JP2013147592A - Ferroelectric liquid crystal composition and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric liquid crystal composition with which the birefringence can be reduced.SOLUTION: The ferroelectric liquid crystal composition contains at least either a compound represented by general formula (1) or a compound represented by general formula (2) as a birefringence improvement agent (wherein each of Rand Ris an alkyl group; X is a single bond or a pyrimidine ring; Y is a single bond or a cyclohexane ring; each of Zto Zis H or F; and m and n are 0 or 1).

Description

  The present invention relates to a ferroelectric liquid crystal composition having a small birefringence and a liquid crystal display device using the same.

  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. .

Since the ferroelectric liquid crystal has a large birefringence, in the liquid crystal display element using the ferroelectric liquid crystal, the cell gap needs to be very narrow as less than 2 μm in order to suppress the occurrence of color shift and obtain a good white display. There is. However, when the cell gap is narrow, there is a problem that the manufacturing yield is lowered due to difficulty in forming the liquid crystal layer, occurrence of thickness unevenness, color unevenness due to thickness unevenness, display unevenness, and the like.
Therefore, a ferroelectric liquid crystal capable of realizing a good white display even in a liquid crystal display element having a large cell gap is desired.

  For the purpose of providing a liquid crystal display element that enables high-visibility black and white display by preventing coloring due to the birefringence effect, for example, Patent Document 1 discloses that the substrate has birefringence and the optical main axis of the substrate. It has been proposed that the ferroelectric liquid crystal is disposed at an angle of 30 degrees with respect to the normal of the smectic layer and the retardation difference between the substrate and the liquid crystal layer is within a predetermined range.

  Further, although it is not a ferroelectric liquid crystal, it is known that a liquid crystal material is added in order to improve display characteristics with respect to a nematic liquid crystal. For example, Patent Document 2 proposes adding a liquid crystal material having a desired birefringence or a liquid crystal material having a relatively large birefringence.

Japanese Patent No. 3225084 JP 2001-34197 A

In Patent Document 1, birefringence is improved by setting the difference in retardation between the substrate of the liquid crystal display element and the liquid crystal layer within a predetermined range, and the birefringence of the ferroelectric liquid crystal itself is not reduced.
In Patent Document 2, a liquid crystal material having a large birefringence is used.

  In order to reduce the birefringence of the ferroelectric liquid crystal, it is conceivable to add a material having a small birefringence. However, materials with low birefringence are generally weakly smectic, and when such materials are added to ferroelectric liquid crystals, the tilt angle becomes small when used in a liquid crystal display device, resulting in reduced brightness, Since the driving performance deteriorates when the temperature range of the chiral smectic C phase of the dielectric liquid crystal becomes narrow, it is not preferable in practice.

  The present invention has been made in view of the above circumstances, and can maintain the driving performance while reducing the birefringence of the ferroelectric liquid crystal composition, and even when the cell gap is large, the white color is excellent. The main object of the present invention is to provide a liquid crystal display device capable of realizing display and a ferroelectric liquid crystal composition used therefor.

  The present inventors have made various studies on the birefringence of a liquid crystal display device using a ferroelectric liquid crystal composition, and as a result, by using an additive having a specific structure, the birefringence of the ferroelectric liquid crystal composition can be obtained. The present inventors have found that it is possible to reduce the color deviation, suppress the occurrence of color misregistration, obtain a good white display, and maintain the driving performance, and have completed the present invention based on such knowledge.

  That is, the present invention contains a ferroelectric liquid crystal characterized in that it contains at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2) as a birefringence improving agent. A composition is provided.

(In the above formulas (1) and (2), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms. In the above formula (1), X is a single bond. In the above formula (2), Y is a single bond or a cyclohexane ring, Z ¹ , Z ² , Z ³ and Z ⁴ are each independently a hydrogen atom or a fluorine atom, and m, n Are each independently 0 or 1. However, Z ¹ and Z ² , or any one of Z ³ and Z ⁴ is a fluorine atom.)

  Since the ferroelectric liquid crystal composition of the present invention contains at least one of the compound represented by the above formula (1) and the compound represented by the above formula (2), birefringence can be reduced, When used in a liquid crystal display element, even if the cell gap is large, it is possible to suppress the occurrence of color misregistration and obtain a good white display and to maintain driving performance.

