal used in the present invention contains at least one compound selected from the group of compounds represented by the following formula [I].

[0047]

Embedded image

[However, in the formula [I], R ¹ is a group selected from the group consisting of an alkyl group having 3 to 16 carbon atoms or a polyfluoroalkyl group (provided that 1 Or two or more non-adjacent -C
The H ₂ — group, or the —CF ₂ — group may be replaced by an —O— group).

[0049] where, if R ¹ is an alkyl group having 3 to 16 carbon atoms, the alkyl group, linear or may be in any form of branched and alicyclic but, R ¹ Is a straight-chain alkyl group, the compound has a straight and rigid structure, and thus exhibits excellent liquid crystal properties. Specific examples of such linear alkyl groups include hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tetradecyl, hexadecyl and octadecyl. Can be.

Examples of the polyfluoroalkyl group in which R ¹ has 3 to 16 carbon atoms include groups in which some or all of the hydrogen atoms of the above-mentioned alkyl groups have been substituted with F atoms. Can be.

Further, as an alkyl group in which one or two or more non-adjacent —CH ₂ — groups or —CF ₂ — groups present in those groups are replaced by —O— groups, Ten-
Examples include a methoxydecyloxy group, a 10-ethoxydecyloxy group, and an 11-methoxyundecyloxy group.

Of these, R ¹ is an H (CH ₂ ) _p O (CH ₂ ) _q group (where p is an integer of 1 to 3 and q is an integer of 6 to 14)
Is more preferable. In the above formula [I], X
¹ represents a group selected from the group consisting of —O— and —COO—, or a single bond. Among these, in the case of the substrate liquid crystal of the present invention, in consideration of the characteristics of the liquid crystal, X ¹ represents a —O— group or
It is preferably a -COO- group. Further, it is more preferably a —COO— group.

A ¹ and B ¹ are each independently

[0054]

Embedded image

A group selected from the group consisting of
^{1 *} represents 4 to 20 carbon atoms having at least one asymmetric carbon
(A hydrogen atom bonded to a carbon atom constituting the optically active group may be replaced by a halogen atom). The guest liquid crystal used in the present invention has the following formula [III]
Is a liquid crystal compound represented by

[0056]

Embedded image

[In the above formula [III], R ² represents an alkyl group having 1 to 16 carbon atoms or a polyfluoroalkyl group (provided that one or two non-adjacent groups are present in these groups) The above-mentioned —CH ₂ — group or —CF ₂ — group may be replaced by —O— group), A ² and B ² are each independently

[0058]

Embedded image

Represents a group selected from the group consisting of the following groups (however, the same group is not selected at the same time), and R ^{2 *} is an optically active group having 4 to 20 carbon atoms having at least one asymmetric carbon. A hydrogen atom bonded to a carbon atom constituting the optically active group may be replaced by a halogen atom), and X ²
Represents a group selected from the group consisting of —O— and —COO—, or a single bond. Among them, in the case of the guest liquid crystal of the present invention, X ² is preferably an —O— group or a single bond in consideration of the characteristics of the liquid crystal.

Y ^{1 to} Y ⁴ are each independently a group selected from the group consisting of H and F, and ^{one of} Y ^{1 to} Y ⁴ is always F].

The liquid crystal compound having the above-mentioned properties may be a mixture of a plurality of compounds selected from the group of compounds represented by the above [III]. Hereinafter, examples of the liquid crystal compound of the formula [III] are shown.

[0062]

[Table 1]

[0063]

[Table 2]

[0064]

[Table 3]

The amount of the liquid crystal compound to be added cannot be determined unequivocally because it varies depending on the physical properties of the liquid crystal compound to be added, the type of the antiferroelectric liquid crystal or the type of the liquid crystal composition thereof. And more preferably 20 to 50 mol%.

