JP2013155309A - Liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal element in which a large electroclinic coefficient capable of producing a satisfactory tilt is provided in a wide temperature range.SOLUTION: The liquid crystal element includes: a first substrate; a second substrate; a liquid crystal layer containing a liquid crystal composition, inserted between the first substrate and the second substrate; and an electrode for controlling the liquid crystal layer on at least one side of the substrates, wherein the liquid crystal composition exhibits a smectic A (SmA) phase, contains at least two kinds of liquid crystal compounds and each liquid crystal compound has a smectic C (SmC) phase by itself.

Description

  The present invention relates to a liquid crystal element useful as a constituent member of a liquid crystal TV or the like.

Ferroelectric liquid crystal replaces the current nematic liquid crystal as a new material used in next-generation high-speed liquid crystal display. In 1979, RBMeyer discovered ferroelectric design and ferroelectric liquid crystal, early 1980, surface stability by Clark-Lagerwall. Beginning with reports of bistability due to computerization, many companies have been researching to achieve this in the 1980s and 1990s. Unfortunately, as a liquid crystal display cell, the problem of alignment failure and operation failure in a state in which horizontal alignment is forced between glass substrates with electrodes has not been solved, and now it is almost forced to withdraw.
_A recent research flow using a ferroelectric liquid crystal (SmC ^* ) phase and an antiferroelectric liquid crystal (SmC _A ) phase includes, for example, the following.

a) In the research flow of ferroelectric liquid crystals, there is a technology invented by Dr. Keisuke Kobayashi, Yamaguchi Tokyo University of Science, called “polymer-stabilized ferroelectric liquid crystals”. This technology mixes acrylate monomers with a liquid crystal skeleton in a ferroelectric liquid crystal, creates a horizontally aligned cell, and then irradiates UV light to collapse the bistability of the ferroelectric liquid crystal. By trying to be monostable, it is intended to prevent the appearance of disorder of orientation. Although the feature of bistability is lost, there is an advantage that uniform orientation is easily realized instead (see, for example, Non-Patent Document 1).
On the other hand, due to the driving method (IPS) of nematic liquid crystal developed by Hitachi in recent years, ferroelectric liquid crystal is also dared, and the smectic layer is parallel to the glass substrate, not horizontal alignment, which cannot solve the problem. Several attempts to use orientation have begun.

b) In the Hideo Takezoe lab at Tokyo Institute of Technology and the Chelsuke lab at Halle University in Germany, SmA (Smectic A) produced by liquid crystal molecules called banana-shaped liquid crystals (discovered in the Watanabe Sequential Laboratory at Tokyo Institute of Technology). Attempts have been made to induce birefringence in the) phase by applying a horizontally oriented electric field. In the SmA phase of the banana-shaped molecule, the banana bending direction of the banana-shaped molecule is directed in various directions, but the banana-shaped molecule has spontaneous polarization in the banana bending direction (see, for example, Non-Patent Document 2). Therefore, when a strong electric field is applied, the polarization is unevenly distributed in the electric field direction. At the same time, the refractive index anisotropy of the banana-shaped molecule (two axes along the banana curve, not in the molecular long axis direction). The light transmission due to birefringence can be controlled by an electric field.
As a problem, the direction of the short axis direction of the banana-shaped molecule is basically going to be a thermally random direction in the SmA phase (= liquid, disordered phase). On the other hand, in the case of the SmC ^* (chiral smectic C) phase, the change is induced by a small force cooperatively (= liquid crystal layer, ordered phase) that spontaneously tries to go in the same direction. In other words, the driving force is large because it uses spontaneous polarization, but basically a large electric field is required because it is a deformation of the Kerr effect that induces molecular orientation in the liquid by an external field. At the same time, the anisotropy in the short axis direction (due to the bending of the banana) of the banana-type liquid crystal is not so large from the molecular shape, and the induced refractive index anisotropy is also small at present. Further, in order to obtain a large birefringence, a large driving voltage is required, which is practically difficult.

c) A method invented by a joint research between Associate Professor Takanishi (co-researcher of the present invention) of Kyoto University and Hitachi, Ltd. as a method using paraelectric drive in the spiral maintaining state of the antiferroelectric liquid crystal. In 2010, a patent application was filed (see Non-Patent Document 3). When a strong / antiferroelectric liquid crystal is vertically aligned in a liquid crystal cell and encapsulated, the C-director (a vector indicating the direction in which the liquid crystal molecules in the layer are tilted) rotates between layers to draw a spiral ( Clark-Lagerwall's method used a horizontal orientation to unwind the helix). This property is an essential property of a chiral liquid crystal, like the cholesteric phase. For this reason, birefringence is not shown when the liquid crystal cell is viewed from above. In the above-described principle of the banana type liquid crystal of b), this state (electric field 0) is used as a black state. Here, when a horizontal electric field is applied in the same manner as the polymer-stabilized ferroelectric liquid crystal of a) described above, in the antiferroelectric phase, the spontaneous polarization is canceled in the adjacent layer, so that the C-director direction is applied. Due to the paraelectric anisotropy of the liquid crystal molecules that are tilted toward, a torque that aligns the C-director in the direction of the electric field works. As a result, when the cell is viewed from above, the refractive index anisotropy is reduced. This occurs and transmitted light appears due to birefringence. In this method, if the electric field strength is further increased, the state is changed to the ferroelectric state, and further rotation occurs so that the C-director is perpendicular to the electric field. As the liquid crystal display element, a region of electric field strength that maintains antiferroelectricity is used. The continuous retardation change can be adjusted by the balance between the torsional force to maintain the spiral and the electric field. In this area, a driving speed of 10 to 100 μsec, which is 10 to 1000 times that of the current display, can be realized.
The problem is that the birefringence is generated using the distortion of the spiral while maintaining the spiral, so the absolute value of the birefringence is as small as the banana-type liquid crystal, and the liquid crystal layer is not thick enough. However, when the thickness of the liquid crystal layer is increased, the existing IPS electrode does not generate a sufficient electric field. In addition, the driving force must not be increased by the electric field because the driving must be performed below the electric field strength at which the transition to the F (ferroelectric) state occurs. Also, the driving voltage needs to be high enough to distort the spiral, like the banana-type liquid crystal.

  d) The polymer-stabilized blue phase is a technology invented by Mr. Hiroki Kikuchi of Kyushu University in 2002 (for example, Patent Document 1, Hiroki Kikuchi, Chisato Hiyama, “Liquid Crystal Material for Optical Modulator”, Independent Administrative Institution In the Science and Technology Agency), the temperature range of the blue phase is reduced to several tens by spontaneously agglomerating polymerizable molecules to defects in the liquid crystal order in the blue phase and photopolymerizing in the blue phase state. It has succeeded in expanding and stabilizing ℃. Unlike the polymer-stabilized liquid crystal phase a) described above, a material polymerized by polymerization exists locally in the liquid crystal phase. However, in the polymer-stabilized blue phase, it is necessary to polymerize it by targeting a place where only a special liquid crystal phase such as a blue phase is called a “defect” in the liquid crystal order.

The above attempt is a method of controlling the transmission of light by the movement of the tilted molecules in the declination (azimuth) direction in an ordered phase (SmC ^* , SmC _A, etc.) in which the molecular tilt in the layer has a finite value. A mode in which the liquid crystal molecules 11 move on the apparent cone 12 while maintaining a certain inclination (see FIG. 1B) is called a goldstone mode and is described as a C-director motion. Compared to the movement of nematic liquid crystal directors used in current liquid crystal displays, the movement of this C-director (Goldstone mode) has a feature that the response speed is 2 to 3 digits faster.

On the other hand, the operation principle of a high-speed light valve using the electroclinic effect in the SmA phase adjacent to the high temperature side has been proposed for some time. The electroclinic effect is an effect in which the tilt of molecules in the layer is induced by aligning the spontaneous polarization in the electric field direction in a system in which chiral symmetry is broken. When the extinction position is perpendicular to the layer, transmitted light due to birefringence is generated with the occurrence of tilt. The movement of the liquid crystal molecules 11 related to the tilt with respect to the layer normal 13 is called a soft mode (see FIG. 1A), and a response speed that is one to two orders of magnitude faster than the high-speed goldstone mode is expected. High-speed response is one of the most notable liquid crystal application technologies. However, the coupling coefficient strongly depends on the temperature difference from the SmA-SmC ^* phase transition point, and shows a critical phenomenon in which the coupling coefficient diverges near the transition point, but becomes extremely small at temperatures far from the transition point. Does not generate tilt.
There are various literatures and patents regarding the application of the electroclinic effect, but because of the induced order (tilt) in the phase where the molecules are not tilted on average (SA phase), the absolute value is small and practically problematic. There is. SmA-SmC ^{* Although} a large coupling coefficient can be expected near the phase transition point due to a critical phenomenon, the temperature dependence of the electroclinic coefficient is large, and stable display cannot be performed.

Japanese Patent No. 3779937

Tokyo University of Science, Furue Laboratory, “Polymer Stabilized Liquid Crystal”, [online], 2006, [searched on January 13, 2012], Internet <URL: http://www.rs.noda.tus.ac .jp / ~ furuelab / introduction / ps.html> Tokyo Institute of Technology, Takezoe and Ishikawa Laboratory, “Developing an ideal display with banana-shaped liquid crystal”, [online], 2006, [searched on January 13, 2012], Internet <URL: http: // www. op.titech.ac.jp/lab/Take-Ishi/Japanese/Research/Highlight/jjap.html> Kyoto University Soft Matter Physics Laboratory, “Electric field response of antiferroelectric liquid crystal”, [online], September 11, 2011, [Search January 13, 2012], Internet <URL: http: // softmatter.scphys.kyoto-u.ac.jp/studySCA.html>

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal element in which a large electrical gradient coefficient capable of generating a sufficient tilt is obtained in a wide temperature range.

