JP2014025044A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element with an excellent display quality by using a ferroelectric liquid crystal composition capable of exhibiting impact resistance.SOLUTION: The provided liquid crystal display element 1 comprises: a first oriented substrate 11a comprising a first electrode layer 3a formed atop a first substrate 2a and a rubbed first oriented film 4a formed atop the first electrode layer; a second oriented substrate 11b comprising a second electrode layer 3b formed atop a second substrate 2b and a rubbed second oriented film 4b formed atop the second electrode layer; and a liquid crystal layer 5 including a ferroelectric liquid crystal composition and formed between the first oriented film and the second oriented film; the first oriented film and the second oriented film are arrayed in a state where the respective rubbing directions D1 and D2 thereof are parallel, and the ferroelectric liquid crystal composition includes a chiral compound having a specific molecule structure.

Description

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

  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 four benzene rings are directly bonded is used, the contrast ratio is good even after an impact is applied. It has been reported that

By the way, in a liquid crystal display element using a ferroelectric liquid crystal composition, a pair of rubbing alignment films is generally arranged so that the rubbing treatment directions are parallel. At this time, the alignment films subjected to the rubbing treatment are arranged so that the rubbing treatment directions are parallel and the same direction (also referred to as parallel), and the rubbing treatment directions are parallel and opposite directions (also referred to as anti-parallel). It may be arranged to be.
Conventionally, it has been preferable to be arranged in an antiparallel manner (see, for example, Patent Document 7). This is because the liquid crystal molecules 101 are given a pretilt by the alignment films 100a and 100b subjected to the rubbing process as illustrated in FIGS. 19A and 19B, and thus the rubbing process as illustrated in FIG. 19A. The alignment films 100a and 100b subjected to the rubbing treatment as illustrated in FIG. 19B, rather than the alignment films 100a and 100b thus arranged so that the rubbing treatment directions D1 and D2 are parallel and in the same direction (parallel). This is because it is considered that the alignment defects are less likely to occur and the uniform alignment can be obtained when the rubbing treatment directions D1 and D2 are arranged in parallel and in opposite directions (anti-parallel).

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 JP 2006-220675 A

Therefore, the present inventors produced a liquid crystal display element in which rubbing-treated alignment films were arranged in antiparallel using a ferroelectric liquid crystal composition capable of exhibiting impact resistance. However, when liquid crystal display elements were fabricated by combining various rubbing alignment films, it was found that almost all combinations of rubbing alignment films generated two domains with distinctly different shades, which deteriorated display quality.
The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a liquid crystal display device having excellent display quality when a ferroelectric liquid crystal composition capable of exhibiting impact resistance is used. Is.

  As a result of various studies on impact resistance of a liquid crystal display device using a ferroelectric liquid crystal composition, the present inventors have found that when a ferroelectric liquid crystal composition capable of exhibiting impact resistance is used, Contrary to the preferred embodiment of the above, it has been found that by arranging the alignment films subjected to the rubbing treatment in parallel, it is possible to prevent deterioration in display quality due to different domains and realize high-quality image display. The present invention has been completed.

  That is, 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 and rubbed. A second alignment having an alignment substrate, a second substrate, a second electrode layer formed on the second substrate, and a second alignment film formed on the second electrode layer and rubbed. A liquid crystal display element having a processing substrate and a liquid crystal layer formed between the first alignment film and the second alignment film and containing a ferroelectric liquid crystal composition, wherein the first alignment film and the second alignment film The alignment film is arranged so that the rubbing treatment direction is parallel, and the ferroelectric liquid crystal composition is represented by the chiral compound A represented by the following general formula (1) and the following general formula (2). Containing at least one chiral compound of chiral compound B To provide a liquid crystal display element according to.

(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. )

  According to the present invention, the compound contains at least one chiral compound of the chiral compound A represented by the above formula (1) and the chiral compound B represented by the above formula (2), and is capable of exhibiting impact resistance. When the dielectric liquid crystal composition is used, the first alignment film and the second alignment film are arranged so that the rubbing treatment directions are parallel, thereby enabling a liquid crystal display element having excellent display quality. Become.

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

  In the present invention, a ferroelectric compound containing 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 exhibiting impact resistance When the first liquid crystal composition is used, the first alignment film and the second alignment film are arranged so that the rubbing treatment directions are parallel, whereby the liquid crystal display element having excellent display quality can be obtained. Play.

