JP2013216848A - Ferroelectric liquid crystal composition and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric liquid crystal composition which is excellent in impact resistance, orientation characteristic and driving characteristic and has a desired intrinsic polarization, and a liquid crystal display element.SOLUTION: A ferroelectric liquid crystal composition contains two types of chiral compounds having optical rotary powers in opposite directions, each of which is composed of at least either of a chiral compound A represented by general formula (1) and a four-benzene rings chiral compound B. (In the formula, R, which is a non-chiral group, is alkyl or alkoxyalkyl. Ris an ester group-containing chiral group. X1-X8 each independently represent -CH3, -CF3, halogen atom or hydrogen atom. But, one or more of X1-X8 are each independently -CH3, -CF3 or halogen atom).

Description

  The present invention relates to a ferroelectric liquid crystal composition having impact resistance and a liquid crystal display device.

  Liquid crystal display elements have been widely used from large displays to portable information terminals because of their thinness and low power consumption, and their development is actively underway. So far, liquid crystal display elements have been developed and put to practical use, such as TN mode, STN multiplex drive, and active matrix drive using thin layer transistors (TFTs) for TN, but these use nematic liquid crystals. In addition, the response speed of the liquid crystal material is as slow as several ms to several tens of ms, and it cannot be said that it is sufficiently compatible with moving image display.

Ferroelectric liquid crystal is expected to provide a high-performance liquid crystal display element because it has a superior response speed such as a wide viewing angle because it has a response speed as short as μs and is suitable for high-speed devices. .
However, the ferroelectric liquid crystal has a higher molecular order than the nematic liquid crystal, so that it is difficult to return to its original state when the regularity of molecular orientation is disturbed by impact, that is, it is very weak to external impact. Have

As means for improving the impact resistance, for example, a method of arranging a partition wall (also referred to as a rib) between a pair of substrates has been proposed (see, for example, Patent Document 1 and Patent Document 2). However, even when the partition walls are provided, there is a problem that alignment disturbance occurs when a shock is locally applied to the liquid crystal display element.
Further, as means for improving impact resistance, for example, a method of adding a gelling agent to a ferroelectric liquid crystal composition (see Patent Document 3), a method of adding a curable resin to a ferroelectric liquid crystal composition, A method of adding a thermoplastic resin to a dielectric liquid crystal composition (see Patent Document 4), a method using a ferroelectric polymer liquid crystal having a ferroelectric liquid crystal structure in the side chain, a liquid crystal polymer compound and a low molecular ferroelectric A method of mixing a conductive liquid crystal compound (see Patent Document 5) has been proposed. However, these methods have a problem that the drive voltage becomes high. In addition, even if a polymer compound is used for the ferroelectric liquid crystal composition, the regularity of the molecular orientation is less likely to be disturbed to a certain degree of weak impact, but the orientation regularity is disturbed by a strong impact. The essential problem that it is difficult to return to the original state has not been solved.

  Recently, attempts have been made to increase the impact resistance of the ferroelectric liquid crystal composition itself for the purpose of improving the impact resistance, and various structures of chiral compounds used in the ferroelectric liquid crystal composition have been studied ( (See Patent Document 6). According to Patent Document 6, when a ferroelectric liquid crystal composition containing a chiral compound having a predetermined structure in which a plurality of benzene rings are directly bonded is used, the contrast ratio is good even after an impact is applied. It has been reported that

JP 2004-77541 A International Publication No. 02/03131 Pamphlet JP 2004-233414 A JP 2003-114440 A Japanese Patent No. 3541437 International Publication No. 2010/031431 Pamphlet

  By the way, the ferroelectric liquid crystal composition has spontaneous polarization. In driving a liquid crystal display device using a ferroelectric liquid crystal composition having spontaneous polarization, a polarization reversal current is generated when a voltage is applied, so that the effective voltage applied to the liquid crystal is lowered. Therefore, when the spontaneous polarization of the ferroelectric liquid crystal composition is too large, there arises a problem that it becomes difficult to drive the liquid crystal. Therefore, when the spontaneous polarization of the ferroelectric liquid crystal composition is too large, it is necessary to reduce the spontaneous polarization.

  Means for reducing the spontaneous polarization of the ferroelectric liquid crystal composition include, for example, a method of reducing the amount of chiral compound that induces spontaneous polarization, a method of adjusting the skeleton structure of the chiral compound, and a method of adjusting the host liquid crystal. Can be mentioned.

However, in the case of a ferroelectric liquid crystal composition containing a chiral compound that contributes to the impact resistance described above, there is a problem that the impact resistance deteriorates if the amount of the chiral compound is reduced. Further, when the skeleton structure of the chiral compound is changed, the impact resistance may be deteriorated or the alignment regularity of the liquid crystal molecules may be easily disturbed. Further, when the host liquid crystal is changed, the tilt angle may be reduced and the luminance may be lowered.
Furthermore, it is extremely difficult to synthesize a chiral compound for obtaining a ferroelectric liquid crystal composition that satisfies all of impact resistance, spontaneous polarization, alignment characteristics, and driving characteristics.

  The present invention has been made in view of the above-mentioned problems, and mainly provides a ferroelectric liquid crystal composition and a liquid crystal display element which are excellent in impact resistance, alignment characteristics and driving characteristics and have desired spontaneous polarization. It is the purpose.

  As a result of various studies on impact resistance, spontaneous polarization, alignment characteristics, and driving characteristics of the ferroelectric liquid crystal composition, the present inventors have a specific structure in which a plurality of benzene rings are directly bonded, By using two kinds of chiral compounds whose optical rotation is opposite, it is possible to control the magnitude of spontaneous polarization while maintaining impact resistance, orientation characteristics and driving characteristics, and also to improve scratch resistance. The present invention has been found out based on such findings.

  That is, the present invention is at least one of a chiral compound A represented by the following general formula (1) and a chiral compound B represented by the following general formula (2). Provided is a ferroelectric liquid crystal composition comprising at least one of chiral compound A and chiral compound B and containing levorotatory chiral compound II and having spontaneous polarization.

(In the above formula (1), R ¹ is a non-chiral group and is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ² is a chiral group and is a group represented by the following general formula (3).

In (the formula (3), R ³ is an alkyl or alkoxyalkyl group of saturated or unsaturated 1 to 10 carbon atoms which may be substituted with a halogen atom.
Y ¹ represents —CH ₃ or a fluorine atom. m is 0 or 1. n is 0 or 1. * Indicates a chiral center. )
X ^{1 to} X ⁸ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{1 to} X ⁸ are each independently —CH ₃ , —CF ₃ or a halogen atom. )

(In the above formula (2), R ⁴ is an achiral group, which is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ⁵ is a chiral group, and is a group represented by the above formula (3).
X ^{9 to} X ²⁰ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{9 to} X ²⁰ are each independently —CH ₃ , —CF ₃ or a halogen atom.
K represents a single bond or a cyclohexane ring. )

  Since the ferroelectric liquid crystal composition of the present invention contains at least one of the chiral compound A represented by the above formula (1) and the chiral compound B represented by the above formula (2), It is possible to achieve impact properties. Furthermore, since the ferroelectric liquid crystal composition of the present invention contains the two kinds of chiral compounds whose optical rotations are in opposite directions, the magnitude of spontaneous polarization is controlled while maintaining impact resistance, orientation characteristics and driving characteristics. It is possible to improve scratch resistance.

  The present invention also includes a first alignment treatment substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment film formed on the first electrode layer; A second alignment substrate having a second substrate, a second electrode layer formed on the second substrate, and a second alignment film formed on the second electrode layer, and the first alignment film And a liquid crystal layer formed between the second alignment films and including a ferroelectric liquid crystal composition having spontaneous polarization, wherein the ferroelectric liquid crystal composition has the formula (1) At least one of the chiral compound A represented by formula (2) and the chiral compound B represented by the above formula (2), and a dextrorotatory chiral compound I, and at least one of the chiral compound A and the chiral compound B A liquid crystal characterized by containing levorotatory chiral compound II To provide a 示素Ko.

  According to the present invention, since the liquid crystal layer contains the above-described ferroelectric liquid crystal composition, it is possible to obtain a liquid crystal display element that is excellent in impact resistance, alignment characteristics, and driving characteristics, and also in scratch resistance. is there.

  In the present invention, the ferroelectric liquid crystal composition contains two kinds of chiral compounds having a specific structure and reverse optical rotation, so that it is spontaneous while maintaining impact resistance, alignment characteristics and driving characteristics. The magnitude of polarization can be controlled, and further, scratch resistance can be improved.

It is a schematic diagram which shows an example of the orientation state of the liquid crystal molecule in this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention.

  Hereinafter, the ferroelectric liquid crystal composition and the liquid crystal display element of the present invention will be described in detail.

