Liquid crystal composition and liquid crystal display element

Abstract

To provide a liquid crystal composition and a liquid crystal display element, capable of preventing the occurrence of alignment defects.SOLUTION: The present invention provides a liquid crystal composition having spontaneous polarization, wherein a Ps variation ratio, representing a value calculated by dividing the spontaneous polarization value at 70°C by the spontaneous polarization value at 25°C, is 0.70 or more, and wherein a twist elastic constant at 25°C is 5 or more, or a twist elastic constant at 70°C is 3 or more. The present invention also provides a liquid crystal display element having the liquid crystal composition sealed therein.SELECTED DRAWING: Figure 3(c)

Description

Technical Field

[0001] The present invention relates to a liquid crystal composition and a liquid crystal display element.

Background Art

[0002] Conventionally, liquid crystal display elements used in liquid crystal display devices take advantage of the characteristics of being thin and having low power consumption, and are used in a wide range of fields. In recent years, liquid crystal display devices using ferroelectric liquid crystals (hereinafter abbreviated as FLC) having characteristics such as fast response time have been commercialized.

[0003] FIG. 1 is a (a) top view and (b) A-A cross-sectional view of a liquid crystal display element. As shown in FIG. 1, the liquid crystal display element 1 includes a first substrate 2, a second substrate 3, a spacer 4, a sealing material 5, an FLC 6, a pixel electrode 7, an alignment film 8, a counter electrode 9, an alignment film 10, an injection port 11, and a sealing material (not shown) that closes the injection port 11.

[0004] The liquid crystal molecules of the FLC 6 filled in the gap between the pair of substrates 2 and 3 are in a regularly arranged state, that is, an aligned state, by being subjected to a predetermined alignment treatment, and form a layer structure called a chevron structure that bends in a "く" shape at the center of the liquid crystal layer, and the entire liquid crystal layer exhibits a smectic C phase (SmC phase).

[0005] When injecting the FLC 6 into the gap, the FLC 6 is heated to a temperature at which the liquid crystal molecules become an isotropic phase (Iso phase) where the regularity of the molecular arrangement is lost. Then, as the temperature of the FLC 6 injected into the gap decreases, it sequentially undergoes a phase transition from the isotropic phase (Iso phase) to the nematic phase (N phase), the smectic A phase (SmA phase), and finally to the target smectic C phase (SmC phase).

[0006] The FLC 6 has a fast response, but has a problem that since the orientation order of the liquid crystal molecules is higher than that of nematic liquid crystals, it is difficult to return to the original state when the regularity of the molecular orientation is disturbed, that is, alignment defects are likely to occur.

[0007] FIG. 2 is a top view schematically showing a state in which alignment defects occur in the liquid crystal display element. As shown in FIG. 2, in the liquid crystal display element 1’, as alignment defects (alignment failures) of FLC6, there are alignment defects 12a (sometimes called “zigzag defects” or “QB defects”) that grow from the injection port 10 toward the effective pixel region 12, and alignment defects 12b (sometimes called “boat wake defects (BW defects)”) that grow from the corner of the sealant 5 located on the side opposite to the injection port 11 toward the effective pixel region 13. Such alignment defects may occur temporarily or permanently during the operation of the ferroelectric liquid crystal element 1 due to changes in the ambient temperature, changes in the voltage applied to FLC6, etc. Note that such alignment defects do not necessarily occur at the positions shown in FIG. 2, and may occur at other positions. When such alignment defects grow large and invade the effective pixel region 13 or the cut-off pixel region 14, there arises a problem that the image quality deteriorates. Therefore, a composition of FLC6 in which such alignment defects are less likely to occur is desired.

