A dichroic dye, a liquid crystal composition containing the same, and applications thereof

Abstract

The present invention provides a dichroic dye, a liquid crystal composition containing the dichroic dye, and its application. The dichroic dye has the structure shown in Formula VII below, is red, has a maximum absorption wavelength range of 580 nm to 680 nm, exhibits high photostability, a high dichroic ratio, and is highly compatible with liquid crystal materials. The liquid crystal composition containing the dichroic dye of Formula VII appears colorless and has high light transmittance when powered on, but displays red and has low light transmittance when powered off. It retains its red color even after prolonged exposure to light and exhibits high photostability. The composition can be used to manufacture products such as dimming films, dimming glass, liquid crystal display elements, or liquid crystal displays. #imgabs0#

Description

Technical Field

[0001] The present invention relates to the technical field of display materials, and in particular to a dichroic dye, a liquid crystal composition containing the dichroic dye, and applications of the dichroic dye in dimming films, dimming glasses, liquid crystal display elements, or liquid crystal displays. Background Art

[0002] Dichroism can be achieved by utilizing the intermolecular interactions of organic dye molecules. Dichroism refers to the property of a substance that absorbs two different refracted beams (o-light and e-light) with significant differences. In other words, dichroism refers to the dependence of a substance's absorption coefficient on the polarization state of the incident light.

[0003] With the continuous research on dichroic dyes, they are widely used in fields such as dimming films, dimming glass, and liquid crystal displays. For example, when the external light is very strong, it needs to be attenuated, polarized, or blocked. Such functions can be achieved by dimming films or dimming glass.

[0004] The main components of the dimming film are dichroic dyes and liquid crystal materials. At present, typical dichroic dyes are mainly anthraquinone dyes and azo dyes. Among them, anthraquinone dyes have good light stability, but the disc-like structure of anthraquinone causes the molecular structure to decrease linearly, resulting in relatively low solubility and dichroicity. Azo dyes have a large dichroic ratio, but poor light stability. When the dimming film containing azo dyes is exposed to ultraviolet light for a long time, it will cause the dichroic dye to age and deteriorate rapidly, fade, or even lose its dichroic properties. Therefore, existing dichroic dyes cannot achieve the characteristics of high dichroic ratio, high light stability and high solubility at the same time, which seriously limits the application of dichroic dyes.

[0005] The development of dichroic dyes with high dichroic ratio, high photostability and high solubility is an urgent problem to be solved. Summary of the Invention

[0006] In light of this, the present invention provides a dichroic dye, a liquid crystal composition containing the same, and its application. The dichroic dye has a high dichroic ratio, high photostability, high solubility, and high compatibility with liquid crystal materials. The liquid crystal composition containing the dichroic dye can be used to manufacture products such as dimming films, dimming glasses, liquid crystal display elements, or liquid crystal displays.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0008] A dichroic dye having a structure shown in formula VII,

[0009]

[0010] wherein m and n are each independently selected from 0 or 1;

[0011] R1 and R2 are each independently selected from a C1-C15 straight or branched alkyl group which is unsubstituted or at least one H is substituted by F, a C1-C15 straight or branched alkoxy group which is unsubstituted or at least one H is substituted by F, a C2-C10 straight or branched alkenyl group which is unsubstituted or at least one H is substituted by F, a C3-C10 straight or branched alkenyloxy group which is unsubstituted or at least one H is substituted by F, or any one or more unconnected -CH2- groups in any of the above groups are each independently substituted by -O-, -S-, cyclopropylene, cyclobutylene or cyclopentylene;

[0012] Each independently selected from a C6-C10 arylene ring group, a C3-C6 aliphatic ring group, a C10-C15 condensed ring group, or any one -CH2- in any group thereof is replaced by -O- or -S-, or any one H in any group thereof is replaced by one or more L;

[0013] L is selected from F, C1-C10 straight or branched alkyl which is unsubstituted or at least one H is substituted by F, C2-C10 straight or branched alkenyl which is unsubstituted or at least one H is substituted by F, C3-C10 straight or branched alkenyloxy which is unsubstituted or at least one H is substituted by F, or any one or more unconnected -CH2- in any of the above groups are independently substituted by -O-, -S-, cyclopropylene, cyclobutylene or cyclopentylene;

[0014] Z1, Z2, Z3, and Z4 are each independently selected from a single bond, -C2H4-, -CH=CH-, -C≡C-, -COO-, -OOC-, -CH2O-, -OCH2-, -CF2O-, or -OCF2-.

