Azo dye compound as well as preparation method and application thereof

Abstract

The invention discloses an azo dye compound, the azo dye compound is a compound with a general formula I structure, and the general formula I is # imgabs0 #. The azo dye compound disclosed by the invention has relatively high dichroic ratio and good dissolvability, and the synthetic method disclosed by the invention has the advantages of simplicity and convenience in operation, low synthetic cost and the like; the liquid crystal display is especially suitable for guest-host liquid crystal display devices.

Description

Technical Field

[0001] The present invention relates to the field of dye liquid crystal materials, and in particular, to an azo dye compound, a preparation method thereof, and an application thereof. Background Art

[0002] Dye liquid crystal is a guest-host type liquid crystal material composed of doping a small amount of guest dichroic dye in a host liquid crystal. Due to the interaction between the host and the guest, the dichroic dye molecules will be arranged orderly following the host liquid crystal molecules. Therefore, the arrangement mode of the host liquid crystal can be changed by changing the applied external electric field, and then the arrangement direction of the dye molecules is driven to change. Among them, dichroic dye refers to a dye compound with different light absorption intensities along different axial directions. Therefore, when it changes its direction following the rotation of the host liquid crystal molecules, its light absorption ability also changes accordingly, so as to achieve the effect of adjusting the light transmittance. By adding dichroic dyes of different colors, the liquid crystal device presents different colors, and the adjustment of visible light in different bands can be realized.

[0003] Compared with traditional liquid crystal devices, this type of technology does not require the use of a polarizing plate, so it has higher light utilization rate. In recent years, with the continuous pursuit of higher quality of life by people, the application fields of dye liquid crystal have been continuously expanded. Such as the color-changing skylights of cars, the color-changing glass inside and outside buildings, the color-changing side windows on large public transport vehicles, and smart glasses that change color with the intensity of external light, etc., are all emerging application scenarios of dye liquid crystal. Compared with the application scenarios of traditional liquid crystal materials, dye liquid crystal has a wider range of use on large-size devices, and many of them are emerging fields, so its demand is greater and the application prospect is broader. However, due to the relatively complex synthesis process of dichroic dyes, high cost and low yield, the number of manufacturers and dye types that can supply dichroic dyes in large quantities on the market is limited at present, and the price is expensive, and the application cost is too high, which restricts the development of dichroic dyes. In addition, due to problems such as the dichroism of the dye molecules themselves and insufficient solubility in the host liquid crystal, the dye liquid crystal has the problem of insufficient contrast, which also restricts the performance and application scenarios of the guest-host liquid crystal. Therefore, the development of dye compounds with low cost, high dichroism and good solubility has become the research focus. Summary of the Invention

[0004] The purpose of the present invention is to provide an azo dye compound, a preparation method thereof, and an application thereof, which have a relatively high dichroic ratio, good solubility and low synthesis cost.

[0005] Technical Solution: To achieve the above purpose, according to one aspect of the present invention, an azo dye compound is provided. The azo dye compound is a compound having the general formula I, and the general formula I is:

[0006]

[0007] Among them, R1 is selected from an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 18 carbon atoms or an alkoxy group having 1 to 18 carbon atoms; the alkyl group and the alkoxy group are straight-chain or branched-chain alkyl groups and alkoxy groups;

[0008] each independently selected from and at least one of them is

[0009] R2 is selected from any one of the following, where R3 and R4 are each independently selected from an alkyl group having 1 to 18 carbon atoms and an alkoxy group having 1 to 18 carbon atoms, and the alkyl group and the alkoxy group are straight-chain or branched-chain alkyl groups and alkoxy groups.

[0010] According to another aspect of the present invention, a preparation method of a compound represented by general formula I is provided. The preparation method includes the following steps:

[0011]

[0012] (1) Under the protection of an inert gas, dissolve the compound represented by general formula II in a certain proportion of solvent, first mix it fully with nitrite, and then carry out a diazotization reaction under acidic conditions at -5 to 25 °C to generate a diazonium salt solution; then dissolve the compound represented by general formula III in a certain proportion of solvent, add a pH regulator, and carry out a coupling reaction with the generated diazonium salt solution to obtain an azo compound represented by general formula IV,

[0013] The compound having general formula II is

[0014]

[0015] The compound having general formula III is

[0016]

[0017] The compound having general formula IV is

[0018]