A. Ferroelectric liquid crystal composition The ferroelectric liquid crystal composition of the present invention is at least one of a chiral compound A represented by the following general formula (1) and a chiral compound B represented by the following general formula (2). And a dextrorotatory chiral compound I and at least one of the chiral compound A and the chiral compound B, and a levorotatory chiral compound II.

(In the above formula (1), R ¹ is a non-chiral group and is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ² is a chiral group and is a group represented by the following general formula (3).

In (the formula (3), R ³ is an alkyl or alkoxyalkyl group of saturated or unsaturated 1 to 10 carbon atoms which may be substituted with a halogen atom.
Y ¹ represents —CH ₃ or a fluorine atom. m is 0 or 1. n is 0 or 1. * Indicates a chiral center. )
X ^{1 to} X ⁸ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{1 to} X ⁸ are each independently —CH ₃ , —CF ₃ or a halogen atom. )

(In the above formula (2), R ⁴ is an achiral group, which is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ⁵ is a chiral group, and is a group represented by the above formula (3).
X ^{9 to} X ²⁰ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{9 to} X ²⁰ are each independently —CH ₃ , —CF ₃ or a halogen atom.
K represents a single bond or a cyclohexane ring. )

  Since the ferroelectric liquid crystal composition of the present invention contains at least one of the chiral compound A represented by the above formula (1) and the chiral compound B represented by the above formula (2), It is possible to achieve impact properties.

In order to improve the impact resistance, it is necessary to contain a predetermined amount of the chiral compound. Since the chiral compound induces spontaneous polarization in the ferroelectric liquid crystal composition, when a predetermined amount of the chiral compound is contained, the spontaneous polarization tends to increase. On the other hand, when the spontaneous polarization becomes too large, when the liquid crystal display element is driven by the TFT, the voltage holding ratio is lowered due to the inversion of the spontaneous polarization, so that the drive voltage becomes high. Therefore, in order to enable stable driving at a low voltage, it is necessary to reduce the spontaneous polarization.
In the present invention, a dextrorotatory chiral compound I and a levorotatory chiral compound II are contained, and these chiral compounds have opposite optical rotations, so that the spontaneous polarizations of each other cancel each other, and effective Spontaneous polarization can be reduced. Therefore, unlike the conventional case of adjusting the amount of the chiral compound and the skeleton structure, it is possible to control the magnitude of the spontaneous polarization while maintaining the impact resistance, the orientation characteristics, and the driving characteristics.

Furthermore, in the present invention, scratch resistance can be improved by including two kinds of chiral compounds I and II having opposite optical rotations.
“Scratch resistance” refers to the performance of the liquid crystal alignment to withstand scratching, and evaluates the liquid crystal alignment when scratched with a sharp object. Specifically, the surface of the liquid crystal display element is scratched with a pen, and the time until the scratches disappear is evaluated.

  The reason why the scratch resistance is improved by using the two kinds of chiral compounds having opposite optical rotations is not clear, but is estimated as follows. That is, if the ferroelectric liquid crystal composition has a higher molecular arrangement regularity and has an arrangement state of molecules close to the crystal phase, the liquid crystal molecules move from the state in which they move when they are scratched by a sharp object. It becomes difficult to return to the state of, and scratch resistance is inferior. The chiral compound in the present invention has a core part in which three or four benzene rings are directly bonded. Generally, the benzene ring has a planar structure, so that the regularity of the molecular arrangement becomes high. On the other hand, when two types of chiral compounds having opposite optical rotations are contained, it is considered that the molecular arrangement that is too regular can be relaxed due to the effect of the three-dimensional structure of the chiral compound. Therefore, in the present invention, it is presumed that the scratch resistance can be enhanced by containing the dextrorotatory chiral compound I and the levorotatory chiral compound II whose optical rotation is in the opposite direction.

  Hereinafter, each component in the ferroelectric liquid crystal composition of the present invention will be described.

1. Chiral Compound I and Chiral Compound II
The chiral compound I used in the present invention is at least one of the chiral compound A represented by the above formula (1) and the chiral compound B represented by the above formula (2), and exhibits dextrorotatory properties. . The chiral compound II used in the present invention is at least one of the chiral compound A and the chiral compound B, and exhibits levorotatory properties. That is, the ferroelectric liquid crystal composition of the present invention contains two kinds of chiral compounds having opposite optical rotation directions.

  Hereinafter, the chiral compound A and the chiral compound B will be described.

(1) Chiral compound A
The chiral compound A used in the present invention is a compound represented by the above formula (1).

In the above formula (1), R ¹ is a non-chiral group and is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
Although carbon number should just be 4-18, 6-18 are preferable especially and 6-12 are more preferable. This is because when the number of carbon atoms is larger than the above range, the synthesis of the chiral compound A becomes difficult and the cost increases. On the other hand, if the number of carbon atoms is less than the above range, the ferroelectric liquid crystal composition may not exhibit a smectic phase. In addition, when the alkyl group and the alkoxyalkyl group are substituted with a halogen atom, the ferroelectric liquid crystal composition may exhibit a smectic phase with a comparatively at least carbon number.
The alkyl group or alkoxyalkyl group may be substituted with a halogen atom or may not be substituted with a halogen atom, but among them, it is preferable that the alkyl group or alkoxyalkyl group is not substituted with a halogen atom.
The alkyl group or alkoxyalkyl group is linear or branched.
The alkyl group or alkoxyalkyl group may be saturated or unsaturated, but is preferably saturated. In unsaturated alkanes other than cyclic unsaturated alkanes, unsaturated alkanes are more reactive than saturated alkanes, and the display quality may be deteriorated due to changes in materials due to long-term storage / driving and temperature changes. It is.
R ¹ may be an alkyl group or an alkoxyalkyl group, but is preferably an alkyl group.

In the above formula (1), R ² is a chiral group having one or more chiral centers, and is a group represented by the above formula (3).

In the above formula (3), R ³ is a saturated or unsaturated alkyl or alkoxyalkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom.
The alkyl group or alkoxyalkyl group is linear, branched or cyclic.
R ³ may be an alkyl group or an alkoxyalkyl group, but is preferably an alkyl group.

In the above formula (3), Y ¹ represents —CH ₃ or a fluorine atom. In the case of —CH ₃ , there is an advantage that the synthesis of the chiral compound A is easy. On the other hand, in the case of fluorine atoms, since the spontaneous polarization of the ferroelectric liquid crystal composition becomes relatively large, there is an advantage that the response speed can be increased.
Y ¹ may be —CH ₃ or a fluorine atom, and among them, —CH ₃ is preferable. As described above, the synthesis of the chiral compound A is easy, the chiral compound A can be produced stably, and the ferroelectric liquid crystal composition can be obtained at a low cost.

In the above formula (3), m is 0 or 1.
In the above formula (3), * indicates a chiral center. When m = 0, the 1st carbon atom becomes a chiral center, and when m = 1, the 2nd carbon atom becomes a chiral center.

  In the above formula (3), n is 0 or 1. When n = 0, the chiral compound is relatively difficult to polarize because the chiral site has no ester bond. On the other hand, when n = 1, the chiral moiety has an ester bond, so that the chiral compound is easily polarized.

In the above formula (1), X ^{1 to} X ⁸ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{1 to} X ⁸ are each independently —CH ₃ , —CF ₃ or a halogen atom.
When all of X ^{1 to} X ⁸ are hydrogen atoms, the solubility of the chiral compound A is lowered, so that the synthesis and purification of the chiral compound A becomes difficult, the cost is increased, and the molecular arrangement rule There is a risk that the desired impact resistance may not be obtained. On the other hand, when one or more of X ^{1 to} X ⁸ are —CH ₃ , —CF ₃ or a halogen atom as in the present invention, the solubility of the chiral compound A in the solvent increases, Synthesis and purification become possible. In addition, since the steric structure of the chiral compound A is distorted and the molecular arrangement that is too regular can be relaxed by this distortion, it is considered that high impact resistance can be obtained.

Among ^them, any one or more of ^{X 1 ~X 3, X 5 ~X} 7 is, _-CH 3 each independently is preferably a -CF ₃ or a halogen atom. This is because the chiral compound has better solubility than the X ⁴ and X ⁸ positions when it has a substituent at the X ^{1 to} X ³ and X ^{5 to} X ⁷ positions. This is presumably because the X ⁴ and X ⁸ positions are less distorted by substituents than the other positions.

Of the two benzene rings to which X ^{1 to} X ⁸ are bonded, the benzene ring having a substituent may have 1 to 4 substituents, and among them, may have one substituent. preferable. That is, when the benzene ring to which X ¹ , X ² , X ⁵ , and X ⁶ are bonded has a substituent, any one of X ¹ , X ² , X ⁵ , and X ⁶ is —CH _3. , —CF ₃ or a halogen atom is preferable. When the benzene ring to which X ³ , X ⁴ , X ⁷ , X ⁸ is bonded has a substituent, one of X ³ , X ⁴ , X ⁷ , X ⁸ is —CH ₃ , It is preferably —CF ₃ or a halogen atom.
In particular, it is preferable that only one of X ^{1 to} X ⁸ is —CH ₃ , —CF ₃ or a halogen atom.

