Liquid crystal composition and preparation method thereof, and display panel

Abstract

A liquid crystal composition and a preparation method thereof, and a display panel. The liquid crystal composition comprises: a rod-shaped monomer molecule mixture, a chiral agent and a bent molecule mixture, wherein the bent molecule mixture comprises a plurality of bent molecules.

Description

Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a liquid crystal composition and a preparation method thereof, and a display panel. Background Art

[0002] So far, the oblique helical cholesteric phase has attracted extensive attention from researchers due to its nanoscale pitch, only orientation order but no position order, small birefringence, and the molecules have no chirality but the system has macroscopic chirality. Summary of the invention

[0003] The present disclosure provides a liquid crystal composition and a preparation method thereof, and a display panel.

[0004] In a first aspect, the present disclosure provides a liquid crystal composition, which includes: a rod-shaped monomer molecule mixture, a chiral agent, and a bent molecule mixture, wherein the bent molecule mixture includes a plurality of bent molecules.

[0005] In some embodiments, the bending elastic constant of the bent molecule is smaller than the twisting elastic constant.

[0006] In some embodiments, the bent molecule mixture includes: a bent molecule dimer and / or a bent molecule trimer, wherein the bent molecule dimer has the following general formula I or general formula II:

[0007]

[0008] The bent molecular trimer has the following general formula III:

[0009]

[0010] Wherein, n is a natural number, 5≤n≤11; n' is 5 or 7; X, X' are selected from Formula IV and Formula V respectively, and Y, Y' are independently selected from Formula VI:

[0011]

[0012] Among them, M 1 、M 2 are independently selected from hydrogen atoms and fluorine atoms, K is cyano, C 2 —C 6 Alkyl or C 2 —C 6 The alkoxy group, Z, Z' are independently selected from methylene and oxygen atoms.

[0013] In some embodiments, the weight proportion of the bent molecule mixture in the liquid crystal composition is less than the weight proportion of the rod-shaped monomer molecule mixture in the liquid crystal composition.

[0014] In some embodiments, the weight percentage of the bent molecule mixture in the liquid crystal composition is between 30% and 70%, the weight percentage of the rod-shaped monomer molecule mixture in the liquid crystal composition is between 30% and 70%, and the weight percentage of the chiral agent in the liquid crystal composition is between 0.5% and 10%.

[0015] In some embodiments, the weight percentage of the bent molecule mixture in the liquid crystal composition is between 40% and 60%, the weight percentage of the rod-shaped monomer molecule mixture in the liquid crystal composition is between 40wt% and 55wt%, and the weight percentage of the chiral agent in the liquid crystal composition is between 0.5% and 5%.

[0016] In some embodiments, the rod-shaped monomer molecule mixture is selected from at least two of the following compounds:

[0017]

[0018]

[0019] Where J is C 2 , C 5 , C 7 Alkyl or C 2 —C 6 , C 8 Alkoxy; L is C 1 —C 2 Alkoxy, N is C 2 —C 5 When O is methyl, P is C 3 , C 5 The alkyl chain, when O is C 2 When the methoxy group is 2 , C 3 , C 5 The alkyl chain of 2 , C 3 The alkyl chain of 1 , C 3 , C 5 Alkoxy, S is C 3 , C 5 When T is methyl, U is C 2 , C 3 The alkyl chain of 2 When the methoxy group is 2 , C 3 , C 5 of methyl chains.

[0020] In some embodiments, the chiral agent is selected from at least one of CB15, S811, R811, S1011, R1011, S2011, R2011, S5011 and R5011.

[0021] In some embodiments, the bent molecular mixture comprises: a first compound, a second compound, a third compound, a fourth compound, a fifth compound and a sixth compound,

[0022] Wherein, the molecular formula of the first compound is:

[0023]

[0024] The molecular formula of the second compound is:

[0025]

[0026] The molecular formula of the third compound is:

[0027]

[0028] The molecular formula of the fourth compound is:

[0029]

[0030] The molecular formula of the fifth compound is:

[0031]

[0032] The molecular formula of the sixth compound is:

[0033]

[0034] Among them, the weight proportion of the first compound in the curved molecular mixture is between 55% and 65%, the weight proportion of the second compound in the curved molecular mixture is between 10% and 15%, the weight proportion of the third compound in the curved molecular mixture is between 8% and 13%, the weight proportion of the fourth compound in the curved molecular mixture is between 5% and 10%, the weight proportion of the fifth compound in the curved molecular mixture is between 3% and 7%, and the weight proportion of the sixth compound in the curved molecular mixture is between 2% and 6%.