[0015] Optionally, the compound represented by formula VII is selected from at least one of the structures represented by formula VIIA below,

[0016]

[0017] wherein m and n are each independently selected from 0 or 1; preferably, m and n are the same and selected from 0 or 1;

[0018] R1 and R2 are each independently selected from a C1-C12 linear or branched alkyl group, or a C1-C12 linear or branched alkoxy group; preferably, R1 and R2 are the same and selected from a C1-C12 linear or branched alkyl group, or a C1-C12 linear or branched alkoxy group;

[0019] Each is independently selected from 1,4-phenylene, 1,4-cyclohexylene, or 1,4-phenylene or 1,4-cyclohexenylene in which 1-4 H are substituted by C1-C4 straight-chain alkyl; preferably, The same is selected from 1,4-phenylene, or 1,4-phenylene in which 1 to 4 H are substituted by C1-C4 straight-chain alkyl.

[0020] Optionally, the compound represented by formula VIIA is selected from at least one of the structures represented by formula VIIa to formula VIId below,

[0021]

[0022] wherein R1 and R2 are each independently selected from a C1-C12 linear or branched alkyl group, or a C1-C12 linear or branched alkoxy group; preferably, R1 and R2 are the same and selected from a C1-C12 linear or branched alkyl group, or a C1-C12 linear or branched alkoxy group;

[0023] Each is independently selected from 1,4-phenylene, 1,4-cyclohexylene, or 1,4-phenylene or 1,4-cyclohexenylene in which 1-4 H are substituted by C1-C4 straight-chain alkyl; preferably, The same is selected from 1,4-phenylene, or 1,4-phenylene in which 1 to 4 H are substituted by C1-C4 straight-chain alkyl.

[0024] Optionally, the compound represented by formula VIIA is selected from at least one of the structures represented by formula VII1 to formula VII11 below,

[0025]

[0026]

[0027] The present invention also provides a method for preparing the above-mentioned dichroic dyes VII1-VII6, and the reaction formula is as follows:

[0028]

[0029] wherein R1 is selected from -C6H 13 、-C9H 19 、-C 10 H 21 、-OC6H 13 、-OC9H 19 or -OC 10 H 21 ,

[0030] The preparation method of dichroic dyes VII1-VII6 comprises the following steps:

[0031] Compound 1 is subjected to a Grignard reaction to obtain a Grignard reagent, which is reacted with trimethyl borate to obtain compound 2; compound 2 and compound 3 are subjected to a coupling reaction to obtain compounds VII1-VII6.

[0032] The present invention also provides a method for preparing the dichroic dyes VII7-VII11, and the reaction formula is as follows:

[0033]

[0034] wherein R1 is selected from -C9H 19 、-C 10 H 21 、-OC6H 13 or n-dodecyl group connected to a benzene ring at position 3

[0035] Each is independently selected from 1,4-phenylene, or 1,4-phenylene in which 1-2 H are substituted by C1-C2 alkyl;

[0036] The preparation method of dichroic dyes VII7-VII11 comprises the following steps:

[0037] Compound 5 reacts with butyl lithium to obtain an organolithium reagent, which reacts with trimethyl borate to obtain compound 6, and compound 6 is coupled with compound 3 to obtain compounds VII7-VII11.

[0038] The present invention also provides a liquid crystal composition comprising at least one of the above-mentioned dichroic dyes and at least one positive dielectric anisotropic liquid crystal compound.

[0039] Optionally, the at least one positive dielectric anisotropic liquid crystal compound comprises at least one of the structures shown in Formula I,

[0040]

[0041] wherein R3 is selected from C1-C10 straight or branched alkyl, C1-C10 straight or branched alkoxy, C2-C10 straight or branched alkenyl, C3-C10 straight or branched alkenyloxy, or any one or more unconnected -CH2- groups in any of these groups are independently substituted with cyclopropylene, cyclobutylene or cyclopentylene;

[0042] R4 is selected from F, a C1-C5 straight chain or branched alkyl group in which at least one H is substituted by F, a C1-C5 straight chain or branched alkoxy group in which at least one H is substituted by F, a C2-C5 straight chain or branched alkenyl group in which at least one H is substituted by F, or a C3-C8 straight chain or branched alkenyloxy group in which at least one H is substituted by F;

[0043] Z5 is selected from a single bond, -CH2CH2- or -CF2O-;

[0044] r is selected from 1, 2, 3 or 4. When r is selected from 2, 3, 4, each Can be the same or different;

[0045] Each independently selected from

[0046] Optionally, the compound represented by formula I is selected from at least one of the structures represented by formula IA to formula IC.