In the mixed system of two kinds of two kinds of liquid crystal compounds exhibiting the SmA-SmC phase transition, the present inventor stabilizes a phase called Induced SmA in an intermediate concentration region, and exhibits a SmA-SmC phase transition in a wide temperature range. We found that a critical phenomenon occurs. In this mixed system, the SmC phase of the compound on one side becomes the “hindered SmC” phase and causes this abnormal critical phenomenon. In such a mixture, the same effect was exerted on the electroclinic coefficient, and it was found that a uniform and large electroclinic coefficient was obtained in a wide temperature range, and the present invention was completed. The material of the mixture is designed using this anomalous critical phenomenon, and can be applied to a liquid crystal display device using an ultrafast soft mode originating from the electric field induced tilt in the SmA phase.
That is, the present invention includes a first substrate, a second substrate, and a liquid crystal layer containing a liquid crystal composition between the first substrate and the second substrate, and at least one of the substrates includes: A liquid crystal element having an electrode for controlling the liquid crystal layer, wherein the liquid crystal composition exhibits a smectic A phase and contains at least two kinds of liquid crystal compounds, each of which has a smectic C phase alone. This is a liquid crystal element.

  According to the present invention, a large electrical gradient coefficient capable of generating a sufficient tilt can be obtained in a wide temperature range, and can be applied to a liquid crystal element capable of stable display at an ultrahigh speed.

It is explanatory drawing of (a) soft mode and (b) goldstone mode. It is a graph which shows the phase diagram of an example (Mixture A) of a liquid-crystal composition. It is a graph which shows an example of the phase diagram of other liquid crystal constituents (Mixture B). It is a graph which shows an example of the phase diagram of other liquid crystal constituents (Mixture C). It is a graph which shows an example of the critical softening phenomenon of the layer compression elastic modulus B in the vicinity of a SmA-SmC phase transition point. The schematic diagram explaining the density | concentration and temperature dependence of the layer compression elastic modulus of Mixture A is shown. The schematic diagram explaining the density | concentration and temperature dependence of the layer compression elastic modulus of Mixture C is shown. The schematic diagram explaining the concentration and temperature dependence of the electroclinic coefficient of Mixture A is shown. The schematic diagram explaining the concentration and temperature dependence of the electroclinic coefficient of Mixture C is shown.

Hereinafter, the present invention will be described based on preferred embodiments.
FIG. 2 shows an example of a phase diagram of the liquid crystal composition used in the present invention, and FIGS. 3 and 4 show examples of phase diagrams of other liquid crystal compositions. In these phase diagrams, the horizontal axis φ is the fraction of the mixture of the first liquid crystal compound shown at the left end and the second liquid crystal compound shown at the right end, and the temperature T is the vertical axis. . The left end represents the composition of 100% of the first liquid crystal compound, the right end represents the composition of 100% of the second liquid crystal compound, and the middle part of the horizontal axis represents the mixture of the first liquid crystal compound and the second liquid crystal compound. Represent.

In the Mixture A shown in FIG. 2 and the Mixture B shown in FIG. 3, the first liquid crystal compound and the second liquid crystal compound are respectively isotropic phase (Iso) -smectic A (SmA) phase-smectic C (SmC) from the high temperature side. ) Phase. Here, the SmA phase includes a chiral smectic A (SmA ^* ) phase, and the SmC phase includes a chiral smectic C (SmC ^* ) phase, an antiferroelectric smectic C (SmC _A ^* ) phase, and a ferrielectric property. Phases are to be included.

In the phase diagram of Mixture B in FIG. 3, the same liquid crystal phases (SmA and SmA, SmC and SmC, etc.) are mixed well, and in the mixed system of two types of liquid crystal compounds exhibiting the Iso-SmA-SmC phase transition, the phase transition A phase diagram is formed to continuously connect the temperature differences. In general, mixing two types of liquid crystal materials is known to be a good mixing principle in the case of the same liquid crystal phase. It is also used as a principle for identifying a liquid crystal phase by a mixing test called "." FIG. 3 corresponds to a case where the principle of the mixing test is well satisfied. In fact, practical nematic liquid crystals use a mixture of a plurality of liquid crystal materials in order to adjust the transition temperature, viscosity, and the like. Further, the SmC ^* phase is important as a liquid crystal material exhibiting ferroelectricity, and attempts have been made to improve material properties by mixing a plurality of SmC ^{* s} (in a broad sense, SmC).

  When the SmA-SmC phase transition temperatures of the two liquid crystal compounds are extremely different, or when the second liquid crystal compound does not show the SmC phase, the SmC phase is destabilized as in Mixture C shown in FIG. As the proportion of the first liquid crystal compound shown at the left end decreases, a certain concentration disappears to the limit. FIG. 4 corresponds to the case where the SmA-SmC phase transition temperature of the second liquid crystal compound shown at the right end is lower than the temperature range of the vertical axis, or the second liquid crystal compound does not show the SmC phase. .

On the other hand, although both types of liquid crystal compounds show SmC phase at similar temperatures, as shown in the phase diagram of Mixture A in FIG. 2, in the vicinity of a symmetrical composition (one-to-one concentration ratio), It is known that there exists a combination of compounds in which the SmC phase disappears and the SmA phase is stabilized, and this SmA phase is referred to as “Induced SmA phase”.
Here, when comparing the region where the first liquid crystal compound is rich, that is, the left end of the phase diagram between Mixture A and Mixture C, the SmC phase is almost the same in FIG. 2 and FIG. 4 by mixing the second liquid crystal compound. Becomes unstable and the SmA-SmC phase transition temperature decreases. The difference between the two is whether or not the second liquid crystal compound has an SmC phase at a similar temperature. Here, the present inventors decided to call the SmC phase which the 2nd liquid crystal compound in Mixture A shows "Hindered (hidden) SmC phase".

  The phase diagrams of Mixture A and Mixture C shown in FIGS. 2 and 4 have thermodynamically similar shapes in the region where the first liquid crystal compound is rich (the left end of the phase diagram). However, no features can be found in both the SmC phase and the SmA phase. Here, the representative inventor has previously studied the viscoelastic properties of the liquid crystal phase, and the elastic modulus related to compression / expansion between smectic layers called the layer compression elastic modulus is critical near the transition point of the SmA-SmC phase. It was found to cause softening (S. Shibahara, J. Yamamoto, Y. Takanishi, K. Ishikawa, H. Takezoe and H. Tanaka, Critical Behavior of Layer Compression Modulus near the Smectic-A-Smectic-Cα * Transition, Phys. Rev. Lett. 85, 1670-1673 (2000).). This phenomenon is a critical phenomenon originated from the divergent decrease in the force that restores the tilt of molecules in the layer, which is also the order parameter of the SmC phase on the low temperature side, near the SmA-SmC transition point, which is the second-order phase transition. It is. That is, by changing the molecular tilt with respect to the layer, it is possible to easily respond to the expansion and contraction of the layer (elasticity becomes weak).

  FIG. 5 shows an example of the critical softening phenomenon of the layer compression elastic modulus B in the vicinity of the SmA-SmC phase transition point reported in the past. FIG. 5 shows the temperature dependency of the layer compression modulus B. The layer compression modulus B gradually increases as the temperature decreases (in other words, the temperature increases). However, in the temperature range between the SmA-SmC phase transition temperature and a temperature several degrees higher than the SmA-SmC phase transition temperature, the temperature decreases on the contrary. Accordingly, the layer compressive elastic modulus B tends to decrease rapidly (in other words, the layer compressive elastic modulus B increases rapidly as the temperature rises). This is because in the SmA phase stable on the high temperature side, the long axis direction of the liquid crystal molecules is stable in the alignment perpendicular to the layer, whereas in the SmC phase stable on the low temperature side, the long axis direction of the liquid crystal molecules is inclined to the layer. Because the alignment is stabilized, the liquid crystal molecules can easily respond to the stretching deformation of the layer by changing the molecular tilt with respect to the layer at a temperature several degrees C. higher or lower than the SmA-SmC phase transition temperature. It represents that the elastic modulus B decreases. That is, even if the mixed system does not actually show the SmC phase, the critical phenomenon of the SmA-SmC phase transition can be observed in the SmA phase, and the critical temperature can be estimated. However, in the example of FIG. 5, the temperature range (critical temperature region) in which the layer compression elastic modulus B decreases near the SmA-SmC phase transition temperature is as narrow as about 5 to 10 ° C., and for industrial applications, It is necessary to expand the critical temperature region.

In the process of studying the critical phenomenon in the SmA-SmC phase transition using a method called viscoelasticity measurement, the present inventors have made a certain mixed system of two kinds of liquid crystal substances exhibiting the SmA-SmC phase transition. Then, we discovered an abnormal critical phenomenon where the critical temperature range expands to a wide temperature range. That is, Mixture A shown in the phase diagram of FIG. 2 shows an abnormal critical phenomenon, unlike the case of pure substance and Mixture C shown in the phase diagram of FIG.
FIG. 6 is a schematic diagram for explaining the concentration / temperature dependence of the layer compression elastic modulus of Mixture A, and FIG. 7 is a schematic diagram for explaining the concentration / temperature dependence of the layer compression elastic modulus of Mixture C. . 6 (a) and 7 (a) show the phase diagrams of FIGS. 2 and 4 on the T-φ plane of the coordinate system consisting of the three axes of the layer compression modulus B, temperature T, and concentration (composition) φ. The graph of the T temperature dependence of B in the three compositions φ ₀ to φ ₃ is superimposed on the phase diagram. Here, phi ₀ represents the case of the first liquid crystal compound alone, shown in the left end of FIG. 2 and FIG. 4, phi ₁ to [phi] ₃ is the first liquid crystal compound as a main compound, a second liquid crystal compound Is a sub-compound, and the fraction of the second liquid crystal compound increases in the order of φ ₀ to φ ₁ , φ ₂ , φ ₃ .