  Further, the ferroelectric liquid crystal composition of the present invention may further contain a compound represented by the following general formula (3) as the birefringence improving agent.

(In the above formula (3), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms, and m and n are each independently 0 or 1.)

  The present invention also includes a first alignment treatment substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment film formed on the first electrode layer; A second alignment substrate having a second substrate, a second electrode layer formed on the second substrate, and a second alignment film formed on the second electrode layer, and the first alignment film And a liquid crystal display device formed between the second alignment films and having a liquid crystal layer containing a ferroelectric liquid crystal composition, wherein the ferroelectric liquid crystal composition serves as a birefringence improving agent of the above formula (1). And a compound represented by the above formula (2) are provided. A liquid crystal display device is provided.

  According to the present invention, the ferroelectric liquid crystal composition contains at least one of the compound represented by the above formula (1) and the compound represented by the above formula (2). The birefringence of the ferroelectric liquid crystal composition can be reduced, and even when the cell gap is large, the occurrence of color misregistration can be suppressed and a good white display can be obtained, and the yield can be improved.

  In the present invention, by using at least one of the compound represented by the above formula (1) and the compound represented by the above formula (2), the birefringence can be reduced while maintaining the driving performance. Thus, it is possible to suppress the occurrence of color misregistration and realize a good white display.

It is a schematic diagram which shows an example of the orientation state of the liquid crystal molecule in this invention. It is the graph which showed the change of the transmitted light quantity with respect to the applied voltage of a liquid crystal display element. It is a schematic sectional drawing which shows an example of the liquid crystal display element of this invention. 3 is a chromaticity diagram of the liquid crystal display element in Example 1. FIG. 6 is a chromaticity diagram of a liquid crystal display element in Example 2. FIG.

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

A. Ferroelectric liquid crystal composition The ferroelectric liquid crystal composition of the present invention comprises at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2) as a birefringence improving agent. It is characterized by containing.

(In the above formulas (1) and (2), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms. In the above formula (1), X is a single bond. In the above formula (2), Y is a single bond or a cyclohexane ring, Z ¹ , Z ² , Z ³ and Z ⁴ are each independently a hydrogen atom or a fluorine atom, and m, n Are each independently 0 or 1. However, Z ¹ and Z ² , or any one of Z ³ and Z ⁴ is a fluorine atom.)

In general, the liquid crystalline compound has a structure composed of a core part, a terminal chain part, and a spacer part that connects the core part and the terminal chain part. In particular, it is known that the liquid crystalline compound constituting the ferroelectric liquid crystal composition contains a plurality of benzene rings in the core portion, and the birefringence increases as the conjugation due to the unsaturated bond increases.
On the other hand, the compounds represented by the above formulas (1) and (2) only contain one or two benzene rings or one benzene ring and one pyrimidine ring in the core portion, and are unsaturated. There is relatively little conjugation due to bonding. Therefore, it is estimated that the birefringence becomes small.
In addition, the compounds represented by the above formulas (1) and (2) contain an ester bond and a cyclohexane ring or a dioxacyclohexane ring, and have a bent shape. That is, the birefringence becomes smaller.
Furthermore, since the compounds represented by the above formulas (1) and (2) contain a fluorine atom as a substituent in the benzene ring in the core portion, the steric structure is distorted. It becomes even smaller.
Therefore, birefringence can be reduced by adding the compounds represented by the above formulas (1) and (2) to the ferroelectric liquid crystal composition. Therefore, even when used in a liquid crystal display element having a relatively large cell gap, it is possible to suppress the occurrence of color misregistration and obtain a good white display.

In addition, since the compounds represented by the above formulas (1) and (2) have a carbon number of the alkyl group in the terminal chain portion within a predetermined range, even if added to the ferroelectric liquid crystal composition, the liquid crystal display When used in an element, the tilt angle is not significantly reduced, and the temperature range of the chiral smectic C phase of the ferroelectric liquid crystal composition is not significantly reduced.
Furthermore, since the compounds represented by the above formulas (1) and (2) contain a fluorine atom as a substituent in the benzene ring in the core portion, the phase transition temperature of the chiral smectic C phase is widened. When this ferroelectric liquid crystal composition is used for a liquid crystal display element, the liquid crystal display element can be driven stably at low and high temperatures.
Therefore, when the ferroelectric liquid crystal composition of the present invention is used for a liquid crystal display element, it is possible to obtain good driving performance.