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 an example of the orientation state of the liquid crystal molecule in the ferroelectric liquid crystal composition which shows bistability. It is a schematic diagram for demonstrating a chevron structure. It is a schematic diagram for demonstrating a bookshelf structure. It is a schematic diagram which shows an example of the orientation state of the liquid crystal molecule in the ferroelectric liquid crystal composition which shows monostability and has a half V-shaped switching characteristic. 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 diagram which shows an example of the orientation state of the liquid crystal molecule in a parallel and antiparallel liquid crystal display element. It is a schematic diagram which shows an example of the orientation state of a liquid crystal molecule. It is a schematic diagram which shows the other example of the orientation state of a liquid crystal molecule. It is a schematic diagram which shows the other example of the orientation state of a liquid crystal molecule. 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 diagram which shows the other example of the orientation state of a liquid crystal molecule. It is a schematic diagram which shows the other example of the orientation state of a liquid crystal molecule. It is a schematic diagram which shows the spontaneous polarization of a liquid crystal molecule. 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 a liquid crystal molecule. It is a photograph for demonstrating evaluation of the liquid crystal orientation in an Example. It is a schematic diagram which shows the other example of the orientation state of the liquid crystal molecule in a parallel and antiparallel liquid crystal display element.

Hereinafter, the liquid crystal display element of the present invention will be described in detail.
The liquid crystal display element of the present invention has 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 and subjected to a rubbing process. A first alignment treatment substrate, a second substrate, a second electrode layer formed on the second substrate, and a second alignment film formed on the second electrode layer and subjected to a rubbing treatment A liquid crystal display device having a two-alignment-treated substrate and a liquid crystal layer formed between the first alignment film and the second alignment film and containing a ferroelectric liquid crystal composition, wherein the first alignment film and the above-mentioned The second alignment film is arranged so that the rubbing treatment direction is parallel, and the ferroelectric liquid crystal composition is represented by the chiral compound A represented by the above formula (1) and the above formula (2). Containing at least one chiral compound of chiral compound B, Is shall.

The liquid crystal display element of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the liquid crystal display element of the present invention. As illustrated in FIG. 1, the liquid crystal display element 1 includes a first alignment treatment substrate 11a in which a first electrode layer 3a and a first alignment film 4a are formed on a first substrate 2a, and a second substrate 2b. A liquid crystal containing a ferroelectric liquid crystal composition is formed between the second alignment substrate 11b on which the second electrode layer 3b and the second alignment film 4b are formed, and the first alignment film 4a and the second alignment film 4b. Layer 5. The first alignment film 4a and the second alignment film 4b are both rubbed films and are arranged so that the rubbing directions D1 and D2 are parallel. The ferroelectric liquid crystal composition contained in the liquid crystal layer 5 contains at least one chiral compound of the chiral compound A represented by the above formula (1) and the chiral compound B represented by the above formula (2). Yes.

  Here, heretofore, as a ferroelectric liquid crystal composition, a ferroelectric liquid crystal composition exhibiting bistability in which a phase series reaches a Kalail smectic C phase via a smectic A phase is known. As shown in FIG. 2, the ferroelectric liquid crystal composition exhibiting such bistability has one smectic layer structure and two stable states 25a and 25b with respect to the layer normal z. ing. In this case, two kinds of stable states 25a and 25b can be achieved by applying a positive or negative polarity voltage to align the direction of spontaneous polarization of the liquid crystal molecules 25.

  When the ferroelectric liquid crystal composition exhibiting the above bistability is injected into a liquid crystal cell in which a rubbing alignment film is arranged in parallel, a structure called a chevron structure illustrated in FIG. It is known that two states are formed and the directions of bending are different. In this case, a defect occurs at the boundary between these two different states, causing a decrease in contrast.

  In order to suppress the occurrence of such defects, as illustrated in FIG. 4, a method of forming a bookshelf structure by making the rubbing treatment directions D1 and D2 anti-parallel has been attempted. In order to obtain the state, there still remains a problem that it is necessary to greatly increase the pretilt angle of the liquid crystal molecules by the rubbing alignment film.

  In addition, as the ferroelectric liquid crystal composition, a ferroelectric liquid crystal composition exhibiting monostability in which the phase series reaches the chiral smectic C phase without passing through the smectic A phase and has a half V-shaped switching characteristic. It has been known. In the case of such a ferroelectric liquid crystal composition, since the smectic layer structure is formed simultaneously with the phase transition to the chiral smectic C phase, the layer normal z is inclined with respect to the rubbing treatment direction d as illustrated in FIG. It is formed in the direction. In this case, as illustrated in FIG. 5, two domains having different layer normal z directions are generated. In the two domains, the liquid crystal molecules 25 operate only with positive and negative voltages of opposite polarities. I can not use it.

The ferroelectric liquid crystal composition in 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). The ferroelectric liquid crystal composition in the present invention also exhibits monostability.
The present inventors have used such a ferroelectric liquid crystal composition, and in various rubbing alignment film combinations and rubbing treatment methods, stable positions of liquid crystal molecules when no voltage is applied, and liquid crystal molecules when a voltage is applied As a result of analyzing the behavior of the following, we found the following.