  As shown in FIG. 6B and FIG. 7B, when the temperature dependence of the layer compression modulus B is measured in the vicinity of the SmA-SmC phase transition temperature while gradually increasing the concentration of the sub-compound, It can be seen that the phase transition temperature (in these figures, B corresponds to the temperature at which B is minimal) decreases. In the case of Mixture C, as shown in FIG. 7B, a normal critical phenomenon is observed around the phase transition temperature depending on the concentration, whereas in Mixture A, FIG. As shown, it can be seen that as the concentration of the sub-compound increases, the temperature region (critical region) showing the critical phenomenon abnormally expands, and anomaly showing the critical phenomenon appears in a wide temperature range. In this case, the critical phenomenon is that the SmC phase exceeds the limit concentration that is retained in the thermodynamic phase diagram, and even if only the SmA phase appears on the phase diagram, softening should be observed in principle. It is.

The present inventors hypothesize about the physical mechanism that causes this abnormal critical phenomenon, but not only the main compound but also the sub compound alone is in the temperature range showing the SmC phase. The presence of a “Hindered (hidden) SmC phase”, which indicates the SmC phase if it is used alone, affects the SmA-SmC critical phenomenon through dynamics such as concentration fluctuations and transient SmC structure formation. I expect.
Further, even if the composition and temperature exhibit a SmA phase in the mixture, at that temperature, the main compound and the sub compound alone are within the range indicating the SmC phase or within the critical region range slightly higher than the SmA-SmC phase transition temperature. Is in. From this, even if the liquid crystal composition shows the SmA phase as a whole, each liquid crystal molecule is easily tilted like the SmC phase, and the molecular tilt is easy to change, as shown in FIG. Thus, it is also considered that the liquid crystal molecules 11 tend to increase / decrease the tilt angle with respect to the layer normal line 13 and cause a soft mode motion.

  Therefore, Mixture A in FIG. 2 shows that the liquid crystal composition exhibits an SmA phase in a specific temperature range, but two or more kinds of liquid crystal compounds contained in the liquid crystal composition each independently exhibit an SmC phase. When applied to a liquid crystal element using mode motion, an ultrafast response can be obtained in a wide temperature range. As a method for inducing a soft mode motion in the liquid crystal composition, a method utilizing an electroclinic effect may be mentioned. The electroclinic effect is an effect in which, in a system in which chiral symmetry is broken, the inclination of molecules in the layer is induced by spontaneous polarization being aligned in the electric field direction. Since the tilt related to the layer is the order variable itself in the SmC phase, the force to suppress the tilt of the molecule in the SmA phase corresponds to the variation itself of the free energy order variable describing the SmA-SmC phase transition. That is, the electroclinic coefficient is similar to the critical phenomenon of the layer compression modulus B, in the vicinity of the SmA-SmC phase transition point, which is the secondary phase transition, due to the divergent decrease in force that suppresses the occurrence of tilt. The coefficient χ increases divergently. As explained above, when applying the electroclinic effect industrially and trying to use an essentially ultrafast soft mode motion for the display element, this strong temperature dependence has been a disadvantage in the past. At a temperature far from the transition point, sufficient tilt does not occur unless a high voltage is applied.

  However, the abnormal critical phenomenon observed in the Induced SmA phase of Mixture A completely corresponds to the fact that the same phenomenon is observed by the electroclinic effect and has a uniform and large electroclinic coefficient over a wide temperature range. FIG. 8 is a schematic diagram for explaining the concentration / temperature dependency of the electric gradient coefficient of Mixture A, and FIG. 9 is a schematic diagram for explaining the concentration / temperature dependency of the electric gradient coefficient of Mixture C. As for Mixture C, as shown in FIG. 9, a similar electroclinic effect is observed when the transition temperature simply decreases as the secondary compound increases, but in Mixture A, as shown in FIG. A large electric gradient coefficient is observed in the range. In addition, the symbol which added ~ on χ which is the vertical axis | shaft of FIG.8 and FIG.9:

Represents an effective electroclinic coefficient including softening of the layer compression modulus B.
A smectic liquid crystal mixture that forms an induced SmA phase with a Hindered SmC phase has a mechanism that causes an anomalous electroclinic effect due to the expansion of the critical region of the SmA-SmC phase. By using such a liquid crystal mixture, a basic technique for producing an ultrafast liquid crystal display element using a soft mode can be obtained. For industrial applications, it is necessary to search for a liquid crystal mixture having a flatter temperature characteristic and generating a large tilt angle with a small electric field. Since it seems that various material designs are possible, it is highly likely that a mixed system showing effective physical properties can be obtained.

  Considering this abnormal critical phenomenon in relation to the electroclinic effect described above, in the liquid crystal exhibiting the SmA phase, the influence of the phase transition to the SmC phase is observed even at a temperature far from the SmA-SmC phase transition point. As a result, a large electroclinic coefficient is realized in a wide temperature range, and its physical properties can be applied to a display element. The mixed system exhibiting an abnormal critical phenomenon is that the SmA phase is strongly stabilized in the entire liquid crystal composition of the mixed system, even though at least two or more liquid crystal compounds exhibit the SmC phase. It is a mixed system showing a phase called “Induced SmA phase” in which no transition occurs. The existence of this mixed system itself has been recognized for more than ten years before the intensive study of ferroelectric liquid crystals. However, the induced SmA phase has been treated as a troublesome property that the SmC phase becomes unstable as a result of mixing to increase the realization temperature of the SmC phase. As will be described later, it is not possible to investigate whether or not anomalies are inherently found in critical phenomena from the phase diagram alone. This time, the study of viscoelasticity shows that the characteristics of the SmA-SmC phase transition of the mixed system depend not only on the temperature difference from the distance from the phase transition point, but also on other physical quantities such as concentration and microstructural characteristics. It was clearly shown that it changed. Therefore, the present inventors concluded that in the induced SmA phase, an abnormal critical phenomenon occurs due to the presence of the “Hindered SmC” phase of the destabilized mixture, and the critical temperature range is expanded. Therefore, by applying this abnormal critical phenomenon, it is possible to design a liquid crystal mixed material that provides a uniform and large electric gradient coefficient in a wide temperature range, and in a soft mode as shown in FIG. It can be applied to a liquid crystal element capable of high-speed response, such as a display element or an optical element.

Examples of the method for filling the liquid crystal material between the two substrates include a conventional vacuum injection method, a liquid crystal drop injection method (One Drop Fill), a flexographic printing method, and the like. After injecting the liquid crystal material after heating it to an isotropic phase or nematic phase (higher temperature and more stable phase), and then slowly cooling it when necessary, the phase transitions to a nematic or smectic phase (lower temperature and more stable phase) It is preferable to make it.
In order to drive the liquid crystal layer sandwiched between the first substrate and the second substrate, at least one of the first substrate and the second substrate has an electrode for controlling the liquid crystal layer.
When the layer normal of the smectic A phase indicated by the liquid crystal composition is substantially horizontal to the substrate, the electric field generated by the electrode is preferably substantially perpendicular to the substrate. In order to apply an electric field substantially perpendicular to the substrate, it is preferable to provide electrodes on each of the first substrate and the second substrate.
When the layer normal of the smectic A phase indicated by the liquid crystal composition is substantially perpendicular to the substrate, the electric field generated by the electrode controlling the liquid crystal layer is preferably substantially horizontal to the substrate. In order to apply the electric field substantially horizontally to the substrate, it is preferable to provide two electrodes having different polarities on the same substrate. The electrode may be a comb electrode.

  As a liquid crystal material, as a liquid crystal having an SmC phase and an SmA phase, conventionally known biphenyl, terphenyl, phenylcyclohexane, phenylbicyclohexane, biphenylylcyclohexane, benzoic acid phenyl ester, benzoic acid biphenyl ester, cyclohexanecarboxylic acid phenyl ester, Biphenylcarboxylic acid phenyl ester, cyclohexyl benzoic acid phenyl ester, cyclohexyl benzoic acid cyclohexyl ester, phenylpyrimidine, biphenylylpyrimidine, 2,5-diphenylpyrimidine, phenyldioxane, biphenylyldioxane, diphenylacetylene (also known as tolan), 1-phenyl- 2-cyclohexylethane, 1-phenyl-2-biphenylylethane, 1-cyclohexyl-2-biphenylylethane Cyanophenyl ester, cyanobiphenyl ester, alkylcyanobiphenyl, alkylcyanoterphenyl, azoxybenzene etc. are used as the skeleton to form the so-called core, alkyl group, alkoxy group, halogen atom (fluorine, chlorine, bromine, etc.), cyano And a liquid crystal compound which may have a substituent such as a group, an ether group, an ester group or an aryl group. As the liquid crystal material, either a positive or negative dielectric anisotropy can be used, and a liquid crystal compound having a positive dielectric anisotropy and a negative liquid crystal compound can be used in combination.

The liquid crystal material may be an achiral liquid crystal compound or a chiral liquid crystal compound. In order to obtain chiral liquid crystal phases (chiral nematic phase, chiral smectic A phase, chiral smectic C phase, etc.), chiral liquid crystal compounds can also be used, and non-liquid crystalline chiral compounds are added to achiral liquid crystal compounds. You can also. In order for a liquid crystal having a tilted smectic phase, particularly a smectic C phase, to exhibit a ferroelectric, antiferroelectric or ferrielectric liquid crystal, a non-racemic chiral system is preferred, and a chiral liquid crystal compound (liquid crystalline chiral Compound) or a non-liquid crystalline chiral compound. In order to introduce asymmetry into these chiral compounds, for example, a structure having a branched or substituted alkyl group, alkoxy group, alkenyl group, alkoxycarbonyl group, etc. in the side chain linked to one or both of the mesogen ends. And those containing an asymmetric atom, axial asymmetry, or plane asymmetry in the cyclic structure.
A chiral compound having an asymmetric carbon as an asymmetric atom is also preferably used, and a liquid crystal composition containing this chiral compound (which may be liquid crystalline or non-liquid crystalline) is preferably used. The position of the asymmetric carbon is preferably close to the core part, and it is particularly preferable that the asymmetric carbon is present between 1 and 4 counted by the linear number of atoms from the core part. Alternatively, it is also preferable that asymmetric carbon exists on both sides of the core part. Also in this case, it is particularly preferable to be located near the core. As the structure of the asymmetric carbon, those in which the substituent on the asymmetric carbon contains fluorine, a methyl group, or a trifluoromethyl group are particularly preferably used.

