Liquid crystal composition and use thereof

Abstract

The present invention relates to the technical field of liquid crystal display, and particularly relates to a liquid crystal composition and the use thereof. The composition comprises one or more compounds as represented by the following general formula I, one or more compounds as represented by the following general formula II, one or more compounds as represented by the following general formula III, and one or more compounds as represented by the following general formula IV. The liquid crystal composition of the present invention has a small change in the reflection center wavelength within a relatively wide temperature range, and can overcome the temperature dependence of existing bistable displays, avoid the chromatic aberration caused by the temperature change, improve the display effect, and broaden the use range thereof.

Description

A liquid crystal composition and its application

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202411590990.9, filed on November 8, 2024, entitled “A Liquid Crystal Composition and Its Application Therein,” the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to the field of liquid crystal display technology, and more specifically to a liquid crystal composition and its application. Background Technology

[0004] Currently, the application fields of liquid crystals have been significantly expanded to various display devices, electro-optical devices, electronic components, sensors, etc. Among them, bistable liquid crystal compositions, due to their bistable nature, can continuously display static images without power supply, and therefore can be used in e-books, electronic tags, display panels, etc., which require particularly low power consumption.

[0005] By adding chiral compounds to nematic liquid crystal compositions, cholesteric liquid crystals with twisted orientation can be made. Display elements made using cholesteric liquid crystals exhibit bistable stability, maintaining either a planar or focal conic state for extended periods without the need for an electric field. Switching is only achieved by applying a corresponding pulse voltage when the displayed content needs to be changed. Such liquid crystal compositions are also called bistable liquid crystal compositions. In the planar state, cholesteric liquid crystals reflect light of a specific wavelength, with the central wavelength of the reflected light satisfying Bragg's law of reflection: λ = nP, where n is the average refractive index and P is the helical pitch. The helical pitch of cholesteric liquid crystals has a significant impact on their optical properties; the characteristics of light transmission and selective light scattering are mainly determined by the helical pitch. However, the helical pitch of cholesteric liquid crystals exhibits significant temperature sensitivity, changing with temperature. This causes the central wavelength λ of the reflection of the bistable liquid crystal to change with temperature, resulting in a visual color shift. Summary of the Invention

[0006] This invention provides a liquid crystal composition and its applications to address the aforementioned problems in the prior art. The liquid crystal composition of this invention exhibits minimal change in the reflective center wavelength over a wide temperature range, overcoming the temperature dependence of existing bistable displays, avoiding color differences caused by temperature variations, improving display performance, and broadening its application range.

[0007] According to a first aspect of the present invention, a liquid crystal composition is provided, comprising one or more compounds represented by general formula I, one or more compounds represented by general formula II, one or more compounds represented by general formula III, and one or more compounds represented by general formula IV.

[0008] Among them, R1, R2, R 31 R 32 R 41 and R 42 Whether the two groups are the same or different, they each independently represent alkyl groups with 1 to 7 carbon atoms, alkoxy groups with 1 to 7 carbon atoms, or alkenyl groups with 2 to 7 carbon atoms;

[0009] L 11 L 21 and L 22 Whether the two are the same or different, they independently represent F, Cl, or H; L 31 and L 32 Whether they are the same or different, they each independently represent F, Cl, H or -CH3;

[0010] Ring A, ring B, and ring C may be the same or different, each independently representing 1,4-cyclohexylene or 1,4-phenylene;

[0011] Z1, Z2, and Z3 may be the same or different, and each independently represents a single bond or -COO-;

[0012] a, b, and c may be the same or different, each representing 0 or 1 independently; d and e may be the same or different, each representing 0, 1, or 2 independently.

[0013] The liquid crystal composition of the present invention comprises one or more compounds represented by general formula I, one or more compounds represented by general formula II, one or more compounds represented by general formula III, and one or more compounds represented by general formula IV. Through the synergistic effect between these compounds, the liquid crystal composition can exhibit a large refractive index anisotropy (Δn) and a large dielectric anisotropy (Δε). Simultaneously, the reflected light center wavelength of the liquid crystal composition of the present invention changes very little with temperature, effectively improving the situation where the color of existing bistable liquid crystals varies significantly with temperature.