An example of a plan view of a liquid crystal display element using the ferroelectric liquid crystal composition of the present invention is shown in FIGS. 6 (a) and 6 (b). As illustrated in FIGS. 6A and 6B, there are two types of directions in which the liquid crystal molecules 25 are stabilized with respect to the rubbing treatment direction d when no voltage is applied. In FIG. 6A, the liquid crystal molecules 25 move to the left when a negative polarity voltage is applied, and the liquid crystal molecules 25 move to the right when a positive polarity voltage is applied. Further, the operating angle of the liquid crystal molecules 25 when a negative polarity voltage is applied is larger. On the other hand, in FIG. 6B, compared with the case of FIG. 6A, the operation directions of the liquid crystal molecules 25 with respect to the positive and negative polarities are the same, but the operation angle is opposite and the negative polarity is obtained. Is small when a positive voltage is applied, and is large when a positive polarity voltage is applied. In either case, the positions when positive and negative voltages are applied coincide with each other.
The operation of such liquid crystal molecules is different from the conventional ferroelectric liquid crystal composition that exhibits monostability and has half V-shaped switching characteristics as described above.

  Furthermore, using the ferroelectric liquid crystal composition according to the present invention, various rubbing alignment films were used and arranged to be parallel or anti-parallel, and liquid crystal display elements were prepared and analyzed. As a result, when the rubbing alignment films are arranged in parallel, even when two domains are generated, both domains are unified into either FIG. 6 (a) or FIG. 6 (b). I found out. On the other hand, when the rubbing alignment film is arranged so as to be anti-parallel, two domains are generated in most combinations of rubbing alignment films, and in both FIGS. 6 (a) and 6 (b). It was.

FIGS. 7A and 7B show a cross-sectional view of a liquid crystal display element using the ferroelectric liquid crystal composition in the present invention.
When the rubbing treatment directions D1 and D2 are parallel as illustrated in FIG. 7A, each of the upper and lower rubbing alignment films in contact with the liquid crystal layer is strongly influenced as shown in (i) and (iii). Although the pretilt angles of the liquid crystal molecules 25 are different in the domain, as shown in (ii) and (iv), the stable positions of the liquid crystal molecules 25 when no voltage is applied in plan view are substantially the same. Therefore, by reducing the pretilt angle of the liquid crystal molecules by the rubbing alignment film, the difference between the two domains is reduced, so that the monodomain can be easily aligned.
On the other hand, when the rubbing directions D1 and D2 are anti-parallel as illustrated in FIG. 7B, the upper and lower rubbing alignment films in contact with the liquid crystal layer as shown in (v) and (viii) Even if the pretilt direction of the liquid crystal molecules 25 is the same in the domains strongly influenced by each of the above, the direction of the stable state of the liquid crystal molecules 25 when no voltage is applied in plan view as shown in (vii) and (x) Are very different. Therefore, no matter how the pretilt angle of the liquid crystal molecules in the rubbing alignment film is controlled, it cannot be a mono domain.

  As described above, 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) and exhibits impact resistance. When the ferroelectric liquid crystal composition to be obtained is used, the first alignment film and the second alignment film are arranged so that the rubbing treatment directions are parallel, so that liquid crystal molecules when no voltage is applied in plan view These liquid crystal display elements can be provided with excellent display quality.

  Hereinafter, each structure in the liquid crystal display element of this invention is demonstrated.

A. 1st alignment film and 2nd alignment film In this invention, a 1st alignment film and a 2nd alignment film are films | membranes which were rubbed, and are arrange | positioned so that the rubbing process direction may become parallel.

Here, the first alignment film and the second alignment film are arranged so that the rubbing treatment directions are parallel, that the rubbing treatment direction of the first alignment film and the rubbing treatment direction of the second alignment film are parallel and The same direction.
That the rubbing treatment direction of the first alignment film and the rubbing treatment direction of the second alignment film are parallel means that the angle formed by the rubbing treatment direction of the first alignment film and the rubbing treatment direction of the second alignment film is 0 ± 5. It is within the range of degrees.

In addition, it is confirmed by measuring the pretilt angle of the liquid crystal molecules with respect to the first alignment film and the second alignment film that the first alignment film and the second alignment film are arranged so that the rubbing treatment directions are parallel. be able to. The direction in which the rubbing process is performed can be determined from the pretilt direction of the liquid crystal molecules.
The pretilt angle can be measured by a crystal rotation method.

The pretilt angle of the liquid crystal molecules with respect to the first alignment film and the second alignment film is not particularly limited, but is preferably 10 degrees or less, more preferably 5 from the viewpoint of display quality and impact resistance. Degrees or less, more preferably 3 degrees or less. As described above, by reducing the pretilt angle of the liquid crystal molecules with respect to the first alignment film and the second alignment film, the difference between the two domains is reduced, so that the monodomain can be easily aligned. Also, it is presumed that the smaller the pretilt angle, the smaller the change in the tilt angle of the liquid crystal molecules when an impact is applied, and the easier it is to return to the original state.
Since the pretilt angle is preferably as small as possible, the lower limit of the pretilt angle is not particularly limited, but is usually about 1 degree.
The pretilt angle can be appropriately adjusted depending on the materials of the first alignment film and the second alignment film, the conditions of the rubbing treatment, and the like.