  It is preferable that the liquid crystal composition contains a liquid crystal having at least one kind of phenylpyrimidine skeleton in the core part and a liquid crystal having at least one kind of ester bond in the core part. Examples of the liquid crystal having an ester bond in the core part include benzoic acid phenyl ester, benzoic acid biphenyl ester, cyclohexane carboxylic acid phenyl ester, biphenyl carboxylic acid phenyl ester, cyclohexyl benzoic acid phenyl ester, and cyclohexyl benzoic acid cyclohexyl ester. . These skeletons can also be substituted with halogen atoms (fluorine, chlorine, bromine, etc.).

It is also preferable that the liquid crystal composition contains a liquid crystal forming at least one monolayer and a liquid crystal forming at least one bilayer.
As the liquid crystal compound forming the monolayer, the side chains at both ends of the liquid crystal compound are each an alkyl group having 1 to 18 carbon atoms (one or more —CH ₂ — group contained in the alkyl group is —O— , -CO-, -COO-, -OCOO-, -CH = CH-, -C≡C-), alkoxyl group, alkenyl group, alkylcarbonyloxy group, alkoxycarbonyl group, F atom , Cl atom, Br atom, CN group, CF ₃ group, OCF ₃ group and the like.
As the liquid crystal compound forming the bilayer, one of the side chains at both ends of the liquid crystal compound is an alkyl group, alkoxyl group, alkenyl group, alkylcarbonyloxy group, alkoxycarbonyl group, F atom, Cl atom, Br atom, CN group. , CF ₃ group, OCF ₃ group, etc., and the other of the side chains at both ends of the molecule is an alkyl group having 10 to 30 carbon atoms (one or two or more —CH ₂ contained in the alkyl group). -Groups may each be substituted with any of -O-, -CO-, -COO-, -OCOO-, -CH = CH-, -C≡C- provided that the oxygen atoms are mutually Except when directly bonded.) It is preferable that 8 or more, more preferably 10 or more of the hydrogen atoms are groups substituted by fluorine atoms, in which case 1 or 2 or more fluorine atoms In the alkyl group substituted with the fluorine atom, the carbon atom substituted with is preferably 4 or more, more preferably 5 or more consecutive [-(CH2 _{- pFp} ) _n It is preferable that p is 1 or 2, and n ≧ 4. The alkyl group substituted with the fluorine atom is, as its partial structure, a perfluoroalkyl group or a perfluoroalkylene group [— (CF ₂ ) _n F or — (CF ₂ ) _n — having 4 or more carbon atoms] n ≧ 4] is preferable.
When the liquid crystal composition contains a liquid crystal that forms a monolayer and a liquid crystal that forms a bilayer, the liquid crystal that forms the monolayer is the main compound, or the liquid crystal that forms the bilayer is the main compound. You can also.

<Liquid crystal compound>
As a liquid crystalline compound showing a smectic C phase, the following general formula

(In the formula, each R independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, a hydrogen atom or a fluorine atom, and one or two of the alkyl groups are not adjacent to each other; The CH ₂ — group is —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—S—, —S—CO—, —O—SO ₂ —, —SO. ₂ -O—, —O—CO—O—, —CH═CH—, —C≡C—, a cyclopropylene group, or —Si (CH ₃ ) ₂ — may be substituted. One or more hydrogen atoms may be replaced by fluorine, chlorine, bromine or CN groups;
Z is each independently —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N (R ^a ) —, —N ( R ^a ) —CO—, —OCH ₂ —, —CH ₂ O—, —SCH ₂ —, —CH ₂ S—, —O—SO ₂ —, —SO ₂ —O—, —CF ₂ O—, — _{OCF 2 -, - CF 2 S} -, - SCF 2 -, - CH 2 CH 2 -, - CF 2 CH 2 -, - CH 2 CF 2 -, - CF 2 CF 2 -, - CH = CH -, - CF═CH—, —CH═CF—, —CF═CF—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH— or a single bond, R ^{a in} —N (R ^a ) — or —N (R ^a ) —CO— represents ^a hydrogen atom or ^a linear or branched alkyl group having 1 to 4 carbon atoms,
A each independently represents a phenylene group, a cyclohexylene group, a dioxolanediyl group, a cyclohexenylene group, a bicyclo [2.2.2] octylene group, a piperidinediyl group, a naphthalenediyl group, a decahydronaphthalenediyl group, or a tetrahydronaphthalenediyl group. Or a cyclic group selected from indanediyl group, wherein the phenylene group, naphthalenediyl group, tetrahydronaphthalenediyl group, or indanediyl group is replaced by a nitrogen atom in one or more —CH═ groups in the ring The cyclohexylene group, dioxolanediyl group, cyclohexenylene group, bicyclo [2.2.2] octylene group, piperidinediyl group, decahydronaphthalenediyl group, tetrahydronaphthalenediyl group, or indanediyl group is a ring. One or two of Not in contact with -CH 2 _- groups may be replaced by -O- and / or -S-, 1 or more hydrogen atoms of the cyclic group, a fluorine atom, a chlorine atom, a bromine atom, CN group, NO ₂ group, or an alkyl group, alkoxy group, alkylcarbonyl group or alkoxy having 1 to 7 carbon atoms in which one or more hydrogen atoms may be replaced by a fluorine atom or a chlorine atom May be replaced by a carbonyl group,
n is 1, 2, 3, 4 or 5. The liquid crystalline compound (LC-0) represented by

  In addition, the following general formula

(In the formula, each R independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, a hydrogen atom or a fluorine atom, and one or two of the alkyl groups are not adjacent to each other; The CH ₂ — group is —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—S—, —S—CO—, —O—SO ₂ —, —SO. ₂ -O—, —O—CO—O—, —CH═CH—, —C≡C—, a cyclopropylene group, or —Si (CH ₃ ) ₂ — may be substituted. One or more hydrogen atoms may be replaced by fluorine, chlorine, bromine or CN groups;
Z is each independently —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N (R ^a ) —, —N ( R ^a ) —CO—, —OCH ₂ —, —CH ₂ O—, —SCH ₂ —, —CH ₂ S—, —O—SO ₂ —, —SO ₂ —O—, —CF ₂ O—, — _{OCF 2 -, - CF 2 S} -, - SCF 2 -, - CH 2 CH 2 -, - CF 2 CH 2 -, - CH 2 CF 2 -, - CF 2 CF 2 -, - CH = CH -, - CF═CH—, —CH═CF—, —CF═CF—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH— or a single bond, R ^{a in} —N (R ^a ) — or —N (R ^a ) —CO— represents ^a hydrogen atom or ^a linear or branched alkyl group having 1 to 4 carbon atoms,
Each Y independently represents a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms, and one or two or more methylene groups present in the alkylene group have oxygen atoms bonded to each other. Each of them may be independently substituted with -O-, -CO-, -COO- or -OCO- as not directly bonded, and one or more hydrogen atoms present in the alkylene group are each independently May be substituted with a halogen atom or an alkyl group having 1 to 9 carbon atoms,
Each X independently represents a halogen atom, a cyano group, a methyl group, a methoxy group, —CF ₃ , or —OCF ₃ ;
n independently represents an integer of 0 to 4;
n ₁ , n ₂ , n ₃ and n ₄ each independently represents 0 or 1, but n ₁ + n ₂ + n ₃ + n ₄ = 1 to 4,
Cyclo independently represents a cycloalkane having 3 to 10 carbon atoms, and may optionally have a double bond. The liquid crystal compounds (LC-I) to (LC-III) represented by

  Here, Cyclo is preferably cyclohexane (cyclohexylene group), for example, the following general formula:

(In the formula, each R independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, a hydrogen atom or a fluorine atom, and one or two of the alkyl groups are not adjacent to each other; The CH ₂ — group is —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—S—, —S—CO—, —O—SO ₂ —, —SO. ₂ -O—, —O—CO—O—, —CH═CH—, —C≡C—, a cyclopropylene group, or —Si (CH ₃ ) ₂ — may be substituted. One or more hydrogen atoms may be replaced by fluorine, chlorine, bromine or CN groups;
Z is each independently —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N (R ^a ) —, —N ( R ^a ) —CO—, —OCH ₂ —, —CH ₂ O—, —SCH ₂ —, —CH ₂ S—, —O—SO ₂ —, —SO ₂ —O—, —CF ₂ O—, — _{OCF 2 -, - CF 2 S} -, - SCF 2 -, - CH 2 CH 2 -, - CF 2 CH 2 -, - CH 2 CF 2 -, - CF 2 CF 2 -, - CH = CH -, - CF═CH—, —CH═CF—, —CF═CF—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH— or a single bond, R ^{a in} —N (R ^a ) — or —N (R ^a ) —CO— represents ^a hydrogen atom or ^a linear or branched alkyl group having 1 to 4 carbon atoms,
Each Y independently represents a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms, and one or two or more methylene groups present in the alkylene group have oxygen atoms bonded to each other. Each of them may be independently substituted with -O-, -CO-, -COO- or -OCO- as not directly bonded, and one or more hydrogen atoms present in the alkylene group are each independently May be substituted with a halogen atom or an alkyl group having 1 to 9 carbon atoms,
Each X independently represents a fluorine atom, a chlorine atom, a bromine atom, a cyano group, a methyl group, a methoxy group, a CF ₃ group, or an OCF ₃ group;
n independently represents an integer of 0 to 4;
n ₁ , n ₂ , n _3, and n ₄ each independently represent 0 or 1, but n ₁ + n ₂ + n ₃ + n ₄ = 1 to 4. The liquid crystal compounds (LC-I ′) to (LC-III ′) represented by

In order to exhibit liquid crystallinity, the ring is preferably 1,4-substituted. That is, the cyclic divalent group contained in the liquid crystalline compound is preferably a 1,4-cyclohexylene group, a 1,4-phenylene group, a 2,5-pyrimidinediyl group, or the like.
For example, the following general formula