[0008] Regarding the above problems, for example, the techniques described in Patent Documents 1 and 2 are known.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] Patent Document 1 describes a method for aligning ferroelectric liquid crystals. A ferroelectric liquid crystal filled between a pair of substrates bonded to each other via a sealing material is held at a temperature at which it undergoes a phase transition from a smectic A phase to an isotropic phase for a certain period of time. During this period of holding at the temperature, an alternating electric field is applied to the ferroelectric liquid crystal. With the alternating electric field applied, the ferroelectric liquid crystal is gradually cooled, and after the temperature of the ferroelectric liquid crystal is lowered to room temperature, the application of the alternating electric field is released.

[0011] In this alignment treatment method, the temperature is gradually lowered to room temperature while an alternating voltage is applied. By releasing the application of the alternating electric field in a temperature environment where the liquid crystal viscosity is high and the liquid crystal molecules are difficult to move, the generation of new zigzag defects due to the electrical shock when the alternating electric field is released is suppressed.

[0012] However, the method described in Cited Document 1 is very effective as a re-alignment treatment for a liquid crystal display element with alignment defects, but it does not suppress the occurrence of alignment defects in the ferroelectric liquid crystal composition itself.

[0013] Also, Patent Document 2 describes mixing a polymerizable compound-containing liquid crystal to improve alignment defects, but it does not mention anything about ferroelectric liquid crystals (FLCs), pyrimidine compounds, liquid crystal compositions containing the compounds, and the compositions.

[0014] The present invention has been made in view of the above problems, and an object thereof is to provide a liquid crystal composition and a liquid crystal display element capable of suppressing the occurrence of alignment defects.

Means for Solving the Problems

[0015] A liquid crystal composition having spontaneous polarization, wherein the Ps change rate, which is the value obtained by dividing the value of the spontaneous polarization at 70°C by the value of the spontaneous polarization at 25°C, is 0.70 or more, and the twist elastic constant at 25°C is 5 or more, or the twist elastic constant at 70°C is 3 or more. Also, a liquid crystal display element in which the liquid crystal composition is enclosed.

Effects of the Invention

[0016] According to the present invention, it is possible to suppress the occurrence of alignment defects in the liquid crystal composition.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3(a)

Figure 3(b)

Figure 3(c)

Figure 4(a)

Figure 4(b)

Figure 4(c)

Figure 5(a)

Figure 5(b)

Figure 6(a)

Figure 6(b)

Figure 7

Figure 8(a)

Figure 8(b)

Figure 9

Embodiments for Carrying Out the Invention

[0018] Hereinafter, examples of the present invention will be described.

[0019] In the example of the present invention, the ferroelectric liquid crystal composition contains, as liquid crystal component materials, for example, a compound A belonging to a fluorine group (a compound having a benzene ring with a fluorine group, hereinafter sometimes referred to as a fluorine group component), a compound B belonging to a pyridine group (hereinafter sometimes referred to as a pyridine component), a compound C belonging to a thiadiazole group (hereinafter sometimes referred to as a thiadiazole component), a compound D belonging to a pyrimidine group (hereinafter sometimes referred to as a pyrimidine component), and a compound E belonging to a chiral group (hereinafter sometimes referred to as a chiral component). Specific substances of compounds A to E are not particularly limited. For example, as compound A, the compound represented by the following (Chemical Formula 1) can be mentioned.

[0020]

Chemical Formula

[0021] The above compound (Chemical Formula 1) is composed of 2,3-Difluoro-4-heptyl-4''-pentyl-1,1':4',1''-terphenyl.

[0022] Figure 3(a) is a diagram showing the relationship between the value of spontaneous polarization (Ps_25) of the ferroelectric liquid crystal composition at 25°C and the degree of BW defects generated in the ferroelectric liquid crystal composition. Figure 3(b) is a diagram showing the relationship between the value of spontaneous polarization (Ps_70) of the ferroelectric liquid crystal composition at 70°C and the degree of BW defects generated in the ferroelectric liquid crystal composition. Figure 3(c) is a diagram showing the relationship between the Ps change rate, which is the value obtained by dividing the value of spontaneous polarization (Ps_70) of the ferroelectric liquid crystal composition at 70°C by the value of spontaneous polarization (Ps_25) at 25°C (Ps_70 / Ps_25), and the degree of BW defects generated in the ferroelectric liquid crystal composition. Figures 3(a) to 3(c) are based on the experimental results of the applicant of the present application. The ● marks plotted in the graph represent one different ferroelectric liquid crystal composition each. Note that the same applies to Figures 4(a) to 4(c), Figure 5, Figures 6(a) and 6(b), Figures 8(a) and 8(b), and Figure 9 described later.

