JP2013067775A - Ferroelectric liquid crystal composition and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric liquid crystal composition which can obtain impact resistance when used in a liquid crystal display element.SOLUTION: The ferroelectric liquid crystal composition contains a chiral compound represented by formula (1) (wherein Ris a non-chiral group and is a 4-18C saturated or unsaturated alkyl group or an alkoxyalkyl group which is optionally substituted with a halogen; Ris a chiral group; and X-Xare each -CH, -CF, halogen or hydrogen provided that at least one of X-Xis -CH, -CFor a halogen).

Description

  The present invention relates to a liquid crystal display element using a ferroelectric liquid crystal composition having impact resistance.

  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).

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

According to Patent Document 6, when a ferroelectric liquid crystal composition containing a chiral compound having a predetermined structure in which four benzene rings are directly bonded is used, the contrast ratio is good even after an impact is applied. It has been reported that
On the other hand, Patent Document 6 discloses a chiral compound having a predetermined structure in which three or five benzene rings are directly bonded, but there is no detailed description of impact resistance. Furthermore, it was reported that when a ferroelectric liquid crystal composition containing a chiral compound having a predetermined structure in which three benzene rings were directly bonded was used, the contrast ratio deteriorated when an impact was applied. There is room for improvement in impact resistance.
In addition, when a ferroelectric liquid crystal composition containing a chiral compound having a predetermined structure in which four or five benzene rings are directly bonded is used, birefringence is increased, so that the cell gap is narrowed. Therefore, when the liquid crystal display element is used, the yield is deteriorated.
In order to improve the birefringence, it is desirable to use a chiral compound having a predetermined structure in which three benzene rings are directly bonded, but there is a concern that the impact resistance is poor as described above.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a ferroelectric liquid crystal composition capable of obtaining impact resistance when used in a liquid crystal display element.

  As a result of various studies on the impact resistance of a liquid crystal display device using a ferroelectric liquid crystal composition, the present inventors have determined a predetermined structure in which three benzene rings and one cyclohexane ring are directly bonded. It has been found that good impact resistance can be achieved when a ferroelectric liquid crystal composition containing a chiral compound having the above is used, and the present invention has been completed based on such findings.

  That is, the present invention provides a ferroelectric liquid crystal composition comprising a chiral compound represented by the following general 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.
R ² is a chiral group, and is a group represented by the following general formula (2).

In (above formula (2), 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. )

  Since the ferroelectric liquid crystal composition of the present invention contains the chiral compound represented by the above formula (1), high impact resistance can be achieved when used in a liquid crystal display device.

  In the said invention, it is preferable that content of the said chiral compound exists in the range of 5 mass%-35 mass%. This is because when the content of the chiral compound is within the above range, excellent impact resistance can be obtained when the ferroelectric liquid crystal composition of the present invention is used in a liquid crystal display device.

  In addition, the present invention provides a first alignment treatment substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment layer formed on the first electrode layer; A second substrate, a second electrode layer formed on the second substrate, a second alignment substrate having a second alignment layer formed on the second electrode layer, and the first alignment layer And a liquid crystal layer formed between the second alignment layers, wherein the liquid crystal layer contains the ferroelectric liquid crystal composition described above. To do.

  According to the present invention, since the liquid crystal layer contains the above-described ferroelectric liquid crystal composition, it is possible to improve impact resistance.

  In the above invention, the constituent material of the first alignment layer and the constituent material of the second alignment layer preferably have different compositions. This is because the occurrence of alignment defects can be suppressed and the contrast can be improved.

  In the present invention, since the ferroelectric liquid crystal composition contains a predetermined chiral compound, the liquid crystal display device using the ferroelectric liquid crystal composition has an effect that the impact 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 the graph which showed the change of the transmitted light quantity with respect to the applied voltage of a liquid crystal display element. It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention. It is a schematic diagram which shows the other example of the orientation state of the liquid crystal molecule in this invention. It is a schematic diagram which shows the other example of the orientation state of the liquid crystal molecule in this invention. It is a schematic diagram which shows the other example of the orientation state of the liquid crystal molecule in this invention. It is a schematic diagram which shows the spontaneous polarization of the liquid crystal molecule in this invention. It is a schematic diagram which shows the other example of the orientation state of the liquid crystal molecule in this invention. It is a schematic sectional drawing which shows the other example of the liquid crystal display element of this invention. It is a schematic perspective view which shows the other example of the liquid crystal display element of this invention. It is a schematic diagram which shows the other example of the orientation state of the liquid crystal molecule in this invention. It is a photograph for demonstrating evaluation of the application trace of the ferroelectric liquid-crystal composition in an Example. It is a photograph which shows an example of the liquid crystal display element of the example of this invention in an Example. It is a photograph which shows an example of the liquid crystal display element of the comparative example in an Example.