Moreover, it is also preferable that the benzene ring which has a substituent has two substituents. In this case, as the positions of the above two substituents, it is preferable that fluorine atoms are respectively substituted on adjacent carbon atoms of the benzene ring as in the case where, for example, X ¹ and X ² are fluorine atoms. When two fluorine atoms are substituted on adjacent carbon atoms of the benzene ring, and the benzene ring is symmetrically substituted, the chiral smectic C phase is stabilized and the tilt angle of the liquid crystal molecules can be increased. Therefore, the transmittance of the liquid crystal display element can be increased. Further, since the two substituents are bonded to a carbon atom located closer to each other, the rod-like structure of the chiral compound is not destroyed, so that the impact resistance can be maintained.
Furthermore, it is preferable that one benzene ring has two substituents among the two benzene rings to which X ^{1 to} X ⁸ are bonded, and among them, X ¹ , X ² , X ⁵ , X ⁶ The benzene ring to which is bonded preferably has two substituents. This is because, among the three directly bonded benzene rings, the ferroelectric liquid crystal composition is difficult to crystallize because the middle benzene ring has a substituent.
In particular, X ¹ and X ² or X ⁵ and X ⁶ are preferably fluorine atoms.

Further, the substituent that the benzene ring has is preferably —CH ₃ , a fluorine atom, or a chlorine atom, and particularly preferably —CH ₃ or a fluorine atom, when the number of substituents is one. On the other hand, when there are two substituents, it is preferable that any substituent is a fluorine atom. When two fluorine atoms are substituted on the benzene ring, the two fluorine atoms are preferably substituted with adjacent carbon atoms.

  Specific examples of the chiral compound A represented by the above formula (1) include chiral compounds represented by the following general formulas (1-1) to (1-2) and (1-3) to (1-4). A is mentioned.

(In the above formulas (1-1) to (1-2) and (1-3) to (1-4), R ¹¹ is a saturated or unsaturated alkyl group having 1 to 10 carbon atoms. Represents a chiral center, m is 0 or 1, p is 4 to 18, X ²¹ and X ²² each independently represent —CH ₃ , —CF ₃ or a halogen atom, and the above formula (1-1 ) To (1-2), one of j and k is 0 and the other is 1.)

  In said formula (1-1)-(1-2) and (1-3)-(1-4), p is 4-18, Preferably it is 6-18, More preferably, it is 6-12. As described above, when the number of carbon atoms is larger than the above range, the synthesis of the chiral compound A becomes difficult. On the other hand, if the number of carbon atoms is less than the above range, the ferroelectric liquid crystal composition may not exhibit a smectic phase.

In the above formula (1-1) to (1-2) and (1-3) - ^{(1-4), R 11} is a saturated or unsaturated alkyl group having 1 to 10 carbon atoms. The alkyl group is linear, branched or cyclic. Among these, R ¹¹ is preferably a linear or branched saturated alkyl group or a phenylalkyl group.

In the above formulas (1-2) and (1-4), m is 0 or 1.
Moreover, in said formula (1-1)-(1-2) and (1-3)-(1-4), * mark shows a chiral center. In the above formulas (1-1) and (1-3), the carbon atom at the 1-position is a chiral center. In the above formulas (1-2) and (1-4), when m = 0, the 1st carbon atom becomes a chiral center, and when m = 1, the 2nd carbon atom becomes a chiral center.

In the above formulas (1-1) and (1-2), X ²¹ and X ²² each independently represent —CH ₃ , —CF ₃ or a halogen atom. Among them, —CH ₃ , a fluorine atom or a chlorine atom is preferable, and —CH ₃ or a fluorine atom is particularly preferable.
The positions of X ²¹ and X ²² are the same as the positions of X ^{1 to} X ⁸ described above.

  In the above formulas (1-1) and (1-2), one of j and k is 0 and the other is 1.

  As described above, the chiral compound A represented by the above formulas (1-1) and (1-3) is easily polarized because the chiral site has an ester bond. On the other hand, the chiral compound A represented by the above (1-2) and (1-4) is relatively difficult to polarize because the chiral site does not have an ester bond.

  Specific examples of the chiral compound A represented by the above formulas (1-1) and (1-2) include a chiral compound A represented by the following formula. In the following formula, dextrorotatory property is represented by (+) and levorotatory property is represented by (−).

  Specific examples of the chiral compound A represented by the above formulas (1-3) and (1-4) include a chiral compound A represented by the following formula. In addition, dextrorotatory property is indicated by (+) and levorotatory property is indicated by (−).

  As such a chiral compound A, 1 type may be used independently and 2 or more types may be mixed and used for it.

  The chiral compound A can be synthesized, for example, by the method described in International Publication No. 2010/031431.

(2) Chiral compound B
The chiral compound B used in the present invention is a compound represented by the above formula (2).

  In the above formula (2), K represents a single bond or a cyclohexane ring. When K is a single bond, as represented by the following general formula (2-1), the chiral compound B is one in which four benzene rings are directly bonded. When K is a cyclohexane ring, as represented by the following general formula (2-2), the chiral compound B is obtained by directly bonding four benzene rings and one cyclohexane ring. Among these, K is preferably a single bond.

(In the above formulas (2-1) and (2-2), R ⁴ , R ⁵ , and X ^{9 to} X ²⁰ are the same as in the above formula (2).)

In the above formula (2), R ⁴ is a non-chiral group and is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
Since for R ⁴ is the same as R ¹ in chiral compound A represented by the above formula (1), and description thereof is omitted here.

In the above formula (2), R ⁵ is a chiral group having one or more chiral centers, and is a group represented by the above formula (3).
Since for R ⁵ is the same as R ² in the chiral compounds A represented by the above formula (1), and description thereof is omitted here.

In the above formula (2), X ^{9 to} X ²⁰ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{9 to} X ²⁰ are each independently —CH ₃ , —CF ₃ or a halogen atom. In the same manner as X ^{1 to} X ⁸ in the chiral compound A represented by the above formula (1), when one or more of X ^{9 to} X ²⁰ are —CH ₃ , —CF ₃ or a halogen atom, chiral The solubility of Compound B in the solvent becomes high, and mass synthesis and purification become possible. In addition, since the steric structure of the chiral compound B is distorted, and the molecular arrangement that is too regular is relaxed by this distortion, it is considered that high impact resistance can be obtained.

Among ^them, any one or more of ^{X 9 ~X 13, X 15 ~X} 19 is, _-CH 3 each independently is preferably a -CF ₃ or a halogen atom. This is because the chiral compound has better solubility than the X ¹⁴ and X ²⁰ positions when it has a substituent at the X ^{9 to} X ¹³ and X ^{15 to} X ¹⁹ positions. This is presumably because the X ¹⁴ and X ²⁰ positions are less distorted by substituents than the other positions.

Of the three benzene rings to which X ^{9 to} X ²⁰ are bonded, the benzene ring having a substituent can have 1 to 4 substituents, and among them, it can have one substituent. preferable. That is, when the benzene ring to which X ⁹ , X ¹⁰ , X ¹⁵ , and X ¹⁶ are bonded has a substituent, any one of X ⁹ , X ¹⁰ , X ¹⁵ , and X ¹⁶ is —CH _3. , —CF ₃ or a halogen atom is preferable. When the benzene ring to which X ¹¹ , X ¹² , X ¹⁷ and X ¹⁸ are bonded has a substituent, any one of X ¹¹ , X ¹² , X ¹⁷ and X ¹⁸ is —CH ₃ , — CF ₃ or a halogen atom is preferred. When the benzene ring to which X ¹³ , X ¹⁴ , X ¹⁹ , X ²⁰ is bonded has a substituent, any one of X ¹³ , X ¹⁴ , X ¹⁹ , X ²⁰ is —CH ₃ , — CF ₃ or a halogen atom is preferred.
In particular, it is preferable that one or two benzene rings each have one substituent among the three benzene rings to which X ^{9 to} X ²⁰ are bonded.

Moreover, it is also preferable that the benzene ring which has a substituent has two substituents. In this case, as in the case of the chiral compound A, the position of the two substituents is such that, for example, when X ⁹ and X ¹⁰ are fluorine atoms, the adjacent carbon atoms of the benzene ring are each substituted with a fluorine atom. It is preferable.
Furthermore, it is preferable that one benzene ring has two substituents among the three benzene rings to which X ^{9 to} X ²⁰ are bonded, and among them, X ⁹ , X ¹⁰ , X ¹⁵ , X ¹⁶ Or it is preferable that the benzene ring which X < ¹¹ >, X < ¹² >, X <^17> , X < ¹⁸ > has couple | bonded has two substituents. This is because, among the four directly bonded benzene rings, the ferroelectric liquid crystal composition is difficult to crystallize because the middle benzene ring has a substituent.
In particular, X ⁹ and X ¹⁰ , X ¹¹ and X ¹² , X ¹⁵ and X ¹⁶ , or X ¹⁷ and X ¹⁸ are preferably fluorine atoms.

