Preparation method of PNLC film and application of PNLC film in automobile intelligent dimming awning

Abstract

The invention discloses a preparation method of a PNLC film and application of the PNLC film in an automobile intelligent dimming awning, and belongs to the technical field of liquid crystal materials for intelligent awning glass and preparation of the liquid crystal materials. The problems that an existing automobile intelligent dimming awning cannot meet the rapid dimming requirement and is poor in reliability and durability and the like are solved. A bifunctional liquid crystal monomer RM82 and a nematic liquid crystal E7 are compounded, acrylate end group polymerization of the RM82 is realized under the initiation of ultraviolet light, meanwhile, a biphenyl core structure and E7 can form a strong pi-pi conjugation effect, a phase separation energy barrier of the PNLC film is remarkably reduced, GQDs serve as a scattering enhancer, the PNLC film is endowed with a dynamic luminescence capability by utilizing the fluorescence characteristic of the GQDs, and the PNLC film has a good application prospect. The orientation of liquid crystal molecules is regulated and controlled through an electric field or temperature, the light scattering state is changed, switching of light transmitting, light scattering and light emitting is achieved, and the starry sky effect is simulated.

Description

Technical Field

[0001] This invention relates to a method for preparing a PNLC film and its application in an automotive smart dimming sunroof, belonging to the technical field of liquid crystal materials for smart sunroof glass and their preparation. Background Technology

[0002] Automotive sunroofs are high-tech features applied to car sunroofs, dynamically adjusting their light transmittance and haze to achieve functions such as sunshade, heat insulation, privacy protection, or ambiance creation. Starry sky roofs, on the other hand, simulate a starry night effect by using optical technology on the sunroof's inner lining. Both technologies rely on optical functional films as their core carrier. The color-changing film used in sunroofs is electronically controlled and dynamically adjustable, while the light guide film used in starry sky roofs utilizes photolithography and superconducting mapping combined with optoelectronic technology in the backlight module to achieve the effect. These two types of products occupy different market shares due to their varying application needs, and both face developmental bottlenecks due to their respective performance limitations: sunroof films offer limited color options, typically blue (electrochromic technology) and hazy white (polymer / liquid crystal technology), failing to meet user aesthetic preferences; starry sky films have poor heat insulation and cannot replace sunshades, limiting their application to nighttime scenarios. Therefore, providing a technology that can address both needs and expand into a wider application market has become a current research hotspot.

[0003] Currently, liquid crystal polymers are mostly prepared using a one-stage saturated polymerization method. The core of this technology is to expose a mixture of reactive mesocrystalline material, low molecular weight liquid crystal, and photoinitiator to ultraviolet light for a sufficient duration to complete polymerization. However, if images are required to be generated in this type of color-changing film, the electrode portion in the conductive substrate must be patterned and etched using laser technology beforehand, which increases both the complexity of the process and the cost. Summary of the Invention

[0004] In order to solve the above-mentioned problems existing in the current intelligent dimming sunroof of automobiles, the present invention provides a method for preparing a PNLC film and its application in intelligent dimming sunroof of automobiles.

[0005] This invention utilizes polymer network liquid crystal (PNLC) film as a color-changing light-transmitting carrier. A reverse-mode (transparent when not energized, atomized when energized) dimming film system is developed using a pre-alignment process. Customized patterns on the dimming film are fabricated using photomask UV curing technology, and then revealed through a thermal processing process. Furthermore, considering the low physical scattering efficiency caused by the PNLC film being thinner than the light guide film, graphene quantum doping is introduced to effectively improve the physical scattering efficiency of the PNLC film. Combined with an LED backlight module, multi-color dynamic displays can be achieved. In summary, the development of a high-value-added PNLC film with dual functions innovatively integrates dimming, heat insulation, and dynamic multi-color display effects, possessing potential applications such as automotive dimming canopies, dynamic starry sky canopies, and combinations thereof, demonstrating significant scientific and industrial value.