R ^{1 * and} R ^{2 *} in the above formulas [I] and [III] are each independently preferably an optically active group represented by the following:

[0067]

Embedded image

(Where k is an integer of 2 to 5, m is 1 to 3)
And n is an integer of 2 to 8). As a specific example
Is -C^*H (CF_Three) -C_TwoH_Five, -C^*H (CF_Three) -C_ThreeH₇, -C^*H (CF_Three) -C
_FourH₉, -C ^*H (CF_Three) -C_FiveH₁₁, -C^*H (CF_Three) -C₆H₁₃, -C^*H (CF_Three) -C
₇H_Fifteen, -C^*H (CF_Three) -C₈H₁₇, -C^*H (CF_Three)-(CH_Two)_TwoOCH_Three, -C^*H
(CF_Three)-(CH_Two)_TwoOC_TwoH_Five, -C^*H (CF_Three)-(CH_Two)_TwoOC_ThreeH₇, -C^*H (C
F_Three)-(CH_Two)_ThreeOCH_Three, -C^*H (CF_Three)-(CH_Two)_ThreeOC_TwoH_Five, -C^*H (CF_Three)-
(CH_Two)_ThreeOC_ThreeH₇, -C^*H (CF_Three)-(CH_Two)_FourOCH_Three, -C^*H (CF_Three)-(CH_Two)
_FourOC_TwoH_Five, -C^*H (CF_Three)-(CH_Two)_FourOC_ThreeH₇, -C^*H (CF_Three)-(CH_Two)_FiveOCH
_Three, -C^*H (CF_Three)-(CH_Two)_FiveOC_TwoH_Five, -C^*H (CF_Three)-(CH_Two)_FiveOC_ThreeH₇,-
C^*H (CH_Three) -C_FourH₉, -C^*H (CH_Three) -C_FiveH₁₁, -C^*H (CH_Three) -C₆H₁₃,-
C^*H (CH_Three) -C₇H_FifteenAnd -C^*H (CH_Three) -C₈H₁₇Is mentioned
You.

The liquid crystal composition of the present invention can be used in combination with an appropriate known liquid crystal compound.
A liquid crystal composition having a wide liquid crystal temperature range can be obtained in combination with the liquid crystal composition of the present invention. Known liquid crystal compounds include ester, diester, azoxy, azo, Schiff, pyrimidine, biphenyl, phenylcyclohexane, cyclohexylcyclohexane,
Examples thereof include a dioxane-based or polycyclic compound-based liquid crystal compound including a benzene ring and a cyclohexane ring.

In forming the liquid crystal composition of the present invention, a known dichroic dye, a light stabilizer or a viscosity reducing agent can be used in combination.

[0071]

According to the present invention, a liquid crystal composition having good responsiveness even in a low temperature region can be obtained by adding a liquid crystal compound having a specific property to a general base liquid crystal. Such a liquid crystal composition exhibits a smectic phase in a wide temperature range including room temperature, and can be used as an antiferroelectric liquid crystal composition.

By further blending the same type and / or another type of liquid crystal substance with the liquid crystal composition of the present invention, the antiferroelectricity of the liquid crystal material of the present invention can be reduced.
A more stable contrast can be obtained with a small decrease in the tilt angle.

Therefore, by using such a liquid crystal composition, it is possible to obtain a liquid crystal element having a high-speed response in a wide temperature range, particularly in the vicinity of room temperature. further,
In a liquid crystal display manufactured using such an element, switching operation of liquid crystal molecules can be performed at high speed, so that the operation time while viewing the display can be significantly reduced. By using such a display, power consumption can be reduced.

[0074]

Next, preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

The liquid crystal cell was manufactured by the following method. After spin-coating polyimide (low pretilt angle) as an alignment film on two glass substrates with transparent electrodes, a rubbing treatment is performed, and a 2.0 μm gap is applied so that the rubbing directions are antiparallel. To assemble the cell.

The response time of the liquid crystal composition in the liquid crystal cell was measured as follows. The liquid crystal cell is placed between the orthogonal polarizing plates,
The liquid crystal layer direction was set so as to be parallel to the analyzer or the polarizer. A pulse voltage of ± 30 V was applied, and the change in the amount of transmitted light was measured by a photomultiplier. The time required for the change of the transmitted light at that time to change from 0% to 90% was defined as the response time, and the response time was measured.

The layer spacing of the smectic phase was measured according to the following method. The liquid crystal was slightly placed on a cover glass, heated until it became an isotropic phase, cooled, and immediately stretched with a spatula immediately after the SmA phase. For other measurement methods and correction methods, refer to “4th Edition
Volume 343-360 ", and the layer spacing of the smectic layer was measured.

[0078]

Example 1 A liquid crystal composition was prepared by mixing the compounds represented by the following formulas [I-1] and [III-1] at the composition ratios shown in Table 4.