[0035] In some embodiments, the rod-shaped monomer molecule mixture includes a first monomer, a second monomer, a third monomer, a fourth monomer, a fifth monomer, a sixth monomer, and a seventh monomer;

[0036] The molecular formula of the first monomer is:

[0037]

[0038] The molecular formula of the second monomer is:

[0039]

[0040] The molecular formula of the third monomer is:

[0041] The molecular formula of the fourth monomer is:

[0042] The molecular formula of the fifth monomer is:

[0043]

[0044] The molecular formula of the sixth monomer is:

[0045]

[0046] The molecular formula of the seventh monomer is:

[0047]

[0048] Among them, the weight proportion of the first monomer in the rod-shaped monomer molecule mixture is between 55% and 65%, the weight proportion of the second monomer in the rod-shaped monomer molecule mixture is between 15% and 20%, the weight proportion of the third monomer in the rod-shaped monomer molecule mixture is between 5% and 15%, the weight proportion of the fourth monomer in the rod-shaped monomer molecule mixture is between 2% and 7%, the weight proportion of the fifth monomer in the rod-shaped monomer molecule mixture is between 2% and 5%, the weight proportion of the sixth monomer in the rod-shaped monomer molecule mixture is between 2% and 5%, and the weight proportion of the seventh monomer in the rod-shaped monomer molecule mixture is between 2% and 5%.

[0049] In a second aspect, the present disclosure provides a method for preparing a liquid crystal composition, comprising:

[0050] The rod-shaped monomer molecule mixture, the chiral agent and the bent molecule mixture are uniformly mixed in an organic solvent to obtain a liquid crystal mixture; wherein the bent molecule mixture includes a plurality of bent molecules;

[0051] The organic solvent in the liquid crystal mixture is evaporated to obtain the liquid crystal composition.

[0052] In some embodiments, the organic solvent includes at least one of acetone, methanol, ethanol, tetrahydrofuran, dichloromethane and chloroform.

[0053] In a third aspect, the present disclosure provides a display panel, comprising a first substrate and a second substrate arranged opposite to each other, and a liquid crystal layer located between the first substrate and the second substrate, wherein the liquid crystal layer comprises the above-mentioned liquid crystal composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0055] Figure 1 The liquid crystal composition provided in the embodiment of the present disclosure is in a state when no voltage is applied between the first electrode layer and the second electrode layer.

[0056] Figure 2A The liquid crystal composition provided in the embodiment of the present disclosure is in a state when a first voltage is applied between the first electrode layer and the second electrode layer.

[0057] Figure 2B The liquid crystal composition provided in the embodiment of the present disclosure is in a state when a second voltage is applied between the first electrode layer and the second electrode layer.

[0058] Figure 2C The liquid crystal composition provided in the embodiment of the present disclosure is in a state when a third voltage is applied between the first electrode layer and the second electrode layer.

[0059] Figure 3 This is a reflection spectrum diagram of the liquid crystal composition provided in an embodiment of the present disclosure at 23°C.

[0060] Figure 4 This is a reflection spectrum diagram of the liquid crystal composition provided in an embodiment of the present disclosure at 27°C.

[0061] Figure 5 This is a reflection spectrum diagram of the liquid crystal composition provided in an embodiment of the present disclosure at 33°C.

[0062] Figure 6 Schematic diagram of a method for preparing a liquid crystal composition provided in some embodiments of the present disclosure.

[0063] Figure 7 A schematic diagram of a display panel provided in some embodiments of the present disclosure. DETAILED DESCRIPTION

[0064] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0065] In recent years, people have shown great interest in smart materials and devices with tunable stimulus-responsive reflected light. Research on materials that can dynamically control the reflection of visible and near-infrared light is one of the important research directions. Among the materials known to selectively reflect light, cholesteric liquid crystals (also known as self-assembled helical superstructures) are formed by chiral elongated organic molecules in a specific temperature range between solid crystals and isotropic melts. They can usually be obtained simply by doping chiral dopants into non-chiral nematic liquid crystal hosts to spontaneously form a helical superstructure. The molecules of cholesteric liquid crystals self-assemble into a periodic structure in which the local orientation of the molecules (called directors) rotates around the helical axis and remains perpendicular to the helical axis. Due to its unique optical activity, circularly polarized light dichroism, and selective Bragg reflection, it has shown broad application prospects in optical materials, but conventional cholesteric liquid crystals can only achieve the regulation of its single reflection color or scattering state by adjusting the voltage. In 1976, De Gennis and Meyer theoretically predicted the twisting-bending change of the cholesteric phase structure with oblique helical arrangement of molecules based on the interaction law between polar molecules. It was not until 2011 that the existence of this change was confirmed. In the cholesteric phase liquid crystal with oblique helical arrangement, the molecules rotate around the helical axis, but at an oblique angle to the axis, rather than perpendicular to the aforementioned helical structure. Experiments have shown that this oblique helical cholesteric phase liquid crystal (ChOH) exists in an external electric field or magnetic field. Compared with traditional cholesteric phase liquid crystal, the biggest advantage of oblique helical cholesteric phase liquid crystal is that it can change the periodic pitch of the helical structure by applying an external electric field without changing the periodic change of molecular orientation. Therefore, people can use a single ChOH device to achieve selective reflection of light from ultraviolet light to visible light and then to infrared light by adjusting the voltage. The necessary condition for the formation of this phase is that the bending elastic constant K33 should be an extremely low value compared with the torsion elastic constant K22.