Further, the substituent that the benzene ring has is preferably —CH ₃ , a fluorine atom, or a chlorine atom, and particularly preferably —CH ₃ or a fluorine atom, when the number of substituents is one. On the other hand, when there are two substituents, it is preferable that any substituent is a fluorine atom. When two fluorine atoms are substituted on the benzene ring, the two fluorine atoms are preferably substituted with adjacent carbon atoms.

  Specific examples of the chiral compound B represented by the above formula (2) include chiral compounds represented by the following general formulas (2-3) to (2-6) and (2-7) to (2-10) B is mentioned.

(In the above formulas (2-3) to (2-6) and (2-7) to (2-10), R ¹² is a saturated or unsaturated alkyl group having 1 to 10 carbon atoms. Represents a chiral center, m is 0 or 1, v is 4 to 18, X ^{31 to} X ³³ each independently represent —CH ₃ , —CF ₃ or a halogen atom, and the above formula (2-3 ) To (2-6), any one or two of r, s, and t is 1, and the rest is 0. One of u and w in the above formulas (2-7) to (2-10) is 1 The other is 0.)

  In said formula (2-3)-(2-6) and (2-7)-(2-10), v is 4-18, Preferably it is 6-18, More preferably, it is 6-12. As described above, when the number of carbon atoms is larger than the above range, the synthesis of chiral compound B becomes difficult. On the other hand, if the number of carbon atoms is less than the above range, the ferroelectric liquid crystal composition may not exhibit a smectic phase.

In the above formulas (2-3) to (2-6) and (2-7) to (2-10), R ¹² is a saturated or unsaturated alkyl group having 1 to 10 carbon atoms. The alkyl group is linear, branched or cyclic. Among them, R ¹² is preferably a linear or branched saturated alkyl group or a phenylalkyl group.

In the above formulas (2-4), (2-6), (2-8), and (2-10), m is 0 or 1.
In the above formulas (2-3) to (2-6) and (2-7) to (2-10), * indicates a chiral center. In the above formulas (2-3), (2-5), (2-7), and (2-9), the carbon atom at the 1-position is a chiral center. In the above formulas (2-4), (2-6), (2-8), and (2-10), when m = 0, the carbon atom at the 1-position becomes a chiral center, and when m = 1, 2 The carbon atom at the position becomes the chiral center.

In the above formulas (2-3) to (2-6), X ^{31 to} X ³³ each independently represent —CH ₃ , —CF ₃ or a halogen atom. Among them, —CH ₃ , a fluorine atom or a chlorine atom is preferable, and —CH ₃ or a fluorine atom is particularly preferable.
The positions of X ^{31 to} X ³³ are the same as the positions of X ^{9 to} X ²⁰ described above.

  The chiral compound B represented by the above formulas (2-3), (2-5), (2-7), and (2-9) is easily polarized because the chiral moiety has an ester bond. On the other hand, the chiral compound B represented by the above (2-4), (2-6), (2-8), and (2-10) is relatively polarized because the chiral site does not have an ester bond. Hateful.

  Specific examples of the chiral compound B represented by the above formulas (2-3) to (2-6) include a chiral compound B represented by the following formula. In the following formula, dextrorotatory property is represented by (+) and levorotatory property is represented by (−).

  Specific examples of the chiral compound B represented by the above formulas (2-7) to (2-10) include a chiral compound B represented by the following formula. In addition, dextrorotatory property is indicated by (+) and levorotatory property is indicated by (−).

As such a chiral compound B, 1 type may be used independently and 2 or more types may be mixed and used for it.
For example, the ferroelectric liquid crystal composition may contain a chiral compound B represented by the above formula (2-1) and a chiral compound B represented by the above formula (2-2).

  The chiral compound B can be synthesized, for example, by the method described in International Publication No. 2010/031431.

(3) Chiral compound I and chiral compound II
The ferroelectric liquid crystal composition of the present invention only needs to contain at least one of chiral compound A and chiral compound B as dextrorotatory chiral compound I. For example, it contains only chiral compound A. It may contain only chiral compound B, and may contain chiral compound A and chiral compound B. Further, when the ferroelectric liquid crystal composition contains the chiral compound A as the dextrorotatory chiral compound I, it may contain one kind of chiral compound A or two or more kinds of chiral compounds A. May be. Similarly, when the ferroelectric liquid crystal composition contains the chiral compound B as the dextrorotatory chiral compound I, it may contain one kind of chiral compound B and contain two or more kinds of chiral compounds B. It may be.

  Further, the ferroelectric liquid crystal composition of the present invention only needs to contain at least one of the chiral compound A and the chiral compound B as the levorotatory chiral compound II. For example, the ferroelectric liquid crystal composition contains only the chiral compound A. Alternatively, only chiral compound B may be contained, or chiral compound A and chiral compound B may be contained. Further, when the ferroelectric liquid crystal composition contains the chiral compound A as the levorotatory chiral compound II, it may contain one kind of chiral compound A or two or more kinds of chiral compounds A. Also good. Similarly, when the ferroelectric liquid crystal composition contains the chiral compound B as the left-handed chiral compound II, it may contain one type of chiral compound B or two or more types of chiral compound B. May be.

  The dextrorotatory chiral compound I and the levorotatory chiral compound II may have the same or different molecular structures. When the molecular structures are identical, dextrorotatory chiral compound I and levorotatory chiral compound II are enantiomers. Among them, it is preferable that the dextrorotatory chiral compound I and the levorotatory chiral compound II have different molecular structures. When the molecular structures are different, it is possible to relax a molecular arrangement that is too regular due to the influence of the three-dimensional structure of the chiral compound, and a further improvement in scratch resistance can be expected. In addition, when the molecular structure of the dextrorotatory chiral compound I and that of the levorotatory chiral compound II are different, it can be expected that the control of the magnitude of the spontaneous polarization becomes easy.

  In order to change the molecular structure of the chiral compound, for example, the structure of the core part may be different, the substituent of the core part may be different, or the structure of the chiral part may be different.

  For example, when the structure of the core part of the chiral compound is different, the structure of the core part is obtained by setting one of the dextrorotatory chiral compound I and the levorotatory chiral compound II as the chiral compound A and the other as the chiral compound B. Can be different. Chiral compound A has a core part directly bonded with three benzene rings and one cyclohexane ring, and chiral compound B has a core part directly bonded with four benzene rings. The benzene ring has a planar structure, whereas the cyclohexane ring has a three-dimensional structure, so it is assumed that the molecular arrangement is too regular. Therefore, when one of the dextrorotatory chiral compound I and the levorotatory chiral compound II is the chiral compound A containing a cyclohexane ring and the other is the chiral compound B, the scratch resistance can be improved. . In this case, impact resistance can also be improved.

  Further, when the structure of the core portion of the chiral compound is different, one of the dextrorotatory chiral compound I and the levorotatory chiral compound II has one of the four benzene rings represented by the above formula (2-1) directly. A chiral compound B1 having a bonded core part, and the other being a chiral compound B2 having a core part directly bonded to four benzene rings and one cyclohexane ring represented by the above formula (2-2) Thereby, the structure of a core part can be varied. As described above, when one of the dextrorotatory chiral compound I and the levorotatory chiral compound II is a chiral compound B1 not containing a cyclohexane ring and the other is a chiral compound B2 containing a cyclohexane ring, Molecular order that is too regular is relaxed, and scratch resistance can be improved. In this case, impact resistance can also be improved.

  When the substituents in the core part of the chiral compound are different, the three-dimensional structure of the chiral compound is distorted depending on the size of the substituent, and this distortion relaxes the molecular arrangement that is too regular, thus increasing the scratch resistance. It is considered possible.

  On the other hand, if the structure of the chiral moiety is different, one of the dextrorotatory chiral compound I and the levorotatory chiral compound II is a chiral compound having a chiral moiety containing an ester bond, and the other is a chiral moiety not containing an ester bond. By using a chiral compound, the structure of the chiral site can be varied. A chiral compound having a chiral moiety containing an ester bond is easily polarized, and a chiral compound having a chiral moiety not containing an ester bond is relatively difficult to polarize. Therefore, by adding a chiral compound that has a chiral moiety containing an ester bond and is easily polarized to a chiral compound that has a chiral moiety that does not contain an ester bond, is not easily polarized, and has a reverse optical rotation, Subtle adjustment of polarization is possible.