(In the formula, each of R ¹¹ and R ¹² independently represents a linear or branched alkyl group having 1 to 18 carbon atoms or a fluorine atom, but R ¹¹ and R ¹² may be simultaneously a fluorine atom. In the alkyl group, one or two non-adjacent —CH ₂ — groups are —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—. S—, —S—CO—, —O—CO—O—, —CH═CH—, —C≡C—, a cyclopropylene group or —Si (CH ₃ ) ₂ — may be substituted. One or more hydrogen atoms in the group may be replaced by fluorine atoms or CN groups;
X ^{11 to} X ²² each independently represent a hydrogen atom, a fluorine atom, a CF ₃ group, or an OCF ₃ group,
L ^{11 to} L ¹⁴ are each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—O. -, - O-CO -, - CO-S -, - S-CO -, - O-CO-O -, - CH 2 CH 2 -, - CH = CH-, or -C≡C- represent,
Each Y independently represents a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms, and one or two or more methylene groups present in the alkylene group have oxygen atoms bonded to each other. Each of them may be independently substituted with -O-, -CO-, -COO- or -OCO- as not directly bonded, and one or more hydrogen atoms present in the alkylene group are each independently May be substituted with a halogen atom or an alkyl group having 1 to 9 carbon atoms,
a ¹ , b ¹ , c ¹ , and d ¹ each independently represent an integer of 0 or 1, but a ¹ + b ¹ + c ¹ + d ¹ is 1, 2 or 3, and d ¹ when a ¹ is 0 Is 0, c ¹ is 0 when a ¹ is 1, a ¹ is 0 when c ¹ is 1, and a ¹ = d ¹ = 0 when b ¹ = c ¹ = 1 And
Cyclo independently represents a cycloalkane having 3 to 10 carbon atoms, and may optionally have a double bond. The liquid crystalline compounds (LC-Ia) to (LC-IIIa) represented by
In addition, the following general formula

(In the formula, each of R ¹¹ and R ¹² independently represents a linear or branched alkyl group having 1 to 18 carbon atoms or a fluorine atom, but R ¹¹ and R ¹² may be simultaneously a fluorine atom. In the alkyl group, one or two non-adjacent —CH ₂ — groups are —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—. S—, —S—CO—, —O—CO—O—, —CH═CH—, —C≡C—, a cyclopropylene group or —Si (CH ₃ ) ₂ — may be substituted. One or more hydrogen atoms in the group may be replaced by fluorine atoms or CN groups;
Ring A ¹ is a 1,4-phenylene group in which 1 to 4 hydrogen atoms are each replaced by a fluorine atom, a CF ₃ group, an OCF ₃ group, or a CN group, or a plurality of these groups, or 1, Represents a 4-cyclohexylene group,
Ring B ¹ represents a 1,4-phenylene group in which ¹ to 4 hydrogen atoms may be replaced by a fluorine atom, a CF ₃ group, an OCF ₃ group, or a CN group, or a plurality of these groups,
Ring C ¹ represents a 1,4-cyclohexylene group in which ¹ to 4 hydrogen atoms may be replaced by a fluorine atom, a CF ₃ group, an OCF ₃ group, or a CN group, or a plurality of these groups,
L is each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—O—, —O. -CO -, - CO-S - , - S-CO -, - O-CO-O -, - CH 2 CH 2 -, - CH = CH-, or -C≡C- represent,
Each Y independently represents a single bond or a linear or branched alkylene group having 1 to 10 carbon atoms, and one or two or more methylene groups present in the alkylene group have oxygen atoms bonded to each other. Each of them may be independently substituted with -O-, -CO-, -COO- or -OCO- as not directly bonded, and one or more hydrogen atoms present in the alkylene group are each independently May be substituted with a halogen atom or an alkyl group having 1 to 9 carbon atoms,
a ¹ represents 0, 1 or 2, b ¹ and c ¹ represent an integer of 0, 1 or 2, and the sum of a ¹ , b ¹ and c ¹ represents ¹ , 2 or 3. Liquid crystal compound (LC-IV) represented by

(In the formula, each of R ²¹ and R ²² independently represents a linear or branched alkyl group having 1 to 18 carbon atoms or a fluorine atom, but R ²¹ and R ²² may be simultaneously a fluorine atom. In the alkyl group, one or two non-adjacent —CH ₂ — groups are —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—. S—, —S—CO—, —O—CO—O—, —CH═CH—, —C≡C—, a cyclopropylene group or —Si (CH ₃ ) ₂ — may be substituted. One or more hydrogen atoms in the group may be replaced by fluorine atoms or CN groups;
X ^{21 to} X ²⁷ each independently represent a hydrogen atom, a fluorine atom, a CF ₃ group, or an OCF ₃ group,
L ^{21 to} L ²⁴ are each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—O. -, - O-CO -, - CO-S -, - S-CO -, - O-CO-O -, - CH 2 CH 2 -, - CH = CH-, or -C≡C- represent,
a ² , b ² , c ² and d ² each independently represent an integer of 0 or 1, but a ² + b ² + c ² + d ² is 1, 2 or 3, and when a ² is 0, d ² Is 0, c ² is 0 when a ² is 1, and a ² = d ² = 0 when b ² = c ² = 1. The liquid crystalline compound (LC-V) represented by

Among phenylpyrimidine compounds, a substituent is added to the ring portion of the molecule to obtain a tilted smectic phase necessary for the development of ferroelectricity, to increase the tilt angle of the molecule, or to lower the melting point. It is preferable that at least one fluorine atom, CF ₃ group, or OCF ₃ group is introduced. It is preferable to introduce fluorine having a small shape as a substituent in terms of maintaining a stable liquid crystal phase and maintaining high-speed response. The number of substituents is preferably 1 to 3.
The viscosity is fast response low, the linking group connecting the ring (-Z-Y-Z-, or -Y-L-Y-) as a single _{bond, -CH 2 O -, - OCH} 2 -, - CF It is preferably selected from ₂ O—, —OCF ₂ —, —CH ₂ CH ₂ —, —CH═CH—, or —C≡C—, and more preferably a single bond. A single bond is preferable also in terms of suppressing local polarization of the molecule and reducing adverse effects on the switching behavior. On the other hand, as the material for maintaining the stability of the layer structure, it is preferable that the viscosity is high. In this case, from —CO—O—, —O—CO—, —CO—S—, and —S—CO—. It is preferably selected from the above, and in particular, —CO—O— and —O—CO— are preferably used.
On the other hand, in terms of increasing the effect of lowering the melting point, one or both of the side chains (R, R ¹¹ , R ¹² , R ²¹ , R ²² ) have a hydrogen atom, methyl group, ethyl group, propyl group, pentyl group. Hexyl group, heptyl group, octyl group, nonyl group, isopropyl group, alkylcarbonyloxy group, alkyloxycarbonyl group, and alkyloxycarbonyloxy group are preferably used.

  As a compound suitable for increasing Δn, showing a stable ferroelectric liquid crystal phase, and having a low viscosity and suitable for a high-speed response, the following general formula is used.

(Wherein R ²¹ and R ²² each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, a hydrogen atom, or a fluorine atom,
In the alkyl group, one or two non-adjacent —CH ₂ — groups are —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—S—. , —S—CO—, —O—SO ₂ —, —SO ₂ —O—, —O—CO—O—, —CH═CH—, —C≡C—, a cyclopropylene group or —Si (CH _{3 2} )-may be replaced with one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom, a chlorine atom, a bromine atom, or a CN group,
X ^{21 to} X ²⁴ each independently represent a hydrogen atom, a halogen, a cyano group, a methyl group, a methoxy group, a CF ₃ group, or an OCF ₃ group,
Ring A ¹ represents a phenylene group or a cyclohexylene group,
L is each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—O—, —O. -CO -, - CO-S - , - S-CO -, - O-CO-O -, - CH 2 CH 2 -, - CH = CH-, or -C≡C- represent,
a ¹ represents 0, 1, or 2, b ¹ and c ¹ represent an integer of 0, 1, or 2, the sum of a ¹ + b ¹ + c ¹ represents 1 or 2, and a ¹ = 1 The liquid crystal compound (LC-VI) represented by the formula (when c ¹ = 0 and when c ¹ = 1 is a ¹ = 0) is preferable.

Y in the general formulas (LC-I) to (LC-VI) is preferably each independently a single bond or an alkylene group having 1 to 7 carbon atoms (one or two present in the alkylene group). The above methylene groups may be independently substituted with —O—, —CO—, —COO— or —OCO— as oxygen atoms are not directly bonded to each other.
More preferably, each independently, a single bond or an alkylene group having 1 to 5 carbon atoms (one or two or more methylene groups present in the alkylene group are independent as those in which oxygen atoms are not directly bonded to each other). May be substituted with -O-, -CO-, -COO- or -OCO-.
More preferably, each independently, a single bond or an alkylene group having 1 to 3 carbon atoms (one or two or more methylene groups present in the alkylene group are independent as those in which oxygen atoms are not directly bonded to each other). -O-, -CO-, -COO- or -OCO- may be substituted.

  As a compound suitable for TFT driving, showing a stable ferroelectric liquid crystal phase and having a low viscosity and suitable for a high-speed response, the following general formula

(Wherein e ¹ represents 0 or 1,
X ^{21 to} X ²⁶ each independently represents a hydrogen atom or a fluorine atom group. When e ¹ is 0, at least one of X ^{21 to} X ²⁴ is a fluorine atom, and when e ¹ is 1, X ^{21 to} X ^{26 At} least one of ²⁶ is a fluorine atom;
R ²¹ and R ²² each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, and one —CH ₂ — group in the alkyl group may be replaced by —O—. Often,
L ²⁵ represents a single bond, —CH ₂ O—, or —OCH ₂ —.
Ring A ¹ represents a phenylene group or a cyclohexylene group. The liquid crystalline compound (LC-VII) represented by

  The liquid crystal compounds used in the liquid crystal composition are the above (LC-0), (LC-I) to (LC-III), (LC-IV), (LC-V), (LC-VI), ( LC-VII) or any combination of two or more thereof may be used.