[0066] So far, oblique helical cholesteric liquid crystals have attracted extensive attention from researchers due to their nanoscale pitch, only orientation order but no position order, small birefringence, and molecular non-chirality, but the system has macroscopic chirality. However, most of the bent dimer materials that induce the formation of conical helical cholesteric phases are in a conventional nematic phase at relatively high temperatures (usually above 100 degrees Celsius), and form a twisted bend nematic phase (Ntb phase) at a very narrow temperature. This results in the conical helical cholesteric liquid crystals studied previously being able to achieve electric field-controlled selective reflection of light only within a narrow temperature range above room temperature. Therefore, it is urgent to find a conical helical liquid crystal composition with a wide temperature range that can meet practical applications.

[0067] The embodiment of the present disclosure provides a liquid crystal composition, including: a rod-shaped monomer molecule mixture, a chiral agent and a bent molecule mixture, wherein the bent molecule mixture includes a plurality of bent molecules.

[0068] In the disclosed embodiment, the liquid crystal composition includes a bent molecule mixture, which can induce the liquid crystal composition to present a conical helical cholesteric phase structure when powered. The bent molecule mixture includes a plurality of bent molecules, and since different bent molecules have different phase transition temperatures, doping with different bent molecules can effectively broaden the applicable temperature range of the liquid crystal composition.

[0069] In some embodiments, the weight proportion of the bent molecule mixture in the liquid crystal composition is less than the weight proportion of the rod-shaped monomer molecule mixture in the liquid crystal composition, which is conducive to the liquid crystal composition being induced to have a conical spiral cholesteric phase structure when powered on. In one example, the weight proportion of the bent molecule mixture in the liquid crystal composition is between 30% and 70%, the weight proportion of the rod-shaped monomer molecule mixture in the liquid crystal composition is between 30% and 70%, and the weight proportion of the chiral agent in the liquid crystal composition is between 0.5% and 10%. This ratio can ensure that the liquid crystal composition is induced to have a conical spiral cholesteric phase structure when powered on, and is conducive to widening the applicable temperature range of the liquid crystal material and improving the stability in the liquid crystal composition.

[0070] Preferably, the weight proportion of the bent molecular mixture in the liquid crystal composition is between 40% and 60%, the weight proportion of the rod-shaped monomer molecular mixture in the liquid crystal composition is between 40% and 55%, and the weight proportion of the chiral agent in the liquid crystal composition is between 0.5% and 5%, thereby further broadening the applicable temperature range of the liquid crystal composition and improving the stability of the liquid crystal composition.

[0071] In some embodiments, the bent molecule has a very small bending elastic constant K 33 , where the bending elastic constant K 33 Smaller than the torsional elastic constant K of the bent molecule 22 .

[0072] In some embodiments, the bent molecule mixture includes: a bent molecule dimer and / or a bent molecule trimer, wherein the bent molecule dimer has the following general formula I or general formula II:

[0073]

[0074] The bent molecular trimer has the following general formula III:

[0075]

[0076] Wherein, n is a natural number, 5≤n≤11; n' is 5 or 7; X, X' are selected from Formula IV and Formula V respectively, and Y, Y' are independently selected from Formula VI:

[0077]

[0078]

[0079] Among them, M 1 、M 2 are independently selected from hydrogen atoms and fluorine atoms, K is cyano, C 2 —C 6 Alkyl or C 2 —C 6 The alkoxy group, Z, Z' are independently selected from methylene and oxygen atoms.

[0080] The above-mentioned bent molecular dimers have different phase transition temperatures on the basis of satisfying the minimum bending elastic constant. By mixing bent molecular dimers of different molecular formulas, the stability of the conical helical liquid crystal material can be effectively improved and its applicable temperature range can be adjusted.

[0081] Compared with the bent molecular dimer, the bent molecular trimer can improve the overall thermal stability of the conical helical liquid crystal composition due to its special bent conformation and molecular intercalation over two-thirds of the molecular length. Therefore, in a preferred embodiment of the present invention, the bent molecular mixture can simultaneously include: a bent molecular dimer and a bent molecular trimer.