[0019] (2) Under the protection of inert gas, dissolve the compound shown in General Formula IV generated in Step 1 in a certain proportion of solvent, first mix it fully with nitrite, and then carry out a diazotization reaction under acidic conditions at -5 to 25 °C to generate a diazonium salt solution; then dissolve the compound shown in General Formula V in a certain proportion of solvent, add a pH regulator, and carry out a coupling reaction with the generated diazonium salt solution to obtain the azo compound shown in General Formula VI, and the compound with General Formula V is

[0020]

[0021] The compound with General Formula VI is

[0022]

[0023] (3) Under the protection of inert gas, dissolve the compound shown in General Formula VI generated in Step 2 in a certain proportion of solvent, first mix it fully with nitrite, and then carry out a diazotization reaction under acidic conditions at -5 to 25 °C to generate a diazonium salt solution; then dissolve the compound shown in General Formula VII in a certain proportion of solvent, add a pH regulator, and carry out a coupling reaction with the generated diazonium salt solution to obtain the target compound shown in General Formula I,

[0024] The compound with General Formula VII is

[0025]

[0026] According to another aspect of the present invention, there is provided a liquid crystal composition comprising at least one azo dye compound shown in General Formula I.

[0027] According to another aspect of the present invention, there is provided an application of the azo dye compound shown in General Formula I above in a liquid crystal display material or a liquid crystal display device.

[0028] Beneficial effects: The azo dye compound of the present invention has a high dichroic ratio and good solubility, which is beneficial to improving the contrast of the display device; in addition, the synthesis method of the azo dye compound has the advantages of simple operation, low pollution, and high yield, which is beneficial to reducing the synthesis cost of the dye compound and improving the quality of the dye compound. Description of the Drawings

[0029] Figure 1 Absorption spectra of A of mixture MA3 at different wavelengths ∥ and A ⊥ Absorption spectrum diagram. Specific Embodiments

[0030] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The beneficial effects of the present invention will be further described below in conjunction with the embodiments.

[0031] In a typical embodiment of the present invention, an azo dye compound is provided. The azo dye compound is a compound having the general formula I, and the general formula I is:

[0032]

[0033] Wherein, R1 is selected from an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 18 carbon atoms or an alkoxy group having 1 to 18 carbon atoms; the alkyl group and the alkoxy group are straight-chain or branched-chain alkyl groups and alkoxy groups;

[0034] each independently selected from and at least one of them is

[0035] R2 is selected from any one of, wherein R3 and R4 are each independently selected from an alkyl group having 1 to 18 carbon atoms and an alkoxy group having 1 to 18 carbon atoms, and the alkyl group and the alkoxy group are straight-chain or branched-chain alkyl groups and alkoxy groups.

[0036] The azo dye compound of the present invention is a compound containing a tri-azo structure, so it has a relatively large conjugated system, which is beneficial to increasing the light absorption intensity, that is, a strong absorption effect can be achieved with a small amount of addition. In addition, the tri-azo structure increases the linearity of the compound, making it have a relatively large dichroic ratio, which is beneficial to increasing the contrast of the display device. In addition, the addition of the structure reduces the molecular symmetry, making it have a relatively low melting point, which is beneficial to increasing its solubility in liquid crystal compounds.

[0037] In another typical embodiment of the present invention, a preparation method of the azo dye compound of the general formula I is provided. The overall process route diagram of this preparation method is as follows:

[0038]

[0039] This preparation method includes the following steps:

[0040] (1) Under the protection of inert gas, a certain amount of the compound shown in General Formula II is dissolved in an isopropanol solvent with a volume 8 - 30 times that of the compound, and after sufficient stirring, nitrite with a molar ratio of 0.9 - 1.5 times that of the compound shown in General Formula II is added to obtain Mixture 1, which is cooled to -5 - 25 °C for standby. In another container, hydrochloric acid with a molar ratio of 4 - 5 times that of the compound shown in General Formula II is added, cooled to 0 - 5 °C, and Mixture 1 is added thereto. The temperature is controlled at 0 - 10 °C. After completion of addition, the mixture is stirred for 1 - 1.5 h to obtain Mixture 2 for standby. To another container, the compound shown in General Formula III with a molar ratio of 0.9 - 1.1 times that of the compound shown in General Formula II is added, and after being fully dissolved in a methanol-acetone mixed solvent with a volume 10 - 30 times that of the compound shown in General Formula III (the volume ratio of methanol to acetone is 2:0.8 - 1.2), sodium carbonate with a molar ratio of 2 - 5 times that of the compound shown in General Formula II is added, cooled to 0 - 5 °C, and Mixture 2 is added to the system. The temperature is controlled at 0 - 10 °C. After completion of addition, the mixture is stirred for 1 - 1.5 h and then directly filtered to obtain the compound shown in General Formula IV after purification;