[0047]

[0048] Wherein, in Formula IA, r is 2 or 3;

[0049] In formula IC, r is selected from 1, 2 or 3, and R4 is selected from F, OCF3 or CF3;

[0050] In Formula IB, r is selected from 1, 2, 3 or 4, and R4 is selected from F, a C1-C5 straight chain or branched alkyl group in which at least one H is substituted by F, a C1-C5 straight chain or branched alkoxy group in which at least one H is substituted by F, a C2-C5 straight chain or branched alkenyl group in which at least one H is substituted by F, or a C3-C8 straight chain or branched alkenyloxy group in which at least one H is substituted by F;

[0051] R3 is selected from C1-C10 straight or branched alkyl, C1-C10 straight or branched alkoxy, C2-C10 straight or branched alkenyl, C3-C10 straight or branched alkenyloxy, or any one or more unconnected -CH2- in any of the above groups are independently substituted by cyclopropylene, cyclobutylene or cyclopentylene;

[0052] When r is selected from 2, 3 or 4, each Can be the same or different;

[0053] Each independently selected from

[0054] Optionally, the compound represented by Formula I is selected from at least one of the structures represented by Formula I1 to Formula I32,

[0055]

[0056]

[0057]

[0058] Among them, in the compounds represented by Formula I1 to Formula I23, R3 is selected from C1-C10 straight chain or branched alkyl, or C2-C10 straight chain or branched alkenyl; in the compounds represented by Formula I24 to Formula I32, R3 is selected from C1-C10 straight chain or branched alkyl in which at least one -CH2- is substituted by cyclopentylene or cyclopropylene.

[0059] Optionally, the at least one positive dielectric anisotropic liquid crystal compound comprises at least one of the structures shown in Formula II,

[0060]

[0061] wherein R5 is selected from a C1-C10 linear or branched alkyl group, or a C1-C10 linear or branched alkoxy group; R6 is CN;

[0062] Each independently selected from Z6 and Z7 are each independently selected from a single bond or -COO-;

[0063] s is selected from 0 or 1.

[0064] Optionally, the compound represented by formula II is selected from at least one of the structures represented by formula IIA to formula IIC.

[0065]

[0066] Wherein, R5 is selected from C1-C10 linear or branched alkyl, or C1-C10 linear or branched alkoxy;

[0067] Each independently selected from Optionally, the compound represented by formula II is selected from at least one of the structures represented by formula II1 to formula II6.

[0068]

[0069]

[0070] Wherein, R5 is selected from C1-C10 linear or branched alkyl groups.

[0071] Optionally, the liquid crystal composition further comprises at least one of the structures shown in Formula III,

[0072]

[0073] wherein R7 and R8 are each independently selected from a C1-C10 linear or branched alkyl group, a C1-C10 linear or branched alkoxy group, an unsubstituted or at least C2-C10 linear or branched alkenyl group, or a C3-C10 linear or branched alkenyloxy group;

[0074] Each independently selected from

[0075] t is selected from 1 or 2. When t is 2, the two Same or different.

[0076] Optionally, the compound represented by formula III is selected from at least one of the structures represented by formula III1 to formula III25.

[0077]

[0078]

[0079]

[0080] Optionally, the total content of the dichroic dye in the liquid crystal composition is 0.5%-2% by mass.

[0081] Optionally, based on mass percentage, the total content of the compound represented by formula I in the liquid crystal composition is 1%-40%, the total content of the compound represented by formula II is 1%-40%, and the total content of the compound represented by formula III is 30%-76%.

[0082] The aforementioned C1-C10 straight-chain or branched alkyl group can be selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or isopentyl, etc.

[0083] The aforementioned C1-C15 straight or branched alkyl group, C1-C12 straight or branched alkyl group may be selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, -C6H 13 、-C9H 19 、-C 10 H 21 、-C 12 H 25 or -C8H 17 wait.

[0084] The aforementioned C1-C10 straight-chain or branched alkoxy group may be selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy or isopentyloxy.

[0085] The aforementioned C1-C15 straight or branched alkoxy, C1-C12 straight or branched alkoxy can be selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, isopentyl, -OC6H 13 、-OC9H 19 、-OC 10 H 21 or -OC8H17 wait.

[0086] The aforementioned C2-C10 straight-chain or branched alkenyl group may be selected from vinyl, 1-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl or 4-pentenyl.

[0087] The aforementioned C3-C8 straight-chain or branched alkenyloxy group can be selected from vinyl methoxy (CH2=CO-CH2-), vinyl ethoxy (CH2=CO-CH2CH2-), methoxyethylene (-CH=C-OCH3) or ethoxyethylene (-CH=C-OCH2CH3) and the like.