  The material used for the first alignment film and the second alignment film is not particularly limited as long as anisotropy can be imparted to the film by rubbing treatment. For example, nylon, polyimide, polyamide, Examples thereof include polyamic acid, polyamideimide, polyetherimide, polyvinyl alcohol, and polyurethane. These may be used alone or in combination of two or more.

  Among these, it is preferable that the first alignment film and the second alignment film contain polyimide. This is because the liquid crystal molecules are easily aligned in the azimuth direction in the first alignment film and the second alignment film containing polyimide. That is, the liquid crystal molecules are easily arranged in a certain direction.

The polyimide used for the first alignment film and the second alignment film preferably has a pretilt angle in the above range.
In order to make the pretilt angle within the above range, for example, it is preferable to shorten the length of the polyimide side chain. A method of controlling the pretilt angle by changing the chain length of the polymer side chain is known, and it has been reported that the pretilt angle increases as the side chain length increases.
In order to set the pretilt angle within the above range, for example, it is preferable to reduce the density of the side chain of the polyimide.

As the rubbing treatment method, a general method can be applied.
It should be noted that the pretilt angle can be controlled by adjusting the amount of roller pressing, the number of rotations, the speed, the number of rubbing processes, and the like in the rubbing process. In order to set the pretilt angle within the above range, for example, it is preferable to reduce the push-in amount.

  The thickness of the first alignment film and the second alignment film is set to about 1 nm to 1000 nm, and preferably in the range of 50 nm to 100 nm.

  In the present invention, it is preferable that the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions across the liquid crystal layer. This is because by adopting such a configuration, the direction of spontaneous polarization of liquid crystal molecules can be made uniform, and a monodomain can be formed. Moreover, it is because generation | occurrence | production of orientation defect can be suppressed and contrast can be improved.

  When the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions across the liquid crystal layer, the ferroelectric liquid crystal composition and the first alignment are used in the first alignment film and the second alignment film. It is considered that the polar surface interaction, which is the interaction between the film surface and the second alignment film surface, is different. Therefore, in the first alignment film and the second alignment film, when the second alignment film tends to have a relatively positive polarity, as illustrated in FIG. It is considered that the positive polarity of the spontaneous polarization Ps of the liquid crystal molecules 25 faces the first alignment film 4a side due to the polar surface interaction. On the other hand, in the first alignment film and the second alignment film, when the first alignment film tends to have a relatively positive polarity, as illustrated in FIG. It is considered that the positive polarity of the spontaneous polarization Ps of the liquid crystal molecules 25 faces the second alignment film 4b side due to the polar surface interaction. The direction of spontaneous polarization is such a direction because the direction of spontaneous polarization is the direction in which the polarization of the liquid crystal molecules and the alignment film are electrically balanced, and the liquid crystal molecules are in an electrically stable state. It seems to be because. 8 and 9, the liquid crystal layer shows liquid crystal molecules.

  Therefore, 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. it can. 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. The direction of spontaneous polarization can be controlled by appropriately selecting a material in consideration of the surface polarity of the second alignment film. As a result, the occurrence of alignment defects peculiar to the ferroelectric liquid crystal composition can be suppressed, and the contrast can be improved. Furthermore, a monodomain orientation can be obtained.

  As a method of making the composition of the constituent materials of the first alignment film and the second alignment film different, for example, a method of different types of material systems such as using polyimide on one side and nylon on the other side, polyimides having different side chains And the like, a method of varying the side chain, a method of changing the content of the additive, and a method of varying the content of each component such as the presence or absence of the additive.

B. 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 includes a ferroelectric liquid crystal composition.
Hereinafter, each configuration in the liquid crystal layer will be described.

1. Ferroelectric liquid crystal composition The ferroelectric liquid crystal composition used in the present invention is a chiral compound of 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 contains a compound.
Hereinafter, each component in the ferroelectric liquid crystal composition will be described.

(1) Chiral compound The chiral compound 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).

  In the present invention, the ferroelectric liquid crystal composition only needs to contain at least one of the chiral compound A and the chiral compound B. For example, the ferroelectric liquid crystal composition may contain only the chiral compound A or only the chiral compound B. It may contain, and the chiral compound A and the chiral compound B may be contained. Further, when the ferroelectric liquid crystal composition contains the chiral compound A, it may contain one kind of chiral compound A or two or more kinds of chiral compounds A. Similarly, when the ferroelectric liquid crystal composition contains the chiral compound B, it may contain one kind of chiral compound B or may contain two or more kinds of chiral compounds B.

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

(A) Chiral compound A
The chiral compound A used in the present invention is 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 (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 (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 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 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, there is an advantage that the magnitude of the spontaneous polarization of the liquid crystal molecules can be increased and 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.

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 decreases, so that the synthesis and purification of the chiral compound A becomes difficult, the cost increases, and the ferroelectric liquid crystal The composition is easily crystallized, and 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. Further, since the steric structure of the chiral compound A is distorted and the crystallization of the ferroelectric liquid crystal composition is hindered 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) to (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.

  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.