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

A. Ferroelectric liquid crystal composition The ferroelectric liquid crystal composition of the present invention is characterized by containing a chiral compound represented by the following general 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.
R ² is a chiral group, and is a group represented by the following general formula (2).

(In the above formula (2), R ³ is a saturated or unsaturated alkyl group or alkoxyalkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom. Y ¹ represents —CH ₃ or fluorine. Represents an 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. )

The benzene ring has a planar structure and is easily crystallized, but the cyclohexane ring has a three-dimensional structure and is presumed to inhibit crystallization. When the ferroelectric liquid crystal composition is easily crystallized, it is difficult to return to the original state when the impact is applied and the liquid crystal molecules move, resulting in poor impact resistance. On the other hand, in this invention, impact resistance can be improved by containing the above chiral compounds.
Hereinafter, each component in the ferroelectric liquid crystal composition of the present invention will be described.

1. Chiral compound The chiral compound used in the present invention is 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 becomes difficult and the cost increases. On the other hand, when the number of carbon atoms is less than the above range, the ferroelectric liquid crystal composition of the present invention 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 of the present invention may exhibit a smectic phase with a relatively small number of carbon atoms.
The alkyl group or alkoxyalkyl group may be substituted with a halogen atom or may not be substituted with a halogen atom, but is preferably 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 material changes due to long-term storage / driving and temperature changes, and the ferroelectric liquid crystal composition of the present invention This is because the display quality may be deteriorated when the is used for a liquid crystal display element.
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 (2).

In the above formula (2), R ³ is a saturated or unsaturated alkyl group or alkoxyalkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom.
The alkyl group or alkoxyalkyl group may be substituted with a halogen atom or may not 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 (2), 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 is easy. On the other hand, in the case of fluorine atoms, the spontaneous polarization of liquid crystal molecules increases, and there is an advantage that the response speed can be increased when the ferroelectric liquid crystal composition of the present invention is used in a liquid crystal display element.
Y ¹ may be —CH ₃ or a fluorine atom, and among them, —CH ₃ is preferable. This is because the chiral compound can be easily synthesized as described above, the chiral compound can be stably produced, and the ferroelectric liquid crystal composition can be obtained at a low cost.

In the above formula (2), m is 0 or 1.
In the above formula (2), * 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 (2), n is 0 or 1.

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 is lowered, so that the synthesis and purification of the chiral compound becomes difficult, the cost increases, and the ferroelectricity of the present invention The liquid crystal composition tends to be crystallized, and when used in a liquid crystal display element, 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 in the solvent is increased, resulting in a large-scale synthesis. Purification becomes possible. Further, since the steric structure of the chiral compound is distorted and the crystallization of the ferroelectric liquid crystal composition is inhibited 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.

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 the benzene ring is substituted symmetrically, the chiral smectic C phase is stabilized and the tilt angle of the liquid crystal molecules can be increased, so that 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 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). Can be mentioned.

(In the above formulas (1-1) to (1-2) and (1-3) to (1-4), R ⁴ 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 ¹¹ and X ¹² 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, synthesis of a chiral compound becomes difficult. On the other hand, when the number of carbon atoms is less than the above range, the ferroelectric liquid crystal composition of the present invention may not exhibit a smectic phase.

In the above formulas (1-1) to (1-2) and (1-3) to (1-4), R ⁴ is a saturated or unsaturated alkyl group having 1 to 10 carbon atoms. The alkyl group is linear, branched or cyclic. Among these, R ⁴ 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 ¹¹ and X ¹² 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 position of X ¹¹ and ^{X 12,} is the same as the position of the ^X 1 to X ⁸ as described above.

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

  Specific examples of the chiral compound represented by the above formulas (1-1) and (1-2) include a chiral compound represented by the following formula.

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

  As such a chiral compound, one kind may be used alone, or two or more kinds may be mixed and used.