[0023] In FIG. 3(a), the horizontal axis of the graph represents the value of the spontaneous polarization (Ps_25) of the ferroelectric liquid crystal composition at 25°C, and the vertical axis of the graph represents the degree of BW defects generated in the ferroelectric liquid crystal composition. In FIG. 3(b), the horizontal axis of the graph represents the value of the spontaneous polarization (Ps_70) of the ferroelectric liquid crystal composition at 70°C, and the vertical axis of the graph represents the degree of BW defects generated in the ferroelectric liquid crystal composition. In FIG. 3(c), the horizontal axis of the graph represents the Ps change rate, which is the value obtained by dividing the value of the spontaneous polarization (Ps_70) of the ferroelectric liquid crystal composition at 70°C by the value of the spontaneous polarization (Ps_25) at 25°C, and the vertical axis of the graph represents the degree of BW defects generated in the ferroelectric liquid crystal composition.

[0024] The value of the spontaneous polarization (Ps) of the ferroelectric liquid crystal composition is a well-known parameter, and the unit is nC / cm 2 where nC is nanocoulomb.

[0025] The degree of BW defects generated in the ferroelectric liquid crystal composition is determined by the applicant of the present application by creating a liquid crystal display element (liquid crystal panel) in which the ferroelectric liquid crystal composition is encapsulated, applying a predetermined driving voltage to the liquid crystal display element, visually confirming the BW defects generated in the liquid crystal display element during this process, and grading and evaluating in three levels according to the degree of occurrence (area, etc.) as good (few BW defects): 0 points, medium: 0.5 points, bad (many BW defects): 1 point. That is, the closer this value is to 0, the less likely it is for BW defects to occur. However, here, the temperature of the liquid crystal display element in which the ferroelectric liquid crystal composition is encapsulated is changed to 50°C, 70°C, and 90°C (three temperature conditions), and the driving voltage is changed to 1.75V, 2.30V, and 2.85V for each of these temperatures (three voltage conditions), and the average value of the results evaluated under a total of nine (3×3) conditions is shown.

[0026] Based on FIGS. 3(a) to 3(c), the following can be said. When Ps at 25°C is in the range of 70 to 85 nC / cm 2 the BW defects are less likely to occur. When Ps at 25°C is in the range of 70 to 80 nC / cm 2When within the range, BW defects are less likely to occur. The upper limit value of Ps at 25°C is not particularly limited, but for example, it is 100 nC / cm 2 is. Also, when the Ps change rate is 0.60 or more, BW defects are less likely to occur. When the Ps change rate is 0.70 or more, BW defects are even less likely to occur. When the Ps change rate is 0.74 or more, BW defects are even less likely to occur. The upper limit value of the Ps change rate is not particularly limited, but for example, it is 1.1.

[0027] FIG. 4(a) is a diagram showing the relationship between the twist elastic constant (B3_25) of the ferroelectric liquid crystal composition at 25°C and the degree of BW defects generated in the ferroelectric liquid crystal composition. FIG. 4(b) is a diagram showing the relationship between the twist elastic constant (B3_70) of the ferroelectric liquid crystal composition at 70°C and the degree of BW defects generated in the ferroelectric liquid crystal composition. FIG. 4(c) is a diagram showing the relationship between the B3 change rate, which is the value (B3_70 / B3_25) obtained by dividing the twist elastic constant (B3_25) of the ferroelectric liquid crystal composition at 25°C by the twist elastic constant (B3_70) at 70°C, and the degree of BW defects generated in the ferroelectric liquid crystal composition.