  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 content of the chiral compound A 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 A is used alone, the content of the chiral compound A is ferroelectric. When two or more of the above chiral compounds A are mixed, each content of two or more of the chiral compounds A is ferroelectric. It is preferable that it is 5 mass% or more in a crystalline liquid crystal composition.

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

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

(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 following 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 ^{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. )

  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.
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 B 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 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 display quality may be deteriorated due to changes in materials due to long-term storage / driving and temperature changes. It is.
R ⁴ may be an alkyl group or an alkoxyalkyl group, but is preferably an alkyl group.

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).

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 B is easy. On the other hand, in the case of fluorine atoms, there is an advantage that the magnitude of the spontaneous polarization of the liquid crystal molecules can be increased and the response speed can be increased.
Y ¹ may be —CH ₃ or a fluorine atom, and among them, —CH ₃ is preferable. This is because the chiral compound B can be easily synthesized as described above, the chiral compound B can be stably produced, and a 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.

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.
When all of X ^{9 to} X ²⁰ are hydrogen atoms, the solubility of the chiral compound B decreases, so that the synthesis and purification of the chiral compound B becomes difficult, the cost increases, and the ferroelectric liquid crystal The composition is easily crystallized, and the desired impact resistance may not be obtained. On the other hand, when at least one of X ^{9 to} X ²⁰ is —CH ₃ , —CF ₃ or a halogen atom as in the present invention, the solubility of the chiral compound B in the solvent increases, Synthesis and purification become possible. In addition, since the steric structure of the chiral compound B is distorted and the crystallization of the ferroelectric liquid crystal composition is inhibited by the 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. That is, the total number of substituents of the three benzene rings to which X ^{9 to} X ²⁰ are bonded is preferably 1 or 2.

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. That is, it is also preferable that the total number of substituents of the three benzene rings to which X ^{9 to} X ²⁰ are bonded is 2, and that one benzene ring has two substituents. Among them, it is preferable that the benzene ring to which X ⁹ , X ¹⁰ , X ¹⁵ , X ¹⁶ or X ¹¹ , X ¹² , X ¹⁷ , X ¹⁸ is 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.

Furthermore, it is also preferable that the total number of substituents of the three benzene rings to which X ^{9 to} X ²⁰ are bonded is 3 to 8. This is because when the total number of substituents is large, crystallization of the ferroelectric liquid crystal composition can be suppressed. In particular, the total number of substituents is preferably 3 to 5, and more preferably 3.
When the three benzene rings to which X ^{9 to} X ²⁰ are bonded have a total of 3 to 8 substituents, X ¹¹ , X ¹² , X ¹⁷ and X ¹⁸ are bonded as the positions of the substituents. Benzene ring having two substituents, benzene ring to which X ⁹ , X ¹⁰ , X ¹⁵ , and X ¹⁶ are bonded, and X ¹³ , X ¹⁴ , X ¹⁹ , and X ²⁰ are bonded to each other It is preferable that 0 to 3 benzene rings each have 1 to 6 substituents in total. In this case, crystallization of the ferroelectric liquid crystal composition can be effectively suppressed, and the liquid crystal display element can be driven stably at a low temperature. Moreover, it can prevent that content of the chiral compound in a ferroelectric liquid-crystal composition is restrict | limited. Among them, the benzene ring to which X ¹¹ , X ¹² , X ¹⁷ and X ¹⁸ are bonded has two substituents, and the benzene ring to which X ⁹ , X ¹⁰ , X ¹⁵ and X ¹⁶ are bonded is 1 It preferably has ~ 3 substituents. This is because, among the directly bonded benzene rings, the benzene ring located in the middle has a substituent, so that the crystallization of the ferroelectric liquid crystal composition is effectively suppressed.
Since the total number of substituents is preferably 3, the benzene ring to which X ¹¹ , X ¹² , X ¹⁷ and X ¹⁸ are bonded has two substituents, and X ⁹ , X ^The benzene ring to which ¹⁰ , X ¹⁵ , and X ¹⁶ are bonded, or the benzene ring to which X ¹³ , X ¹⁴ , X ¹⁹ , and X ²⁰ are bonded preferably has one substituent. Among them, the benzene ring to which X ¹¹ , X ¹² , X ¹⁷ and X ¹⁸ are bonded has two substituents, and the benzene ring to which X ⁹ , X ¹⁰ , X ¹⁵ and X ¹⁶ are bonded. More preferably, the benzene ring having one substituent has one substituent. This is because, as described above, when the benzene ring located in the middle has a substituent, crystallization of the ferroelectric liquid crystal composition is effectively suppressed.
In this case, examples of the substituent that the benzene ring has include a benzene ring to which X ⁹ , X ¹⁰ , X ¹⁵ and X ¹⁶ are bonded, and a benzene ring to which X ¹³ , X ¹⁴ , X ¹⁹ and X ²⁰ are bonded. substituents _-CH 3 which has, preferably a -CF ₃ or a halogen atom, is preferably Among them, -CH _3. ^Further, it is preferable that ^{X 11, X 12, X 17} , substituent group of the benzene ^{ring X 18} is attached is a fluorine atom.
In particular, when the total number of substituents is 3, X ⁹ or X ¹⁰ is preferably —CH ₃ , and X ¹¹ and X ¹² are preferably fluorine atoms.