[0006] The technical solution of the present invention: One of the objectives of this invention is to provide a PNLC film comprising a base layer and a graphene quantum dot-doped PNLC film stacked between two base layers, wherein the base layer is composed of an ITO-PET substrate layer and a PI orientation layer coated on the ITO-PET substrate layer and pre-oriented.

[0007] Further specifying, the graphene quantum dot-doped PNLC film is obtained by laying a mixed solution of graphene quantum dot-doped PNLC obtained by mixing GQDs, RM82, E7 and HHMP, then obtaining a patterned pre-crosslinked graphene quantum dot-doped PNLC film by UV curing through a photomask template, and then annealing.

[0008] Further specifying, the unsaturated crosslinking degree of the patterned pre-crosslinked graphene quantum dot-doped PNLC film is 50-75%.

[0009] Further specifying, the pre-orientation treatment method for the PI orientation layer is: the polyimide layer coated on the ITO-PET substrate is obtained by friction orientation treatment using a friction machine.

[0010] The second objective of this invention is to provide a method for preparing the above-mentioned PNLC membrane, specifically including the following steps: (1) Mix RM82, E7 and HHMP and stir for 1 to 1.5 h in a water bath at 50 to 60 °C. Then add GQDs dispersion and continue stirring for 1.5 h in a water bath at 60 to 70 °C. Then degas the mixed solution under vacuum to obtain a graphene quantum dot-doped PNLC mixed solution. (2) Apply polyimide (PAA) adhesive to the ITO-PET substrate with a thickness of 0.5-2 μm and heat cure at 60-80℃ to obtain a polyimide (PI) layer. Use a friction machine to align the PI layer at a speed of 1000-2000 r / min to obtain a PI oriented layer on the ITO-PET substrate. Thus, a base layer consisting of the ITO-PET substrate and the pre-oriented PI oriented layer coated on the ITO-PET substrate is obtained. (3) At 40±1℃, the graphene quantum dot-doped PNLC mixed solution was uniformly coated on the PI orientation layer of the base layer, and a base layer was covered on it, ensuring that the PI orientation layer was in contact with the graphene quantum dot-doped PNLC mixed solution to obtain a wet film. (4) Under nitrogen protection, a photomask template with a predetermined pattern is placed on the surface of the wet film and placed in the UV curing zone for irradiation pre-curing treatment to obtain a patterned pre-crosslinked graphene quantum dot-doped PNLC film, which is then annealed to obtain a PNLC film.

[0011] Further specified, in (1), the mass ratio of RM82 to E7 is 1:8, the mass of GQDs is 0.1 to 0.5% of the total mass of RM82 and E7, and the mass of HHMP is 1 to 2% of the mass of RM82.

[0012] Further specified, the wet film thickness in (3) is 40~70μm.

[0013] Further specifying, in (4), the UV curing region consists of a 365nm LED array, and the irradiance for the irradiation curing treatment is 1-5mW / cm². 2 The exposure time is 2-4 minutes.

[0014] Further, in (4), the annealing temperature is 60~70℃ and the time is 1~2h.

[0015] The third objective of this invention is to provide an application of PNLC film, specifically for the preparation of intelligent dimming sunroofs for automobiles.

[0016] The fourth objective of this invention is to provide an intelligent dimming sunroof for automobiles, which includes an automobile sunroof glass substrate and the aforementioned PNLC film stacked on the glass substrate. The PNLC film is connected to the automobile circuit via an epitaxial electrode and a flexible wire in series with a photosensitive sensor.

[0017] The fifth objective of this invention is to provide an application of the above-mentioned PNLC film. The specific application method is as follows: the PET substrate layers on both sides of the PNLC film are cut off to expose the ITO electrode portion, and multiple solder points are made on the ITO electrode and connected to flexible wires. The electrode is then shaped and pressed to form an epitaxial electrode. The epitaxial electrode is connected to the automotive circuit through flexible wires. The graphene quantum dot-doped PNLC film is fixed to the underside of the automotive sunroof glass substrate by clips or OCA optical adhesive.