  The content of the chiral compound in the ferroelectric liquid crystal composition is not particularly limited as long as an impact resistance effect is obtained. When one of the above chiral compounds is used alone, the content of the chiral compound is the same. When two or more of the above chiral compounds are mixed, the content of each of the two or more of the chiral compounds is the ferroelectric liquid crystal composition. The content is preferably 5% by mass or more. In particular, when one of the above chiral compounds is used alone, the content of the chiral compound is the same. When two or more of the above chiral compounds are mixed, the total content of the two or more chiral compounds is the ferroelectric liquid crystal. It is preferable that it is in the range of 5 mass%-35 mass% in a composition, and it is more preferable that it exists in the range of 15 mass%-30 mass%. This is because if the content of the chiral compound is less than the above range, desired impact resistance may not be obtained. On the other hand, if the content of the chiral compound is more than the above range, the ferroelectric liquid crystal composition may have a high viscosity or may be easily crystallized, and sufficient impact resistance may not be obtained. Moreover, it is because formation of a liquid crystal layer may become difficult when manufacturing a liquid crystal display element.

  A chiral compound is compoundable by the method as described in international publication 2010/031431, for example.

2. Host liquid crystal The ferroelectric liquid crystal composition of the present invention may contain a host liquid crystal in addition to the chiral compound.

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.

  Among them, the phenylpyrimidine compound used as the host liquid crystal is preferably a phenyl group substituted with a fluorine atom, and more preferably a phenyl group substituted with one or two fluorine atoms. . By using a phenylpyrimidine compound in which the phenyl group is substituted with a fluorine atom, the phase transition temperature of the chiral smectic C phase of the ferroelectric liquid crystal composition of the present invention is widened, so that the ferroelectric liquid crystal composition of the present invention is liquid crystal This is because, when used in a display element, the liquid crystal display element can be driven stably at low and high temperatures. Moreover, since the viscosity of the ferroelectric liquid crystal composition of the present invention is lowered, there is an advantage that the liquid crystal layer can be easily formed in the manufacturing process of the liquid crystal display element. Furthermore, when a ferroelectric liquid crystal composition is applied or dropped when a liquid crystal display device is produced by using a phenylpyrimidine compound in which the phenyl group is substituted with a fluorine atom, the coating mark and the dropping mark are not observed. Since it becomes difficult to occur, it is possible to prevent alignment disorder of liquid crystal molecules due to coating marks and dropping marks, and to suppress the occurrence of alignment defects. This is because the fluorine atom weakens the interaction between the ferroelectric liquid crystal composition and the alignment film, and when the ferroelectric liquid crystal composition is applied or dropped, the liquid crystal molecules are not aligned and are fixed to the alignment film. It is guessed that this is because it is suppressed.

  Specific examples of such a phenylpyrimidine compound include those represented by the following general formulas (3-1) to (3-4).

In the above formulas (3-1) to (3-4), R ²¹ is an alkyl group, and R ²² is an alkoxy group or a carboxyl group.

The phenylpyrimidine compound is a bicyclic compound having one pyrimidine ring and one benzene ring, a tricyclic compound having one pyrimidine ring and two benzene rings, one pyrimidine ring and 1 Any of a tricyclic compound having 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, the phase transition temperature of the chiral smectic C phase of the ferroelectric liquid crystal composition of the present invention is higher when the tricyclic compound is mixed with the bicyclic compound than when the bicyclic compound is used alone. This is because the usable range is widened when used in a liquid crystal 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 of the present invention is reduced, and therefore, 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.
In particular, when a phenyl pyrimidine compound is used as the host liquid crystal and the phenyl pyrimidine compound is a phenyl group substituted with a fluorine atom, the content of the phenyl pyrimidine compound in the ferroelectric liquid crystal composition is 10 mass. It is preferable that it is in the range of% to 30% by mass. This is because if the content of the phenylpyrimidine compound is small, the above effects may not be sufficiently obtained. On the other hand, if the content of the phenylpyrimidine compound is too large, the ferroelectric liquid crystal composition of the present invention is easily crystallized, so that the storage stability is deteriorated when used in a liquid crystal display device, and the ferroelectric liquid crystal composition This is because precipitation of a compound contained in the liquid crystal may occur and display quality may be deteriorated.

3. Ferroelectric liquid crystal composition 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.

  Among them, those exhibiting the half V-shaped switching characteristics as exemplified in FIGS. 2A and 2B can increase the transmittance even if the cone angle is relatively small. When the cone angle is sufficiently large, the V-shaped switching characteristics as illustrated in FIG. 2C make the operation of the liquid crystal molecules symmetric with respect to positive and negative voltages, electrical neutrality, and stability. This is preferable. Even asymmetric switching characteristics can be used by devising a driving method.