  Specific examples of the chiral compound B represented by the above formula (2) include chiral compounds B represented by the following general formulas (2-3) to (2-12).

(In the above formulas (2-3) to (2-12), R ¹² is a saturated or unsaturated alkyl group having 1 to 10 carbon atoms, * represents a chiral center, and m is 0 or 1. , V is 4 to 18, and X ^{31 to} X ³⁴ each independently represent —CH ₃ , —CF ₃ or a halogen atom, and r, s in the above formulas (2-3) to (2-6) and Any one or two of t is 1, and the remaining is 0, and one of u and w in the above formulas (2-7) to (2-10) is 1 and the other is 0.

  In said formula (2-3)-(2-12), 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 formula ^{(2-3) ~ (2-12),} 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), (2-10) and (2-12), m is 0 or 1.
Moreover, in said formula (2-3)-(2-12), * mark shows a chiral center. In the above formulas (2-3), (2-5), (2-7), (2-9) and (2-11), the carbon atom at the 1-position is a chiral center. In the above formulas (2-4), (2-6), (2-8), (2-10) and (2-12), when m = 0, the carbon atom at the 1-position becomes a chiral center, m When = 1, the carbon atom at the 2-position is a chiral center.

In the above formulas (2-3) to (2-6) and (2-11) to (2-12), X ^{31 to} X ³⁴ 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 ³⁴ are the same as the positions of X ^{9 to} X ²⁰ described above.

  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.

  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. Hereinafter, dextrorotatory property is indicated by (+) and levorotatory property is indicated by (−).

  Specific examples of the chiral compound B represented by the above formula (2-11) include a chiral compound B represented by the following formula.

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 content of the chiral compound B in the ferroelectric liquid crystal composition is not particularly limited as long as an impact resistance effect is obtained. When the chiral compound B is used alone, the content of the chiral compound B is ferroelectric. When two or more kinds of the chiral compound B are mixed, each content of the two or more chiral compounds B is ferroelectric. It is preferable that it is 5 mass% or more in a crystalline liquid crystal composition.

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

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

  When the ferroelectric liquid crystal composition contains only the chiral compound A, the content of the chiral compound A in the ferroelectric liquid crystal composition is particularly limited as long as an impact resistance effect is obtained. is not. When one of the above chiral compounds A is used alone, the content of the chiral compound A is ferroelectric. When two or more of the above chiral compounds A are mixed, each content of two or more of the chiral compounds A is ferroelectric. It is preferable that it is 5 mass% or more in a crystalline liquid crystal composition. Among them, when the chiral compound A is used alone, the content of the chiral compound A is, and when two or more chiral compounds A are mixed, the total content of the two or more chiral compounds A is In the ferroelectric liquid crystal composition, 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. If the content of the chiral compound A is less than the above range, the desired impact resistance may not be obtained. On the other hand, if the content of the chiral compound A is more than the above range, the ferroelectric liquid crystal composition may be obtained. In some cases, the viscosity becomes high or the crystallized easily, and sufficient impact resistance may not be obtained, and it may be difficult to form a liquid crystal layer when manufacturing a liquid crystal display element. is there.

  When the ferroelectric liquid crystal composition contains only the chiral compound B, the content of the chiral compound B in the ferroelectric liquid crystal composition is particularly limited as long as an impact resistance effect is obtained. is not. When the chiral compound B is used alone, the content of the chiral compound B is ferroelectric. When two or more kinds of the chiral compound B are mixed, each content of the two or more chiral compounds B is ferroelectric. It is preferable that it is 5 mass% or more in a crystalline liquid crystal composition. Among them, when the chiral compound B is used alone, the content of the chiral compound B is, and when two or more chiral compounds B are mixed, the total content of the two or more chiral compounds B is: In the ferroelectric liquid crystal composition, 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. If the content of the chiral compound B is less than the above range, the desired impact resistance may not be obtained. On the other hand, if the content of the chiral compound B is more than the above range, the ferroelectric liquid crystal composition may be obtained. In some cases, the viscosity becomes high or the crystallized easily, and sufficient impact resistance may not be obtained, and it may be difficult to form a liquid crystal layer when manufacturing a liquid crystal display element. is there.

  Further, in the case where the ferroelectric liquid crystal composition contains only the chiral compound B, the chiral compound B1 in which the four benzene rings represented by the above formula (2-1) are directly bonded to the above formula (2). -2), the chiral compound B1 in the ferroelectric liquid crystal composition contains the chiral compound B2 in which four benzene rings and one cyclohexane ring directly bonded to each other are contained. It is preferable that it is more than the content of 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, when 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 performance can be improved.