[0028] In FIG. 4(a), the horizontal axis of the graph indicates the twist elastic constant (B3_25) of the ferroelectric liquid crystal composition at 25°C, and the vertical axis of the graph indicates the degree of BW defects generated in the ferroelectric liquid crystal composition. In FIG. 4(b), the horizontal axis of the graph indicates the twist elastic constant (B3_70) of the ferroelectric liquid crystal composition at 70°C, and the vertical axis of the graph indicates the degree of BW defects generated in the ferroelectric liquid crystal composition. In FIG. 4(c), the horizontal axis of the graph indicates the B3 change rate, which is the value (B3_70 / B3_25) obtained by dividing the twist elastic constant (B3_25) of the ferroelectric liquid crystal composition at 25°C by the twist elastic constant (B3_70) at 70°C, and the vertical axis of the graph indicates the degree of BW defects generated in the ferroelectric liquid crystal composition.

[0029] The twist elastic constant of liquid crystal (hereinafter sometimes referred to as B3) is a well-known parameter and is obtained, for example, by the following formula 1. The parameter obtained by formula 1 is a relative parameter of the viscosity of liquid crystal and the response speed of liquid crystal at the same temperature with the constant part normalized. B3 = γ / t ···(Formula 1) γ: Viscosity of liquid crystal t: Response speed of liquid crystal

[0030] Based on FIGS. 4(a) to 4(c), the following can be said. When B3 at 25°C is 5 or more, BW defects are less likely to occur. When B3 at 25°C is 6 or more, BW defects are even less likely to occur. The upper limit value of B3 at 25°C is not particularly limited, but is, for example, 15. Also, when B3 at 70°C is 3 or more, BW defects are less likely to occur. When B3 at 70°C is 4 or more, BW defects are even less likely to occur. The upper limit value of B3 at 70°C is not particularly limited, but is, for example, 8. Also, when the B3 change rate is within the range of 0.1 to 1, BW defects are less likely to occur.

[0031] FIG. 5(a) is a diagram showing the relationship between the content ratio (weight%) of a liquid crystal component material having a fluorine group contained in a ferroelectric liquid crystal composition and the degree of BW defects generated in the ferroelectric liquid crystal composition. FIG. 5(b) is a diagram showing the relationship between the content ratio (weight%) of a liquid crystal component material having two or more fluorine groups and three cyclic structures, excluding the chiral component and the thiadiazole component, among the liquid crystal component materials having a fluorine group contained in the ferroelectric liquid crystal composition and the degree of BW defects generated in the ferroelectric liquid crystal composition.

[0032] In FIG. 5(a), the horizontal axis of the graph indicates the content ratio (wt%) of the liquid crystal component material having a fluorine group contained in the ferroelectric liquid crystal composition, and the vertical axis of the graph indicates the degree of BW defects generated in the ferroelectric liquid crystal composition. In FIG. 5(b), the horizontal axis of the graph indicates the content ratio (wt%) of the liquid crystal component material having two or more fluorine groups and three cyclic structures, excluding the chiral component and the thiadiazole component, among the liquid crystal component materials having a fluorine group contained in the ferroelectric liquid crystal composition, and the vertical axis of the graph indicates the degree of BW defects generated in the ferroelectric liquid crystal composition. Note that the content ratio (wt%) of the liquid crystal component material indicates the ratio with respect to the total weight of the ferroelectric liquid crystal composition. Further, the cyclic structure possessed by the liquid crystal component material means a benzene ring.

[0033] Based on FIGS. 5(a) and 5(b), the following can be said. When the content ratio (wt%) of the liquid crystal component material having a fluorine group is within the range of 34% to 42%, the occurrence of BW defects becomes difficult. Further, when the content ratio (wt%) of the liquid crystal component material having two or more fluorine groups and three cyclic structures, excluding the chiral component and the thiadiazole component, among the liquid crystal component materials having a fluorine group contained in the ferroelectric liquid crystal composition is 19% to 26%, the occurrence of BW defects becomes difficult.