<Chiral compound>
The chiral compound contained in the liquid crystal composition used in the present invention may be any of a compound having an asymmetric atom, a compound having axial asymmetry, a compound having plane asymmetry, and an atropisomer, and the chiral compound is polymerized. Those having a polymerizable group or those having no polymerizable group may be used.
In a compound having an asymmetric atom, it is preferable that the asymmetric atom is an asymmetric carbon atom because steric inversion hardly occurs, but a hetero atom may be an asymmetric atom. The asymmetric atom may be introduced into a part of the chain structure or may be introduced into a part of the cyclic structure.

  The liquid crystal composition has a general formula (IV) as a compound having an asymmetric atom.

(In formula (IV), R ¹ and R ² each independently represents a linear or branched alkyl group having 1 to 30 carbon atoms, a hydrogen atom or a fluorine atom, and one or two of the alkyl groups When two or more non-adjacent —CH ₂ — groups are —O—, —S—, —NH—, —N (CH ₃ ) —, —CO—, —CO—O—, —O—CO—, — O—CO—O—, —S—CO—, —CO—S—, —O—SO ₂ —, —SO ₂ —O—, —CH═CH—, —C≡C—, cyclopropylene group or — Si (CH ₃ ) ₂ — may be substituted, and one or more hydrogen atoms of the alkyl group may be replaced by a fluorine atom, a chlorine atom, a bromine atom or a CN group, The alkyl group may include a condensed or spirocyclic system, and the alkyl group may be It may contain one or more aromatic or aliphatic rings that may contain one or more heteroatoms, and these rings are optionally substituted with alkyl groups, alkoxy groups, halogens You may,
Either one or both of R ¹ and R ² is a group having an asymmetric atom,
Z is each independently —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N (R ^a ) —, —N ( R ^a ) —CO—, —OCH ₂ —, —CH ₂ O—, —SCH ₂ —, —CH ₂ S—, —CF ₂ O—, —OCF ₂ —, —CF ₂ S—, —SCF ₂ — _{, -CH 2 CH 2 -, -} CF 2 CH 2 -, - CH 2 CF 2 -, - CF 2 CF 2 -, - CH = CH -, - CF = CH -, - CH = CF -, - CF = CF—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH— or a single bond, —CO—N (R ^a ) — or —N (R ^a ) R ^{a in} —CO— represents ^a hydrogen atom or ^a linear or branched alkyl group having 1 to 4 carbon atoms,
A ¹ and A ² are each independently a phenylene group, cyclohexylene group, dioxolanediyl group, cyclohexenylene group, bicyclo [2.2.2] octylene group, piperidinediyl group, naphthalenediyl group, decahydronaphthalenediyl group, Represents a cyclic group selected from a tetrahydronaphthalenediyl group or an indanediyl group, wherein the phenylene group, naphthalenediyl group, tetrahydronaphthalenediyl group, or indanediyl group has one or more —CH═ groups in the ring. May be replaced by a nitrogen atom, the cyclohexylene group, dioxolanediyl group, cyclohexenylene group, bicyclo [2.2.2] octylene group, piperidinediyl group, decahydronaphthalenediyl group, tetrahydronaphthalenediyl group, or Indandiyl group is 1 in the ring Or two non-adjacent -CH 2 _- groups may be replaced by -O- and / or -S-, 1 or more hydrogen atoms of the cyclic group, a fluorine atom, a chlorine atom , A bromine atom, a CN group, a NO ₂ group, or an alkyl group having 1 to 7 carbon atoms, an alkoxy group, an alkyl, in which one or more hydrogen atoms may be replaced by a fluorine atom or a chlorine atom May be replaced by a carbonyl group or an alkoxycarbonyl group,
m is 1, 2, 3, 4 or 5. ) Is preferred.

A dichiral compound in which both R ¹ and R ² in the general formula (IV) are chiral groups is more preferable. Specific examples of the dichiral compound include compounds represented by the following general formulas (IV-a1) to (IV-a11).

In the general formulas (IV-a1) to (IV-a11), each R ³ independently represents a linear or branched alkyl group having 1 to 10 carbon atoms, and one or two of the alkyl groups When two or more non-adjacent —CH ₂ — groups are —O—, —S—, —NH—, —N (CH ₃ ) —, —CO—, —CO—O—, —O—CO—, — O—CO—O—, —S—CO—, —CO—S—, —O—SO ₂ —, —SO ₂ —O—, —CH═CH—, —C≡C—, cyclopropylene group or — Si (CH ₃ ) ₂ — may be substituted, and one or more hydrogen atoms of the alkyl group may be replaced by a fluorine atom, a chlorine atom, a bromine atom or a CN group, May be. Examples of the polymerizable group include a vinyl group, an allyl group, and a (meth) acryloyl group.
X ³ and X ⁴ are each a halogen atom (F, Cl, Br, I), a cyano group, a phenyl group (one or more arbitrary hydrogen atoms of the phenyl group are halogen atoms (F, Cl, Br, I), optionally substituted with a methyl group, a methoxy group, —CF ₃ , —OCF ₃ ), a methyl group, a methoxy group, —CF ₃ , or —OCF ₃ . However, in general formulas (IV-a3) and (IV-a8), in order for the position marked with * to be an asymmetric atom, a group different from X ³ is selected for X ⁴ .
Moreover, _{n 3} is an integer of 0 to 20.
R ⁵ in the general formulas (IV-a4) and (IV-a9) is preferably a hydrogen atom or a methyl group.
Examples of Q in the general formulas (IV-a5) and (IV-a10) include divalent hydrocarbon groups such as a methylene group, an isopropylidene group, and a cyclohexylidene group.
K in general formula (IV-a11) is an integer of 0-5.

More preferable examples include linear or branched alkyl groups having 4 to 8 carbon atoms such as R ³ = C ₄ H ₉ , C ₆ H ₁₃ , C ₈ H ₁₇ and the like. X ³ is preferably CH ₃ .

The partial structural formulas in the general formulas (IV) and (IV-a1) to (IV-a11), -A ^1- (ZA ² ) _m -are more preferably the following general formula (IV-b)

(In the formula, rings A, B and C are each independently a phenylene group, a cyclohexylene group or a naphthalenediyl group, and in these groups, any one or two or more arbitrary hydrogen atoms of the benzene ring are halogen atoms. An atom (F, Cl, Br, I), a methyl group, a methoxy group, —CF ₃ , —OCF ₃ , and any one or more carbon atoms of the benzene ring may be a nitrogen atom The definition of Z is the same as in formula (IV).), More preferably, the following general formulas (IV-b1) to (IV-b6)

(However, in these formulas (IV-b1) to (IV-b6), any one or two or more arbitrary hydrogen atoms of the benzene ring are halogen atoms (F, Cl, Br, I), methyl groups, A methoxy group, —CF ₃ , —OCF ₃ may be substituted, and any one or more carbon atoms of the benzene ring may be substituted with a nitrogen atom. The same as in IV)). In terms of reliability, a benzene ring or a cyclohexane ring is preferable to a heterocyclic ring such as a pyridine ring or a pyrimidine ring. In terms of increasing the dielectric anisotropy, it is preferable to use a compound having a heterocyclic ring such as a pyridine ring or a pyrimidine ring. In this case, the polarizability of the compound is relatively large, such as a benzene ring or a cyclohexane ring. In the case of a hydrocarbon ring such as a compound, the polarizability of the compound is low. For this reason, it is preferable to select an appropriate content according to the polarizability of the chiral compound.

Moreover, as a chiral compound used for a liquid-crystal composition, the compound or atropisomer which has axial asymmetry can also be used.
Axis asymmetry is an allene derivative shown below,

  The biphenyl derivatives shown below,

In a compound in which rotation of the bond axis is prevented, the substituents X ^a and Y ^a are different from each other on one end side of the axis, and the substituents X ^b and Y ^b are different from each other on the other end side of the axis. A case where rotation of the bond axis is hindered by the influence of steric hindrance such as a biphenyl derivative is called atropisomerism.

  Examples of compounds having axial asymmetry used for chiral compounds include:

Is mentioned. In formulas (IV-c1) and (IV-c2), at least one of X ⁶¹ and Y ⁶¹ , X ⁶² and Y ⁶² is present, and X ⁶¹ , X ⁶² , Y ⁶¹ and Y ⁶² are Each independently represents CH ₂ , C═O, O, N, S, P, B, or Si. In the case of N, P, B, and Si, they may be bonded to a substituent such as an alkyl group, an alkoxy group, or an acyl group so as to satisfy a required valence.
E ⁶¹ and E ⁶² are each independently a hydrogen atom, alkyl group, aryl group, allyl group, benzyl group, alkenyl group, alkynyl group, alkyl ether group, alkyl ester group, alkyl ketone group, heterocyclic group or these Represents any of the derivatives.

In Formula (IV-c1), R ⁶¹ and R ⁶² each independently represent an alkyl group, an alkoxyl group, or a phenyl group, a cyclopentyl group, or a cyclohexyl group that may be substituted with a halogen atom,
R ⁶³ , R ⁶⁴ , R ⁶⁵ , R ⁶⁶ , R ⁶⁷ and R ⁶⁸ each independently represent a hydrogen atom, an alkyl group, an alkoxyl group, an acyloxy group, a halogen atom, a haloalkyl group, or a dialkylamino group,
Two of R ⁶³ , R ⁶⁴ and R ⁶⁵ may form a mono- or polymethylenedioxy group which may have a methylene chain or a substituent which may have a substituent. ,
Two of R ⁶⁶ , R ⁶⁷ and R ⁶⁸ may form a mono- or polymethylenedioxy group which may have a methylene chain or a substituent which may have a substituent. .
However, it excludes when both ^R65 and ^R66 are hydrogen atoms.