  When the ferroelectric liquid crystal composition contains the chiral compound A and the chiral compound B, the total content of the chiral compound A and the chiral compound B in the ferroelectric liquid crystal composition is such that an impact resistance effect is obtained. If it is, it will not specifically limit, It is preferable in the range of 5 mass%-35 mass%, and it is more preferable that it exists in the range of 15 mass%-30 mass%. If the total content of chiral compound A and chiral compound B is less than the above range, the desired impact resistance may not be obtained, while the total content of chiral compound A and chiral compound B is more than the above range. In some cases, the ferroelectric liquid crystal composition has a high viscosity or is easily crystallized, so that sufficient impact resistance may not be obtained. In addition, when a liquid crystal display device is produced, a liquid crystal layer is formed. This may be difficult.

  When the ferroelectric liquid crystal composition contains the chiral compound A and the chiral compound B, the content of the chiral compound B in the ferroelectric liquid crystal composition is preferably equal to or higher than the content of the chiral compound A. 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, when 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 performance can be improved.

(2) Host liquid crystal The ferroelectric liquid crystal composition in 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. . In the phenylpyrimidine compound in which the phenyl group is substituted with a fluorine atom, the phase transition temperature of the smectic liquid crystal in the ferroelectric liquid crystal composition is widened, so that the liquid crystal display element can be driven stably at low and high temperatures. It is. Further, since the viscosity of the ferroelectric liquid crystal composition 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 phenylpyrimidine compounds include those represented by the following general formulas (4-1) to (4-4).

In the above formulas (4-1) to (4-4), 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, 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.
In particular, when the phenylpyrimidine compound is a compound in which the phenyl group is substituted with a fluorine atom, the content of the phenylpyrimidine compound in the ferroelectric liquid crystal composition is in the range of 10% by mass to 30% by mass. It is preferable. This is because if the content of the phenylpyrimidine compound is small, the above effects may not be sufficiently obtained. On the other hand, when the content of the phenylpyrimidine compound is too large, the ferroelectric liquid crystal composition is easily crystallized, so that the storage stability is deteriorated and the compound contained in the ferroelectric liquid crystal composition is precipitated, resulting in display quality. It is because there exists a possibility that it may fall.

(3) Ferroelectric liquid crystal composition The ferroelectric liquid crystal composition in 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. 10, 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 having a half V-shaped switching characteristic as exemplified in FIGS. 11A and 11B 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. 11C make the operation of liquid crystal molecules symmetrical 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.

2. 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 contains the above-described ferroelectric liquid crystal composition. .

  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 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.

  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.

C. 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.
Since the first alignment film has been described above, the description thereof is omitted here. Hereinafter, another configuration of the first alignment processing substrate will be described.

1. 1st electrode layer Although the 1st electrode layer used for this invention will not be specifically limited if it is generally used as an electrode of a liquid crystal display element, The 1st electrode layer of a 1st orientation processing board | substrate and It is preferable that at least one of the second electrode layers of the second alignment treatment substrate is 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 obtained by the present invention is driven by an active matrix system using TFTs, one of the first alignment processing substrate and the second alignment processing substrate is formed on the entire surface formed of the transparent conductor. An electrode is provided, and 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.

2. 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 mentioned preferably.

3. Other Configurations In the first alignment processing substrate in the present invention, a partition wall or a columnar spacer 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.

D. 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.
Since the second alignment film has been described above, description thereof is omitted here. The second base material, the second electrode layer, and other configurations are the same as the first base material, the first electrode layer, and other configurations in the first alignment processing substrate, respectively. Description is omitted.

E. 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.

F. In the present invention, the ferroelectric liquid crystal composition exhibits monostability, and the second alignment film is relatively the first alignment film and the second alignment film. When the positive polarity tends to be strong, display is preferably performed when a negative voltage is applied to the second electrode layer.

  FIG. 12 is a schematic diagram illustrating an example of an alignment state of liquid crystal molecules that exhibits monostability and exhibits half V-shaped switching characteristics. 12A shows a case where no voltage is applied, FIG. 12B shows a case where a negative voltage is applied to the second electrode layer, and FIG. 12C 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. 12A). When a negative voltage is applied to the second electrode layer, the liquid crystal molecules 25 are tilted from the stabilized state (broken line) to one side (FIG. 12B). 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. 12 (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. 9, D1 and D2 are the rubbing treatment directions of the first alignment film and the second alignment film, respectively, and z is the layer normal.

  In this way, when the second alignment film 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.

When the first alignment film and the second alignment film tend to have a relatively positive polarity in the second alignment film, in the no voltage applied state, as illustrated in FIG. Therefore, the spontaneous polarization Ps of the liquid crystal molecules 25 tends to face the first alignment film 4a side. At this time, as illustrated in FIG. 13A, the liquid crystal molecules 25 are aligned along the alignment treatment directions D1 and D2 of the first alignment film and the second alignment film, thereby obtaining 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 film 4b side due to the influence of the polarity of the applied voltage, as illustrated in FIG. . Also at this time, the liquid crystal molecules 25 are in a uniform alignment state as illustrated in FIG. Furthermore, 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 film 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. 13A is a schematic diagram showing the alignment state of the liquid crystal molecules from the top surface of FIG. ). FIG. 13B is a schematic diagram showing the alignment state of the liquid crystal molecules from the top surface of FIG. ).

