A light-responsive liquid crystal alignment agent and a pretilt angle control method

Abstract

The application discloses a kind of light-responsive diamine monomers for orientation agent, light-responsive composition, polyamic acid solution, polyamic acid orientation agent, polyimide film prepared therefrom, display device and display module containing polyimide film, the adjustment method of pretilt angle.The light-responsive diamine monomer has or the structure shown, side chain with light-controlled deformation ability, with orientation function diamine monomer and other diamine monomers and dianhydride as raw material synthesis polyimide, reversible isomerization response unit is introduced in polyimide side chain, realize the effective regulation of pretilt angle, overcome the fundamental defect that prior art cannot realize function dynamic due to the limitation of chemical principle.

Description

Technical Field

[0001] This invention relates to the field of displays, and more specifically to a photoresponsive diamine monomer for an alignment agent, a photoresponsive composition, a polyamic acid solution, a polyamic acid alignment agent, a polyimide film prepared therefrom, a display device and display module containing the polyimide film, and a method for adjusting the pretilt angle. Background Technology

[0002] Polyimide (PI) has become an indispensable core material in modern high-end display technologies, especially thin-film transistor liquid crystal displays (TFT-LCDs), due to its excellent thermal stability, superior mechanical properties, good chemical inertness, and outstanding electrical insulation characteristics. In the field of liquid crystal displays, polyimide is mainly used as a liquid crystal alignment film. Its core function is to induce liquid crystal molecules to align uniformly and consistently along a specific direction through anisotropic interactions on its surface, thus laying the physical foundation for the optical performance of the display. In polymer stabilized vertical alignment (PSVA) technology, the role of the polyimide alignment agent is particularly crucial. It first provides initial vertical alignment capability, and then induces the polymerization of reactive monomers (RM) within the liquid crystal cell through ultraviolet (UV) light, forming a stable polymer network. This "anchors" the ideal liquid crystal pretilt angle, ultimately achieving a display effect with high contrast, fast response, and wide viewing angle.

[0003] As display technology evolves towards flexibility, intelligence, and scene adaptation, higher demands are placed on the dynamic adjustability of display device functions. The pretilt angle determined by traditional PSVA technology is permanently fixed once solidified during the manufacturing stage, leading to significant application bottlenecks: on the one hand, minute fluctuations in the manufacturing process can cause the pretilt angle to deviate from the design value, resulting in uneven display that cannot be corrected later, directly damaging product yield; on the other hand, its static nature makes it impossible to readjust the pretilt angle of the display panel after cell assembly. This not only limits its application in advanced optical functions requiring regionally differentiated pretilt angles, such as privacy displays and integrated lenses, but also makes it difficult for the device to compensate for performance drift caused by changes in ambient temperature, affecting the reliability of wide-temperature operation.

[0004] US Patent 20030007116A1 discloses a method for controlling the pretilt angle direction of a liquid crystal cell. Its core technical approach involves using a photosensitive alignment material and determining the liquid crystal alignment direction through two independent ultraviolet light irradiation steps. The first irradiation step (typically unpolarized light or oblique incident light at a specific angle) sets the pretilt angle and multiple potential liquid crystal tilting directions (i.e., molecules may tilt in two or more specific directions) on the alignment layer surface. The second irradiation step uses linearly polarized ultraviolet light, whose polarization direction coincides with one of the potential directions formed in the first step, thereby selectively activating and ultimately "locking" that single direction while suppressing other directions. This method achieves relatively independent control of the liquid crystal pretilt angle direction and size through this stepwise photochemical selection process. However, although the two-step photoalignment process of this technical solution is "selective" in the final step, the photochemical reaction on which each step depends is still irreversible in nature. This means that once the second polarized light irradiation is completed and the final selection is made, the orientation direction of the liquid crystal is permanently fixed and becomes a static property of the device, making it impossible to achieve dynamic mode switching of the same screen in different application scenarios.

[0005] Therefore, developing a smart alignment agent with dynamically and reversibly adjustable pretilt angle has become a highly attractive material solution for realizing next-generation adaptive displays (such as viewing angle switching modes, privacy-preserving displays, and optical information encryption). Endowing the alignment agent with this "optical programming" capability promises to transform some optical characteristics of displays from fixed hardware parameters into dynamic variables that can be defined by software, thereby significantly enhancing the product's added value and market competitiveness. Summary of the Invention

[0006] The purpose of this invention is to solve the above problems and provide a smart orientation agent with a dynamically and reversibly adjustable pretilt angle.

[0007] To achieve the above objectives, the technical method adopted by the present invention is as follows: A photoresponsive diamine monomer is provided, wherein the photoresponsive diamine monomer has the structure shown in Formula 1 or Formula 2: Formula 1, Equation 2, in, R1 and R2 are each independently selected from one of -H, -NO2, -N(CH3)2, -CH3, -OCH3, -OCH2CH3, -OCH(CH3)2, -CH(CH3)2, and -C(CH3)3; R3 and R4 are each independently selected from a single bond or at least one of the structures shown in Equations 3 to 9: Formula 3, Equation 4, Equation 5, Formula 6, Equation 7, Formula 8, Formula 9, In Equations 3, 4, or 5, n is an integer greater than or equal to 2 and less than or equal to 10; in Equations 6 and 7, m is an integer greater than or equal to 2 and less than or equal to 6, and n is an integer greater than or equal to 0 and less than or equal to 6; and, when R3 is selected from one of the structures shown in Equations 3 to 7, R4 is selected from one of the structures shown in Equations 8 or 9, or, when R4 is selected from one of the structures shown in Equations 3 to 7, R3 is selected from one of the structures shown in Equations 8 or 9; R5 is selected from one of the structures shown in Equation 10, Equation 11, or Equation 12: Formula 10, Formula 11, Equation 12; Preferably, R5 is selected from one of the structures shown in Formula 10 or Formula 12 above; R6 is selected from one of the structures shown in Equation 13 or Equation 14: Equation 13, Equation 14, In Equation 13 or Equation 14, n is an integer greater than or equal to 3 and less than or equal to 10.

[0008] Another object of the present invention is to provide a photoresponsive composition comprising a diamine monomer and a dianhydride monomer, wherein the diamine monomer comprises at least one of the above-described photoresponsive diamine monomers and at least one oriented diamine monomer.

[0009] Furthermore, the oriented diamine monomer has the structure shown in Formula 15 or Formula 16: Formula 15, Equation 16 in, R7 is selected from one of the structures shown in Equations 17, 18, 19, 20, and 21: Equation 17, Equation 18, Formula 19, Equation 20, Equation 21, In Equation 17, n is an integer greater than or equal to 0 and less than or equal to 10; in Equation 18 or Equation 20, m and n are each independently selected from integers greater than or equal to 0 and less than or equal to 6. R8 is selected from either a single bond or one of the structures shown in Equations 22, 23, and 24: Equation 22, Equation 23, Equation 24; R9 is selected from either a single bond or one of the structures shown in Equations 25, 26, and 27: Equation 25, Equation 26 Equation 27; R 10 Choose one of the structures shown in Equations 28 and 29: Equation 28, Equation 29 In Equation 28 or Equation 29, n is an integer greater than or equal to 3 and less than or equal to 10.