Using this liquid crystal composition, the SmC _A ^* phase and
Phase transition temperature (° C) between SmA phase and SmA phase and Iso
The phase transition temperature between phases (° C.) was measured. Table 4 shows the results.

[0080]

Embedded image

A parameter L _SC indicating the temperature dependence of the layer spacing of the smectic phase of the liquid crystal compound represented by the formula [III-1]
/ _LSA is as shown in FIG. 2 and satisfies the above formula [II], and is obtained from T _AC −30 (T−T _AC = −30 ° C.) to T _AC −10 (T−T _AC = −10). ° C) in the temperature range.

Further, regarding the electric field induced phase transition of this liquid crystal composition, the temperature (1000) with respect to the rate constant (1 / tr)
Arrhenius plot of (× 1 / T) is shown in FIG. From this Arrhenius plot, the slope α in the temperature range below the temperature T _AF -35 ° C. was −8.77.

The α value of the compound represented by the formula [I-1], which is the base liquid crystal of the liquid crystal composition, was −21.94. Therefore, the rate of change of the α value by adding the liquid crystal compound represented by the formula [III-1] was 0.40.

[0084]

Comparative Example 1 A liquid crystal composition was prepared by mixing the compounds represented by the above formulas [I-1] and [I-2] at the composition ratios shown in Table 4.

Using this liquid crystal composition, the SmC _A ^* phase and
Phase transition temperature (° C) between SmA phase and SmA phase and Iso
The phase transition temperature between phases (° C.) was measured. Table 4 shows the results.

[0086]

Embedded image

The parameter L _SC / which indicates the temperature dependence of the layer spacing of the smectic phase of the liquid crystal compound represented by the formula [I-2]
L _SA is as shown in FIG. 4 and satisfies the above formula [II], T _AC −30 (T−T _AC = −30 ° C.)
There was a point where the differential value was 0 or less in the temperature range of T _AC -10 to (T-T _AC = -10 ° C.).

Further, regarding the electric field induced phase transition of this liquid crystal composition, the temperature (1000) with respect to the rate constant (1 / tr)
Arrhenius plot of (× 1 / T) is shown in FIG. From this Arrhenius plot, the slope α in the temperature range below the temperature T _AF -35 ° C. was −17.72.

As described above, the β / α value of the compound represented by the formula [I-1], which is the base liquid crystal of this liquid crystal composition, was −21.94. Therefore, the rate of change of the α value due to the addition of the liquid crystal compound represented by the formula [I-2] was 0.81.

[0090]

[Table 4]

[0091]

Example 2 Compounds represented by the following formulas [I-3] and [III-2] were mixed at a composition ratio shown in Table 5,
A liquid crystal composition was prepared.

Using this liquid crystal composition, an SmC _A ^* phase and
Phase transition temperature (° C) between SmA phase and SmA phase and Iso
The phase transition temperature between phases (° C.) was measured. Table 5 shows the results.

[0093]

Embedded image

A parameter L indicating the temperature dependence of the layer spacing of the smectic phase of the liquid crystal compound represented by the formula [III-2]
_SC / _LSA is as shown in FIG. 5 and satisfies the above formula [II], and is obtained from T _AC −30 (T−T _AC = −30 ° C.) to T _AC −10 (T−T _AC = −). The differential value in the temperature range of 10 ° C.) was larger than 0.

Further, regarding the electric field induced phase transition of the liquid crystal composition, the temperature (1000) with respect to the rate constant (1 / tr)
Arrhenius plot of (× 1 / T) is shown in FIG. From this Arrhenius plot, the slope α in the temperature range below the temperature T _AF -35 ° C. was −11.13.

The α value of the compound represented by the formula [I-3], which is the base liquid crystal of this liquid crystal composition, was -19.12. Therefore, the rate of change of the α value due to the addition of the liquid crystal compound represented by the formula [III-2] was 0.58.

[0097]

Comparative Example 2 A liquid crystal composition was prepared by mixing the compounds represented by the above formulas [I-3] and [I-2] at the composition ratios shown in Table 5.

Using this liquid crystal composition, an SmC _A ^* phase and
Phase transition temperature (° C) between SmA phase and SmA phase and Iso
The phase transition temperature between phases (° C.) was measured. Table 5 shows the results.