[0041] (2) Under the protection of inert gas, the compound shown in General Formula IV obtained in Step 1 is dissolved in an isopropanol solvent with a volume 8 - 30 times that of the compound, and after sufficient stirring, nitrite with a molar ratio of 0.9 - 1.5 times that of the compound shown in General Formula IV is added to obtain Mixture 3, which is cooled to -5 - 25 °C for standby. In another container, hydrochloric acid with a molar ratio of 4 - 5 times that of the compound shown in General Formula IV is added, cooled to 0 - 5 °C, and Mixture 3 is added thereto. The temperature is controlled at 0 - 10 °C. After completion of addition, the mixture is stirred for 1 - 1.5 h to obtain Mixture 4 for standby. To another container, the compound shown in General Formula V with a molar ratio of 0.9 - 1.1 times that of the compound shown in General Formula IV is added, and after being fully dissolved in a methanol-acetone mixed solvent with a volume 10 - 30 times that of the compound shown in General Formula V (the volume ratio of methanol to acetone is 2:0.8 - 1.2), sodium carbonate with a molar ratio of 2 - 5 times that of the compound shown in General Formula IV is added, cooled to 0 - 5 °C, and Mixture 4 is added to the system. The temperature is controlled at 0 - 10 °C. After completion of addition, the mixture is stirred for 1 - 1.5 h, then stirred at room temperature for 10 h and filtered to obtain the compound shown in General Formula VI after purification;

[0042] (3) Under the protection of inert gas, dissolve the compound shown in the general formula VI obtained in step 2 in an isopropanol solvent with a volume 8 - 30 times that of the compound, stir well, and then add nitrite with a molar ratio of 0.9 - 1.5 times that of the compound shown in the general formula VI to obtain mixture 5, and cool it to -5 - 25 °C for standby. In another container, add hydrochloric acid with a molar ratio of 4 - 5 times that of the compound shown in the general formula VI, cool it to 0 - 5 °C, add mixture 5 thereto, control the temperature at 0 - 10 °C, and after completion of addition, stir for 1 - 1.5 h for standby to obtain mixture 6. Add the compound shown in the general formula VII with a molar ratio of 0.9 - 1.1 times that of the compound shown in the general formula VI to another container, fully dissolve it with a methanol-acetone mixed solvent (methanol:acetone volume ratio is 2:0.8 - 1.2) with a volume 10 - 30 times that of the compound shown in the general formula VII, add sodium carbonate with a molar ratio of 2 - 5 times that of the compound shown in the general formula VI, cool it to 0 - 5 °C, add mixture 6 to the system, control the temperature at 0 - 5 °C, after completion of addition, stir for 1 - 1.5 h, and then stir at room temperature for 10 h and filter to obtain the azo dye compound shown in the general formula I after purification.

[0043] The preparation method of the azo dye compound provided by this application has the advantages of simple operation and high yield.

[0044] In another typical embodiment of this application, a liquid crystal composition is provided, and this liquid crystal composition includes at least one azo dye compound having the structure shown in the general formula I.

[0045] The liquid crystal composition of the present invention can be prepared according to a conventional method. Usually, at a high temperature, the required amount of components is dissolved in a component constituting the main component in a relatively small amount; it is also possible to mix the solutions of the components into an organic solvent, such as mixing into acetone, chloroform or methanol, and after sufficient mixing, remove the solvent again, such as removing the solvent by distillation.

[0046] In a preferred embodiment of this application, the above liquid crystal composition further includes at least one liquid crystal compound of component II, at least one liquid crystal compound of component III, at least one liquid crystal compound of component IV, at least one liquid crystal compound of component V, a chiral agent with a mass fraction of 0 - 20% and a stabilizer with a mass fraction of 0 - 20%.