[0010] Furthermore, the molar ratio of the diamine monomer to the dianhydride monomer is 1:0.8~1, more preferably 1:0.9~0.98.

[0011] Furthermore, the diamine monomer also includes other conventional diamine monomers that are different from the photoresponsive diamine monomer and the oriented diamine monomer.

[0012] Furthermore, the photoresponsive diamine monomer accounts for 5-40 mol% of all diamine monomers, more preferably 10-25 mol%.

[0013] Furthermore, the oriented diamine monomer accounts for 5-40 mol% of all diamine monomers, more preferably 10-25 mol%.

[0014] Furthermore, the photoresponsive composition further includes an organic solvent, which is a commercially available type of organic solvent. More preferably, the organic solvent includes at least one of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, dimethyl sulfoxide, and propylene glycol methyl ether acetate.

[0015] Furthermore, the dianhydride monomer includes at least one of the following dianhydrides: , , , , , , , , , , , .

[0016] Furthermore, the other diamine monomers include at least one of the following diamines: , , , , , , , , , , , , , , , .

[0017] Another object of the present invention is to provide a polyamic acid solution obtained by reacting the above-described photoresponsive composition; Furthermore, the solid content of the polyamic acid solution is 10-30%, more preferably 15-25%.

[0018] Furthermore, the viscosity of the polyamic acid solution is 100-600 mPa·s, more preferably 200-500 mPa·s.

[0019] Another object of the present invention is to provide a method for preparing a polyamic acid solution, comprising the steps of: (1) Under a nitrogen atmosphere, the diamine monomer is dissolved in an organic solvent to obtain solution 1; (2) The dianhydride monomer is added to solution 1, and the reaction is carried out to obtain a polyamic acid solution; Furthermore, in step (2), the dianhydride monomer is added to solution 1 in batches; Furthermore, in step (2), the reaction temperature is not higher than 40°C, preferably 0-30°C, and more preferably 10-25°C; Furthermore, in step (2), the reaction time is 8-36h, more preferably 10-24h.

[0020] Another object of the present invention is to provide a polyamic acid orientation agent, which is obtained by diluting and filtering the above-mentioned polyamic acid solution with a diluent.

[0021] Further, the diluent includes at least one of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol dimethyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diacetone alcohol, and diisobutyl ketone.

[0022] Furthermore, the filter membrane used for filtration has a pore size of 0.1-1 micrometer, more preferably 0.1-0.5 micrometer.

[0023] Furthermore, the solid content of the polyamic acid orientation agent is 2.5-6%, more preferably 3%-5%.

[0024] Furthermore, the viscosity of the polyamic acid orientation agent is 6.5-9 mPa·s, more preferably 7.0-8.5 mPa·s.

[0025] Another object of the present invention is to provide a polyimide film obtained by coating and imidization reaction of the above-mentioned polyamic acid orientation agent.

[0026] Furthermore, the thickness of the polyimide film is 80-120 nm.

[0027] Furthermore, the imidization reaction is carried out under a nitrogen atmosphere.

[0028] Furthermore, the temperature range of the imidization reaction is 200-250°C.

[0029] Another object of the present invention is to provide a display device comprising the above-described polyimide film.

[0030] Furthermore, the pretilt angle of the display device is reversibly adjustable.

[0031] Another object of the present invention is to provide a method for adjusting the pretilt angle of a display device, comprising the steps of: (1) Applying ultraviolet light of a first wavelength and a first intensity to the display device to change the pretilt angle from a first state to a second state; (2) Apply ultraviolet light of a second wavelength and a second intensity to the display device obtained in step (1) to restore it to the first state or change it to the third state; Furthermore, the first wavelength range is 360-420 nm, and the first intensity range is 5-20 mW / cm². 2 .

[0032] Furthermore, the second wavelength range is 500-600 nm, and the second intensity range is 10-30 mW / cm². 2 .

[0033] Another object of the present invention is to provide a display module comprising the above-described display device.

[0034] Furthermore, the display module includes a view-switching display module, a privacy-protecting display module, or a rewritable display module.

[0035] The beneficial effects of the technical solution of the present invention include: This invention provides a key starting material for synthesizing photoreversibly modulated polyimide alignment agents. A flexible spacer group, a photoreversibly responsive group, and a terminal alignment group are sequentially bonded to the benzene ring of an aromatic diamine via a specific linking group, forming a side chain with photo-controlled deformation capabilities. This starting material, along with alignment-functional diamine monomers, other diamine monomers, and dianhydrides, are used as raw materials to synthesize polyimides. A photoreversibly isomerizing responsive unit is introduced into the polyimide side chain. This unit undergoes a reversible molecular conformational change under specific wavelength light irradiation. This microscopic deformation is transmitted to the material surface through the chemically bonded flexible spacer group, thereby directly and reversibly adjusting the anchoring effect between the interface and liquid crystal molecules, achieving effective control of the pretilt angle. This transforms the alignment layer from a passive, permanent "recording medium" into an active, responsive "intelligent interface." Therefore, the pretilt angle of the display device based on the alignment agent of the present invention can be non-destructively, reversibly and repeatedly adjusted and rewritten during the product use stage by applying a light source of specific wavelength and intensity; giving a single display panel dynamic and reconfigurable optical performance, enabling it to flexibly adapt to diverse application scenarios, thereby completely overcoming the fundamental defect of existing technologies that cannot achieve dynamic functionality due to limitations in chemical principles. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will be further described in detail below with reference to specific embodiments.

[0037] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the ordinary meaning that can be understood by one of skill in the art.

[0038] As analyzed in the background section, current mainstream liquid crystal photoalignment technologies primarily rely on irreversible photodimerization or photocrosslinking reactions induced by linearly polarized ultraviolet light to generate alignment capabilities. However, the fundamental limitation of this technology lies in the fact that the photochemical reaction it relies on is chemically irreversible. This chemical characteristic directly leads to an insurmountable consequence: once the alignment layer is shaped by light during manufacturing, the anisotropy generated on its surface is permanently fixed. This permanence makes the liquid crystal pretilt angle determined by it, and the resulting key optical properties such as display viewing angle and contrast distribution, static attributes that cannot be changed after the device leaves the factory. Therefore, display devices produced based on this technology have their functions fixed in a single mode and cannot respond to emerging, scene-adaptive application needs such as dynamic switching between private narrow viewing angles and public shared wide viewing angles. To address the problem of "device function staticization" directly caused by "chemical irreversibility," this invention innovates from the source of material design, providing a photoresponsive diamine monomer, a photoresponsive composition, a polyamic acid solution, a polyamic acid alignment agent, a polyimide film prepared therefrom, a display device and display module containing the polyimide film, and a method for adjusting the pretilt angle.