[0034] Examples of the liquid crystal component material having two or more fluorine groups and three cyclic structures include, but are not limited to, the compound represented by the aforementioned (Chemical Formula 1).

[0035] FIG. 6(a) is a diagram showing the relationship between the total content ratio (wt%) of the chiral component contained in the ferroelectric liquid crystal composition and the content ratio (wt%) of the liquid crystal component material having two cyclic structures and the degree of QB defects generated in the ferroelectric liquid crystal composition. FIG. 6(b) is a diagram showing the relationship between the twist elastic constant (B3_25) at 25° C. of the ferroelectric liquid crystal composition and the degree of QB defects generated in the ferroelectric liquid crystal composition.

[0036] In Fig. 6(a), the horizontal axis of the graph indicates the sum of the content ratio (weight %) of the chiral component contained in the ferroelectric liquid crystal composition and the content ratio (weight %) of the liquid crystal component material having two cyclic structures, and the vertical axis of the graph indicates the degree of QB defects generated in the ferroelectric liquid crystal composition. In Fig. 6(b), the horizontal axis of the graph indicates the twist elastic constant (B3_25) at 25°C of the ferroelectric liquid crystal composition, and the vertical axis of the graph indicates the degree of QB defects generated in the ferroelectric liquid crystal composition. Note that the content ratio (weight %) of the liquid crystal component material indicates the ratio with respect to the total weight of the ferroelectric liquid crystal composition. Further, the cyclic structure possessed by the liquid crystal component material means a benzene ring.

[0037] The degree of QB defects generated in the ferroelectric liquid crystal composition is determined by the applicant of the present application by creating a liquid crystal display element (liquid crystal panel) in which the ferroelectric liquid crystal composition is encapsulated, performing an evaluation test of leaving the liquid crystal display element in a predetermined environment, visually confirming the QB defects generated in the liquid crystal display element at that time, and considering those in which even a slight amount of QB defects are generated as defective products and those in which no QB defects are generated as non-defective products. That is, it indicates that the closer this value is to 0, the less likely it is for QB defects to occur. However, here, the results of an evaluation test of leaving a plurality of liquid crystal display elements encapsulated with the ferroelectric liquid crystal composition in an environment of a temperature of 60°C and a humidity of 90% for 1000 hours are shown. Note that since QB defects are likely to have a great adverse effect on the quality of the liquid crystal display element among the alignment defects, here, those in which even small or medium-sized QB defects are generated are regarded as defective products and evaluated in two stages.

[0038] Based on Fig. 6(a) and Fig. 6(b), the following can be said. When the sum of the content ratio (weight %) of the chiral component contained in the ferroelectric liquid crystal composition and the content ratio (weight %) of the liquid crystal component material having two cyclic structures is 36% or more, it becomes difficult for QB defects to occur. Further, when the twist elastic constant (B3_25) at 25°C is 6 or more, it becomes difficult for QB defects to occur. When the twist elastic constant (B3_25) at 25°C is 9.5 or more, it becomes even more difficult for QB defects to occur.

[0039] FIG. 7 is a diagram showing examples of Ps_25, Ps_70, Ps change rate, B3_25, B3_70, B3 change rate, degree of BW defect, and degree of QB defect of a ferroelectric liquid crystal composition. The numbers described in the "Mixtures" column of the table shown in FIG. 7 are identification numbers of the ferroelectric liquid crystal compositions uniquely assigned by the applicant of the present application, and those with different identification numbers mean different ferroelectric liquid crystal compositions.

[0040] The values of the parameters shown in FIG. 7 are merely examples and are not limited thereto. The values of Ps and B3 can be changed, for example, by appropriately adjusting the types and content ratios of the compounds contained in the ferroelectric liquid crystal composition.