[0018] Beneficial effects: This invention involves mixing a mixture of ultraviolet-polymerizable liquid crystal monomer RM82, low molecular weight liquid crystal E7, and photoinitiator HHMP at a concentration of 1-5 mW / cm². 2 The first-stage polymerization was carried out under high-power ultraviolet irradiation for 2-4 minutes, resulting in a patterned pre-crosslinked graphene quantum dot-doped PNLC film. Under subsequent thermal or electrical induction, the residual active free radicals from the first-stage polymerization react with the unsaturated polymerized RM82 to undergo a second-stage polymerization reaction, forming an isotropic polymer network and thus achieving optical modulation. EPR testing revealed that the unsaturated crosslinking degree of the polymer network in the pre-crosslinked graphene quantum dot-doped PNLC film formed in the first-stage polymerization was 50%-75% within 2-4 minutes (unsaturated crosslinking degree = residual free radical concentration / total free radical concentration; free radicals refer to acrylate free radicals generated by RM82 under the action of the photoinitiator HHMP). This process effectively altered the structure and optical properties of the color-changing polymer network liquid crystal (PNLC). The PNLC film after the second-stage polymerization was in a scattering state, which could be triggered by electrical stimulation to achieve refractive index matching between the liquid crystal and the polymer, leading to a transparent state. Reversible optical modulation was successfully achieved, meeting the optical requirements of different scenarios. Furthermore, in the patterning process, this application employs a simple ultraviolet photomask technique. Compared to traditional laser etching and nanoimprint lithography, this technique offers significant advantages such as a simpler processing flow, lower unit cost, and more flexible pattern design. The specific process is as follows: During the first stage of ultraviolet irradiation, a photomask with a specific pattern blocks part of the ultraviolet light, while the patterned portion allows ultraviolet light to pass through. This causes the liquid crystal mixture in the patterned portion to undergo a first-stage unsaturated cross-linking. Then, through thermal or electrical induction of the liquid crystal into a disordered state, the pattern is formed on the film. Reversible color change is then achieved through electrical modulation. Compared to existing technologies, this application also has at least the following advantages: (1) In this application, the bifunctional liquid crystal monomer RM82 is combined with the nematic liquid crystal E7. The acrylate end group of RM82 is polymerized under ultraviolet light. At the same time, its biphenyl core structure can form a strong π-π conjugation with E7, which significantly reduces the phase separation energy barrier of PNLC film. Furthermore, by introducing GQDs as scattering enhancers, the fluorescence properties can be used to give PNLC film dynamic light emission ability. By controlling the crosslinking density of PNLC, the orientation of liquid crystal molecules can be controlled by electric field or temperature to change the light scattering state and realize the switching of "transmitting light-scattering light-emitting light" to simulate the starry sky effect.

[0019] (2) This invention utilizes GQDs as carbon nanomaterials (zero-dimensional nanoparticles with a size of less than 20 nm), which can be uniformly integrated into the PNLC system. This enables the direct integration design of graphene quantum dot-doped PNLC films with automotive sunroofs, eliminating the need for traditional discrete fiber optic structures. The sunroof is transparent when not powered, ensuring high light transmittance. Simultaneously, when powered, the sunroof exhibits fogging and reduced transparency, achieving active light emission and displaying a predetermined pattern. Compared to other traditional modified materials (TiO2 nanoparticles, azo dyes, etc.), GQDs have strong absorption capabilities for ultraviolet light, acting as a "built-in ultraviolet barrier" to prevent direct ultraviolet light irradiation of liquid crystal molecules and polymer substrates (such as polyimide alignment films and PET substrates), thus avoiding liquid crystal molecule degradation, substrate yellowing, and extending the sunroof's lifespan. Furthermore, the chemical inertness of GQDs prevents reactions with electrode materials (such as ITO), maintaining stable electrode conductivity. Furthermore, the introduction of GQDs improves the charge transport capability of PNLC films, significantly shortens the response time, and reduces the driving voltage. Traditional liquid crystal windows require a driving voltage of 30-40V or higher to achieve molecular orientation switching, while with the addition of GQDs, the driving voltage can be reduced to 5-15V, resulting in a 30%-50% reduction in power consumption over long-term use. Through patterned orientation processing and the fluorescence properties of GQDs, the graphene quantum dot-doped PNLC film is made transparent during the day, ensuring normal light transmission through the sunroof. At night, under a 15V, 100Hz AC drive, PNLC polymer scattering and GQD luminescence are achieved, allowing the predetermined pattern to change dynamically, enhancing the luxury and technological feel of the car interior. Moreover, due to the high thermal conductivity of GQDs and their strong interaction with the PNLC polymer network, the graphene quantum dot-doped PNLC film maintains stable liquid crystal orientation and electro-optical properties even at high temperatures (such as 60℃).