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 this invention has the 1st base material, the 1st electrode layer formed on the said 1st base material, and the 1st orientation layer formed on the said 1st electrode layer. A first alignment treatment substrate, a second substrate, a second electrode layer formed on the second substrate, and a second alignment treatment substrate having a second alignment layer formed on the second electrode layer; A liquid crystal display element having a liquid crystal layer formed between the first alignment layer and the second alignment layer, wherein the liquid crystal layer contains the ferroelectric liquid crystal composition described above. To do.

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

  According to the present invention, the liquid crystal layer contains the above-described ferroelectric liquid crystal composition, whereby the impact resistance can be improved.

  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 layer of the first alignment treatment substrate and the second alignment layer of the second alignment treatment substrate, and contains the above-described ferroelectric liquid crystal composition. .
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 3.0 μm. is there. This is because if the thickness of the liquid crystal layer is too thin, the contrast may be lowered. Conversely, if the thickness of the liquid crystal layer is too thick, the liquid crystal molecules may be difficult to align. 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 injected with the ferroelectric liquid crystal composition with an adhesive.
In the liquid crystal dropping method, for example, first, a heated or room temperature ferroelectric liquid crystal composition is dropped or applied onto the second alignment layer 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.

  Especially, it is preferable that the formation method of a liquid-crystal layer is a liquid crystal dropping system. This is because the liquid crystal display element can be efficiently manufactured by shortening the tact time. In addition, when the ferroelectric liquid crystal composition is dropped or applied, it is preferably at room temperature. This is because deterioration of the ferroelectric liquid crystal composition due to heat can be prevented.

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

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 layer.
Hereinafter, each configuration in the first alignment processing substrate will be described.

(1) 1st alignment layer The 1st alignment layer 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 layer and second alignment layer In the present invention, it is preferable that the constituent materials of the first alignment layer and the second alignment layer have different compositions with the liquid crystal layer interposed therebetween. By forming the first alignment layer and the second alignment layer using materials having different compositions, the polarities of the first alignment layer surface and the second alignment layer surface can be made different depending on the respective materials. As a result, the polar surface interaction of the ferroelectric liquid crystal composition and the first alignment layer is different from the polar surface interaction of the ferroelectric liquid crystal composition and the second alignment layer. This is because generation of alignment defects such as zigzag defects, hairpin defects, and double domains can be suppressed by appropriately selecting a material in consideration of the surface polarity of the second alignment layer. As a result, contrast can be improved.

In order to make the constituent materials of the first alignment layer and the second alignment layer 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 layer and the second alignment layer are rubbing alignment films, the composition can be changed by changing the amount of additive added or by the presence or absence of the additive.

When the first alignment layer and the second alignment layer 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.
Further, when the first alignment layer and the second alignment layer 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 layer and the second alignment layer 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.

Photo-alignment films using photodimerization materials tend to have a relatively positive polarity compared to photo-alignment films using photoisomerization-type materials. The spontaneous polarization of the liquid crystal molecules tends to face the photo-alignment film side using the photoisomerizable material.
Photo-alignment films using photodimerized materials tend to have a relatively positive polarity relative to the rubbing alignment film, so the spontaneous polarization of the liquid crystal molecules tends to face the rubbing alignment film due to the polar surface interaction. It is in.
In addition, rubbing alignment films tend to have a relatively strong positive polarity compared to photo-alignment films using photoisomerizable materials, so that the spontaneous polarization of liquid crystal molecules is caused by the photoisomerization type due to the polar surface interaction. It tends to face the photo-alignment film side using the material.
In such a combination, the direction of spontaneous polarization of liquid crystal molecules can be controlled, and the occurrence of alignment defects can be effectively suppressed.

In the present invention, as described above, when the second alignment layer tends to have a relatively positive polarity in the first alignment layer and the second alignment layer, the second electrode layer is negative. It is preferable to perform display when the above voltage is applied.
As the case where the second alignment layer tends to have a relatively strong positive polarity in the first alignment layer and the second alignment layer, the above-mentioned combinations can be mentioned, and specifically, the first alignment layer. Is a photo-alignment film using a photoisomerizable material, the second alignment layer is a photo-alignment film using a photo-dimerization material; the first alignment layer is a rubbing alignment film, and the second alignment layer is a photo-dimerization type It is preferable that a photo-alignment film using a material is used; alternatively, the first alignment layer is a photo-alignment film using a photoisomerizable material, and the second alignment layer is a rubbing alignment film.
Note that a method for driving the liquid crystal display element will be described later, and a description thereof will be omitted here.

(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 layer.