[0082] In some embodiments, the rod-shaped monomer molecule mixture is selected from at least two of the following compounds:

[0083]

[0084]

[0085] Where J is C 2 , C 5 , C 7 Alkyl or C 2 —C 6 , C 8 Alkoxy; L is C 1 —C 2 Alkoxy, N is C 2 —C 5 When O is methyl, P is C 3 , C 5 The alkyl chain, when O is C 2 When the methoxy group is 2 , C 3 , C 5 The alkyl chain of 2 , C 3 The alkyl chain of 1 , C 3, C 5 Alkoxy, S is C 3 , C 5 When T is methyl, U is C 2 , C 3 The alkyl chain of 2 When the methoxy group is 2 , C 3 , C 5 of methyl chains.

[0086] In some embodiments, the rod-shaped monomer molecule mixture includes molecules represented by each of the above formulas VII to XIV.

[0087] In some embodiments, the chiral agent is selected from at least one of CB15, S811, R811, S1011, R1011, S2011, R2011, S5011, and R5011.

[0088] The molecular formula of CB15 is as follows:

[0089]

[0090] The molecular formula of S811 is as follows:

[0091]

[0092] The molecular formula of R811 is as follows:

[0093]

[0094] The molecular formula of S1011 is as follows:

[0095]

[0096] The molecular formula of R1011 is as follows:

[0097]

[0098] The molecular formula of S2011 is as follows:

[0099]

[0100] The molecular formula of R2011 is as follows:

[0101] The molecular formula of S5011 is as follows:

[0102]

[0103] The molecular formula of R5011 is as follows:

[0104]

[0105] In some embodiments, the bent molecular mixture includes: a first compound, a second compound, a third compound, a fourth compound, a fifth compound and a sixth compound. The molecular formula of the first compound is:

[0106]

[0107] The molecular formula of the second compound is:

[0108]

[0109] The molecular formula of the third compound is:

[0110]

[0111] The molecular formula of the fourth compound is:

[0112]

[0113] The molecular formula of the fifth compound is:

[0114]

[0115] The molecular formula of the sixth compound is:

[0116]

[0117] Table 1 shows the structures and hydrogen spectrum data of each compound.

[0118]

[0119]

[0120] In some embodiments, the weight proportion of the first compound in the bent molecule mixture is between 55% and 65%, for example, the weight proportion of the first compound in the bent molecule mixture is 55% or 56% or 57% or 58% or 59% or 60% or 61% or 62% or 63% or 64% or 65%. The weight proportion of the second compound in the bent molecule mixture is between 10% and 15%, for example, the weight proportion of the second compound in the bent molecule mixture is 10% or 11% or 12% or 13% or 15%. The weight proportion of the third compound in the bent molecule mixture is between 8% and 13%, for example, the weight proportion of the third compound in the bent molecule mixture is 8% or 9% or 10% or 11% or 12% or 13%. The weight proportion of the fourth compound in the bent molecule mixture is between 5% and 10%, for example, the weight proportion of the fourth compound in the bent molecule mixture is 5% or 6% or 7% or 8% or 9% or 10%. The weight proportion of the fifth compound in the bent molecule mixture is between 3% and 7%, for example, the weight proportion of the fifth compound in the bent molecule mixture is 3% or 4% or 5% or 6% or 7%. The weight proportion of the sixth compound in the bent molecule mixture is between 2% and 6%. For example, the weight proportion of the sixth compound in the bent molecule mixture is 2% or 3% or 4% or 5% or 6%.

[0121] In some embodiments, the rod-shaped monomer molecule mixture includes a first monomer, a second monomer, a third monomer, a fourth monomer, a fifth monomer, a sixth monomer, and a seventh monomer.

[0122] The molecular formula of the first monomer is:

[0123]

[0124] The molecular formula of the second monomer is:

[0125]

[0126] The molecular formula of the third monomer is:

[0127]

[0128] The molecular formula of the fourth monomer is:

[0129]

[0130] The molecular formula of the fifth monomer is:

[0131]

[0132] The molecular formula of the sixth monomer is:

[0133]

[0134] The molecular formula of the seventh monomer is:

[0135]