[0088] The group obtained by replacing one or more non-adjacent -CH2- in the aforementioned C1-C15 straight or branched alkyl group which is unsubstituted or at least one H is substituted by F, the C1-C15 straight or branched alkoxy group which is unsubstituted or at least one H is substituted by F, the C2-C10 straight or branched alkenyl group which is unsubstituted or at least one H is substituted by F, or the C3-C10 straight or branched alkenoxy group which is unsubstituted or at least one H is substituted by F with a cyclopropylene or cyclopentylene group may be selected from cyclopropyl, cyclopentyl, methylcyclopropylene, ethylcyclopropylene, propylcyclopropylene, isopropylcyclopropylene, n-butylcyclopropylene, isobutylcyclopropylene, tert-butylcyclopropylene, methylcyclopentylene, ethylcyclopentylene, propylcyclopentylene, isopropylcyclopentylene, n-butylcyclopentylene or isobutylcyclopentylene;

[0089] The aforementioned C6-C10 arylene ring group may be selected from 1,4-phenylene or 1,5-naphthylene;

[0090] The aforementioned C3-C6 aliphatic cyclic group can be selected from 1,2-cyclopropylene, 1,3-cyclobutylene, 1,3-cyclopentylene, 1,4-cyclohexylene and the like.

[0091] The present invention also provides a method for preparing the above-mentioned liquid crystal composition, comprising the following steps: placing the raw materials in a stainless steel beaker and heating and melting them; after the raw materials are completely melted, stirring them evenly and cooling them to room temperature to obtain the liquid crystal composition;

[0092] Alternatively, the raw materials except the dichroic dye are placed in a stainless steel beaker and heated to melt. After the raw materials in the stainless steel beaker are completely melted, they are stirred evenly, and then the dichroic dye is added. The mixture is heated again until the dichroic dye is completely melted and mixed evenly, and then cooled to room temperature to obtain a liquid crystal composition.

[0093] The present invention also provides a dimming film, which comprises at least one of the above-mentioned dichroic dyes or at least one of the above-mentioned liquid crystal compositions.

[0094] The present invention also provides a dimming glass, which comprises at least one of the above-mentioned dichroic dyes or at least one of the above-mentioned liquid crystal compositions.

[0095] The present invention also provides a liquid crystal display element, comprising at least one of the above-mentioned dichroic dyes or at least one of the above-mentioned liquid crystal compositions; preferably, the liquid crystal display element is a guest-host liquid crystal display element.

[0096] The present invention also provides a liquid crystal display device, comprising at least one of the above-mentioned dichroic dyes or at least one of the above-mentioned liquid crystal compositions; preferably, the liquid crystal display is a guest-host liquid crystal display.

[0097] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0098] 1. The dichroic dye provided by the present invention is red, with a maximum absorption wavelength range of 580nm-680nm. It has the characteristics of high photostability, high dichroic ratio, and high compatibility with liquid crystal materials (the liquid crystal composition containing the dichroic dye does not precipitate after being placed in a glove box at -20°C for 240 hours).

[0099] 2. The liquid crystal composition provided by the present invention containing the dichroic dye represented by formula VII is colorless when powered on and has high light transmittance (visible light transmittance reaches 68%-71% under 6V power conditions). It displays red after power is turned off and has low light transmittance (the light transmittance is 35%-37% after irradiation under 365nm ultraviolet light environment for 240 hours, and the change in light transmittance does not exceed 6%). It can still maintain red color after long-term illumination and has high light stability. It can be used to manufacture products such as dimming films, dimming glasses, liquid crystal display elements or liquid crystal displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 It is the MS mass spectrum of the compound represented by formula VII3. DETAILED DESCRIPTION

[0101] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0102] Unless otherwise specified, the methods involved in the following examples and comparative examples are conventional methods. The raw materials used can be obtained from public commercial channels unless otherwise specified. The percentages are by mass and the temperatures are in degrees Celsius (°C).

[0103] 1. Performance test conditions and the specific meaning of corresponding symbols

[0104] Cp represents the clearing point of liquid crystal (℃), measured by DSC quantitative method;

[0105] Δn represents optical anisotropy, Δn=n e -n o , where n o is the refractive index of ordinary light, n e The refractive index of extraordinary light was measured at 25±2°C, 589 nm, and an Abbe refractometer.