  In addition, about a 2nd base material, a 2nd electrode layer, a 2nd orientation layer, and another structure, with the 1st base material in a said 1st orientation processing board | substrate, a 1st electrode layer, a 1st orientation layer, 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. In the present invention, the ferroelectric liquid crystal composition exhibits monostability, and the second alignment layer is relatively the first alignment layer and the second alignment layer. When the positive polarity tends to be strong, display is preferably performed when a negative voltage is applied to the second electrode layer.

  FIG. 4 is a schematic diagram showing an example of the alignment state of a ferroelectric liquid crystal composition that exhibits monostability and exhibits half V-shaped switching characteristics. 4A shows a case where no voltage is applied, FIG. 4B shows a case where a negative voltage is applied to the second electrode layer, and FIG. 4C shows a case where a positive voltage is applied to the second electrode layer. Each is shown. When no voltage is applied, the liquid crystal molecules 25 are stabilized in one state on the cone (FIG. 4A). When a negative voltage is applied to the second electrode layer, the liquid crystal molecules 25 are inclined from the stabilized state (broken line) to one side (FIG. 4B). In addition, when a positive voltage is applied to the second electrode layer, the liquid crystal molecules 25 are tilted from the stabilized state (broken line) to the opposite side when a negative voltage is applied to the second electrode layer (see FIG. 4 (c)). At this time, the inclination angle δ when a negative voltage is applied to the second electrode layer is larger than the inclination angle ω when a positive voltage is applied to the second electrode layer. In FIG. 4, D indicates the alignment treatment direction of the first alignment layer and the second alignment layer, and z indicates the layer normal.

  In this way, when the second alignment layer tends to have a relatively positive polarity, the inclination angle of the liquid crystal molecules from the mono-stabilized state when the negative voltage of the second electrode layer is applied is When the positive voltage of the second electrode layer is applied, the inclination angle of the liquid crystal molecules from the mono-stabilized state becomes larger. Therefore, when a negative voltage is applied to the second electrode layer, the amount of transmitted light is larger than when a positive voltage is applied to the second electrode layer. That is, when a positive voltage is applied to the second electrode layer, the amount of transmitted light is less than when a negative voltage is applied to the second electrode layer. For this reason, when a positive voltage is applied to the second electrode layer, it is more disadvantageous for display than when a negative voltage is applied to the second electrode layer. Therefore, it is preferable to perform display when a negative voltage is applied to the second electrode layer where the tilt angle from the mono-stabilized state of the liquid crystal molecules becomes larger.

  “Display when a negative voltage is applied to the second electrode layer” means that liquid crystal molecules are stabilized in one state on the cone when no voltage is applied, and the second electrode layer is negative. When the voltage is applied, the liquid crystal molecules tilt from the mono-stabilized state to one side on the cone, and the liquid crystal molecules maintain the mono-stabilized state when a positive voltage is applied to the second electrode layer. Or tilted from the mono-stabilized state to the opposite side of the negative voltage applied to the second electrode layer, and tilted from the mono-stabilized state of the liquid crystal molecules when a negative voltage is applied to the second electrode layer. It means that the angle is larger than the tilt angle from the mono-stabilized state of the liquid crystal molecules when a positive voltage is applied to the second electrode layer. At this time, the alignment direction in the mono-stabilized state of the liquid crystal molecules and the polarization axis of one polarizing plate are made substantially parallel.

In the first alignment layer and the second alignment layer, when the second alignment layer tends to have a relatively positive polarity, in the no voltage applied state, as illustrated in FIG. Therefore, the spontaneous polarization Ps of the liquid crystal molecules 25 tends to be directed toward the first alignment layer 4a. At this time, as illustrated in FIG. 8A, the liquid crystal molecules 25 are aligned along the alignment treatment direction D of the first alignment layer and the second alignment layer to be in a uniform alignment state. Further, when a negative voltage is applied to the second electrode layer 3b, the spontaneous polarization Ps of the liquid crystal molecules 25 is directed to the second alignment layer 4b side due to the influence of the polarity of the applied voltage, as illustrated in FIG. . Also at this time, as illustrated in FIG. 8B, the liquid crystal molecules 25 are in a uniform alignment state. Further, when a positive voltage is applied to the second electrode layer 3b, the spontaneous polarization Ps of the liquid crystal molecules 25 is directed toward the first alignment layer 4a due to the influence of the polarity of the applied voltage, as illustrated in FIG. . In this case, the direction of spontaneous polarization is the same as that in the state where no voltage is applied. As described above, the direction of the spontaneous polarization is the direction in which the polarization of the liquid crystal molecules and the polarization of the alignment film or the polarity of the voltage are electrically balanced. This is because of an electrically stable state.
FIG. 8A is a schematic diagram showing the alignment state of the liquid crystal molecules from the upper surface of FIG. 5, and the spontaneous polarization Ps is directed from the front side to the back side of the sheet (the mark “X” in FIG. 8A). ). FIG. 8B is a schematic diagram showing the alignment state of the liquid crystal molecules from the upper surface of FIG. 6, and the spontaneous polarization Ps is directed from the back of the page to the near side (the mark ● in FIG. 8B). ).