If the structures of the chiral sites are different, one of the dextrorotatory chiral compound I and the levorotatory chiral compound II is a chiral compound in which the chiral site Y ¹ is a methyl group, and the other is a chiral site Y ^1. By using a chiral compound that is a fluorine atom, the structure of the chiral site can be varied. Chiral compounds in which Y ^{1 at the} chiral site is a fluorine atom are easily polarized. Therefore, by adding a chiral compound in which the chiral moiety Y ¹ is a fluorine atom and easily polarized, and the chiral moiety Y ¹ is a methyl group and the optical rotation is in the reverse direction, the spontaneous polarization is increased. Can be adjusted.

  The ferroelectric liquid crystal composition of the present invention preferably contains, as dextrorotatory chiral compound I or levorotatory chiral compound II, a chiral compound having a chiral moiety containing at least an ester bond. As described above, since a chiral compound having a chiral moiety containing an ester bond is easily polarized, spontaneous polarization tends to increase when the ferroelectric liquid crystal composition contains a chiral compound having a chiral moiety containing an ester bond. It is in. On the other hand, in the present invention, since a chiral compound having an optical rotation in the reverse direction is contained, effective spontaneous polarization can be reduced.

  When it is desired to increase the impact resistance, the ferroelectric liquid crystal composition of the present invention preferably contains at least the chiral compound A. As described above, when the ferroelectric liquid crystal composition contains the chiral compound A containing a cyclohexane ring, the molecular order that is too regular is relaxed and the impact resistance can be improved.

  When it is desired to improve impact resistance, the ferroelectric liquid crystal composition of the present invention is a chiral compound in which four benzene rings and one cyclohexane ring represented by the above formula (2-2) are directly bonded. It is also preferable to contain at least B2. As described above, when the ferroelectric liquid crystal composition contains the chiral compound B2 containing a cyclohexane ring, the molecular order that is too regular is relaxed, and the impact resistance can be improved.

The content of the dextrorotatory chiral compound I and the content of the levorotatory chiral compound II include the ease of polarization of the chiral compound I and chiral compound II, and the spontaneous polarization of the target ferroelectric liquid crystal composition. It is adjusted appropriately according to the size.
For example, when the molecular structures of the dextrorotatory chiral compound I and the levorotatory chiral compound II are the same, the ease of polarization of the chiral compound I and the chiral compound II is equal. Therefore, the magnitude of the spontaneous polarization can be adjusted by increasing the content of one of the dextrorotatory chiral compound I and the levorotatory chiral compound II and decreasing the content of the other.
In addition, among the dextrorotatory chiral compound I and the levorotatory chiral compound II, when one is a readily polarizable chiral compound and the other is a nonpolarizable chiral compound, the content of the easily polarizable chiral compound is increased. By reducing the content of chiral compounds that are difficult to polarize, the magnitude of spontaneous polarization can be adjusted.

  Of the content of the dextrorotatory chiral compound I and the content of the levorotatory chiral compound II in the ferroelectric liquid crystal composition, either one is preferably 5% by mass or more, and more preferably 5% by mass to It is preferable to be in the range of 35% by mass, particularly in the range of 15% by mass to 30% by mass. This is because, if the content of either one is less than the above range, desired impact resistance and spontaneous polarization may not be obtained. On the other hand, if the content is higher than the above range, the ferroelectric liquid crystal composition may have a high viscosity or be easily crystallized, so that sufficient impact resistance may not be obtained. This is because it may be difficult to form a liquid crystal layer when manufacturing an element.

  The total content of dextrorotatory chiral compound I and levorotatory chiral compound II in the ferroelectric liquid crystal composition is not particularly limited as long as desired impact resistance and spontaneous polarization can be obtained. It is preferably in the range of 5% by mass to 35% by mass, and more preferably in the range of 15% by mass to 30% by mass. This is because if the total content of the chiral compound I and the chiral compound II is less than the above range, desired impact resistance and spontaneous polarization may not be obtained. In addition, if the total content of chiral compound I and chiral compound II is larger than the above range, the ferroelectric liquid crystal composition has a high viscosity and is easily crystallized, thereby obtaining sufficient impact resistance. This is because the formation of a liquid crystal layer may be difficult when a liquid crystal display element is manufactured.

  When the ferroelectric liquid crystal composition of the present invention contains the chiral compound A and the chiral compound B, the content of the chiral compound B in the ferroelectric liquid crystal composition is the content of the chiral compound A from the viewpoint of driving characteristics. The above is preferable. Since the chiral compound A has a tendency to reduce the tilt angle of the liquid crystal molecules when a voltage is applied as compared with the chiral compound B, if the content of the chiral compound A is increased compared to the chiral compound B, the liquid crystal molecules There is a possibility that the tilt angle becomes small and sufficient brightness cannot be obtained. On the other hand, since the chiral compound B is contained in a larger amount than the chiral compound A, the tilt angle of the liquid crystal molecules can be increased, and the driving characteristics can be improved.

  The ferroelectric liquid crystal composition of the present invention contains only the chiral compound B, and the chiral compound B1 in which the four benzene rings represented by the above formula (2-1) are directly bonded to the above compound In the case of containing the chiral compound B2 in which four benzene rings and one cyclohexane ring represented by the formula (2-2) are directly bonded, the chirality in the ferroelectric liquid crystal composition from the viewpoint of driving characteristics The content of compound B1 is preferably not less than the content of chiral compound B2. Since the chiral compound B2 has a tendency to reduce the tilt angle of the liquid crystal molecules when a voltage is applied as compared with the chiral compound B1, if the content of the chiral compound B2 is increased compared to the chiral compound B1, the liquid crystal molecules There is a possibility that the tilt angle becomes small and sufficient brightness cannot be obtained. On the other hand, since the chiral compound B1 is contained in a larger amount than the chiral compound B2, the tilt angle of the liquid crystal molecules can be increased, and the driving characteristics can be improved.

2. Host Liquid Crystal The ferroelectric liquid crystal composition of the present invention contains a host liquid crystal in addition to the above chiral compound I and chiral compound II.

As the host liquid crystal, those generally used as the host liquid crystal of the ferroelectric liquid crystal composition can be used, and examples thereof include a phenylpyrimidine compound.
A host liquid crystal may be used individually by 1 type, and 2 or more types may be mixed and used for it.

The phenylpyrimidine compound used as the host liquid crystal is a bicyclic compound having one pyrimidine ring and one benzene ring, a tricyclic compound having one pyrimidine ring and two benzene rings, and one pyrimidine. Any of a tricyclic compound having a ring, one benzene ring, and one cyclohexane ring may be used.
Especially, as a phenyl pyrimidine compound, it is preferable to mix the said tricyclic compound with the said bicyclic compound. As the phenylpyrimidine compound, when the tricyclic compound is mixed with the bicyclic compound rather than using only the bicyclic compound, the phase transition temperature of the chiral smectic C phase of the ferroelectric liquid crystal composition is increased. This is because the usable range is widened when used for a display element.
Furthermore, among the tricyclic compounds, it is preferable to use a tricyclic compound having one pyrimidine ring, one benzene ring, and one cyclohexane ring. When a tricyclic compound having one pyrimidine ring, one benzene ring, and one cyclohexane ring was used, a tricyclic compound having one pyrimidine ring and two benzene rings was used. This is because, since the conjugated system is shorter than the case, the birefringence of the ferroelectric liquid crystal composition is reduced, so that it can be used with a wider cell gap when applied to a liquid crystal display element.

  The content of the host liquid crystal in the ferroelectric liquid crystal composition is not particularly limited as long as the content of the chiral compound can be within the above range.

3. Ferroelectric liquid crystal composition The ferroelectric liquid crystal composition of the present invention has spontaneous polarization. Note that “having spontaneous polarization” means that the spontaneous polarization is not zero. The spontaneous polarization of the ferroelectric liquid crystal composition may not be 0, but is preferably ² nC / cm ² or more, and preferably in the range of 3 nC / cm ^{2 to} 15 nC / cm ² . If the spontaneous polarization is within the above range, stable driving and high-speed response can be realized at a low voltage.

The ferroelectric liquid crystal composition of the present invention is not particularly limited as long as it exhibits a chiral smectic C (SmC ^* ) phase. Examples of the phase series of the ferroelectric liquid crystal composition include those in which the phase changes between a nematic (N) phase, a cholesteric (Ch) phase, a chiral smectic C (SmC ^* ) phase, and a nematic (N) phase-chiral. Phase change with smectic C (SmC ^* ) phase, Nematic (N) phase-Smectic A (SmA) phase-Chiral smectic C (SmC ^* ) phase change, Nematic (N) phase-Cholesteric (Ch) Examples include a phase-smectic A (SmA) phase-a chiral smectic C (SmC ^* ) phase and a phase change.