[0106] Δε represents dielectric anisotropy, Δε=ε ∥ -ε ⊥ , where ε ∥ is the dielectric constant parallel to the molecular axis, ε ⊥ is the dielectric constant perpendicular to the molecular axis, tested at 25±0.5°C, 20 μm antiparallel cell, INSTEC: ALCT-CUST-4C;

[0107] K 11 is the splay elastic constant, K 33 is the bending elastic constant, the test conditions are: 25±2℃, INSTEC:ALCT-CUST-4C, 20 μm antiparallel cell;

[0108] γ1 represents the rotational viscosity (mPa·s), the test conditions are 25±0.5℃, 20 μm antiparallel cell, INSTEC: ALCT-CUST-4C test;

[0109] T represents light transmittance, the test equipment is DMS501, the test conditions are 25±0.5℃, and the test box is a 3.3μm IPS test box.

[0110] 2. Preparation Methods of the Precursor and Liquid Crystal Compositions in Each Example and Comparative Example

[0111] Melting the dichroic dye with the remaining raw materials, or melting and mixing the remaining raw materials except the dichroic dye before adding the dichroic dye, has no effect on the properties of the liquid crystal composition. However, for ease of comparison, the liquid crystal compositions in the following examples and comparative examples were prepared using the following method:

[0112] The remaining raw materials except the dichroic dye are weighed according to a certain ratio and placed in a stainless steel beaker, which is then placed on a magnetic stirring apparatus for heating and melting. After the raw materials in the stainless steel beaker are completely melted, a magnetic rotor is added to the stainless steel beaker, and the mixture is stirred evenly. Half of the mixture is taken out and cooled to room temperature to obtain a matrix. At the same time, the dichroic dye is added to the remaining half. After the added dichroic dye is completely melted and mixed evenly, it is cooled to room temperature to obtain a liquid crystal composition.

[0113] The matrix was subjected to the above method to measure Cp, Δn, Δε, K 11 , K 33 The liquid crystal composition was subjected to performance tests such as γ and γ1, and the photoelectric performance, light stability and dye solubility of the liquid crystal composition was tested.

[0114] 3. Code Abbreviations

[0115] The structures of the raw materials in each embodiment and comparative example are represented by codes, and the code representation method of the ring structure, end group, and connecting group is shown in Table 1-2 below.

[0116] Table 1 Corresponding codes of ring structure

[0117]

[0118] Table 2 Corresponding codes of terminal groups and linking groups

[0119]

[0120] For example:

[0121] Its code is CC-3-V;

[0122] Its code is CC-3-V1;

[0123] Its code is PP-1-2V;

[0124] Its code is CPP-1V-2;

[0125] Its code is PGP-3-2;

[0126] Its code is CCU-3-F;

[0127] Its code is PGU-3-F;

[0128] Its code is CCPU-3-F;

[0129] Its code is CPGU-3-OT;

[0130] Its code is DGUQU-4-F;

[0131] Its code is PGUQU-3-F;

[0132] Its code is PPGU-Cp-F.

[0133] 4. Preparation of dichroic dyes and liquid crystal compositions and related performance testing

[0134] Example 1

[0135] This embodiment provides a dichroic dye, the structural formula of which is shown in Formula VII1, and the synthesis route is as follows:

[0136]

[0137] The specific synthesis steps are as follows:

[0138] To a 2L three-necked flask, 35g (0.2mol) of p-bromophenol, 33g (0.2mol) of bromohexane, 30g (0.2mol) of potassium carbonate and 600mL of DMF were added, stirred and dissolved, and reacted at 90°C for 4 hours until the reaction was completed. 1000mL of water and 200mL of ethyl acetate were added, stirred and allowed to stand for separation, and the separated aqueous phase was extracted twice with ethyl acetate, each time with 200mL. The organic phases were combined and washed with water until neutral, and the solvent was spin-dried to obtain 46g of an oily liquid (Compound 1) with an HPLC purity of 99.1% and a yield of 90%.

[0139] Add 200 mL of anhydrous tetrahydrofuran, 3 g of magnesium chips and 5 g (0.02 mol) of compound 1 to a 1 L three-necked flask, heat under reflux with stirring; after initiation, add a solution of compound 1 in anhydrous tetrahydrofuran (20 g (0.08 mol) of compound 1 dissolved in 100 mL of anhydrous tetrahydrofuran) dropwise under reflux for 1 hour; after the addition is completed, continue to reflux with stirring for 2 hours until the reaction is completed, cool to -30 ° C, and then add 11 g ( The reaction mixture was added to a 5-well plate of 4-nitropropane-2-nitropropane (5-nitropropane-2-nitropropane) and trimethyl borate (0.1 mol). After the addition was completed for 0.5 h, the temperature was naturally raised to room temperature and the mixture was reacted at room temperature for 2 hours. The mixture was then poured into 200 mL of dilute hydrochloric acid (2 mol / L), stirred, and allowed to stand for separation. The separated aqueous phase was extracted with ethyl acetate three times, 100 mL each time. The organic phases were combined and washed with water until neutral. The solvent was spin-dried and slurried with 100 ml of petroleum ether to obtain 17.76 g of a white solid (compound 2) with an HPLC purity of 99% and a yield of 80%.