[0099]

Embedded image

The parameter L _SC / which indicates the temperature dependence of the layer spacing of the smectic phase of the liquid crystal compound represented by the formula [I-2]
L _SA is as shown in FIG. 4 and satisfies the above formula [II], T _AC −30 (T−T _AC = −30 ° C.)
There was a point where the differential value was 0 or less in the temperature range of T _AC -10 to (T-T _AC = -10 ° C.).

Regarding the electric field-induced phase transition of this liquid crystal composition, the temperature (1000) with respect to the rate constant (1 / tr)
Arrhenius plot of (× 1 / T) is shown in FIG. From this Arrhenius plot, the slope α in the temperature range below the temperature T _AF −35 ° C. was −16.05.

As described above, the α value of the compound represented by the formula [I-3], which is the base liquid crystal of this liquid crystal composition, is −
19.12. Therefore, the rate of change of the α value by adding the liquid crystal compound represented by the formula [I-2] was 0.84.

[0103]

[Table 5]

[0104]

Example 3 Compounds represented by the following formulas [I-4] and [III-3] were mixed at a composition ratio shown in Table 6,
A liquid crystal composition was prepared.

Using this liquid crystal composition, an SmC _A ^* phase and
Phase transition temperature (° C) between SmA phase and SmA phase and Iso
The phase transition temperature between phases (° C.) was measured. Table 6 shows the results.

[0106]

Embedded image

Regarding the electric field-induced phase transition of this liquid crystal composition, the temperature (1000 × 1) with respect to the rate constant (1 / tr)
/ T) is shown in FIG. From this Arrhenius plot, the slope α in the temperature range below the temperature T _AF -35 ° C. was −12.04.

The α value of the compound represented by the formula [I-4], which is the base liquid crystal of the liquid crystal composition, was -17.126. Therefore, the rate of change of the α value by adding the liquid crystal compound represented by the formula [III-3] is 0.70
Met.

[0109]

Comparative Example 3 A liquid crystal composition was prepared by mixing the compounds represented by the above formulas [I-4] and [I-5] at the composition ratios shown in Table 6.

Using this liquid crystal composition, the SmC _A ^* phase and
Phase transition temperature between SmA phase (℃) and SmA phase and Iso
The phase transition temperature between phases (° C.) was measured. Table 6 shows the results.

[0111]

Embedded image

Regarding the electric field-induced phase transition of this liquid crystal composition, the temperature (1000 × 1) with respect to the rate constant (1 / tr)
/ T) is shown in FIG. From this Arrhenius plot, the slope α in the temperature range below the temperature T _AF -35 ° C. was −25.81.

As described above, the α value of the compound represented by the formula [I-4], which is the base liquid crystal of this liquid crystal composition, is −
17.126. Therefore, the ratio of change in α value due to the addition of the liquid crystal compound represented by the formula [I-5] was 1.51.

[0114]

[Table 6]

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an Arrhenius plot showing a relationship between a rate constant and a temperature in an electric field-induced phase transition of SmC _A ^* of a liquid crystal composition according to the present invention.

FIG. 2 is a graph showing the temperature dependence of the layer spacing during the phase transition between the smectic A phase and the smectic C phase of the liquid crystal compound serving as the guest liquid crystal used in Example 1 of the liquid crystal composition according to the present invention. FIG.

FIG. 3 is an Arrhenius plot showing a relationship between a rate constant and a temperature in an electric field-induced phase transition of SmC _A ^{* in} the liquid crystal compositions according to Example 1 and Comparative Example 1 of the present invention. It is a graph shown.

FIG. 4 is a graph showing the temperature dependence of the layer spacing during the phase transition between the smectic A phase and the smectic C phase of the liquid crystal compound serving as the guest liquid crystal used in Comparative Example 1 of the liquid crystal composition according to the present invention. FIG.

FIG. 5 is a graph showing the temperature dependence of the layer spacing during the phase transition between the smectic A phase and the smectic C phase of the liquid crystal compound serving as the guest liquid crystal used in Example 2 of the liquid crystal composition according to the present invention. FIG.

FIG. 6 is an Arrhenius plot showing the relationship between the temperature constant and the temperature constant in the electric field-induced phase transition of SmC _A ^{* in} the liquid crystal compositions according to Example 2 and Comparative Example 2 of the present invention. It is a graph shown.