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

1. Birefringence improving agent The ferroelectric liquid crystal composition of the present invention contains at least one of a compound represented by the above formula (1) and a compound represented by the above formula (2) as a birefringence improving agent. The compounds represented by the above formulas (1) and (2) can reduce birefringence when added to the ferroelectric liquid crystal composition by having the above-mentioned specific structure, thereby improving birefringence. It can be used as an agent.

(1) Compound represented by the above formula (1) In the above formula (1), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms. X is a single bond or a pyrimidine ring.

R ¹ and R ² have 5 to 10 carbon atoms. When the number of carbon atoms is larger than the above range, the tilt performance of the liquid crystal molecules in the ferroelectric liquid crystal composition becomes small, and the driving performance such as insufficient brightness may be deteriorated. On the other hand, when the number of carbon atoms is less than the above range, the ferroelectric liquid crystal composition may not exhibit a smectic phase. If the smectic phase does not appear, the tilt angle of the liquid crystal molecules is reduced, the orientation of the liquid crystal molecules is adversely affected, or the temperature range of the chiral smectic C phase as the ferroelectric liquid crystal composition is narrowed. When the carbon number is within the above range, the tilt angle of the liquid crystal molecules can be increased and good driving performance can be obtained.

In R ¹ and R ² , the alkyl group may be saturated or unsaturated.

In R ¹ and R ² , the alkyl group may be linear or branched, but is preferably linear. This is because the smectic property may be lowered in the branched state.

  Examples of the compound represented by the above formula (1) include compounds represented by the following general formulas (1-1) and (1-2).

In the above formulas (1-1) and (1-2), R ¹ and R ² are the same as described above.

  Specific examples of the compound represented by the above formula (1) include compounds represented by the following formula.

  As a compound represented by the said Formula (1), 1 type may be used independently and 2 or more types may be mixed and used.

  The compound represented by the above formula (1) is, for example, a method described in JP-T-8-504754, Patent No. 2813396, Liquid Crystals 1989, Vol.5, No.1, pp159-170. Can be synthesized.

(2) Compound represented by the above formula (2) In the above formula (2), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms. Y is a single bond or a cyclohexane ring. Z ¹ , Z ² , Z ³ and Z ⁴ are each independently a hydrogen atom or a fluorine atom. However, ^{one set} of Z ¹ and Z ² or Z ³ and Z ⁴ is a fluorine atom. m and n are each independently 0 or 1.

R ¹ and R ² are the same as in the above formula (1).

  Examples of the compound represented by the formula (2) include compounds represented by the following general formulas (2-1) and (2-2). Furthermore, examples of the compounds represented by the formulas (2-1) and (2-2) include compounds represented by the following general formulas (2-3) to (2-9).

In the above formulas (2-1) to (2-9), R ¹ , R ² , Y, Z ¹ , Z ² , Z ³ , Z ⁴ , m and n are the same as above.

  Specific examples of the compound represented by the above formula (2) include compounds represented by the following formula.

  As a compound represented by the said Formula (2), 1 type may be used independently and 2 or more types may be mixed and used.

  The compound represented by the above formula (2) is, for example, a method described in JP-T-8-504754, Patent No. 2813396, Liquid Crystals 1989, Vol. 5, No. 1, pp159-170. Can be synthesized.

(3) Compound Represented by the following Formula (3) The ferroelectric liquid crystal composition of the present invention may further contain a compound represented by the following general formula (3) as a birefringence improving agent. The compound represented by the following formula (3) was added to the ferroelectric liquid crystal composition by having a specific structure as described above, similarly to the compounds represented by the above formulas (1) and (2). In some cases, the birefringence can be reduced and can be used as a birefringence improving agent.

(In the above formula (3), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms, and m and n are each independently 0 or 1.)

R ¹ and R ² are the same as in the above formula (1), and m and n are the same as in the above formula (2).

  Specific examples of the compound represented by the above formula (3) include compounds represented by the following formula.

  As a compound represented by the said Formula (3), 1 type may be used independently and 2 or more types may be mixed and used.