In addition, as the chiral compound used in the liquid crystal composition, a compound having surface asymmetry can also be used.
Examples of compounds having surface asymmetry include the following helicene derivatives:

(In the formula (IV-c3), at least one of X ⁶¹ and Y ⁶¹ , X ⁶² and Y ⁶² exists, and X ⁶¹ , X ⁶² , Y ⁶¹ , and Y ⁶² are each independently CH _2. , C = O, O, N, S, P, B, or Si, and in the case of N, P, B, or Si, an alkyl group, an alkoxy group, or an alkoxy group so as to satisfy a required valence. It may be bonded to a substituent such as a group or an acyl group.
E ⁶¹ and E ⁶² are each independently a hydrogen atom, alkyl group, aryl group, allyl group, benzyl group, alkenyl group, alkynyl group, alkyl ether group, alkyl ester group, alkyl ketone group, heterocyclic group or these Represents any of the derivatives. )

Is mentioned. In such a helicene derivative, the front-rear relationship of the overlapping rings cannot be freely converted, so the case where the ring takes a right-handed spiral structure is distinguished from the case where it takes a left-handed helical structure, and the chirality is To express.

  The chiral compound contained in the liquid crystal composition is preferably a compound having a large helical twisting power so that the pitch of the helical structure is reduced. In particular, when adjusting DHFLC having a short helical pitch of 400 nm or less, it is preferable to use a compound having a large torsional force. Since a compound having a large twisting force can be added in a small amount to obtain a desired pitch, a chiral compound having a high raw material cost can be minimized, which is preferable from the viewpoint of cost reduction. From this viewpoint, compounds represented by the general formulas (IV-d1) to (IV-d3), which are compounds having an asymmetric atom, as preferred chiral compounds

And compounds represented by general formulas (IV-d4) to (IV-d5), which are compounds having axial asymmetry

Is mentioned. In formulas (IV-d1) to (IV-d5), R ⁷¹ and R ⁷² are each independently hydrogen, halogen, cyano (CN) group, isocyanate (NCO) group, isothiocyanate (NCS) group or carbon An alkyl group having a number of 1 to 20 is represented, and one or more of —CH ₂ — in the alkyl group is —O—, —S—, —COO—, —OCO—, —CH═. CH—, —CF═CF—, or —C≡C— may be replaced, and any hydrogen in the alkyl may be replaced with a halogen,
A ⁷¹ and A ⁷² each independently represents an aromatic or non-aromatic 3- to 8-membered ring or a condensed ring having 9 or more carbon atoms, and any hydrogen in these rings is halogen, carbon It may be substituted with an alkyl group having 1 to 3 atoms or a haloalkyl group, and one or more of —CH ₂ — in the ring may be replaced with —O—, —S—, or —NH—. , One or more of the rings —CH═ may be replaced by —N═,
Z ⁷¹ and Z ⁷² each independently represent a single bond or an alkylene group having 1 to 8 carbon atoms, and arbitrary —CH ₂ — represents —O—, —S—, —COO—, —OCO—, -CSO-, -OCS-, -N = N-, -CH = N-, -N = CH-, -N (O) = N-, -N = N (O)-, -CH = CH-, -CF = CF-, or -C≡C-, and any hydrogen may be replaced with a halogen;
X ⁷¹ and X ⁷² each independently represent a single bond, —COO—, —OCO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, or —CH ₂ CH ₂ —. Represent,
_m71 and _m72 each independently represent an integer of 1 to 4. However, either one of m ₇₁ and m ₇₂ in Formula (IV-d5) may be 0.
In the formula (IV-d2), Ar ⁷¹ and Ar ⁷² each independently represent a phenyl group or a naphthyl group, and in these groups, any one or two or more arbitrary hydrogen atoms of the benzene ring are halogen atoms (F , Cl, Br, I), a methyl group, a methoxy group, —CF ₃ , —OCF ₃ may be substituted.

  As the chiral compound, a chiral compound having a mesogen can also be used. As such a chiral compound, for example,

Is mentioned. In formulas (IV-e1) to (IV-e3),
R ⁸¹ , R ⁸² , R ⁸³ and Y ⁸¹ each independently represent a linear or branched alkyl group having 1 to 30 carbon atoms, a hydrogen atom or a fluorine atom, and one or two of the alkyl groups When two or more non-adjacent —CH ₂ — groups are —O—, —S—, —NH—, —N (CH ₃ ) —, —CO—, —CO—O—, —O—CO—, — O—CO—O—, —S—CO—, —CO—S—, —O—SO ₂ —, —SO ₂ —O—, —CH═CH—, —C≡C—, cyclopropylene group or — Si (CH ₃ ) ₂ — may be substituted, and one or more hydrogen atoms of the alkyl group may be replaced by a fluorine atom, a chlorine atom, a bromine atom or a CN group, The alkyl group may contain a condensed or spirocyclic system, and the alkyl group The group may contain one or more aromatic or aliphatic rings which may contain one or more heteroatoms, and these rings may be alkyl groups, alkoxy groups, halogens. Optionally substituted,
Z ⁸¹ , Z ⁸² , Z ⁸³ , Z ⁸⁴ and Z ⁸⁵ each independently represent an alkylene group having 1 to 40 carbon atoms, and one or more CH ₂ groups of the alkyl group are —O _{-, - S -, - NH} -, - N (CH 3) -, - CO -, - COO -, - OCO -, - OCOO -, - S-CO -, - CO-S -, - CH = CH -, - CH = CF -, - CF = CH -, - CF = CF -, - CF 2 - or -C≡C- may be replaced by,
X ⁸¹ , X ⁸² and X ⁸³ are each independently —O—, —S—, —CO—, —COO—, —OCO—, —OCOO—, —CO—NH—, —NH—CO—, — CH ₂ CH ₂ —, —OCH ₂ —, —CH ₂ O—, —SCH ₂ —, —CH ₂ S—, —CF═CF—, —CH═CH—, —OCO—CH═CH—, —C Represents ≡C- or a single bond,
A ⁸¹ , A ⁸² and A ⁸³ each independently represent a phenylene group, a cyclohexylene group, a dioxolanediyl group, a cyclohexenylene group, a bicyclo [2.2.2] octylene group, a piperidinediyl group, a naphthalenediyl group, or decahydronaphthalene. Represents a cyclic group selected from a diyl group, a tetrahydronaphthalenediyl group, or an indanediyl group, wherein the phenylene group, naphthalenediyl group, tetrahydronaphthalenediyl group, or indanediyl group is one or more —CH in the ring. = The group may be replaced by a nitrogen atom, and the cyclohexylene group, dioxolanediyl group, cyclohexenylene group, bicyclo [2.2.2] octylene group, piperidinediyl group, decahydronaphthalenediyl group, tetrahydronaphthalenediyl group Group or indandiyl The group may be one or two non-adjacent —CH ₂ — groups in the ring may be replaced by —O— and / or —S—, wherein one or more hydrogen atoms of said cyclic group Has 1 to 7 carbon atoms, wherein one or two or more hydrogen atoms may be replaced by fluorine or chlorine atoms, fluorine atom, chlorine atom, bromine atom, CN group, NO ₂ group An alkyl group, an alkoxy group, an alkylcarbonyl group or an alkoxycarbonyl group may be substituted;
m ₈₁ , m ₈₂ and m ₈₃ are each 0 or 1, and m ₈₁ + m ₈₂ + m ₈₃ is 1, 2 or 3.
CH ^{* 81} and CH ^{* 82} each independently represent a chiral divalent group;
CH ^{* 83} represents a chiral trivalent group.

Here, the chiral divalent group used for CH ^{* 81} and CH ^{* 82} is the following divalent group having an asymmetric atom.

And the following divalent groups with axial asymmetry

Is preferred. However, in these divalent groups used for CH ^{* 81} and CH ^{* 82} , any one or two or more arbitrary hydrogen atoms of the benzene ring are halogen atoms (F, Cl, Br, I), methyl groups , A methoxy group, —CF ₃ , —OCF ₃ , and any one or more carbon atoms of the benzene ring may be substituted with a nitrogen atom.
As the chiral trivalent group used for CH ^{* 83} , —X ⁸³ (Z ⁸³ A ⁸³ ) m ₈₃ R ⁸³ is located at any position of the chiral divalent group used for CH ^{* 81} and CH ^{* 82.} What is necessary is just to become a trivalent group by being able to couple | bond together.

  More preferably, the following compounds having an isosorbide skeleton as a chiral divalent group are exemplified.

In the formula, each of R ⁹¹ and R ⁹² independently represents a linear or branched alkyl group having 1 to 30 carbon atoms, a hydrogen atom, or a fluorine atom, and one or two or more adjacent groups of the alkyl group -CH ₂ you are not - group _{-O -, - S -, -} NH -, - N (CH 3) -, - CO -, - CO-O -, - O-CO -, - O-CO- O—, —S—CO—, —CO—S—, —O—SO ₂ —, —SO ₂ —O—, —CH═CH—, —C≡C—, a cyclopropylene group or —Si (CH ₃ ) May be replaced with _2- , and one or more hydrogen atoms of the alkyl group may be replaced with a fluorine atom, a chlorine atom, a bromine atom or a CN group, and may have a polymerizable group, The alkyl group may include a condensed or spirocyclic system, and the alkyl group is one or two. It may contain one or more aromatic or aliphatic rings that can contain the above heteroatoms, and these rings may be optionally substituted with an alkyl group, an alkoxy group, or a halogen. ,
Z ⁹¹ and Z ⁹² are each independently —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N (R ^a ) —. , —N (R ^a ) —CO—, —OCH ₂ —, —CH ₂ O—, —SCH ₂ —, —CH ₂ S—, —CF ₂ O—, —OCF ₂ —, —CF ₂ S—, _{-SCF 2 -, - CH 2 CH} 2 -, - CF 2 CH 2 -, - CH 2 CF 2 -, - CF 2 CF 2 -, - CH = CH -, - CF = CH -, - CH = CF- , —CF═CF—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH— or a single bond, —CO—N (R ^a ) — or —N R ^{a in} (R ^a ) —CO— represents ^a hydrogen atom or ^a linear or branched alkyl group having 1 to 4 carbon atoms.