[0047] The component II is a liquid crystal compound having the general formula A, and the general formula A is as follows:

[0048]

[0049] n is 1 or 2;

[0050] When n is 1, Selected from

[0051] When n is 2, the component includes two That is appears twice in the component

[0052] and are each independently selected from the group consisting of

[0053] R5 is selected from alkyl groups having 1 to 7 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, alkenyl groups having 2 to 7 carbon atoms, alkenyloxy groups having 2 to 7 carbon atoms, halogenated alkyl groups having 1 to 7 carbon atoms, halogenated alkoxy groups having 1 to 7 carbon atoms, halogenated alkenyl groups having 2 to 7 carbon atoms, halogenated alkenyloxy groups having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups;

[0054] The component III is a liquid crystal compound having the general formula B, and the general formula B is as follows:

[0055]

[0056] R6 is selected from alkyl groups having 1 to 7 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, alkenyl groups having 2 to 7 carbon atoms, alkenyloxy groups having 2 to 7 carbon atoms, halogenated alkyl groups having 1 to 7 carbon atoms, halogenated alkoxy groups having 1 to 7 carbon atoms, halogenated alkenyl groups having 2 to 7 carbon atoms, halogenated alkenyloxy groups having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups;

[0057] X1 and X2 are each independently selected from H or F, and at least one of X1 and X2 is F;

[0058] The component IV is a liquid crystal compound having the general formula C, and the general formula C is as follows:

[0059]

[0060] R7 is selected from an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 2 to 7 carbon atoms, a halogenated alkyl group having 1 to 7 carbon atoms, a halogenated alkoxy group having 1 to 7 carbon atoms, a halogenated alkenyl group having 2 to 7 carbon atoms, a halogenated alkenyloxy group having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups,

[0061] Component V is a liquid crystal compound having the general formulas D1 to D3, and the general formulas D1 to D3 are as follows:

[0062] D1, D2, D3,

[0063] wherein, R8 and R9 are each independently selected from an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 2 to 7 carbon atoms, a halogenated alkyl group having 1 to 7 carbon atoms, a halogenated alkoxy group having 1 to 7 carbon atoms, a halogenated alkenyl group having 2 to 7 carbon atoms, a halogenated alkenyloxy group having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups.

[0064] The above chiral agents include but are not limited to the following:

[0065]

[0066]

[0067] The above stabilizers are one or more of the compounds represented by the general formulas S1 to S4:

[0068] S1, S2, S3, S4,

[0069] Among them, Y1 is selected from H, F, an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 2 to 7 carbon atoms, a halogenated alkyl group having 1 to 7 carbon atoms, a halogenated alkoxy group having 1 to 7 carbon atoms, a halogenated alkenyl group having 2 to 7 carbon atoms, a halogenated alkenyloxy group having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups.

[0070] In another typical embodiment of the present application, an application of the above azo dye compound in a liquid crystal display material or a liquid crystal display device is provided. Applying the azo dye compound of the present application in the preparation of a liquid crystal composition, a liquid crystal display material or a liquid crystal display device can significantly improve the performance of the liquid crystal composition, the liquid crystal display material or the liquid crystal display device.

[0071] The beneficial effects of the present invention will be further described below in conjunction with examples.

[0072] The following examples are used to explain the present invention rather than limit it. The percentages involved in the examples are all mass percentages, and the temperature is expressed in degrees Celsius. The measured physical and chemical parameters are expressed as follows: T NI represents the clearing point; △n represents the optical anisotropy (△n = ne - no, 589 nm, measurement temperature 25 °C); △ε represents the dielectric anisotropy (△ε = ε∥ - ε⊥, 25 °C); K 11 represents the splay elastic coefficient (measurement temperature 25 °C); K 33 represents the bend elastic coefficient (measurement temperature 25 °C), and T is measured by DSC NI ; △n is measured by an Abbe refractometer; △ε, K 11 and K 33 .