[0041] By appropriately combining the numerical ranges and the like of the parameters described above, a ferroelectric liquid crystal composition and a liquid crystal display element capable of effectively suppressing the occurrence of alignment defects can be provided. How to combine the numerical ranges and the like of the parameters is free and not particularly limited, but as an example of an effective combination, for example, the Ps change rate is 0.70 or more, and the twist elastic constant (B3_25) at 25 ° C is 5 or more, or the twist elastic constant (B3_70) at 70 ° C is 3 or more. In addition to this condition, the Ps at 25 ° C is in the range of 70 to 85 nC / cm 2 within the range, the content ratio (by weight) of the liquid crystal component material having a fluorine group is in the range of 34% to 42%, or the content ratio (by weight) of the liquid crystal component material having two or more fluorine groups and three cyclic structures excluding the chiral component and the thiadiazole component among the liquid crystal component materials having a fluorine group is 19% to 26%. Further, as another example of the combination, the sum of the content ratio (by weight) of the chiral component and the content ratio (by weight) of the liquid crystal component material having a cyclic structure of two or more rings is 36% or more, and the twist elastic constant (B3_25) at 25 ° C is 6 or more.

[0042] As a ferroelectric liquid crystal composition used in a liquid crystal display element, a material in which alignment defects are less likely to occur is desired. In addition, a material having a large birefringence (Δn) is desired. Note that the birefringence (Δn) is a well-known parameter.

[0043] FIG. 8(a) is a diagram showing the relationship between the content ratio (weight %) of a liquid crystal component material having two cyclic structures and the birefringence (Δn) of a ferroelectric liquid crystal composition. FIG. 8(b) is a diagram showing the relationship between the content ratio (weight %) of a liquid crystal component material having three cyclic structures and the birefringence (Δn) of a ferroelectric liquid crystal composition. FIG. 9 is a diagram showing examples of the content ratio (weight %) of a liquid crystal component material having two cyclic structures, the content ratio (weight %) of a liquid crystal component material having three cyclic structures, and the birefringence (Δn) of a ferroelectric liquid crystal composition.

[0044] In FIG. 8(a), the horizontal axis of the graph indicates the content ratio (weight %) of a liquid crystal component material having two cyclic structures, and the vertical axis of the graph indicates the birefringence (Δn) of a ferroelectric liquid crystal composition. In FIG. 8(b), the horizontal axis of the graph indicates the content ratio (weight %) of a liquid crystal component material having three cyclic structures, and the vertical axis of the graph indicates the birefringence (Δn) of a ferroelectric liquid crystal composition. Note that the content ratio (weight %) of the liquid crystal component material indicates the ratio with respect to the total weight of the ferroelectric liquid crystal composition. In addition, the cyclic structure of the liquid crystal component material means a benzene ring.

[0045] Based on FIGS. 8(a) and 8(b), the following can be said. When the content ratio (by weight) of the liquid crystal component material having three cyclic structures is greater than the content ratio (by weight) of the liquid crystal component material having two cyclic structures, the birefringence (Δn) increases. When the content ratio (by weight) of the liquid crystal component material having three cyclic structures is 90% or more, the birefringence (Δn) becomes even greater. When the content ratio (by weight) of the liquid crystal component material having three cyclic structures is 100%, that is, when the ferroelectric liquid crystal composition is composed only of the liquid crystal component material having three cyclic structures, the birefringence (Δn) becomes even greater. Also, based on the presumption that the same can be said regarding the relationship between the sum of the content ratios (by weight) of the liquid crystal component materials having two or more (one or two) cyclic structures and the sum of the content ratios (by weight) of the liquid crystal component materials having three or more cyclic structures, the following can be said. When the sum of the content ratios (by weight) of the liquid crystal component materials having three or more cyclic structures is greater than the sum of the content ratios (by weight) of the liquid crystal component materials having two or less (one or two) cyclic structures, the birefringence (Δn) increases. When the sum of the content ratios (by weight) of the liquid crystal component materials having three or more cyclic structures is 90% or more, the birefringence (Δn) becomes even greater. When the content ratio (by weight) of the liquid crystal component materials having three or more cyclic structures is 100%, that is, when the ferroelectric liquid crystal composition is composed only of the liquid crystal component materials having three or more cyclic structures, the birefringence (Δn) becomes even greater.