[0014] Furthermore, the compound represented by general formula I is selected from one or more of the following formulas I-1 to I-4:

[0015] Wherein, R1 represents the same meaning as R1 in general formula I, preferably an alkyl group having 1 to 5 atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 5 carbon atoms.

[0016] The compound represented by general formula I has a large dielectric anisotropy (Δε), and the dielectric anisotropy of the liquid crystal composition can be effectively adjusted by adjusting its mass percentage; at the same time, the compound represented by general formula I in this invention has the function of enhancing the stability of the liquid crystal phase in the focal conic and planar states.

[0017] Furthermore, the compound represented by general formula I accounts for 17% to 37% of the mass percentage of the liquid crystal composition, preferably 18% to 32%, and more preferably 20% to 30%.

[0018] In some specific embodiments, the compound represented by general formula I accounts for 20% to 26% of the mass percentage of the liquid crystal composition.

[0019] Furthermore, the compound represented by general formula II is selected from one or more of formulas II-1 to II-4:

[0020] Wherein, R2 represents the same meaning as R2 in general formula II, preferably an alkyl group having 1 to 5 atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 5 carbon atoms.

[0021] The compound represented by general formula II has a large dielectric anisotropy and a high refractive index anisotropy (Δn). By adjusting its mass percentage, the dielectric anisotropy and refractive index anisotropy of the liquid crystal composition can be adjusted simultaneously.

[0022] Furthermore, the compound represented by general formula II accounts for 24% to 46% of the mass percentage of the liquid crystal composition, preferably 29% to 43%, and more preferably 31% to 41%.

[0023] In some specific embodiments, the compound represented by general formula II accounts for 34% to 39% of the mass percentage of the liquid crystal composition.

[0024] Furthermore, the compound represented by general formula III is selected from one or more of formulas III-1 to III-5:

[0025] Among them, R 31 and R 32 Represents R in general formula III 31 and R 32 With the same meaning, alkyl groups having 1 to 5 atoms, alkoxy groups having 1 to 5 carbon atoms, or alkenyl groups having 2 to 5 carbon atoms are preferred.

[0026] The compound represented by general formula III has a high refractive index anisotropy. By adjusting its mass percentage, the refractive index anisotropy of the liquid crystal composition can be effectively adjusted.

[0027] Furthermore, the compound represented by general formula III accounts for 22% to 44% of the mass percentage of the liquid crystal composition, preferably 24% to 42%, and more preferably 26% to 40%.

[0028] In some specific embodiments, the compound represented by general formula III accounts for 27% to 37% of the mass percentage of the liquid crystal composition.

[0029] Furthermore, the compound represented by general formula IV is selected from one or more of formulas IV-1 to IV-3:

[0030] Among them, R 41 and R 42 Represents R in general formula IV 41 and R 42 With the same meaning, alkyl groups having 1 to 6 atoms, alkoxy groups having 1 to 6 carbon atoms, or alkenyl groups having 2 to 6 carbon atoms are preferred.

[0031] The compound represented by general formula IV is a helical chiral agent, which has the ability to twist helically. Adjusting its mass percentage can make the liquid crystal composition of the present invention exhibit different pitches, thereby reflecting colors of different wavelengths.

[0032] Further, the compound represented by general formula IV accounts for 1% to 10% of the mass percentage of the liquid crystal composition, preferably 1% to 8%, and more preferably 1% to 6%. In some specific embodiments, the compound represented by general formula IV accounts for 3% to 5% of the mass percentage of the liquid crystal composition.

[0033] Furthermore, the liquid crystal composition further includes one or more compounds represented by the following general formula V:

[0034] R5 represents an alkyl group with 1 to 7 carbon atoms, an alkoxy group with 1 to 7 carbon atoms, or an alkenyl group with 2 to 7 carbon atoms.