[0073] In the embodiments of the present invention, the main chain of the liquid crystal molecule is named: cyclohexyl is represented by the letter C; phenyl is represented by the letter P; the phenyl group with a single fluorine substitution on the left is represented by the letter H2, and the phenyl group with a single fluorine substitution on the right is represented by the letter H1; the corresponding codes of the specific group structures are shown in Table 1:

[0074] Table 1

[0075]

[0076] The branched chains of each compound are converted into chemical formulas according to Table 2 below. The left branched chain is represented by R1, and the right branched chain is represented by R2. Among them, the group C n H 2n+ 1 and C m H 2m+1 are straight-chain alkyl groups with n and m carbon atoms respectively, and Cp represents cyclopentyl C n H 2n+1 Cp represents cyclopentyl with a straight-chain alkyl group of n carbon atoms. The main chain and the branched chain, as well as the branched chains, are separated by "-". When naming, the main chain comes first and the branched chain comes second. For example, is represented by CMPP-2-N; is represented by CPP-3-N, is represented by PH1P-3-N; is represented by CC-3-V.

[0077] Table 2

[0078] Code R1 R2 n-m CnH2n+1 CmH2m+1 n-Om CnH2n+1 OCmH2m+1 nO-Om OCnH2n+1 OCmH2m+1 n-Cp CnH2n+1 Cp n-mCp CnH2n+1 CmH2m+1Cp n-F CnH2n+1 F Cp-m Cp CmH2m+1 Cp-Om Cp OCmH2m+1 CpO-Om OCp OCmH2m+1 Cp-F Cp F nCp-m CnH2n+1Cp CmH2m+1 nCp-Om CnH2n+1Cp OCmH2m+1 nCpO-Om CnH2n+1CpO OCmH2m+1 nCp-F CnH2n+1Cp F n-OCp CnH2n+1 OCp n-N CnH2n+1 CN nO-N OCnH2n+1 CN n-V CnH2n+1 CH=CH2

[0079] Preparation method of compound A3 in Example 1:

[0080]

[0081] (1) Under nitrogen protection, add 65 g of 4-pentyloxyaniline and 650 ml of isopropanol to a 1 L single-necked flask. After stirring well, add 26 g of sodium nitrite and cool to below 10 °C for standby. Add 623 ml of dilute hydrochloric acid with a concentration of 8.75% to a 2 L four-necked flask, cool to 0-5 °C, add the above solution to the system, control the temperature at 0-10 °C. After adding, keep warm and stir for 1-1.5 h to obtain a diazonium salt solution for standby. Add 49.51 g of 1-naphthylamine, 500 ml of methanol, and 250 ml of acetone to another 3 L four-necked flask. After complete dissolution, add 110 g of sodium carbonate and cool to 0-5 °C. Add the above diazonium salt solution to the system, control the temperature at 0-10 °C. After adding, keep warm and stir for 1-1.5 h, then filter directly, and then purify to obtain 100 g of dark red compound A1, with a yield of 83% and an HPLC purity > 97%;

[0082] (2) Under nitrogen protection, add 50.8 g of the product from the previous step and 1000 ml of isopropanol to a 2 L single-necked flask, stir and disperse, then add 10 g of sodium nitrite, stir evenly, and cool down to -5 to 25 °C for standby. Add 260 ml of dilute hydrochloric acid with a concentration of 8.75% to a 2 L four-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 20 g of 2-methoxy-5-methylaniline, 200 ml of methanol, and 100 ml of acetone to another 2 L four-necked flask, stir to dissolve, then add 46.11 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 5 °C, after adding, keep warm for 1 to 1.5 h and then stir naturally overnight. Filter and purify to obtain 50 g of compound A2 with a yield of 68%.

[0083] (3) Under nitrogen protection, add 20 g of the product from the previous step and 400 ml of isopropanol to a 1 L single-necked flask, stir well, then add 2.76 g of sodium nitrite, cool down to below 10 °C for standby. Add 72 ml of dilute hydrochloric acid with a concentration of 8.75% to a 1 L four-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 5.89 g of N-phenylpyrrolidine, 60 ml of methanol, and 30 ml of acetone to another 1 L four-necked flask, stir well, then add 12.72 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 5 °C, after adding, stir overnight. Filter by suction and purify to obtain 18 g of purple dye compound A3 with a yield of 67%.