  In addition, as the ferroelectric liquid crystal composition, either one showing bistability or one showing monostability can be used. Among these, a ferroelectric liquid crystal composition exhibiting monostability is preferable. When a ferroelectric liquid crystal composition exhibiting monostability is used, gradation display is achieved by continuously changing the director of the liquid crystal (inclination of the molecular axis) by changing the voltage and analog-modulating the transmitted light intensity. This is because it becomes possible. In particular, when the liquid crystal display element is driven by a field sequential color system, it is preferable to use a ferroelectric liquid crystal composition exhibiting monostability. By using a ferroelectric liquid crystal composition exhibiting monostability, it becomes possible to drive by an active matrix method using TFTs, and also to control gradation by voltage modulation, so that high-definition and high-quality display is possible. This is because it can be realized.

  Note that “showing monostability” means a state in which the state of liquid crystal molecules when no voltage is applied is stabilized in one state. In the ferroelectric liquid crystal composition, as illustrated in FIG. 1, the liquid crystal molecules 25 are tilted from the layer normal z and rotate along a cone ridge having a bottom surface perpendicular to the layer normal z. . In such a cone, the tilt angle of the liquid crystal molecules 25 with respect to the layer normal z is referred to as a tilt angle θ. Thus, the liquid crystal molecules 25 can operate on the cone between two states inclined by a tilt angle ± θ with respect to the layer normal z. Specifically, the expression of monostability refers to a state in which the liquid crystal molecules 25 are stabilized in any one state on the cone when no voltage is applied.

  In addition, the ferroelectric liquid crystal composition only needs to exhibit monostability, and exhibits a half V-shaped switching characteristic in which liquid crystal molecules operate only when a positive or negative voltage is applied. A V-shaped switching characteristic in which liquid crystal molecules operate to the same degree with respect to voltage, asymmetric switching in which the operation of liquid crystal molecules for either positive or negative voltage is larger than the operation of liquid crystal molecules for the other polarity voltage Any of those exhibiting properties can be used.

Such a ferroelectric liquid crystal composition can be variously selected from generally known liquid crystal materials according to required characteristics. In particular, the ferroelectric liquid crystal composition that expresses the SmC ^* phase from the Ch phase without passing through the SmA phase is preferable because the change in the operating characteristics with respect to the voltage is small with respect to the temperature change.

B. Liquid crystal display element The liquid crystal display element of the present invention includes a first base material, a first electrode layer formed on the first base material, and a first alignment film formed on the first electrode layer. A second alignment treatment substrate having a first alignment treatment substrate, a second base material, a second electrode layer formed on the second base material, and a second alignment film formed on the second electrode layer; A liquid crystal display element formed between the first alignment film and the second alignment film and having a liquid crystal layer containing a ferroelectric liquid crystal composition having spontaneous polarization, wherein the ferroelectric liquid crystal composition comprises: , At least one of the chiral compound A represented by the formula (1) and the chiral compound B represented by the formula (2), a dextrorotatory chiral compound I, the chiral compound A, and the chiral compound At least one of B and containing levorotatory chiral compound II It is characterized by that.

The liquid crystal display element of the present invention will be described with reference to the drawings.
FIG. 2 is a cross-sectional view showing an example of the liquid crystal display element of the present invention. As illustrated in FIG. 2, the liquid crystal display element 1 is formed on the first base material 2a, the first electrode layer 3a formed on the first base material 2a, and the first electrode layer 3a. The first alignment processing substrate 11a having the first alignment film 4a, the second base material 2b, the second electrode layer 3b formed on the second base material 2b, and the second electrode layer 3b A second alignment treatment substrate 11b having a second alignment film 4b; and a liquid crystal layer 5 formed between the first alignment film 4a and the second alignment film 4b. It contains a ferroelectric liquid crystal composition.

According to the present invention, since the liquid crystal layer contains the above-described ferroelectric liquid crystal composition, it is possible to obtain a liquid crystal display element having excellent impact resistance, alignment characteristics, and driving characteristics, and excellent scratch resistance. .
Hereinafter, each structure in the liquid crystal display element of this invention is demonstrated.

1. Liquid Crystal Layer The liquid crystal layer in the present invention is formed between the first alignment film of the first alignment treatment substrate and the second alignment film of the second alignment treatment substrate, and the chiral compound A represented by the above formula (1) and the above At least one of the chiral compounds B represented by the formula (2), and a dextrorotatory chiral compound I; and at least one of the above chiral compound A and the above chiral compound B, and a levorotatory chiral compound II; And a ferroelectric liquid crystal composition having spontaneous polarization.
The ferroelectric liquid crystal composition has been described in detail in the above section “A. Ferroelectric liquid crystal composition”, and thus the description thereof is omitted here.

  The thickness of the liquid crystal layer is preferably in the range of 1.0 μm to 10.0 μm, more preferably in the range of 1.3 μm to 5.0 μm, and still more preferably in the range of 1.4 μm to 3.5 μm. is there. If the thickness of the liquid crystal layer is too thin, defects may be noticeable due to the inclusion of foreign substances during manufacturing. Conversely, if the thickness of the liquid crystal layer is too thick, the liquid crystal molecules may be difficult to align and the contrast may be reduced. is there. The thickness of the liquid crystal layer can be adjusted by a bead spacer, a columnar spacer, a partition wall, or the like.

As a method for forming the liquid crystal layer, a method generally used as a method for manufacturing a liquid crystal cell can be used. For example, a vacuum injection method, a liquid crystal dropping method, or the like can be used.
In the vacuum injection method, for example, first, a ferroelectric liquid crystal composition made into an isotropic liquid by heating is applied to a liquid crystal cell that has been prepared using a first alignment treatment substrate and a second alignment treatment substrate in advance. Inject using the effect. Next, a liquid crystal layer can be formed by sealing the liquid crystal cell into which the ferroelectric liquid crystal is injected with an adhesive.
In the liquid crystal dropping method, for example, first, a heated ferroelectric liquid crystal composition is dropped or applied onto the second alignment film of the second alignment processing substrate. Next, a sealant is applied to the peripheral portion of the first alignment processing substrate. Subsequently, a liquid crystal layer can be formed by stacking the first alignment treatment substrate and the second alignment treatment substrate under reduced pressure and bonding them with a sealant.

  When aligning the ferroelectric liquid crystal composition, it may be cooled slowly, and it is not necessary to apply a voltage to the liquid crystal layer.

2. 1st orientation processing board The 1st orientation processing board used for the present invention is the 1st base material, the 1st electrode layer formed on the 1st base material, and the 1st orientation formed on the 1st electrode layer. And a film.
Hereinafter, each structure in a 1st orientation processing board | substrate is demonstrated.

(1) 1st alignment film The 1st alignment film used for this invention will not be specifically limited if the alignment control of a ferroelectric liquid-crystal composition is possible, For example, a photo-alignment film, a rubbing alignment Examples thereof include a film and an oblique deposition alignment film. Hereinafter, these alignment films will be described.

(A) Photo-alignment film The photo-alignment film is useful in that since the photo-alignment process is a non-contact alignment process, there is no generation of static electricity or dust, and the quantitative alignment process can be controlled.
The materials used for the photo-alignment film are large, photoreactive materials that impart anisotropy to the film by causing a photoreaction, and photoisomerism that imparts anisotropy to the film by causing a photoisomerization reaction. It can be divided into chemical materials. In the following, description will be made separately for photoreactive materials and photoisomerizable materials.

(Photoreactive material)
The photoreactive material may be a photodimerization material that imparts anisotropy to the film by causing a photodimerization reaction or a photodegradable material that imparts anisotropy to the film by causing a photodecomposition reaction. preferable. Among these, a photodimerization type material is more preferable because of high exposure sensitivity and wide range of material selection.

  Examples of the photodimerization type material and the photolysis type material include those described in JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428, and the like. Can be used.

  The photodimerization reactive compound used for the photodimerization-type material is preferably a dimerization reactive polymer containing any of cinnamic acid ester, coumarin or quinoline as a side chain.

  As the photodimerization reactive compound, various photodimerization reaction sites and substituents can be selected from the above compounds according to the required properties. Moreover, the photodimerization reactive compound can also be used individually by 1 type or in combination of 2 or more types.

  Further, the photodimerization type material may contain an additive in addition to the photodimerization reactive compound as long as the photoalignment of the alignment film is not hindered. Examples of the additive include a polymerization initiator and a polymerization inhibitor.

(Photoisomerization type material)
As the photoisomerization type material, for example, those described in JP-A-2006-350322, JP-A-2006-323214, JP-A-2005-258429, JP-A-2005-258428 are used. it can.