[0035] L 51 and L 52 Whether they are the same or different, they each independently represent F, Cl, or H;

[0036] f and g may be the same or different, each independently representing 1 or 2, and not both being 2 at the same time.

[0037] Preferably, the compound represented by the general formula V is selected from one or more of the following formulas V-1 to V-9:

[0038] R5 represents an alkoxy group with 1 to 5 carbon atoms or an alkenyl group with 2 to 5 carbon atoms.

[0039] The compounds represented by general formula V have moderate dielectric anisotropy and moderate refractive index anisotropy. When added to the liquid crystal composition described in this invention, they can improve the low-temperature stability of the liquid crystal composition.

[0040] In some specific embodiments, the compound represented by general formula V accounts for 5 to 10% of the mass percentage of the liquid crystal composition.

[0041] Furthermore, the liquid crystal composition further includes one or more compounds represented by the following general formula VI:

[0042] Where R 61 and R 62 Whether the two groups are the same or different, they each independently represent alkyl groups with 1 to 7 carbon atoms, alkoxy groups with 1 to 7 carbon atoms, or alkenyl groups with 2 to 7 carbon atoms;

[0043] Ring D and ring E may be the same or different, each independently representing 1,4-cyclohexylene or 1,4-phenylene in which hydrogen atoms can be substituted by fluorine atoms;

[0044] Z4 represents a single bond or -COO-;

[0045] h represents 1, 2 or 3, and when h is not 1, rings D and Z4 can be the same or different.

[0046] Preferably, the compound represented by general formula VI is selected from one or more of formulas VI-1 to VI-12:

[0047] Where R 61 and R 62 Whether the groups are the same or different, they each independently represent alkyl groups with 1 to 5 atoms, alkoxy groups with 1 to 5 carbon atoms, or alkenyl groups with 2 to 5 carbon atoms.

[0048] The compound represented by general formula VI has moderate refractive index anisotropy. When added to the liquid crystal composition described in this invention, it can effectively adjust the clearing point of the liquid crystal and improve the low-temperature stability of the liquid crystal composition.

[0049] In some specific embodiments, the compound represented by general formula VI accounts for 5 to 10% of the mass percentage of the liquid crystal composition, preferably 6 to 8%, and more preferably 6.5 to 7%.

[0050] Compared to traditional bistable liquid crystals, extensive research on the photoelectric and physical properties of existing liquid crystal compounds has revealed a synergistic effect when four liquid crystal compounds of general formulas I to IV are combined in specific ratios. The resulting liquid crystal compositions exhibit excellent temperature stability of the primary reflection wavelength, specifically, the variation in primary reflection wavelength does not exceed 5 nm within the temperature range of 0℃ to 50℃. This is particularly suitable for cholesteric bistable displays and can improve the operating temperature range of existing bistable displays.

[0051] Furthermore, in order to improve the stability of the liquid crystal composition to heat and light, especially ultraviolet light, the liquid crystal composition further includes one or more of ultraviolet absorbers, hindered amine light stabilizers, and hindered phenolic antioxidants; preferably, the ultraviolet absorber is selected from one or more of benzotriazoles, benzophenones, triazines, and benzoic acid esters.

[0052] There are no particular limitations on the preparation method of the liquid crystal composition of the present invention. It can be produced by mixing two or more compounds using conventional methods, such as by mixing different components and dissolving them together at high temperature. In this case, the liquid crystal composition is dissolved in a solvent used for the compound and mixed, and then the solvent is distilled off under reduced pressure. Alternatively, the liquid crystal composition of the present invention can be prepared by conventional methods, such as dissolving a component with a smaller content in a major component with a larger content at a higher temperature, or dissolving each component in an organic solvent, such as acetone, chloroform, or methanol, and then mixing the solutions to remove the solvent.

[0053] All compounds involved in this invention are known compounds, commercially available, or provided by Beijing Bayi Space-Time Liquid Crystal Technology Co., Ltd.

[0054] According to a second aspect of the present invention, the present invention also provides the use of the above-described liquid crystal composition in a liquid crystal display element or liquid crystal display device.