  The compound represented by the above formula (3) is, for example, a method described in JP-T-8-504754, Patent No. 2813396, Liquid Crystals 1989, Vol.5, No.1, pp159-170. Can be synthesized.

(4) Birefringence improving agent The ferroelectric liquid crystal composition of the present invention contains at least one of a compound represented by the above formula (1) and a compound represented by the above formula (2) as a birefringence improving agent. It may contain only the compound represented by the above formula (1), may contain only the compound represented by the above formula (2), and is represented by the above formula (1). Both the compound represented by said formula and the compound represented by said Formula (2) may be contained.

  The ferroelectric liquid crystal composition of the present invention may further contain a compound represented by the above formula (3) as a birefringence improving agent, and is a compound represented by the above formula (3). May be contained, and the compound represented by the above formula (3) may not be contained.

  The content of the birefringence improving agent in the ferroelectric liquid crystal composition is not particularly limited as long as the birefringence can be reduced, but is 5% by mass to 80% by mass in the ferroelectric liquid crystal composition. % Is preferable. If the content of the birefringence improving agent is small, the effect of reducing the birefringence may not be sufficiently obtained, and if the content of the birefringence improving agent is large, the driving performance may be deteriorated. .

2. Chiral Compound A ferroelectric liquid crystal composition usually contains a chiral compound.
As the chiral compound used in the present invention, those generally used as a chiral compound of a ferroelectric liquid crystal composition can be used. Note that the chiral compound does not need to have smectic properties and does not need to exhibit liquid crystallinity.

  In order to reduce the birefringence of the entire ferroelectric liquid crystal composition, the chiral compound preferably has a small birefringence, and the number of benzene rings constituting the chiral compound is preferably small. In addition, for example, when the chiral compound is one in which two or more benzene rings are directly bonded, the number of benzene rings constituting the chiral compound is relatively large, and the birefringence of the chiral compound is increased. However, in the present invention, the birefringence of the entire ferroelectric liquid crystal composition can be reduced by adding the above-described birefringence improving agent.

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

  The content of the chiral compound in the ferroelectric liquid crystal composition can be, for example, about 5% by mass to 35% by mass.

3. Other Compounds The ferroelectric liquid crystal composition of the present invention may contain other compounds in addition to the birefringence improving agent and the chiral compound.
As other compounds, those generally used in ferroelectric liquid crystal compositions can be used, and examples thereof include phenylpyrimidine compounds.
A phenyl pyrimidine compound may be used individually by 1 type, and 2 or more types may be mixed and used for it.

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 one Any of a tricyclic compound having a 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.

  Moreover, it is preferable that the phenyl pyrimidine compound has a phenyl group substituted with a fluorine atom. This is because such a phenylpyrimidine compound has low birefringence.

  The content of the other compound in the ferroelectric liquid crystal composition is not particularly limited as long as the content of the birefringence improving agent and the chiral compound can be within the above ranges.

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

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

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

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

  Among the ferroelectric liquid crystal compositions exhibiting monostability, it is preferable that they exhibit half V-shaped switching characteristics as exemplified in FIGS. 2 (a) and 2 (b). When a ferroelectric liquid crystal composition exhibiting such a half V-shaped switching characteristic is used, the opening time as a black and white shutter can be made sufficiently long, whereby each color that can be temporally switched can be displayed brighter. This is because a bright color liquid crystal display element can be realized.

  The “half V-shaped switching characteristic” refers to an electro-optical characteristic in which the amount of transmitted light is asymmetric with respect to an applied voltage. Specifically, the transmitted light amount of the applied voltage when the transmitted light amount is small out of the transmitted light amount with respect to the applied voltage when a positive and negative voltage of 10 V is applied to the liquid crystal display element using the ferroelectric liquid crystal composition of the present invention. Is the characteristic that B / A is 2 or more, where A is the transmitted light amount of the applied voltage when the transmitted light amount is B.

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

B. Liquid crystal display element The liquid crystal display element of the present invention includes a first base material, a first electrode layer formed on the first base material, and a first alignment film formed on the first electrode layer. A second alignment treatment substrate having a first alignment treatment substrate, a second base material, a second electrode layer formed on the second base material, and a second alignment film formed on the second electrode layer; A liquid crystal display element formed between the first alignment film and the second alignment film and having a liquid crystal layer containing a ferroelectric liquid crystal composition, wherein the ferroelectric liquid crystal composition has improved birefringence. It contains at least one of a compound represented by the above formula (1) and a compound represented by the above formula (2) as an agent.