The photoisomerization reaction that produces the photoisomerizable material is preferably a cis-trans isomerization reaction. The photoisomerization reactive compound used for the photoisomerization type material is preferably a compound having an azobenzene skeleton in the molecule.
Examples of photoisomerization-reactive compounds include monomolecular compounds and polymerizable monomers. Among them, the anisotropy is stabilized by polymerizing after imparting anisotropy to the film by light irradiation. In view of this, a polymerizable monomer is preferable. Among the polymerizable monomers, an acrylate monomer and a methacrylate monomer are preferable because they can be easily polymerized while anisotropy is imparted to the film and the anisotropy is maintained in a good state.

  From such photoisomerization-reactive compounds, various cis-trans isomerization-reactive skeletons and substituents can be selected according to required characteristics. In addition, a photoisomerization reactive compound can also be used individually by 1 type or in combination of 2 or more types.

  In addition to the photoisomerization reactive compound, the photoisomerization type material may contain an additive within a range that does not interfere with the photoalignment of the alignment film. When a polymerizable monomer is used as the photoisomerization reactive compound, examples of the additive include a polymerization initiator and a polymerization inhibitor.

(Photo-alignment film)
The wavelength region of light in which the material used for the photo-alignment film undergoes a photoexcitation reaction (photodimerization, photolysis, photoisomerization) is preferably in the ultraviolet range, that is, in the range of 10 nm to 400 nm, 250 nm More preferably, it is in the range of ˜380 nm.

As a method for forming the photo-alignment film, a general method can be used.
The thickness of the photo-alignment film is preferably in the range of 1 nm to 1000 nm, more preferably in the range of 3 nm to 100 nm. If the thickness of the photo-alignment film is smaller than the above range, sufficient optical alignment may not be obtained. Conversely, if the thickness of the photo-alignment film is larger than the above range, the cost may be disadvantageous. is there.

(B) Rubbing alignment film The rubbing alignment film is useful in that a relatively high pretilt angle can be realized.
As materials and forming methods used for the rubbing alignment film, general materials can be applied.
The thickness of the rubbing alignment film is set to about 1 nm to 1000 nm, and preferably in the range of 50 nm to 100 nm.

(C) Oblique deposition alignment film The oblique deposition alignment film is formed by an oblique deposition method. The oblique deposition film is useful in that a relatively high pretilt angle can be realized.
As materials and forming methods used for the oblique deposition alignment film, general materials can be applied. As for the oblique deposition alignment film, “Liquid Crystal Handbook” edited by the Liquid Crystal Handbook Editorial Committee Maruzen Co., Ltd. October 30, 2000 p. Reference may be made to 229-230.
The thickness of the oblique deposition alignment film is set to about 10 nm to 500 nm, and preferably in the range of 30 nm to 200 nm.

(D) Composition of constituent materials of first alignment film and second alignment film In the present invention, it is preferable that the constituent materials of the first alignment film and the second alignment film have different compositions with the liquid crystal layer interposed therebetween. By forming the first alignment film and the second alignment film using materials having different compositions, the polarities of the first alignment film surface and the second alignment film surface can be made different depending on the respective materials. As a result, the polar surface interaction between the ferroelectric liquid crystal composition and the first alignment film is different from the polar surface interaction between the ferroelectric liquid crystal composition and the second alignment film. By appropriately selecting the material in consideration of the surface polarity of the second alignment film, it is possible to suppress the occurrence of alignment defects such as zigzag defects, hairpin defects, and two types of domains having different stable states of liquid crystal molecules when no voltage is applied. Because it can. As a result, contrast can be improved.

In order to make the constituent materials of the first alignment film and the second alignment film have different compositions across the liquid crystal layer, for example, one may be a photo-alignment film and the other a rubbing alignment film.
Also, for example, both are rubbed alignment films, and the composition of the constituent materials of the rubbing alignment film are different; both are the photo-alignment films, and the compositions of the constituent materials of the photo-alignment film are different; As the alignment film, the composition of the constituent materials of the oblique deposition alignment film may be different.

  When the first alignment film and the second alignment film are rubbing alignment films, the composition can be changed by changing the amount of the additive added or by the presence or absence of the additive.

Further, when the first alignment film and the second alignment film are photo-alignment films, for example, by using a photoisomerizable material for one photo-alignment film and a photo-reactive material for the other photo-alignment film, The composition of the constituent material of the alignment film can be different.
Furthermore, when the first alignment film and the second alignment film are photo-alignment films using a photoisomerization type material, cis-trans isomerization reactivity is selected from photoisomerization-reactive compounds according to required characteristics. By selecting various skeletons and substituents, the composition of the constituent materials of the photo-alignment film can be made different. Further, the composition can be changed by changing the amount of additive added or by the presence or absence of the additive.
Furthermore, when the first alignment film and the second alignment film are photo-alignment films using a photo-dimerization-type material, by selecting various photo-dimerization reactive compounds, for example, photo-dimerization-reactive polymers, The composition of the constituent materials can be different. Further, the composition can be changed by changing the amount of additive added or by the presence or absence of the additive.

(2) First electrode layer The first electrode layer used in the present invention is not particularly limited as long as it is generally used as an electrode of a liquid crystal display element. At least one of the electrode layer and the second electrode layer of the second alignment treatment substrate is preferably formed of a transparent conductor. Preferred examples of the transparent conductor material include indium oxide, tin oxide, indium tin oxide (ITO), and the like.

  When the liquid crystal display element of the present invention is driven by an active matrix method using TFTs, one of the first alignment processing substrate and the second alignment processing substrate is provided with a whole surface common electrode formed of the transparent conductor. On the other side, a gate electrode and a source electrode are arranged in a matrix, and a TFT element and a pixel electrode are provided in a portion surrounded by the gate electrode and the source electrode.

  Examples of the method for forming the first electrode layer include chemical vapor deposition (CVD), physical vapor deposition (PVD) such as sputtering, ion plating, and vacuum deposition.

(3) 1st base material The 1st base material used for this invention will not be specifically limited if generally used as a base material of a liquid crystal display element, For example, a glass plate, a plastic plate, etc. are preferable. Can be mentioned.

(4) Other Configurations In the first alignment treatment substrate in the present invention, partition walls or columnar spacers may be formed on the first base material. When the partition or columnar spacer is formed on the second base material in the second alignment processing substrate, the partition or columnar spacer is not formed on the first base material in the first alignment processing substrate. That is, partition walls or columnar spacers may be formed on the first alignment processing substrate, and partition walls or columnar spacers may be formed on the second alignment processing substrate.
As the partition walls and columnar spacers, general partition walls and columnar spacers can be applied.

  Moreover, in the 1st orientation processing board | substrate in this invention, the colored layer may be formed on the 1st base material. When the colored layer is formed on the second base material in the second alignment processing substrate, the coloring layer is not formed on the first base material in the first alignment processing substrate. That is, a colored layer may be formed on the first alignment processing substrate, and a coloring layer may be formed on the second alignment processing substrate.

  When the colored layer is formed, a color filter type liquid crystal display element capable of realizing color display by the colored layer can be obtained.

  As a method for forming the colored layer, a method for forming a colored layer in a general color filter can be used. For example, a pigment dispersion method (color resist method, etching method), a printing method, an inkjet method, or the like can be used. it can.

3. Second alignment treatment substrate The second alignment treatment substrate used in the present invention includes a second base material, a second electrode layer formed on the second base material, and a second orientation formed on the second electrode layer. And a film.

  In addition, about a 2nd base material, a 2nd electrode layer, a 2nd orientation film, and other structures, with the 1st base material in a said 1st orientation processing board | substrate, a 1st electrode layer, a 1st orientation film, and another structure, respectively. Since it is the same, description here is abbreviate | omitted.

4). Other Configurations The liquid crystal display element of the present invention may have a polarizing plate.
The polarizing plate used in the present invention is not particularly limited as long as it transmits only a specific direction among the wave of light, and a polarizing plate generally used as a polarizing plate of a liquid crystal display element should be used. Can do.

5. Method for driving liquid crystal display element As a method for driving the liquid crystal display element of the present invention, the high-speed response of the ferroelectric liquid crystal composition can be used. Therefore, it can be suitably used for a field sequential color system that requires high-speed response.

  Further, the driving method of the liquid crystal display element of the present invention is not limited to the field sequential method, and may be a color filter method that performs color display using a colored layer.

  As a driving method of the liquid crystal display element of the present invention, an active matrix system using a thin film transistor (TFT) is preferable. This is because by adopting an active matrix system using TFTs, the target pixel can be reliably turned on and off, and a high-quality display becomes possible.

  Further, the driving method of the liquid crystal display element of the present invention may be a segment method.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Example 1]
(Ferroelectric liquid crystal composition)
As shown in Table 1 below, a ferroelectric liquid crystal composition was prepared.