The temperature width at which the liquid crystal composition layer causes critical softening is preferably 10 ° C. or higher, more preferably 15 ° C. or higher, and particularly preferably 20 ° C. or higher. Here, the temperature range at which critical softening occurs is, for example, in FIG. 5, the temperature at which the layer compression modulus B has a maximum in the SmA phase, and the SmA-SmC transition point (the temperature at which the layer compression modulus B has a minimum, Temperature difference with TAC).
Further, the temperature range in which the liquid crystal composition layer has a normalized electroclinic effect coefficient (χ ′) value of 0.2 is preferably 5 ° C. or more, more preferably 8 ° C. or more, and more preferably 10 ° C. or more. It is particularly preferred that Here, the electroclinic effect coefficient (also referred to as χ, electroclinic coefficient, or electroclinic coefficient) is the ratio of the magnitude of the tilt angle to the intensity of the electric field, and the normalized electroclinic effect coefficient (χ ′) This means that the value of the electroclinic effect coefficient (χ) is normalized with the value at the SmA-SmC transition point (TAC) as 1. Some liquid crystal compositions have no SmA-SmC transition point (TAC) due to the disappearance of SmC. In that case, a phase diagram is created to measure the critical softening phenomenon, the electroclinic effect coefficient The value of the electroclinic effect coefficient (χ) at the SmA-SmC transition point (TAC) may be predicted by extrapolation or the like by measuring (χ). If this prediction is difficult, the normalized gradient effect coefficient (χ ′) may be obtained by normalizing to the value of the gradient effect coefficient (χ) at the lowest SmA temperature.

The liquid crystal composition contains a mixture of at least two kinds of liquid crystal materials having different molecular lengths, and the ratio of the molecular lengths is preferably 1.0: 1.2 or more, and is 1.0: 1.3 or more. Is more preferable, and 1.0: 1.5 or more is particularly preferable. In this case, the liquid crystal composition has a general liquid crystal compound having at least one kind of core part, at least one kind of general liquid crystal compound connected in two dimers, three connected oligomers, It is preferable to include a liquid crystal compound having a long molecular length selected from several connected oligomers. The molecular length can be estimated from the most stable molecular structure of energy obtained by Hartree-Fock method using, for example, Spatran '06 (manufactured by Wavefunction). Alternatively, it can be estimated experimentally from the layer spacing of the smectic A phase or from the layer spacing and tilt angle of the smectic C phase.
It is preferable that the liquid crystal composition layer has a temperature lower than the temperature at which the liquid crystal composition exhibits the SmA phase, and the liquid crystal composition having the same composition exhibits the SmC phase.

The operating temperature of the liquid crystal element of the present invention operates at a temperature lower than the maximum temperature among the SmA-SmC transition temperatures (or the upper limit temperature of the SmC phase) of two or more liquid crystal compounds contained in the liquid crystal composition. The liquid crystal compound (main compound), which is the component having the largest mass fraction, is preferably operated at a temperature lower than the SmA-SmC transition temperature (or the upper limit temperature of the SmC phase) exhibited by itself. When any one of the liquid crystal compounds has no SmA phase on the higher temperature side than the SmC phase, or has another liquid crystal phase between the SmC phase and the SmA phase, the liquid crystal compound shows SmA-SmC alone. Instead of the transition temperature, an upper limit temperature at which the liquid crystal compound alone exhibits an SmC phase can be used.
The operating temperature of the liquid crystal element of the present invention is preferably within the temperature range in which the liquid crystal composition exhibits an SmA phase. The liquid crystal composition preferably has an SmC phase on the low temperature side in the composition, but is not necessarily limited thereto, and has a liquid crystal phase other than the SmC phase on the low temperature side of the SmA phase, or a clear SmA-SmC transition point. It is also possible that it does not appear in
The operating temperature range of the liquid crystal element is, for example, an upper limit temperature at which the main compound alone exhibits an SmC phase, and a liquid crystal composition exhibits an SmA phase as a temperature range that is a difference between the preferred upper limit temperature and the lower limit temperature exemplified above. It is preferable that the temperature difference of minimum temperature is 20 degreeC or more.

The liquid crystal material may contain one or more liquid crystal compounds, and may further be a liquid crystal material containing a liquid crystalline or non-liquid crystalline polymerizable compound. When the liquid crystal composition contains a polymerizable compound, the composition preferably contains at least one polymerization initiator. The polymerization initiator is a useful compound for efficiently polymerizing the polymerizable compound in the liquid crystal composition. As the polymerization initiator, a photopolymerization initiator is preferable, and specifically, the following are preferable.
BASF Irgacure 651, Irgacure 184, Irgacure 907, Irgacure 127, Irgacure 369, Irgacure 379, Irgacure 819, Irgacure OXE01, Irgacure OXE02, Lucyrin TPO, Darocur 1173. LAMBSON Esacure 1001M, Esacure KIP150, Speed Cure BEM, Speed Cure BMS, Speed Cure PBZ, Benzophenone.
One kind of these polymerization initiators may be used, but two or more kinds may be used, and a sensitizer or the like may be added.

  In the liquid crystal composition, if necessary, pigments, dyes, antioxidants, ultraviolet absorbers, non-reactive oligomers and inorganic fillers, organic fillers, polymerization inhibitors, antifoaming agents, leveling agents, plasticizers, A silane coupling agent or the like may be added as appropriate.

Hereinafter, the present invention will be specifically described with reference to examples.
(Liquid crystal compound)
As one model of two types of SmC phase mixed systems, the following mixed system of 10B and P10O10 was used. 10B has a phenyl ring and an ester bond as a core, and also has a chiral center (carbon atom appended with * in the following chemical formula) in one side chain. P10O10 has a phenylpyrimidine skeleton.

In the 10B-P10O10 mixed system, a phase diagram in which the SmA phase is widely stabilized as described above is shown. The transition temperature of 10B identified by observation with a polarizing microscope is Iso-150 ° C.-SmA-130 ° C.-SmC ^* , but when 10% of P10O10 is added, the SmA-SmC ^* transition point is lowered to 115 ° C. and 20%. In addition, SmA-SmC ^* transition point decreased to 75 ° C., and in the addition of 30%, SmA was reached to room temperature and no SmC ^* phase was expressed. Since P10O10 shows Iso-77 ° C.-SmA-73 ° C.-SmC and smectic C phase, the mixture of 10B and P10O10 showing the smectic C phase disappeared and the smectic A phase was stabilized. I understand.

  10B: P10O10 = 90%: 10%, 80%: When the layer compression modulus was measured for a mixture of 20%, in the SmA phase in the vicinity of the SmA-SmC transition point, it was found that the molecules easily inclined in the layer. It was found that the reflected critical softening occurred toward the phase transition point. The temperature range in which critical softening occurs is 15 ° C for a mixture of 10B: P10O10 = 90%: 10%, 35 ° C for a mixture of 80%: 20%, and the temperature range in which critical softening occurs with 10B alone (5 )) Was observed.

  In order to measure the electroclinic effect, the tilt angle induced by applying an electric field in the SmA phase enclosed in a horizontally oriented cell was measured. As an index of the electroclinic effect, an electroclinic coefficient, which is a value obtained by dividing the tilt angle by the electric field, was obtained, and the value was normalized and evaluated by Tc (SmA-SmC transition temperature) of each mixture. It is preferable that the temperature range in which the normalized electroclinic coefficient (χ ′) is a certain level or more is wide, but when the temperature range in which the normalized electroclinic coefficient (χ ′) is 0.2 or more is examined, 10B: P10O10 = 90 ° C: 8 ° C for the mixture of 10%, 14 ° C for the mixture of 80%: 20%, a temperature range wider than the temperature range of 10B alone (4 ° C) can be obtained. It was found that it is suitable for an element using the tilt effect.

  The absolute value of the bare electroclinic coefficient, excluding effects that depend on critical phenomena, varies greatly depending on the molecular shape of the liquid crystal sample, the magnitude of spontaneous polarization, etc. It is considered that it is sufficiently possible to increase the magnitude of the induced tilt angle by performing strictly. In addition, if a sample having a sufficient thickness is used in the model system of this time, it is considered that sufficient retardation can be earned to bear the display function.

11 ... liquid crystal molecule, 12 ... cone, 13 ... layer normal.

Claims (10)

  A liquid crystal layer containing a liquid crystal composition is sandwiched between the first substrate, the second substrate, and the first substrate and the second substrate, and the liquid crystal layer is controlled on at least one of the substrates. A liquid crystal element having an electrode, wherein the liquid crystal composition exhibits a smectic A phase and contains at least two kinds of liquid crystal compounds, and each of the liquid crystal compounds independently has a smectic C phase. element.   The liquid crystal element according to claim 1, wherein the liquid crystal composition layer causes critical softening at a temperature range of 10 ° C. or more.   3. The liquid crystal device according to claim 1, wherein the liquid crystal composition layer has a temperature range in which a value of a normalized electroclinic effect coefficient (χ ′) is 0.2 is 5 ° C. or more.   4. The liquid crystal composition according to claim 1, wherein the liquid crystal composition contains a liquid crystal having at least one phenylpyrimidine skeleton in the core portion and a liquid crystal having at least one ester bond in the core portion. Liquid crystal element.   The liquid crystal element according to any one of claims 1 to 4, wherein the liquid crystal composition contains a liquid crystal forming at least one monolayer and a liquid crystal forming at least one bilayer.   The liquid crystal device according to claim 1, wherein the liquid crystal composition includes a mixture of at least two liquid crystal materials having different molecular lengths, and a ratio of the molecular lengths is 1: 1.2 or more. .   The liquid crystal element according to claim 1, wherein the liquid crystal composition contains at least two kinds of liquid crystal materials having molecular structures incompatible with each other.   The normal layer of the smectic A phase indicated by the liquid crystal composition is substantially horizontal to the substrate, and the first substrate and the second substrate each have an electrode for controlling the liquid crystal layer, The liquid crystal element according to claim 1, wherein an electric field generated by the electrode is substantially perpendicular to the substrate.   The layer normal of the smectic A phase indicated by the liquid crystal composition is substantially perpendicular to the substrate, and the electric field generated by the electrode controlling the liquid crystal layer is substantially horizontal to the substrate. The liquid crystal element according to claim 1.   The liquid crystal element according to claim 1, wherein the liquid crystal composition contains at least one chiral compound.

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