[0039] In a typical embodiment of this application, a photoresponsive diamine monomer is provided, the photoresponsive diamine monomer having the structure shown in Formula 1 or Formula 2: Formula 1, Equation 2, in, R1 and R2 are each independently selected from one of -H, -NO2, -N(CH3)2, -CH3, -OCH3, -OCH2CH3, -OCH(CH3)2, -CH(CH3)2, and -C(CH3)3; R3 and R4 are each independently selected from a single bond or one of the structures shown in Equations 3 to 9: Formula 3, Equation 4, Equation 5, Formula 6, Equation 7, Formula 8, Formula 9, In Equations 3, 4, or 5, n is an integer greater than or equal to 2 and less than or equal to 10; in Equations 6 and 7, m is an integer greater than or equal to 2 and less than or equal to 6, and n is an integer greater than or equal to 0 and less than or equal to 6; and, when R3 is selected from one of the structures shown in Equations 3 to 7, R4 is selected from one of the structures shown in Equations 8 or 9, or, when R4 is selected from one of the structures shown in Equations 3 to 7, R3 is selected from one of the structures shown in Equations 8 or 9; R5 is selected from one of the structures shown in Equation 10, Equation 11, or Equation 12: Formula 10, Formula 11, Equation 12; Preferably, R5 is selected from one of the structures shown in Formula 10 or Formula 12 above; R6 is selected from one of the structures shown in Equation 13 or Equation 14: Equation 13, Equation 14, In Equation 13 or Equation 14, n is an integer greater than or equal to 3 and less than or equal to 10.

[0040] The aforementioned photoresponsive diamine monomer is a key starting material for synthesizing photoreversibly modulated polyimide orientation agents. On the benzene ring of the aromatic diamine, a flexible spacer group, a photoreversibly responsive group, and a terminal orientation group are sequentially bonded through a specific linking group, thereby forming a side chain with photo-controlled deformation capability.

[0041] Another object of the present invention is to provide a photoresponsive composition comprising a diamine monomer and a dianhydride monomer, wherein the diamine monomer comprises at least one of the above-described photoresponsive diamine monomers and at least one oriented diamine monomer.

[0042] Furthermore, the oriented diamine monomer has the structure shown in Formula 15 or Formula 16: Formula 15, Equation 16 in, R7 is selected from one of the structures shown in Equations 17, 18, 19, 20, and 21: Equation 17, Equation 18, Formula 19, Equation 20, Equation 21, In Equation 17, n is an integer greater than or equal to 0 and less than or equal to 10; in Equation 18 or Equation 20, m and n are each independently selected from integers greater than or equal to 0 and less than or equal to 6. R8 is selected from either a single bond or one of the structures shown in Equations 22, 23, and 24: Equation 22, Equation 23, Equation 24; R9 is selected from either a single bond or one of the structures shown in Equations 25, 26, and 27: Equation 25, Equation 26 Equation 27; R 10 Choose one of the structures shown in Equations 28 and 29: Equation 28, Equation 29 In Equation 28 or Equation 29, n is an integer greater than or equal to 3 and less than or equal to 10.

[0043] Furthermore, the molar ratio of the diamine monomer to the dianhydride monomer is 1:0.8~1, more preferably 1:0.9~0.98. A slight excess of the diamine monomer allows for sufficient consumption of the dianhydride monomer, facilitating viscosity control and preventing excessive viscosity from affecting subsequent printability.

[0044] Furthermore, the diamine monomer also includes other conventional diamine monomers that are different from the photoresponsive diamine monomer and the oriented diamine monomer.

[0045] Furthermore, the photoresponsive diamine monomer accounts for 5-40 mol% of all diamine monomers, more preferably 10-25 mol%. If the percentage is lower than this, the number of photoresponsive units is insufficient, the modulation amplitude of the reversible conformational change on the interface anchoring force is too small, resulting in a very small pretilt angle adjustment range and an inability to achieve an effective viewing angle switching function. If the percentage is higher than this, it will disrupt the regular stacking of the polyimide backbone, which may lead to unstable initial pretilt angle and decreased uniformity of liquid crystal arrangement. At the same time, the introduction of a large number of azophenyl groups may increase the residual ionic impurities, resulting in a decrease in voltage retention rate (VHR) and an increase in residual DC voltage (RDC).

[0046] Furthermore, the oriented diamine monomer accounts for 5-40 mol% of all diamine monomers, more preferably 10-25 mol%. If the proportion is lower than this, the vertical orientation anchoring force will be insufficient, and the initial pretilt angle may deviate from the ideal value, resulting in a decrease in the contrast of the liquid crystal cell and an increase in dark-state light leakage. If the proportion is higher than this, the dense stacking of rigid long alkyl chains will restrict the degree of freedom of movement of the photoresponse side chains, making it difficult for the micro-deformation generated by photoisomerization to be effectively transferred to the interface, which manifests as a significant reduction in the adjustment range Δθ and a slower response.

[0047] Furthermore, the photoresponsive composition further includes an organic solvent, which is a commercially available type of organic solvent. More preferably, the organic solvent includes at least one of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, dimethyl sulfoxide, and propylene glycol methyl ether acetate.

[0048] Furthermore, the dianhydride monomer includes at least one of the following dianhydrides: , , , , , , , , , , , .

[0049] Furthermore, the other diamine monomers include at least one of the following diamines: , , , , , , , , , , , , , , , .

[0050] Another object of the present invention is to provide a polyamic acid solution obtained by reacting the above-described photoresponsive composition; Furthermore, the solid content of the polyamic acid solution is 10-30%, more preferably 15-25%.

[0051] Furthermore, the viscosity of the polyamic acid solution is 100-600 mPa·s, more preferably 200-500 mPa·s.

[0052] Another object of the present invention is to provide a method for preparing the above-mentioned polyamic acid solution, comprising the steps of: (3) Under a nitrogen atmosphere, the diamine monomer is dissolved in an organic solvent to obtain solution 1; (4) The dianhydride monomer is added to solution 1 to react and obtain a polyamic acid solution; Furthermore, in step (2), the dianhydride monomer is added to solution 1 in batches; Furthermore, in step (2), the reaction temperature is not higher than 40°C, preferably 0-30°C, and more preferably 10-25°C; Furthermore, in step (2), the reaction time is 8-36h, more preferably 10-24h.

[0053] Another object of the present invention is to provide a polyamic acid orientation agent, which is obtained by diluting and filtering the above-mentioned polyamic acid solution with a diluent.

[0054] Further, the diluent includes at least one of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol dimethyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diacetone alcohol, and diisobutyl ketone.

[0055] Furthermore, the filter membrane used for filtration has a pore size of 0.1-1 micrometer, more preferably 0.1-0.5 micrometer.

[0056] Furthermore, the solid content of the polyamic acid orientation agent is 2.5-6%, more preferably 3%-5%.

[0057] Furthermore, the viscosity of the polyamic acid orientation agent is 6.5-9 mPa·s, more preferably 7.0-8.5 mPa·s.

[0058] Another object of the present invention is to provide a polyimide film obtained by coating and imidization reaction of the above-mentioned polyamic acid orientation agent.

[0059] Furthermore, the thickness of the polyimide film is 80-120 nm.

[0060] Furthermore, the imidization reaction is carried out under a nitrogen atmosphere.

[0061] Furthermore, the temperature range of the imidization reaction is 200-250°C.

[0062] Another object of the present invention is to provide a display device comprising the above-described polyimide film.

[0063] Furthermore, the pretilt angle of the display device is reversibly adjustable.

[0064] Another object of the present invention is to provide a method for adjusting the pretilt angle of a display device, comprising the steps of: (3) Apply ultraviolet light of a first wavelength and a first intensity to the display device to change the pretilt angle from a first state to a second state; (4) Apply ultraviolet light of a second wavelength and a second intensity to the display device obtained in step (1) to restore it to the first state or change it to the third state; Furthermore, the first wavelength range is 360-420 nm, and the first intensity range is 5-20 mW / cm². 2 .