[0140] To a 500 mL reaction flask, 4.4 g (0.02 mol) of compound 2 and 3.93 g (0.01 mol) of compound 3 were added, followed by 200 mL of toluene, 100 mL of water, and 2.76 g of potassium carbonate. 0.02 g of tetrakis(triphenylphosphine)palladium was then added under nitrogen. The reaction was heated under reflux for 10 hours until the residual content of the raw material (compound 2) was below 0.2% as monitored by HPLC. Heating was stopped, the liquid was allowed to stand, and the separated organic phase was filtered to remove insoluble matter. The solvent was then dried and the mixture was passed through a silica gel column with 1000 mL of eluent (eluent being petroleum ether:ethyl acetate in a volume ratio of 1:1). The silica gel was selected to have a mesh size of 100-200. The eluted solution was dried to give 5.7 g of a red powder (VII1) with a yield of 85% and an HPLC purity of 99.2%.

[0141] The structure of compound VII1 was verified by H NMR and mass spectrometry, and the NMR characterization data of VII1 are as follows:

[0142] 1 HNMR (CDCl3, 400MHZ, ppm): δ = 0.92 (m, 6H), 1.30 (d, 8H), 1.75-1.45 (d, 8H), 2.49 (m, 6H), 4.06 (d, 4H), 7.05 (s, 4H), 7.67 (s, 4H), 7.52 (s, 4H).

[0143] Example 2

[0144] This embodiment provides a dichroic dye, the structural formula of which is shown in Formula VII3:

[0145]

[0146] The specific synthesis steps are similar to those in Example 1, except that: in this example, compound 1 in Example 1 is replaced by

[0147] That's it.

[0148] The structure of compound VII3 was verified by H NMR and MS, such as Figure 1 As shown, MS-ESI (m / z) of VII3: [M+H] + 789.39934.

[0149] Example 3:

[0150] This embodiment provides a dichroic dye, the structural formula of which is shown in Formula VII7, and the synthesis route is as follows:

[0151]

[0152] The specific synthesis steps are as follows:

[0153] 36g of compound 4 and 500mL of tetrahydrofuran were added to a 1L three-necked flask, and then the temperature was lowered to -80°C under nitrogen protection. 44ml of butyl lithium (2.5mol / L) was added dropwise at -80°C for 2 hours. After stirring with temperature control for 4 hours, 11g of trimethyl borate was added dropwise at -80°C. After 0.5h of dropping, the temperature was naturally raised to -50°C and stirred at this temperature for 2 hours. Then, the solution was poured into 300ml of dilute hydrochloric acid (2mol / L) for hydrolysis. After stirring, the solution was allowed to stand for separation. The separated aqueous phase was extracted with ethyl acetate 3 times, 100mL each time. The organic phases were combined and washed with water until neutral. The solvent was spin-dried and slurried with 100ml of petroleum ether to give 26g of a white solid (compound 5). The HPLC purity was 98.9% and the yield was 80%.

[0154] To a 500 mL reaction flask, 6.3 g of compound 5 and 3.93 g of compound 3 were added, followed by 200 mL of toluene, 100 mL of water, and 2.76 g of potassium carbonate. 0.02 g of tetrakis(triphenylphosphine)palladium was then added under nitrogen protection. The reaction was heated under reflux for 10 min until the residual content of the raw material (compound 5) was below 0.2% as monitored by HPLC. Heating was stopped, the liquid was allowed to stand, and the separated organic phase was filtered to remove insoluble matter. The solvent was then dried and the mixture was passed through a silica gel column with 1000 mL of eluent (eluent being petroleum ether:ethyl acetate in a volume ratio of 1:1). The silica gel was selected to have a mesh size of 100-200. The eluted solution was dried to give 7.6 g of a red powder (VII7) with a yield of 86% and an HPLC purity of 99.3%.

[0155] The structure of compound VII7 was verified by H NMR and mass spectrometry, and the NMR characterization data of VII7 are as follows:

[0156] 1 HNMR (CDCl3, 400MHZ, ppm): δ = 0.93 (m, 6H), 1.25 (m, 6H), 1.31 (d, 8H), 1.75-1.44 (d, 8H), 2.49 (m, 6H), 2.60 (m, 4H), 4.06 (d, 4H), 7.05 (s, 4H), 7.07 (s, 2H), 7.67 (s, 4H), 7.75-7.45 (s, 4H), 7.80 (s, 2H), 7.90 (m, 2H).