  When no voltage is applied or when a positive voltage is applied to the second electrode layer (FIG. 8), a negative voltage is applied to the second electrode layer (FIG. 9). Due to the repulsion of the spontaneous polarization of the liquid crystal molecules with the negative polarity, the liquid crystal molecules 25 rotate by about 2θ 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 molecules in parallel to the first alignment treatment substrate surface.

  Thus, when the second alignment film tends to have a relatively positive polarity between the first alignment film and the second alignment film, the spontaneous polarization of the liquid crystal molecules tends to be directed to the first alignment film 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. 15, polarizing plates 17a and 17b are provided on the outer sides of 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 film 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. Further, in the ferroelectric liquid crystal, as illustrated in FIG. 12A, the position A (direction of the liquid crystal molecules 25), the position B (rubbing treatment directions D1, D2), and the position C are not necessarily coincident. Do not mean. Therefore, as illustrated in FIG. 12B, 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, for example, as shown in FIG. 11, 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. 12 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 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. 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 film and the second alignment film tend to have a relatively positive polarity in the second alignment film, the first alignment process substrate is common to the TFT substrate and the second alignment process substrate. An electrode substrate is preferred.

  For example, in the liquid crystal display element 1 shown in FIG. 16, when the gate electrode 26x is set to a high potential of about 30V, the TFT element 27 is switched on, and the 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. 16, 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 film and the second alignment film, when the second alignment film 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 film side. That is, in the switch-off state, as illustrated in FIG. 17, 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 as shown in Table 1 below using ab of chiral compound A and 1-2 of chiral compound B shown below.

(Production of liquid crystal display element)
First, resin spacers having a circular shape of Φ5.0 μm and a height of 2.5 μm were formed on an ITO-coated glass substrate 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.
Next, a sealing material was applied in a square frame shape on the substrate. On the substrate, the above-mentioned ferroelectric liquid crystal composition was applied in the form of dots, and the two substrates were assembled and thermocompression bonded so that the rubbing treatment direction was parallel and parallel or antiparallel. Thereafter, the liquid crystal cell was cooled to align the ferroelectric liquid crystal composition.

(Evaluation)
When the obtained liquid crystal display element is observed and a domain having a different extinction position is generated as illustrated in FIG. 18A, “x” is generated, and a domain having a different extinction position is illustrated in FIG. 18B. When it did not occur, it was evaluated as “◯”.

[Example 2]
(Ferroelectric liquid crystal composition)
A ferroelectric liquid crystal composition was prepared in the same manner as in Example 1 except that c to h of chiral compound A and 3 to 8 of chiral compound B shown in Table 3 were used. When the total content of the chiral compounds was 15% by mass, each content of the host liquid crystals I to III was 28.3% by mass. The dextrorotatory property is indicated by (+) and the levorotatory property is indicated by (−).

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

(Evaluation)
1) Orientation Evaluation was performed in the same manner as in Example 1.
2) 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 of the measurement, either of the chiral compounds contained in the ferroelectric liquid crystal composition is compared with the case where the chiral compound contained in the ferroelectric liquid crystal composition does not have two fluorine atoms in the substituent. The tilt angle was increased when this chiral compound had two fluorine atoms in the substituent. Further, among the chiral compounds contained in the ferroelectric liquid crystal composition, the chiral compound contained in the ferroelectric liquid crystal composition is compared with the case where any one of the chiral compounds has two fluorine atoms in the substituent. In any case, the tilt angle was larger when the substituent had two fluorine atoms.
3) Transmittance The transmittance of the liquid crystal display element was measured.
The transmittance is calculated from the tilt angle, and is a value when the transmittance when the tilt angle is 45 degrees is 100%. This value is an average value of the transmittance when a positive voltage (+10 V) is applied and the transmittance when a negative voltage (−10 V) is applied.
As a result of the measurement, the transmittance increased with the above-described tilt angle, and the same tendency as the tilt angle was obtained.
Tables 4 and 5 show the evaluation results of orientation, tilt angle, and transmittance.

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 Processing substrate 11b ... Second alignment processing substrate 25 ... Liquid crystal molecules D1, D2 ... Rubbing processing direction Ps ... Spontaneous polarization z ... Layer normal

Claims (2)

A first alignment 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 and rubbed;
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 rubbed;
A liquid crystal display device comprising a liquid crystal layer formed between the first alignment film and the second alignment film and including a ferroelectric liquid crystal composition,
The first alignment film and the second alignment film are arranged so that the rubbing treatment directions are parallel,
The ferroelectric liquid crystal composition contains at least one chiral compound of a chiral compound A represented by the following general formula (1) and a chiral compound B represented by the following general formula (2). Liquid crystal display element.

(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. )   The liquid crystal display element according to claim 1, wherein the constituent material of the first alignment film and the constituent material of the second alignment film have different compositions.

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