[0065] Furthermore, the second wavelength range is 500-600 nm, and the second intensity range is 10-30 mW / cm². 2 .

[0066] Another object of the present invention is to provide a display module comprising the above-described display device.

[0067] Furthermore, the display module includes a view-switching display module, a privacy-protecting display module, or a rewritable display module.

[0068] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0069] Example 1 Under nitrogen protection, 12.05 g (23.41 mmol) of photoresponsive diamine A-1, 4.52 g (11.69 mmol) of oriented functional monomer B-1, 3.04 g (13.37 mmol) of 4,4'-diaminobenzoyl aniline (C-1), and 3.65 g (33.45 mmol) of 2,6-diaminopyridine (C-2) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomers were fully dissolved. Finally, 10.8 g (55.07 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) and 4.92 g (23.41 mmol) of 2,6-diaminopyridine (C-2) were added to the solution. 1,2,3,4-cyclopentanetetracarboxylic dianhydride (D-2) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA (polyamic acid) solution with a viscosity of 345 cp.

[0070] The A-1 structural formula is: The B-1 structural formula is: The PAA solution was diluted to a solid content of 3.8% to obtain an orientation agent solution with a viscosity of 7.44 cp, which was then filtered through a 0.22-micron filter membrane.

[0071] Appendix: Synthesis of A-1 and B-1 A-1 synthesis steps: 1. In a dry 100 mL single-necked round-bottom flask, add 2.33 g (10 mmol) of Formula 1 and 2.01 g (10.05 mmol) of Formula 2 in sequence, then add 30 mL of glacial acetic acid. Stir at room temperature for 5 minutes to completely dissolve the solid and obtain a homogeneous orange-red solution.

[0072] 2. Seal the flask and place it at room temperature (25°C) in the dark. Stir the reaction for 24 hours. During the reaction, the progress is monitored by thin-layer chromatography (TLC) with petroleum ether / ethyl acetate as the developing solvent at a ratio of 8:2 (v / v) until the characteristic spots of the starting material of formula 1 completely disappear, at which point the reaction endpoint is determined.

[0073] 3. After the reaction was complete, the reaction solution was slowly poured into 150 mL of stirred ice water, and stirring was continued for 15 minutes, resulting in the precipitation of an orange-yellow solid. The solid was filtered under vacuum, and the filter cake was washed three times with deionized water (3 × 30 mL) to remove residual acetic acid, then washed once with 5 mL of cold anhydrous ethanol. The mixture was dried under vacuum to obtain the crude product. The crude product was recrystallized from the crude product by heating with anhydrous ethanol, and the crystals were precipitated by standing and cooling. After filtration, the crystals were dried under vacuum at 35°C for 8 hours to obtain 3.04 g of pure orange-yellow needle-like product of formula 3 (yield 80%). 4. In a dry 100 mL three-necked flask, add 3.04 g (8 mmol) of Formula 3, 1.21 g of triethylamine, and 20 mL of anhydrous DCM. Stir in an ice bath (0 °C) under nitrogen protection for 10 minutes to obtain a homogeneous solution. Dissolve 2.03 g (8.8 mmol) of 3,5-dinitrobenzoyl chloride in 10 mL of anhydrous DCM and slowly add it dropwise to the above solution while maintaining an ice bath. The addition should be completed within 10 minutes.

[0074] 5. After the addition is complete, remove the ice bath and allow the mixture to return to room temperature (25°C). Stir the mixture under nitrogen protection for 6 hours. Monitor the reaction progress using TLC with petroleum ether / ethyl acetate as the developing solvent at a ratio of 9:1 (v / v) until the characteristic spots of starting material formula 3 completely disappear, at which point the reaction endpoint is determined.

[0075] 6. After the reaction was complete, 50 mL of deionized water was added to the reaction solution to quench the reaction. After stirring for 5 minutes, the mixture was transferred to a separatory funnel, allowed to stand for separation, and the organic phase was separated. The aqueous phase was extracted twice with DCM (2 × 20 mL). All organic phases were combined and washed successively with 0.5 mol / L dilute hydrochloric acid (30 mL), saturated sodium bicarbonate solution (30 mL), and saturated brine (30 mL). The organic phase was dried with anhydrous sodium sulfate for 2 hours. The desiccant was removed by filtration, and the filtrate was concentrated under reduced pressure at 35 °C using a rotary evaporator to obtain a yellow crude product. The crude product was recrystallized from a mixed solvent of petroleum ether / ethyl acetate, filtered, and dried under vacuum at 40 °C for 6 hours to obtain 4.14 g of bright yellow pure product of formula 4 (yield 90%). 7. In a dry 100 mL three-necked flask, add 3.45 g (6 mmol) of Formula 4 and 35 mL of anhydrous THF, stir at room temperature until the substrate is completely dissolved, then add 10% Pd / C catalyst and stir until a suspension is formed.

[0076] 8. Install a condenser in the flask, first purging nitrogen into the system three times to replace the air, then connect a hydrogen balloon and purging hydrogen into the system three times to replace the nitrogen, finally maintaining a normal pressure hydrogen atmosphere. Place the reaction system at room temperature (25°C) in the dark and stir for 12 hours. Monitor the reaction progress using TLC with dichloromethane / methanol = 95:5 (v / v) as the developing solvent, until the characteristic spot of reactant formula 4 completely disappears, at which point the reaction endpoint is determined.

[0077] 9. After the reaction was complete, the hydrogen gas in the system was slowly vented, and the mixture was vacuum filtered using a diatomaceous earth pad to remove the Pd / C catalyst. The filter cake was washed three times with THF (3 × 10 mL), and all filtrates were combined. The filtrate was concentrated under reduced pressure at 40 °C using a rotary evaporator to remove most of the THF, yielding a light brown crude product. The crude product was purified by column chromatography with 200-300 mesh silica gel as the stationary phase and dichloromethane / methanol = 98:2 (v / v) as the eluent. The target fraction was collected, concentrated under reduced pressure, and dried under vacuum at 40 °C for 8 hours to obtain 2.86 g of a white solid of formula 5 (yield 92%).

[0078] B-1 synthesis steps: 1. In a dry 100 mL single-necked round-bottom flask, add 2.81 g (10 mmol) of Formula 7, 2.59 g (10.05 mmol) of Formula 6, and 2.07 g of anhydrous potassium carbonate in sequence, then add 20 mL of anhydrous DMF. Stir at room temperature for 5 minutes to allow the solid to be basically dispersed and dissolved, resulting in a homogeneous suspension.

[0079] 2. Install a spherical condenser in the flask, introduce a nitrogen protection system, place the flask in a temperature-controlled oil bath, heat to 80°C, and maintain the temperature under closed stirring for 12 hours. During the reaction, the progress is monitored using thin-layer chromatography (TLC) with petroleum ether / ethyl acetate as the developing solvent at a ratio of 9:1 (v / v) until the characteristic spot of the starting material of formula 7 completely disappears, at which point the reaction endpoint is determined.