[0055] The liquid crystal composition provided by the present invention comprises one or more compounds represented by general formula I, one or more compounds represented by general formula II, one or more compounds represented by general formula III, and one or more compounds represented by general formula IV. It exhibits minimal variation in the reflection center wavelength over a wide temperature range, thereby overcoming the temperature dependence of existing bistable displays, avoiding color differences caused by temperature changes, improving display performance, and broadening its application range. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] Unless otherwise stated, percentages in this invention are weight percentages; temperature is in degrees Celsius; Δn represents optical anisotropy (25°C); ε ∥ and ε ⊥ λ_25, λ_0, and λ_50 represent the parallel dielectric constant and the perpendicular dielectric constant (25℃, 1000Hz), respectively; Δε represents the dielectric anisotropy (25℃, 1000Hz); Tni represents the clearing point of the liquid crystal composition (℃); λ_25, λ_0, and λ_50 represent the primary reflection wavelength at 25℃, 0℃, and 50℃, respectively.

[0058] In the following embodiments, the group structures in the liquid crystal compounds are represented by the codes shown in Table 1.

[0059] Table 1: Group structure codes of liquid crystal compounds

[0060] Take the following compound structure as an example:

[0061] Represented as: 3CPEUaN

[0062] Represented as: 4PMPN

[0063] In the following embodiments, the liquid crystal composition is prepared by a thermal dissolution method, including the following steps: weighing the liquid crystal compound by weight percentage using a balance, wherein there is no specific requirement for the order of weighing and adding, usually weighing and mixing in order of the melting point of the liquid crystal compound from high to low, heating and stirring at 60 to 100°C to make the components melt evenly, then filtering, rotary evaporating, and finally encapsulating to obtain the target sample.

[0064] In the following embodiments, the weight percentage of each component in the liquid crystal composition and the performance parameters of the liquid crystal composition are shown in the following tables.

[0065] In the following embodiments, all components involved are known liquid crystal compounds and can be provided by Beijing Bayi Space Technology Co., Ltd.

[0066] Table 2

[0067] Table 3

[0068] Table 4

[0069] Table 5

[0070] Table 6

[0071] Table 7

[0072] Table 8

[0073] Table 9

[0074] Table 10

[0075] In Comparative Example 2, S5011 and S811 are chiral agents with the following specific structures:

[0076] The performance parameters of the liquid crystal compositions obtained in Examples 1 to 7 and Comparative Examples 1 and 2 are summarized and compared, as shown in Table 11.

[0077] Table 11

[0078] As can be seen from Table 11, the liquid crystal composition of the present invention exhibits excellent wavelength-temperature stability, with minimal change in the reflection center wavelength over a wide temperature range. Further comparison shows that, compared to Comparative Examples 1 and 2, with similar physical properties (Tni, Δn, Δε) and the same primary reflection wavelength at room temperature of 25 degrees Celsius, the liquid crystal composition provided in the embodiments of the present invention exhibits even smaller wavelength variation within the temperature range of 0°C to 50°C.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid crystal composition, characterized in that, It comprises one or more compounds represented by general formula I, one or more compounds represented by general formula II, one or more compounds represented by general formula III, and one or more compounds represented by general formula IV. Among them, R1, R2, R 31 R 32 R 41 and R 42 Whether the two groups are the same or different, they each independently represent alkyl groups with 1 to 7 carbon atoms, alkoxy groups with 1 to 7 carbon atoms, or alkenyl groups with 2 to 7 carbon atoms; L 11 L 21 and L 22 Whether the two are the same or different, they independently represent F, Cl, or H; L 31 and L 32 Whether they are the same or different, they each independently represent F, Cl, H or -CH3; Ring A, ring B, and ring C may be the same or different, each independently representing 1,4-cyclohexylene or 1,4-phenylene; Z1, Z2, and Z3 may be the same or different, and each independently represents a single bond or -COO-; a, b, and c may be the same or different, each representing 0 or 1 independently; d and e may be the same or different, each representing 0, 1, or 2 independently.