[0020] (3) By adjusting the addition ratio of photoinitiator HHMP, the present invention induces the formation of a PNLC structure with a three-dimensional interpenetrating network by ultraviolet exposure. At the same time, by adjusting the crosslinking density of PNLC, the orientation of liquid crystal molecules can be controlled by electric field or temperature to change the light scattering state and realize the switching of "transmitting light - scattering light - emitting light" to simulate the starry sky effect.

[0021] (3) The method for preparing graphene quantum dot-doped PNLC thin films provided by the present invention is simple, and the use of photomask process to produce patterned and roll-to-roll processes can meet the needs of large-area, high-efficiency and low-cost preparation of automotive intelligent dimming sunroofs, making it more suitable for industrial production. Attached Figure Description

[0022] Figure 1 SEM image of a graphene quantum dot-doped PNLC film; Figure 2 SEM image of a perovskite quantum dot-doped PNLC film; Figure 3 This is a schematic diagram illustrating the process of patterning a substrate using photomask technology. Figure 4 An optical photograph of the intelligent dimming canopy prepared in Example 1 under heating-cooling stimulation; Figure 5 An optical photograph of the intelligent dimming canopy prepared in Example 1 under electrical stimulation; Figure 6 This is a comparison of the transmittance curves of the PNLC membrane prepared in Example 1 before and after color change. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art may make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0027] Example 1: The process for preparing graphene quantum dot-doped PNLC thin films in this embodiment is as follows: I. Material Preparation and Pretreatment (1) Dispersion of nanoscale graphene quantum dots (GQDs) Weigh an appropriate amount of GQDs (zero-dimensional nanoparticles with a size of less than 20 nm) and add them to N,N- In dimethylformamide (DMF), the mass fraction of graphene was controlled at 0.5%. The mixture was ultrasonically dispersed at 400 W for 1.5 h to form a stable GQDs dispersion.

[0028] (2) Preparation of liquid crystal-prepolymer Weigh the liquid crystal monomer RM82, nematic liquid crystal E7, and HHMP (photoinitiator) separately, with the mass ratio of RM82, E7, and HHMP being 1:8:0.01. Place the three components in a clean glass container and stir them in a constant temperature water bath at 60°C for 1 hour to form a uniform dispersion.

[0029] (3) Solution preparation The GQDs dispersion obtained in (1) was slowly added to the RM82 / E7 / HHMP mixed solution obtained in (2) (the amount of GQDs added was 0.5% of the total mass of RM82 and E7). The mixture was stirred for 1.5 h at 300 r / min in a 60℃ water bath to ensure that the GQDs were uniformly dispersed in the liquid crystal-prepolymer system. After stirring, the mixed solution was transferred to a vacuum drying oven and degassed for 1 h under a vacuum of 0.01 MPa to remove air bubbles and avoid affecting the film quality, thus obtaining the premixed RM82 / E7 / GQDs / HHMP mixed solution.

[0030] II. Preparation of PNLC membranes (1) Pretreatment of substrate First, the PET flexible transparent conductive film is ultrasonically cleaned with acetone, isopropanol and deionized water in sequence, dried with nitrogen, and then subjected to plasma treatment (50 W, 1 min) to remove contaminants and weaken the boundary layer.