[0080] 3. After the reaction was complete, the heating was turned off, and the reaction solution was allowed to cool naturally to room temperature. It was then slowly poured into 100 mL of stirred ice water, and stirring was continued for 10 minutes, resulting in the precipitation of a pale yellow solid. The solid was filtered under vacuum, and the filter cake was washed three times with deionized water (3 × 20 mL) to remove residual DMF and inorganic salts. It was then washed once with 5 mL of cold anhydrous ethanol and dried under vacuum to obtain the crude product. The crude product was recrystallized from the crude product by heating with anhydrous ethanol. After standing and cooling, crystals precipitated. These crystals were filtered and dried under vacuum at 40°C for 6 hours to obtain 3.79 g of the pale yellow needle-like pure product (Formula 8). (Yield 85%) 4. In a dry 100 mL three-necked flask (or high-pressure reactor), add 3.57 g (8 mmol) of Formula 8 and 30 mL of anhydrous THF, stir at room temperature until the substrate is completely dissolved, then add 10% Pd / C catalyst and stir until a suspension is formed.

[0081] 5. Install a condenser in the flask. First, purge the air in the system with nitrogen three times. Then, connect a hydrogen balloon and purge the nitrogen with hydrogen three times, finally maintaining a normal pressure hydrogen atmosphere. Place the reaction system in a temperature-controlled oil bath, heat to 50°C, and stir for 6 hours. Monitor the reaction progress using TLC with dichloromethane / methanol = 95:5 (v / v) as the developing solvent until the characteristic spot of reactant formula 8 completely disappears, at which point the reaction endpoint is determined.

[0082] 6. After the reaction was complete, the heating was turned off, and the reaction solution was cooled to room temperature. The hydrogen gas in the system was slowly purged, and the mixture was vacuum filtered using a diatomaceous earth pad to remove the Pd / C catalyst. The filter cake was washed three times with THF (3 × 10 mL), and all filtrates were combined. The filtrate was concentrated under reduced pressure at 40 °C using a rotary evaporator to remove most of the THF, yielding a grayish-white crude product. The crude product was purified by column chromatography with 200-300 mesh silica gel as the stationary phase and dichloromethane / methanol = 98:2 (v / v) as the eluent. The target component was collected, concentrated under reduced pressure, and dried under vacuum at 40 °C for 8 hours to obtain 2.84 g of a white solid pure product (Formula 9, yield: 92%).

[0083] The synthesis of A-2 to A-8 and B-2 to B-6 were carried out using the methods described above, employing conventional reaction mechanisms in the field of organic synthesis.

[0084] Example 2 Under nitrogen protection, 5.88 g (11.42 mmol) of photoresponsive diamine A-1, 7.77 g (19.02 mmol) of oriented functional monomer B-2, 4.50 g (19.80 mmol) of 4,4'-diaminobenzoyl aniline (C-1), and 6.94 g (25.86 mmol) of 1,4-bis(4-aminophenyl)piperazine (C-3) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added, and the mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Then, 14.4 g (73.43 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) was added to the solution, and the mixture was mechanically stirred at room temperature for 15 h to obtain a PAA solution with a viscosity of 402 cp.

[0085] The B-2 structural formula is: The PAA solution was diluted to a solid content of 3.7% to obtain an orientation agent solution with a viscosity of 7.79 cp, which was then filtered through a 0.22-micron filter membrane.

[0086] Example 3 Under nitrogen protection, 7.28 g (15.67 mmol) of photoresponsive diamine A-2, 4.33 g (10.97 mmol) of oriented functional monomer B-3, 5.74 g (23.50 mmol) of 1,2-bis(4-aminophenoxy)ethane (C-4), and 5.02 g (25.07 mmol) of 4,4'-diaminodiphenyl ether (C-5) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Finally, 10.53 g (50.11 mmol) of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (D-2) and 6.64 g (26.33 mmol) of 4,4'-diaminodiphenyl ether (C-5) were added to the solution. 1,2,3,4-Tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (D-3) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA solution with a viscosity of 452 cp.

[0087] The A-2 structural formula is: The B-3 structural formula is: The PAA solution was diluted to a solid content of 3.7% to obtain an orientation agent solution with a viscosity of 7.85 cp, which was then filtered through a 0.22-micron filter membrane.

[0088] Example 4 Under nitrogen protection, 6.54 g (13.47 mmol) of photoresponsive diamine A-3, 8.19 g (17.94 mmol) of oriented functional monomer B-4, 4.25 g (18.70 mmol) of 4,4'-diaminobenzoyl aniline (C-1), and 4.94 g (24.67 mmol) of 4,4'-diaminodiphenyl ether (C-5) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomers were fully dissolved. Finally, 9.68 g (49.36 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) and 6.01 g (23.83 mmol) of other compounds were added to the solution. 1,2,3,4-Tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (D-3) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA solution with a viscosity of 399 cp.

[0089] The A-3 structural formula is: The B-4 structural formula is: The above PAA solution was diluted to a solid content of 4.0% to obtain an orientation agent solution with a viscosity of 7.34 cp, which was then filtered through a 0.22-micron filter membrane.

[0090] Example 5 Under nitrogen protection, 6.18 g (12.72 mmol) of photoresponsive diamine A-3, 6.99 g (16.46 mmol) of oriented functional monomer B-5, 7.23 g (26.94 mmol) of 1,4-bis(4-aminophenyl)piperazine (C-3), and 4.27 g (18.71 mmol) of 4-aminobenzoic acid-4-aminophenyl ester (C-6) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added, and the mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Finally, 10.28 g (52.42 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) and 5.04 g (20.07 mmol) of other compounds were added to the solution. 1,2,4,5-cyclohexanetetracarboxylic dianhydride (D-4) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA solution with a viscosity of 344 cp.

[0091] The B-5 structural formula is: The PAA solution was diluted to a solid content of 3.7% to obtain an orientation agent solution with a viscosity of 7.49 cp, which was then filtered through a 0.22-micron filter membrane.

[0092] Example 6 Under nitrogen protection, 17.18 g (23.41 mmol) of photoresponsive diamine A-1, 2.87 g (11.69 mmol) of oriented functional monomer B-1, 2.70 g (13.37 mmol) of 4,4'-diaminobenzoyl aniline (C-1), and 2.34 g (33.45 mmol) of 2,6-diaminopyridine (C-2) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomers were fully dissolved. Finally, 9.60 g (55.07 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) and 4.87 g (23.41 mmol) of 2,6-diaminopyridine (C-2) were added to the solution. 1,2,3,4-cyclopentanetetracarboxylic dianhydride (D-2) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA solution with a viscosity of 417 cp.

[0093] The PAA solution was diluted to a solid content of 3.8% to obtain an orientation agent solution with a viscosity of 7.51 cp, which was then filtered through a 0.22-micron filter membrane.

[0094] Example 7 Under nitrogen protection, 7.51 g (15.10 mmol) of photoresponsive diamine A-4, 4.47 g (11.33 mmol) of oriented functional monomer B-3, and 11.15 g (49.06 mmol) of 4,4'-diaminobenzoyl aniline (C-1) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Then, 7.23 g (28.67 mmol) of 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (D-3) and 9.65 g (43.05 mmol) of 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride (D-4) were added to the solution. The mixture was mechanically stirred at room temperature for 12 h to obtain a PAA solution with a viscosity of 404 cp.