[0157] Example 4:

[0158] This embodiment provides a dichroic dye, the structural formula of which is shown in Formula VII4:

[0159]

[0160] The specific synthesis steps are similar to those in Example 1, except that: in this example, compound 1 in Example 1 is replaced by

[0161] That's it.

[0162] The structure of compound VII4 was verified by H NMR and mass spectrometry, and the NMR characterization data of VII4 are as follows:

[0163] 1 HNMR (CDCl3, 400MHZ, ppm): δ=0.93 (m, 6H), 1.29 (d, 8H), 1.30 (d, 4H), 2.50-1.61 (d, 8H), 2.49 (m, 6H), 7.40-7.35 (s, 8H), 7.67-7.52 (s, 4H).

[0164] Compound VII2, Compound VII5, and Compound VII6 can be prepared by a method similar to that of Example 1, except that Compound 1 is replaced by

[0165] That is, the structures of the finally obtained compounds VII2, VII5 and VII6 were verified by H NMR and mass spectrometry, and the yields and purities of compounds VII2, VII5 and VII6 were comparable to those of compound VII1 in Example 1.

[0166] Example 5:

[0167] This embodiment provides a dichroic dye, the structural formula of which is shown in Formula VII11.

[0168]

[0169] The specific synthesis steps are similar to those in Example 3, except that: in this example, compound 4 in Example 3 is replaced by

[0170] That's it.

[0171] The structure of compound VII11 was verified by H NMR and mass spectrometry. The NMR characterization data of VII11 are as follows:

[0172] 1 HNMR (CDCl3, 400MHZ, ppm): δ=0.76 (m, 6H), 0.93 (m, 6H), 1.25 (m, 6H), 1.53-1.26 (m, 36H), 2.48 (m, 6H)2 .60(m, 4H), 2.76(s, 2H), 7.07(s, 2H), 7.37-7.36(s, 8H), 7.40(s, 2H), 7.67(s, 2H), 7.90-7.82(m, 4H).

[0173] Compounds VII8-VII10 can be prepared by a method similar to that of Example 3, except that compound 4 is replaced by

[0174] That is, the structures of the finally obtained compounds VII8-VII10 were verified by H NMR spectroscopy and mass spectrometry, and the yield and purity of compounds VII8-VII10 were equivalent to those of compound VII7 in Example 3.

[0175] Structures of two commercially available dichroic dyes:

[0176]

[0177] The matrix and liquid crystal composition were prepared according to the above method, and the structures of two commercially available dichroic dyes represented by Formula R1 and Formula R2 were added to the matrix to prepare a liquid crystal composition as a comparative example. The specific composition formula is shown in Tables 3-4 below. The mass percentage of each raw material is calculated based on the total content of each raw material in the corresponding table as 100%.

[0178] Table 3 Composition and performance parameters of the matrix and corresponding liquid crystal compositions in Examples 6-10 and Comparative Examples 1-2

[0179]

[0180]

[0181]

[0182] Table 4 Composition and performance parameters of the matrix and corresponding liquid crystal compositions used in Examples 11-12

[0183]

[0184]

[0185] Photoelectric performance test:

[0186] The liquid crystal compositions prepared according to the formulations of Examples 6-12 and Comparative Examples 1-2 were poured into a test box for photoelectric performance testing. The visible light transmittance of the test box was tested in both the power-off and power-on states (the power-on voltage was 6 V). The specific test results are shown in Table 5 below.

[0187] Table 5 Photoelectric performance test

[0188]

[0189]

[0190] Photostability test:

[0191] Liquid crystal compositions prepared according to the formulations of Examples 6-12 and Comparative Examples 1-2 were poured into a test cell and irradiated with 365nm UV light for 240 hours. The color of the test cell was observed before and after UV irradiation, and the T-light transmittance was measured under power-off conditions. The specific experimental results are shown in Table 6 below.

[0192] Table 6 Light stability test

[0193]

[0194]

[0195] Solubility test:

[0196] The formulas of the liquid crystal compositions of Examples 13-17 and Comparative Examples 3-4 are shown in the following table:

[0197] Table 7 Formulations of the liquid crystal compositions of Examples 13-17 and Comparative Examples 3-4

[0198]

[0199] According to the formulations in Examples 13-17 and Comparative Examples 3-4, dyes of corresponding weight percentages were added to Precursor 1. The mixtures were then stirred at room temperature (25°C) for 1 hour, and the solubility of each dye in Precursor 1 was observed. The stirred mixtures were then placed in a glove box at -20°C for 240 hours, and the solubility of each dye in Precursor 1 was observed. The specific experimental results are shown in Table 8 below.