[0084] Example 2 Preparation method of compound B3:

[0085]

[0086] (1) Under nitrogen protection, add 37.6 g of 4-pentyloxyaniline and 350 ml of isopropanol to a 500 mL single-necked flask, stir well, then add 15 g of sodium nitrite, cool down to below 10 °C for standby. Add 360 ml of dilute hydrochloric acid with a concentration of 8.75% to a 1 L four-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 27.44 g of 2-methoxy-5-methylaniline, 300 ml of methanol, and 150 ml of acetone to another 2 L four-necked flask, dissolve completely, then add 63.6 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h and then filter directly, and then purify to obtain 54.5 g of dark red compound B1 with a yield of 79% and an HPLC purity > 98.5%;

[0087] (2) Under nitrogen protection, add 6.9 g of compound B1 to a 250 mL single-necked flask, disperse it by stirring with 140 mL of isopropanol, then add 1.5 g of sodium nitrite, stir evenly, and cool down to -5 to 25 °C for standby. Add 36 mL of dilute hydrochloric acid with a concentration of 8.75% to a 250 mL three-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 2.9 g of 1-naphthylamine, 30 mL of methanol, and 15 mL of acetone to another 500 mL four-necked flask, stir to dissolve, then add 6.4 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 5 °C, after adding, keep warm for 1 h and then naturally warm up and stir overnight. Filter and purify to obtain 8 g of compound B2 with a yield of 79%.

[0088] (3) Under nitrogen protection, add 7.1 g of compound B2 to a 250 mL single-necked flask, add 150 mL of isopropanol, stir well, then add 1.07 g of sodium nitrite, cool down to below 10 °C for standby. Add 25 mL of dilute hydrochloric acid with a concentration of 8.75% to a 250 L three-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 2.1 g of N-phenylpyrrolidine, 20 mL of methanol, and 10 mL of acetone to another 500 mL four-necked flask, stir well, then add 4.5 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 5 °C, after adding, stir overnight. Filter by suction and purify to obtain 8.2 g of purple dye compound B3 with a yield of 85%.

[0089] Preparation method of compound C3 in Example 3:

[0090]

[0091] (1) Under nitrogen protection, add 37.6 g of 4-pentyloxyaniline to a 500 mL single-necked flask, add 350 mL of isopropanol, stir well, then add 15 g of sodium nitrite, cool down to below 10 °C for standby. Add 360 mL of dilute hydrochloric acid with a concentration of 8.75% to a 1 L four-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 27.44 g of 2-methoxy-5-methylaniline, 300 mL of methanol, and 150 mL of acetone to another 2 L four-necked flask, dissolve well, then add 63.6 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 10 °C, after adding, keep warm and stir for 1 to 1.5 h, then directly filter, and then purify to obtain 55 g of dark red compound C1 with a yield of 80% and an HPLC purity > 98.5%;

[0092] (2) Under nitrogen protection, add 10.3 g of compound C1 to a 500 ml single-necked flask, add 200 ml of isopropanol and stir to disperse. Then add 2.22 g of sodium nitrite, stir evenly, and cool down to -5 to 25 °C for standby. Add 45 ml of dilute hydrochloric acid with a concentration of 8.75% to a 500 mL four-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C. After adding, keep stirring at a constant temperature for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 4.12 g of 2-methoxy-5-methylaniline, 40 ml of methanol, and 20 ml of acetone to another 500 mL four-necked flask. After stirring and dissolving, add 9.5 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 5 °C. After adding, keep the temperature constant for 1 h and then stir overnight while the temperature rises naturally. Filter and purify to obtain 14 g of carmine compound C2, with a yield of 95%.

[0093] (3) Under nitrogen protection, add 5 g of compound C2 to a 250 ml single-necked flask, add 100 ml of isopropanol, stir well, then add 0.75 g of sodium nitrite, and cool down to below 10 °C for standby. Add 18 ml of dilute hydrochloric acid with a concentration of 8.75% to a 250 mL three-necked flask, cool down to 0 to 5 °C, add the above solution to the system, control the temperature at 0 to 10 °C. After adding, keep stirring at a constant temperature for 1 to 1.5 h to obtain a diazonium salt solution for standby. Add 1.5 g of N-phenylpyrrolidine, 15 ml of methanol, and 7.5 ml of acetone to another 250 mL four-necked flask. After stirring well, add 3.2 g of sodium carbonate, cool down to 0 to 5 °C, add the above diazonium salt solution to the system, control the temperature at 0 to 5 °C. After adding, stir overnight. Filter by suction and purify to obtain 5.4 g of purple dye compound C3, with a yield of 77%.