[0095] The A-4 structural formula is: The PAA solution was diluted to a solid content of 3.5% to obtain an orientation agent solution with a viscosity of 7.89 cp, which was then filtered through a 0.22-micron filter membrane.

[0096] Example 8 Under nitrogen protection, 8.13 g (15.75 mmol) of photoresponsive diamine A-5, 6.43 g (15.74 mmol) of oriented functional monomer B-2, 2.15 g (19.70 mmol) of 2,6-diaminopyridine (C-2), and 6.73 g (27.55 mmol) of 1,2-bis(4-aminophenoxy)ethane (C-4) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added, and the mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Then, 16.57 g (73.92 mmol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (D-4) was added to the solution, and the mixture was mechanically stirred at room temperature for 10 h to obtain a PAA solution with a viscosity of 370 cp.

[0097] The A-5 structural formula is: The PAA solution was diluted to a solid content of 3.6% to obtain an orientation agent solution with a viscosity of 7.53 cp, which was then filtered through a 0.22-micron filter membrane.

[0098] Example 9 Under nitrogen protection, 5.81 g (13.13 mmol) of photoresponsive diamine A-6, 9.74 g (17.49 mmol) of oriented functional monomer B-6, 3.32 g (12.37 mmol) of 1,4-bis(4-aminophenyl)piperazine (C-3), and 6.82 g (29.88 mmol) of 4-aminobenzoic acid-4-aminophenyl ester (C-6) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added, and the mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Finally, 10.01 g (51.04 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) and 4.31 g (19.23 mmol) of [unspecified substance] were added to the solution. 1,2,4,5-cyclohexanetetracarboxylic dianhydride (D-4) was reacted with mechanical stirring at room temperature for 18 h to obtain a PAA solution with a viscosity of 355 cp.

[0099] The A-6 structural formula is: The B-6 structural formula is: The PAA solution was diluted to a solid content of 3.9% to obtain an orientation agent solution with a viscosity of 7.12 cp, which was then filtered through a 0.22-micron filter membrane.

[0100] Example 10 Under nitrogen protection, 7.90 g (12.72 mmol) of photoresponsive diamine A-7, 6.70 g (16.46 mmol) of oriented functional monomer B-2, 5.17 g (26.94 mmol) of 1,2-bis(4-aminophenoxy)ethane (C-4), and 3.59 g (18.71 mmol) of 4-aminobenzoic acid-4-aminophenyl ester (C-6) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added, and the mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Next, 2.00 g (52.42 mmol) of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (D-2) and 14.64 g (20.07 mmol) of [unspecified ingredient] were added to the solution. 1,2,3,4-Tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (D-3) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA solution with a viscosity of 468 cp.

[0101] The A-7 structural formula is: The PAA solution was diluted to a solid content of 3.2% to obtain an orientation agent solution with a viscosity of 7.54 cp, which was then filtered through a 0.22-micron filter membrane.

[0102] Example 11 Under nitrogen protection, 5.63 g (11.53 mmol) of photoresponsive diamine A-8, 8.16 g (19.22 mmol) of oriented functional monomer B-5, 3.71 g (13.82 mmol) of 1,4-bis(4-aminophenyl)piperazine (C-3), and 6.47 g (32.31 mmol) of 4,4'-diaminodiphenyl ether (C-5) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added, and the mixture was mechanically stirred at room temperature until the diamine monomers were fully dissolved. Finally, 7.75 g (36.88 mmol) of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (D-2) and 8.28 g (36.94 mmol) of other compounds were added to the solution. 1,2,4,5-cyclohexanetetracarboxylic dianhydride (D-4) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA solution with a viscosity of 404 cp.

[0103] The A-8 structural formula is: The PAA solution was diluted to a solid content of 3.8% to obtain an orientation agent solution with a viscosity of 7.98 cp, which was then filtered through a 0.22-micron filter membrane.

[0104] Comparative Example 1 Under nitrogen protection, 13.48 g (34.87 mmol) of oriented functional monomer B-1, 3.75 g (16.50 mmol) of 4,4'-diaminobenzoyl aniline (C-1), and 4.41 g (40.41 mmol) of 2,6-diaminopyridine (C-2) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Then, 12.96 g (66.09 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) and 4.99 g (23.75 mmol) of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (D-2) were added to the solution. The mixture was mechanically stirred at room temperature for 12 h to obtain a PAA solution with a viscosity of 422 cp.

[0105] The PAA solution was diluted to a solid content of 3.8% to obtain an orientation agent solution with a viscosity of 7.99 cp, which was then filtered through a 0.22-micron filter membrane.

[0106] Comparative Example 2 Under nitrogen protection, 12.82 g (31.38 mmol) of oriented functional monomer B-2, 4.64 g (20.42 mmol) of 4,4'-diaminobenzoyl aniline (C-1), and 7.16 g (26.68 mmol) of 2,6-diaminopyridine (C-2) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Then, 14.74 g (75.16 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (D-1) was added to the solution. The mixture was mechanically stirred at room temperature for 12 h to obtain a PAA solution with a viscosity of 322 cp.

[0107] The PAA solution was diluted to a solid content of 4% to obtain an orientation agent solution with a viscosity of 7.45 cp, which was then filtered through a 0.22-micron filter membrane.

[0108] Comparative Example 3 Under nitrogen protection, 12.28 g (26.64 mmol) of photoresponsive diamine A-2, 5.70 g (23.32 mmol) of 1,2-bis(4-aminophenoxy)ethane (C-4), and 4.98 g (24.87 mmol) of 4,4'-diaminodiphenyl ether (C-5) were added to a 250 mL three-necked round-bottom flask. Then, 160 g of N-methylpyrrolidone was added. The mixture was mechanically stirred at room temperature until the diamine monomer was fully dissolved. Next, 10.45 g (49.73 mmol) of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (D-2) and 6.59 g (16.13 mmol) of other compounds were added to the solution. 1,2,3,4-Tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (D-3) was reacted with mechanical stirring at room temperature for 12 h to obtain a PAA solution with a viscosity of 430 cp.

[0109] The PAA solution was diluted to a solid content of 3.8% to obtain an orientation agent solution with a viscosity of 7.89 cp, which was then filtered through a 0.22-micron filter membrane.

[0110] The filtered PAA alignment agent was applied to a cleaned ITO glass substrate using a spin coating method. The spin coating program was set to 500 rpm / 20 s initially, followed by 1300 rpm / 30 s. The substrate was then pre-baked on a hot plate at 90°C for 2 minutes to remove most of the solvent and form a transparent pre-cured film.

[0111] High-temperature imidization: The pre-baked substrate is transferred to a programmable temperature oven and cured in a nitrogen atmosphere by stepwise temperature increase: the temperature is increased to 230°C at a rate of 2°C / min and held for 30 minutes. This process completely dehydrates and cyclizes the polyamic acid to form the corresponding polyimide (PI) oriented film. After natural cooling to room temperature, the film thickness is approximately 80-120 nm.

[0112] Cell assembly: Two substrates coated with PI alignment film are aligned in an antiparallel manner (opposite photoalignment directions), and the cell thickness is controlled using plastic spacers with a diameter of 3.5μm. The edges are sealed with UV-curable adhesive to form an empty cell.