  From the no-voltage applied state or the positive voltage applied state to the second electrode layer (FIG. 5) to the negative voltage applied state to the second electrode layer (FIG. 6), the negative polarity of this applied voltage, Due to the repulsion of the spontaneous polarization of the liquid crystal molecules with the negative polarity, as illustrated in FIG. That is, when a negative voltage is applied to the second electrode layer, the molecular direction of the liquid crystal changes approximately twice the tilt angle θ of the liquid crystal in parallel to the first alignment treatment substrate surface.

  As described above, when the second alignment layer tends to have a relatively positive polarity in the first alignment layer and the second alignment layer, the spontaneous polarization of the liquid crystal molecules tends to be directed to the first alignment layer side. By utilizing this, it is possible to control the direction of spontaneous polarization of liquid crystal molecules.

  A liquid crystal display element using a ferroelectric liquid crystal composition exhibiting V-shaped switching characteristics or asymmetric switching characteristics can be driven by controlling the direction of spontaneous polarization of liquid crystal molecules in the same manner. .

  When a negative voltage is applied to the second electrode layer, there are preferably 70% or more, more preferably 80% or more, more preferably 90% or more, in which the molecular direction of the liquid crystal changes about twice the tilt angle. Most preferably, it is 95% or more. This is because a favorable contrast ratio can be obtained within the above range.

In addition, said ratio can be measured as follows.
For example, as shown in FIG. 9, polarizing plates 17a and 17b are provided outside the first alignment processing substrate 11a and the second alignment processing substrate 11b, respectively, and the two polarizing plates 17a and 17b have substantially vertical polarization axes. In addition, a liquid crystal display element is used in which the polarization axis of the polarizing plate 17a and the rubbing treatment direction (the alignment direction of liquid crystal molecules) of the first alignment layer 4a are substantially parallel. A dark state is obtained when no voltage is applied, and a bright state is obtained when a voltage is applied.
When a negative voltage is applied to the second electrode layer, a bright state is obtained when the molecular direction of the liquid crystal changes approximately twice the tilt angle. On the other hand, when a negative voltage is applied to the second electrode layer, for example, when there is a part in which the molecular direction of the liquid crystal does not change, a dark state is partially obtained. Therefore, from the white / black area ratio of black and white (light / dark) display obtained at the time of voltage application, the ratio of the liquid crystal molecular direction changing about twice the tilt angle when a negative voltage is applied to the second electrode layer. Can be calculated.

  When a negative voltage is applied to the second electrode layer, the liquid crystal molecules are tilted from the mono-stabilized state to one side on the cone at an angle corresponding to the magnitude of the applied voltage. In the ferroelectric liquid crystal composition, as illustrated in FIG. 4A, the position A (direction of the liquid crystal molecules 25), the position B (alignment processing direction D), and the position C are not necessarily coincident. Do not mean. Therefore, as illustrated in FIG. 4B, the maximum tilt angle δ when a negative voltage is applied to the second electrode layer is about twice the tilt angle θ.

  In addition, the angle at which the molecular direction of the liquid crystal changes in parallel to the first alignment treatment substrate surface can be measured as follows. First, a polarizing microscope and a liquid crystal display element in which polarizing plates are arranged in crossed Nicols are arranged so that the polarization axis of one polarizing plate and the alignment direction of liquid crystal molecules in the liquid crystal layer are parallel, and this position is used as a reference. . When a voltage is applied, the liquid crystal molecules come to have a predetermined angle with the polarization axis, so that the polarized light transmitted through one polarizing plate is transmitted through the other polarizing plate to be in a bright state. With this voltage applied, the liquid crystal display element is rotated to a dark state. And the angle which rotated the liquid crystal display element at this time is measured. The angle by which the liquid crystal display element is rotated is an angle at which the molecular direction of the liquid crystal changes in parallel to the first alignment processing substrate surface.