[0136] Among them, the weight proportion of the first monomer in the rod-shaped monomer molecule mixture is between 55% and 65%, for example, the weight proportion of the first monomer in the rod-shaped monomer molecule mixture is 55% or 57% or 60% or 62% or 64% or 65%. The weight proportion of the second monomer in the rod-shaped monomer molecule mixture is between 15% and 20%, for example, the weight proportion of the second monomer in the rod-shaped monomer molecule mixture is 15% or 16% or 18% or 20%. The weight proportion of the third monomer in the rod-shaped monomer molecule mixture is between 5% and 15%, for example, the weight proportion of the third monomer in the rod-shaped monomer molecule mixture is 5% or 8% or 10% or 12% or 15%. The weight proportion of the fourth monomer in the rod-shaped monomer molecule mixture is between 2% and 7%, for example, the weight proportion of the fourth monomer in the rod-shaped monomer molecule mixture is 2% or 5% or 7%. The weight proportion of the fifth monomer in the rod-shaped monomer molecule mixture is between 2% and 5%, for example, the weight proportion of the fifth monomer in the rod-shaped monomer molecule mixture is 2% or 3% or 5%. The weight proportion of the sixth monomer in the rod-shaped monomer molecule mixture is between 2% and 5%, for example, the weight proportion of the sixth monomer in the rod-shaped monomer molecule mixture is 2%, 3%, or 5%. The weight proportion of the seventh monomer in the rod-shaped monomer molecule mixture is between 2% and 5%, for example, the weight proportion of the seventh monomer in the rod-shaped monomer molecule mixture is 2%, 3%, or 5%.

[0137] The liquid crystal material and its physical properties disclosed herein are further described below in conjunction with specific embodiments and comparative examples.

[0138] Embodiment 1:

[0139] In dichloromethane, the first compound, the second compound, the third compound, the fourth compound, the fifth compound and the sixth compound in Table 1 are mixed to obtain a bent molecular mixture, wherein the weight proportion of the first compound in the bent molecular mixture is 60%, the weight proportion of the second compound in the bent molecular mixture is 13%, the weight proportion of the third compound in the bent molecular mixture is 10%, the weight proportion of the fourth compound in the bent molecular mixture is 8%, the weight proportion of the fifth compound in the bent molecular mixture is 5%, and the weight proportion of the sixth compound in the bent molecular mixture is 4%); the above-mentioned first to seventh monomers are mixed to obtain a rod-shaped monomer molecular mixture; wherein the weight proportion of the first monomer in the rod-shaped monomer molecular mixture is 60%, the weight proportion of the second monomer in the rod-shaped monomer molecular mixture is 16%, the weight proportion of the third monomer in the rod-shaped monomer molecular mixture is 10%, the weight proportion of the fourth monomer in the rod-shaped monomer molecular mixture is 5%, the weight proportion of the fifth monomer in the rod-shaped monomer molecular mixture is 3%, the weight proportion of the sixth monomer in the rod-shaped monomer molecular mixture is 3%, and the weight proportion of the seventh monomer in the rod-shaped monomer molecular mixture is 3%). The above-mentioned curved molecular mixture, rod-shaped monomer molecular mixture and chiral agent R811 were mixed in a weight ratio of 45:50:5, and after evaporating the solvent, a cholesteric liquid crystal composition with an electrically induced conical spiral arrangement was obtained. The liquid crystal composition was poured between the first substrate and the second substrate at a higher temperature to make a display panel, and the temperature was lowered to room temperature at a rate of 1-5°C / min for testing.

[0140] The first substrate includes a first base substrate and a first electrode layer arranged on the first base substrate, the second substrate includes a second base substrate and a second electrode layer arranged on the second base substrate, the first electrode layer is arranged on the side of the first base substrate facing the liquid crystal material, and the second electrode layer is arranged on the side of the second base substrate facing the liquid crystal material. Both the first electrode layer and the second electrode layer can be electrodes made of transparent materials (such as ITO, etc.).

[0141] Figure 1 The state of the liquid crystal composition provided in the embodiment of the present disclosure when no voltage is applied between the first electrode layer and the second electrode layer; Figure 2A The state of the liquid crystal composition provided in the embodiment of the present disclosure when a first voltage is applied between the first electrode layer and the second electrode layer, Figure 2B The state of the liquid crystal composition provided in the embodiment of the present disclosure when a second voltage is applied between the first electrode layer and the second electrode layer, Figure 2C In the state of the liquid crystal composition provided in the embodiment of the present disclosure when a third voltage is applied between the first electrode layer and the second electrode layer, the first voltage E1>the second voltage E2>the third voltage E3. Figure 3This is a reflection spectrum diagram of the liquid crystal composition provided in the embodiment of the present disclosure at 23°C, Figure 4 This is a reflection spectrum diagram of the liquid crystal composition provided in the embodiment of the present disclosure at 27°C, Figure 5 The reflection spectrum of the liquid crystal composition provided in the embodiment of the present disclosure at 33°C. Figures 1 to 5 As shown in FIG. 1 , the liquid crystal composition prepared in Example 1 can achieve narrow bandwidth reflection in the full spectrum range by adjusting the voltage at 20°C to 35°C. When no voltage is applied between the first electrode layer 12 and the second electrode layer 22, the liquid crystal composition is Figure 1 The weak focal conic scattering state shown in the figure; when a large voltage E1 is applied between the first electrode layer 12 and the second electrode layer 22, the liquid crystal composition is in a field nematic state. At this time, the display panel is in a transparent state. By reducing the voltage between the first electrode layer 12 and the second electrode layer 22 (that is, reducing the electric field strength between the first electrode layer 12 and the second electrode layer 22), the liquid crystal composition can show a reflection peak change from blue to green to red, and finally return to a weak focal conic state. The process is reversible and has good stability. Among them, at 23°C, when the electric field strength is 0.94V / μm, the reflection peak is around 480nm; when the electric field strength is 0.84V / μm, the reflection peak is around 550nm; when the electric field strength is 0.73V / μm, the reflection peak is around 630nm. At 27°C, when the electric field strength is reduced to 1.25V / μm, the reflection peak is around 460nm; when the electric field strength is 1.03V / μm, the reflection peak is around 570nm; when the electric field strength is reduced to 0.88V / μm, the reflection peak is around 660nm. At 33°C, when the electric field strength is reduced to 1.81V / μm, the reflection peak is around 460nm; when the electric field strength is 1.69V / μm, the reflection peak is around 540nm; when the electric field strength is reduced to 1.44V / μm, the reflection peak is around 630nm. For the liquid crystal composition in this embodiment 1, by reducing the voltage between the first electrode layer 12 and the second electrode layer 22 (that is, reducing the electric field strength between the first electrode layer 12 and the second electrode layer 22), the liquid crystal composition can show a reflection peak change from blue to green to red, and finally return to a weak focal conic state. This process is reversible and has good stability.