[0113] Crystal filling and sealing: Under vacuum conditions, nematic liquid crystal (with negative dielectric anisotropy Δε) is filled into an empty cell. After filling, the injection port is sealed with UV-curable adhesive to produce a standard test liquid crystal cell.

[0114] The following describes the evaluation method and evaluation results of the liquid crystal cell samples prepared in the embodiments and comparative examples.

[0115] [Reversible adjustment of pretilt angle] Objective: To directly verify whether the pretilt angle of the liquid crystal cell can be reversibly controlled by light stimulation, and to measure the adjustment range (Δθ) and reset accuracy.

[0116] Method: A liquid crystal cell was fabricated, and the initial pretilt angle θ0 was measured. The cell was then irradiated with an LED lamp with a wavelength of 420 nm and a light intensity of 10 mW / cm² for 30-90 seconds, and the pretilt angle θ1 after the change was measured. Next, the cell was irradiated with a reset LED lamp with a wavelength of 530 nm and a light intensity of 20 mW / cm² for 60-120 seconds, and the recovered pretilt angle θ2 was measured. Δθ = |θ1 - θ0| and Δθ' = |θ2 - θ0| were calculated. Durability could be tested through multiple cycles.

[0117] Evaluation: The Δθ value reflects the adjustment capability; Δθ ≥ 0.5° indicates adjustment capability. The Δθ' value reflects the reset accuracy and should be as small as possible (< 0.3°). A low Δθ decay rate after cycling indicates good durability.

[0118] Voltage holding rate Objective: To evaluate the insulation performance and charge retention ability of alignment films under an electric field, which are key indicators for predicting image persistence.

[0119] Method: At high temperature (50℃), a DC voltage of ±5V was applied to the liquid crystal cell and maintained. After disconnection, a high impedance meter was used to measure and calculate the percentage of the residual voltage to the initial voltage at 60ms.

[0120] Evaluation: The higher the percentage value, the better. Excellent PSVA alignment agents require a VHR > 95.0%. A decreasing value indicates high levels of ionic impurities or poor insulation.

[0121] [Heat Resistance and Reliability] Objective: To evaluate the physical and functional stability of alignment films after high-temperature processes or environments.

[0122] Method: The cured alignment film substrate was placed in a high-temperature environment (250℃) for 1 hour. After treatment, the appearance of the film was observed, and the liquid crystal cell was remade to test its core performance such as pretilt angle and VHR.

[0123] Assessment: The membrane should be free of cracks and peeling; the core performance (VHR, pretilt angle) should decrease very little before and after treatment, with VHR decreasing by <0.5% and pretilt angle Δθ <0.3° (difference in pretilt angle before and after high-temperature treatment).

[0124] Residual DC Voltage (RDC) Test Objective: To evaluate the charge trapping and accumulation characteristics of alignment films under an electric field. Excessive RDC is the main cause of image sticking.

[0125] Method: The "Voltage Retention Rate-Capacitance (VHR-C) Method" was used. At 50℃, a ±2V DC bias voltage was applied to the liquid crystal cell for 1 hour. Then, the AC measurement mode was quickly switched and the residual voltage decay curve across the liquid crystal cell was measured using a high impedance meter. The voltage value after 0.1 seconds was taken as RDC.

[0126] Evaluation: The lower the RDC value, the better. It is usually required to be below 100mV. Excellent orientation agents can be controlled below 50mV or even 30mV.

[0127] [Response Time Test] Objective: To evaluate the rate of change in the optical state of the liquid crystal cell when voltage is applied / removed, and during light adjustment.

[0128] method: a. Electrical response time: Using a photoelectric detection system, the time required for the transmittance of the liquid crystal cell to change from 10% to 90% (rise time) and from 90% to 10% (fall time) under a square wave driving voltage of 0V to 5V is measured.

[0129] b. Photoresponse time: Under a fixed voltage, using an adjustable 420nm LED light source, the time required for the pretilt angle change or the corresponding optical delay change to reach 90% of the stable value under real-time monitoring.

[0130] Evaluation: Record the electrical response time (τ_on / τ_off) and optical response time separately. The optical response time is typically in the order of seconds, while the electrical response time should be in the order of milliseconds (<15ms).

[0131] [Observation of Orientation Uniformity and Defects] Objective: To visually evaluate the uniformity of liquid crystal molecule alignment induced by the alignment agent and to check for point or line defects caused by poor alignment or impurities.

[0132] Method: The prepared liquid crystal cell was placed under a polarizing microscope and observed between orthogonal polarizers. An AC signal slightly below the saturation voltage was applied to slightly tilt the liquid crystal, thereby enhancing the contrast.

[0133] Evaluation: Observe the uniformity of light and dark across the entire display area (especially the edges and center). The alignment film should produce a uniform dark or bright field in the field of view, without obvious streaks (hooks), vortices, bright spots, or cloudy uneven areas.

[0134] Electro-optic property curve test Objective: To comprehensively characterize the relationship between the transmittance of a liquid crystal cell and the driving voltage, and to obtain key parameters such as threshold voltage and saturation voltage.

[0135] Method: Using a liquid crystal electro-optical characteristic testing system, under constant light source illumination, the driving voltage was gradually increased from 0V (in 0.1V increments), and the transmittance of the liquid crystal cell was measured simultaneously until the transmittance reached the maximum saturation value.

[0136] Evaluation: Plot voltage-transmittance curves. Analyze the threshold voltage (Vth, when transmittance reaches 10%) and saturation voltage (Vsat, when transmittance reaches 90%). The light modulation function of this invention may slightly alter the shape of the curves and the Vth value.

[0137] Long-term optical / thermal reliability cycling test Objective: To evaluate the durability and fatigue resistance of the light reversible modulation function, as well as the stability of the material under long-term stress.

[0138] method: a. Optical Cycling Reliability: The liquid crystal cell is subjected to repeated "adjustment-reset" optical cycles (60 seconds of UV irradiation → 60 seconds of visible light irradiation constitutes one cycle). After a certain number of cycles (e.g., 100, 500, 1000 times), its pretilt angle adjustment range Δθ, VHR, and RDC are tested again, and performance degradation is observed. b. High Temperature and Humidity Storage: The liquid crystal cell is stored in a high temperature and humidity environment (60℃ / 90%RH) for 500 hours. After being removed and allowed to return to room temperature, its electro-optical properties (VHR, RDC, pretilt angle) are tested and compared with those before storage.

[0139] Evaluation: Record the rate of change of key performance parameters with the number of cycles or storage time. Excellent examples should exhibit extremely low performance degradation (Δθ retention >90% after 1000 cycles, VHR decrease <3%).

[0140] [Evaluation Results] The evaluation results of the examples and comparative examples are shown in Table 1.

[0141] Table 1. Monomers used in the Examples and Comparative Examples, and evaluation results of the liquid crystal cell samples prepared therefrom. As shown in Table 1, the liquid crystal cell samples prepared in Examples 1-11 have advantages such as reversible adjustment of the pretilt angle and accurate reset, good insulation, fast response time, and uniform orientation. Their overall performance is better than that of Comparative Examples 1-3.