[0031] (2) Orientation treatment A polyimide (PI) solution (WL398 / WL396 from Weilai Electronics, Korea, with a mass ratio of A to B of 2:1) was coated onto an ITO-PET substrate with a coating thickness of 2 μm. The solution was thermo-cured at 70°C, and the PI layer was then rubbed and oriented using a rubbery machine at a speed of 2000 r / min. This resulted in a PI-oriented layer on the ITO-PET substrate, forming a base layer consisting of the ITO-PET substrate and the pre-oriented PI layer coated on it.

[0032] (3) Coating Subsequently, at 40±1℃, a slit coating head (50μm gap, 1m / min speed) was used to uniformly coat the premixed RM82 / E7 / GQDs / HHMP mixed solution onto the PI orientation layer of the base layer, and a base layer was then placed on top of it, ensuring that the PI orientation layer was in contact with the graphene quantum dot-doped PNLC mixed solution, to obtain a wet film with a thickness of 70μm. The coating temperature was controlled at 40±1℃ to prevent the liquid crystal prepolymer from agglomerating.

[0033] (4) Photomask patterning and UV curing Photomask technology is used to pattern the substrate, forming electrode patterns (HIT, starry sky patterns). Specifically, under nitrogen protection, a photomask with the predetermined pattern (HIT) is placed on the surface of a wet film and then placed in a UV curing zone (365nm LED array, irradiance 5mW / cm²). 2 The irradiation curing process (with an exposure time of 3 minutes) yielded a patterned pre-crosslinked graphene quantum dot-doped PNLC film. Exposure to UV light under a photomask caused the photoinitiator HHMP to decompose and generate free radicals, initiating crosslinking of the RM82 prepolymer to form a polymer network that fixes the orientation of the liquid crystal molecules.

[0034] (5) Packaging and post-processing The patterned pre-crosslinked graphene quantum dot-doped PNLC film obtained after UV curing was annealed in a constant temperature drying oven at 70℃ for 2 hours to eliminate internal stress and improve the film's performance and stability. The annealed film was then wound up for later use. It can be subsequently cut to the required size to obtain the final PNLC film.

[0035] III. Preparation of Intelligent Dimming Canopy (1) Electrode arrangement The PNLC film is cut according to usage requirements, and then the PET substrate layers on both sides of the PNLC film are trimmed off, exposing the exposed portion to which ITO electrodes are attached. Multiple solder joints are fabricated on the ITO electrodes and connected to flexible wires. The electrodes are then shaped and pressed together to form epitaxial electrodes, which are connected to the circuit via flexible wires. A transformer is designed based on the actual voltage of the vehicle to adjust the transmittance and pattern of the PNLC film, simulating a starry sky effect. A photosensitive sensor with a response speed in the μs range is connected in series. Its control logic is: circuit disconnection under low irradiance conditions, and circuit opening after reaching a strong light threshold, ensuring the PNLC film is in transparent mode during the day (e.g., ...). Figure 6 As shown, when no power is applied and the voltage is 0V, the PNLC film is in transparent mode. At night, after power is applied, the PNLC film exhibits fogging and reduced transparency, thus achieving active light emission (e.g., ...). Figure 6 As shown, the transparency of the PNLC film decreases when a voltage of 15V is applied.

[0036] IV. Thermal Stimulation Control of Intelligent Dimming Canopy The aforementioned intelligent dimming canopy underwent a heating-cooling cycle test at 25℃-40℃-25℃, such as... Figure 4 As shown, when the temperature rises to 40°C, the patterned portions of the PNLC film become distinguishable from the transparent background. This is because the LC mixture has entered an isotropic state at 40°C, while the PNLC regions retain their liquid crystal state. Therefore, the patterned portions of the graphene quantum dot-doped PNLC film become distinguishable from the transparent background. Furthermore, this display mode persists when the temperature is cooled back to 25°C, indicating that the process is irreversible.