[0142] Comparative Example 1:

[0143] In dichloromethane, the first to seventh monomers are mixed to obtain a rod-shaped monomer molecule mixture, wherein the content of each monomer in the rod-shaped monomer molecule mixture is the same as in the above-mentioned embodiment 1. The monomer molecule mixture is mixed with the above-mentioned first compound and the chiral agent R5011 to obtain a cholesteric liquid crystal composition. Among them, the weight proportion of the first compound in the cholesteric liquid crystal composition is 49%, the weight proportion of the monomer molecule mixture in the cholesteric liquid crystal composition is 50%, and the weight proportion of the chiral agent in the cholesteric liquid crystal composition is 1%). After evaporating the solvent, a cholesteric liquid crystal composition with an electrically induced conical spiral arrangement is obtained. The liquid crystal composition is poured between the first substrate and the second substrate at a higher temperature to make a display panel, and the temperature is lowered to room temperature at a cooling rate of 1-5°C / min for testing.

[0144] It was found through testing that when a large voltage (e.g., 75V to 100V) was applied to the first electrode layer 12 and the second electrode layer 22, the display panel was in a transparent state, and lowering the voltage could achieve a change in the reflective color from blue to green to red, and finally back to a weak focal cone state, and the process was reversible, but the display panel showed a similar crystallization state after being placed overnight, and could not be used again. By comparison with Example 1, it can be seen that the applicable temperature range of the liquid crystal composition constructed by the bent molecules containing only the first compound is less than 5°C (i.e., the difference between the upper limit temperature and the lower limit temperature of the applicable temperature range is less than 5°C, wherein the lower limit temperature of the cholesteric phase is higher than room temperature 25°C), the range is narrow, and the stability is not high.

[0145] Comparative Example 2:

[0146] In dichloromethane, the first compound, the second compound, the third compound, the fifth compound and the sixth compound are mixed to obtain a bent molecule mixture, wherein the weight proportion of the first compound in the bent molecule mixture is 52%, the weight proportion of the second compound in the bent molecule mixture is 20%, the weight proportion of the third compound in the bent molecule mixture is 20%, the weight proportion of the fifth compound in the bent molecule mixture is 4%, and the weight proportion of the sixth compound in the bent molecule mixture is 4%. The first to seventh monomers are mixed to obtain a rod-shaped monomer molecule mixture, wherein the content of each monomer in the rod-shaped monomer molecule mixture is the same as in the above-mentioned embodiment 1. The bent molecule mixture, the rod-shaped monomer molecule mixture and the chiral agent R1011 are mixed to obtain a cholesteric liquid crystal composition. wherein the weight proportion of the bent molecule mixture in the cholesteric liquid crystal composition is 47%, the weight proportion of the rod-shaped monomer molecule mixture in the cholesteric liquid crystal composition is 50%, and the weight proportion of the chiral agent R1011 in the cholesteric liquid crystal composition is 3%. After the solvent is evaporated, a cholesteric liquid crystal composition that can induce a conical spiral when powered is obtained. The composition is poured between the first substrate and the second substrate at a relatively high temperature to form a display panel, and then cooled to room temperature at a cooling rate of 1-5°C / min for testing.