The liquid crystal display element of the present invention will be described with reference to the drawings.
FIG. 3 is a cross-sectional view showing an example of the liquid crystal display element of the present invention. As illustrated in FIG. 3, the liquid crystal display element 1 is formed on the first base material 2a, the first electrode layer 3a formed on the first base material 2a, and the first electrode layer 3a. The first alignment processing substrate 11a having the first alignment film 4a, the second base material 2b, the second electrode layer 3b formed on the second base material 2b, and the second electrode layer 3b A second alignment treatment substrate 11b having a second alignment film 4b; and a liquid crystal layer 5 formed between the first alignment film 4a and the second alignment film 4b. A ferroelectric liquid crystal composition containing at least one of the compound represented by the above formula (1) and the compound represented by the above formula (2) is included as an improving agent.

In the present invention, the ferroelectric liquid crystal composition contains at least one of the compound represented by the above formula (1) and the compound represented by the above formula (2), while maintaining driving performance, Birefringence can be reduced, and even when the cell gap is relatively large, the occurrence of color misregistration can be suppressed and a good white display can be obtained. Therefore, the yield can be improved.
Hereinafter, each structure in the liquid crystal display element of this invention is demonstrated.

1. Liquid Crystal Layer The liquid crystal layer in the present invention is formed between the first alignment film of the first alignment treatment substrate and the second alignment film of the second alignment treatment substrate, and is represented by the above formula (1) as a birefringence improving agent. A ferroelectric liquid crystal composition containing at least one of a compound and a compound represented by the above formula (2) is included.

  The ferroelectric liquid crystal composition has been described in detail in the above section “A. Ferroelectric liquid crystal composition”, and thus the description thereof is omitted here.

The thickness of the liquid crystal layer in the present invention 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 2.0 μm to 3.5 μm. Within range. In the present invention, since the birefringence can be reduced even if the cell gap is large, the liquid crystal layer is preferably relatively thick. Further, 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 into which the ferroelectric liquid crystal is injected with an adhesive.
In the liquid crystal dropping method, for example, first, a heated ferroelectric liquid crystal composition is dropped or applied onto the second alignment film of the second alignment processing substrate. Next, a sealant is applied to the peripheral portion of the first alignment processing substrate. Subsequently, a liquid crystal layer can be formed by stacking the first alignment treatment substrate and the second alignment treatment substrate under reduced pressure and bonding them with a sealant.

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

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

(2) First electrode layer The first electrode layer used in the present invention is not particularly limited as long as it is generally used as an electrode of a liquid crystal display element. For example, indium oxide, tin oxide, oxide A transparent electrode such as indium tin (ITO) can be used.

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

(4) Other Configurations In the first alignment treatment substrate in the present invention, partition walls or columnar spacers may be formed on the first base material. 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, a color filter type liquid crystal display element capable of realizing color display by the colored layer can be obtained.
As a method for forming the colored layer, a method for forming a colored layer in a general color filter can be used. For example, a pigment dispersion method (color resist method, etching method), a printing method, an inkjet method, or the like can be used. it can.

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

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

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

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

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

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

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

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

  The following examples illustrate the present invention in more detail.

[Example 1]
(Ferroelectric liquid crystal composition)
Using the compounds a to f shown below and the liquid crystal mixture A shown below, a ferroelectric liquid crystal composition was prepared as shown in Table 1 below.

(Production of liquid crystal display element)
First, a resin spacer having a circular shape of Φ5.0 μm and a height of 2.5 μm was formed on an ITO-coated glass substrate 1 at a pitch of 0.1 mm. Next, a photo-dimerization type photo-alignment film material (ROP103: manufactured by ROLIC) was spin-coated at a rotation speed of 1500 rpm for 30 seconds. Thereafter, after drying in an oven at 100 ° C. for 30 minutes, polarization treatment was performed.

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

  Next, a sealing material was applied in a square frame shape on the substrate. 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 directions of the respective polarization treatments were vertical. Thereafter, the liquid crystal cell was cooled to align the ferroelectric liquid crystal composition. The thickness of the liquid crystal layer was 2.5 μm.