FIG. 7 is an Arrhenius plot showing the relationship between the temperature constant and the rate constant in the electric field-induced phase transition of SmC _A ^{* in} the liquid crystal compositions of Example 3 and Comparative Example 3 of the present invention. It is a graph shown.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G02F 1/13 500 G02F 1/13 500 (72) Inventor Sakai Yukari 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemicals Co., Ltd. In-house (72) Inventor Hideo Hama 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 4H027 BA07 BD02 BD08 BD20 BD23 BE02 DK08

Claims (8)

[Claims] 1. An antiferroelectric liquid crystal composition comprising a base liquid crystal and a liquid crystal compound, wherein an upper limit temperature at which a transition from an antiferroelectric phase to another phase is T _AF.
(If the other phase is a smectic A phase, T _AF is T
Matches _AC . Here, T _AC is the phase transition temperature between the smectic A phase and the smectic C phase).
In the slope α of the Arrhenius plot in a temperature range of T _AF -35 (° C.) or less, the α value obtained by using the composition is a ratio of 0.8 or less of the α value when only the base liquid crystal is used. An antiferroelectric liquid crystal composition, wherein a liquid crystal compound is added to the base liquid crystal. 2. The antiferroelectric liquid crystal composition according to claim 1, wherein the base liquid crystal contains at least one compound selected from the group consisting of compounds represented by the following formula [I]. ; Embedded image [However, in the formula [I], R ¹ is one kind of group selected from the group consisting of an alkyl group having 3 to 16 carbon atoms or a polyfluoroalkyl group (however, one of the groups present in these groups) Or two or more non-adjacent —CH ₂ — groups, or —CF ₂ — groups may be replaced by —O— groups), X ¹ is —O—, —COO—, or A ¹ and B ¹ each independently represent the following: R ^{1 *} represents a group having 4 to 2 carbon atoms having at least one asymmetric carbon atom.
0 represents an optically active group (a hydrogen atom bonded to a carbon atom constituting the optically active group may be replaced by a halogen atom). ] 3. In the base liquid crystal, R ¹ is H (CH ₂ ) _p O
(CH _{2) q} group (wherein, p is an integer of 1 to 3, q is a is 6-14 integer) antiferroelectric liquid crystal composition according to claim 2, characterized in that a. 4. The antiferroelectric liquid crystal composition according to claim 2, wherein in the base liquid crystal, X ¹ is a —COO— group. 5. A temperature dependence of a layer interval in a phase transition between a smectic A phase and a smectic C phase of a smectic layer of the liquid crystal compound is represented by the following formula [II]:
In a temperature range of T _AC -30 (° C.) to T _AC -10 (° C.) (T _AC is a phase transition temperature between the smectic A phase and the smectic C phase), a differential value of a change in a layer interval related to the phase transition. 2. The antiferroelectric liquid crystal composition according to claim 1, wherein is a liquid crystal compound having a value greater than 0. [In the above formula [II], L _SA represents a layer spacing in a smectic A phase, and L _SC represents a layer spacing in a chiral smectic C phase (including a ferroelectric phase or an antiferroelectric phase)]. 6. The antiferroelectric liquid crystal according to claim 5, wherein the antiferroelectric liquid crystal composition contains a liquid crystal compound having the above characteristics in an amount of 10 mol% to 60 mol%. Composition. 7. The antiferroelectric liquid crystal composition according to claim 5, wherein the liquid crystal compound is at least one compound selected from a group of compounds represented by the following formula [III]: Chemical formula 3] [In the above formula [III], R ² represents an alkyl group having 1 to 16 carbon atoms or a polyfluoroalkyl group (provided that one or two or more non-adjacent- The CH ₂ -group or the -CF ₂ -group may be replaced by an -O- group), A ² and B ² each independently represent Represents a group selected from the group consisting of the following groups (however, the same group is not selected at the same time), and R ^{2 *} has 4 to ² carbon atoms having at least one asymmetric carbon.
X represents an optically active group (a hydrogen atom bonded to a carbon atom constituting the optically active group may be replaced by a halogen atom); X ² represents an —O— group, —COO— or a single bond. , Y ^{1 to} Y ⁴ are each independently a group selected from the group consisting of H and F, and any one of Y ^{1 to} Y ⁴ is always F]. 8. R in the formulas [I] and [III]
^{1 *} or R ^{2 *} is (Where k is an integer of 2 to 5, m is an integer of 1 to 3, and n is an integer of 2 to 8), and is a kind of group selected from the group consisting of: 3. The antiferroelectric liquid crystal composition according to item 1.