  As described above, when a negative voltage is applied to the second electrode layer, the liquid crystal molecules are inclined from the mono-stabilized state to one side on the cone at an angle according to the magnitude of the applied voltage. When driving the liquid crystal display element, the direction of the liquid crystal molecules does not change about twice the tilt angle when a negative voltage is applied to the second electrode layer.

In a liquid crystal display element using a ferroelectric liquid crystal composition exhibiting monostability, the amount of transmitted light depends on the tilt angle of liquid crystal molecules when a voltage is applied. When either positive or negative voltage is applied, the liquid crystal molecules are tilted on the cone. Therefore, as shown in FIG. 2, for example, the tilt angle of the liquid crystal molecules changes according to the magnitude of the applied voltage, and the transmitted light amount changes. At this time, the amount of transmitted light is maximized when the inclination angle of the liquid crystal molecules from the monostable state is 45 °.
Therefore, in order to realize a high amount of transmitted light, a ferroelectric liquid crystal whose tilt angle from a monostable state of liquid crystal molecules can be 45 ° when a negative voltage is applied to the second electrode layer during actual driving. It is preferable to use a composition.
For example, when a ferroelectric liquid crystal composition having a maximum tilt angle δ from the monostable state of liquid crystal molecules as shown in FIG. 4 is larger than 45 °, the liquid crystal display element is actually driven. At this time, when a negative voltage is applied to the second electrode layer, the tilt angle of the liquid crystal molecules from the monostable state can be set to 45 °. This is because, as described above, when a negative voltage is applied to the second electrode layer during actual driving, the direction of the liquid crystal molecules does not change approximately twice the tilt angle.

  As a driving method of the liquid crystal display element of the present invention, since the high-speed response of the ferroelectric liquid crystal composition can be used, the high-speed response is obtained in order to obtain a good moving image display characteristic by dividing one pixel into time. In particular, it can be suitably used for a required field sequential color system.

  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.

  In the present invention, the first alignment treatment substrate may be a TFT substrate, the second alignment treatment substrate may be a common electrode substrate, the first alignment treatment substrate is a common electrode substrate, and the second alignment treatment substrate is a TFT substrate. Also good. In particular, when the first alignment layer and the second alignment layer tend to have a relatively positive polarity in the second alignment layer, the first alignment processing substrate is common to the TFT substrate and the second alignment processing substrate. An electrode substrate is preferred.

  For example, in the liquid crystal display element 1 shown in FIG. 10, when the gate electrode 26x is set to a high potential of about 30 V, the TFT element 27 is switched on, and a signal voltage is applied to the ferroelectric liquid crystal composition by the source electrode 26y. When the electrode 26x is set to a low potential of about −10V, the TFT element 27 is switched off. In the switch-off state, as illustrated in FIG. 11, a voltage is applied between the common electrode (second electrode layer 3b) and the gate electrode 26x so that the common electrode (second electrode layer 3b) side is positive. . In this switch-off state, the liquid crystal molecules do not operate, so that the pixel is in a dark state.

  In the first alignment layer and the second alignment layer, when the second alignment layer tends to have a relatively strong positive polarity, the spontaneous polarization of the liquid crystal molecules is caused by the polar surface interaction in the no-voltage applied state. There is a tendency to face one alignment layer side. That is, in the switch-off state, as illustrated in FIG. 11, the spontaneous polarization Ps of the liquid crystal molecules 25 faces the TFT substrate (first alignment processing substrate 11a) side. Therefore, the direction of spontaneous polarization is not affected by the voltage applied between the common electrode (second electrode layer 3b) and the gate electrode 26x. Therefore, by controlling the direction of spontaneous polarization and using the first alignment treatment substrate as the TFT substrate and the second alignment treatment substrate as the common electrode substrate, light leakage near the gate electrode can be prevented.

  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)
Ferroelectric liquid crystal compositions were prepared using the chiral compounds 1 to 15 shown below, as shown in Tables 1 to 3 below.

(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 (LIA012: DIC Corporation) was spin-coated at 1500 rpm for 30 seconds on the glass substrate 2 coated with ITO. 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. The ferroelectric liquid crystal composition described above was applied to the substrate in the form of dots, and the two substrates were assembled and thermocompression bonded so that the rubbing treatment direction and the polarization treatment direction were perpendicular. Thereafter, the liquid crystal cell was cooled to align the ferroelectric liquid crystal composition.