[0147] It was found through testing that when the temperature of the environment in which the display panel is located is high, when a large voltage (e.g., 75V to 100V) is applied to the first electrode layer 12 and the second electrode layer 22, the display panel is in a transparent state, and reducing the voltage can achieve a change in the reflective color from blue to green to red, and finally back to a weak focal conic state, and the process is reversible. However, it was found during the test that the lowest temperature at which the liquid crystal mixture presents a cholesteric phase is 26°C, so when the temperature and voltage are reduced, the liquid crystal mixture cannot change from the transparent state of the cholesteric phase to the reflective state, but directly changes to the transparent state of the non-cholesteric phase.

[0148] The display panel undergoes a phase transition to a transparent state, and no reflected color can be observed. Polarized light microscopy confirms that the lower limit of the cholesteric phase temperature range of the liquid crystal mixture is 26°C, which is much lower than the cholesteric phase temperature range of Example 1 and Comparative Example 1 and cannot be used.

[0149] Figure 6 Schematic diagram of a method for preparing a liquid crystal composition provided in some embodiments of the present disclosure, such as Figure 6 As shown, the preparation method comprises:

[0150] S1. Evenly mix the rod-shaped monomer molecule mixture, the chiral agent and the bent molecule mixture in an organic solvent to obtain a first mixture. The bent molecule mixture includes a plurality of bent molecules. In some embodiments, the organic solvent may include at least one of acetone, methanol, ethanol, tetrahydrofuran, dichloromethane and chloroform.

[0151] S2, evaporating the organic solvent in the first mixture to obtain a cholesteric liquid crystal composition that can induce a conical spiral arrangement when electrically applied.

[0152] In some embodiments, the weight percentage of the bent molecule mixture in the liquid crystal composition is between 30 wt% and 70 wt%. The weight percentage of the rod-shaped monomer molecule mixture in the liquid crystal composition is between 30 wt% and 70 wt%, and the weight percentage of the chiral agent in the liquid crystal composition is between 0.5 wt% and 10 wt%.

[0153] Figure 7 is a schematic diagram of a display panel provided in some embodiments of the present disclosure, such as Figure 7 As shown, it includes: a first substrate 10 and a second substrate 20 arranged opposite to each other, and a liquid crystal layer 30 located between the first substrate 10 and the second substrate 20, and the liquid crystal layer 30 includes the liquid crystal composition described above.

[0154] The first substrate 10 may include: a first base substrate 11 and a first electrode layer 12 located on the side of the first base substrate 11 facing the liquid crystal layer 30, and the second substrate 20 may include: a second base substrate 21 and a second electrode layer 22 located on the side of the second base substrate 21 facing the liquid crystal layer 30. The display panel may include a plurality of sub-pixels, the first electrode layer 12 may include a pixel electrode located in each sub-pixel, and the second electrode layer 22 may be a planar electrode. By adjusting the electric field strength between the pixel electrode and the common electrode, the liquid crystal composition in the sub-pixel may be transparent, or reflect blue light, red light, or green light, thereby realizing picture display.

[0155] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A liquid crystal composition, wherein: include: A mixture of rod-shaped monomer molecules, a chiral agent and a mixture of bent molecules, wherein the mixture of bent molecules includes a plurality of bent molecules; The bent molecule mixture includes: bent molecule dimers and / or bent molecule trimers, The rod-shaped monomer molecule mixture is selected from at least two of the following compounds: Wherein, J is C2, C5, C7 alkyl or C2-C6, C8 alkoxy; L is C1-C2 alkoxy, N is C2-C5 alkyl chain; when O is methyl, P is C3, C5 alkyl chain, when O is C2 methoxy, P is C2, C3, C5 alkyl chain; Q is C2, C3 alkyl chain; R is C1, C3, C5 alkoxy, S is C3, C5 alkyl chain; when T is methyl, U is C2, C3 alkyl chain, when T is C2 methoxy, U is C2, C3, C5 methyl chain; The chiral agent is selected from at least one of CB15, S811, R811, S1011, R1011, S2011, R2011, S5011 and R5011; The weight proportion of the bent molecular mixture in the liquid crystal composition is between 30% and 70%, the weight proportion of the rod-shaped monomer molecular mixture in the liquid crystal composition is between 30% and 70%, and the weight proportion of the chiral agent in the liquid crystal composition is between 0.5% and 10%.

2. The liquid crystal composition according to claim 1, wherein The bending elastic constant of the bent molecule is smaller than the twisting elastic constant.

3. The liquid crystal composition according to claim 1, wherein The bent molecular dimer has the following general formula I or general formula II: The bent molecular trimer has the following general formula III: Wherein, n is a natural number, 5≤n≤11; n' is 5 or 7; X, X' are selected from Formula IV and Formula V respectively, and Y, Y' are independently selected from Formula VI: Wherein, M1 and M2 are independently selected from hydrogen atoms and fluorine atoms, K is cyano, C2-C6 alkyl or C2-C6 alkoxy, and Z and Z' are independently selected from methylene and oxygen atoms.