[0037] V. Electrical Stimulation Control of Intelligent Dimming Canopy Apply a 15V, 100Hz AC current to the upper and lower surfaces of the aforementioned intelligent dimming canopy, maintain for 15 seconds, then remove the voltage. Figure 5 As shown in (a), after applying voltage, the PNLC film transitions from a transparent state to a milky white, strongly scattering state. After removing the voltage, the "HIT" pattern in the PNLC film becomes visible and remains. (b) shows the dynamic scattering state inside the PNLC film observed under cross-polarization. As can be seen from Figure (b), when the PNLC film is at 45° to any of the cross-polarizers, the sample is initially dark. After applying voltage, it exhibits a dynamic scattering state. After removing the electric field, the "HIT" pattern part becomes randomly oriented, while the rest returns to the dark state. This strongly verifies that the disordered arrangement of LMWLC leads to the reorientation and contact of unsaturated polymerized RM82 chains, forming a new isotropic network due to secondary polymerization.

[0038] Example 2 The difference between this embodiment and embodiment 1 is that: 2. In the preparation process of PNLC film, the exposure time of irradiation curing treatment (4) is 2 min, and the remaining process steps and parameter settings are the same as in embodiment 1.

[0039] Example 3 The difference between this embodiment and embodiment 1 is that: 2. In the preparation process of PNLC film, the exposure time of irradiation curing treatment (4) is 4 min, and the other process steps and parameter settings are the same as in embodiment 1.

[0040] Comparative Example 1 The difference between this embodiment and embodiment 1 is that: 2. In the preparation process of PNLC film, the exposure time of the irradiation curing treatment in (4) is 5 min, and the other process steps and parameter settings are the same as in embodiment 1.

[0041] Comparative Example 2 The difference between this embodiment and embodiment 1 is that: 2. In the preparation process of PNLC film, the exposure time of irradiation curing treatment (4) is 7 min, and the other process steps and parameter settings are the same as in embodiment 1.

[0042] Comparative Example 3 The difference between this embodiment and embodiment 1 is that: 2. In the preparation process of PNLC film, the exposure time of the irradiation curing treatment in (4) is 0 min, and the other process steps and parameter settings are the same as in embodiment 1.

[0043] The degree of polymerization of the patterned pre-crosslinked graphene quantum dot-doped PNLC films prepared in Examples 1-3 and Comparative Examples 1-3 was characterized by EPR test spectra of the RM82 radicals generated by the patterned pre-crosslinked graphene quantum dot-doped PNLC films. The calculation results are shown in Table 1 below.

[0044] Table 1

[0045] The remaining molar concentration in the table refers to the remaining molar concentration of acrylate free radicals generated by RM82.

[0046] As shown in Table 1 above, the unsaturated crosslinking degree of the patterned pre-crosslinked graphene quantum dot-doped PNLC films prepared in Examples 1-3 with different UV exposure times ranged from 50% to 75%. Comparative Example 4: (1) Weigh the liquid crystal monomer RM82, nematic liquid crystal E7 and HHMP (photoinitiator) respectively, wherein the mass ratio of RM82, E7 and HHMP is 1:8:0.01. Place the three in a clean glass container and stir and mix in a constant temperature water bath at 60°C for 1 hour to form a uniform dispersion.

[0047] At 40±1℃, a premixed RM82 / E7 / GQDs / HHMP solution was uniformly coated onto a glass substrate using a slit coating head (50μm gap, 1m / min speed), and then placed in a UV curing zone (365nm LED array, irradiance 5mW / cm²). 2 The graphene quantum dot-doped PNLC film was obtained by irradiation curing treatment (exposure time 3 min). SEM images of the film surface are shown below. Figure 1 As shown.

[0048] (2) Perovskite quantum dot material was used to replace GQDs, and the remaining process steps and parameter settings were the same as in (1) to prepare a perovskite quantum dot-doped PNLC film. The SEM image of the film surface is shown below. Figure 2 As shown.

[0049] contrast Figure 1 and Figure 2 It is known that graphene quantum dot materials have better dispersibility than perovskite quantum dot materials.