(Evaluation)
1) Impact resistance The liquid crystal display device thus obtained was tested for impact resistance.
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 3N and 5N was applied with a push area of 1.3 cm ² .
When the liquid crystal alignment does not change after applying the 5N load, “◯”, the liquid crystal alignment does not change after applying the 3N load, and when the 5N load is applied, the alignment changes and returns. When it was not, “Δ” was evaluated, and when the load of 3N was applied, the orientation changed and returned to “x”.
2) Application trace As shown in FIG. 12A, when the orientation of the place where the ferroelectric liquid crystal composition is applied in the form of dots is disturbed, “X”, as shown in FIG. When the application mark could be visually confirmed, “Δ” was evaluated, and when the application mark could not be visually confirmed as illustrated in FIG.
Table 4 shows the evaluation results of impact resistance and application marks.

3) Display quality The liquid crystal display element using the host liquid crystal A as illustrated in FIG. 13A is more complex than the liquid crystal display element using the host liquid crystal B as illustrated in FIG. The display quality was good because the refraction was small.

[Example 2]
(Ferroelectric liquid crystal composition)
Using the chiral compounds 1 to 11 shown above, ferroelectric liquid crystal compositions were prepared as shown in Tables 1 and 2 above.

(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 solution of a photoisomerization type photo-alignment film material (LIA012: DIC Corporation) was spin-coated 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.

  Further, a solution of a photoisomerization type photo-alignment film material (LIA012: DIC Corporation) was spin-coated at 1500 rpm for 30 seconds on the ITO-coated glass substrate 2. Thereafter, after drying in an oven at 100 ° C. for 3 minutes, 2J-polarized exposure processing was performed with a polarizing exposure machine.

  Next, the sealing material was applied on the glass substrate 1 in a square frame shape so that there was no break. The ferroelectric liquid crystal composition was applied to the substrate in a dot shape so as to be inside the sealing material, and the two substrates were assembled and thermocompression bonded so that the directions of polarization treatment were parallel. Thereafter, the liquid crystal cell was cooled to align the ferroelectric liquid crystal composition.

(Evaluation)
1) Impact resistance When the obtained liquid crystal display element was subjected to an impact resistance test, there was no change in the liquid crystal alignment after a load of 5N was applied.
2) Orientation Liquid crystal display element No. obtained in Example 1 When the liquid crystal alignment of 1-1 to 1-12 and 2-1 to 2-12 was observed, uniform alignment was obtained.
On the other hand, when the liquid crystal alignment of the liquid crystal display element obtained in Example 2 was observed, double-domain alignment defects partially occurred as illustrated in FIG.
The results are shown in Table 5.

[Example 3]
(Ferroelectric liquid crystal composition)
Using the chiral compounds 16 to 20 shown in Table 6 below, ferroelectric liquid crystal compositions were prepared as shown in Table 7 below.

(Production of liquid crystal display element)
A liquid crystal display element was produced in the same manner as in Examples 1 and 2.

(Evaluation)
1) Impact resistance When the obtained liquid crystal display element was subjected to an impact resistance test, there was no change in the liquid crystal alignment after a load of 5 N was applied to a push area of 1 cm ² .
2) Alignment When the liquid crystal alignment of the obtained liquid crystal display element was observed, the same alignment as in Example 1 was obtained.
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 the positive voltage (+10 V) and 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.
As a result, when a chiral compound having two fluorine atoms as a substituent is used, either a chiral compound having one fluorine atom as a substituent or a chiral compound having no fluorine atom is used. The tilt angle was larger than that.
Table 8 shows the evaluation results of impact resistance, orientation and tilt angle.

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 layer 4b ... 2nd orientation layer 5 ... Liquid crystal layer 11a ... 1st orientation Treatment substrate 11b ... Second alignment treatment substrate 25 ... Liquid crystal molecules

Claims (4)

A ferroelectric liquid crystal composition comprising a chiral compound represented by the following general 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.
R ² is a chiral group, and is a group represented by the following general formula (2).
In (above formula (2), 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. )   2. The ferroelectric liquid crystal composition according to claim 1, wherein the content of the chiral compound is in the range of 5 mass% to 35 mass%. A first alignment treatment substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment layer 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 layer formed on the second electrode layer;
A liquid crystal display element having a liquid crystal layer formed between the first alignment layer and the second alignment layer,
A liquid crystal display element, wherein the liquid crystal layer contains the ferroelectric liquid crystal composition according to claim 1.   4. The liquid crystal display element according to claim 3, wherein the constituent material of the first alignment layer and the constituent material of the second alignment layer have different compositions.