2. The liquid crystal composition according to claim 1, characterized in that, The compound represented by general formula I is selected from one or more of the following formulas I-1 to I-4: Wherein, R1 represents the same meaning as R1 in general formula I, preferably an alkyl group having 1 to 5 atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 5 carbon atoms.

3. The liquid crystal composition according to claim 1 or 2, characterized in that, The compound represented by general formula I accounts for 17% to 37% of the mass percentage of the liquid crystal composition, preferably 18% to 32%, and more preferably 20% to 30%.

4. The liquid crystal composition according to claim 1, characterized in that, The compound represented by general formula II is selected from one or more of formulas II-1 to II-4: Wherein, R2 represents the same meaning as R2 in general formula II, preferably an alkyl group having 1 to 5 atoms, an alkoxy group having 1 to 5 carbon atoms, or an alkenyl group having 2 to 5 carbon atoms.

5. The liquid crystal composition according to claim 1 or 4, characterized in that, The compound represented by general formula II accounts for 24% to 46% of the mass percentage of the liquid crystal composition, preferably 29% to 43%, and more preferably 31% to 41%.

6. The liquid crystal composition according to claim 1, characterized in that, The compound represented by general formula III is selected from one or more of formulas III-1 to III-5: Among them, R 31 and R 32 Represents R in general formula III 31 and R 32 With the same meaning, alkyl groups having 1 to 5 atoms, alkoxy groups having 1 to 5 carbon atoms, or alkenyl groups having 2 to 5 carbon atoms are preferred; And / or, the compound represented by general formula III accounts for 22% to 44% of the mass percentage of the liquid crystal composition, preferably 24% to 42%, more preferably 26% to 40%.

7. The liquid crystal composition according to claim 1, characterized in that, The compound represented by general formula IV is selected from one or more of formulas IV-1 to IV-3: Among them, R 41 and R 42 Represents R in general formula IV 41 and R 42 With the same meaning, alkyl groups having 1 to 6 atoms, alkoxy groups having 1 to 6 carbon atoms, or alkenyl groups having 2 to 6 carbon atoms are preferred; And / or, the compound represented by the general formula IV accounts for 1% to 10% of the mass percentage of the liquid crystal composition, preferably 1% to 8%, more preferably 1% to 6%.

8. The liquid crystal composition according to claim 1, characterized in that, The liquid crystal composition further includes one or more compounds represented by the following general formula V: R5 represents an alkyl group with 1 to 7 carbon atoms, an alkoxy group with 1 to 7 carbon atoms, or an alkenyl group with 2 to 7 carbon atoms. L 51 and L 52 Whether they are the same or different, they each independently represent F, Cl, or H; f and g may be the same or different, each independently representing 1 or 2, and not both being 2 at the same time; Preferably, the compound represented by the general formula V is selected from one or more of the following formulas V-1 to V-9: R5 represents an alkoxy group with 1 to 5 carbon atoms or an alkenyl group with 2 to 5 carbon atoms.

9. The liquid crystal composition according to claim 1, characterized in that, The liquid crystal composition further includes one or more compounds represented by the following general formula VI: Where R 61 and R 62 Whether the two groups are the same or different, they each independently represent alkyl groups with 1 to 7 carbon atoms, alkoxy groups with 1 to 7 carbon atoms, or alkenyl groups with 2 to 7 carbon atoms; Ring D and ring E may be the same or different, each independently representing 1,4-cyclohexylene or 1,4-phenylene in which hydrogen atoms can be substituted by fluorine atoms; Z4 represents a single bond or -COO-; h represents 1, 2 or 3, and when h is not 1, rings D and Z4 can be the same or different; Preferably, the compound represented by general formula VI is selected from one or more of formulas VI-1 to VI-12: Where R 61 and R 62 Whether the groups are the same or different, they each independently represent alkyl groups with 1 to 5 atoms, alkoxy groups with 1 to 5 carbon atoms, or alkenyl groups with 2 to 5 carbon atoms.

10. The use of the liquid crystal composition according to any one of claims 1-9 in a liquid crystal display element or liquid crystal display device.

Images