[0050] The above description is only a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A PNLC membrane, characterized in that, The film includes a base layer and a graphene quantum dot-doped PNLC film stacked between the two base layers. The base layer consists of an ITO-PET substrate and a PI orientation layer coated on the ITO-PET substrate and pre-oriented. The graphene quantum dot-doped PNLC film is obtained by coating a mixed solution of graphene quantum dot-doped PNLC obtained by mixing GQDs, RM82, E7 and HHMP, then curing it under ultraviolet light through a photomask to obtain a patterned pre-crosslinked graphene quantum dot-doped PNLC film, and then annealing it. The unsaturated degree and crosslinking degree of the patterned pre-crosslinked graphene quantum dot-doped PNLC film are 50-75%. The pre-orientation treatment method for the PI orientation layer is as follows: the polyimide layer coated on the ITO-PET substrate is obtained by friction orientation treatment using a friction machine.

2. A method for preparing the PNLC membrane according to claim 1, characterized in that, include: (1) Mix RM82, E7 and HHMP and stir for 1 to 1.5 h in a water bath at 50 to 60 °C. Then add GQDs dispersion and continue stirring for 1.5 h in a water bath at 60 to 70 °C. Then degas the mixed solution under vacuum to obtain a graphene quantum dot-doped PNLC mixed solution. (2) Coat a 0.5-2μm polyimide adhesive onto an ITO-PET substrate and heat-cur it at 60-80℃ to obtain a polyimide layer. Then, use a friction machine to perform a friction orientation treatment on the cured polyimide layer to obtain a PI orientation layer on the ITO-PET substrate. Thus, a base layer consisting of an ITO-PET substrate and a pre-oriented PI orientation layer coated on the ITO-PET substrate is obtained. (3) At 40±1℃, the graphene quantum dot-doped PNLC mixed solution was uniformly coated on the PI orientation layer of the base layer, and a base layer was covered on it, ensuring that the PI orientation layer was in contact with the graphene quantum dot-doped PNLC mixed solution to obtain a wet film. (4) Under nitrogen protection, a photomask template with a predetermined pattern is placed on the surface of the wet film and placed in the UV curing zone for irradiation pre-curing treatment to obtain a patterned pre-crosslinked graphene quantum dot-doped PNLC film, which is then annealed to obtain a PNLC film.

3. The preparation method according to claim 2, characterized in that, (1) The mass ratio of RM82 to E7 is 1:8, the mass of GQDs is 0.1~0.5% of the total mass of RM82 and E7, and the mass of HHMP is 1~2% of the mass of RM82.

4. The preparation method according to claim 2, characterized in that, (3) The thickness of the wet film is 40~70μm.

5. The preparation method according to claim 2, characterized in that, (4) The UV curing zone consists of a 365nm LED array, and the irradiance for the irradiation curing process is 1-5mW / cm². 2 The exposure time is 2-4 minutes.

6. The preparation method according to claim 2, characterized in that, (4) The annealing temperature is 60~70℃ and the time is 1~2h.

7. An application of the PNLC membrane according to claim 1, characterized in that, For the fabrication of intelligent dimming sunroofs for automobiles.

8. A smart dimming sunroof for automobiles, characterized in that, The intelligent dimming sunroof for automobiles includes an automobile sunroof glass substrate and a PNLC film as described in claim 1, which is stacked on the glass substrate. The PNLC film is connected to the automobile circuit via an epitaxial electrode and a flexible wire in series with a photosensitive sensor.

9. A method for preparing an intelligent dimming sunroof for automobiles as described in claim 8, characterized in that, The PET substrate layers on both sides of the PNLC film are cut off to expose the ITO electrode portion. Multiple solder joints are made on the ITO electrode and connected to flexible wires. The electrode is shaped and pressed to form an epitaxial electrode. The epitaxial electrode is connected to the automotive circuit through a photosensitive sensor connected in series with the flexible wire. The PNLC film is fixed to the underside of the automotive sunroof glass substrate by clips or OCA optical adhesive.

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