[0142] In summary, this invention introduces photo-induced reversible isomerism responsive units into the polyimide side chains. These units undergo reversible molecular conformational changes under specific wavelength light irradiation. This microscopic deformation is transferred to the material surface through chemically bonded flexible spacer groups, thereby directly and reversibly adjusting the anchoring effect between the interface and liquid crystal molecules, achieving effective control of the pretilt angle. Through this molecular design, the alignment layer is transformed from a passive, permanent "recording medium" into an active, responsive "intelligent interface." Consequently, display devices based on the alignment agent of this invention can have their pretilt angle non-destructively, reversibly, and repeatedly adjusted and rewritten during product use by applying a light source of specific wavelength and intensity. This endows a single display panel with dynamic and reconfigurable optical properties, enabling it to flexibly adapt to diverse application scenarios, thus completely overcoming the fundamental defect of existing technologies that cannot achieve dynamic functionality due to limitations in chemical principles.

[0143] 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, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A photoresponsive diamine monomer for use as an orientation agent, characterized in that, The photoresponsive diamine monomer has the structure shown in Formula 1 or Formula 2: Formula 1, Equation 2, in, R1 and R2 are each independently selected from one of -H, -NO2, -N(CH3)2, -CH3, -OCH3, -OCH2CH3, -OCH(CH3)2, -CH(CH3)2, and -C(CH3)3; R3 and R4 are each independently selected from a single bond or one of the structures shown in Equations 3 to 9: Formula 3, Equation 4, Equation 5, Formula 6, Equation 7, Formula 8, Formula 9, In Equations 3, 4, or 5, n is an integer greater than or equal to 2 and less than or equal to 10; in Equations 6 and 7, m is an integer greater than or equal to 2 and less than or equal to 6, and n is an integer greater than or equal to 0 and less than or equal to 6; and, when R3 is selected from one of the structures shown in Equations 3 to 7, R4 is a single bond or is selected from one of the structures shown in Equations 8 or 9, or, when R4 is selected from one of the structures shown in Equations 3 to 7, R3 is a single bond or is selected from one of the structures shown in Equations 8 or 9; R5 is selected from one of the structures shown in Equation 10, Equation 11, or Equation 12: Formula 10, Formula 11, Equation 12; R6 is selected from one of the structures shown in Equation 13 or Equation 14: Equation 13, Equation 14, In Equation 13 or Equation 14, n is an integer greater than or equal to 3 and less than or equal to 10.

2. A photoresponsive composition for an orientation agent, characterized in that, The photoresponsive composition comprises a diamine monomer and a dianhydride monomer, wherein the diamine monomer comprises at least one photoresponsive diamine monomer as described in claim 1 and at least one oriented diamine monomer; Preferably, the oriented diamine monomer has the structure shown in Formula 15 or Formula 16: Formula 15, Equation 16 in, R7 is selected from one of the structures shown in Equations 17, 18, 19, 20, and 21: Equation 17, Equation 18, Formula 19, Equation 20, Equation 21, In Equation 17, n is an integer greater than or equal to 0 and less than or equal to 10; in Equation 18 or Equation 20, m and n are each independently selected from integers greater than or equal to 0 and less than or equal to 6. R8 is selected from either a single bond or one of the structures shown in Equations 22, 23, and 24: Equation 22, Equation 23, Equation 24; R9 is selected from either a single bond or one of the structures shown in Equations 25, 26, and 27: Equation 25, Equation 26 Equation 27; R 10 Choose one of the structures shown in Equations 28 and 29: Equation 28, Equation 29, In Equation 28 or Equation 29, n is an integer greater than or equal to 3 and less than or equal to 10; Preferably, the molar ratio of the diamine monomer to the dianhydride monomer is 1:0.8~1, more preferably 1:0.9~0.98; Preferably, the diamine monomer further includes other diamine monomers that are different from the photoresponsive diamine monomer and the oriented diamine monomer; Preferably, the photoresponsive diamine monomer accounts for 5-40 mol% of all diamine monomers, more preferably 10-25 mol%. Preferably, the oriented diamine monomer accounts for 5-40 mol% of all diamine monomers, more preferably 10-25 mol%. Preferably, the photoresponsive composition further includes an organic solvent, and more preferably, the organic solvent includes at least one of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, dimethyl sulfoxide, and propylene glycol methyl ether acetate.

3. The photoresponsive composition according to claim 2, characterized in that, The photoresponsive composition must satisfy at least one of the following two conditions: (1) The dianhydride monomer includes at least one of the following dianhydrides: 、 、 、 、 、 、 、 、 、 、 、 。 (2) The other diamine monomers include at least one of the following diamines: 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 。 4. A polyamic acid solution, characterized in that, The polyamic acid solution is obtained by reacting the photoresponsive composition according to any one of claims 2-3; Preferably, the solid content of the polyamic acid solution is 10-30%, more preferably 15-25%; Preferably, the viscosity of the polyamic acid solution is 100-600 mPa·s, more preferably 200-500 mPa·s.

5. A method for preparing the polyamic acid solution according to claim 4, characterized in that, Including the following steps: (1) Under a nitrogen atmosphere, the diamine monomer is dissolved in an organic solvent to obtain solution 1; (2) The dianhydride monomer is added to solution 1, and the reaction is carried out to obtain a polyamic acid solution; Preferably, in step (2), the dianhydride monomer is added to solution 1 in batches; Preferably, in step (2), the reaction temperature is not higher than 40°C, more preferably 0-30°C, and even more preferably 10-25°C; Preferably, in step (2), the reaction time is 8-36 hours, more preferably 10-24 hours.

6. A polyamic acid orientation agent, characterized in that, The polyamic acid orientation agent is obtained by diluting and filtering the polyamic acid solution according to claim 4 or 5 with a diluent solution; Preferably, the diluent includes at least one of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol dimethyl ether, ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diacetone alcohol, and diisobutyl ketone. Preferably, the filter membrane used for filtration has a pore size of 0.1-1 micrometer, more preferably 0.1-0.5 micrometer; Preferably, the solid content of the polyamic acid orientation agent is 2.5-6%, more preferably 3%-5%; Preferably, the viscosity of the polyamic acid orientation agent is 6.5-9 mPa·s, more preferably 7.0-8.5 mPa·s.

7. A polyimide film, characterized in that, The polyimide film is obtained by coating and imidization reaction of the polyamic acid orientation agent as described in claim 6; Preferably, the thickness of the polyimide film is 80-120 nm; Preferably, the imidization reaction is carried out under a nitrogen atmosphere; Preferably, the temperature range of the imidization reaction is 200-250°C.

8. A display device, characterized in that, The display device comprises the polyimide film according to claim 7; Preferably, the pretilt angle of the display device is reversibly adjustable.

9. A method for adjusting the pretilt angle of a display device as described in claim 8, characterized in that, Including the following steps: (1) Applying ultraviolet light of a first wavelength and a first intensity to the display device to change the pretilt angle from a first state to a second state; (2) Apply ultraviolet light of a second wavelength and a second intensity to the display device obtained in step (1) to restore it to the first state or change it to the third state; Preferably, the first wavelength range is 360-420 nm, and the first intensity range is 5-20 mW / cm. 2 ; Preferably, the second wavelength range is 500-600 nm, and the second intensity range is 10-30 mW / cm. 2 .

10. A display module, characterized in that, The display module includes the display device as described in claim 8; Preferably, the display module includes a view-switching display module, a privacy-protecting display module, or a rewritable display module.

Images