[0094] Example 4 Dichroism Test of Compound A3

[0095] Fully mix 0.5% by mass of compound A3 with 99.5% by mass of the liquid crystal composition HOST-1 shown in Table 3 and stir evenly to fully dissolve compound A3 to obtain mixture MA3. Pour mixture MA3 into a horizontally aligned liquid crystal cell with a cell thickness of 9 μm, and measure the absorption spectra of mixture MA3 with incident light parallel to the long axis direction of compound A3 molecules and incident light perpendicular to the long axis direction of compound A3 molecules respectively; the instrument used for the measurement is a Shimadzu UV-2600 spectrophotometer. In order to eliminate the influence caused by the absorption or reflection of the liquid crystal composition itself and the liquid crystal cell, a horizontally aligned liquid crystal cell with a cell thickness of 9 μm filled with 100% by mass of the liquid crystal composition HOST-1 is used as a reference at the same time, that is, the absorption spectrum of the obtained mixture MA3 minus the absorption spectrum of HOST-1. The absorption spectrum of mixture A3 is as shown in the appendix Figure 1 as follows.

[0096] Table 3

[0097]

[0098] According to the definition of the dichroic ratio of a dye, the dichroic ratio of a dye is determined by its absorption intensity A under incident light parallel to the long axis of the dye molecule ∥ and its absorption intensity A under incident light perpendicular to the long axis of the dye molecule ⊥ calculated therefrom. The discussion of the dichroic ratio of a dye is usually carried out at the maximum absorption wavelength of the dye. If the dye has multiple absorption peaks, the peak with the strongest absorption is usually selected. The dichroic ratio D A = A ∥ / A ⊥ . As shown in the appendix Figure 1 , the dichroic ratio of MA3 can be calculated to be 13.82.

[0099] From the above Examples 1 to 4, it can be seen that the azo dye compound provided by the present invention can achieve the preparation goal with relatively simple operation methods, easily achievable reaction conditions, and common organic reagents, and the compound has good dichroism.

[0100] Referring to the preparation methods similar to those in Examples 1 to 3, the following dye compounds can be conveniently prepared:

[0101]

[0102] In addition, although the embodiments of the present invention do not exhaust all the azo dye compounds, liquid crystal compositions containing them, and their preparation methods claimed, those skilled in the art can foresee that, based on the above disclosed embodiments, other similar compounds can be prepared only by combining their own professional knowledge without creative labor. Only representative embodiments are listed here.

[0103] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An azo dye compound, which is a compound having the general formula I, and the general formula I is: Wherein, R1 is selected from an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, a cyclopentyl group, or a cyclopentyl group substituted by an alkyl group having 1 to 18 carbon atoms or an alkoxy group having 1 to 18 carbon atoms; the alkyl group and the alkoxy group are straight-chain or branched-chain alkyl groups and alkoxy groups; Each independently selected from and at least one of which is R2 is selected from any one of them, wherein R3 and R4 are each independently selected from an alkyl group having 1 to 18 carbon atoms and an alkoxy group having 1 to 18 carbon atoms, and the alkyl group and the alkoxy group are straight-chain or branched-chain alkyl groups and alkoxy groups.

2. A method for preparing the azo dye compound according to claim 1, and the preparation method includes the following steps: (1) Under the protection of an inert gas, dissolve the compound represented by the general formula II in a certain proportion of a solvent, first mix it fully with nitrite, and then carry out a diazotization reaction under acidic conditions at -5 to 25 °C to generate a diazonium salt solution; then dissolve the compound represented by the general formula III in a certain proportion of a solvent, add a pH regulator, and carry out a coupling reaction with the generated diazonium salt solution to obtain an azo compound represented by the general formula IV, The compound having the general formula II is The compound having the general formula III is The compound having the general formula IV is (2) Under the protection of an inert gas, dissolve the compound represented by the general formula IV generated in step 1 in a certain proportion of a solvent, first mix it fully with nitrite, and then carry out a diazotization reaction under acidic conditions at -5 to 25 °C to generate a diazonium salt solution; then dissolve the compound represented by the general formula V in a certain proportion of a solvent, add a pH regulator, and carry out a coupling reaction with the generated diazonium salt solution to obtain an azo compound represented by the general formula VI, The compound having the general formula V is The compound having the general formula VI is (3) Under the protection of an inert gas, dissolve the compound represented by the general formula VI generated in step 2 in a certain proportion of a solvent, first mix it fully with nitrite, and then carry out a diazotization reaction under acidic conditions at -5 to 25 °C to generate a diazonium salt solution; then dissolve the compound represented by the general formula VII in a certain proportion of a solvent, add a pH regulator, and carry out a coupling reaction with the generated diazonium salt solution to obtain the target compound represented by the general formula I, The compound having the general formula VII is 3. According to the preparation method described in claim 2, characterized in that, In steps 1, 2, and 3, the diazotization reagent nitrite is sodium nitrite, the acidic reagent is hydrochloric acid, and the pH regulator is sodium carbonate.