[0200] Table 8 Solubility test results

[0201] Room temperature After being placed in a glove box at -20℃ for 240h Example 13 Completely dissolved No precipitation Example 14 Completely dissolved No precipitation Example 15 Completely dissolved No precipitation Example 16 Completely dissolved No precipitation Example 17 Completely dissolved No precipitation Comparative Example 3 Completely dissolved Red dye precipitation Comparative Example 4 Completely dissolved Red dye precipitation

[0202] By replacing the compound represented by formula VII contained in the liquid crystal composition of Examples 6-17 of the present invention with a new combination of compounds represented by formula VII within the scope of the present invention, the technical effects substantially equivalent to those in Examples 6-17 can be achieved. Combined with the experimental data in Tables 3-8 above, it can be seen that the dichroic dye of a specific structure provided by the present invention has good dichroicity and high light stability, and the dye has high compatibility with liquid crystal materials. The liquid crystal composition containing the dye has a high dichroic ratio, and the light transmittance changes significantly when the power is on and off, and has high light stability. There is no obvious color change after 240 hours of ultraviolet light irradiation, and the change in light transmittance does not exceed 6%. The operating temperature range is wide, and the dye does not precipitate in a low temperature environment. It has broad application prospects in the fields of dimming films, dimming glasses or guest-host liquid crystal displays.

[0203] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A dichroic dye, characterized in that having at least one of the structures shown in Formula VIIA, wherein m and n are each independently selected from 0 or 1; R1 and R2 are each independently selected from a C1-C12 linear or branched alkyl group, or a C1-C12 linear or branched alkoxy group; Each is independently selected from 1,4-phenylene, 1,4-cyclohexylene, or 1,4-phenylene or 1,4-cyclohexenylene in which 1 to 4 H atoms are substituted with a C1-C4 straight-chain alkyl group.

2. The dichroic dye according to claim 1, wherein The compound represented by formula VIIA is selected from at least one of the structures represented by formula VII1 to formula VII11 below, 3. A liquid crystal composition, characterized in that Comprising at least one dichroic dye according to any one of claims 1 to 2, and at least one positive dielectric anisotropic liquid crystal compound; The positive dielectric anisotropic liquid crystal compound comprises at least one of the structures shown in Formula I or Formula II, wherein R3 is selected from C1-C10 straight or branched alkyl, C1-C10 straight or branched alkoxy, C2-C10 straight or branched alkenyl, C3-C10 straight or branched alkenyloxy, or any one or more unconnected -CH2- groups in any of these groups are independently substituted with cyclopropylene, cyclobutylene or cyclopentylene; R4 is selected from F, a C1-C5 straight chain or branched alkyl group in which at least one H is substituted by F, a C1-C5 straight chain or branched alkoxy group in which at least one H is substituted by F, a C2-C5 straight chain or branched alkenyl group in which at least one H is substituted by F, or a C3-C8 straight chain or branched alkenyloxy group in which at least one H is substituted by F; Z5 is selected from a single bond, -CH2CH2- or -CF2O-; r is selected from 1, 2, 3 or 4. When r is selected from 2, 3, 4, each Can be the same or different; Each independently selected from Wherein, R5 is selected from C1-C10 linear or branched alkyl, or C1-C10 linear or branched alkoxy; R6 is CN; Each independently selected from Z6 and Z7 are each independently selected from a single bond or -COO-; s is selected from 0 or 1; The total content of the dichroic dye in the liquid crystal composition is 0.5%-2%.

4. The liquid crystal composition according to claim 3, characterized in that The liquid crystal composition further comprises at least one of the structures shown in Formula III, wherein R7 and R8 are each independently selected from a C1-C10 linear or branched alkyl group, a C1-C10 linear or branched alkoxy group, an unsubstituted or at least C2-C10 linear or branched alkenyl group, or a C3-C10 linear or branched alkenyloxy group; Each independently selected from t is selected from 1 or 2. When t is 2, the two Same or different.

5. A dimming film, characterized in that: The dimming film comprises at least one dichroic dye according to any one of claims 1 to 2, or at least one liquid crystal composition according to any one of claims 3 to 4.

6. A liquid crystal display element, characterized in that: The liquid crystal display element comprises at least one dichroic dye according to any one of claims 1 to 2, or at least one liquid crystal composition according to any one of claims 3 to 4.

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