4. The liquid crystal composition according to any one of claims 1 to 3, wherein The weight proportion of the bent molecular mixture in the liquid crystal composition is smaller than the weight proportion of the rod-shaped monomer molecular mixture in the liquid crystal composition.

5. The liquid crystal composition according to any one of claims 1 to 3, wherein The weight proportion of the bent molecular mixture in the liquid crystal composition is between 40% and 60%, the weight proportion of the rod-shaped monomer molecular mixture in the liquid crystal composition is between 40% and 55%, and the weight proportion of the chiral agent in the liquid crystal composition is between 0.5% and 5%.

6. The liquid crystal composition according to any one of claims 1 to 3, wherein The bent molecular mixture comprises: a first compound, a second compound, a third compound, a fourth compound, a fifth compound and a sixth compound, Wherein, the molecular formula of the first compound is: The molecular formula of the second compound is: The molecular formula of the third compound is: The molecular formula of the fourth compound is: The molecular formula of the fifth compound is: The molecular formula of the sixth compound is: Among them, the weight proportion of the first compound in the curved molecular mixture is between 55% and 65%, the weight proportion of the second compound in the curved molecular mixture is between 10% and 15%, the weight proportion of the third compound in the curved molecular mixture is between 8% and 13%, the weight proportion of the fourth compound in the curved molecular mixture is between 5% and 10%, the weight proportion of the fifth compound in the curved molecular mixture is between 3% and 7%, and the weight proportion of the sixth compound in the curved molecular mixture is between 2% and 6%.

7. The liquid crystal composition according to any one of claims 1 to 3, wherein The rod-shaped monomer molecule mixture includes a first monomer, a second monomer, a third monomer, a fourth monomer, a fifth monomer, a sixth monomer and a seventh monomer; The molecular formula of the first monomer is: The molecular formula of the second monomer is: The molecular formula of the third monomer is: The molecular formula of the fourth monomer is: The molecular formula of the fifth monomer is: The molecular formula of the sixth monomer is: The molecular formula of the seventh monomer is: Among them, the weight proportion of the first monomer in the rod-shaped monomer molecule mixture is between 55% and 65%, the weight proportion of the second monomer in the rod-shaped monomer molecule mixture is between 15% and 20%, the weight proportion of the third monomer in the rod-shaped monomer molecule mixture is between 5% and 15%, the weight proportion of the fourth monomer in the rod-shaped monomer molecule mixture is between 2% and 7%, the weight proportion of the fifth monomer in the rod-shaped monomer molecule mixture is between 2% and 5%, the weight proportion of the sixth monomer in the rod-shaped monomer molecule mixture is between 2% and 5%, and the weight proportion of the seventh monomer in the rod-shaped monomer molecule mixture is between 2% and 5%.

8. A method for preparing a liquid crystal composition, comprising: The rod-shaped monomer molecule mixture, the chiral agent and the bent molecule mixture are uniformly mixed in an organic solvent to obtain a liquid crystal mixture; wherein the bent molecule mixture includes a plurality of bent molecules; Distilling off the organic solvent in the liquid crystal mixture to obtain the liquid crystal composition; Wherein, the bent molecular mixture includes: bent molecular dimers and / or bent molecular trimers; The rod-shaped monomer molecule mixture is selected from at least two of the following compounds: Wherein, J is C2, C5, C7 alkyl or C2-C6, C8 alkoxy; L is C1-C2 alkoxy, N is C2-C5 alkyl chain; when O is methyl, P is C3, C5 alkyl chain, when O is C2 methoxy, P is C2, C3, C5 alkyl chain; Q is C2, C3 alkyl chain; R is C1, C3, C5 alkoxy, S is C3, C5 alkyl chain; when T is methyl, U is C2, C3 alkyl chain, when T is C2 methoxy, U is C2, C3, C5 methyl chain; The chiral agent is selected from at least one of CB15, S811, R811, S1011, R1011, S2011, R2011, S5011 and R5011; The weight proportion of the bent molecular mixture in the liquid crystal composition is between 30% and 70%, the weight proportion of the rod-shaped monomer molecular mixture in the liquid crystal composition is between 30% and 70%, and the weight proportion of the chiral agent in the liquid crystal composition is between 0.5% and 10%.

9. The preparation method according to claim 8, wherein: The organic solvent comprises at least one of acetone, methanol, ethanol, tetrahydrofuran, dichloromethane and chloroform.

10. A display panel, wherein: The invention comprises a first substrate and a second substrate which are arranged opposite to each other, and a liquid crystal layer located between the first substrate and the second substrate, wherein the liquid crystal layer comprises the liquid crystal composition according to any one of claims 1 to 9.

Images