4. According to the preparation method described in claim 2, characterized in that, In steps 1, 2, and 3, the diazotization reaction solvent is isopropyl alcohol, and the coupling reaction solvent is a methanol-acetone mixed solution, where the volume ratio of methanol to acetone is 2:0.8 to 1.

2.

5. According to step 1 of the preparation method described in claim 2, characterized in that, In step 1, the molar ratio of the compound of the general formula II: sodium nitrite: hydrochloric acid: the compound of the general formula III is preferably 1:1.03 to 1.06:4 to 5:0.8 to 1.

2.

6. According to step 2 of the preparation method described in claim 2, characterized in that, In step 2, the molar ratio of the compound of the general formula IV: sodium nitrite: hydrochloric acid: the compound of the general formula V is preferably 1:1.03 to 1.06:4 to 5:0.8 to 1.

2.

7. According to step 3 of the preparation method described in claim 2, characterized in that, In step 3, the molar ratio of the compound of the general formula VI: sodium nitrite: hydrochloric acid: the compound of the general formula VII is preferably 1:1.03 to 1.06:4 to 5:0.8 to 1.

2.

8. A liquid crystal composition, characterized in that, The liquid crystal composition includes at least one azo dye compound having the general formula I as described in claim 1.

9. According to the liquid crystal composition described in claim 8, characterized in that, The liquid crystal composition further comprises at least one liquid crystal compound of Component II, at least one liquid crystal compound of Component III, at least one liquid crystal compound of Component IV, at least one liquid crystal compound of Component V, a chiral agent with a mass fraction of 0 to 20%, and a stabilizer with a mass fraction of 0 to 20%. Component II is a liquid crystal compound having the general formula A as follows: n is 1 or 2; When n is 1, selected from When n is 2, the component includes two That is appears twice in the component, and each independently is R5 is selected from an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 2 to 7 carbon atoms, a halogenated alkyl group having 1 to 7 carbon atoms, a halogenated alkoxy group having 1 to 7 carbon atoms, a halogenated alkenyl group having 2 to 7 carbon atoms, a halogenated alkenyloxy group having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups; Component III is a liquid crystal compound having the general formula B as follows: R6 is selected from an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 2 to 7 carbon atoms, a halogenated alkyl group having 1 to 7 carbon atoms, a halogenated alkoxy group having 1 to 7 carbon atoms, a halogenated alkenyl group having 2 to 7 carbon atoms, a halogenated alkenyloxy group having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups; X1 and X2 are each independently selected from H or F, and at least one of X1 and X2 is F; Component IV is a liquid crystal compound having the general formula C as follows: R7 is selected from an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 2 to 7 carbon atoms, a halogenated alkyl group having 1 to 7 carbon atoms, a halogenated alkoxy group having 1 to 7 carbon atoms, a halogenated alkenyl group having 2 to 7 carbon atoms, a halogenated alkenyloxy group having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups, Component V is a liquid crystal compound having the general formulas D1 to D3 as follows: D1, D2, D3, Among them, R8 and R9 are each independently selected from an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms, an alkenyloxy group having 2 to 7 carbon atoms, a halogenated alkyl group having 1 to 7 carbon atoms, a halogenated alkoxy group having 1 to 7 carbon atoms, a halogenated alkenyl group having 2 to 7 carbon atoms, a halogenated alkenyloxy group having 2 to 7 carbon atoms, cyclopentyl, or cyclopentyl substituted by an alkyl group having 1 to 7 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, an alkenyl group having 2 to 7 carbon atoms or an alkenyloxy group having 2 to 7 carbon atoms; the alkyl group, the alkoxy group, the alkenyl group and the alkenyloxy group are straight-chain or branched-chain alkyl groups, alkoxy groups, alkenyl groups and alkenyloxy groups.

10. Use of the azo dye compound according to claim 1 in a guest-host liquid crystal display material or a guest-host liquid crystal display device.

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