[0046] FIG. 9 is a diagram showing examples of the content ratio (by weight) of the liquid crystal component material having two cyclic structures, the content ratio (by weight) of the liquid crystal component material having three cyclic structures, and the birefringence (Δn) of the ferroelectric liquid crystal composition. The numbers described in the "Mixtures" column of the table shown in FIG. 9 are identification numbers of the ferroelectric liquid crystal compositions uniquely assigned by the applicant of the present application, and those with different identification numbers mean different ferroelectric liquid crystal compositions.

[0047] The values of the parameters shown in FIG. 9 are merely examples and are not limited thereto. The birefringence (Δn) of the ferroelectric liquid crystal composition can be changed, for example, by appropriately adjusting the content ratio (by weight) of the liquid crystal component material having two cyclic structures and the content ratio (by weight) of the liquid crystal component material having three cyclic structures.

[0048] By appropriately combining the numerical ranges of the parameters described above, etc., it is possible to provide a ferroelectric liquid crystal composition and a liquid crystal display element in which alignment defects are less likely to occur and the birefringence is large. How to combine the numerical ranges of the parameters, etc. is free and not particularly limited, but as an example of an effective combination, for example, the Ps change rate is 0.60 or more, and the total content ratio (by weight) of the liquid crystal component material having three or more cyclic structures is greater than the total content ratio (by weight) of the liquid crystal component material having two or less (one or two) cyclic structures. Also, the Ps change rate is 0.60 or more, and the content ratio (by weight) of the liquid crystal component material having three cyclic structures is greater than the content ratio (by weight) of the liquid crystal component material having two cyclic structures.

[0049] The present invention is not limited to the above embodiments and can take other embodiments. The present invention is not limited to ferroelectric liquid crystals and can also be applied to other liquid crystals having spontaneous polarization (antiferroelectric liquid crystals, ferroelectric nematic liquid crystals, etc.).

Explanation of Symbols

[0050] 1 Liquid crystal display element 1’ Liquid crystal display element 2 First substrate 3 Second substrate 4 Spacer 5 Sealant 6 Ferroelectric liquid crystal (FLC) 7 Pixel electrode 8 Alignment film 9 Counter electrode 10 Alignment film 11 Injection port 12a Alignment defect (zigzag defect, QB defect) 12b Alignment defect (boat wake defect) 13 Effective pixel area 14 Cutoff pixel area

Claims

1. A liquid crystal composition having spontaneous polarization, wherein the Ps change rate, which is the value obtained by dividing the value of spontaneous polarization at 70 °C by the value of spontaneous polarization at 25 °C, is 0.70 or more, and the twist elastic constant at 25 °C is 5 or more, or the twist elastic constant at 70 °C is 3 or more. A liquid crystal composition characterized by this.

2. The liquid crystal composition according to claim 1, wherein the Ps change rate is 0.74 or more.

3. The value of the spontaneous polarization at 25 °C is 70 to 85 nC / cm 2 The liquid crystal composition according to claim 1, characterized in that it is so.

4. The liquid crystal composition according to claim 1, wherein the content ratio (by weight) of the compound having a fluorine group is 34% to 42%.

5. Among the compounds having a fluorine group, the content ratio (by weight) of the compound having two or more fluorine groups and three cyclic structures, excluding the chiral component and the thiadiazole component, is 19% to 26%. The liquid crystal composition according to claim 1, characterized by this.

6. A liquid crystal display element in which the liquid crystal composition described in any one of claims 1 to 5 is enclosed.

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