(Evaluation)
1. Chromaticity The birefringence of the liquid crystal display element was evaluated by measuring the chromaticity by installing a lambda vision microspectroscopy system TFCAM-7000 on an Olympus polarizing microscope BX51. First, two polarizing plates in a polarizing microscope were set in a parallel state, chromaticity was measured for an empty cell not filled with a ferroelectric liquid crystal composition, and a standard light source was measured. Thereafter, the two polarizing plates in the polarizing microscope were set in a crossed Nicol state, and the liquid crystal cell filled with the ferroelectric liquid crystal composition was rotated to a position where the amount of transmitted light was maximized. The chromaticity was measured in that state.

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 a positive voltage (10 V) and a negative voltage are based on the position of black display when no voltage is applied. The angle of the liquid crystal molecules that moved when (-10 V) was applied was measured.
The evaluation results are shown in Table 2. FIG. 4 shows a chromaticity diagram.

  In the chromaticity diagram shown in FIG. 4, it can be said that the birefringence decreases in the direction of the arrow and approaches white. That is, No. 2 to which the birefringence improving agent in the present invention is added. Nos. 2 to 7 are No. 2 with no birefringence improving agent added. Compared with 1, it became close to white. In addition, No. of the present invention example. In Nos. 2 to 7, the addition of the birefringence improving agent maintained the half V-shaped switching characteristics without reducing the tilt angle.

[Example 2]
Using the liquid crystal mixture B shown below, a liquid crystal display element was prepared and evaluated in the same manner as in Example 1 except that a ferroelectric liquid crystal composition was prepared as shown in Table 3 below.
The evaluation results are shown in Table 4. FIG. 5 shows a chromaticity diagram.

  In the chromaticity diagram shown in FIG. 5, it can be said that the birefringence decreases in the direction of the arrow and approaches white. That is, No. 2 to which the birefringence improving agent in the present invention is added. Nos. 9 to 14 are No. No birefringence improving agents added. Compared with 8, it became close to white. In addition, No. of the present invention example. In Nos. 9-14, the addition of the birefringence improving agent maintained the half V-shaped switching characteristics without reducing the tilt angle.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2a ... 1st base material 2b ... 2nd base material 3a ... 1st electrode layer 3b ... 2nd electrode layer 4a ... 1st orientation film 4b ... 2nd orientation film 5 ... Liquid crystal layer 11a ... 1st orientation Processing substrate 11b ... Second alignment processing substrate 25 ... Liquid crystal molecule z ... Layer normal

Claims (3)

A ferroelectric liquid crystal composition comprising at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2) as a birefringence improving agent.
(In the above formulas (1) and (2), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms. In the above formula (1), X is a single bond. In the above formula (2), Y is a single bond or a cyclohexane ring, Z ¹ , Z ² , Z ³ and Z ⁴ are each independently a hydrogen atom or a fluorine atom, and m, n Are each independently 0 or 1. However, Z ¹ and Z ² , or any one of Z ³ and Z ⁴ is a fluorine atom.) The ferroelectric liquid crystal composition according to claim 1, further comprising a compound represented by the following general formula (3) as the birefringence improving agent.
(In the above formula (3), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms, and m and n are each independently 0 or 1.) A first alignment treatment substrate having a first substrate, a first electrode layer formed on the first substrate, and a first alignment film formed on the first electrode layer;
A second substrate having a second substrate, a second electrode layer formed on the second substrate, and a second alignment film formed on the second electrode layer;
A liquid crystal display 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 ferroelectric liquid crystal composition contains at least one of a compound represented by the following general formula (1) and a compound represented by the following general formula (2) as a birefringence improving agent. Display element.
(In the above formulas (1) and (2), R ¹ and R ² are each independently a saturated or unsaturated alkyl group having 5 to 10 carbon atoms. In the above formula (1), X is a single bond. In the above formula (2), Y is a single bond or a cyclohexane ring, Z ¹ , Z ² , Z ³ and Z ⁴ are each independently a hydrogen atom or a fluorine atom, and m, n Are each independently 0 or 1. However, Z ¹ and Z ² , or any one of Z ³ and Z ⁴ is a fluorine atom.)