(Production of liquid crystal display element)
First, a resin spacer having a circular shape of Φ5.0 μm and a height of 2.5 μm was formed on an ITO-coated glass substrate 1 at a pitch of 0.1 mm. Subsequently, a rubbing alignment film material (SE610: Nissan Chemical Industries, Ltd.) was spin-coated at a rotation speed of 1500 rpm for 30 seconds. Thereafter, the substrate was dried in an oven at 180 ° C. for 30 minutes, and then rubbed.

  Further, a solution of a photoisomerization type photo-alignment film material (LIA03: DIC Corporation) was spin-coated on an ITO-coated glass substrate 2 at 1500 rpm for 30 seconds. Thereafter, after drying in an oven at 100 ° C. for 3 minutes, 2J-polarized exposure processing was performed with a polarizing exposure machine.

  Next, a sealing material was applied in a square frame shape on the substrate. On the substrate, the above-described ferroelectric liquid crystal composition was applied in the form of dots, and the two substrates were assembled and pressure-bonded so that the rubbing treatment direction and the polarization treatment direction were perpendicular. Next, the liquid crystal cell is heated to a temperature at which the ferroelectric liquid crystal composition exhibits a nematic phase, and after confirming that the ferroelectric liquid crystal composition has spread, it is cooled to room temperature to align the ferroelectric liquid crystal composition. I let you.

(Evaluation)
1) Spontaneous polarization Spontaneous polarization uses a liquid crystal property evaluation apparatus (manufactured by Toyo Technica Co., Ltd.) to apply a triangular wave (100 Hz) of 0 to 10 V to the liquid crystal display element. Determined by measurement. As the spontaneous polarization value, a value of 1/2 of the area was used.

2) Impact resistance The obtained liquid crystal display element was subjected to an impact resistance test. In the impact resistance test, a push-up scale (FB-30N: manufactured by Imada) was used, and a change in liquid crystal alignment was observed when a load of 5 N was applied with a push area of 1.3 cm ² . When the liquid crystal alignment did not change after applying a 5N load, it was evaluated as “◯”, and when the alignment did not change when a 5N load was applied, it was evaluated as “×”.

3) Tilt angle The angle at which the liquid crystal molecules moved was measured with a polarizing microscope. A liquid crystal cell filled with a ferroelectric liquid crystal composition is placed between two polarizing plates set in a crossed Nicol state, and a positive voltage (10 V) and a negative voltage are based on the position of black display when no voltage is applied. The angle of the liquid crystal molecules that moved when (-10 V) was applied was measured. Here, the tilt angle is the sum of the angle of movement of the liquid crystal molecules when a positive voltage is applied and the angle of movement of the liquid crystal molecules when a negative voltage is applied.

4) Orientation The orientation of the liquid crystal was observed with a polarizing microscope. A liquid crystal cell filled with a ferroelectric liquid crystal composition was placed between two polarizing plates set in a crossed Nicol state, and the alignment state when no voltage was applied was confirmed. When no voltage was applied, the liquid crystal molecules aligned in one direction were marked with “◯”, those with two domains and zigzag defects were marked with “x”.

5) Scratch resistance The resulting liquid crystal display element was subjected to a scratch test. In the scratch test, a 3-inch liquid crystal display element was scratched with a pen, and the time for the scratch to disappear was measured.

6) Response speed The response speed is changed at the point where the amplitude reaches 10% with the amplitude of the amount of light transmitted through the liquid crystal display element being 100% when a square wave of ± 2.5 V and 60 Hz is applied by the waveform generator. The time from the start point to the end point was defined as the “response speed” and measured when the start point and the point at which the amplitude reached 90% were defined as the end point of the change.
The evaluation results are shown in Table 2.

No. 2 to which two kinds of chiral compounds having opposite optical rotations are added. Nos. 2 to 4 are No. 1 to which one kind of chiral compound is added. Compared with 1, the spontaneous polarization was reduced, the scratch resistance was improved, and the impact resistance, orientation characteristics and driving characteristics were all excellent.
In addition, No. No. 4 is a range in which the response speed is slightly slow due to the small spontaneous polarization, but does not affect the high-speed response in the liquid crystal display element using the ferroelectric liquid crystal composition.

[Example 2]
(Ferroelectric liquid crystal composition)
As shown in Table 3 below, a ferroelectric liquid crystal composition was prepared.

(Production of liquid crystal display element)
A liquid crystal display element was produced in the same manner as in Example 1.

(Evaluation)
In the same manner as in Example 1, spontaneous polarization, impact resistance, tilt angle, orientation, scratch resistance, and response speed were evaluated. The evaluation results are shown in Table 4.

  No. 2 in which two or more kinds of chiral compounds having optical rotations in opposite directions are added. Nos. 6 to 8 are Nos. In which two kinds of chiral compounds having the same optical rotation direction are added. Compared to 5, the spontaneous polarization was reduced, the scratch resistance was improved, and the impact resistance, the orientation characteristics, and the driving characteristics were all excellent.

[Example 3]
(Ferroelectric liquid crystal composition)
A ferroelectric liquid crystal composition was prepared as shown in Table 5 below.

(Production of liquid crystal display element)
A liquid crystal display element was produced in the same manner as in Example 1.

(Evaluation)
As in Example 1, spontaneous polarization, impact resistance, tilt angle, transmittance, orientation, scratch resistance, and response speed were evaluated. The evaluation results are shown in Table 6.

When the ferroelectric liquid crystal composition shown in Table 5 was used, the same results as in Example 1 were obtained.
In addition, when two or more kinds of chiral compounds each use a chiral compound having two fluorine atoms as a substituent, only one of the two or more kinds of chiral compounds has two fluorine atoms as a substituent. Compared with the case of using a chiral compound having, the tilt angle of liquid crystal molecules was widened.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2a ... 1st base material 2b ... 2nd base material 3a ... 1st electrode layer 3b ... 2nd electrode layer 4a ... 1st orientation film 4b ... 2nd orientation film 5 ... Liquid crystal layer 11a ... 1st orientation Treatment substrate 11b ... Second alignment treatment substrate 25 ... Liquid crystal molecules Ps ... Spontaneous polarization z ... Layer normal

Claims (2)

At least one of a chiral compound A represented by the following general formula (1) and a chiral compound B represented by the following general formula (2), and a dextrorotatory chiral compound I;
A ferroelectric liquid crystal composition comprising at least one of the chiral compound A and the chiral compound B and containing a left-handed chiral compound II and having spontaneous polarization.

(In the above formula (1), R ¹ is a non-chiral group and is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ² is a chiral group and is a group represented by the following general formula (3).

In (the formula (3), R ³ is an alkyl or alkoxyalkyl group of saturated or unsaturated 1 to 10 carbon atoms which may be substituted with a halogen atom.
Y ¹ represents —CH ₃ or a fluorine atom. m is 0 or 1. n is 0 or 1. * Indicates a chiral center. )
X ^{1 to} X ⁸ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{1 to} X ⁸ are each independently —CH ₃ , —CF ₃ or a halogen atom. )

(In the above formula (2), R ⁴ is an achiral group, which is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ⁵ is a chiral group, and is a group represented by the above formula (3).
X ^{9 to} X ²⁰ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{9 to} X ²⁰ are each independently —CH ₃ , —CF ₃ or a halogen atom.
K represents a single bond or a cyclohexane ring. ) A first alignment treatment substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment film formed on the first electrode layer;
A second substrate having a second substrate, a second electrode layer formed on the second substrate, and a second alignment film formed on the second electrode layer;
A liquid crystal display element comprising a ferroelectric liquid crystal composition having a spontaneous polarization formed between the first alignment film and the second alignment film,
The ferroelectric liquid crystal composition is at least one of a chiral compound A represented by the following general formula (1) and a chiral compound B represented by the following general formula (2). And a chiral compound II which is at least one of the chiral compound A and the chiral compound B and contains a levorotatory chiral compound II.

(In the above formula (1), R ¹ is a non-chiral group and is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ² is a chiral group and is a group represented by the following general formula (3).

In (the formula (3), R ³ is an alkyl or alkoxyalkyl group of saturated or unsaturated 1 to 10 carbon atoms which may be substituted with a halogen atom.
Y ¹ represents —CH ₃ or a fluorine atom. m is 0 or 1. n is 0 or 1. * Indicates a chiral center. )
X ^{1 to} X ⁸ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{1 to} X ⁸ are each independently —CH ₃ , —CF ₃ or a halogen atom. )

(In the above formula (2), R ⁴ is an achiral group, which is a saturated or unsaturated alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms which may be substituted with a halogen atom.
R ⁵ is a chiral group, and is a group represented by the above formula (3).
X ^{9 to} X ²⁰ each independently represent —CH ₃ , —CF ₃ , a halogen atom or a hydrogen atom. However, one or more of X ^{9 to} X ²⁰ are each independently —CH ₃ , —CF ₃ or a halogen atom.
K represents a single bond or a cyclohexane ring. )

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